Is This Transmission an Answer?

Have you actually built a model or prototype? Excuse me, but I'm skeptical when someone's first post is touting the latest, greatest, cure-all widget.

A continuously variable transmission is a device with continuously (non-stepwise) variable ratios. Such devices typically operate within a range of ratios (for example, from 1:1 to 3:1, not unlike the ratio spread found in a four-speed automotive gearbox). Unlike a standard transmission, a CVT can operate at any ratio between the extremes: 1:2.15, 1: 2.155, 1:2.16 etc etc. The power in and power out must be the same (except for unavoidable losses due to friction, which cause heating of the gerabox).

However, you wrote. "P-CVT does not directly provide a variable speed ratio. It varies the driving torque." This makes your device sound like a slip clutch, which can vary torque without varying speed of either input or output, creating a great deal of waste heat in the process.

Is there an animation that shows the device working? It is unclear from the description what the function of the "activator" is. From the function schematic, it appears only to change the phase angle between the input shaft and the gear 31. Do you have a working prototype?

For the purpose of demonstration and description, a prototype with just two gear pairs 41 and 42 might be useful.

Are you intending to say that your device allows output torque to change without changing output speed? That is a different function than a transmission (gearbox) usually provides.

My first observation is that I thought I was looking at a patent. Still do.

Patents are not written in a descriptive way that is easy for engineers to understand. They are written in lawyerspeak. So that "someone well schooled in the art" could understand them.

I think that you have designed an oil pump, that you think can function as a power transmission device, also.

Take K_Fry's suggestion and build a few gears. Don't forget the lubricant in your demo model. You'll turn the oil into foam.

Cool if it works.....

Unfortunately it will never be able to compete with even the most basic variable displacement pump/motor type hydrostatic drive system in terms of mechanical simplicity, size, power to weight ratio, efficiency, longevity, durability, or manufacturing cost.

May this transmission be an answer?

Nope more of a question.

A question of efficiency

A question of efficacy

A question of reliability

A question of whether it can deal with serious horsepower (more than 50bhp)

A question of is there enough money available to be thrown at its development without a possibility of ROI.

Hmm many questions to answer...

It may be the greatest set of "Continouos Variable Transmission" device. One thing is sure, that it is impossible to grasp it from the description provided.

Until, and unless a working prototype is provided with data, the rest of the presentation is meaningless. Have a good day.

I tried follow the explanations but are not clear enough to me specially pictures need more contrast.

Here the answer, but what's the question?

Duc Quang, what do you think this might be the answer to?

Can you give an example of where this transmission might fill an unoccupied application niche or improve on existing methods?

Following up on the above:

Start with the schematic drawing without the hydraulic cylinders, which appear to do nothing at the basic description level. Call shaft 1 the input shaft. Call shaft 2 the output shaft. Show the direction of rotation and speeds of each gear and carrier.

Because carrier 6 is fixed, the gears attached to carrier 7 (and disc 11 and the output shaft) must jump from one gear 42 to the next. A prototype that shows this occurring smoothly might be a good place to start (even if from just one gear to the next).

But in any event, this appears to be a single speed planetary gearbox, if you can get the gear jumping to work.

Isn't this something like a freewheel / overrunning clutch ala Reynolds, Formsprag etc., ? (Pardon my ignorance if not... i am an electrical engineer)

No. The things that look like smooth rollers are actually toothed gears. Freewheeling clutches transmit torque via friction between smooth surfaces.

(As it happens, most CVT transmissions do this as well, with either steel belts running on smooth steel pulleys or steel discs running on steel torus shapes. Special oils are used that allow for a combination of good traction and lubrication.) (The need for toothed [positive] drive, kind of the holy grail of CVT's, is largely imaginary. A typical production CVT has no more friction losses than a standard transmission. The old days of slipping belts are gone. Even the dry belt CVT's used in motor scooters are surprisingly efficient.)

More rambling:

Many people think of standard automatic transmissions (with the torque converter locked) and double clutch transmissions (a la Porsche 8 speed, etc) as being "positive" drive. This is not really true. Both make use of Formsprag style freewheeling clutches.

Formsprag clutches and V-belts both make use of positive feedback: the higher the load, the more firmly the friction elements engage.

Perhaps even more obviously: any standard transmission car uses friction drive: the clutch.

Hi K Fry

The operation of P-CVT is completely different from all prior mechanical CVTs. The V-Belt, Toroidal CVT vary the speed ratio by varying the effective radii. P-CVT does not directly vary the speed ratio; it varies the driving torque through the pressure control unit and the switching valve. P-CVT operates in a similar way as the Hybrid Synergy Drives (HSD), also called Electric Control CVT.

The heart of a HSD is a Power Split Device (PSD), a planetary gear set (PGS) having three driving members: the sun gear connects to a generator/motor, the carrier (arm) connects to the engine and the ring gear connects to a motor and the differential. The PGS provides any speed ratio between the engine and the differential (from zero to infinity, same direction or opposite direction). To transfer power from the engine to the differential, the generator/motor function as a generator, transforming dynamic power to electric power supplied to the motor. As the generator/motor function as a generator, it cause a resistance on the sun gear. At the planetary gear set, the resistance on the sun gear results in a resistance on the carrier that connects to the engine and a driving torque on the ring gear, connecting to the differential. The strengths of the resistance applied on the engine and the driving torque on the differential rely on how strong the resistance on the sun gear that is controlled through a power control unit. HSD does not directly vary the speed ratio; it varies the driving torque to get desired speed ratio.

The Reactor of P-CVT is a mechanism including two PSDs or planetary gear sets coupled together. The simple embodiment in the following figure may help in explain the operation of P-CVT. Please note that a working P-CVT is much complex.

The first PGS comprises three driving members: the first member is the sun gear mounted freely on the input shaft that connects to the engine, the second member are the planet gears that are supported on a carrier (arm) that is the third member of the first PGS. The carrier connects to the output shaft. The sun gear of the second PGS is keyed to the input shaft. The planet gears are also supported on the carrier of the first PGS. Each planet gear of the second PGS connects to each planet gear of the first PGS.

In case the gear ratio between the sun gear and the planet gear of the first PGS is equal to the gear ratio between the sun gear and the planet gear of the second PGS, at any speed ratio between the input and output shafts, the sun gear of the first PGS and the input shaft always rotate at the same speed. This means when the sun gear of the first PGS and the input shaft are connected, the two drive shafts can rotate at any speed ratio.

On the left view, the double-acting hydraulic cylinders connect the sun gear of the first PGS to the input shaft through ab arm. When the input shaft rotates, the double-acting hydraulic cylinders and the sun gear of the first PGS rotate as well. When hydraulic pressure applies on the hydraulic cylinders, the hydraulic cylinders try to turn the sun gear of the first PGS on the input shaft. Since the sun gear of the first PGS and the input shaft always rotate at the same speed, the hydraulic cylinder cannot turn the sun gear of the first PGS on the input shaft, they perform two equal and opposite torques: one applying on the sun gear of the first PGS and the other one on the input shaft. The strength and directions of the torques can be controlled through the pressure control unit and the switching valve.

As a toque applied on the sun gear of the first PGS, it causes the toques applied on the planet gears of the first PGS and another torque applied on the carrier connecting to the output shaft. Since the planet gears of the second PGS connect to the planet gears of the first PGS, the torques applied on the planet gears of the first PGS transfer to the planet gears of the second PGS. As the torques from the planet gears of the first PGS transfer to the planet gears of the second PGS, they result a torque applied on the sun gear of the second PGS and another torque applied on the carrier in opposite direction to the torque formed by the first PGS. Since the sun gear of the second PGS is keyed to shaft 1, the torque on the sun gear of the second PGS transfers to the input shaft, against the torque performed by the hydraulic cylinders.

On a HSD, at the PSD, the engine power flows into two directions: one to the differential, the other one to the generator. At the generator, the power is transferred to electric form then sent to the motor where it is transformed back to dynamic.

The difference between a P-CVT and a HSD is: while the HSD uses the electric devices to transfer power from a member to another member of a PSD and to control the driving torque, the P-CVT uses second PGS transfer power from a member of the first PGS back to the input shaft and uses a hydrostatic module to control the driving torque.

The embodiment as shown on the above figure is just used to provide the ideas on how a P-CVT create and control the driving torque. As mentioned, as the torques from the planet gears of the first PGS transfer to the planet gears of the second PGS, they result a torque applied on the sun gear of the second PGS and another torque applied on the carrier in opposite direction to the torque formed by the first PGS. Since the first and second PDSs have the same gear ratio, the strength of the torques performed by the second PGS is equal to the one performed by the first PGS. As a result, the driving torque is zero. To have a driving torque on the output shaft, the pitch diameter of the planet gear on the first PGS must be different to the pitch diameter of the planet gear on the second PGS i.e. the gear ratio of the first PGS must be different to the gear ratio of the second PGS. In this case, the whole system will turn around the center axis at the same speed. The simple embodiment like that cannot produce the driving torque or allow the speed ratio to be varied.

It is known that when the speed ratio between two drive shafts changes, the torque ratio between the torques applied on the shafts also changes.

A Reactor able to product the driving torque, allow the two drive shafts can rotate at any speed ratio and able to vary the torque ratio proportionally to the speed ratio would be quite complex.

A mechanism able to vary a torque ratio without varying a pitch diameter or an effective radius is something "out of laws" hard to accept. I need time to find a way to explain more clearly how it works. Thank for your interesting and comments.

As far as I can interpret, I don't think it will function as intended -- if at all.

P-CVT does not directly vary the speed ratio; it varies the driving torque through the pressure control unit and the switching valve.

As drawn, with hydraulic cylinders, this cannot happen. The cylinders only vary phase angle between the input shaft and the gear 31. This does nothing to change the torque output other than in the case where the input shaft it clamped and stationary. To apply a continuous torque to a rotating element, you need a motor. You have not explained, in any plausible way, how driving torque changes in response to the change in phase angle. Are there numerous pieces involved not shown in the engineering drawing?

P-CVT operates in a similar way as the Hybrid Synergy Drives (HSD), also called Electric Control CVT.

The HSD is not an electric control CVT. It is a power split device with three devices that supply power: an engine and two motors. The Prius acceleration is leisurely (as compared to its total power vs weight) because full power cannot be applied throughout the whole acceleration envelope. In a real CVT, full power can be applied continuously, while vehicle speed changes.
If you use this simulator of the HSD you can see that at 20 mph you cannot set the device to give high rpm on both motors and the engine, which is a condition for supplying high power to the wheels. In a CVT (or conventional 6-speed transmission, to an only slightly lesser extent) the engine's full power (as well as very high torque multiplication) is available at 20 mph.

To supply continuous power, a hydraulic cylinder must oscillate. As you have described your device, the hydraulic cylinder takes a position to change torque output (by some unexplained means) and then stays there. So in a given configuration, the cylinder could be replaced by a solid link. The cylinders, as drawn, only change phase angle between the input shaft and gear 31.

The source code for the HSD simulator is available. Perhaps you could use that code to help you build a simulator than explains the operation of your device.

You have not answered the question: Do you have a working model of your device?

It may be worth watching this video. Gizmag gushed about the device, but later realized that the device does not work as claimed; it too is a power split device (functioning in the same way as a differential).

Your new functional drawing does not show that the device would work as a CVT. It also suggests this question: If the device can be modeled as a pair of planetary gearsets, why not build it that way, which (especially for a prototype) would be easier, faster and far cheaper? You could find a couple planetary gearsets from a car's transmission for almost nothing, and could have your device ready for demonstration in a week or two.

When you have built your prototype, we'd love to see it operate.

My, my, this just gets curiouser and curiouser.

"When you have built your prototype, we'd love to see it operate."

Me, too.

Roger, roger.