Reducing Agent Heater Plastic Casing Insertion
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Solution Overview
Problem
Existing reducing agent heaters for motor vehicles suffer from cracking due to plastic shrinkage and thermal expansion differences, leading to potential contact between the reducing agent and the heat transfer body, which can cause chemical and electrical interactions and result in heater failure.
Innovation Solution
A reducing agent heater design where the heat transfer body is inserted into a prefabricated plastic casing after the shrinkage process, ensuring a non-positive fit and complete encapsulation to prevent direct contact and ensure reliable operation, using a thermally conductive metal heat transfer body and electrical heating elements, with a plastic casing and cover for insulation and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the plastic casing is molded directly around the heat transfer body, then the heat transfer body is protected from the reducing agent, but cracks form in the plastic casing due to shrinkage and thermal expansion differences
Solution Approach 1:
The plastic casing is divided into two separate components: the casing itself and the heat transfer body. This segmentation allows the plastic casing to be manufactured independently without the heat transfer body, avoiding the shrinkage and thermal expansion conflicts that occur when molding around the heat transfer body. The heat transfer body is then inserted into the pre-formed casing, maintaining protection while preventing cracks.
Solution Approach 2:
The plastic casing is manufactured and allowed to complete its shrinkage process before the heat transfer body is inserted. This preliminary action ensures that the plastic casing reaches its final dimensions and stabilizes thermally before the heat transfer body is introduced, preventing subsequent cracking due to differential shrinkage or thermal expansion.
2Reliability
If the plastic casing is molded around the heat transfer body, then encapsulation is achieved, but the shrinkage process causes cracks and potential heater failure
Solution Approach 1:
The manufacturing process is segmented into two independent steps: first manufacturing the plastic casing, then separately inserting the heat transfer body. This eliminates the complexity of coordinating simultaneous cooling and solidification of plastic around a heat transfer body, while still achieving complete encapsulation through the insertion process.
Solution Approach 2:
The plastic casing is manufactured and allowed to shrink completely before the heat transfer body is inserted. This preliminary completion of the shrinkage process simplifies the overall manufacturing by decoupling the plastic formation and heat transfer body integration steps, avoiding the complexity of managing both processes simultaneously.
3Reliability
If the heat transfer body is inserted into the prefabricated plastic casing, then cracking is prevented and long-term reliability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The plastic casing and heat transfer body are manufactured as separate components using optimized individual processes, then assembled through simple insertion. This segmentation allows each component to be manufactured using the most suitable process for its material and function, improving long-term reliability while the simple insertion process minimizes the added manufacturing complexity.
Solution Approach 2:
The heat transfer body is inserted into the receiving recess of the plastic casing, creating a nested structure where one component fits within another. This nesting approach achieves complete encapsulation and protection while maintaining a compact design, and the insertion process is simpler than co-molding, balancing manufacturing ease with reliability.
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 prevents cracking and ensures long-term, reliable operation by allowing the plastic casing to shrink before the heat transfer body is inserted, providing efficient heat transfer and insulation, thus preventing chemical and electrical interactions and extending the service life of the heater.
Implementation Method 1
the heat transfer body consists of a thermally conductive material, in particular a metal, preferably aluminum or an aluminum alloy. Due to its thermal conductivity, the heat transfer body enables the heat generated by the heating element to be transferred to the reducing agent
Implementation Method 2
The plastic jacket at least partially surrounding the heat transfer body serves to protect the heat transfer body from the chemically reactive reducing agent, i.e. to prevent chemical reactions between the reducing agent and the heat transfer body, and to electrically insulate the heat transfer body
Implementation Method 3
Since the plastic is subject to a shrinkage process after overmoulding, i.e. a change in volume or shape, cracks can form in the plastic overmoulding. The plastic casing is therefore prefabricated and has a receiving recess into which the heat transfer body can be inserted
Data Source
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AI summary
The invention relates to a reducing agent heater (1) of a motor vehicle for heating a reducing agent, particularly a reducing agent for the selective catalytic reduction of nitric oxide in the exhaust gases of a combustion engine of the motor vehicle, having a heat transmission body (2) and at least one heating element (5) arranged therein, wherein the heat transmission body (2) is surrounded at least partially by a plastic sheathing (8) in order to prevent direct contact with the reducing agent. It is proposed that the heat transfer body (2) is arranged inserted into an accommodating recess (9) provided for the heat transmission body (2) in the prefabricated plastic sheath (8). The invention further relates to a method for producing such a reducing agent heater (1).