Normal Brake Pressure Transmitter 96GG
Figure 010
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F. Normal Brake Servovalve Manifolds 2612GM and 2613GM
(Ref. Fig. 011)
The manifold includes:
-
a manifold assembly
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a filter
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two servovalves
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two safety valves
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two pressure transducers The body of the manifold assembly is machined externally to give faces for the servovalves, the safety valves and the pressure transducers.Holes are machined internally to connect these faces.The body includes four unions which are the connections for the fluid supply, the fluid return and the two service line connections.
A filter is installed near the supply connection to keep the holes through the body (and the components attached) free from contamination.A sealed plug keeps the filter in position.
The machined faces for the externally installed components have holes to make the hydraulic connections.The faces for the safety valves have two bobbins and a filter installed.The bobbins align and seal the faces of the safety valves.
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Normal Brake Manifold
Figure 011
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G. Normal-Brake Pressure Transducers
(Ref. Fig. 012)
The brake pressure transducers are installed on the manifold of the Normal brake servovalve, one downstream of each servovalve. The pressure transducer measures the hydraulic pressure in the related brake service line. It contains an electronic bridge-type circuit which is installed on a number of circuit boards. Hydraulic pressure sent to the transducer causes a change in the electrical resistance of the brigde circuit.This changes the electrical input voltage to give an output voltage in proportion to the hydraulic pressure. The integrated-logic transducer supplies a DC voltage between 1 and 5V for a pressure signal between 0 and 200 bars.The zero has been shifted to enable BITE testing.
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Normal- Brake Pressure Transducer
Figure 012
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H. Normal Brake Servovalve
(Ref. Fig. 013, 014, 015, 016)
The servovalve supplies a pressure proportional to the current which passes through the control coil used. The servovalve is an electro-hydraulic valve that includes a hydraulic assembly with an electrical assembly attached. The valve has three primary positions of operation, with more positions of operation between the primary positions. The valve is electrically controlled to keep the pressure in its related brake service line at the necessary value, or release the pressure.
The hydraulic assembly has a body with a control bore and a distribution bore. The body is drilled to connect these two bores and to make a supply port A, a service port B and a return port C. The control bore contains two nozzles that are the same. The nozzles are held stable in the bore and each is connected to its related end of the distribution bore. The distribution bore contains a slide valve which can move in the bore to connect two ports together.
The electrical assembly has a body with an electrical plug-in type connector. The assembly includes a top and bottom pole piece. Two permanent magnets keep the pole pieces stable and apart. Two coils are installed between the pole pieces. The coils connect to the electrical connector and this connects each coil to its related channel of the BSCU.
The electrical assembly has a flapper assembly that includes an armature. The armature is installed between the pole pieces. The flapper is installed in the armature. The flapper goes between the nozzles in the control bore then through to the slide valve.
When the coil is de-energized, the slide valve connects port B to port C (brakes released).
When the coil is energized:
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the flapper moves nearer the nozzle 1
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the flow through the nozzle 2 is more than the flow through the nozzle 1
-a larger pressure decrease occurs across jet 2 than jet 1
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the pressure at one end of the slide valve is more than the pressure at the opposite end
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the slide valve moves to connect port A to port B, it controls the pressure (that goes to the brakes) to a specified value.
When the pressure at port B is at the necessary pressure:
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