External-Motor Parking Lock With Sealed Shaft and Internal Cam
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Solution Overview
Problem
Existing parking lock designs for motor vehicles are complex, requiring separate wire harnesses and are prone to transmission oil ingress, which complicates the construction and reliability of the electric drive system.
Innovation Solution
A parking lock design featuring a rotatable shifting shaft driven by an external electric motor, with a cam mechanism inside the transmission housing, utilizing a torsion spring for blocking and releasing the parking lock wheel, and a single external wire harness, while sealing the shifting shaft to prevent contamination and oil leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the drive motor is disposed inside the transmission housing, then the parking lock can be compactly integrated, but the electric drive becomes vulnerable to transmission oil ingress and requires separate wire harnesses
Solution Approach 1:
The drive motor is extracted from the transmission housing and positioned externally. This separation removes the electric drive from the harmful environment inside the transmission housing, eliminating the risk of transmission oil ingress while maintaining compact integration through the penetrating shifting shaft mechanism
Solution Approach 2:
The shifting shaft acts as an intermediary element that penetrates the transmission housing wall, transmitting rotational motion from the externally positioned drive motor to the cam mechanism inside. This intermediary allows the drive to be externally positioned for protection while still controlling internal components
2Reliability
If separate wire harnesses are provided for interior and exterior of transmission housing, then electrical connections are ensured, but the construction complexity increases
Solution Approach 1:
The wire harnesses for the interior and exterior are merged into a single external wire harness. The drive motor's external positioning allows both electrical connections to be routed through one harness outside the transmission housing, eliminating the need for separate internal wiring while maintaining reliable electrical connectivity
3Reliability
If the shifting shaft is surrounded by a torsion spring, then the cam can be reliably moved between states, but the friction and required drive output increase
Solution Approach 1:
The torsion spring is pre-loaded to store elastic energy that automatically moves the cam between blocked and releasing states. This preliminary energy storage in the spring eliminates the need for the drive motor to continuously overcome friction, reducing the required drive output while ensuring reliable state transitions through the spring's stored energy
4Reliability
If the shifting shaft is sealed with a sealing element, then contamination ingress and oil leakage are prevented, but the friction increases
Solution Approach 1:
A sealing element in the form of a flexible seal (such as an O-ring or lip seal) is used around the shifting shaft where it penetrates the transmission housing. This flexible film-like seal prevents contamination ingress and oil leakage while allowing the shaft to rotate, minimizing friction compared to rigid sealing methods
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design simplifies the construction, ensures reliable performance by protecting the electric drive from transmission oil, and applies a high holding force with reduced friction and operational output, eliminating the need for separate ventilation.
Implementation Method 1
A refinement of the invention provides that the shifting shaft is surrounded by a torsion spring which is fastened to the shifting shaft, on the one hand, and to the cam, on the other hand. The torsion spring moves the cam that blocks the parking lock wheel when the shifting shaft is pivoted from the releasing state to the blocked state.
Implementation Method 2
The shifting shaft in relation to the transmission housing is sealed by a sealing element. The sealing element prevents the ingress of contamination into the interior of the transmission housing, while the leakage of transmission oil through the transmission housing to the outside is prevented at the same time.
Implementation Method 3
In order for an operation of the parking lock according to the invention with particularly little friction to be guaranteed, it can be provided that the shifting shaft is mounted on or in the transmission housing by a friction bearing or a roller bearing.
Implementation Method 4
In order for an operation of the parking lock according to the invention with particularly little friction to be guaranteed, it can be provided that the shifting shaft is mounted on or in the transmission housing by a friction bearing or a roller bearing.
Data Source
AI summary
Parking lock (1, 19, 24) for a motor vehicle, having a movable locking means for impinging a parking lock wheel (14), disposed in the interior of a transmission housing (2), with a holding force, wherein the movable locking means, by means of a shifting shaft (3) that is rotatable by a drive motor (4) and a cam (7) that is coupled to the shifting shaft (3) is pivotable between a releasing state, in which the parking lock wheel (14) is rotatable, and a blocked state, in which a rotation of the parking lock wheel (14) is blocked, wherein the drive motor (4) is disposed outside the transmission housing (2), the shifting shaft (3) penetrates the transmission housing (2), and the cam (7) is disposed within the transmission housing (2). The invention moreover relates to a transmission having a parking lock (1, 19, 24) of this type, and to a drive installation for electrically drivable motor vehicle.