Pressure Controller for Air Leak Testing｜Stable Starting Pressure in Automotive Parts

Pressure Controller for Air Leak Testing

Demand for high airtightness is growing for automotive components such as battery packs and inverters. For the enclosures of these components, air leak testing (airtightness testing) using the pressure change method is widely used as a means of verifying airtightness performance.

The MC300 is used as a pressure controller that generates the "starting pressure (air-filling pressure)" for this air leak testing with both stability and repeatability. It can be applied across a wide range of inspection processes for mass-produced components such as inverters and battery cases—from individual evaluations in the development stage to shipping inspections on mass-production lines.

Challenges in Automotive Parts Air Leak Testing

With the expanding adoption of EVs, quality requirements for waterproof and dustproof performance and safety are growing for automotive components related to batteries and electrical systems. Related standards have also been established, such as IP ratings (IEC 60529), which define enclosure protection levels, and JIS Z 2332, which specifies leak testing using the pressure change method. To meet the requirements of automotive manufacturers, component manufacturers are required to establish inspection systems compliant with these standards.

High Airtightness Required for Enclosures

Battery packs and inverters are components whose performance and safety are affected by the intrusion of water and dust. To ensure stable airtightness performance as mass-produced products, an inspection process that verifies airtightness on every product is essential.

Errors Caused by Variation in Starting Pressure

The pressure change method evaluates the amount of leakage based on the pressure change after pressurizing or depressurizing to a specified starting pressure. Since variation in the starting pressure directly affects measurement results, filling air at a consistent pressure each time is essential for ensuring test repeatability.

Repeatability Requirements in Mass-Production Inspection

Shipping inspections require many products to be measured repeatedly under consistent conditions. If the starting pressure varies between individual units, the accuracy of evaluating individual differences decreases, which can also affect the reliability of inspection results.

Solution with the MC300 Pressure Controller

Pressurization at a Stable Starting Pressure

The MC300 is a pressure controller capable of pressurizing to the set starting pressure with high repeatability in air leak testing using the pressure change method. With an output relative accuracy of ±0.04% and a 12-month accuracy guarantee period, it smoothly reaches the setpoint with low overshoot. Because the pressure during air filling can be stabilized for every test, even in shipping inspections that continuously measure large numbers of products, test results can be obtained with errors caused by variation in starting pressure suppressed.

Needle Valve Design That Suppresses Overpressure

The MC300's pressure control section employs a needle-valve servo mechanism. A motor-driven needle moves continuously to smoothly adjust the airflow, performing fine control without outputting excessive pressure even near the setpoint. This design enables both high-speed pressurization with a response time of less than 5 seconds and low overshoot. It stably delivers the "fast, yet non-overshooting pressurization" required as the starting pressure for air leak testing.

Silicon Resonant Sensor Supporting High Accuracy

The MC300 is equipped with a silicon resonant sensor developed in-house by Yokogawa. Based on the principle that the resonant frequency changes when pressure is applied to a vibrator formed on a silicon wafer, the differential method using two vibrators cancels out the effects of external environments such as ambient temperature. With high sensitivity, resolution, and excellent long-term stability, it accurately monitors the output pressure and supports the reliability of feedback control. The output accuracy is maintained throughout the 12-month accuracy guarantee period.

Improved Inspection Accuracy with the MT300

In situations requiring a more precise testing environment, adding the MT300 Precision Pressure Monitor to the MC300 enables high-accuracy pressure monitoring near the DUT (Device Under Test). The MC300 stably supplies the starting pressure while the MT300 records the applied pressure, allowing the construction of a high-accuracy inspection environment—from detailed evaluations in the development stage to mass-production shipping inspections.

Expected Benefits of Using the MC300

By using the MC300, the following benefits can be expected in automotive parts air leak testing.

Improved Repeatability of Air Leak Testing

Stable pressurization that suppresses variation in starting pressure makes it possible to maintain consistent measurement conditions for each product. Even when continuously measuring many products on a mass-production line, errors caused by inconsistent conditions can be reduced, leading to more reliable test results.

Smoother Component Development

With accurate and highly repeatable measurement results, judgments regarding enclosure airtightness can be made quickly at each phase, from design to mass production. This is expected to facilitate smoother development of components requiring high airtightness performance, such as inverters and battery cases.

Stable Operation in Mass-Production Inspection

The combination of high-speed pressurization with a response time of less than 5 seconds and low overshoot enables stable measurement of large numbers of products while maintaining the inspection tact time on shipping inspection lines. It also supports automated testing using communication commands. This is expected to contribute to balancing productivity and quality in mass-production inspection processes.

Long-Term Stable Operation and Maintainability

The needle-valve design adopted by the MC300 does not involve rapid valve opening and closing, resulting in minimal component wear and stable operation over long periods. Since the output accuracy is also maintained within the 12-month accuracy guarantee period, the MC300 is also expected to contribute to reducing lifecycle costs when integrated into production lines.