Camshaft: Description and Operation

Camshaft Adjuster:

NOTE: Numbers in parentheses ( ) indicate a component or tool in the associated illustration.

Task Of Camshaft Adjuster
The task of the camshaft adjuster is to:
- educe the quantities of residual gas by creating smaller valve overlaps at idling speed and up to 1200 rpm ("retarded" position)
- Reduce unburned mixture losses at engine speeds of 1200-4300 rpm ("advanced" position)
- Improve the charge (boost effect) from an engine speed of 4300 ram Retarded position)





Function Of Camshaft Adjuster
When the engine is running, the camshaft adjuster (75) rotates the inlet camshaft (78) hydraulically/mechanically relative to the camshaft sprocket by 20° crank angle or 10° cam angle, respectively. toward the "advanced" position and back into the "retarded" position.
The camshaft adjuster is actuated electromagnetically by the control module.
The adjustment time of about 1 second is dependent on the engine oil pressure at the camshaft adjuster and the oil viscosity and oil temperature.





Operation Of Electromagnetic Actuator Of Camshaft Adjuster
The control piston (18) directs, depending on its position, the pressurized engine oil from the camshaft flange (22) into one of the two working chambers (A or B) and at the same time opens the oil return flow for the respective pressureless working chamber (A or B).





Moving Camshaft Adjuster Into "Retarded" Position
Actuator (Y49) is deenergized and as a result the control piston (18) is moved back as far as the stop ring (19) by the force of the compression spring (17) and allows engine oil to flow into the working chamber (A) and at the same time allows oil to flow back along the oil return for the working chamber (B).
The torque of the inlet camshaft sprocket (13) which is acting in the direction of rotation of the camshaft, pushes the adjusting piston (14) forward as a result of the screw effect of the helical gearing. The working chamber (B) is emptied through the drillings (14c) in the adjusting pistons (14), (16a) in the flange shafts (16), (18a) in the control piston (18) and two drillings (23) in the camshaft flange. The engine oil pressure which exists in the working chamber (A) additionally maintains the control piston (I) in the "retarded" position.





Function Of Conical Spring Of Camshaft Adjuster
A conical spring (14a) prevents noises being produced during starting (caused by the function-related backlash at the helical gearing).





Function Of Positioning Piston Of Camshaft Adjuster
The positioning piston (14) has an external and internal helical gearing (14b). The external helical gearing (14b) meshes into the helical gearing (13a) on the inlet camshaft sprocket (13), the internal helical gearing (14b) meshes into the helical gearing (16a) on the flange shaft (16). If the positioning piston (14) moves forward or back axially, depending on which working chamber (A or B) is pressurized, the camshaft (22) is rotated relative to the inlet camshaft sprocket (13) by these helical gearings.
The rotation angle of the camshaft (22) is limited by three stops (arrows) around the circumference between inlet camshaft sprocket (13) and flange shaft (16). A certain installation position is fixed is a result of a blocking tooth (Z) at the threads of the adjusting piston (14).





Operation Of Electromagnetic Actuator Of Camshaft Adjuster
When the actuator IY49) is energized, it attracts the armature (4) together with the control piston (18) forward and overcomes the spring force of the compression spring (17).





Switching Camshaft Adjuster Into "Advanced" Position
The actuator (Y49) is energized, as a result the armature (4) moves forward together with the control piston (18) and overcomes the spring force of the compression spring (17) and allows engine oil to flow into the working chamber (B).
The positioning piston (14) is moved back axially as a result and rotates the inlet camshaft (22) forward in the direction of rotation of the camshaft by means of the helical gearing.
The working chamber (A) is emptied at the same time pushed by the positioning piston (14) through the bores (16b) in the flange shaft (16) and two bores (23) in the camshaft flange.