 |
|
 |
Begin OCR Text:
,o___j ,_
_ 18OO
When the fuel tank is empty, the cu rrent flows
__\\
through the series-connected coil, passes _through
the tank fitting and then to earth. l n this position +
only a few of the windings of the tank fitting
rheostat are in circu it, so that there is only a smaIl
amount of resistance to the current. The magnetic
force which arises when the current passes
through the coil attracts the armatu re plate of
the d ial unit and the pointer goes over to '' Empty''.
When fil l ing the tank, a successively larger part _
of the rheostat comes into ci rcuit, which means
increased resistance for the current flowing
through. An î-ncreasing part of the current will Fig. 3. _o_gtru_tjo_ g_d fu__tio_ of the fuel gauge. _'
therefore tend to flow th rough the coil which is _
connected directly to earth. The armature of the _ p , M M,_ _ _ _ , _ -
dial unit is then influenced by this coil due to the 1 ' , _ 1 _ ' , _
Iarger number of wind ings which it has compared
' __' ' i _
with the series-connected coil. The pointer then 1 _, _, ,
moves over from the '' Empty'' position and wi l I 1,',,' 1.'
give a reading on the scaIe ín proportion to _the 1,_' , 1 _ _
amount oi iue_ ii _ _ed in. ,
',, p,,,', ,, ,',,
__E EDOM E_ER _ I I__1Il I
The speedometer is of the eddy cu rrent type, It is _ , _
d _ b i b_ _ d te c ble_ _ ' 1 1 _
riVen y meanS o a Ca e _Spee Ome f a ) 1 ' 1 1 ' 1 ' ; , ,
from a worm gear on the output shaft of the gear- ' _ ' '_ 1 ' _ _ 1 1
h ' t, ,
box To enable the speed to be read off on t e -- ' _ j j
. v,,o,__vqo,
instrument dial, the speedometer has a permanent d
d d _ . . t d Fig. _. Fro_t a_d reverse sîdes of gp$e ometer.
magnet, a fitting isc an an a uminium ro or rum. i . t t _
Th _ tt . t d t th . t h it i the 1 . Conne Ction of tripme er COn fO _
e a er is connec e o e poin er s a o 2 C . i d t _ _ _ b_
. onnection or spee ome er riving ca e_
instrument. The rotor d rum is fitted on one end
of the shaft and the pointer on the other. A coun- _
_
t b _ . g _ a_so c nnected to the shaft _ 2 3 4 5 6
ef a anCe Spfjn iS O )
the purpose of which is to brake the m6vement of
'
the rotor drum at the same time as it tends to
move the pointer to the ''O'' position when the car _ '
is stopped. The numeral rol Iers of the mileometer
and tripmeter are driven by means of a number
of gears d i rect from the speedometer driving
cable. The ratios of these gears are chosen so _ _
that the speedometer d ríving cable has to rotate i
62O times to register one kilometre (992 times for
1 mi Ie).
As mentioned above, the part of the speedometer
which registers the speed operates magnetical Iy.
When the car begins to move, the driving cable
begins to rotate, and thereby also the permanent Fig. f. S_hemati_ _iew of speedometer.
magnet. This then generates a rotatíng magnetic 1 _ Pointef
f_ _d h_ h _ _ t dd t _ the tor 2. CoUntefbalanCe Spfing
ie W I C g IVeS fISe O e y C Uffen S In fO
_ i . i h 3. Fitting di__c
d rum The ines o magnetic orce go over t e q _ d
' . otor rum
fitting disc Df the instrUment_ _. permanent magnet
The torque effect wh ich the magnetic fie Id has 6. Worm gear drive for mi leometer and tripmeter
_ 9- 2
|
