Volvo 819 E - Page 26

Group 28 Ignition systems
Des ign and fun ct ion - Speed and crankshaft position i nformat ion
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TOC
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TOC
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Flywh eel/ carri er plate pr ofil es
The above figures show the three different ' Ioothed ' or drilled crankshaft/carrier plate profiles which are used . (The
profiles afe shown in section .) Unlike the starter motor ring gear, which is moun t ed on the flywheel. the profile used
for signal generation is usually an integral part of the component.
Volvo igni tion systems are supplied mainly by two manufacturers - Bosch of Germany and Bendix , France. Among
other factors. this means that several different profiles must be used. while the method whereby the control unit de-
tects and processes the induc tive pick-up signals may also differ .
The
electronic circuit ( which may be likened to a frequency divider or 'mul tiplier' ) in wh ich the signal is first received
and processed, also varies in design . The frequency of the incoming voltage pulses is divided by a certain factor to
i mprove signal resolution. Th is, in t urn, means that the cont r ol unil can regulate t he t iming in more precise steps, for
example, when re-advancing t he t iming afte r knock in a cylinder has been elimina ted.
A. I
gnition systems supplied by B endix employ a type 4412 toothed profile. The figure 44 means t ha t the flywheel is
provided with 44 dr illed holes , and t he figure 2 that it has two ' long ' teeth , each equal in leng th to tw o sho rter
teeth. In o
th er w ords, the profile is provided with 40 (44-2x2) sho rt t eeth and tw o l ong tee th . T he angular pitch be-
tw een tw o a dja cent short tee th (X O) is 8.18° (360°/44 ). The two long teeth wh ich com pris e the cranks haft position
reference points are located 180° apart (angle a ). The con tr ol unit identifies TDC as th e poi nt 90° after the passage
of a l
ong tooth .
Th e type 44/2 profile is used on Ae nix -F and Rex -I systems. In each case, the control unit applies a factor of 8.18 to
improve the signal resolution. This means th at it can adjust the timing in steps of 1.0
0
•
8. I gni ti on systems supplied by Bosch for Vol vo 4-cylinder engines fea ture a type 60/1 t oothed profile. This means
t
hat th e profile is provided with 60 drilled holes and with one ' long ' t ooth of tw ice the length of a 's hort' t oo th . In
other words , the pr ofile is provided wit h 58 (60-1x2) short teeth and one long tooth whi ch represents t he crank-
shaft posit io n reference point . The angular pitch between two adjacent sho rt teeth ly O) is 6.0" (3000/60). Th e con-
trol un it i dentif ies TDC as the point goo after the passage of the long t oo t h.
The type 6011 t oo t hed profile is used on the EZ -116K system . This means that the con trol unit applies a factor of 16
to improve the resolution of the pick-up signal. In effect , the control unit can adjust the t iming in steps of O.37se .
C. The EZ-1 15K igni tion system for B 280 engines is designed for a flywheel with a type 6013 toothed profile. The pro-
file is provided with 60 drilled holes and 3 'long' teeth , each of which is twice the length of a 'sho rt ' tooth . In other
words , the profile is prov ided w i th 54 (60-3 x2 ) short leeth and 3 long teeth as the crankshaft position reference
points . The angular pitch between two adjacent short teeth (Z O) is 6.00 (360°/60). The t hree long t eeth are located
120"
apart la ngle cl. The control unit iden tif ies TOC as the point 000 after the passage of a reference tooth .
The
con t rol un it applies a f actor of 16 to im prove the resolut io n of the pick-up signa l. In o th er words , the unit can
adjus t th e ti ming in st eps of 0.375°.
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