Section 3. Research and Development of Basic Technology
Item 6. Rubber Product Research and Development
Manufacture of rubber products at the Kariya Plant
In May 1936, upon completion of the car assembly plant within the Automotive Department of Toyoda Automatic Loom Works, the rubber product manufacturing process was moved from the brake test plant to a 660 square meter lot at the new facility, becoming part of the chassis assembly section. The engineers who had been engaged in developing rubber products also began to work in the new location, while retaining their affiliation with the research laboratory of the Steelmaking Department. In addition, four new staff members with experience in rubber product manufacturing were hired, and the lineup of rubber part manufacturing equipment was further enhanced.1
Subsequently, the company embarked on the development of hoses for hydraulic brakes, and prototypes were produced, using Wagner hydraulic hoses as reference. The rubber for the inner tube and external cover was natural rubber of the highest quality, while the pressure-resisting layer employed long-staple Egyptian cotton thread woven into a tubular shape. The resulting prototypes proved strong enough for practical use. After the trial manufacture of rubber parts for brakes had shown some success, the program was expanded to include other rubber parts such as extruded parts, anti-vibration rubber mounts, fan belts etc.
From 1938 onwards, the use of imported parts increasingly gave way to domestically produced parts, and brake master cylinders from Nippon Air Brake Co., Ltd. were adopted. Also in 1938, hydraulic brake oil manufactured by Tokyo Rikagaku Kogyo Sho, and refractory brake oil from Nippon Brake Oil Shokai were designated as genuine Toyota accessories.
In November 1938, with the completion of the Koromo Plant, the engineers working on rubber parts development who had previously been affiliated with the chemical laboratory in the research laboratory of the Steelmaking Department of Toyoda Automatic Loom Works were transferred to Toyota Motor Corporation and were now affiliated with the rubber works at the Kariya Plant. According to the employee roster of 1939, the name of the rubber works was "Kariya Representative Office Research Department".
Another significant development in 1938 was the so-called "tire drought" In January of that year, the Japanese government restricted the import of crude rubber in order to address an imbalance in international payments. As a consequence, shipments of finished tires continued to fall drastically, until numbers were down to about 10 percent of regular figures by October. In November, the supply of tires stopped altogether.
Given this situation, focus shifted to the production of domestically sourced tires, engineers specializing in this area were hired, and preparations for production facilities were made. Between 1940 and 1941, some 500 tires were produced at the rubber works of the Kariya Plant in a series of trials.2
However, because the supply of crude rubber was threatened by the war situation, the Ministry of Commerce and Industry did not grant the required permissions, and trial production of tires ceased. The production equipment was subsequently moved to the Iho Rubber Plant located at Tianjin in China. This plant, financed at 1.6 million yen and dedicated to the manufacture of rubber products, had been founded through equal participation by four parties, namely Yokohama Rubber Co., Ltd., Chuji Idebuchi, Toyobo Co., Ltd., and Toyoda Boshoku Sho. In August 1942, the equipment transferred from Toyota Motor Corporation was installed at the plant located at street No. 15 in the "Italian concession" of the city of Tianjin, and used for the production of aircraft tires.3
At the rubber works in Japan, the "tire drought" of 1938 also prompted a reconsideration of the material used for steering wheels. Researchers began exploring the possibility of using cellulose acetate resin instead of the hard rubber that so far had been the norm. Cellulose acetate was produced by the Shonaigawa Rayon Company as a source material for rayon yarn and therefore represented a promising choice. However, although the R&D efforts culminated in the successful production of a prototype steering wheel using thermoplastic cellulose acetate resin, the raw material for cellulose acetate, namely pulp, had also become very scarce in the meantime, and the switch in steering wheel material therefore did not develop beyond the trial stage.
In February 1942, when trial production of rubber parts was finally concluded and full-scale production began, the Kariya Representative Office Research Department was renamed to Kariya Plant Rubber Section.
The Rubber Department of the Kariya Plant was integrated into Kokka Kogyo in May 1943, following the governmental directive for the integration of industry. Production equipment was moved to the former Shokufu Plant, which started to operate as the Kokka Kogyo Nagoya Plant. The former name of the Shokufu Plant was Toyoda Shokufu Kikui Plant, originally managed by Sasuke Toyoda. As it specialized in woven fabric and had no spinning department, it was not included in the merger of five Toyoda and Toyo Menka-related spinning and weaving companies, and had become in effect an idling plant. 4