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16 © Scania CV AB 1999, Sweden 1050f16b.mkr Hydraulic system, overview of later design Components in the hydraulic system 1 Stators 2 Rotor 3 Shaft 7 Oil pump 8 Sump 9 Filter 10 Control valve 11 Oil cooler 12 Chamber 13 Air ducts 14 Coolant oilway 15 Radial seals 16 Accumulator 17 Solenoid valve 18 Non-return restriction valve 19 Proportional valve 20 Solenoid valve 21 Bypass valve 22 Safety valve 23 Channel 24 Spring 20 19 18 16 17 11 12 2 7 13 24 8 23 22 21 9 14 1 3 15 10 25 1 1 5
  16  ©  Scania CV AB 1999, Sweden 1050f16b.mkr Hydraulic system, overview of later design Components in the hydraulic system1 Stators2 Rotor 3 Shaft 7 Oil pump8 Sump9 Filter 10 Control valve11 Oil cooler 12 Chamber 13 Air ducts14 Coolant oilway15 Radial seals16 Accumulator 17 Solenoid valve18 Non-return restriction valve19 Proportional valve20 Solenoid valve21 Bypass valve22 Safety valve23 Channel24 Spring 201918 161711122 71324823222191413 15 1025    1   1   5    4   2   5 327654 1 25 Cone Hydraulic system  1050f16b.mkr  ©  Scania CV AB 1999, Sweden 17New design of the proportional valve A new valve block, V97, is introduced in production from 9908 on trucks and from 9910 on buses. The functions for the following are incorporated into the valve block:ãProportional valve 19ãAir supply for solenoid valve (ON/OFF) 20ãSolenoid valve for oil accumulator 17 Note: The new valve block V97 requires a higher control frequency, 360 Hz. This frequency is available from control units manufactured from 9902. Otherwise, the system is not modified but works in the same way irrespective of valve design. Retarder There is an oil pump 7 on shaft 3 which receives oil from the sump 8, via the filter 9. From there, the oil is directed via the control valve 10, either to the rotor 2 for braking or to the oil cooler 11 for cooling in disengaged mode.There are two annular chambers 12 between the rotor 2 and the stators 1. When these are filled with oil, the rotor and the stators force the oil to change direction repeatedly. The flow of oil thus provides resistance to the rotor and counteracts its rotation.The oil flows extremely quickly and in a curved spiral path. Centrifugal force causes the oil in the chambers to accumulat on the periphery and attempt to escape. The oil is therefore retained in the chambers by back pressure from the outside. Higher pressure gives more oil in the chambers and higher brake torque.The chambers are connected to the sump via air ducts 13. These are necessary to enable the quantity of oil to be adjusted quickly when the driver wants to adjust the brake torque.The oil pump 7 rotates as soon as the vehicle is in motion. When braking, the oil is directed via the control valve to the rotor and the oil cooler. When the retarder is disengaged, most of the oil is directed via the control valve to the oil cooler and the sump. A small proportion is directed via the coolant oilway 14 for lubrication and cooling.Safety valve 22 is fitted with an additional sealing ring from chassis number SS1251239, SN4414949, SA9043610, SBK1835768.The retarder and gearbox oil systems are separated by two radial seals 15. Hydraulic system  18  ©  Scania CV AB 1999, Sweden 1050f16b.mkr Oil accumulator The accumulator 16 is emptied and quickly fills the retarder when braking begins. This is activated with compressed air from a solenoid valve 17. There is a non-return restriction valve 18 in the accumulator outlet.The left-hand position is the non-return valve position. The oil then passes both through the restriction and on the outside of the bushing. The non-return valve position is used both when emptying and refilling when the driver ceases braking. The right-hand position is the restriction valve position. The oil then passes only through the restriction. The restriction valve position is used when refilling the accumulator during braking. Oil cooler The oil cooler 11 transmits the heat from the retarder oil to the engine cooling system where the heat is finally dissipated by the vehicle's ordinary radiator. Proportional valve The supply air solenoid valve 20 and the proportional valve 19 are both actuated by the control unit. Unreduced air pressure is fed from solenoid valve 20 to the proportional valve 19.The control unit supplies a current, whose strength corresponds to the required brake torque, to the proportional valve. This then delivers air pressure to control valve 10 which creates the oil pressure necessary to achieve the required brake torque. Safety system See When the retarder is to stop braking, under Safety system Hydraulic system
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