Differential Limiting Device Screw Mechanism Actuation
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Solution Overview
Problem
Existing differential limiting devices for vehicles face issues with size increase due to the need for additional mechanisms like actuators to engage and disengage dog clutches for hard off-road conditions, leading to torque capacity shortages and potential friction clutch burning.
Innovation Solution
A differential limiting device that incorporates a clutch hub, clutch drum, friction clutch, and screw mechanism to convert rotary motion into linear motion, allowing for mechanical limitation of side gear rotation without increasing device size, using a low-output actuator and reducing electric power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dog clutch mechanism is added to mechanically limit differential rotation during hard off-road traveling, then torque capacity is improved, but device size increases
Solution Approach 1:
The patent combines the friction clutch and dog clutch into a single integrated differential limiting device. The friction clutch includes frictional engagement elements that can transition from friction contact to mechanical engagement, merging the functions of both clutch types into one compact structure. This eliminates the need for separate actuators for each clutch type, reducing overall device size while maintaining sufficient torque capacity for hard off-road conditions.
Solution Approach 2:
The friction clutch is designed to perform multiple functions: it provides friction-based differential limitation during normal operation and can transition to mechanical locking via the dog clutch mechanism during hard off-road traveling. This multi-functionality allows a single device to handle both soft and hard off-road conditions without requiring separate mechanisms, thereby reducing device size while ensuring adequate torque capacity across all operating conditions.
2Reliability
If the torque capacity of the friction clutch is increased to prevent slipping during hard off-road traveling, then reliability is improved, but device size and component dimensions increase
Solution Approach 1:
The patent merges the friction clutch and dog clutch into a single integrated system where the dog clutch mechanism is incorporated within the friction clutch structure. This allows the device to achieve high torque capacity through mechanical engagement of the dog clutch during hard off-road traveling without increasing the overall size of the friction clutch components. The integrated design enables compact dimensions while providing sufficient torque capacity through the combined friction and mechanical locking mechanisms.
3Adaptability or versatility
If additional actuation mechanisms are added to engage and disengage the dog clutch, then differential rotation control is improved, but device complexity increases
Solution Approach 1:
The patent combines the actuation mechanisms for the friction clutch and dog clutch into a single integrated actuator system. The actuator controls both the friction clutch piston and the dog clutch engaging/disengaging operations through a unified mechanism. This merging of actuation functions reduces the number of separate actuators and control mechanisms required, thereby reducing device complexity while maintaining full adaptability for differential rotation control under various driving conditions.
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
The solution effectively limits differential rotation while reducing the overall size and component count of the differential limiting device, maintaining torque capacity without the need for additional actuation mechanisms, thus addressing size and torque issues in hard off-road conditions.
Implementation Method 1
The screw mechanism includes a screw shaft member and a nut member which are screwed together. The screw mechanism is configured to convert rotary motion of the actuator into linear motion of the nut member in an axial direction of the side gear shaft
Implementation Method 2
The friction clutch includes a plurality of frictional engagement elements and a piston. The first frictional engagement elements are configured to be relatively non-rotatably engaged with the clutch drum. The second frictional engagement elements are configured to be relatively non-rotatably engaged with the clutch hub. The first frictional engagement elements and the second frictional engagement elements are configured to overlap with each other so as to be in friction contact with each other
Data Source
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AI summary
In a differential limiting device (66; 110; 120; 140) for a vehicle, when rotary motion of an electric motor (74) is converted by a screw mechanism (76, 146) into linear motion of a nut member (90; 144) in a direction of a first axis Cl of a side gear shaft (44; 124), and a piston (84; 112) mounted on the nut member (90; 144) is moved in a direction opposite to a direction to depress frictional engagement elements (82), the piston (84; 112) and a clutch drum (78; 114; 126) are relatively non-rotatably engaged. Therefore, differential rotation of a pair of side gears (56, 58) is mechanically limited. Thus, rotation of one electric motor (74) makes it possible to generate differential limiting torque for limiting differential rotation of the pair of side gears (56, 58) in a rear-wheel differential device (30).