However, even if this method was effective in theory, it was not easy to turn it into a marketable product. Above all the structure was completely different from that of conventional products, even other opposed type calipers. For example, since the force that was received by the entire caliper thus far is basically received only by the pin in this design, it was not clear at first how much strength the pin needed and what problems might occur.
A development team member who has been engaged solely in development of opposed type calipers since joining the company recalled that “the biggest challenge was pin design.”
“Because this was the world's first mechanism of its type, at first we were completely frustrated with the pin design. If we made the pin thicker to increase its strength, it would be much more difficult to secure sufficient pad area. By making prototypes and carrying out many verifications with actual machines, making full use of strength calculations and CAE (computer aided engineering) simulations, we finally achieved optimal balance of pad size, pin thickness and shape, holding method and so forth.”
The member spoke about the first time driving a test vehicle fitted with a prototype.
"I already knew the product would work from the CAE analyses, bench tests and so forth. Still, the moment I actually drove the vehicle myself, applied the brakes, and felt the response, I thought ‘Yes, it works!!’ That was thanks to our hard work to achieve smoother, quieter performance.”
However, to put the product on the market, it was vital to prevent aging and corrosion of the pins even in harsh environments. Brake calipers are exposed to heat, brake dust, mud, and water generated during braking, and there is also the possibility of wheel cleaner and brake fluid adhering to them. Of all car parts, the brakes are exposed to some of the harshest environments, and as parts crucial for safety, absolute reliability is required.
The developers compared various surface treatments and conducted component analyses for each process, while engaging with material and surface treatment manufacturers. Even as the mass-production stage approached, we were still reviewing the compatibility of the metal components and materials, and the processes, which were finally able to achieve an optimal surface treatment.
The completed 6-pot fixed calipers body is impressive. However, the highlight of the new product is the pin that penetrates the center and literally forms its “axis.”
As the project neared its completion and the product was nearing the mass production stage, one of the development team members who had worked so hard to make it commercially viable said:
"Adapting existing technologies involves a degree of trial and error, but this time we truly lacked past expertise and experience and were really doing something new. There were no clues how to proceed and we had to figure things out for ourselves. That was quite a challenge.”
For this new product, we were strongly committed to excellence in design and beauty, of the caliper. In a premium vehicle, the brake caliper is also part of the car design, and is one of the few functional parts that can be seen on the exterior.
At last, the world’s first vehicle to incorporate this aluminum 6-pot fixed caliper with a new mechanism was announced. It was the Lexus LC flagship coupe, released in March 2017.
For the Lexus LC 6-pot fixed caliper, we adopted a form that pursues functional beauty so as not to detract from the LC's elegant styling. Furthermore, by collaborating with the paint manufacturer from the paint selection stage, we were able to achieve a beautiful black paint finish that conveys a distinctly Japanese sense of beauty. One might say that the Lexus LC’s styling is complemented by the Japanese-made brake caliper, which can be seen in glimpses between the wheel spokes.
Another feature of this 6-pot fixed caliper is weight reduction realized through a monoblock structure, where the entire caliper is a single component, and a center bridge mechanism. As a result, weight was reduced by 10% compared to competing products.
The 6-pot fixed caliper created in this way has not only strong braking force, but also the smooth quietness and beauty suitable for a premium vehicle. A 6-pot fixed caliper of the same type was incorporated into the F SPORT, a sporty version of the Lexus LS flagship sedan, launched in autumn 2017.
What was this project like for the development team members?
"This was a tough project because we not only incorporated the latest technologies, but also worked to come up with entirely new ones. I am personally very pleased that we were able to see design and development through to the end and see the product adopted for mass-market flagship vehicles.”
"In the world of brakes, there is now demand for completely new technologies in the face of major changes such as automated driving and vehicle electrification. Being able to create a new mechanism unlike any in existence gave me a great deal of confidence going forward.”
For ADVICS, the adoption of this 6-pot fixed caliper for vehicles in the premium sports field is a big step forward. And for engineers involved in its development, the experience and confidence gained through this challenge will provide great impetus for the next new project.