Steering -- Basic Knowledge -- 215 & 220 Chassis: Other Mercedes-Benz Pullman W221

Steering wheel heater (LRH), function - GF46.11-P-0001M

MODEL 220.025 /026 /028 /063 /065 /067 /070 /073 /074 /075 /083 /084 /087 /125 /126 /128 /165 /167 /170 /173 /174 /175 /176 /178 /183 /184 /187 /874 /875 /876 /878 with CODE (443) Steering wheel heater

MODEL 215.373 /374 /375 /376 /378 with CODE (443) Steering wheel heater

Shown on Model 220

Identifying Steering Column Module, EIS Control Module - Shown On Model 220. Scheme 30

Operation

Using the steering wheel heater the steering wheel can be heated up to make finger contact more comfortable and safer at low outside temperatures.

The steering wheel heater is switched on and off by a rotary function of the steering wheel heater switch. The position of the steering wheel heater switch is read out by the electronics in the steering column module (N80) and placed on CAN class B.

There are 3 positions for the steering wheel heater switch

1. Center position
2. Turning upwards
3. Turning downwards

A red function LED to display function is integrated in the steering wheel heater switch. The function display is switched off in the event of a defect in the steering wheel heater.

The DC/DC converter control module (N99) directs voltage to the steering wheel heater electronics fitted in the steering wheel. This energizes the heating coils in the steering wheel in order to heat up the steering wheel and regulates the steering wheel heater to the target temperature of approx. 28 °C at the steering wheel surface.

The information as to whether heating or an internal diagnosis (steering wheel self check) should be carried out is conveyed to the steering wheel heater electronics by means of a different voltage level at its inlet.

Tasks of steering wheel heater electronics

1. To energize the heating coil in the steering wheel
2. To measure the surface temperature of the steering wheel rim via the integrated temperature sensor
3. To carry out diagnosis for the heating coil and temperature sensor in the steering wheel rim

Two power settings are possible

1. To heat with minimum power (voltage supply 42 V)
2. To heat with maximum power (voltage supply 48 V)

It is necessary to increase the voltage from 12 V to 42 V or 48 V so that the steering wheel heater can be supplied with a power of approx. 100 W

Scheme 31

To enable rapid heating up the heating coil is supplied with 48 V when it is switched on.

The time is limited to 7 minutes to prevent it from overheating. After this the heating coil is supplied with minimum power (voltage supply 42 V).

The maximum permanent heating time is 24 minutes. The heating coil is switched off after this.

The system is controlled and monitored by the DC/DC converter control module (N99).

The interior temperature is reported to the DC/DC converter control module (N99) by the overhead control panel control module (N70) via the CAN class B. The DC/DC converter control module (N99) evaluates the interior temperature signal to protect the heating coil.

Identifying Steering Wheel Heater Switch Location - Shown On Model 220. Scheme 32

Shown on Model 220

Switching steering wheel heater (LRH) on/off, function - GF46.11-P-1001M

MODEL 220.025 /026 /028 /063 /065 /067 /070 /073 /074 /075 /083 /084 /087 /125 /126 /128 /165 /167 /170 /173 /174 /175 /176 /178 /183 /184 /187 /874 /875 /876 /878 with CODE (443) Steering wheel heater

MODEL 215.373 /374 /375 /376 /378 with CODE (443) Steering wheel heater

MODEL 230.467 /474 /475 with CODE (443) Steering wheel heater

Function requirements

1. 15R On or 15 ON from EIS control module (N73) via CAN class B.

Switch on steering wheel heater

The position of the steering wheel heater switch (S59/1s2) is read out by the electronics in the steering column module (N80) and placed on the CAN class B.

As long as the steering wheel heater switch (S59/1s2) is operated (turned upwards), the operated position is sent cyclically. The cycle time is t = 100 ms.

The center position of the steering wheel heater switch (S59/1s2) is not sent by the steering column module (N80).

The center position is recognized if within t = 3 cycles no message is sent from the steering wheel heater switch(S59/1s2) or if the two corresponding bits for the rotary operation of the steering wheel heater switch (S59/1s2) are not set.

The message for the actuation of the function LED (red) is placed cyclically on the CAN class B by the DC/DC converter control module (N99) and is read out by the steering column module (N80). This actuates the function LED integrated in the steering wheel heater switch (S59/1s2).

If the DC/DC converter control module (N99) receives the command "Steering wheel heating" , the steering wheel heater electronics (A74) fitted in the steering wheel are supplied with voltage which energizes the heating coil (R22/4r1).

In addition the steering wheel heater electronics (A74) measures the surface temperature of the steering wheel rim via a temperature sensor integrated in the steering wheel. If the temperature rises to above 28 °C, the energizing of the heating coil (R22/4r1) is interrupted. If the temperature drops below 24 °C (during the control) or below 26 °C (during a hot start), the heating coil (R22/4r1) is energized again.

The interior temperature is reported by the overhead control panel control module (N70) via the CAN class B and is evaluated in the DC/DC converter control module (N99) in order to protect the heater coil (R22/4r1). At interior temperatures above 30 °C the steering wheel heater is switched off in order to prevent the heating coil (R22/4r1) from overheating.

Initially the steering wheel heater is operated with maximum power (voltage supply 48 V) in order to achieve adequate heating up of the steering wheel. After t = 7 minutes the steering wheel heater is operated with reduced power (voltage supply 42 V) in order to prevent the heating coil (R22/4r1) from overheating.

Only a limited current of approx. 2 A can be supplied via the heating coil (R22/4r1). The voltage transformation is necessary in order to realize steering wheel heating with a power of approx. 100 W.

Finishing steering wheel heating

The heating mode of the steering wheel heater is finished manually by turning the steering wheel heater switch (S59/1s2) downwards. The steering wheel heater is switched off automatically when a continuous heating mode over a period of 24 minutes is detected by the DC/DC converter control module (N99) or one of the following shutoff conditions occurs

1. Switching off after ignition circuit 15R OFF The steering wheel heater also switches off once circuit 15R is switched off. However, the time control continues on for t = 5 minutes for as long as circuit 15 is "ON". If circuit 15R is switched on again, the steering wheel heater is switched on again with the output voltage existing before it was switched off. The timer (t = 7 minutes) for the reduced heating voltage of 42 V is not reset.
2. Switching off in the event of undervoltage (< 11 V) or overvoltage (> 16 V) The steering wheel heater is switched off if undervoltage or overvoltage is detected. The function LED flashes. The timer (t = 7 minutes) for the reduced heating voltage of 42 V is not reset. If the voltage is in the normal range again, the steering wheel heater switches on again with the output voltage existing before it was switched off. The function LED comes on again accordingly.
3. Switching off while the engine is being started The steering wheel heater is switched off while starting the engine. The function LED remains switched on. The timer (t = 7 minutes) for the reduced heating voltage of 42 V is not reset. Once the engine has been started the steering wheel heater switches on again with the output voltage existing before it was switched off.
4. Switching off when steering column adjustment is active The steering wheel heater is switched off during active steering column adjustment. The function display remains switched on. The timer (t = 7 minutes) for the reduced heating voltage of 42 V is not reset. Once the steering column is adjusted, the steering wheel heater only switches on again after t = 5 seconds with the output voltage existing before it was switched off. However, if the timer (t = 7 minutes) for the reduced heating voltage of 42 V has come to an end, the system switches to the output voltage of 42 V with a stop condition following it.
5. Switching off if the DC/DC converter control module overheats (N99) The DC/DC converter control module (N99) has its own safety shutoff, the steering wheel heater being switched off at a temperature of > 10 of 193 95 °C in the DC/DC converter control module (N99).

Survey of system components of steering wheel heater (LRH) - GF46.11-P-9999M

MODEL 220.025 /026 /028 /063 /065 /067 /070 /073 /074 /075 /083 /084 /087 /125 /126 /128 /165 /167 /170 /173 /174 /175 /176 /178 /183 /184 /187 /874 /875 /876 /878 with CODE (443) Steering wheel heater

MODEL 215.373 /374 /375 /376 /378 with CODE (443) Steering wheel heater

Electrically-adjustable steering column (EVL), function - GF46.15-P-0003S

MODEL 215, 220

Electrically-Adjustable Steering Column (EVL) Function Diagram. Scheme 33

Block diagram

Electrically-adjustable steering column

(shown on left-hand steering)

Electrically-adjustable steering column

The position of the steering column is electrically adjustable manually using the switch in the steering column adjustment and entrance/exit aid switch group (S59/1) in the jacket tube module (N80)

1. The fore/aft position of the steering column, max. adjustment travel 60 mm
2. The tilt of the steering column, max. adjustment travel 31 mm (+ 7 mm when approaching the entrance/exit position) can each be adjusted separately.

The fore/aft adjustment has one adjusting speed, the tilt position adjustment has two adjusting speeds.

With the memory function the steering column positions can also be stored in addition to the driver's seat/interior rearview/exterior rearview mirror adjustments. The stored positions are approached automatically when the respective memory button in the left front door control module (N69/1)(right-hand steering: front right door control module (N69/2) is pressed. The steering column adjustment motor group (M20) is actuated in parallel.

The entrance/exit aid function makes it easier for the driver to get in and out with the steering column raised upwards.

Adjusting steering column function - GF46.15-P-2000S

MODEL 215, 220

Adjusting Steering Column Function Chart. Scheme 34

Shown on model 220

Functional prerequisites

1. No overvoltage or undervoltage and
2. Circuit 15c ON or
3. Circuit 15R ON or
4. Circuit 15 ON or
5. Driver's door open or
6. Front passenger's door open
7. No blocking recognized
8. Steering column in standardized condition

Manual adjustment

When the switches of the steering column adjustment and entrance/exit aid switch group (S59/1) are operated, this is read in by the jacket tube module (N80) and from there placed on the CAN bus as a message. The left front SAM control module (N10/6) receives this message and actuates the telescopic adjustment motor (in/out) (M20m1) and tilt adjustment motor (in/out) (M20m2) via the left front fuse and relay module (K40/6) as long as the switch is operated.

Automatic adjustment with memory function (special equipment)

When one of the memory buttons or the "Ergo" button in the left front door control module (N69/1) (right-hand steering: front right door control module (N69/2) is pressed the corresponding steering column positions are also approached in addition to the stored driver's seat position and associated settings of the interior rearview and exterior rearview mirrors. For this a CAN message is sent to the left front SAM control module (N10/6) . This control module then actuates the motors (M20m1, M20m2) via the door control module.

Entrance/exit aid

When the entrance/exit aid function is called up the steering wheel is moved to the uppermost position, making it easier for the driver to get in and out.

Emergency running function

If the Hall sensors in the motors (M20m1, M20m2) are defective or if normalizing is defective the emergency running function enables the steering column to be moved into the driving position manually (airbag safety range).

Steering column drive position recognition microswitch position/task/design/function - GF46.15-P-4102S

MODEL 215, 220

Steering column drive position recognition microswitch position - GF46.15-P-4102-01S

The microswitch for steering column driving position (M20s1) is located on the steering column.

Identifying Drive Pinion, Thrust Piece (Spring-Loaded) And Gear Rack. Scheme 35

Rack-and-pinion steering gear, function - GF46.20-P-1000-01B

Models 215, 220, 230

The drive pinion (4b) transmits the movement of the steering wheel to the gear rack (7) and then via the tie rods to the wheels.

The drive pinion has spiral splines. Because a number of teeth are always meshed at the same time, the rack-and-pinion steering is resistant to wear and has a very low noise level.

Identifying Rack-And-Pinion Steering Damper Components. Scheme 36

Steering gear ratio and gear teeth

The variable steering gear ratio is achieved by means of the effective diameters (d1 and d2) resulting from the shape and angles of the gear teeth.

In the central area (X) the gear rack is indirect. The rack-and-pinion steering becomes increasingly direct in the outside areas (Y).

Identifying Perforated Disk. Scheme 37

The difference between the gear ratio in the central area (X) and the gear ratio in the outside area (Y) amounts to approx. 30 %.

Identifying Difference Between Central And Outer Area Gear Ratio. Scheme 38

Rack-and-pinion steering damper, function - GF46.20-P-1200-02A

Models 171.4, 203, 209, 215, 220, 230

Illustrated steering left

Identifying Rack-And-Pinion Steering Damper Components - Models 171.4, 203, 209, 215, 220, 230. Scheme 39

Identifying Perforated Disk. Scheme 40

Pressurized steering damper (I)

The high-pressure oil passes unrestricted through 4 holes in the perforated disk (5b) and past the return plate (5a) against the force of the return spring (5c) to one of the working cylinders.

Dampened return pressure (II)

The oil flowing from the opposite working cylinder is forced through 4 other holes in the perforated disk (5b). This pushes up the disk spring (5d) and pumps the oil into the return line. This restricted pressure provides the required damping effect.

Rack-and-pinion steering straight-ahead driving function - GF46.25-P-3100B

MODEL 171.4, 203, 209, 211 with CODE (213a) Speed-sensitive power steering

MODELS 215, 220, 230

Shown on model 220

Rack-And-Pinion Steering Straight-Ahead Driving Function Diagram - Shown On Model 220. Scheme 41

The rotary valve is composed of the rotary slide (4k) with 6 control grooves with ground edges on its jacket surface, and the pilot bushing (4i) also with 6 control grooves corresponding to those on the rotary slide (4k).

One end of the torsion bar (4a) is pinned to the rotary slide (4k), and the other end to the drive pinion (4b). It holds the rotary slide (4k) in the neutral position when the steering wheel is not turned.

Rack-and-pinion steering, function when steering - GF46.25-P-3400A

MODEL 171.4, 203, 209, 211 with CODE (213a) Speed-sensitive power steering

MODELS 215, 220, 230

Rack-And-Pinion Steering, Function Diagram (Illustrated On Model 220, Left Wheel Lock). Scheme 42

Illustrated on model 220, left wheel lock

Rack-And-Pinion Steering, Function Diagram (Illustrated On Model 220, Right Wheel Lock). Scheme 43

Illustrated on model 220, right wheel lock

When the steering wheel is turned, the drive pinion (4b) rests on the rack (4j). The rotary slide (4k) is twisted against the surrounding pilot bushing (4i) by the torsion bar (4a), thus changing the relative positions of the control grooves. The high-pressure oil stream passes into the right working cylinder (left wheel lock) (I) or into the left working cylinder (right wheel lock) (II), causing the axial movement of the rack (4j) to the right or left.

The oil from the unpressurized working cylinder is displaced. It flows through the open return grooves in the pilot bushing (4i) back to the supply reservoir of the power steering pump.

Power steering pump, function - GF46.30-P-2100-01B

Models 203, 209, 211

Models 220, 230 except Code (487a)

Active Body Control (ABC)

Identification of power steering pump manufacturers

Models 220, 230

LF 30 = LuK Clutch and Transmission Systems

FP 42 = ZF (Zahnradfabrik Friedrichshafen)

Models 203, 209, 211 with diesel engines

LF 37 = LuK Clutch and Transmission Systems

FP 42Q = ZF (Zahnradfabrik Friedrichshafen)

Models 203, 209, 211 with gasoline engines

LF 30 = LuK Clutch and Transmission Systems

FP 42 = ZF (Zahnradfabrik Friedrichshafen)

c Unpressurized

f Pressurized

A To steering gear

B From supply reservoir

Section View Of Power Steering Pump. Scheme 44

Basic function

The rotation of the drive shaft, and thus of the rotor, produces a centrifugal force which presses the blades on the rotor in the radial direction against the running surface of the non-moving cam insert. This is assisted by hydraulic oil, which travels from the pressure chamber via bores and grooves and against the internal end faces of the blades. Ten closed pump cells are thus formed between the ten blades of the rotor.

As the volume increases, oil is drawn up from the supply reservoir (B); as the volume decreases, oil is forced into the pressure chamber (A). Because the shape of the cam insert means that two suction and two pressure zones are opposite each other, each of the ten pump cells pumps twice its own volume for each rotation of the drive shaft.

Furthermore, this double arrangement of suction and pressure zones causes the radial hydraulic forces acting on the rotor to cancel each other out.

(Scheme 30) Quantity control valve (30t) open

Power Steering Pump, Function Diagram - Quantity Control Valve (30T) Open. Scheme 45

(Scheme 31) Quantity control valve (30t) closed

Power Steering Pump, Function Diagram - Quantity Control Valve (30T) Closed. Scheme 46

Oil volume regulation

The power steering pump is driven by the engine at alternating speeds. Power assistance however requires a constant oil flow. As more oil than is necessary is pumped at higher engine speeds, the surplus oil is fed back to the supply reservoir via the open quantity control valve (30t).

The quantity control valve (30t) thus ensures that the steering gear is supplied with a constant oil stream across the entire engine speed range.

Scheme 47

1. Engine ON, steering wheel not turned: The pressure oil produced by the rotor cells is fed via the calibrated bore hole (9a) to the steering gear and also via the bore (9b) to the spring chamber downstream of the quantity control valve (30t). The calibrated bore holes (9a, 9b) throttle the oil stream so that the oil pressure in the spring chamber downstream of the quantity control valve (30t) is lower than on the side of the high-pressure chamber. The quantity control valve (30t) opens (Scheme 30) and the surplus pressure oil flows back to the supply reservoir.
2. Engine ON, steering wheel turned: Because of the rising pressure downstream of the restrictor orifice (a), the pressure downstream of the quantity control valve also rises. The quantity control valve (30t) closes (Scheme 31) and remains in its basic position.
3. High engine speed: If the oil quantity increases as the engine speed rises, a greater pressure difference again occurs due to the calibrated bore hole (9a). The quantity control valve (30t) is forced against the spring (30s) and the surplus oil can flow back to the supply reservoir (Scheme 30) see scheme 28: Power Steering Pump, Function Diagram - Quantity Control Valve (30t) Open

Quantity control valve (30t) open

Pressure limiting

A pressure limiting valve (49d) is installed in the quantity control valve (30t) to protect the steering system against overloading. It opens at a pressure between 65 and 125 bar depending on the model of power steering pump.

This occurs, for example, at full steering lock, and is audible as a high-pitched whirring whistle.

Arrangement of power steering pump - GF46.30-P-2100-02B

Model 220

The power steering pump (30) is attached to the front of the engine on the left side.

Identifying Power Steering Pump. Scheme 48

Tandem pump, design - GF46.30-P-3300-03A

MODEL 215

MODEL 220, 230 with CODE (487a)

Active body control (ABC)

Identifying Radial Piston Pump, Vane-Type Pump, Input Shaft And Sealing Ring. Scheme 49

The tandem pump consists of two pumps, each supplying one circuit. The pump facing the input shaft is a radial piston pump supplying the hydraulics of the active body control (ABC) system.

The rear pump is a vane-type pump supplying the hydraulics of the steering system. Both pumps are driven by a common input shaft (3) and are carried in common bearings. The hydraulic circuits are separated from each other by a sealing ring (4).

Tandem pump, function - GF46.30-P-3300-04A

MODEL 215

MODEL 220, 230 with CODE (487a)

Active body control (ABC)

Identifying Tandem Steering Pump Function. Scheme 50

The rotation of the drive shaft, and thus of the rotor, produces a centrifugal force which presses the blades on the rotor in the radial direction against the running surface of the non-moving cam ring. This is assisted by hydraulic oil, which travels from the pressure chamber via bores and grooves and against the internal end faces of the blades. Ten closed pump cells are thus formed between the ten blades of the rotor.

As the volume increases, oil is drawn up from the supply reservoir (B); as the volume decreases, oil is forced into the pressure chamber (A).

Because the shape of the cam ring means that two suction and two pressure zones are opposite each other, each of the ten pump cells pumps twice its own volume for each rotation of the drive shaft.

Furthermore, this double arrangement of suction and pressure zones causes the radial hydraulic forces acting on the rotor to cancel each other out.

Identifying Pressure And Flow Valve (30) Open And Pressure Limiting Valve (30C) Open. Scheme 51

(Scheme 30): Pressure and flow valve (30) open, pressure limiting valve (30c) open

Identifying Rotary Valve And Control Bush Housing For Models 215 And 220, Left Wheel Lock. Scheme 52

(Scheme 31): Pressure and flow control valve (30) closed, pressure limiting valve (30c) closed

Oil volume regulation

The vane-type pump is driven by the engine at alternating speeds. Power assistance however requires a constant oil flow.

As more oil than is necessary is pumped at higher engine speeds, the surplus oil is fed back to the intake side of the vane-type pump via the infinitely variable opening of the pressure and flow control valve (30t).

The pressure and flow control valve (30) thus ensures that the steering gear is supplied with a constant oil stream across the entire engine speed range.

1. Engine ON, idle speed, steering wheel turned: The end face of the piston (30a) in the pressure and flow control valve (30) is subjected to the pressure oil generated by the vane-type pump. The opposite side of the piston (30a) is acted on by the spring pressure and also by a reduced oil pressure via the calibrated borehole (30b). In total, the pressure on the end face of the piston (30a) is greater than that on the opposite side. The pressure and flow control valve (30) opens and the surplus pressure oil flows back to the intake side of the vane-type pump (2) (Scheme 30)
2. Engine ON, steering wheel not turned: As the pressure on the end face of the piston (30a) falls, the pressure on the opposite side remains approximately the same, causing the pressure and flow control valve (30) to close. The oil pumped by the vane-type pump is directed in its entirety to the steering gear (Scheme 31)
3. High engine speed: As the engine speed rises, the pressure on the end face of the piston (30a) increases. This decreases the difference between the pressures acting on the end face and opposite side of the piston. The pressure and flow control valve (30) opens smoothly against the force of the spring. The surplus oil can flow to the intake side of the vane-type pump (Scheme 30)

Pressure limiting

A pressure limiting valve (30c) is installed in the pressure and flow control valve (30) to protect the steering system against overloading and to reduce pressure spikes in the system. It opens at approx.120 bar pressure (Scheme 30) This occurs e.g. at full steering lock, and is audible as a high-pitched whirring whistle.

Note. Some tandem pumps are equipped with a stub pipe. The purpose of this stub pipe is to allow for additional compensation of any pressure surges that may occur.

Tandem pump, function - GF46.30-P-3300-04B

MODEL 215

MODEL 220, 230 with CODE (487a)

Active body control (ABC)

Identifying Tandem Pump Function. Scheme 53

Identifying Rotary Valve Housing And Control Bush Housing, Models 215, 220 Right Wheel Lock. Scheme 54

Oil supply

The rotation of the input shaft (3) acting via the cam (3a) produces an oscillating stroke in the radially moving, spring-loaded pistons (A to G).

As the piston travels to the bottom dead center (pistons A to C) the increasing space in the piston chamber produces a vacuum. This causes the oil to enter through the bore (11) in the piston which connects the piston chamber just before the bottom dead center with the inlet side of the pump (piston D). On the power stroke the full cylinder chamber is sealed just before the bottom dead center when the bore (11) is covered (piston E). The oil is pumped to the system against the working pressure by means of the pressure diverter valve (12), one of which is assigned to each piston (pistons E to G).

Shortly after the top dead center no more oil is delivered to the system. The pressure diverter valve (12) closes due to the higher pressure of the spring (12a) overcoming the oil pressure in the piston chamber of the pump.

Lubricating oil is diverted via the calibrated boreholes (14a, 14b) to supply the input shaft bearings.

Oil volume regulation

An ABC suction restrictor valve (Y86/1) is integrated in the radial piston pump on the suction side. This can be used to provide infinitely variable adjustment of the volumetric flow rate of the radial piston pump. The basic characteristic of the radial piston pump is produced via the bores (11).

Pressure limiting

The pressure in the radial piston pump is limited in the active body control (ABC) system.

Scheme 55

Output and pressure testing of the tandem pump is not planned.

Speed-sensitive power steering (SPS), function - GF46.50-P-0001A

MODELS 203, 209, 211 with CODE (213a) Speed-sensitive power steering

MODELS 215, 220, 230

Identifying Speed-Sensitive Power Steering (SPS) Function - Models 203, 209, 211 With Code (213A) And 215, 220, 230. Scheme 56

Shown on steering gear model 220

Identifying Speed-Sensitive Power Steering (SPS), Function Diagram - Shown On Steering Gear Model 220. Scheme 57

The speed-sensitive power steering (SPS) gradually increases the manual effort required to turn the steering wheel from when the vehicle is stationary up to a speed of approximately 100 km/h.

When stationary, the steering assistance is similar to that of the hydraulic power steering (without SPS function).

The operating parameter is the vehicle speed, which with the aid of the electronic systems, adjusts the hydraulic reaction by means of the SPS solenoid valve (Y10) in the speed range from 0 to approx. 100 km/h to suit the requirements.

The electronic control system is integrated in the traction system control module (N47).

SPS electrically controlled centering, function - GF46.50-P-2400AA

MODELS 203, 209, 211 with CODE (213a) Speed-sensitive power steering

MODELS 215, 220, 230

Function

The electronic control system of the speed-sensitive power steering is integrated in the traction system control module (N47). A certain manual force (K) is set at the steering wheel according to the speed of the vehicle. As the speed of the vehicle increases, the manual effort (K) required to turn the steering increases at the steering wheel (up to 100 km/h).

The driving speed calculated by the traction system control module (N47) is assigned a nominal current in a characteristic map. This current is then set in the SPS solenoid valve (Y10) (proportional solenoid valve) and influences the oil flow (hydraulic reaction) within the rack-and-pinion steering, and thus the manual force (K) required at the steering wheel.

Manual Force Graph. Scheme 58

The actuation of the SPS solenoid valve (Y10) is pulsed. The current is regulated by pulse-width modulation of these pulses.

SPS Solenoid Valve Pulse-Width Graph. Scheme 59

Speed-sensitive power steering, function with vehicle stationary - GF46.50-P-2500A

MODEL 171.4, 203, 209, 211 with CODE (213a) Speed-sensitive power steering

MODELS 215, 220, 230

Illustration shows rotary valve and control bush housing for models 215 and 220, left wheel lock

Vehicle speed v = 0 km/h

The SPS solenoid valve (Y10) receives maximum current which closes it against the force of the integrated compression spring. The pressure ratios in the reaction chambers are identical, since the pressure oil supply is stopped. No force is exerted on the reaction balls (4) and no additional moment is produced on the v-shaped surfaces of the rotary valve (12).

The steering turns easily because the steering moment which the driver must apply to overcome the force of the torsion bar (10) is very low. The oil passes virtually unpressurized via the constant constriction orifice (8) to the supply reservoir of the power steering pump.

Speed-sensitive power steering at vehicle speeds 0-100 km/h when steering, function - GF46.50-P-2600A

MODEL 171.4, 203, 209, 211 with CODE (213a) Speed-sensitive power steering

MODELS 215, 220, 230

Shown: rotary valve housing and control bush housing, models 215, 220 left wheel lock

Identifying Rotary Valve Housing And Control Bush Housing, Models 215, 220 Left Wheel Lock. Scheme 60

Shown: rotary valve housing and control bush housing, models 215, 220 right wheel lock

As the vehicle speed increases, the energization of the SPS [PML] solenoid valve (Y10) decreases continuously; this is opened by the force of the integral push spring. The regulated pressure is transmitted via the control spool (9) to the reaction balls (4), which causes the pressure acting on the v-shaped surfaces of the rotary slide (12) to rise. The force on the torsion bar (10) is thus further increased and the driver must operate the steering wheel with a higher steering moment.

The constant constriction orifice (8) reduces the regulated pressure from the SPS solenoid valve (Y10). This is then passed on as an almost depressurized backflow to the power steering pump reservoir.

Speed-sensitive power steering at vehicle speeds >100 km/h when steering, function - GF46.50-P-2700A

MODEL 171.4, 203, 209, 211 with CODE (213a) Speed-sensitive power steering

MODELS 215, 220, 230

Rotary valve and control bush housing for models 215 and 220 illustrated Steering left

Scheme 61

Vehicle speed v --> 100 km/h

The SPS [PML] solenoid valve (Y10) is energized to the minimum extent. This causes the maximum possible pressure from the SPS solenoid valve (Y10) to be directed via the control spool (9) onto the reaction balls (4), increasing the pressure acting on the v-shaped surfaces of the rotary slide (12) to the maximum.

The constant constriction orifice (8) reduces the regulated pressure from the SPS solenoid valve (Y10). This is then passed on as an almost depressurized backflow to the power steering pump reservoir.

SPS solenoid valve, function - GF46.50-P-5000-01B

Model 203.0 as of 01.08.01

Models 203.2, 203.7

Models 209, 211, 215, 220, 230

SPS Solenoid Valve Function Graph - Models 203.0 As Of 01.08.01, 203.2, 203.7, 209, 211, 215, 220, 230. Scheme 62

SPS solenoid valve (Y10) open

Identifying SPS Solenoid Valve Open - Models 203.0 As Of 01.08.01, 203.2, 203.7, 209, 211, 215, 220, 230. Scheme 63

SPS solenoid valve (Y10) closed

Identifying SPS Solenoid Valve Closed - Models 203.0 As Of 01.08.01, 203.2, 203.7, 209, 211, 215, 220, 230. Scheme 64

The electronics for actuation of the SPS solenoid valve (Y10) are integrated in the traction system control module (N47). The SPS solenoid valve (Y10) is actuated in pulses. As the vehicle speed increases, the current flow decreases and the SPS solenoid valve (Y10) gradually opens the control valve according to a characteristic (K) defined in the traction system control module (N47).

This regulates the oil flow and thus the torque to be applied to the steering wheel. When the SPS solenoid valve (Y10) is actuated with the maximum current (v=0 km/h), the control valve is closed.

No oil flows and the minimum steering wheel torque is set (situation for parking).