Our Stories 03 Development of temperature sensors

Story 03A new sensor beyond core technology that enjoys top market share.
NGK SPARK PLUG CO., LTD. has developed "temperature sensors for turbochargers" that are very resistant to harsh conditions.

Exhaust gas temperature sensors play an important role in the running of cars.
This device measures the appropriate temperature range to protect the heart of engine from high temperature and to run engine efficiently in order to improve fuel efficiency and reduce CO2 emission.
Exhaust gas temperature sensors are necessary for turbochargers of diesel engine that has become smaller and lighter in considering the environment. However it is extremely difficult to create exhaust gas temperature sensors that satisfy durability to temperature change and vibration, and measurement accuracy.
NGK SPARK PLUG CO., LTD. has promoted technological innovations as the world's top brand in sensor technology and developed temperature sensors for turbochargers, which was technically challenging.
Here, let us see how they could overcome the "wall" that was an insurmountable difficulty with conventional technology─

Oya:Joined the company for 8 years. In charge of development and design of temperature sensors. His primary responsibility is to develop elements.

Nishi:In charge of development, process design and cost reduction through total adjustment.

Mishima:Has extensive experience in Quality Assurance Department. Currently in charge of sensor testing.

Morita:A sales engineer who is the point of contact for customers.

Development of new sensors for turbochargers, where traditional methods did not work the same way.

Technological innovations can be achieved when people take a leap of faith with great courage─

Exhaust gas temperature sensors for automobiles have evolved along with exhaust gas regulations.
We have developed various temperature sensors to meet demands including purpose, required performance and temperature range measurements, which may vary from time to time.

It's been 40 years since the first temperature sensor was developed. We started the development from detecting exhaust gas temperatures to prevent overheating of catalysts.
Next exhaust gas temperature sensors were required to maximize the capacity of engines and cleaning systems that keep the temperature ranges where sensors could fulfill their functions.
Technology has been carried forward into the turbocharger temperature sensors that increase the power outputs of diesel engines, and the technology has continued to evolve.
The knowledge we have gained through the development of various temperature sensors is utilized in exhaust gas oxygen sensors, wide range oxygen sensors, and NOx sensors. Sensor technology is a relatively new field in our long company history, but has grown to be our core technology. It also has a lineup of sensors that can respond to a broad range of different demands.

Here is a question of why development of temperature sensors for turbochargers is difficult for us, with having a history of technological developments.

"Because downsizing of engines has been a trend, pressure and temperature of small engines have to be high to maintain conventional power levels. Under harsh environmental conditions, highly precise designs are needed to detect gases emitted from engines." designer Oya stated.
During combustion, the temperature around engines becomes very high in a moment, but when the engine stops, it becomes immediately low. This temperature change is significant. In addition to this "thermal shock," sensors must resist engine vibrations. Of course, they have to ensure the durability up to 300,000 km drive.
The conventional design concept is inapplicable in this situation. Accordingly, the team had faced difficulties since the start of the development.

"Element," a key to development of precise sensor, and ideas exceeding conventional concepts.

On the other hand, members had confidence they had obtained through their ceramic and sensor manufacturing.

Members were confident because they had an advantage of in-house development of "elements," which is the basic foundation of measuring temperatures.
Elements can be created from various potential materials, so there are several hundreds of combinations to create them. Furthermore, they are fragile and as small as grains of rice, and require high technology. It is easy to create a large element but if an element is small, the product will be more valuable with light weight and low cost without the consequences of engine vibrations. There is no exaggeration to say that engineers started this project "to create the smallest sensors in the world."

Oya decided to locate a sensor in the upstream side to protect the engine, not in the downstream side to protect the catalyst. He thought that, if they locate a sensor in the downstream side, the conventional products was good enough to satisfy the requirements. The engineers thought "when we develop a new sensor, we want to take on the challenge of upstream side development that is more difficult," and this decision triggered the team's passion. After the examinations of durability and improvement of precision, Oya designed an element with a different approach from the conventional method.

However, this was contradicted by other members.
Given the rule of thumb so far, some thought that "it was impossible."
Oya struggled with the old concepts and results which were established by the 40 years of history of temperature sensors.

When they cannot obtain the data they expected, they become either optimistic or pessimistic. When they are optimistic, they have the inspiration of "what they have to do next." But when they are pessimistic, they become disappointed and the development is stagnated. When considering the whole sensor development, sharing the last form image makes project easier. But when they prioritize the development of elements, this would be a factor with a negative restriction.

The development and production of extremely small parts that should resist harsh environmental conditions. The best design of overall structure that can maximize its ability. Ono struggled to coordinate the design of element with other total aspects.

In this situation, it was the younger members' encouragement that helped him.
By consulting other people, they selected materials and re-examined element structure size and process method, and then steadily developed the element structure that can resist harsh environmental conditions.

The strength only NGK SPARK PLUG CO., LTD. has is the best "test environment" that is similar to the actual drive. It should help them to take on the challenge.

They selected the most promising elements but needed more time to turn the product into a prototype. They had to evaluate the durability of sensors by operating test equipment for many hours, instead of using actual engines.
This "test environment" is our strength along with "in-house element production." It cannot be accomplished in a day, and it was an achievement of senior engineers' effort.

When we stepped into the new field, development of sensor for turbocharger─,
Senior engineers were bewildered when faced with a huge barrier, "Why does this element break this way?"
They had no idea in what environment the sensor broke and what happened with vehicles. Then they focused on reproducing the situation in their test environment with collecting information from their clients, automobile manufacturers. They worked hard to collect and manage data every day and to obtain immediate feedback from clients repeatedly. As a result, they deepened their understanding of "what clients knew and pointed out at their field test" and "what the cause of the problem was," and they realized how to reproduce environments similar to actual driving tests.

Even after the test environment has been established, they attempted to obtain data of the failed products, aiming to find factors that shows "the reason why the product failed." Also in this turbocharger temperature sensor development, they repeated these tests over and over in order to narrow down products to the most promising one.

The shared passion for sensors supported the members' work.
"I love cars. I explore new horizons in order to contribute to automobile industries with products that I was involved in creating," Mishima said.
Morita, who was in charge of negotiations, said, "I feel excited every time I see the vehicles that I was involved in manufacturing running on the roads with our sensors in their hoods."

Future proposals beyond our No.1 core technology.

For engineers, temperature sensors for turbochargers are entirely different from conventional sensors in terms of their engine environment and technology. This will create a new challenge for them to open a new field. Furthermore, contributing to the sensor industry will be the result of their efforts as well as their adaptability to new core technologies.

Recently, the team has achieved mass production for the new sensor.
"It may be an exaggeration but I believe that we could create a product that opens a new chapter in the history of temperature sensors. We have managed to overcome almost all technical issues and will start manufacturing of the product that will be a breakthrough product. I am very happy about that," Mishima stated with confidence.

Nishi, who is in charge of the production process comments on the new stage.
"They designed quality products that they can guarantee to sell. However, it is inefficient to introduce totally new production facilities in order to manufacture new products. We have a great responsibility to utilize the existing production facilities instead."

Oya says, "I am confident that this is our new No.1 product, but I don't want to stop working on our self-improvement at this stage. I wish to continue to take on new challenges in order to maintain our company's position on the top of sensor industry at all times."

Since engines of the future will undergo a significant evolution, engineers will continue to explore new possibilities.
The team members are encouraged to think that "It is necessary to create products that will meet future technology trends."
They also believe that "They have developed products that meet current clients' needs so far, but they still have to successfully anticipate clients' future needs in advance and respond with appropriate products." The project members' inspirational goals are beyond our expectations as they'll always bravely take on new challenges.