Electrohydraulic Actuator Worm Gear Angle Optimization
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Solution Overview
Problem
Conventional electrohydraulic actuators for motor vehicles experience increased wear on the piston due to tilting forces caused by friction and gearing forces, which can lead to reduced performance and increased leakage over extended periods, especially in safety-critical systems like brake systems.
Innovation Solution
An electrohydraulic actuator design that includes a spindle drive with a worm gear and a radial bearing to minimize radial forces on the piston by strategically selecting the angle between the worm's point of action and the rotation-prevention mechanism, allowing for axial and radial support of the nut, thereby reducing wear and maintaining hydraulic pressure over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional spindle drive with worm gear is used, then the actuator can convert rotary motion to linear motion, but tilting forces cause increased radial force on the piston leading to increased wear
Solution Approach 1:
The patent changes the geometric parameter of the rotation-prevention mechanism by defining a specific angle alpha between the force direction of the rotation-prevention mechanism and the radial direction. This angular parameter optimization allows the reaction force to have a component that counteracts the tilting force, thereby minimizing the radial force on the piston and reducing wear while maintaining reliable actuator operation
2Duration of action of stationary object
If the actuator operates for extended periods, then it can maintain hydraulic pressure, but friction and gearing forces cause tilting forces that increase leakage and reduce performance
Solution Approach 1:
The rotation-prevention mechanism is designed to preemptively counteract the tilting force generated by the worm gear before it can cause damage. By positioning the rotation-prevention mechanism at a specific angle, its reaction force creates a counterbalancing component that prevents excessive radial loading on the piston, thereby maintaining hydraulic pressure and preventing leakage during extended operation
3Object-affected harmful factors
If a second bearing is added to support radial forces, then piston wear can be reduced, but device complexity and cost increase
Solution Approach 1:
The patent extracts the force-balancing function from the bearing system and transfers it to the rotation-prevention mechanism. By optimizing the angular parameter of the rotation-prevention mechanism, the design eliminates the need for an additional radial bearing while still achieving the goal of minimizing radial piston force and reducing wear, thereby simplifying the device structure
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 reduces piston wear and leakage, maintains actuator performance, and allows for a more compact and cost-effective design by minimizing radial forces on the piston, while also compensating for misalignment and balancing forces within the actuator.
Implementation Method 1
Owing to the unavoidable friction between the nut and the spindle and the gearing forces on the nut
Implementation Method 2
In order to transmit the rotary motion of the electric motor to the nut and, at the same time, to reduce its speed, a worm gear can be used
Implementation Method 3
The nut is supported radially and axially by means of a bearing, and there is furthermore a single-armed rotation-prevention mechanism for securing the spindle against rotation
Implementation Method 4
an axial pump is used, comprising a hydraulic cylinder with a piston which can be actuated axially
Data Source
AI summary
The invention relates to an electrohydraulic actuator comprising a hydraulic piston, a spindle drive for moving the piston along an axis of rotation, wherein the spindle drive comprises a spindle and a nut, and a worm wheel, which is coaxially attached to the nut. Furthermore, an electric motor having a worm, which meshes with the worm wheel, is provided. The nut is radially and axially supported by means of a bearing. In addition, there is a single-armed rotation-prevention mechanism in order to prevent the spindle from rotating. An angle with respect to the axis of rotation is included between a point of action of the worm on the worm wheel and the effective direction of the rotation-prevention mechanism, wherein the angle is selected in such a way that, for a predetermined torque acting on the nut, a radial force acting on the piston is minimized.