Dual-Element Thermostat for Fast Coolant Feedback Control
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Solution Overview
Problem
Conventional cooling systems in heavy vehicles with hydraulic retarders suffer from slow temperature feedback, leading to 'temperature cycling' and reduced radiator lifetime due to the delayed response of thermostats to coolant temperature changes.
Innovation Solution
A compact thermostat device using two thermal expansion elements with sensor and stroke members to rapidly regulate coolant flow between a radiator and a radiator bypass line, based on coolant temperatures at two positions in the cooling system, allowing for rapid temperature changes to be indicated and addressed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional thermostat senses coolant temperature upstream of the radiator, then the thermostat can control coolant flow to the radiator, but the temperature feedback is slow leading to temperature cycling
Solution Approach 1:
The cooling system is segmented into two temperature sensing zones: the main coolant flow upstream of the radiator and a pilot circuit downstream of the radiator. This segmentation allows the thermostat to receive temperature information from both locations, enabling it to anticipate temperature changes before they affect the upstream coolant, thereby eliminating temperature cycling and protecting the radiator.
2Loss of time
If a pilot circuit is introduced to sense downstream coolant temperature, then temperature feedback speed improves, but the device complexity increases
Solution Approach 1:
The thermostat combines two thermal expansion elements into a single integrated structure where one element responds to upstream coolant temperature and the other to downstream pilot circuit temperature. These elements are merged with a common valve mechanism, allowing the thermostat to control coolant flow based on both temperature signals without requiring separate control systems, thus improving feedback speed while limiting complexity increase.
Solution Approach 2:
The pilot circuit serves multiple functions: it provides rapid temperature feedback from the downstream side, acts as a thermal conduit for the second expansion element, and enables the thermostat to anticipate temperature changes. This multi-functionality allows a single circuit to achieve several objectives that would otherwise require separate components.
3Productivity
If two thermal expansion elements are used to sense temperatures at two positions, then rapid temperature regulation is achieved, but the thermostat size increases
Solution Approach 1:
The thermostat employs a nested arrangement where the two thermal expansion elements are positioned concentrically or adjacently within a shared housing. The first expansion element (responding to upstream temperature) and the second expansion element (responding to downstream temperature) are integrated such that they share common structural support and actuate a single valve mechanism, reducing the overall volume compared to two separate thermostats.
Solution Approach 2:
The patent utilizes the vertical dimension by arranging the two thermal expansion elements at different heights or positions along the coolant flow path. This dimensional arrangement allows both sensing elements to operate independently while sharing the same horizontal footprint, effectively packing two temperature sensing functions into a compact vertical space.
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 rapid regulation of coolant flow, reducing temperature cycling and extending the lifespan of radiators by providing a fast and efficient response to temperature changes, maintaining a compact design with fewer components.
Implementation Method 1
a first thermal expansion element sensing the temperature of the coolant in the pilot circuit and providing a first stroke of the valve body in response to the temperature of the coolant in the pilot circuit
Implementation Method 2
a second thermal expansion element sensing the temperature of the received coolant and providing a second stroke of the valve body in response to said temperature
Data Source
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AI summary
The present invention relates to a thermostat device for a cooling system in a vehicle. The thermostat device (8) comprises at least one movably arranged valve body (16, 20, 34, 44) configured to distribute the coolant from an inlet (7') to two outlets (9', 10') in dependence on its position. The thermostat device (8) comprises a first thermal expansion element (31) configured to be in thermal contact with coolant entering the thermostat device via a pilot circuit (14) and to provide a first stroke of the valve body (16, 20, 34, 44) in response to the temperature of the coolant in the pilot circuit (14), and a second thermal expansion element (32) configured to be in thermal contact with the coolant received via the inlet (7') and to provide a second stroke of the valve body (16, 20, 34, 44) in response to the temperature of the coolant from the inlet (7') such that the valve body (16, 20, 34, 44) is moved to a position defined by the strokes from the thermal expansion elements (31, 32).