COMPRESSED AIR SYSTEM This chapter contains general information about the brake and air suspension systems. For a more detailed description of brakes

Transcription

1 Contents COMPRESSED AIR SYSTEM... 2 Compressed air... 2 Compressor... 2 Air dryer... 3 Couplings... 3 Charging compressed air... 4 BRAKE SYSTEM... 5 Configuration... 5 Modification... 5 Manual control valve with test position... 5 ABS... 6 TC (Traction Control)... 7 The eight main components of the ABS/TC system... 8 TC operation in brief... 9 TC off-road... 9 ELC (Electronic Level Control) TAG AXLE Load transfer CONTROL BOX Programming M1 and M Extra control box CHASSIS HEIGHT Front Rear Tyres

2 COMPRESSED AIR SYSTEM This chapter contains general information about the brake and air suspension systems. For a more detailed description of brakes and air suspension, please refer to the Scania workshop manual. Compressed air The guaranteed pressure is 8 bar. The air tanks may be located transversely inside the frame right at the rear or next to the battery shelf, depending on vehicle type and wheel configuration. The current location is shown on the maim dimension drawings. Compressor The compressor has a swept volume of 600 cc, ensuring that charging time is short. The compressor has an ESS ( Energy Saving System ) relief mechanism that reduces the compressor s no-load power requirement by about 800 W. Relief pressure: With extra air tanks (load handling) Control range Without extra air tanks Control range 12.2 ± 0.2 bar bar 9.3 ± 0.2 bar bar 2

3 Air dryer The air dryer has integrated heating to prevent freezing (engaged at +7). Capacity 800 litres/min. Drying performance is more than adequate to cope with extra tank capacities for cargo handling, trailers, etc. Couplings The compressed air hoses have unions with seals of O-ring type. NOTE: If the hoses are to be disconnected from a component, the coupling must be unscrewed. The hose cannot be simply pulled out of the union. When changing unions on a hose the old ones must be scrapped and new ones fitted instead. If it is necessary to fit new unions or hoses, they can be purchased from the Scania spare parts department which also has a special tool for fitting unions on plastic pipes. Part no Connecting extra air consuming equipment. Connection of all extra compressed air equipment must always be carried out after the four-circuit protection valve at manifold fitting 65. Manifold fitting 65 can be found at several places on the vehicle but the most easily accessible ones are on the right-hand frame side member and rear crossmember. Place for extra solenoid valves can be found on the solenoid valve holder, located on one of the crossmembers beside the bogie / rear axle. Valves and couplings can be purchased from Scania distributors. 3

4 Charging compressed air The air dryer can be charged with air directly from an external compressed air system through the union located beside the left-hand boarding step. An air union on the dashboard under the parking brake control can be used for charging the parking brake circuit with air in connection with towing, etc. Consult the driver s manual for a description of how air can be filled from the front wheel Note: If the truck has an air dryer, air must only be filled via this air dryer in order to ensure that the new air is dried. 4

5 BRAKE SYSTEM Configuration The system has four circuits; service brake front and rear, parking brake/trailer brake circuit and a circuit for optional equipment. The circuits are internally protected by a four-circuit protection valve located beside the air dryer. If any of the circuits suffers an abnormal drop in pressure, supply is shut off to this circuit and the valve provides reduced pressure to the remaining circuits. All extra equipment should be coupled after the four-circuit protection valve. Parking and trailer components are assembled in a central valve package on the left-hand side of the frame. The relay valves are assembled in a package on the inside of the frame beside the rear axle. In order to facilitate removal of the cab, cab brake equipment and the central valve package are connected with two pairs of block couplings. Modification Modification of the brake system, for example after retrofitting additional tag axles, must always be carried out by Scania s service works. Manual control valve with test position 1. Drive position Emergency brake position. Between positions 1 and 2, air is bled from the lines to the spring brake chambers and the brakes are applied in proportion to how far the lever is moved towards position 2. If the vehicle has a trailer brake circuit, the trailer brakes are also applied Parking position. 4. Test position. The lever is pressed down, pulled back and held in this position. The function is then the same as for the parking position except that the trailer brakes are released when the line to the trailer relay valve is again pressurized. The purpose of this is to check that the vehicle parking brake alone is capable of holding the entire vehicle combination if the trailer brakes fail. When the lever is released it springs back to the parking position b : a 5

6 ABS ABS stands for Anti-lock Braking System. Optimum braking characteristics are achieved if both the trailer and tractor unit are equipped with ABS. If one part of the combination does not have ABS, it will brake as normally with the risk of wheel-lock. ABS ABS 26:1005 The four main components of the ABS system. (four-circuit system) ABS control valve, two front and two rear.* 2 Electronic control unit, ABS. 3 Toothed ring, two front and two rear. * 4 Wheel sensor, two front and two rear.* *Six-circuit systems have four at the rear. The toothed ring ( 3 ) is located on the wheel hub. The electromagnetic wheel sensor ( 4 ) is located on the axle and senses wheel rotation. The control unit ( 2 ), with the aid of the wheel sensors, senses whether one of the wheels is about to lock and then sends a signal to that wheel s control valve ( 1 ) which reduces brake pressure sufficiently to stop the wheel locking :1007 6

7 TC (Traction Control) Traction control prevents the driven wheels from spinning when acceleration is too fierce. TC works in combination with the ABS and uses the same sensors. 7

8 The eight main components of the ABS/TC system (four-circuit system). 1 ABS control valve, two front and two rear.* 2 Control unit. 3 Toothed ring, two front and two rear. * 4 Wheel sensor, two front and two rear.* 5 Solenoid valve (TC brake control), one unit for the driven wheel pair. 6 Double check valve, one unit for the driven wheel pair. 7 Relay valve, one unit for the driven wheel pair. 8 EDC control unit (electronically controlled fuel injection), for TC engine control. *Six-circuit systems have four at the rear. 8

9 TC operation in brief With ABS, the control unit registers signals from the sensors about the tendency of the wheels to lock. With TC, signals concerning whether the wheels are about to spin are also registered (one or two wheels show an abnormal increases in speed). Traction control has two control circuits. - Brake control - Engine control Brake control The brake control circuit is active up to a maximum of 40 km/h and is activated when a driven wheel spins. The TC brake control applies the brake to the spinning wheel and therefore basically functions as an automatic differential brake. Engine control Engine control is active at all speeds and is engaged when both driven wheels are spinning at the same speed. It is also engaged when one wheel is spinning and vehicle speed is greater than 40 km/h. Engine control limits the supply of fuel to the engine, via the EDC control unit, until the average speed of the driven wheels, when compared to vehicle road speed, is within the programmed range. Note: Malfunctions may arise if the difference in tyre sizes between the front and rear axles is too great. See the work description in the Workshop Manual. TC off-road With the TC off-road switch activated, the spin limit is increased by 10 km/h + 6 % of the normal programmed value. This means that the driven wheels can have a comparatively higher speed than the front wheels. 9

10 ELC (Electronic Level Control) Brief description. Electronic Level Control (ELC) is electronic control of the air suspension level control. Some advantages: - Constant height when loading and unloading, irrespective of chassis height. - Two chassis heights, such as for two the heights of two loading bays, can be programmed in the control unit. - Load transfer on vehicles with liftable tag axle. Driving Drive level is obtained by pressing the drive level button on the control box. Only in exceptional circumstances may the vehicle be driven at a height other than drive level. When driving with snow chains, the chassis should be raised about 65 mm. Calibration When a control unit or level sensor has been changed, drive level, upper max. level and the lower mechanical stop must be calibrated in the control unit. Adjusting programmed parameters for tipper trucks, etc. On tipper trucks and trucks with a crane the air bellows should be emptied to gain increased stability. Scania service workshops can reprogram the air suspension control unit with a function called empty air bellows and fit a switch for activating this function. Other alterations to the control unit can also be carried out for better adaptation to customer requirements. For chassis heights, see page 14. Always use axle stands when working under vehicles with air suspension. 10

11 TAG AXLE Operating the tag axle. With the switch in its lower position, the tag axle is lowered. Tag axle lowered With the switch in its middle position, the tag axle is raised. Tag axle raised Load transfer With the switch in its upper position, the load transfer is requested. Load transfer is used to temporarily obtain increased weight on the driven axle. Two ways to activate load transfer: 1 With a spring-back upper position, the tag axle bellows are vented for 90 seconds. 2 Spring-back position and unlimited time. Load transfer The regulations concerning maximum permitted rear axle weight and load transfer vary between different countries. The pressure monitors and switches should be selected to ensure that operation complies with the local regulations. 11

12 CONTROL BOX The control box is used to adjust chassis height to the desired level. The microprocessor in the box communicates with the control unit via digital signals. Features: 1 Raising/lowering, front. 2 Raising/lowering, rear. 3 Not used. 4 M1 memory for selectable chassis height. Must be used in combination with button 1 or 2. 5 M2 memory for selectable chassis height. Must be used in combination with button 1 or 2. 6 Raising/lowering to normal drive level. Must be used in combination with button 1 and/or 2. 7 Raising. Must be used in combination with button 1 and/or 2. 8 Lowering. Must be used in combination with button 1 and/or 2. 9 STOP. Interrupts features 4-6 when they have started. STOP is used to activate the stand-by feature. This button can also be used when programming M1 and M

13 Programming M1 and M2 Any two chassis heights can be programmed in addition to the preprogrammed values. 1 Adjust chassis height to the desired level using the control box. 2 Press the STOP button when the chassis is at the correct level and keep it depressed while activating either M1 or M2. 3 The chassis height is now stored in the memory and the STOP button can be released. Stand-by feature The stand-by feature allows automatic level control to work for two hours after the starter power has been switched off. If the truck is equipped with the stand-by feature, it is activated by holding the STOP button depressed when switching off the starter power. The stand-by feature is not used in 4x2 and 6x4 without load transfer. Extra control box For connection, see chapter 11, electrical system. M1 M2 STOP 26:

14 CHASSIS HEIGHT If a more accurate calculation of chassis height is desired, a document on Scania s bodyworking home page describes how to calculate the height. Scania distributors can also provide information on the height of a chassis. Front Electronically controlled air suspension, ELC (Electronic Level Control) - Front Chassis Chassis height Front axle Dimension U Max. raised Max. lowered Comment 4x2 6x2 6x2*4 6x2/4 6x4 8x2/4 8x4*4 4x2 6x2 6x2*4 6x2/4 6x4 8x4*4 8x2 8x2*6 8x4 8x2 8x2*6 8x4 4x2 6x2 6x2*4 4x2 6x2 6x2*4 Normal AMA Normal AMA Normal AMA Normal AMA Low AMA Produced before February 2000 Low AMA Produced after February x2/4 Low AMA x2 Extra low AMA U, measured from top of frame to ground at front axle centre or centre between front axles, for chassis weight with 295/80R22.5 tyres. 14

15 Leaf spring suspension - Front Front axle Suspension Dimension U with axle weight kg Dimension U with axle weight kg AM620/621 2x x x AM740 2x x x AM860 2x x AM820/920 2x x x x AM900 2x x x x AMD900 2x x U, measured from top of frame to ground at front axle centre or centre between front axles, at different loads with 295/80R22.5 tyres. 15

16 Rear Mechanically controlled air suspension - Rear Chassis Chassis height Rear axle Dimension V Max. raised Max. lowered Comment 4x2 Normal ADA1100/ x2 Low ADA1100/ Produced before February x2 Low ADA1100/ Produced after February 2000 V, measured from top of frame to ground at centre of rear axle, for chassis weight with 295/80R22.5 tyres. Electronically controlled air suspension, ELC (Electronic Level Control) - Rear Chassis Chassis height Rear axle Dimension V Max. raised Max. lowered Comment 4x2 Normal ADA1100/ x2 6x2*4 8x2 8x2*6 4x2 Normal ADA1500P x2 6x2*4 8x2 8x2*6 6x4 Normal ADA1100/ x4 8x4*4 6x2/4 Normal ADA1100/ x2/4 8x2/4 Normal ADA1500P x2 6x2 6x2*4 4x2 6x2 6x2*4 Low ADA1100/ Produced before February 2000 Low ADA1100/ Produced after February x2/4 Low ADA1100/ x2 Extra low ADA1100/ V, measured from top of frame to ground at centre of rear axle (driving axle) or bogie, for chassis weight with 295/80R22.5 tyres. 16

17 Leaf spring suspension - Rear 4x2 Suspension Dimension V with axle weight kg Dimension V with axle weight kg V, measured from top of frame to ground at centre of rear axle at different loads with 295/80R22.5 tyres. Leaf spring suspension - Rear 6x2, 8x2 V, measured from top of frame to ground at centre of driving axle at different loads with 295/80R22.5 tyres. Comment 3x26+2x With AM900 add 78 mm 7x15+6x x15+6x x15+6x Suspension Dimension V with bogie weight kg Dimension V with bogie weight kg Comment 5x For ad 3100 reduce by 30 mm 1x15+10x For ad 3100 reduce by 30 mm 17

18 Leaf spring suspension - Rear 6x4, 8x4 Boogie Suspension Dimension V with bogie weight kg BT200B BT200I BT201B BT201I BT300B H/E V, measured from top of frame to ground at centre of bogie at different loads with 295/80R22.5 tyres. Dimension V with bogie weight kg 4x x x x x x x20/ x x x20/ x20/ x25/ x20/ x20/ Leaf spring suspension - Rear 4x4 Suspension Dimension V with axle weight kg Dimension V with axle weight kg 3x26+2x x15+6x V, measured from top of frame to ground at centre of rear axle at different loads with 295/80R22.5 tyres. 18

19 Leaf spring suspension - Rear 6x6 Boogie Suspension Dimension V with bogie weight 5000 kg BT300I V, measured from top of frame to ground at centre of bogie at different loads with 295/80R22.5 tyres. Tyres For tyres other than 295/80R22.5 the chassis height changes. Adjust the height with the value obtained from the table below. For more accurate calculation of chassis height a calculation should be performed according to the height document that will be found on Scania s bodyworking home page. Tyres Dimension 295/60R /60R /60R /65R /70R /70R /70R /80R /80R R R R R R R R24 80 Dimension V with bogie weight kg 4x x20/ x25/