U.S. patent number RE33,308 [Application Number 07/175,041] was granted by the patent office on 1990-08-21 for automatic window wiper control.
This patent grant is currently assigned to Mist-Defy'r, Inc.. Invention is credited to Marl J. Bell, Donald L. Millerd.
United States Patent |
RE33,308 |
Millerd , et al. |
August 21, 1990 |
Automatic window wiper control
Abstract
The invention is directed to an automatic wiper control circuit
for operating window wipers automatically when moisture is sensed.
The control circuit additionally provides for increasing the speed
of a dual speed wiper motor when a high level of moisture is
detected. The system comprises a moisture sensor which senses
moisture thereon. A circuit associated with the moisture sensor
converts the moisture level to DC voltage. At a preselected level
of this DC voltage the wiper motor operates in one of its two
different speeds. A lack of a predetermined amount of moisture
terminates the wiper motor operation. If the control circuit
terminates the wiper motor action during wiper sweep, the normal
homing circuit of the wiper motor continues to operate the motor
until the wiper blade or blades reach the wiper blade home
position. Sequential illumination of a plurality of light emitting
diodes (LEDS) occur during a wiping cycle when the circuit is
operating normally. A switch is provided to remove the automatic
wiper control circuit from the conventional automotive wiper motor
circuit. A separate LED provides a visual indication of automatic
wiper control circuit disconnection from the conventional
automotive wiper motor circuit.
Inventors: |
Millerd; Donald L. (San Diego,
CA), Bell; Marl J. (Valley Center, CA) |
Assignee: |
Mist-Defy'r, Inc. (La Jolla,
CA)
|
Family
ID: |
26683791 |
Appl.
No.: |
07/175,041 |
Filed: |
March 29, 1988 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
012617 |
Feb 9, 1987 |
04705998 |
Nov 10, 1987 |
|
|
Current U.S.
Class: |
318/444;
15/250.17; 318/480; 318/483; 318/490; 318/DIG.2 |
Current CPC
Class: |
B60S
1/0818 (20130101) |
Current International
Class: |
B60S
1/08 (20060101); B60S 001/08 () |
Field of
Search: |
;318/443,444,445,480,483,490,DIG.2 ;15/25C,250.17 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Ro; Bentsu
Attorney, Agent or Firm: Milde & Robinson
Claims
What is claimed is:
1. An automatic wiper motor control system for operating a window
wiper motor which operates at least one wiper blade to and fro
across window for removing moisture from .[.the.]. .Iadd.an
.Iaddend.area which it sweeps, said motor having a park circuit
means for returning said wiper blade to a home location when said
wiper motor .[.motor.]. .Iadd.operation .Iaddend.is terminated at
other than the wiper blade home location comprising:
a voltage source;
a moisture sensor, said moisture sensor comprising a plurality of
spaced apart exposed conductive strips positioned within .[.an.].
.Iadd.the .Iaddend.area of the sweep of said at least one wiper
blade;
a voltage storage means;
a scanning circuit for sequentially connecting adjacent pairs of
said conductive strips, one of said pair to said voltage source and
the other of said pair to said voltage storage means;
a wiper motor operating circuit .Iadd.for activating said wiper
motor.Iaddend.;
a voltage sensing means connected between said voltage storage
means and said wiper motor operating circuit, said voltage sensing
means activates said wiper motor operating circuit when the voltage
level of said voltage storage means exceeds a preselected voltage
level; and
a wiper position sensor means positioned along the sweep of said
wiper blade and influenced by the blade passing thereacross for
.[.activating the operation of said voltage sensing means.].
.Iadd.controlling termination of the operation of said wiper motor
.Iaddend., whereby a determination is made by said .[.automotive.].
.Iadd.automatic .Iaddend.wiper motor control system to operate said
wiper motor or terminate said operation .Iadd.in dependence upon
the amount of moisture on the window .Iaddend..
2. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 1
wherein said wiper motor is multi-speed.
3. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 1
wherein said voltage source is a storage battery.
4. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 1
wherein said scanning circuit comprises a pair of multiplexer
circuits each of which is operated at a common frequency.
5. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 1
wherein said voltage sensing means comprises a means to constantly
remove a portion of the voltage stored .[.therein.]. .Iadd.in said
voltage storage means.Iaddend..
6. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 2
wherein said voltage sensing means comprises means for operating
said multi-speed wiper motor at one speed when the voltage in said
voltage storage means is above a first preset level and at an
increased speed when the voltage in said voltage storage means
exceeds a second preset level.
7. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 6
wherein the first preset level of voltage which operates said
multi-speed wiper motor at said one speed is adjustable.
8. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 6
wherein the second preset level of voltage which operates said
multi-speed wiper motor at said increased speed is adjustable.
9. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 1
additionally comprising visual means for providing indication of
operation of said scanning circuit.
10. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 9
wherein said visual means includes a plurality of .[.LEDS.].
.Iadd.LEDs.Iaddend..
11. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim
10 wherein said .[.LEDS.]. .Iadd.LEDs .Iaddend.all illuminate in
the same color.
12. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim
10 wherein some of said .[.LEDS.]. .Iadd.LEDs .Iaddend.illuminate
in different colors than others thereof.
13. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 2
additionally comprises a switch for removing said automatic wiper
motor control system from control of said multi speed wiper motor
and an LED connected in conjunction therewith for a visual
indication of the removal of said automatic wiper motor control
system from control of said multi-speed wiper motor.
14. The .[.invention.]. .Iadd.system .Iaddend.as defined in claim 1
wherein said park circuit means continues to operate said wiper
motor when said wiper blade across said position sensor .Iadd.means
.Iaddend.causes said automatic wiper motor control .Iadd.system
.Iaddend.to terminate operation of said wiper motor. .Iadd.
15. An automatic wiper control system for operating a window wiper
motor which moves at least one wiper blade to and fro across the
window for removing moisture from an area which it sweeps, said
system comprising, in combination:
(a) a voltage source;
(b) current detection means, having an input and an output, for
producing a wiper activation signal at said output, said wiper
motor being operated in response to said wiper activation
signal;
(c) a moisture sensor comprising at least three spaced apart,
exposed conductive strips;
(d) first means for connecting one of said conductive strips to
said voltage source; and
(e) second means for connecting one other of said conductive strips
to said current detection means;
wherein said first and second means sequentially scan adjacent
pairs of said conductive strips, one of said pair to said voltage
source and the other of said pair to said current detection means,
respectively; and
wherein said current detection means includes means for
accumulating a parameter substantially representative of the
current received by each of said other conductive strips during at
least one scan of said conductive strips by said first and second
means;
whereby a determination is made by said wiper motor control system
to operate said wiper motor or to terminate its operation, in
dependence upon the amount of moisture on the window. .Iaddend.
.Iadd.
16. The control system defined in claim 15, wherein said moisture
sensor is positioned on the window within the area of sweep of said
wiper blade. .Iaddend. .Iadd.
17. The control system defined in claim 15, wherein said current
detection means includes:
voltage storage means; and
voltage sensing means, connected to said voltage storage means, for
producing said wiper activation signal when the voltage level of
said voltage storage means exceeds a preselected voltage level.
.Iaddend. .Iadd.18. The control system defined in claim 15, further
comprising wiper position sensor means positioned along the sweep
of said wiper blade and influenced by the blade passing
thereacross, for enabling the operation of said current detection
means to produce said wiper activation signal. .Iaddend. .Iadd.19.
The control system defined in claim 15, wherein said wiper motor is
multi-speed and wherein said current detection means is operative
to control the speed of said motor in response to the level of
current at said input. .Iaddend. .Iadd.20. The control system as
defined in claim 15, wherein said voltage source is a storage
battery. .Iaddend.
.Iadd.21. The control system defined in claim 15, wherein said
first and second means comprise a pair of multiplexer circuits each
of which is operated at a common frequency. .Iaddend. .Iadd.22. The
control system defined in claim 17, wherein said voltage sensing
means comprises a means to constantly remove a portion of the
voltage stored in said voltage storage means. .Iaddend. .Iadd.23.
The control system defined in claim 17, wherein said wiper motor is
multi-speed and wherein said voltage sensing means comprises means
for operating said multi-speed wiper motor at one speed when the
voltage in said voltage storage means is above a first preset level
and at an increased speed when the voltage in said voltage storage
means exceeds a second preset level. .Iaddend. .Iadd.24. The
control system defined in claim 23, wherein the first preset level
of voltage which operates said multi-speed wiper motor at said one
speed is adjustable. .Iaddend. .Iadd.25. The control system defined
in claim 23, wherein the second preset level of voltage which
operates said multi-speed
wiper motor at said increased speed is adjustable. .Iaddend.
.Iadd.26. The control system defined in claim 15, additionally
comprising visual means for providing indication of operation at
least one of said first and second means and said current detection
means. .Iaddend. .Iadd.27. The control system defined in claim 26,
wherein said visual means includes a plurality of LEDs. .Iaddend.
.Iadd.28. The control system defined in claim 27, wherein said LEDs
all illuminate in the same color. .Iaddend. .Iadd.29. The control
system defined in claim 27, wherein some of said LEDs illuminate in
different colors than others thereof. .Iaddend. .Iadd.30. The
control system defined in claim 19, further comprising a manual
switch for removing said automatic wiper motor control system from
control of said multi-speed wiper motor. .Iaddend. .Iadd.31. The
control system defined in claim 30, further comprising an LED
connected with said manual switch for a visual indication of the
removal of said automatic wiper motor control system from control
of said multi-speed wiper motor.
.Iaddend. .Iadd.32. The control system defined in claim 18, wherein
said wiper motor has park circuit means for returning said wiper
blade to a home location when said wiper motor operation is
terminated at other than the wiper blade home location, said park
circuit means continuing to operate said wiper motor when said
wiper blade crosses said position sensor means and causes said
automatic wiper motor control system to terminate operation of said
wiper motor. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to a wiper motor control
system for clearing windows including, but not limited to, an
automotive windshield or rear window wiper blade or blades, which
automatically operates and controls the operating speed of a wiper
blade or blades according to rain or moisture conditions. More
particularly, the invention relates to a wiper motor control system
having an exterior sensor which continually monitors moisture
conditions on the windshield or rear window and is influenced
thereby to remain inoperative or to operate the wiper motor in one
of two speeds according to this influence. The sensor is positioned
within an area swept by the wiper blades.
U.S. Pat. No. 4,554,493 teaches an apparatus for automatic
activation and control of windshield wiper blades in response to
moisture accumulation at the exterior surface of the windshield,
including a pair of wires sandwiched within the windshield laminate
and positioned below the surface of the windshield. The wiper
blades provide a variable capacitance to a detection circuit. Wiper
blade action is initiated when the capacitance measurement exceeds
a predetermined reference standard.
U.S. Pat. No. 4,463,294 teaches a control circuit for a windshield
wiper motor which utilizes a plurality of infrared emitters that
emit a chain of infrared pulses towards a plurality of infrared
sensors. When rain passes between the infrared emitters and
sensors, the rain interrupts the flow of pulses therebetween. A
control circuit senses the missed pulses and selectively energizes
a low-speed, mid-speed, and high-speed windings associated with the
wiper motor.
U.S. Pat. No. 4,495,452 teaches a windshield wiper motor control
which receives information as to the amount of moisture on the
windshield through a sensor within the area swept by the windshield
wipers. The sensor may be of the capacitive type and may generate
an AC-signal the frequency of which is indicative of the relative
humidity of the windshield. The sensor and circuit of this teaching
is susceptible to temperature changes and impurities present on a
dry windshield.
U.S. Pat. No. 4,527,105 teaches additional means for automatic
operation of windshield wiper motors.
All improved automatic window wiper motor system which overcome the
short comings of the prior art and improves safety, especially,
when used in the control of automobile windshield and rear window
wipers would find wide acceptance.
SUMMARY OF THE INVENTION
The invention is directed to the automatic control of window wiper
motor including the windshield wiper motor of an automotive vehicle
and a control which operates under all moisture or rain conditions
to keep the window clear of moisture or rain. An automatic
windshield wiper motor control of this nature allows the operator
of an automotive vehicle to concentrate on driving when under
adverse conditions and not break concentration directed to the
automotive operation by continually adjusting the speed or
operation of the windshield wiper blade or blades or adjusting
existing time delay circuitry.
Applicants provide an automotive windshield or rear window wiper
motor control system which includes a novel sensor means comprised
of a plurality of side-by side exposed conductive strips positioned
on the external surface of the windshield or rear window in the
path of a wiper blade sweep. A multiplexer circuit continues to
select adjacent pairs of the conductive strips and connects a DC
voltage to one end of one of a selected strip and connects one end
of the other selected strip to the control circuit input. When
moisture or water is present between adjacent strips simultaneously
connected by the multiplexer circuit, the DC voltage conducts
between the normally open circuit selected strips to the control
circuit. The DC voltage level present at the control circuit input
will depend on the amount of moisture or rain between the strips
and the conductivity of that moisture or rain. When a selected
level of DC voltage is present at the input of the control circuit
the wiper motor will become operative. A slight amount of moisture
or rain present, above a minimum preselected level, will operate
the wiper motor at a first slow speed and an amount of moisture or
rain exceeding a range for the selected level for low speed wiper
motor operation will cause the wiper motor to operate at a second
or faster speed when the motor is equipped for a multi-speed
operation. Additional circuits could be added to accomodate
additional available wiper motor speeds greater than two. Most
modern automotive vehicles are factory equipped with a standard two
speed wiper motor and the explanation herein is directed to such a
motor, but the invention should not be considered limited to two
speed motors or to the application to automatic windshields or rear
windows as the invention can be employed for use with single or
multi-speed wiper motors which are used on any type of window,
windshield and the like.
The motor control circuit of the invention includes a wiper blade
position sensor which when influenced by wiper blade passing
thereacross initiates the control circuit to determine whether or
not the wiper motor will be operated for an additional wiper blade
sweep.
The wiper blade position sensor terminates wiper motor operation in
the absence of moisture or a level of moisture below a pre-set
level on adjacent strips of the sensor. The wiper motor park switch
present in modern conventional wiper motors continues to operate
the wiper motor after the wiper blade position sensor has
instructed the circuit of the invention to terminate wiper motor
operation until the wiper blade(s) have reached their home or
normally stowed position(s).
The sequencing of the multiplexer is monitored by light emitting
diodes (LEDS) of the same or mixed different colors. The operation
of these LEDS provide a pleasant "light show" as well as monitoring
system operation and therefore are positioned within the view of
the automobile operator and passengers. The presence of the LEDS
illumination and failure of wiper action would indicate that the
blade is frozen to the window or otherwise prevented from
movement.
A local control switch convenient to the operator allows the
switching of the automatic wiper motor control system in or out of
the normal wiper motor circuit, as selected by the operator. An LED
associated with the local control switch illuminates when the
automatic wiper motor system of the invention has been
disconnected.
It is an object of the invention to provide an automatic control
for a windshield wiper motor which is responsive to moisture or
rain deposited on the exterior surface of the windshield.
It is a further object of the invention to provide a sensor
comprised of a plurality of side-by-side conduction strips, pairs
of which are multiplexed for sequential moisture sensing
thereacross.
It is a further object of the invention to provide means for
automatically changing the speed of the wiper motor with changing
moisture conditions.
It is still a further object of the invention to provide a wiper
blade position sensor for sensing moisture conditions on the
moisture sensor during the wiper blade sweep across the wiper blade
position sensor.
It is still a further object of the invention to utilize the
home-park switch of the wiper motor to return the wiper blade or
blades to the home or stowed position after wiper motor termination
by the automatic wiper motor control.
A yet further object of the invention is to provide LEDS for
visually monitoring the operating sequence of the multiplexer
circuits.
These and other objects and benefits of the invention will be
apparent to those skilled in the art based upon the following
detailed description taken in combination with the following
drawings, wherein;
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing of the inter connected elements
of the present invention;
FIG. 2 is a top plan view showing in partial cutaway the present
invention adapted to the forward portion of an automotive
vehicle;
FIG. 3 is a detailed schematic showing of the circuit of FIG. 1;
and
FIG. 4 is a typical printed circuit moisture sensor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, there is shown a block diagram of the
automatic wiper motor control system 10 of the present invention.
The system comprises a sensor 12, a scanning circuit 14, an
oscillator 16, a scan select circuit 18, a wiper blade position
sensor 20, a filter 22, a high speed comparator 24, a control logic
circuit 26, an adjustable reference voltage 28, a low/high speed
wiper motor speed select circuit 30, and a wiper motor energize
circuit 32. These circuits which are hereinafter described in
greater detail are electrically interconnected as shown by the
various connecting lines therebetween. The arrow heads on the
interconnecting lines denote direction of signal or current flow
therebetween.
Referring now also to FIG. 2 which shows, in partial cutaway, the
forward portion of an automobile 34 incorporating the present
invention.
The automobile 34 typically includes a hood 36, top 38, dash 40,
windshield 42, wiper motor 44, wiper motor to wipe blade linkage 46
and a pair of wiper blades 48.
Shown centrally located on windshield 42 is the system moisture
sensor 12. The moisture sensor is electrically connected to circuit
components (hereinafter discussed in detail) contained within
housing portions 15A and 15B which in turn are interconnected to
the wiper blade position sensor 20. Wiper motor 44 is connected to
15A. Portion 15A of the housing portion is positioned out of view
of the automobile operator generally under the hood 36 while
portion 15B is mounted on the dash 40, for example, in view of the
automobile operator. The wiper motor 44 is interconnected to the
wiper blades 48, through conventionally known linkage 46 and
therefore, no detailed explanation of the linkage is included
herein.
Referring now specifically to FIGS. 3 and 4, a schematic diagram of
the inter-connections of the various elements of an automobile
wiper motor control system 10 is shown in FIG. 3 and a typical
printed circuit type sensor 12 is shown in FIG. 4.
The moisture sensor 12 is comprised of a plurality of side-by-side
positioned exposed conductive elements 50. The spacing of these
elements can be varied according the the moisture anticipated, or
the amount of impurities within the expected moisture. The elements
50 have a width for example of from 1.0 to 100 mils. Typically the
elements will be from 15 to 62 mils in width and spaced from 15 to
62 mils apart. The width of the conductive elements and their
spacing is not critical and can be varied and still be utilized
successfully to practice this invention. The elements 50 are
generally partially disposed within an insulation medium such as
flexible plastic and the like. Typically flat strap harness
material well known by the electronic art is satisfactory. The
sensor 12 is adhered to the outer surface of the windshield with
the exposed conductive elements 50 being positioned for
encountering a wiper blade 48 during its normal to-and-fro sweep.
Although, it is anticipated that only one wiper blade of a two
wiper blade conventional automobile windshield wiping system will
encounter the sensor 12 in its pass, both wipers' blades could
encounter the sensor 12 in their sweep path without altering the
operation of the automatic wiper motor control system of this
invention.
Each element 50 of the sensor 12, nine shown for the purpose of
explanation, more or less could be employed, is connected to a
separate output of a multiplexer 52. A second multiplexer 54 is
connected to each elements 50 in the same manner as multiplexer 52.
The multiplexers 52 and 54 are interconnected according to the
manufacturers specifications so that one of the adjacent pairs of
elements 50 are connected through a 100K ohm resistor 51 to a
positive DC voltage source 56 to multiplexer 52 and the other one
of the adjacent pair is connected to the output of multiplexer 54.
It should be understood that the adjacent elements in a normal dry
condition appear as an open circuit between the two multiplexers,
preventing voltage from source 56 from being present on the output
of the multiplexer 54. The amount of moisture on adjacent elements
50 and the amount of impurities in that moisture present determine
the level of voltage present at the output of the multiplexer 54
for any given moisture condition.
As the moisture accumulates on the sensor, each pair of adjacent
elements 50 in turn provide a voltage level at the output of the
multiplexer 54. This voltage level is stored in a capacitor 57 of
10 micro farads. This stored voltage in capacitor 57 is continually
bleed to ground through a resistor 58 of 470K ohms. The theory is
that when sufficient moisture accumulates on the sensor 12 between
wiper blade sweeps, the capacitor will be sufficiently charged to
overcome the bleed off through the resistor 58 and provide a
voltage level at the inverting input of a voltage comparator 60.
The voltage comparator 60 has its non-inverting input connected to
the DC voltage source 56 through a 22K ohm resistor 62, a 3.3K
resistor 63, and a 100K ohm potentiometer 64 to ground. The
potentiometer 64 adjusts the desired level of DC voltage at the
non-inverting positive input of the voltage comparator 60 in
comparison to the DC voltage at the inverting input. The operation
of the system sensitivity control will be hereinafter
explained.
A second voltage comparator 66 which also has its inverting input
connected to the output of the multiplexer 54 and its non-inverting
positive input connected to the common connection between resistors
62 and 63. The output of the voltage comparator 60 is connected to
the DC voltage source 56 through a resistor 68 of 100K ohms as is
comparator 66 through a resistor 70 of 100K ohms.
Oscillator 16 comprises a pair of buffer inverters 72, a resistor
74 of 10K ohms, a resistor 76 of 27K ohms, and a capacitor 78 of
0.22 micro farads. The oscillator output is connected to clock
terminal A of one portion of a dual up counter 80. The three
outputs of this position of the dual up-down counter 80 are
connected to the sequence control of the multiplexers 52 and 54.
The reset terminal of this portion of the dual up-down counter 80
is connected to ground potential. The enable of the second or other
portion of the dual up counter 80 is connected to the DC voltage
source 56. The clock terminal B of the up counter 80 is connected
to a fourth output terminal of the first section of the dual up
counter which also provides a clock input to a flip-flop circuit
82.
The output of the voltage comparator 60 is also connected to a
terminal of an And gate 84 and an And gate 82 and the other inputs
to the last mentioned And gates are provided from the DC voltage
source 56 and the output of the wiper blade position sensor 20. The
wiper blade position sensor output is also connected to the DC
voltage source through a resistor 88 of 10 Kohms.
Outputs from the other half of the up counter 80 are each connected
to one input of four inverters 90-96. The outputs of each of these
inverters are connected to the cathodes of light emitting diodes
(LEDS) 98-104 respectively through associated resistors 106-112 of
680 ohms. The anodes of the LEDs are connected to the DC voltage
source 56.
The reset terminal of the flip-flop circuit 82 is connected to one
end of a resistor 114 of 470K ohms and to one side of a capacitor
116 of 1 micro farad. The other end of resistor 114 is connected to
ground and the opposite side of capacitor 116 is connected to the
DC voltage source 56. The inverted output of the flip-flop circuit
82 is connected to the reset terminal of one of the counter
sections of the dual up counter. The non-inverted output of the
flip-flop circuit 82 is connected to the base of a transistor 118
through a resistor 120 of 1.8K ohms. The set terminal of the
flip-flop circuit 82 is connected to ground. The output of the And
gate 84 is connected to the "J" input and the output of the And
gate 86 is connected to the "K" input of the flip-flop circuit
82.
The output of the voltage comparator 66 is also connected to the
base of transistor 122 through resistor 124 of 2.2K ohms. The
emitter of transistor 122 is connected to the DC voltage source 56
and the collector is connected through the wiper motor speed relay
coil 126 to ground. A diode 128 is connected across the coil 126.
The relay coil operates to close a normally open relay switch 130
when the transistor 122 conducts. The relay switch 130 provides
voltage to the high speed winding of the dual speed wiper motor 44.
Dual speed wiper motors of this type are commonly employed on
modern automobiles.
The emitter of the transistor 118 is connected to ground and the
collector is connected to one side of relay switch activating coil
132 and a diode 134. The other end of the coil and diode are
connected to the DC voltage source 56. A relay switch 136 provides
operating voltage to the low speed winding of wiper motor 44
through a two pole/two throw switch 138 which is manually
positionable in either the auto position wherein the automatic
wiper motor system is in control of the wiper motor or in the
manual position wherein the normal vehicle wiper motor control
controls the wiper motor. When in a manual operation mode, DC
voltage is applied through a 680 ohm resistor 142 and a series LED
144.
The term DC voltage or DC voltage source 56 throughout the
discussion refer to the vehicle battery which can be 6 or 12 volts
DC the negative pole of which is referred to as ground. The
multiplexer 52 and 54 shown are cos/mos analog multiplexers
typically of the type CD 4051 or an equivalent thereto. The
inverter buffers 72 and 90-96 are type CD 4049 or equivalent. The
dual up counter 80 is an CD 4520 or equivalent. And gates 84 and 86
and flip-flop circuit 82 are a CD 4096 or equivalent. The voltage
comparators 60 and 66 are single dual voltage comparator circuit's
CA 3290 or are two single equivalents or an equivalent dual unit.
Transistor 118 is a 2N3569 or equivalent. Transistor 122 is a
2N3638 or equivalent. The wiper blade position sensor 20 can be an
optical device, hall effect transistor, magnetic switch, reed
switch, waterproof switch, or the like which is activated by wiper
contact or sensing.
The various solid state circuits mentioned above have terminals or
connections identified in the same manner as those specific
circuits noted above and shown in the various drawing figures. It
should be understood that equivalent circuits may have differently
identified terminals or connections and would be connected to
equivalent circuit connections in accordance with the circuit
manufacturer's specifications.
The resistors used throughout are typically one quarter watt carbon
resistors of approximate value as noted. The potentiometer 64 is a
one watt carbon type. The capacitors are chosen to operate safely
at 12 volts DC. The LEDS operate on DC voltage and may have any
desirable color or colors.
BRIEF DESCRIPTION OF THE CIRCUIT OPERATION
The multiplexer 52 and 54 are analog type multiplexers. The eight
channels of each multiplexer are selected by a binary 0 through
binary 7. The binary code is produced by the dual binary counter
80. The half of the binary counter that selects the multiplexer
channels is clocked by the oscillator made up from inverters 72,
the resistor 74, 76 and capacitor 78. If, for example, a water
droplet is deposited across two adjacent conductive sensor strips
50, the multiplexer in its sequencing will select these conductive
sensor strips. For the brief moment that these conductive sensor
strips 50 are selected, there is a current pattern therebetween
from the DC voltage source through resistor 51, through the
multiplexers to the high side of capacitor 57 thereby charging
capacitor 57. As the multiplexers switch, other pairs of conductive
sensor strips 50 which have rain or moisture therebetween conduct
therebetween in the same manner. Each current path thereby provided
will increase the charge on capacitor 57. As the amount of rain or
moisture intensity diminish the voltage applied to the capacitor 57
will further diminish due to the constant discharge through
resistor 58 until a voltage level below the pre-selected voltage
level required to operate the wiper motor will result. The voltage
charge on capacitor 57 is continually compared with a preset
voltage level on the positive inputs of voltage comparators 60 and
66. The type CA 3290 comparators shown are open-collector devices
and require pull up resistors 68 and 70. Two threshold voltage
levels for comparison are provided by the voltage divider
comprising resistors 62, 63 and potentiometer resistor 64. When the
voltage level at the inverting input of comparator 60 is more
positive than the voltage level on its non-inverting input, its
output becomes a logic "0". A logic "0" at the output indicates
water present across sensor strips 50 sufficient to require wiper
blade action. For the circuit to now produce a signal that
activates the wiper motor 44, flip-flop circuit 82 must have proper
inputs. The output from voltage comparator 60 provides an inputs.
The output from voltage comparator 60 provides an input to the
inverting input of the And gate 84 which must be a binary "0" and
the other two inputs to the And gate 84 must be a binary "1". One
of the two inputs is always "1" since it is connected directly to
the DC voltage source 56 and the other is initially a binary "1"
until the wiper blades reach the wiper blade sensor position. The
output of the And gate 84 is now binary "1" Under these conditions
a binary "1" will appear at the non-inverting output Q of flip-flop
82 if the clock input to the flip-flop makes a transition from
binary "0" to binary "1" when the Q3 output of the first half of
dual binary counter 80 makes a binary "0" to binary "1" transition
and if the output of And gate 86 is a binary "0". When the
non-inverted output Q of flip-flop 82 is a binary "1" the
transistor 118 will be biased on. Transistor 118 will conduct from
emitter to collector and provide a return path for the relay switch
activating coil 132. The diode 134 across the coil 132 is used to
squelch the reverse electro motive force (EMF) produced by the coil
field collapsing when the relay is de-energized. When the contacts
of the relay switch make or close, the wiper motor 44 is activated.
When the non-inverted output Q of flip-flop 82 is a binary "1" the
inverted output thereof is a binary "0". This inverted output
removes the reset pulse from half of the dual binary counter 80 and
the clock pulse is now provided from the other half of the same
dual up counter. The outputs from one half of the binary counter
supply inputs to buffer inverters through their associated resistor
sequentially illuminating LEDs 98-104. This provides indication
that the multiplexer is operative and a pleasurable light show for
the vehicle occupants will be displayed on control portion 15B.
When the wiper motor is activated, the wiper blade or blades will
continually wipe across the sensor strips 50, removing the rain
drop or drops that caused the prior wiper activation.
The wiper action termination sequence is as follows. When the wiper
blade or blades reach the wiper position sensor 20, the position
sensor will produce a binary "0" at its connection to the And gates
84 and 86. This is the only position of the wiper blade or blades
that the automatic wiper motor control activation can make a
decision to de-activate the wiper motor or not. This decision
depends on the moisture level between the sensor strips 50 of the
sensor 12 and the binary voltage level present at the output of the
voltage comparator 60. If the output or voltage level of comparator
60 remains a binary "0" and a binary "0" to "1" transition occurs
at the clock input of the flip-flop 82, operation of the wiper
motor will continue. If, on the other hand, drops have not
reaccumulated across the sensor strips, the output of the voltage
comparator 60 will change from a binary "0" to a binary "1" causing
the output of the And gates 84 and 86 to provide a binary "0" to
the input to flip-flop 82. Also under these conditions, the output
of And gate 86 will be a binary "1" causing the non-inverted output
of flip-flop 82 to change from a binary "1" to a binary "0" when a
binary "0" to "1" transition occurs at the clock input to flip-flop
82. At this time transistor 118, will be turned off which
terminates the operating voltage to the wiper motor, ie. switch 136
returns to its normally open condition. The wiper motor will not
normally stop when the wiper blade or blades are positioned in the
middle of a sweep as the park switch associated with a conventional
wiper motor will maintain motor operation until the wiper blade
home position is reached. Once the wiper blade or blades start
moving toward its home position, the wiper position sensor 20 will
change from a binary "0" to a binary "1". This binary "1" forces
the output of And gate 86 to switch from a binary "1" to a binary
"0" at the same time the other two inputs of And gate 84 are at a
binary "1" causing the output of binary "0" at And gate 84. So now
the output of the voltage comparator 60 depends on whether or not
moisture has re-accumulated between the sensor strips 50 of sensor
12. If moisture re-accumulates after the decision to terminate
wiper motor action has been made, the voltage comparator 60's
output will change from a binary "1" to a binary "0" and with the
conditions above being conductive, wiper motor action resumes in
the hereinbefore explained manner. No interruption of wiper action
will be observed under these conditions because of the action of
the home-park switch. When the automatic controls of the invention
terminate wiper motor action the inverted output of the flip-flop
82 will cause the dual up counter to reset, terminating the output
to buffer/inverters 90-96 and thereby terminating the sequential
illumination of LEDS 98-104.
When the voltage at the inverting input of the voltage comparator
66 is more positive than the voltage level from the DC voltage
source through resistor 62, as set by potentiometer resistor 64 and
resistor 63, the output of the voltage comparator 66 will change
from a binary "1" to a binary "0". The presence of the binary "0"
indicates that a high accumulation of moisture or water is present
on sensor 12. This condition will cause transistor 122 to conduct
from emitter to collector. This conduction provides a return path
for the second wiper motor speed relay coil 126, closing the relay
switch 130 associated therewith activating the conventional high
speed windings of the wiper motor 44. Diode 128 serves the same
purpose as the other diode 134 hereinbefore mentioned.
The capacitor 116 and resistor 114 form a power-on-reset for
flip-flop 82 so that the wiper motor is off upon initial power up
of the automotive wiper motor circuit. The power-on-reset occurs
when the vehicle is started (ignition on) if the manual/automatic
switch 138 (a dual pole double throw type) has previously been
moved from the manual to automatic position shown. If the vehicle
has previously been started with switch 138 in the manual position,
selecting the automatic mode of switch 138 will cause a
power-on-reset to occur. The switch removes the DC voltage source
56 from the wiper motor circuit when the switch 138 is in the
manual mode and also when the manual mode is selected the automatic
portion of the switch 138 opens causing the current path to the
wiper motor to be open. The automatic wiper control circuit is now
removed from the wiper motor's normal circuit. Moving the switch
138 from auto to manual causes LED 144 to illuminate.
Throughout the above discussion an automobile windshield wiper
motor system has been used to describe an embodiment of this
invention. It should be understood that the automobile environment
is not intended to limit the use of the invention as obviously, the
invention can be employed in conjunction with any window wiper
system employing a motor, linkage and blade(s).
The above described embodiment of the invention is merely
descriptive of its principles and is not to be considered as
limiting in any manner. The scope of the invention instead shall be
determined from the scope of the following claims including their
equivalents.
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