Technology / product information

The parking rod is a safety-critical component responsible for holding an automatic transmission (AT) vehicle in a stationary condition. As a safety part, its heat treatment conditions and cam angle accuracy are strictly specified. These requirements are essential to ensure that the vehicle remains securely stopped in the P range and does not move due to malfunction or misoperation.

■ Safety Requirements for the Rod

The rod undergoes high-frequency induction hardening followed by tempering. During this process, precise control of surface hardness and case depth is required.
In addition, the hardening pattern must never penetrate into non-designated areas.

If the hardness is too low, wear progresses rapidly and the locking function may be lost. If the hardness is too high, the risk of brittle fracture increases. Proper management of the localized heat treatment pattern, which hardens only the specified areas, is the key to maintaining safety performance.

■ Safety Requirements for the Cam

The cam requires a higher hardness than the rod, achieved through carburizing heat treatment, as it functions as a sliding contact surface repeatedly engaging with the rod and therefore demands high wear resistance.

The case depth is strictly specified, and the cam angle is managed as a critical safety characteristic. Even a slight deviation in cam angle can alter engagement with the parking pawl, potentially causing a situation where the vehicle does not fully stop despite being in the P range.

■ Risks When Safety Characteristics Are Not Maintained

Abnormal wear

Part fracture

Deformation due to improper heat treatment

Cam angle deviation

If any of these occur, the vehicle may begin to move even when the transmission is in the P range, directly leading to serious accidents and personal injury.

■ Manufacturing Control to Ensure Safety Performance

To protect safety performance, the following controls are essential:

Process assurance of heat treatment conditions (temperature, case depth, hardness)

Visual inspection and hardness testing to verify hardening patterns

High-precision cam angle measurement and lot variation control

Measurement of deformation after heat treatment (straightness, dimensional changes)

In-process checks for abnormal wear

These activities are not merely quality control measures, but safety management practices aimed at accident prevention.

■ Strengths of Ohashi Tekko Vietnam

At Ohashi Tekko Vietnam, heat treatment of rods and cams, as well as cam angle control, are managed as special safety characteristics in accordance with standards established by the Japanese headquarters.

Through precise measurement of hardness, case depth, and cam angle, along with comprehensive evaluation of post–heat treatment deformation, the company ensures stable supply of high-reliability parking rods and related components that support vehicle safety.

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