Electric Parking Brake Actuator With Quiet Screw Motion Conversion
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Solution Overview
Problem
The existing electric actuator in electric parking brake devices experiences slapping sounds due to unavoidable play in the movable portions of the motion conversion mechanism, which includes both the male and female thread members.
Innovation Solution
The electric actuator incorporates a motion conversion mechanism with a first member that is blocked to execute both rotational and rectilinear motions, and a second member that engages with the first member to generate a rectilinear motion through thread engagement, featuring a lubricant reservoir for smooth operation and a fixed first member to the actuator case to minimize movable parts, along with a transmission member connected via a bearing and an elastic member to stabilize the braking state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If both male and female thread members are made movable to enable motion conversion, then the motion conversion function is achieved, but slapping sound occurs due to play in movable portions
Solution Approach 1:
The patent inverts the conventional design by making the male thread member movable and the female thread member fixed. This reversal eliminates the slapping sound issue while maintaining the motion conversion function, as the movable male thread member engages with the fixed female thread member to convert rotational motion to linear motion without excessive play.
2Ease of operation
If multiple movable portions are provided in the motion conversion mechanism, then the motion conversion mechanism can function, but the number of movable portions increases causing more slapping sound
Solution Approach 1:
By inverting which thread member is movable and which is fixed, the patent reduces the number of movable portions from two (both male and female threads movable) to one (only male thread movable), thereby reducing slapping sound while preserving motion conversion capability.
3Ease of operation
If a lubricant reservoir is added to the second member, then thread engagement smoothness is improved, but device complexity increases
Solution Approach 1:
The lubricant reservoir is integrated into the female thread member structure, allowing the system to self-lubricate during operation. The reservoir automatically supplies lubricant to the thread engagement interface, eliminating the need for external lubrication systems while ensuring smooth operation.
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 reduces slapping sounds, enhances quietness, and stabilizes the braking state by minimizing movable parts and ensuring smooth thread engagement and transmission, thereby improving the overall performance of the electric actuator and parking brake device.
Implementation Method 1
a male thread member that is allowed to execute only the rectilinear motion, and is supported by an actuator case; and a female thread member supported by the actuator case such that the female thread member is allowed to execute only rotation while threadedly engaging with the male thread member
Implementation Method 2
a lubricant reservoir that a thread portion of the first member faces is provided to the second member
Data Source
AI summary
Provided is an electric actuator which has fewer movable portions of a motion conversion mechanism so that slapping sound less liable to occur at the time of operation of an electric drive unit, and hence has quietness. An electric actuator includes: an electric driving source configured to generate a rotational motion as a driving force; and a motion conversion mechanism configured to convert the rotational motion to a rectilinear motion.The motion conversion mechanism includes: a first member configured to be blocked to execute a rotational motion and a rectilinear motion; and a second member configured to engage with this first member to relatively rotate with respect to this first member, to thereby generate a rectilinear motion. This second member is configured to be rotationally driven by the driving force of the electric driving source.