Variable Valve Timing Actuator: Description and Operation
Function of camshaft adjuster
1. M6 x 18 bolt
2. Servo magnet with 2-pin connector
3. Bolt
4. Armature
5. 3 x 22 roll pin in armature
6. M20 x 1.5 nut, WAF 30
7. Front cover
8. Seal
9. Ignition control module position sensor
10. M6 x 16 bolt+washer
11. Seal
12. Cover with seal
13. Camshaft sprocket with position indicator (b)
14. Positioning piston
(1st version: size c 25.45 mm)
(2nd version: size c 25.0 mm)
15. Bolt+washer **hyperlink**
15a. Collar bolt **hyperlink**
16. Flanged shaft
(1st version: d with recess)
(2nd version: d without recess)
17. Compression spring
18. Control plunger
19. 18 x 1 circlip
20. End cover A 18 oil drilling
21. Straight pin in camshaft
22. Inlet camshaft (size e see **hyperlink**)
Function
When the engine is running, the camshaft adjuster rotates the inlet camshaft hydraulically/mechanically relative to the camshaft sprocket by 34° (29°) *) (engine 104.98) or 32° (engine 104.99) crank angle, respectively, to the "advanced" position and back to the "retarded" position. The camshaft adjuster is actuated electromechanically by the CFI or LH-SFI control module. The positioning time of approx. 1 second is dependent on the engine oil pressure at the camshaft adjuster and on the oil visosity and oil temperature, respectively. The position indicator on the camshaft sprocket (13) provides the camshaft rotational speed to the position sensor (9) as an input parameter for the ignition control module or, on engine 104.99, for the LH-SFI control module.
*) As of approx. 04/91 except USA
Engine switched off ("retarded")
The compression spring (17) pushes the control plunger (18) against the circlip (19). The engine oil pressure in the camshaft adjuster is eliminated.
From 0 to 1000 -> 2000/min ("retarded")
The torque of the internally helically toothed camshaft sprocket (13) acting in the direction of rotation of the engine pushes the externally helically toothed positioning piston (14) against the cover (12) as a result of the screw action. Consequently, the likewise internally helically toothed positioning piston (14) holds the externally helically toothed flanged shaft (16) together with the bolted-on camshaft (22) in the "retarded position". The compression spring (17) pushes the control plunger (18) against the circlip (19). The engine oil flows through two oblique drillings in the camshaft flange and in the flanged shaft (16) into the working chamber (A) and holds the positioning piston (14) additionally in the "retarded" position with the available engine oil pressure.
Leak oil flows off over control and positioning piston surface, through the control plunger drilling and 2 drillings (23) in the camshaft flange.
"Retarded" position
Servo magnet (Y49) not energized. Control pluner (18) against rear stop. Positioning piston (14) against front stop. Oil pressure in working chamber (A).
A Working chamber
12 Cover with ring
13 Camshaft sprocket
14 Positioning piston
16 Flanged shaft
17 Compression spring
18 Control plunger
19 18x1 Circlip
22 Camshaft
23 Oil outlet drilling
Y49 Servo magnet with 2-pin connector
From 1000 -> 2000 to 5000/min ("advanced")
The control plunger (18) is pulled forward as far as the stop in the flanged shaft (16) by the servo magnet (Y49) against the force of the compression spring (17).
The control plunger (18) closes the oil feed to the working chamber "A" and at the same time allows oil to flow to the working chamber "B" through 2 drillings each in the flanged shaft (16) and adjusting piston (14). The engine oil pressure moves the adjusting piston (14) as far as the stop on the flanged shaft (16).
As a result of the axial movement of the adjusting piston (14), the camshaft (22) bolted to the flanged shaft (16) is turned into the "advanced" position. The turning action is achieved as a result of the effect of the helical teeth on the camshaft sprocket (13), positioning piston (14) and flanged shaft (16). The engine oil in working chamber "A" flows off, assisted by the pushing action of the adjusting piston (14), over the flanged shaft (16) and through 2 drillings (23) in the camshaft flange.
"Advanced" position
Servo magnet (Y49) energized. Control plunger (18) against front stop. Positioning piston (14) against rear stop. Oil pressure in working chamber (B).
A Working chamber
B Working chamber
12 Cover with ring
13 Camshaft sprocket
14 Positioning piston
16 Flanged shaft
17 Compression spring
18 Control plunger
19 18 x 1 circlip
22 Camshaft
23 Oil outlet drilling
Y49 Servo magnet with 2-pin connector
From 5000/min ("retarded")
The electromagnetic actuator (Y49) is not energized and allows the control plunger to move. The compression spring (17) pushes the control plunger (18) against the cirdip (19). The oil feed to the working chamber "B" is closed off and oil is able to flow to working chamber "A'. along 2 drillings in the flanged shaft (16). As a result of the engine oil pressure the control plunger (18) is moved as far as the cover (12)
This axial movement of the adjusting piston (14) rotates the camshaft (22) bolted to the flanged shaft (16) into the "retarded" position.
The rotational movement is a result of the screw effect of the helical teeth on the camshaft sprocket (13), positioning piston (14) and flanded shaft (16). The engine oil in the working chamber (B) flows off, assisted by the pushing action of the adjusting piston (14), through 2 drillings each in the adjusting piston (14), flanged shaft (16) and control plunger (18) through the control plunger (18) and 2 drillings in the camshaft flange (23).
Leak oil flows off over the control plunger and adjusting piston surfaces through the control plunger drilling and 2 drillings in the camshaft flange (23).