Antonov gears up for China - and EVs

  • 30-Dec-2010 01:24 EST
Antonov12-10 TX6 rendered.jpg

Antonov's TX6 twin-shaft transmission uses a combination of planetary and parallel axis gearsets, wet clutches, and no torque converter.

The aspirations of car buyers in emerging nations are presenting OEMs with commercial opportunities and technology challenges in almost equal measure. What the rest of the world — particularly the U.S., Europe, and Japan — has today, those nations want tomorrow. And China is in the vanguard.

For the majority of Chinese car buyers the vehicles they are purchasing now or in the near future will be their first. Buyers therefore have little or no basis for comparison of products and the technology they incorporate. Features are another matter, however. Most buyers will be aware of what is the norm in terms of equipment in America and Europe, and they will expect the same.

Consider the automatic transmission. Approximately 20% of cars currently sold in China are equipped with automatics, but by 2017 that figure is forecast to reverse, with automatics taking 80% of new vehicle sales. Further complicating demand is the Chinese market's growing awareness of the benefits of dual-clutch transmissions (DCT) as well as 7- and 8-speed automatics.  

Meeting such needs in moderately priced cars isn't easy, which is why transmission specialist Antonov has focused on the design and development of an all-new 6-speed automatic suitable for small to medium vehicles in the 150-180 N·m (111-133 lb·ft) engine torque range. But the company also is looking to the future. It is separately developing a 3-speed transmission for electric vehicles (EVs), which could also find applications in both developing and developed markets.

Veteran transmission engineer Simon Roberts is Antonov's Managing Director. He is fully aware of the shortcomings of automated manual transmission (AMT) technology, the cost of  DCTs, and the cost, packaging challenges, and comparative inefficiency of most torque converter (TC) automatics. He said there is a clear need for a transmission that can be positioned between the incumbent types for use in emerging markets.

Antonov's solution is the two-shaft TX6, aimed primarily at the Chinese market. Initial planned production volume is 200,000 units per annum.

The new 6-speed was developed in the U.K. and aimed at fwd applications. It's unrelated to an earlier transmission Antonov developed for MG Rover. It will be built by Chongqing EFA Transmission Co., a 50/50 joint venture between Antonov and its Chinese manufacturing partner, Chongqing Landai Industry Co.

The TX6's first application is the Lifan 620 sedan, powered by an 85-kW (114-hp), 145-Nm (107-lb·ft) 1.6-L engine. The car is expected to be priced around €7000. Start of production is planned for early 2012, in a new plant in Chongqing.

“The gearbox is similar to a conventional auto transmission, with planetary gearsets and transfer gearsets, but its major asset is that we have replaced the torque converter with wet multiplate clutches,” said Roberts. He explained the design offers a number of benefits to vehicle engineers. Its 325-mm (12.8-in) overall length compares well with a typical sector average of 380-420 mm (15-16.5 in), although length may vary according to engine damper requirements.

Total weight of the complete unit is 78 kg (172 lb).

The TX6's design also provides significant efficiency benefits, Roberts claimed, particularly in 1st, 2nd, and 3rd gears where the losses that could be expected with a torque converter system are entirely absent; 4th, 5th, and 6th are direct drive.

The TX6 has three pairs of transfer gears along the two parallel shafts. Each pair of gears is connected to an epicyclic unit. When open, each unit produces a ratio that is multiplied by the transfer ratio to give one gear; when the epicyclic unit is locked in direct drive, the ratio is that of the transfer gear. It obviates any losses from rotating gears.

Roberts said that unlike a Lepelletier design with its interdependency between gears, the Antonov system’s gears are independent, to give optimum efficiency across the rev range. Its architecture splits the mechanical hardware into two shafts instead of the more traditional single main shaft, enabling the gearbox length to be minimized to achieve a narrow installation between a vehicle’s front wheels.

Although the bill of materials is higher than in a TC transmission, the TX6's components are simple to manufacture. There is no need for complex multiplexing valves and integration. Installation in the vehicle is also simple, Roberts claimed.

Antonov’s costing is based on the transmission representing no more than 15% of the sticker price of the car. “We should be able to bring it into production for less than 1000 euros,” stated Roberts.

About 80% of the TX6's components will initially be manufactured in China, but that figure is expected to rise. Some critical components including the hydraulic block, which needs very accurate machining and clean assembly, are at present being manufactured in Germany. Roberts hopes that Chinese companies will eventually produce the blocks.

Magna is to supply production oil pumps for the transmission out of its Chinese facility. Cases, shafts, and gears are also being produced in China by Landai Industry Co.

“The TX6 is based on patented technology owned by Antonov,” Roberts noted. “Our philosophy is to go to China with a product that is of the lowest technical risk.”

A test program is continuing using VW Golf mules. First hardware phase was in 2008. The TX6 is expected to have a 150,000-km (93,200-mi) warranty and is being tested to 200,000 km (125,000 mi). 

All design, calibration, and development of the transmission is carried out at Antonov’s Warwick, U.K., headquarters in conjunction with Continental, which is supplying production control software.

Validation and sign-off by a Chinese manufacturer is currently typically around a third less time-consuming than would be the case at a company such as Mercedes-Benz, stated Roberts.

He deems DCT technology as being too advanced and costly for high-volume introduction into the Chinese market at present. AMT also is an unsatisfactory solution for applications there, he said. He believes that for at least the next decade, "the TX6 will sit neatly between TC and DCT.”

In the VW mule testing, the TX6 has proved capable of matching the fuel efficiency of a standard Golf 1.6 FSI equipped with an Aisin 6-speed automatic.

A 3-speed for EVs

While the TX6 is focusing Antonov’s development and production teams, a major R&D program concerns a 3-speed automatic gearbox for EVs. Antonov has built one for Jaguar in partnership with MIRA as part of the U.K. government’s Technology Strategy Board-funded "Limo-Green" project.

“We decided that for real efficiency an EV should have a 1st gear for launching and a 3rd for cruising, while the car would spend perhaps 95% of its running time in 2nd,” explained Roberts. “A 3-speed parallel-shaft gearbox with mainly commercial off-the-shelf (COTS) components maximizes motor efficiency. A single speed is not sufficient and a 2-speed provides a ratio step that feels like shifting from 1st to 4th in an IC car.

"It is virtually impossible to refine the shift and there is danger of gearbox damage,” he claimed. 

Roberts noted that in the early days of the auto industry, large engines and small transmissions were common. Now, he said, “we are seeing small engines (or electric motors) and large (with more ratios) transmissions. We will see a downsizing policy for electric motors just as we are seeing it for IC engines today, and we will see efficiency improved by the use of multispeed transmissions.

"We can easily add four more speeds to our EV transmission,” he asserted. 

For example, to use a 900-N·m (664-lb·ft) motor with a single-speed transmission would involve approximately "1200 A running round a vehicle” – an industrial level. But by using a three-speed transmission, 400 N·m (295 lb·ft) would be sufficient and bring the system down to 400-500 A, which he noted would be far more acceptable.

Roberts sees the 3-speed EV as suitable initially for larger vehicles in the U.S. and not city cars. But with the growing trend toward EV solutions, and with China always likely to want more and better technology, it could be that Antonov’s TX6 might eventually pave the way for the company’s multispeed EV transmission range, with applications in a wide span of vehicles.

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