Toyota’s popular Camry now comes in a hybrid version thanks to innovations and investment in the assembly line at Georgetown, Kentucky. AMS looks at how the manufacturing process has been modified to accommodate the new, cleaner model.

Toyota celebrated the production launch of the Camry Hybrid at its Georgetown, Kentucky facility (TMMK) last October – the first hybrid vehicle from the Japanese manufacturer to be produced in North America.

The addition of hybrid production represents a $10m investment at TMMK, which will build approximately 48,000 Camry Hybrid vehicles per year. TMMK was established in 1986 and is Toyota’s largest plant in North America. The facility employs approximately 7,000 team members and currently builds the Camry, Avalon and Solara.

It has the capacity to build 500,000 vehicles annually. Since its inception, TMMK has built about 6.7 million vehicles and the plant’s current investment is $5.4 billion.

“We are proud, excited and honoured to be Toyota’s first plant in North America to build a hybrid vehicle,” says Steve St. Angelo, President of TMMK. “It’s a great tribute to the tremendous ability and skill level of all of our team members who have been building the Camry.”

The Toyota Hybrid Synergy Drive System consists of gas and electric power sources that are complementary and produce a combined 187hp. This system varies power between gas and electric, or both, as needed. The first half of the system consists of a 2.4-litre 4-cylinder engine, assembled at TMMK’s powertrain plant. The Atkinson-cycle engine generates 147hp and is coupled to a continuously variable transmission.

The second half of the Hybrid Synergy Drive equation consists of a small, high torque electric motor that produces 141hp, an ultra-small inverter with a specially designed compact battery and a transaxle to provide the economy and seamless performance hybrid drivers seek.

In 1997, Toyota became a pioneer in the industry by launching the Prius, a mass-production hybrid vehicle with outstanding environmental performance. Toyota has positioned hybrid systems as a key technology for the 21st century and is taking measures to promote the widespread use of hybrid vehicles.

Smooth transition

The man charged with integrating the production of the Camry Hybrid at Georgetown is David Cox, General Manager of Manufacturing Engineering, who has the role of Chief Engineer for the plant in Georgetown.

Cox has been at Toyota for 18 years and was General Manager of the Central Engineering Group for several years, responsible for stamping and body weld and paint shop before moving to his current role three years ago. His main responsibilities are new model introduction, major projects and plant support for the Baha Mexico facility, and the joint venture with Subaru.

Although the exterior body profiles are similar between the traditional Camry and its hybrid offspring there are several key differences – the battery, electric motor and inverter from the hybrid drive, the transaxle to deliver this combined power and the regenerative braking system, all of which have some effect on the manufacturing process.

“There are a little over 350 unique components for the hybrid but a lot of those are just cosmetic changes as far as assembly is concerned. For example, the instrument cluster has a different look, but it is still replacing a traditional instrument cluster, so it is not a totally new item; it is just a different feature for the hybrid,” Cox explains. “Of course, the main hybrid component is the transaxle, a combination of electrical motor generator and transaxle, but it bolts to the engine very similarly to a standard transaxle.”

Designed with vision

Cox explains that the Camry was designed from its early days with a hybrid version in mind. That philosophy has meant that the changes required for the underbody were very minor. “It had the unique rear floorpan and centre floor, which is right below and behind the rear seat,” he says. “That is strictly for the main battery mounting. There are a lot of additional studs and pass throughs for the high voltage wire harness and things like that. Basic shapes are similar; there are just additional holes.

“On the hybrid, the main drive battery is under the rear seat so you lose a little bit of trunk space, but not significantly.

And, because of where it is, you cannot get a reclining rear seat in the hybrid version due to the space issue. Except for that, the interior of the car is exactly the same. There may be a little difference in fabric, a little difference in instrument clusters that look slightly different, but as far as space and comfort go, it is exactly the same as the standard.”

One of the things that enables the hybrid car to achieve excellent fuel economy also causes some engineering problems – namely the fact that the petrol engine does not run all the time. This means that the air conditioning system cannot be on a traditional compressor type system because it would not be functioning all of the time. For the hybrid an electric HVAC system (heating, ventilation and air conditioning) has been installed. Also, because the engine does not run all of the time, the fuel tank does not have a vapour return like a normal fuel system does. At peaks it has a high pressure and about a third of the $10m investment went into solving that engineering dilemma. “We had to do a new fuel tank line because the fuel tank steel is much thicker and has a plumbing that is a little more complicated,” says Cox. “When you pull up to refuel at a petrol station, you flick the lever to open the fuel door. Hopefully by the time you are back there it will be open, but it doesn’t immediately open. It actually evacuates the system of all the vapour and then the fuel door electrically opens. That is part of the requirement to meet the regulations and that is the captive passive vapour collection system helps meet that regulation. Again, a lot of that is just due to the fact the engine doesn’t run all of the time.”

Minor changes

Rather surprisingly the body shop escapes almost unaltered at Georgetown with the arrival of the Camry hybrid. The bodywork features a host of additional studs for the battery, extra holes to punch for the wiring harness and slightly different bracketing for the engine compartment to accommodate the inverter, but in the words of Cox it is all “minor”.

The latest version of the hybrid is a lot higher voltage than other Toyota hybrids: it is over 600 volts. Because of that, the components are a lot smaller and the inverter actually sits in the same location that the normal vehicle battery would sit.

So in the engine compartment, again other than the wire harness complexity and the regenerative braking systems, the physical changes to the engine compartment from the body shop side are fairly minor.

When it comes to welding there are some unique settings on the hem weld caused by the thicker material and because the material is thicker, the checking system for confirming the weld is a little more difficult, but it is basically the same process.

Simplified assembly

When you get into the assembly shop, of course, there are more severe implications with the major component being the high voltage battery that is installed in the rear.

The normal gasoline battery that would usually be in the engine compartment is actually in the trunk with the main battery. There is also a high voltage line that runs from the battery to the inverter and then you have all of the regenerative braking wiring that you don’t have in a normal vehicle.

So how have Georgetown adapted and incorporated this additional complexity into the assembly hall without harming hard won recent gains in productivity? Key to the ability to assimilate the additional model is the process simplification that has been an ongoing project with TMMK.

“We have been going through a process simplification activity for a couple of years in Georgetown,” Cox explains. “That has a lot to do with part sequencing and kitting that provides the on-line team member with the part directly in sequence. So the concept is not only to reduce and compress the line side links but also decreases the number of decisions that the team member has to make for any particular model coming back.

“We don’t have to have all these pallets of parts down the line, and this allows us to increase the process density, so instead of having to choose between 15 or 16 sun visors that you might have, that next sun visor for the next car is provided to him. So, the worker doesn’t have to make the selection decision, and it is provided in a small spot rather than having a case of all the different types.

“So through that activity we were able to compress the assembly line and we actually had quite a bit of the unused assembly line linked prior to this model.”

Bypass processes

The hybrid goes down the same mixed product line and, at the moment, approximately one in every eight vehicles is a hybrid. “Because of the additional space on the line we had to rebalance and move some things,” says Cox. “We also installed three bypass processes – one for main battery install, one for the inverter and all its connections, and one for the high voltage wire harness. The concept of a bypass process means that all the other cars pass right through it, there is no activity and nothing goes on the normal Camry in that process. In the case of the volume that we are running right now, that process is three to four stations long.

“The operators that, for example, are installing the inverter will start at the beginning of process one and work continuously on that vehicle through those four processes so they stay with the car. Normally, a team member would only work in a single pitch process and work that on every single vehicle, but in the bypass processes they stay with one vehicle through all the three or four stations. Then, when they are done, they walk back to the beginning for the next hybrid.

“Again, we only had to do three of those for those really unique long time installation type processes for the hybrid, which is fairly small and a minor impact on the assembly line.”

Somewhere in the region of three quarters of the processes have some sort of an impact on hybrids. Aside from the three major exceptions, however, these are simply a matter of selecting a different component.

There is one other additional off-line process at Georgetown, a pre-prep on the main battery. The battery comes in as a base unit and on site a fan blower for the venting is installed as well as some of the vent ducting. After that the battery is sequenced like any other part, and is simply placed in the car and bolted down.

Toyota team

Safety is always an important concern so the sheer weight of the battery and inverter necessitated the use of ‘lift assist’ lifting arms to install them. One nice story that Cox retells is the interaction between team members from Georgetown and their counterparts in Japan. “TMMK’s team members were in Japan during the initial design trials for the Japan hybrid and their original concept for battery installation was the same as the Prius, which is a hatchback so it is a slightly different vehicle,” he says. “They traditionally installed the battery through the back door and it causes an odd ergonomic issue to be able to do that in a sedan. So with our team member’s input and through doing some trials over there, we were the ones that came up with the concept of doing some pre-assembly on the battery and putting it straight in the luggage through the trunk.

It saves a lot of assembly in the vehicle, that concept changed the way Japan was planning to install it.”

The high voltage system itself was another area for safety concerns. As a completed vehicle the system is very safe – there are disconnects for the high voltage for maintenance purposes and the Toyota dealers that are doing maintenance have to know the proper procedure, but it is a very closed system.

“We did have to do some special safety training for dealing with the live components as we are assembling them, only certifying certain members to do repairs,” Cox says.

“We have highlighted high voltage-only zones in the repair bays, so that only certified people… can work on the vehicle.

Initially it was a safety issue, but really it is a quality issue too, as the technology is very different. So the certification of a repair person is probably where we spent most of our additional training time.

Increasing hybrid ratios

At first glance it would appear that this by-pass process would limit the ratio of hybrids that can be produced at Georgetown but, as Cox explains, that is not the case.

“Actually, we could probably have any infinite change,” he says. “We are not really the bottleneck. The battery availability will be the limiting factor on what we could build.

“As we are set up now, one in four or five would be the max without any process alignment, but even before we had to redistribute the line we could put in an additional person and have two running through that cycle on every other one.

So it is not going to be a major investment for us to go up in volume if at some point we decide to do that. Our fuel tank process has some limitations, of course, and the stud deck and body weld would need some kaizen improvements. We probably do have some flexibility to go up in volume if we ever decide to do that.”

Product levelling

As with any multi-model line, product levelling is an important consideration, but no more so for the hybrid than other models. “We try to keep the hybrids levelled out, but we try not to run the same model back to back as well,” Cox says.

“For example, at Plant One we have Avalon and Camry production where the Avalon content is a little different and could be more on a particular process. It may be a very full process and if you have an Avalon come through you could handle it within the 53-second take time that we are running.

But if you have two back to back, the potential of you getting behind is greater, so we try not to have the same model back to back. Thus, levelling is very important to us to maximise what those team members are doing every cycle [in order to avoid] having them standing around between a high work content model.”

According to Cox only about ten additional team members being recruited to work on the new model. This is good news because, if early sales figures are any indication, the volume could rapidly grow from the initial 50,000.