AUG-30-O1 10:38 From: ~ 02356847 2001-05-28 g057267173 T-099 P O6 Job-338
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:MAGNA REFLEX I-IQh7Zi~iG GM13H
Vehicle rear va.sirn s~rstem with e:lectrochromic mirror
The present invention reJ.ates to a vehicle rear vi-
sion system acCOrding to the pre~smble of the main
S claim.
Vehicle rear vision systems are l~;nown which have at
least one rearview mirror unit provided with an elec-
trochromic mirror, a control dev~.ce and a vehicle
1G power supply devzae, the contro;. device being con
nected for its power supply with the vehicle power
supply device and with the electrochromic mirror in
order to control the reflection properties of said
mirror in dependence on a control- voltage. Triggering
ef the electrdchrornie mirror in relation to its
transmission or reflection proper°ties comes about
through a d.c. voltage which may be adjusted in level
according to 1_ght sensors_ The triggering voltage
rraries here in a range s~etween ~'~' and a . g , approxi-
z0 mutely 1.2V. The d.c. voltage is generated from the
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conLroi device whose essential components are gener-
ally located in the housing of t:he rearview mirror
located in the interior of the vehicle (interior mir-
ror), in dependence an the amount of glare. As a
rule, both the interior mirror and rearview mirrors
lccated on the exterior of the vcshicle (exterior mir-
rors) are provided with electrochromic mirrors; gen-
erally the low control voltage is used for the uni-
form actuation of the interior m_~rror and of the ex-
terior mirrors.
However, problems arise from the fact that the vehi-
cle voltage of standard passerigex: vehicles is gener-
ally between 9V and 16V (nominal 12V), whilst the
highest value of the variable control voltage is e.g,
cnly 1.2V. The consequence of this is that, with a
typical current through an electxwchromic mirror of
approximately 3QOmA, dissipation of approximately 9W
has to be converted into heat. or: devices according
to the state of the art, this transformation gener-
ally happens by means of a power transistor which is
accommodated in the very low volume housing of the
interior mirror. In order tQ cpol down the very high
temperatures occurring, aluminium. cooling plates
which have to be attached to the power transistor are
generally used.
This unavoidable dissipation proves to be particu-
larly problematic in the miniaturisation of the elec-
tropics. According to the present state of the art it
is perfectly possible to integrate 4he entire elec-
tronics far actuating an electroc.lZromic mirror in an
integrated power semiconductor co:mpdnent (power IG).
A power 1C cf this kind would however have to be able
to lead away the abaveTmentioned 9W dissipation to
the environment in such a way th at its inner chip
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temperature remains below a critical value of genEr-
ally 125°C. This in turn requires, as well as a suit---
able costly power housing of the power IC, a suffi-
ciently large volume of surrounding air which has a
temperature low enough to cool. A large space o~ this
sort is however not generally available in the inte-
rior mirror housing (moreover this large space re-
quirement works against the intended miniaturisaT
tion). on exterior mirrors, this problem is further
intensified; as well as there being generally Gn even
smaller space available, here also the increased ba-
sic temperature of the mirror housing (for instance
as a result of intensive sunshine in the summer) has
to be taken into consideration. '
Thus the purpose underlying the present invention is
to create a vehicle rear vision system which makes
pcssable the accommodation of the' control device in
the smallest space, without the ciissipation which oc-
curs leading to an impairment in the functioning of
the control electronics system.
This purpose is fulfilled by ~ ve~hycle rear vision
system with the features of the preamble of the main
claim in connection with the characterising features
of the main claim.
Through the fact that the control device has a sheet-
type heating resistor to carzy away the heat occur-
zing through electrical dissipation, an imGpairment of
the functioning of the control electror_~ics car.. be
prevented by ar_ "evacuation" of the heat that occurs.
Secondly it is possible to divert the heat cccurring
in the sheet~type heating resistor to a place where
it fu~.fils for example the useful function of a heat--
ing device (for example for a mirror surface).
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Advantageous embodiments of the present invention are
given in the dependent claims.
An advantageous embodiment provides far the heating
resistor to be applied as a coating to a carrier ma-
terial, such as far examp7.e the non--reflective rear
side of the mirror of the rearview mixror unit, a
plastiCS fioil ar a fiat electrical line ("flex" or
strip conductor connection). The coating can be ap-
pl~.ed to a variety of flat carr;.:_er materials, the
heat that occurs here does not impair the functioning
of the control electronics and can also be used to
advantage (for example to step clouding barer of the
glass or icing of objects).
A particular advantageous embod~,ment provides far the
heating resistor to be disposed in meander shape on
the carrier material, pref~rably a plastics foil. On
the same plastics foil there can moreover be disposed
a meander-shaped mirror glass heating system produced
in the same way, it being possible to dispose the me-
ander structures of the two resistors compactly be-
sid~ one another or interlocking with one another. In
order to constantly guarantee a condensati.an-free
mirror, th~.s foil can be provided on both sides with
double-sided adhesive tape and be glued on one side
to the rear side of the mirror and on the other to a
glass support plate. As well as very good heat con-
duction towards the mirror to be heated, this moreo-
ver makes possible low-cost attachment of the m~.rror
glass to the glass suppoxt plate.
A further advantageous embodiment of the present in-
vention provides for the control device to have a
unit far pulse-width modulation of a control signal
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with a signal level, preferably at the level of the
vehicle voltage and the unit for the pulse-width
modulation to be connected to a converter, belonging
to the control device, for converting the pulse-width
5 mt~dulated signal into an analog control voltage. rt
is particularly advantageous when the signal level is
at the level of the vehicle voltage, to convey a sig-
nal generated from a signal generation unit located
in the housing of the interior mirror to the exterior
mirrors. In this case, the converter according to the
invention is located in the region of the exterior
mirror; the dissipation occurring in said mirror dur-
ing the conversion of the pulse-modulated signal at
the.level of the vehicle voltage into an analog con-
txol voltage of a lower level is converted again in a
heating resistor according to thE: invention. In so
doing, the separate earth wire b~aween znteriar mir-
ror and exterior mixrors, usual i_n rear vision sys-
terns according to the state of tree art, and necessary
in order to balance the potentiaa_ differences between
the interior and exterior mirrors of the veha_cle.
This stems from the fact that, when ,~. ~roltage is sup-
plied from the interior mirror to the exterior mir-
rors at the level of the vehicle voltage, the poten-
tial differences are of considerably Yess signifi-
cance than with direct transmission of the low con-
trol voltage (e_g. a maximum of 1.2V).
>~'urther advantageous embodiments of the present in-
ventior~ are given in the remaining dependent claims.
The present invention is now explained with the aid
of several figures. These show:
~'ig. 1 a heating resistor according to the invention
on the rear side of an electrochromic mirror,
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Fig. 2 a cross-section through an exterior mirror
according to the invention,
Fig. 3 a block diagram of a vehicle rear vision sys-
tem according to the invention,
Figs. 4a and 4b two possible ways of arranging the
wiring of a heating resistor accord-
inc3 to the invention.
Fig. 1 shows a dissipating resistor 3 according tc
the invention, Which in the (allowing is called heat-
ing resistor and which is embodied in meander shape
and d~.sposed on the non-reflective rear side 2a of an
electrochramic mirxor 2 of a rearview mirror unit.
fhe application of the heating resistor_ to the rear
side of the mirror 2a can come about by means of
metal coating in a plasma process, screen printing
~Q using resistor paste (the xesistor paste is applied
in the form of the desired heating elementy or gal- .
vanic coating. The heating resistor 3 (i.e. the coat-
ing) can be of copper, silver ar aluminium. In each
case, the heat.inc~ resistor is configured in lines or
flat; a heating resistor voltage is released between
the electrical connections 3a and 3b which represent
the beginning and end of the heating resister.
Likewise, a mirror glass heating system 6 is attached
~0 to the rear side 2a of the e7.ectrochromic mirror c,
which system in addition heats the mirror 2. This can
also be cl~.sposed in meander shape; .it prwcres particu-
larly advantageous if, as shown in Fig_ 1, the course
of the mirror glass heating system 6 is designed com-
~5 p~.ementary to the course of the heating resistor 3.
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It is not abso~.utely necessary to dispose the hea~.ing
resistor 3 directly on the electrachremic mirror 2.
There is admittedly an advantageous heating effect
here which helps to prevent icing or clouding ovax of
the mirror surface, but other arra3ngements are also
possible. Thus, for example, provision can be made
for the heating resistor 3 to be applied to foil
printed circuits ("flex", or "FPC" supply lines).
These supply lines ~ar~ for example pro~tride the elec-
14 trical connection between the corlt_rol device and the
electrochromic mirror or also connect individual ele-
ments of the control device to onra another (see in
this connection also Fig. 3).
E'i.g. 2 shows the cross-section of an exterior mirror
according to the invention or an Exterior mirror unit
5_ This has an electrochromic mirz°ar 2 which ~.s elec-
trical.ly connected, in a manner which is not spawn in
detail, with a control device. This control device or
parts of the control device (see F'ig. 3} can be ac~-
commodated within the housing 9 of; the exterior mir-
ror unit 5 (in Fig. 2 only the heatJ.ng resistor 3 be-
longing to the control device and lying inside the
housing 9 is shown).
The housing 3 is connected via a web 19 w~.th the ex-
terior ehass~.s :L$ of an automotizr~~ vehicle. A glass
adjustment drive 8 situated inside: the housing 9 car-
ries a glass support plate 7. To t;he szde: of the
3C glass support plate 7 remote from the glass adjust-
ment drive 8 is attachEd a heating resistor 3 accord-
ing to the invention. This ~.s connected with further
elements, not shown, of a control device via electri-
cal contacts 3a, 3b, which can be embodied as flexa..-
ble cables. The electrochromic min-ror 2 is attached
to the side of the heating resistor 3 remote from the
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glass support plate. The attachme:rlt of the heating
resistor 3 between the glass support plate 7 and the
electrochromic mirror 2 can ComE .about in various
ways. The heating resistor 3 can for example ire ap-
plied as a solid coating to the rear side 2a of the
electrochrornic mirror.
A further possibility is that the heating resistor 3
is embodied as a foil composite. To this end, the re-
~.0 sistor element running between the contacts 3a and 3b
is enclosed between two foils. It is now possible to
attach this foil composite as a farm-fit, for in-
stance by means of a snap-an plug connection, to the
rear side 2a of the electroohromic mirror. Another
variant provides for the outer sides of the foil com-
posite to be sElf-adhesive. In this case, the heating
resistor 3 ensures the secure connectJ.on of the mir-
ror 2 on the glass support plate 7 (instead df tile
self~-adhesive exterior surface of the foil, a double--
2~ sided adhesive tape can naturally also be glued to
the outer sides of the foil composite, which has the
same function).
~t is also possible to accommodate further elements
of the control device, e.g. an integral:ed circuit,
between the glass support plate 7 and mirror 2. This
l.ntegrated circuit can either be applied directly to
the rear side 2a of the mirror 2 or to a foil. This
application can come about in SMD technology or chip-
an board technology. An integrated circuit could also
be accommodated within. the foil composite described
above. Heat-resistant plastics are preferably used as
foils here.
Further elements of the control d~,evice, for instance
a digital-analog converter, can likewise be accommo-
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dated inszde the housing 9 of the exterior mirror
unit 5, for example inside the glass adjustment drive
8.
The above embodiments referred by way of example to
the exterior mirrors shown in Figa. I and 2. The de-
scribed embodiments are simi7.arly applicable to inte-
rior mirrors.
Fiq. 3 shows the diagrammatic construction of the
whole vehicle rear vision system. This contains two
rearview units, an interior mirror unit 4 as well as
an exterior mirror unit 5. A vehicle power supply de-
vice, not shown in detail, providE=s a d.c. voltage of
7.5 a nominal 12v. The vehicle voltage= can however be be-
tween 5'~ and 2~V, depending an th~a automotive vehi-
cle. The vehicle power supply dev_~ce is connected to
the control unit an order to supp~!y it with powez:.
The exterior mirror unit 5 has anew or two electro-
chromic mirrors, (respectively one on each side of
the vehicle), t:ne interior mirror unit has one elec-
t.r.ochromic vehicle mirror.
A glare sensor 10 attached to the interior mirror and
~5 orientated in the d~.reotion of rei"lection of the
electrochromic mirror (i.e. towards the rear of the
vehicle), measures the incident l~.ght flux Pram the
rear of the vehicle (for instance from vehicles trav-
elling behind same). A daylight seansor 11; which is
orientated e.g. in the direction of motion or towards
one side of the vehicle, determinE:s a further light
flux. Senscars 10 and 11 are connected to a computing
unit 20 of the control device for data transmission.
Depending on the measurEment values of the sensors,
the amount of glare is determined by the computing
unit 20, and converted into an analog control signal.
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1. 0
This analog control signal is then supplied to a
transistor (see input 1'7a of transistor Q in Figs. 4a
and 4b). The circuit shown in Figs. 4a and 9b, which
will be described in detail later, makes available to
the elect~ochxamic mirror 2 a d.c. voltage vaxyinc~
between OV and 1.5V according to the amount of glare_
In dependence on this voltage, the reflection proper-
ties of the electrochromic mirror 2 alter in known
fashion. The analog voltage 21 is e.g, laetween JV and
1.5V. It can however, accprding to the embodiment,
cover higher voltage regions, e.g_ from pV - 2.5V.
In addition tp controlling the reflection properties
of the interior mirror, the computing unit 2d also
controls the re f ection properties of at least one
electrochromic mirrox 2 of the exterior mirror unit
5. To this end, the computing unit 20 transm~.ts an
analog signal, as was far ir_stance supplied to the
eleotxochromic mirror 2 of the interior mirror unit
2C 9, to the electrochromic mirror 2 ef the exterior
mirror unit 5. This signal can be transmitted e.g.
directly. Fig. 3 shows a fux-ther possible way of
transmission.
This possib~.~.i.ty consists in the analog control sig-
nal being digitised first of all in an analog-digital
converter 15, which is accommodated far instance in a
"roof modulE," of an automotive vehicle, (according
to the design of the computing unit 20, in some ern-
bodiments a micro-controller integrated in the com-
puting unit 20 can already emit a d~.gital signal).
The signal digitized in trie analog-digital converter
7.5 is led by means of a data bus to a door contxol
apparatus 12. The door control apparatus i.~ is de-
signed as a node, which controls all the functa.ons of
the door, such as glass adjustment drive, mirror
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glass heating, tilt:~ng mechanism drive, lighting de-
vices and signal device.
The connection between the door control apparatus 12
and unit 19 shows a further variax:t of the transmis-
sion Qf the control signal to ari selectrochromie mir-
ror 2.
The dour control apparatus 12 belonging tc the con-
trot device contains a unit for t:he pulse-width modu-
lation of a control signal with a signal level at the
level of the vehicle voltage (naturally, as well as
the standard 12V vehicle voltage, other levels cf
voltage are possible). The pulse-width modulated
brightness signal is led with a signal level at the
levP1 of the vehicle voltage to unit 14. Unit 19 has
a converter, belonging to the control devJ.ce, for
converting the pulse-width modulated signal ~.3 into
an analog control voltage. zn order to avoid the heat
problems depicted in the introduction to the specifi--
catior~, in this conversion a circuit arrangement as
per ?"igs. 4a or 4b is needed. ThE; low analog control
voltage (preferably between 0V and 1.5v) is then led
to the electrochromic mirror 2.
z~
Tn the present example, the computing unit 20 is ac-
commodated in the interior mirror unit. it is natu--
rall~r possible to accommodate thc~ c4mputing unit 2g
in the exterior mirror unit 5 also. As a result of
the design acccrdir~g to the invention of a heating
resistor, no heat problems here occur in the exterior
mirror, the heat can even be used as available heat
for heating the mirror surface. The computing unit
can also be acaommodat~d in other places, far example
in the region of the door control apparatus 12 or of
the roof module.
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The embodiment given by way of example and shown in
Fig. 3 thus shows a plurality of transmission paths
between the computing unit 24 and an electrochrornic
mirror 2:
analog transmission
2. digitisation and transmissiaxl by means of data
bus
lp 3. pulse-width modulation with <a signal. level e.g.
at the level of the vehicle voltage.
It is naturally possible to use just one of the sys-
tems presented for signal transmis~iori. For this, in
tlye case of digital transmission .by means of data
bus, (preferably a DART or CAN protocol is used) e.g.
a digital-analog converter is necessary for convert-
ing the data bus signal into an analog control volt-
age.
zo
Fig. 4a shows a circuit for minimisation of heat de-
velopment in the region of the transistor Q. The
sheet-type heating resistor 3 iS Connected in series
to a parallel circuit of a control transistor Q and
2~ an electrochromic mirror 2. Between points 23 and 24
is released a voltage at the level of the vehicle
voltage. Through input 2~a, a control voltage or a
control signal is supplied to thE~ transistor Q, by
which means the current passing i~hrough transistor
30 and resistor is adjusted. pepend:ing on this transient
current, a different component voltage is released on
the heating resistor R such that a residual voltage
of a different level remains on the electrochromic
mirror z and is far example in the region between aV
35 and 1.5V. The use of a circuit as per Fig. ~a is par-
ticularly advantageous since the dissipation occur
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:r 3
ring in the transistor is particularly low therEin,
(instead of the 44a mentioned init:~ally in power tran-
sistors according to the state of the art, here c.g.
only 0.5w are to be con~rertEd in the transistor) .
F~.g. ~b shows a further embodiment of a circuit ar-
rangem~nt accordinC~ to the invention. Between points
23 and 2~ there is a voltage cf e.g. 12V (the level
of the vehicle vo~.tage). rn this embodiment, the
lp transistor Q, which is actuated by a control. sigr'Aal
1?a, the heating resistor 3 and t:he elec~trachromic
mirror 2 are connected in series. As in the arrange
meat shown in Fig. Via, the heating resistor is dis-
posed flat te.g. in a spiral or rneander shape).
1
~'he circuits shown in Figs. as and 4b s?~ou~.d be so
laid out that the maximum control vo>rtagc on the
electrochromic mirror is less than 250 of the nominal
vehicle voltage.
