Method for Estimation of Time at Temperature Histogram of Vehicle Interior Parts Exposed to Meteorological Environments around the World (Third Report) 2021-01-0296

In order to help guarantee the durability and reliability of vehicle interior parts, it is necessary to use time at temperature histogram data for the parts when they are exposed to actual meteorological environments as criteria for judgment. In order to do so, it would be necessary to conduct actual vehicle exposure tests in the regions throughout the world in which the vehicles will be sold, which is unrealistic. The research discussed in this paper proposes a method of estimating the time at temperature histogram for vehicle interior parts when exposure tests are conducted at locations throughout the world using vehicle-specific constants obtained from actual vehicle exposure tests conducted in a single location and publicly available annual meteorological data.

Using the same vehicle, exposure tests were conducted sequentially in three locations: Yomitan Village in Okinawa Prefecture (2016); a Honda parking lot in Haga, Tochigi Prefecture (2017); and a vacant lot belonging to a partner company in Takasu, Hokkaido Prefecture (2018). An analysis performed using hourly temperature measurement data and meteorological data found that air temperature is the basic temperature for the interior parts, and increases in their temperature above the air temperature were proportional to the total solar radiation or the amount of radiant heat from the instrument panel. It was also found that the degree of change in the temperatures of interior parts in relation to the amount of radiant heat, in other words the constants of proportionality, were constants specific to the vehicle used in the exposure test and not dependent on the location of the exposure test, or the season or weather in which it was conducted. It was possible to express the temperatures of the interior parts by means of these vehicle-specific constants and a linear model of the variables of air temperature and total solar radiation. Calculated values accorded well with measured values. Using this model, it has become possible to calculate time at temperature histogram data for vehicle interior parts when exposure tests are conducted at locations throughout the world.