Sistema de Frenos de Aire 793D

7/28/2019 Sistema de Frenos de Aire 793D

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Operacin de Sistemas793D Off-Highway Truck Air System and Brakes

Air Flow Schematic

SMCS - 4250

Air Start (If Equipped)

Cerrar SIS

Pantalla anterior

Producto: TRUCKModelo: 793D TRUCK FDBConfiguracin: 793D Off-Highway Truck FDB00001-UP (MACHINE)POWERED BY 3516B Engine

Nmero de medio -RENR8330-01 Fecha de publicacin -2006/10/01 Fecha de actualizacin -2006/10/26

i02643866

Pgina 1 de 12793D Off-Highway Truck FDB00001-UP (MACHINE) POWERED BY 3516B Engine(SEBP397...

12/03/2008https://sis.cat.com/sisweb/sisweb/techdoc/techdoc_print_page.jsp?returnurl=/sisweb/sisweb/products...PDF created with pdfFactory trial version www.pdffactory.com
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Illustration 1 g01201621

(1) Air tank check valve

(2) Primary air tank

(3) Starter relay valve (If Equipped)

(4) Air starting motor (If Equipped)

(5) Air compressor with air compressor governor

(6) Starter solenoid valve (If Equipped)

(7) External air supply

(8) Air dryer with air relief valve

(9) Air suspension seat

(10) Solenoid valve for autolube




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Note: The darkened lines show air pressure and the arrows show the direction of flow.

If the pressure in primary air tank (2) is above the cut-in pressure of the air system pressure protection valve (14) ,air will flow through pressure protection valve (14) . If the pressure in primary air tank (2) is below the cut-inpressure of the air system pressure protection valve (14) , you will need to charge the system with an external airsupply (7) . System air pressure is monitored by brake air pressure sensor (15) .

If the system is equipped with an air starting motor, then some of the air that flows through air system pressureprotection valve (14) supplies starter solenoid valve (6) . When the key start switch is turned to the start position,starter solenoid valve (6) is electrically opened. When starter solenoid valve (6) is open, air from pressureprotection valve (14) will flow into air starting motor (4) . The air flow pneumatically engages the starter pinionwith the engine flywheel ring gear. When the starter pinion is engaged, internal passages allow air to flow fromstarter solenoid valve (6) to the control passage of starter relay valve (3) . This air flow causes starter relay valve (3)to open. Air now flows from primary air tank (2) to air starting motor (4) . Air starting motor (4) will crank theengine.

If the system is equipped with an air starting motor, then the following applies. When the engine is started and thekey start switch is released from the start position, starter solenoid valve (6) closes. The flow of air to the starter

pinion is stopped. The gear is disengaged by a spring. This also stops air flow to the control passage of starter relayvalve (3) . Starter relay valve (3) closes. Air starting motor (4) disengages.

The engine drives the air compressor. The air compressor has two cylinders. When the engine is started, the airpressure from the air compressor will build up until the air pressure reaches the cut-in pressure of the aircompressor governor. Then, air flow from the two cylinders of the air compressor will flow to air dryer (8) . The airflows from air dryer (8) to one-way check valve (1) and into primary air tank (2) . When the pressure in the systemis above the cut-in pressure of the air system pressure protection valve, pressure protection valve (14) will be open.Pressure protection valve (14) must be open to supply air to starter solenoid valve (6) , air suspension seat (9) ,machine autolube solenoid (10) , attachment air suspension buddy seat (11) , attachment cleanout hose (12) , airhorn solenoid (13) , secondary air tank (16) , and the wastegate for the engine. When the air pressure in all of the air

tanks reaches the cutout pressure of the air compressor governor, the flow of air into the system will be stopped.When the pressure falls to the cut-in pressure of the air compressor governor, air will flow through the air dryers tothe rest of the system. If the pressure in the system drops below 415 kPa (60 psi), the action alarm will sound in thecab.

The Parking Brake Reset Valve Is Open

(11) Attachment air suspension buddy seat

(12) Attachment cleanout hose

(13) Air horn solenoid

(14) Air system pressure protection valve

(15) Brake air pressure sensor

(16) Secondary air tank




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Note: Secondary brake and parking brake pressure switch (18) is activated when air control valve (19) for theparking brake is in the ON position and parking brake reset valve (22) is closed.


The engine is operating. The parking brake reset valve is open. The parking brake control valve is in the ON position. The secondarybrake air control valve is in the OFF position.


(17) Parking and secondary brake valve

(18) Secondary brake and parking brake switch

(19) Parking brake control valve

(20) Secondary brake air control valve

(21) Secondary brake inverter valve

(22) Parking brake reset valve




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Air pressure from secondary air tank (16) flows to the secondary brake air control valve (20) and the parking brakereset valve (22) . With secondary brake air control valve (20) in the OFF position, air pressure from the secondaryair tank (16) would be able to flow to the secondary brake inverter valve (21) and the air control valve (19) for theparking brake. In this case, parking brake reset valve (22) is open and the air pressure from secondary air tank (16)is stopped at parking brake reset valve (22) .

When parking brake reset valve (22) is in the open position, parking brake reset valve (22) stops the flow of air toparking and secondary brake valve (17) . The parking brakes are applied by springs and the parking brakes are

released by pressure. When the air flow to parking and secondary brake valve (17) is blocked, the oil pressure to thebrake housing will be blocked and the springs will apply the parking brakes.

The Parking Brake Control Valve Is In The ON Position


The engine is operating. The parking brake reset valve is closed. The parking brake control valve is in the ON position. The secondarybrake air control valve is in the OFF position.





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Note: Secondary brake and parking brake pressure switch (18) is activated when parking brake air control valve(19) is in the ON position.

Air pressure from secondary air tank (16) flows to the secondary brake air control valve (20) and secondary brakeinverter valve (21) . With secondary brake air control valve (20) in the OFF position, air pressure from the

secondary air tank (16) flows through the parking brake reset valve (22) and the secondary brake inverter valve (21)to air control valve (19) for the parking brake.

When air control valve (19) for the parking brake is in the ON position and parking brake reset valve (22) is closed,air control valve (19) for the parking brake stops the flow of air to parking and secondary brake valve (17) . Theparking brakes are applied by springs and the parking brakes are released by pressure. When the air flow to parkingand secondary brake valve (17) is blocked, the oil pressure to the brake housing will be blocked and the springs willapply the parking brakes.

The Secondary Brake Air Control Valve Is In The ON Position.


(18) Secondary brake and parking brake switch








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Note: Secondary brake and parking brake pressure switch (18) is activated when the secondary brake air controlvalve is in the ON position.


The engine is operating. The parking brake reset valve is closed. The parking brake control valve is in the OFF position. The secondarybrake air control valve is in the ON position.



(18) Secondary brake and parking brake pressure switch








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Air pressure from secondary air tank (16) flows to the secondary brake air control valve (20) and through theparking brake reset valve (22) to the secondary brake inverter valve (21) . When the pedal for secondary brake aircontrol valve (20) is partially depressed to the ON position, a portion of the full supply pressure is sent to thecontrol passage of the secondary brake inverter valve (21) . Secondary brake inverter valve (21) will block some ofthe air pressure that is flowing to the parking and secondary brake valve (17) . The result is modulated secondarybraking action.

When the pedal on secondary brake air control valve (20) is held in the full ON position, air pressure from

secondary air tank (16) flows through the secondary brake air control valve to the control passage of the secondarybrake inverter valve (21) . The secondary brake inverter valve blocks all of the air pressure that was flowing to theparking and secondary brake valve (17) . The parking brakes are applied by springs and the parking brakes arereleased by pressure. When the air flow to parking and secondary brake valve (17) is blocked, the oil pressure to thebrake housing will be blocked and the springs will apply the parking brakes.

When you release the pedal for the secondary brake air control valve (20) , the pedal is returned by a spring to theOFF position. When the secondary brake valve is in the OFF position, air is not sent to the control passage of thesecondary brake inverter valve (21) . Secondary brake inverter valve (21) allows air pressure from secondary airtank (16) to flow to parking and secondary brake valve (17) . This air flow will cause parking and secondary brakecontrol valve (17) to send oil to the brake housing. The oil pressure will release the parking brakes.

The Service Brake Air Control Valve Is In The ON Position




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The engine is operating. The parking brake reset valve is closed. The parking brake control valve is in the OFF position. The secondarybrake air control valve is in the OFF position. The service brake air control valve is in the ON position.




(23) Brake air relay valve

(24) Cooling diverter solenoid

(25) Double check valve

(26) Front brake cooling diverter valve

(27) Service brake air control valve

(28) Front brake master cylinders

(29) Rear brake master cylinders




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Note: The darkened lines show air pressure and the arrows show the direction of air flow.

Note: Secondary brake and parking brake pressure switch (18) is deactivated when the parking brake control valveand the secondary brake air control valve are in the OFF position. The parking brakes are released.

When the pedal on service brake air control valve (27) is pushed down, air pressure from primary air tank (2) flowsthrough service brake air control valve (27) . Air pressure flows through double check valve (25) to the controlpassage of brake air relay valve (23) . This allows supply air from primary air tank (2) to flow through brake air

relay valve (23) to front brake master cylinders (28) and to rear brake master cylinders (29) . Oil pressure from thebrake master cylinders flows to the wheel brakes. The oil pressure activates the brakes.

The brake ECM energizes cooling diverter solenoid (24) when the service brakes are applied. Air is supplied tocooling diverter solenoid (24) from secondary air tank (16) . Air is then sent to front brake cooling diverter valve(26) . Air pressure at front brake cooling diverter valve (26) causes oil to flow through the front brake oil cooler.

When the pressure on the pedal of service brake air control valve (27) is released, the flow of air through servicebrake air control valve (27) is blocked. Air pressure between the control passages of brake air relay valve (23) andservice brake air control valve (27) flows outward through an exhaust passage in service brake air control valve(27) . The air pressure between brake air relay valve (23) and the brake master cylinders flows outward through an

exhaust passage in the brake air relay valve (23) . The oil pressure that had applied the brakes returns to the brakemaster cylinders as the pistons are drawn up by the spring in the brake master cylinders.

When the air pressure to the control passage of diverter valve (26) is blocked, the oil bypasses the front brake oilcooler.

The Retarder Air Control Valve Is In The ON Position




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The engine is operating. The parking brake reset valve is closed. The parking brake control valve is in the OFF position. The secondarybrake air control valve is in the OFF position. The retarder air control valve is in the ON position.




(23) Brake air relay valve

(24) Cooling diverter solenoid

(25) Double check valve

(26) Front brake cooling diverter valve

(28) Front brake master cylinders

(29) Rear brake master cylinders

(30) Retarder air control valve




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Note: Secondary brake and parking brake pressure switch (18) is deactivated when the parking brake control valveand the secondary brake air control valve are in the OFF position. The parking brakes are released.

When the lever for retarder air control valve (30) is in the ON position, air pressure from primary air tank (2) flowsthrough retarder air control valve (30) and through double check valve (25) . Air pressure flows through doublecheck valve (25) to the control passage of brake air relay valve (23) . This allows supply air from primary air tank

(2) to flow through brake air relay valve (23) to front brake master cylinders (28) and to rear brake master cylinders(29) . Oil pressure from the brake master cylinders flows to the wheel brakes. The oil pressure activates the brakes.The engine speed must be kept between 1500 rpm and 1900 rpm in order to keep the oil to the brakes cool.

The pressure of the air to the brake master cylinders is determined by the position of the lever for the retarder air

control valve. When the lever is completely pulled down, the maximum amount of retarding is achieved.

When retarder air control valve (30) is in the OFF position, the flow of air through retarder air control valve (30) isblocked. Air pressure between the control passages of brake air relay valve (23) and retarder air control valve (30)flows outward through an exhaust passage in retarder air control valve (30) . The air pressure between brake airrelay valve (23) and the brake master cylinders flows outward through an exhaust passage in the brake air relayvalve (23) . The oil pressure that had applied the brakes returns to the brake master cylinders as the pistons aredrawn up by the spring in the brake master cylinders.

NOTICE

Do not increase speed while the retarder is ON.

Copyright 1993 - 2008 Caterpillar Inc.Todos los derechos reservados.Red privada para licenciados del SIS.

Wed Mar 12 14:03:59 EST 2008


12/03/2008htt // i t / i b/ i b/t hd /t hd i t j ? t l / i b/ i b/ d t
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Sistema de Frenos de Aire 793D

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