Solenoid Valve Eddy Current Heating for Brake Fluid
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Solution Overview
Problem
Existing solenoid valve heating methods in vehicle brake systems, particularly at low temperatures, are inefficient due to temperature-dependent brake fluid viscosity and reliance on ohmic losses in coil windings for heating, leading to slower valve operation and reduced pressure build-up.
Innovation Solution
The method employs bipolar clocking with lower frequencies to induce eddy currents in the iron circuit of the solenoid valve, generating heat through electrical induction rather than ohmic losses, allowing for efficient heating of the fluid without mechanical valve reaction or with controlled mechanical operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ohmic losses in coil winding are used for heating, then the valve can be heated, but the heating efficiency is low and the heat path is long
Solution Approach 1:
The patent replaces the conventional ohmic heating method (electrical resistance heating through coil winding) with electromagnetic induction heating. The coil generates a time-varying magnetic field that induces eddy currents in the iron circuit, which directly heats the valve components and fluid. This substitution of heating mechanism dramatically improves heating efficiency by eliminating the long heat path through the winding carrier and directly heating the fluid at the magnet armature location.
Solution Approach 2:
The patent employs periodic alternating current through the coil winding to generate time-varying magnetic fields for electromagnetic induction. The periodic nature of the AC current creates oscillating magnetic flux that continuously induces eddy currents in the iron circuit, maintaining efficient heating. The frequency of the alternating current is specifically selected to optimize both heating efficiency and avoid unwanted valve actuation.
2Loss of energy
If bipolar clocking with lower frequency is used, then heating efficiency is improved, but valve reaction may occur
Solution Approach 1:
The patent carefully selects and adjusts the frequency parameter of the alternating current applied to the coil. The frequency is chosen to be low enough to generate sufficient eddy currents for efficient heating, but high enough to prevent the magnetic force from causing unwanted valve armature movement. This optimal frequency selection balances heating efficiency with valve operational stability, resolving the contradiction between these two requirements.
3Temperature
If the coil winding heats the fluid directly, then heating is achieved, but the heat path is long and separated by winding carrier
Solution Approach 1:
The patent replaces conductive heating through the winding carrier with electromagnetic induction heating. The time-varying magnetic field penetrates the valve structure and directly induces eddy currents in the iron circuit components that are in contact with or close to the fluid. This eliminates the need for heat conduction through the plastic winding carrier, dramatically shortening the effective heat path and enabling direct heating of the fluid at the magnet armature location.
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 approach significantly enhances heating efficiency by directly heating the fluid and iron components, improving valve operation speed and pressure build-up across a range of temperatures, while minimizing undesirable magnetic forces and DC current components.
Implementation Method 1
bipolar clocking with a significantly lower frequency is now used. While the complete heating power is generated in the coil with the conventional preheating functionality, only a small part of the total heating power is generated in the coil in embodiments of the present invention, while a multiple of the coil losses now arise inductively directly in the iron circuit of the solenoid valve
Implementation Method 2
generate eddy currents in the iron circuit of the solenoid valve and in the capsule, which heat the fluid present in the valve cartridge
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a solenoid valve (1) for a vehicle braking system, comprising a magnet assembly (20) that comprises a winding support (22), a coil winding (24), a housing (26), and a cover disc (28) and comprising a valve cartridge (10) that comprises a capsule (12), a valve insert (16) which is connected to the capsule (12), an armature (14) which is guided within the capsule (12) in an axially movable manner between a closed position and an open position and which comprises a closing element, and a valve insert (16) which is connected to the capsule (12) and which comprises a valve seat. The closing element and the valve seat form a valve which adjusts a fluid flow through the valve cartridge (10). The magnet assembly (20) coil winding (24), which is applied onto the winding support (22), forms an electric coil which can be actuated by control signals applied via electric connections (24.1, 24.2) and generates a magnetic force that moves the armature (14) against the force of a restoring spring (18), the fluid temperature within the valve cartridge (10) being variable during a heating operation on the basis of the control signals. According to the invention, the control signals are applied to the coil winding (24) in the form of bipolar alternating signals with a specified frequency and generate eddy currents in the iron core of the solenoid valve (1) and in the capsule (12), said eddy currents heating the fluid (3) provided in the valve cartridge (10).