Divided Disc Brake Piston Structure for Stable Parking Brake Force
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Solution Overview
Problem
In electric parking brake type disc brake devices, the coupling structure of the piston main body and piston cap leads to slippage and idling issues when the spindle rotates, causing instability in braking force and potentially increasing the temperature of brake oil, which can result in vapor lock phenomena.
Innovation Solution
A disc brake device with a divided piston structure and a unidirectional rotation regulating portion between the piston main body and piston cap, allowing relative rotation in the reverse direction to prevent torque buildup and maintain stable braking force, while preventing heat transfer to the brake oil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the piston main body and piston cap are coupled by fitting a convex portion into a concave portion, then the structure is simple and easy to manufacture, but slippage occurs between the piston cap and piston main body when torque is applied, causing the piston main body to idle and making it difficult to stably obtain braking force
Solution Approach 1:
The invention applies asymmetry by providing rotation prevention protrusions on the piston cap that asymmetrically engage with rotation prevention grooves on the piston main body. This asymmetric coupling prevents relative rotation between the piston cap and piston main body when torque is applied, eliminating the idling problem while maintaining manufacturing simplicity. The protrusions and grooves are specifically designed with non-circular cross-sections that allow easy assembly but prevent rotation under load.
Solution Approach 2:
The invention implements preliminary action by pre-forming the rotation prevention protrusions and grooves during the manufacturing process. These features are built into the piston cap and piston main body before assembly, so that when the piston is assembled, the anti-rotation function is already in place. This preliminary preparation ensures that braking force is stably transmitted without any idling or slippage from the moment the brake is applied.
2Reliability
If the piston main body and piston cap are coupled to prevent relative rotation, then idling is prevented and braking force stability is improved, but when the nut is fully released to the limit position, the nut and spindle become locked, causing the electric motor to reach stall torque and reducing durability
Solution Approach 1:
The invention applies segmentation by dividing the piston into two separate components: the piston main body and the piston cap. This segmentation allows independent design optimization - the piston cap can be designed with rotation prevention features to ensure braking stability, while the piston main body can be designed with a limited rotation range to prevent the nut from reaching the locked position. The segmented structure enables the system to achieve both braking force stability and motor durability by allowing controlled relative rotation between the two segments.
Solution Approach 2:
The invention implements parameter changes by controlling the rotation angle parameter of the piston main body relative to the piston cap. By limiting the rotation range to within ±45 degrees from the parallel position, the system changes the rotational parameter to prevent the nut from reaching the locked position where stall torque occurs. This parameter control allows the electric motor to operate within its safe torque range while still providing stable braking force through the rotation prevention mechanism.
3Ease of manufacture
If the piston has an integral structure, then manufacturing is simpler, but heat is transferred from the pad to the brake oil via the piston, causing brake oil temperature to rise and leading to vapor lock phenomenon
Solution Approach 1:
The invention applies segmentation by dividing the piston into two separate components: the piston main body and the piston cap. This segmentation creates a thermal barrier between the pad (which contacts the piston cap) and the brake oil (which is contained by the piston main body). The interface between the cap and main body, combined with the rotation prevention mechanism, provides thermal insulation that prevents heat transfer to the brake oil, thereby preventing vapor lock while maintaining acceptable manufacturing complexity through standard machining operations.
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 enables stable braking force and prevents brake oil temperature rise, addressing issues of slippage and durability concerns in the electric motor and speed reduction mechanism.
Implementation Method 1
heat is transferred to the brake oil via a piston... the amount of heat transferred to the brake oil can be reduced as compared with a case where the piston has an integral structure
Implementation Method 2
a rotary-to-linear motion conversion mechanism configured to convert a rotary motion of a drive source into a linear motion to push the piston toward the rotor
Data Source
AI summary
A disc brake device includes a pad, a caliper including a cylinder, a piston, and a rotary-to-linear motion conversion mechanism. The piston is divided into two parts that are a piston main body and a piston cap. The rotary-to-linear motion conversion mechanism includes a rotary member and a linear motion member. A unidirectional rotation regulating portion between the piston main body and the piston cap is configured to regulate relative rotation of the piston main body in a forward rotation direction with respect to the piston cap when the rotary member is driven to rotate in the forward rotation direction, and to allow relative rotation of the piston main body in a reverse rotation direction with respect to the piston cap when the rotary member is driven to rotate in the reverse rotation direction.