Retractor Mechanism

Retractor Mechanism

Retractor mechanism
The electrically motorized reel system is an extension of the existing mechanical reel mechanism.
The electrically motorized reel system includes the following functions:
- Minimising belt slack (the seat belt lies as tightly as possible against the driver or passenger)
- Stabilization of the seating position in a critical driving situation or in the event of a possible accident (pretensioning of the seat belt to optimise the restraint system)

Brief component description
The following components are described:

EMALI or EMARE: Control unit for electrically motorized reel, left or right
The control unit is connected to the drive for the electrically motorized reels and vehicle network by mean of 2 plug connections.
Following of evaluation of various signals and messages, the control unit recognizes whether the belt has to be pretensioned. The control unit activates the drive for the electrically motorized reels directly.







Drive for electrically motorized reels, left and right
The drive for the electrically motorized reel on the left and right consists essentially of the following parts:
- Electric motor
- Electronic component
- Gear with clutch (the clutch sets up the connection to the reel mechanism)
- Reel mechanism (mechanical function as before)

The electric motor is supplied with current (direction of motor rotation "tension belt") and moves a so-called output wheel in the clutch by means of a gear. In the clutch, locking pawls move out and enter the clutch case. The clutch case is firmly connected to the drive shaft of the reel mechanism. This rolls up the seat belt.
To open the clutch, the direction of rotation of the electric motor must be briefly changed (opposite engine direction of rotation "tension belt"). If the connection between the electric motor and reel mechanism is interrupted, the reel mechanism works in the same way as a conventional mechanical reel mechanism.
There 2 Hall sensors integrated in the drive. One Hall sensor picks up the direction of rotation and speed of the drive shaft for the reel mechanism. The other Hall sensor picks up the rotary motion of the electric motor. The direction of rotation of the electric motor can be changed by means of the corresponding activation via the control unit (EMALI or EMARE control unit).







System functions
When the seat belt is fastened (door closed), the control unit for the electrically motorized reel on the left (EMALI control unit) or the control unit for the electrically motorized reel on the right (EMARE control unit) activates the drive once over a certain period of time. With the help of the electric motor, the seatbelt strap is rolled up, thus removing the belt slack.
In critical driving situations or in the event of a possible accident, the control unit also activates the drive. The duration is set in such a way that the drive is activated by the control unit until a collision occurs or until a critical driving situation ends.
To calculate whether there is a critical driving situation (e.g. vehicle oversteering), the two control units (EMALI control unit and EMARE control unit) use the data from the following systems:
- Integrated Chassis Management (ICM)
The ICM control unit provides the systems in the entire vehicle with the dynamic driving state in the form of signals (e.g. data such as lateral and longitudinal acceleration, yaw velocity).

- Dynamic Stability Control (DSC)
The DSC control unit delivers information such as the speed and brake pressure.

- Crash safety module (ACSM stands for "Advanced Crash Safety Module")
The crash safety module sends a message with the status of the seat belt buckle contacts.







Notes for Service department

General notes
The drive for the electrically motorized reel can be activated via the BMW diagnosis system.
If the drive for the left electrically motorized reel fails, the following behaviour is to be expected:
- Fault code memory entry in the control unit for inertia reel mechanism on the left (EMALI control unit) or control unit for inertia reel mechanism on the right (EMARE control unit)
- No effect on the mechanical function of the inertia reel mechanism

No liability can be accepted for printing or other faults. Subject to changes of a technical nature