The Ford Motor Co. has negotiated an agreement to acquire a 25 per cent interest in Toyo Kogyo Co., the Japanese manufacturer of the Mazda automobile.

The Hiroshima-based company announced the agreement yesterday and said the acquisition plan would be presented to its board of directors for approval next September.

If approved, the agreement would give Ford its first direct participation in an Asian automotive company. It is now the only major American automaker which does not have an affiliation of some sort with a Japanese manufacturer.

The two companies have negotiated off and on over 10 years but the first word that an agreement might be near came last May when both let it be known that a way was being sought for Ford to acquire a sizeable minority equity in Toyo Kogyo.

In making the announcement yesterday, Toyo Kogyo President Yoshiki Yamasaki minimized the American company's potential participation in his firm's operations.

He said Ford had agreed not to seek any management role in the companys operations and said that only a limited number of Ford personnel would join Toyo Kogyo's board of directors.

The two companies have had marketing tie-ups since 1972 and Ford now markets a small pick-up truck produced by Toyo Kogyo in the United States.

Officials of both companies in Tokyo emphasized this morning that the arrangement is only a capital tie-up and will not affect the market operations of either.

Toyo Kogyo now sells Mazda cars in the United States through its own network of dealers, and that arrangement will not change, a company spokesman said. There is no plan for the Japanese company to take over the marketing of Fords in Japan, he said.

The Toyo Kogyo spokesman also said it appeared likely the company's stockholders would approve the acquisition in September, paving the way for an agreement to be signed about the first of October.

Toyo Kogyo exported about 157,000 vehicles to the United States in 1978, including between 60,000 and 70,000 one-ton Courier trucks sold under the Ford brand.

The company is selling three Mazda models in the United States. The rotary-engine car, which has been produced here since 1931, is known as one which causes little air pollution. However, its success in America was limited during the first oil shortage in 1973 because of its high fuel consumption. Since then, the company has improved the model's fuel performance and now claims it gets 30 miles per gallon in city driving and 40 to 42 miles per gallon on the highway.

Ford markets its cars in Japan through its own distribution system, using independent dealers, and a Ford executive said there is no plan to enlist Toyo Kogyo in its Japanese sales campaigns.

No plans were announced for any exchange of technology between the two companies as a result of the agreement.

According to the agreement announced yesterday, Ford will acquire the 25 per cent equity share by permitting Toyo Kogyo to absorb all the assets of an old Ford subsidiary in Japan, Ford Industries Limited. That Yokohama-based firm was established in 1923 to assemble Ford Model-Ts but is now essentially a real estate management firm.

Another Ford subsidiary, Japan - Ford Motor Co., Ltd., based in Tokyo, currently imports Ford products and market them in Japan.

The exchange agreement will permit Ford to acquire the interest in Toyo Kogyo at considerably less expensive than if it had to buy the company's stock on the open market.

Japan's third largest auto manufacturer, Toyo Kogyo has a far smaller share of the Japanese market than either Toyota Motor Co., or Nissan Motor Co. Together, those two companies have nearly three fourths of the Japanese market.

According to reports published here recently, Toyo Kogyo may have been encouraged to make the tie-up with Ford by a large Japanese bank, Sumitomo, which overr the years has loaned substantial amounts of money to the manufacturer. CAPTION: Picture, The Toyo Kogyo "Ujina" automobile assembly plant. AP