Transfer Case H4L Switching for Four-Wheel Drive Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Four-wheel drive vehicles face difficulties in medium to high-speed movement and controllability on low-friction surfaces when the clutch fails, as existing systems struggle to adjust torque effectively, leading to excessive driving force and poor handling.
Innovation Solution
A transfer mechanism that includes a high-low switching mechanism and a locking sleeve, driven by an electric motor, which can switch between H4L and L4L positions to lock the output shaft and output member together, enabling high-speed gear engagement and improved controllability, even when the clutch is malfunctioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vehicle switches to the L4L position with low-speed gear established when the clutch fails, then torque can be transmitted to the auxiliary driving wheels, but medium- to high-speed driving becomes difficult and vehicle mobility is severely reduced
Solution Approach 1:
The patent implements dynamic switching capability between H4L and L4L positions through the switching mechanism, allowing the vehicle to adapt its gear state based on driving conditions. The high-low sleeve can dynamically shift between high-speed and low-speed gears, enabling the vehicle to maintain medium- to high-speed driving capability (H4L position) under normal conditions while retaining low-speed torque multiplication (L4L position) when needed, thus resolving the contradiction between reliability and speed.
2Reliability
If the vehicle operates in the L4L position with low-speed gear and locked 4WD, then torque is transmitted to auxiliary driving wheels, but driving force becomes excessive and controllability deteriorates on low-friction surfaces
Solution Approach 1:
The switching mechanism enables dynamic adjustment between H4L and L4L positions, allowing the driver or control system to select the appropriate gear state based on surface conditions. On low-friction surfaces, the vehicle can operate in H4L position with moderate driving force for better controllability, while switching to L4L position only when sufficient torque to auxiliary wheels is required, thus resolving the contradiction between reliability and ease of operation.
Solution Approach 2:
The patent changes the gear ratio parameter by switching between high-speed gear (H4L) and low-speed gear (L4L) in the high-low switching mechanism. This parameter change allows the vehicle to adjust its driving characteristics: using high-speed gear for normal conditions with better controllability, and low-speed gear for conditions requiring enhanced torque transmission, thereby resolving the contradiction between torque transmission capability and controllability.
3Device complexity
If a single electric motor controls both the high-low switching mechanism and the 4WD locking mechanism, then device complexity is reduced, but the switching mechanism must precisely coordinate multiple functions which increases control difficulty
Solution Approach 1:
The patent merges the control functions of the high-low switching mechanism and the 4WD locking mechanism into a single electric motor (motor 84). This single motor controls both the high-low sleeve (62) and the locking sleeve (70) through a unified control system, reducing device complexity by eliminating the need for separate motors while integrating multiple switching functions into one actuator system.
Solution Approach 2:
The switching mechanism is segmented into distinct functional components: the high-low switching mechanism (controlling the high-low sleeve) and the 4WD locking mechanism (controlling the locking sleeve). This segmentation allows the single electric motor to control different functions through separate control paths (first switching control and second switching control), making the coordination of multiple functions more manageable despite using one motor.
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
Enables the vehicle to maintain medium to high-speed operation and improve controllability on low-friction surfaces by establishing a high-speed gear in the H4L position, ensuring efficient power transmission and stable vehicle performance.
Implementation Method 1
The screw mechanism includes a threaded shaft member, a nut member, and an electric motor. The threaded shaft member and the nut member are supported by the output shaft and are screwed together. The electric motor is configured to rotatably drive one of the threaded shaft member and the nut member so that the nut member moves linearly in the axial direction of the output shaft.
Implementation Method 2
The drum cam is configured to convert a rotational motion of the electric motor into a linear motion in the axial direction of the output shaft.
Implementation Method 3
The locking sleeve is configured to move in the axial direction of the output shaft. The locking sleeve is supported by the output shaft in a manner so that the locking sleeve is unable to rotate around the axis of the output shaft relative to the output shaft. The locking sleeve is configured to selectively engage with the output member so that the output shaft and the output member lock together.
Implementation Method 4
The high-low switching mechanism is configured to change a rate of rotation input from the input shaft and transmit the resultant rotation to the output shaft by a motion of a high-low sleeve in an axial direction of the output shaft
Data Source
AI summary
A transfer for a four-wheel drive vehicle includes an input shaft, an output shaft, a high-low switching mechanism, an output member, a clutch, a locking sleeve, a screw mechanism, a transmitting mechanism, a drum cam, and a switching mechanism. The switching mechanism is configured to selectively switch between an H4L position and an L4L position in conjunction with rotational motion of the electric motor. The H4L position is a position in which a high-low sleeve provided in the high-low switching mechanism is in a position in which a high-speed gear is established in the high-low switching mechanism. The L4L position is a position in which the high-low sleeve provided in the high-low switching mechanism is in a position in which a low-speed gear is established in the high-low switching mechanism.