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Advanced Vehicle Technology Episode 3 Part 8

Tham khảo tài liệu 'advanced vehicle technology episode 3 part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | until with the secondary brake position the delivered pressure is zero. In other words the upright valve delivers a gradually increasing pressure to the trailer brake actuators and at the same time the inverse valve assembly allows the air pressure on the tractor spring brake actuators to be gradually released. Park brake application Fig. 12.18 c When the handle is moved from the secondary brake position to the park position the cam lifted by the leverage of the handle about its pivot allows the upright plunger and the inverse plunger to be raised. The air pressure in both tractor and trailer brake actuators then exhaust into the atmosphere. The tractor brakes are now applied in the park position by the mechanical force exerted by the spring actuators. 12.3.14 Relay valve piston type Bendix Fig. 12.19 a and b Purpose The relay valve is used to rapidly operate a part of a braking system when signalled by either a foot or hand control valve. This is achieved by a small bore signal line feeding into the relay valve which then controls the air delivery to a large bore output service line. As a result a small variation in signal pressure from the foot or hand valve will produce an instant response by the relay valve to admit air from the service reservoir directly to the service line brake system. Operation Brakes applied Fig. 12.19 a When the brakes are applied a signal pressure from the foot control valve or hand control valve reacts on the large control piston which responds by moving downwards rapidly until the centre stem of the piston closes the exhaust passage. The downwards movement of the piston pushes open the inlet valve. Air will now be admitted to the underside of the piston as it flows through to the service line and brake actuator. Movement of air from the service reservoir to the service line continues until the combined upthrust of both piston and valve springs and the air pressure balances the air signal pressure force pushing the piston downwards. The