Solenoid valve coil having an integrated bobbin and flux ring assembly

An Electronic Brake Control System (EBCS) is often included as standard equipment on new vehicles. When actuated, the EBCS is operative to modulate the pressure applied to the vehicle wheel brakes. A typical EBCS includes a plurality of solenoid valves mounted within a control valve body and connected to the vehicle hydraulic brake system between the brake master cylinder and the individual wheel brake cylinders. The solenoid valves usually are normally open, or isolation, valves and normally closed, or dump, valves. Proportional solenoid valve also can be included. The valve body further includes one or more accumulators for the temporary storage of brake fluid during an operating cycle of the EBCS.



An EBCS further includes an electronic control module which has a microprocessor. The microprocessor is electrically connected to the pump motor, a plurality of solenoid coils associated with the solenoid valves, and wheel speed sensors for monitoring the speed and deceleration of the vehicle wheels. The microprocessor also is typically electrically connected to the brake light switch and receives a signal from the switch when the vehicle brakes are applied. Additionally, the EBCS may include one or more accelerometers which also are connected to the microprocessor.



Another mode of operation provides Traction Control (TC). If the microprocessors detect excessive slip of a driven wheel when the wheel brakes are not applied, the EBCS will apply the brakes to the slipping wheel and thereby transfer more engine torque to the non-slipping wheel.




The solenoid coil 20 is of conventional design, comprising a winding 24 formed from multiple turns of an insulated magnet wire having a round cross section, such as #28 ? magnet wire. The magnet wire is helically wound upon a plastic bobbin 26. The bobbin 26 has a cylindrical center portion 28 that terminates in upper and lower flanges, 30 and 32, respectively. A pair of terminal pin supports 34 extend in an axial direction from the top of the bobbin 26. Each of the supports 34 is molded over a terminal pin 36. An end 38 of the coil winding wire is wound around the base of each of the terminal pins 36 and soldered thereto. The pins 36 are electrically coupled to via a printed circuit board (not shown) to the EBCS microprocessor.



When it is necessary to actuate the valve 10 during an anti-lock braking cycle, an electric current is supplied through the terminal pins 36 to the solenoid coil 20. The current establishes a magnetic field in the armature which pulls the armature in a downward direction, closing the ball valve. When the current is interrupted, the magnetic field collapses, allowing the spring to return the armature to its original position, thereby reopening the ball valve. An EBCS control unit also typically includes other digital solenoid valves, such as normally closed solenoid valves (not shown), which have structures similar to the normally open valve 10 described above. Additionally, an EBCS control unit can include proportional solenoid valves.



For electronic brake control systems being currently developed, vehicular solenoid valves can be energized for long periods of time. The energized coils generate heat that must be conducted away from the coils to avoid overheating. Conventional coil bobbins typically have air gaps and low-pressure contacts between the bobbins and the metal parts of the other components of the control system. Accordingly, current units have poor heat conduction properties. Therefore, a coil assembly having improved heat conduction properties would be desirable.



The present invention contemplates a bobbin assembly for a solenoid valve coil that includes a bobbin formed from an electrically insulative material with a stepped bore extending axially therethrough. The bobbin assembly filter includes a flux ring formed from a magnetically permeable material having a high heat conductivity. The flux ring has an annular base portion and a tubular sleeve extending axially into an end of the bobbin bore. The bobbin has a pair of flanges formed upon the ends thereof. A winding is wound upon the bobbin between said flanges.