U.S. patent number 3,894,250 [Application Number 05/453,349] was granted by the patent office on 1975-07-08 for hall cell position sensor for outboard drive apparatus.
This patent grant is currently assigned to Brunswick Corporation. Invention is credited to James R. Hager, Hugh E. Riordan.
United States Patent |
3,894,250 |
Hager , et al. |
July 8, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Hall cell position sensor for outboard drive apparatus
Abstract
Apparatus for power positioning and holding of an outboard
marine drive includes a manual trim angle selection input signal
generator. A position sensitive signal generator in the form of a
Hall cell or a resistor is secured on the gimbal ring unit with a
movable element set in accordance with and by the movement of the
marine drive. A comparator provides a pair of output signals in
accordance with the relative magnitude of the two signals and
depending upon whether drive is to be raised or lowered. The output
signals are similarly connected through amplifying and switch
isolating circuitry to actuate an electric motor and hydraulic pump
unit to raise or lower the stern drive until the position sensor
and the manual input are nulled. A slight dead band maintains
stable operation as the stern drive is moved to a new trim
position. A fail-safe circuit prevents malfunctioning if the
sensing system open circuits.
Inventors: |
Hager; James R. (Fond du Lac,
WI), Riordan; Hugh E. (West Bend, WI) |
Assignee: |
Brunswick Corporation (Skokie,
IL)
|
Family
ID: |
26986936 |
Appl.
No.: |
05/453,349 |
Filed: |
March 21, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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329726 |
Feb 5, 1973 |
3834345 |
|
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Current U.S.
Class: |
327/511; 440/1;
114/144A; 440/53 |
Current CPC
Class: |
B63H
20/10 (20130101); G05D 3/1409 (20130101) |
Current International
Class: |
B63H
20/00 (20060101); B63H 20/10 (20060101); G05D
3/14 (20060101); H01r 005/00 (); B63b 041/00 ();
B60q 001/26 () |
Field of
Search: |
;307/278,309
;114/144A,144R,235B ;115/34A,34R,41R,41HT |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Miller, Jr.; Stanley D.
Attorney, Agent or Firm: Andrus, Sceales, Starke &
Sawall
Parent Case Text
This is a division of application Ser. No. 329,726, filed Feb. 5,
1973 and now U.S. Pat. No. 3,834,345.
Claims
1. A Hall cell sensor for producing a sine wave signal proportional
to tilt positioning of a pivotally mounted outboard drive unit,
comprising Hall cell having a tubular housing having attachment
means for supporting the housing in fixed relation with respect to
the outboard drive unit, an annular magnetic means adjacent to said
Hall cell and having attachment means for securing the magnetic
means to the outboard drive unit coaxially with the axis of
rotation of the drive unit, said magnetic means being diametrically
magnetized to produce an operative flux field varying as a sine
wave with angular orientation.
2. The Hall cell sensor of claim 1 wherein at least one of said
attachment means is adjustable to produce offset of the cell
voltage.
3. The Hall cell sensor of claim 1 including a differential
amplifier connected to the output of the Hall cell and establishing
a pair of floating output lines, a dual input operational
amplifier, a pair of emitter follower circuits connecting the pair
of floating output lines to the operational amplifier, said
operational amplifier including a resistivecapacitive feedback
network, a resistive bias adjustment to the Hall cell to establish
a selected offset of Hall cell voltage, a regulated voltage supply,
and a low-pass filter network connecting said Hall cell and said
amplifier to the regulated voltage supply.
4. The Hall cell sensor of claim 1 wherein said housing includes a
recess within which said Hall cell and a signal processing circuit
components are mounted and interconnected, a potting material
filling said recess to support said cell and circuit components,
the housing having a wall adjacent the magnetic means which is
non-magnetic.
5. The Hall cell sensor of claim 4 wherein said wall is formed of a
solid material which is non-magnetic.
6. The Hall cell sensor of claim 4 wherein said circuit components
include a differential amplifier connected to the output of the
Hall cell and establishing a pair of floating output lines, a dual
input operational amplifier establishing a single ended output
signal, a pair of emitter follower circuits connecting the pair of
floating output lines to the second operational amplifier.
Description
BACKGROUND OF THE INVENTION
This invention relates to automatic positioning drives for angular
positioning of an outboard drive unit.
Outboard propulsion drive units are widely employed for marine
drives particularly of the smaller pleasure boats and the like.
Such units are preferably connected to the transom of the boat and
mounted for angular orientation about a vertical axis for steering
purposes and about a horizontal axis to permit optimum location of
the propulsion unit in the water for optimum driving conditions.
Hydraulic systems have been advantageously applied to power trim
positioning of the outboard propulsion units. For example, U.S.
Pat. Nos. 3,434,448 and 3,434,449 disclose hydraulic systems
wherein a piston and cylinder means is coupled to a stern drive for
selectively positioning and holding of the stern drive unit in
various angular orientation about a horizontal axis. The hydraulic
system is driven from a suitable electric motor driven pumping unit
having an appropriate hydraulic control system for raising and
lowering of the stern drive unit. Generally such systems have
employed a manual control at the steering station which the
operator continuously operates until such time as the motor is at a
desired position. The prior systems have therefore relied on the
operator sensing an optimum condition. Alternatively, meters have
been electrically coupled to the stern drive unit and positioned in
accordance with the angular drive trim position. The variable
resistor unit is connected in the circuit of a meter mounted
adjacent to the operator and provides a visual indication of the
angular setting time position.
Although the prior art devices have permitted power trim
positioning systems, they have relied upon the direct attention of
the operator either through a subjective sensing of optimum motor
positioning, visual viewing of the motor position or of a meter
with adjustment of the trim until an optimum condition is believed
to have been established. Thus, the operator's attention is, in
essence, divided between the setting of the trim control and the
operation of the propulsion unit. Further, in such systems, the set
trim position changes during operation such as a result of
interaction with the water and/or objects in the water or as a
result of minor hydraulic leakage. For example, rapid acceleration
or running over a stump or the like may cause the marine propulsion
unit to move from the set position without necessarily returning to
the set position after disturbing forces are removed. The operator
must, therefore, provide a more or less continuous attention to the
trim run positioning of the propulsion unit. This may require the
operator's attention under conditions representing a hazardous
diversion from the driving of the boat.
SUMMARY OF THE PRESENT INVENTION
The present invention is particularly directed to a power lift
system for automatically setting the marine propulsion unit in a
selected trim position as a result of a single angle selection
input, with the system holding the trim position for all normal
operating conditions. Generally, in accordance with the present
invention, the automatic trim system includes a manually actuated
signal generator for producing a signal related to a desired trim
angle. An automatic sensing unit is coupled to a power unit and
generates an output signal proportional to the angle position with
respect to a reference. The two signals are connected to a
comparator, the output of which provides an output for raising and
lowering of the propulsion unit. The comparator preferably provides
a pair of on-off signals for selectively raising and lowering of
the marine propulsion unit. Thus, the one signal actuates a power
lift mechanism to raise the stern drive and the opposite signal
correspondingly actuates the power lift unit to lower the marine
propulsion unit. The drive unit is thus automatically positioned
until a null signal condition is established, at which time the
drive unit is held in the preset desired position. If the trim
angle should be changed due to any operating condition, the system
will automatically reposition the drive unit to the preset
condition.
In accordance with a further novel aspect of the invention, the
apparatus is provided with a time delay which will be sufficient to
keep the system from self-correcting itself under minor
disturbances such as those associated with wave bounce and the
like. The apparatus may further include a pressure responsive
cutout which opens the drive position circuit if a high pressure is
applied to the propulsion means, such as encountered if passing
over a log. This permits the standard "log jumping" with subsequent
automatic reconnection of the trim control. Further, electronic
circuitry can be employed to minimize the power consumption by the
control system and thereby adapt the unit to the usual marine drive
system.
The system, in accordance with a particularly novel aspect of the
present invention, includes a dead band selected in accordance with
the coasting characteristics of the drive unit including the
hydraulic system. The dead band is selected to prevent overlap
between adjacent selected angles.
In accordance with a further novel aspect of the present invention,
the position sensor is a Hall cell sensor including a Hall cell
transducer in combination with a magnetic member, with the cell and
magnetic unit mounted for relative movement as a part of the drive
unit. The Hall cell sensor transduces the sine wave of flux density
to a related sine wave of voltage in response to the relative
angular orientation of the Hall cell and the magnetic unit. The
output is amplified and preferably buffered with a pair of emitter
follower transistors to produce a double-ended output sufficient to
drive an operational amplifier, the output of which is connected as
an input to a comparator amplifier. The sensor circuitry includes
filtering means to attenuate any radio frequency signal resulting
from the ignition system of the marine propulsion unit and an
offset adjustment means to adjust the offset of the Hall device.
The system is preferably powered from a suitable voltage regulator
means.
The Hall cell amplifier and emitter follower circuit may
advantageously be formed as an integrated circuit unit with the
Hall cell mounted in fixed relation to the propulsion drive unit. A
doughnut shaped magnet is secured to the movable portion of the
stern drive, for example, to the pivot shaft mounting and is
rotated about the Hall cell to impress an operative flux upon the
Hall cell which varies as a sine wave with the rotation or angular
orientation of the propulsion drive unit. The comparator and drive
circuitry may be separately mounted in a suitable control mounted
inboard of the motor of the boat. Thus, in the preferred circuitry
an operational amplifier means including a separate pair of
operational amplifiers is connected as a comparator to compare the
output of the Hall cell sensor and a preset DC signal. The output
of one operational amplifier is connected to selectively drive an
up switching amplifier and the output of the other operational
amplifier is connected to drive a down switching amplifier. The
outputs of the switching amplifier are connected through suitable
relays or other switching means to reversibly drive an electric
motor. The electric motor, in turn, is coupled to reversibly drive
a hydraulic pump unit for corresponding raising and lowering of the
propulsion drive unit until such time as the position sensing
signal is nulled with the input signal. The control circuitry may
further include a stabilizing network to eliminate the effects of
vibration and to insert the desired angular dead zone which will
permit the drive unit to coast past the equilibrium position by
approximately one degree in either direction without
re-energization of the system.
Further, as previously noted, the U.S. Pat. 3,641,965 discloses a
resistive sensor for providing an output signal proportional to the
angular orientation of the drive unit. As noted therein relatively
simple and inexpensive linear resistors are preferably employed.
However, the output as noted is linear with the position and,
consequently, such an inexpensive resistor does not provide the
required sine wave signal compatible with a system employing a Hall
cell sensor. Applicant has found, however, that for the limited
angular positioning required of a marine propulsion unit, a linear
resistor in series with an appropriate fixed resistor generates a
variable voltage which approaches a sine wave voltage versus
angular displacement and is such as to permit highly satisfactory
operation as the input to the Hall cell signal processing circuit.
The resistive sensitive system may be desirable to minimize the
expense and to avoid certain temperature stabilization required
with Hall cell units.
As the sensing systems are preferably mounted to the propulsion
unit there is a danger that the circuit will become open circuited
due to wear or water contamination, corrosion or the like,
particularly where the resistive sensing network is employed. Under
such conditions the voltage may rise to provide a turn-on signal to
the power lift means tending to lower the propulsion drive unit to
its maximum down position with no means for the operator to return
it to a higher position. This can obviously create an extremely
dangerous operating condition particularly when the boat is under
power. The present invention desirably provides a safety circuit to
positively prevent the operation of the lowering power circuitry
under open circuit conditions. The safety circuit in accordance
with a further novel aspect of the present invention may employ a
Zener diode means or the like connected to sense the input voltage
from the resistance position sensor and actuate an interlock switch
such as a transistor in response to an open circuit condition. The
interlock switch positively prevents energizing of the lowering
circuitry. The same voltage signals holds the lifting circuit in
the preferred construction. The safety circuit preferably includes
an integration means such as a resistor-capacitor to produce a
delay in the actuation of the fail-safe circuit and thereby permit
a momentary open circuit condition. Thus, in the resistance sensor
element, the wiper may momentarily create an open circuit condition
when moving from one winding turn to the next and erroneously
operate the safety circuit if a delay means is not introduced.
The present invention thus provides a reliable automatic drive for
accurately locating and positioning of an outboard marine
propulsion drive unit.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings furnished herewith illustrate preferred constructions
of the present invention in which the above advantages and features
are clearly disclosed as well as others which will be readily
understood from the following description:
In the drawings:
FIG. 1 is a side elevational view of an inboard-outboard drive unit
mounted on the transom of a partially shown watercraft, with
various trim positions shown in phantom line illustration;
FIG. 2 is a fragmentary rear view of the watercraft and stern drive
unit shown in FIG. 1;
FIG. 3 is an enlarged fragmentary side elevational view of the
stern drive unit shown in FIG. 1 more clearly illustrating the Hall
cell mounting;
FIG. 4 is a vertical section taken on line 4-4 of FIG. 3;
FIG. 5 is a block diagram of an automatic trim control system
constructed in accordance with the present invention and applied to
control a stern drive unit such as shown in FIG. 1;
FIG. 6 is a schematic circuit diagram of a system corresponding to
that shown in FIG. 5 and employing a Hall cell position sensor
mounted as a part of a stern drive unit shown in FIG. 1;
FIG. 7 is a schematic circuit similar to FIG. 3 illustrating an
embodiment employing a resistance sensor and a novel fail-safe
circuit; and
FIG. 8 is a schematic circuit of a simple differential relay
embodiment.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENT
Referring to the drawings and particularly to FIG. 1, an outboard
propulsion unit or assembly in the form of a stern drive unit 1 is
shown mounted on the transom 2 of a partially shown watercraft 3.
The stern drive includes a lower drive unit 4 and a bracket
mounting assembly 5 for movably mounting and supporting of the
drive unit from the transom 2. The bracket assembly 5 includes an
intermediate gimbal ring 6 which pivotally supports the drive unit
1 upon a generally transverse horizontal axis 7 for selective tilt
movement of the unit in a generally vertical plane. The gimbal ring
6 is in turn pivotally supported on a generally vertical axis 8 by
the outer transom bracket 9 to provide for and permit movement of
the drive unit 4 in a generally horizontal plane for purposes of
steering the movement of the watercraft 3.
The drive unit 4 more particularly includes the usual propeller 10
which is drivingly connected to an engine 11 mounted inboard of the
watercraft 3. The propeller 10 is selectively rotatable in opposite
directions in accordance with operation of suitable reversing gear
positioning means not shown to provide for a corresponding forward
and reverse thrust respectively for the watercraft 3. Further, the
drive controls include a suitable remote speed and directional
control unit connected by an electrical, mechanical cable system or
the like not shown to permit convenient location of the operation,
for example, adjacent a forward control station 12 of the
watercraft 3. In addition, hydraulic power means are provided for
supplying hydraulic liquid to a pair of cylinder-piston means 13
connected to the opposite sides of the stern drive unit 1
functioning as hydraulic shock absorbing means as well as stern
drive angular positioning or trim positioning power means. Thus, as
more fully described in the previously referred to U.S. Pat. Nos.
3,434,448 and 3,434,449, the piston-cylinder means 13 are connected
to a hydraulic gear pump 14 which is reversible driven by a
reversible electric motor 15 to selectively supply liquid to the
opposite sides of the cylinder-piston means 13, thereby permitting
the powered extension and retraction thereof with a corresponding
angular orientation or positioning of the stern drive unit 1 about
the horizontal axis 7. As the above mounting and positioning of the
stern drive may take any desired form and construction, no further
description thereof is given other than that necessary to clearly
describe the present invention.
In the operation of a watercraft which is driven from an outboard
propulsion means such as a stern drive unit, the watercraft is
preferably started with the drive unit 1 in the lowered depending
full line position shown in FIG. 1. This aids the movement of the
boat to the plane position. However, when the boat is on a plane,
it is desirable to re-position the drive unit 1 further outward for
maximum efficiency and speed as disclosed in the previously
referred to U.S. Pat. No. 3,641,965. Under normal operating
conditions various trim angles might be desirably employed.
Further, the drive unit 1 may be raised upwardly to maximum
position for trailing or low power operation. The present invention
is particularly directed to provide an automatic drive and
positioning control system which will permit selection of a given
angle and the holding of such given angle automatically and in
response to the operator merely actuating a suitable input
positioning device to a selected angle position without the
necessity for continued attention and monitoring of the system.
Thus, generally, in accordance with the present invention, a trim
angle selection unit 17 is provided adjacent to the operating
station 12 and may conveniently be in the form of a multiple switch
unit adapted to select any one of a plurality of preselected angles
between a reference zero position and a maximum raised position.
Thus, for example, a highly satisfactory automatic control system
has been constructed providing for the selection of the seven
different angles of 0.degree., 3.5.degree., 7.0.degree.,
10.5.degree.,15.degree., 22.degree. and 44.degree.. Although
pushbuttons, levers or position selection means can be used, a
satisfactory selection unit 17 has been constructed with a rotary
switch having an input knob 18 that could be moved to any one of
the angle positions. The trim control system further includes a
stern drive position sensitive signal means 19 coupled to the unit
1 and the signals of the selection unit 17 and signal means 19 are
compared and processed to automatically and directly establish the
angular movement and positioning of the stern drive unit 1 and is
continuously operative to maintain such trim angle position.
Referring particularly to FIG. 5, a block diagram of the automatic
trim control system of the invention is illustrated in which the
manual input control 17 is shown providing one input to a
comparator amplifier 20, the opposite input of which is connected
to the position sensor 19. The output of the position sensor is a
signal directly related to the angular positioning of the drive
unit 1 and of a character related to the signal from the unit 17.
The comparator 20 compares the two signals and provides a lift
signal or a drop signal at a pair of corresponding lines 21 and 22,
depending upon the relative magnitude of the two input signals.
Thus, if there is a difference between the selected angle and the
actual angle, a signal will appear at one or the other of the two
output lines. These signals are similarly processed and in
particular the control signal is amplified through similar
amplifiers 23 and 23a and connected to actuate and up-relay 24 or a
down-relay 25. The relays 24 and 25 in turn connect power to the
electric motor 15 to reversibly operate the electric motor in
accordance with the operation of the relays to thereby reversibly
drive the hydraulic pump 14. The control system will automatically
establish the trim angle and will reset the trim angle if it is
changed for any reason under operation; for example, due to rapid
acceleration, running over a stump or the like. The operator can
select any one of the given angles without a great deal of
attention or distraction from the normal operation of the
watercraft.
Referring particularly to FIG. 6, schematic circuit diagram of an
automatic trim control system is shown employing a Hall cell
position sensing unit coupled to the stern drive unit, as shown in
FIGS. 1-4 and functioning as a position sensor.
The Hall sensor 19 preferably is constructed as an integrated Hall
cell circuit unit having a Hall cell 27 connected to a closely
regulated power supply 28. A resistor-capacitor network 29 connects
the supply 28 to the battery 29a and functions as a low pass filter
to attenuate radio frequency that might be produced by the ignition
system, not shown. Thus, in a practical application, the Hall cell
was connected to a 5.6 volt regulated voltage.
The output of the Hall cell 27 is connected to a differential
amplifier 30 which produces a double-ended output, each of which is
coupled through a buffering emitter transistor 31 to a second
amplifier 32 to provide an amplified voltage signal related to the
Hall cell voltage at the output line 32a. A pair of resistors 33
one of which is made adjustable, is connected to the input of the
differential amplifier 30 to adjust the offset of the Hall device
27. The several circuit elements of the sensor 19 are, as noted,
preferably formed as a single integrated circuit.
The output of the Hall cell 27 is controlled by an annular
permanent magnet 34 which as shown diagrammatically in FIG. 6 is
polarized diametrically of the magnet on a line generally normal to
the diametrical line through the Hall cell. The magnet 34 is
mounted for angular rotation about its own axis and is angularly
oriented with respect to the Hall cell 27, as more fully shown in
FIGS. 3 and 4. The effective component of the flux impressed upon
the Hall cell 27 changes or varies in accordance with a sine wave
function as the angular orientation or position of the magnet 34
with respect to the Hall cell 27 changes. The Hall cell 27 thus
transduces the sine wave of magnetic flux to a corresponding sine
wave voltage signal.
As illustrated in FIGS. 3 and 6, for the lowermost position of the
drive unit 1, the Hall cell 27 is aligned with the periphery of the
magnet 34 at essentially ninety degrees to the north and south
poles. Although this is not the position of maximum flux and
therefore signal level, it is the position of the maximum rate of
signal change for any given small angle movement. This is
particularly advantageous when applied to positioning of a marine
drive unit, which is normally positioned between a vertical or
0.degree. position and a raised 55.degree. position. The angular
positioning between approximately 0.degree. and 15.degree. is quite
significant in the propulsion of an outboard unit and consequently
maximum accuracy is desired in that range. The sine wave voltage
signal provides maximum voltage change per degree at the zero
crossover axis as a result of the maximum slope and almost linear
characteristic of the wave at that point. This also permits use of
a relatively narrow voltage range; for example, 2.5 volts for the
zero degree angle setting to 8.2 volts for a maximum or 55.degree.
angle setting. Although the voltage change per degree of angular
movement in the upper range or last 15.degree. is substantially
less, the angular position is not as significant for operating the
propulsion means and is therefore readily employed.
The output of the cell 27 is amplified and coupled through the
emitter followers 31 to prevent loading of the sensor circuit. The
amplified output is impressed upon a second amplifying stage 32
through series coupling resistors 35 and 36 and a resistor 37 to
ground which sets the source impedance of the second amplifying
stage. A paralleled RC feedback network includes a variable
resistor 38 and a fixed capacitor 39. The variable resistor 38
permits adjustment of the gain of the second amplifying stage while
the feedback capacitor limits the band width of the operational
amplifier and protects it from spurious oscillation.
The output is thus an amplified signal, taken with respect to
ground, which is directly related to the angular orientation of the
stern drive unit 1 with respect to the zero or reference
position.
The output is applied as one input to the comparator 20, which, as
shown in FIG. 6, is preferably an operational amplifier means
including a pair of operational amplifiers 40 and 41 for driving of
the respective switching amplifiers 23 and 23a. Each of the
amplifiers 40 and 41 is similarly constructed and includes a
corresponding non-inverting input 42 and 43 and an inverting input
44 and 45. The non-inverting input 42 and the inverting input 45
are connected through individual series coupling resistors 46 and
46a to the ungrounded output of the angle section unit 17.
Individual coupling resistors 47 and 47a connect the inverting
input 44 and the non-inverting input 43 to the sensor 19. The
sensor connected input terminals 43 and 44 of amplifier 40 and 41
are further connected to ground through suitable bypass capacitors
48 which, with the coupling resistors define low pass signal
filters in the input circuit.
The selection unit 17 includes a voltage dividing network including
a fixed resistor operational connected to the battery 29a with a
regulated power supply 50 providing a regulated voltage to the
selection unit 17 and the comparator circuit 20. The opposite leg
of the voltage dividing network includes the rotary switch assembly
having a movable contact 51 selectively engaging one of seven
different contacts 52, related sequentially to the trim angles
0.degree., 3.5.degree., 7.degree., 10.5.degree., 15.degree.,
22.degree. and 44.degree. in accordance with the system heretofore
discussed. Each of the contacts 52 is individually connected to
ground via an angle related resistor 53 to complete the voltage
dividing network, with the common connection or junction 53a
between the fixed resistor 49 and the movable contact 51 connected
to the inputs 42 and 45 of the opeational amplifier 40 and 41.
Thus, each of the resistors 53 provides a different voltage
division of the regulated voltage with a corresponding fixed
reference or set voltage input to the operational amplifier. The
sensor and the reference voltages are thus applied to both
operational amplifiers 40 and 41, compared, and an appropriate
output signal generated to null the system by repositioning of the
stern drive unit.
The operational amplifier 40 includes a paralleled R-C feedback
network 54 which interconnects the amplifier output line 55 to the
non-inverting input 44. A similar R-C network 54a interconnects
output line 56 of amplifier 41 to the non-inverting input 45. The
capacitors of the feedback networks 54 and 54a limit the frequency
response of the amplifier in order to prevent a frequency response
high enough to cause positive feedback and unstable operation. The
feedback resistors of the networks 54 and 54a in combination with
the input resistors set the gain of the amplifier which is selected
to be sufficiently high to maintain alternative full on and full
off conditions at the lines 55 and 56 and provide a switching logic
to the drive portion of the power tilt mechanism. A relatively low
voltage appears at lines 55 and 56 with amplifiers 40 and 41 off
and a relatively high voltage appears when such amplifiers are on:
In a practical system, the voltage may change from 2.4 volts to 7
volts.
Thus, selection resistors 53 are selected to maintain the minimum
voltage applied to the operational amplifier well below the low
voltage operating limit at 0.degree. centigrade, to thereby avoid
possible erroneous operation with temperature. The stern drive unit
is a relatively large load and will coast somewhat after a null
condition is created. In accordance with an aspect of this
invention, a dead band is introduced into the input circuit to
allow for such movement. In the illustrated embodiment, a dead band
bias voltage is established at the inverting input 45 of amplifier
41 and at the non-inverting input 42 of amplifier 40. The input 45
is connected by a resistor 57 to the regulated power supply 50
while the noninverting input is connected by a resistor 58 to
ground. The resistor 57 and 58 are selected such that the reference
voltage is offset slightly and results in a slightly premature
cutoff or nulling of the corresponding amplifier. The dead band is
selected in accordance with the coasting characteristics of the
stern drive mechanism and in accordance with a practical
construction permits the stern drive unit to coast past an
equilibrium position by one degree in either direction without
affecting the system.
For example, the reference voltages inserted by resistor 53 may be
selected to vary the input voltage between 2.4 and 7 volts, with
the resistors 57 and 58 causing the actual input voltage to be
offset by 0.1 of a volt. Thus, if the selection unit is set to an
intermediate position with four volts appearing at line 53a, the
voltage at the non-inverting input 42 of the raising operational
amplifier 40 would be 3.9 volts while the voltage at the lowering
operational amplifier would be 4.1 volts. If the sensor output
voltage is, for example, below such level as a result of the drive
unit 1 being located below the select angle, the amplifier 41
remains off. The amplifier 40, however, is driven on because the
inverting terminal 44 is at a lesser voltage than the non-inverting
terminal 42. The unit 1 is driven up and the sensor voltage
increases until a voltage 3.9 volts is impressed on both applifier
40 and 41. Amplifier 41 is off and remains off. This, however,
nulls the output of amplifier 40 which then cuts off and terminates
the positive drive. The drive unit 1 continues to coast toward the
set position and stops. If it coasts slightly past the set position
corresponding to the reference voltage of the selection unit 17,
the offset of such voltage appearing at the opposite terminal
prevents driving of the operational amplifier on, unless of course
the coasting is excessive. In that case, the voltage output of
sensor 19 compared to the set voltage differs by more than the
offset voltage and reverses the drive.
For example, assume the coast is four degrees and thus in excess of
two degrees dead band. The sensor voltage is then 4.3 volts equal
to 3.9 volt cutoff voltage and the additional 0.4 volts for the
4.degree. coast movement. The non-inverting input 43 of the
lowering amplifier 41 is now above the set voltage of 4.1 volts at
the inverting terminal 45. As a result, amplifier 41 turns on and
reverses the drive to properly re-position the drive unit 1.
Generally, the stern drive units of the assignee of this
application are basically of two different varieties. One employs a
relatively hydraulic cylinder means and moves at a relatively fast
angular velocity, with a total angular displacement of about
50.degree.. The other system illustrated employs a somewhat larger
hydraulic cylinder means moving at a somewhat slower angular
velocity but with a total angular displacement of about 56.degree..
This difference in velocity results in a somewhat different amount
of average coast and generally it has been found that the slower
dual drive will stop approximately three-quarters of a degree
before the desired position whereas the single drive will stop at
approximately the desired position with the 2.degree. dead
band.
The amount of coast also depends on the amount of power applied to
the propeller. Thus, with the stern drive trimmed down and under
full forward power, the total coast may be such as to move beyond
the dead band zone. However, with the present invention, the system
will correct itself once and come back within the desired
position.
The total dead band zone of two degrees in the system described is
thus a compromise to adapt the unit to both systems while
maintaining separation of the two adjacent trim settings at
3.5.degree..
The difference in total angular displacement also requires somewhat
of a comprise is a single system is to be applied to all the
drives. Further, some margin of safety must be introduced into the
system in order to compensate for normal manufacturing tolerances
and the like as well as to allow a few degrees between the all down
trim position and the all down mechanical stop. A practical system
was designed for a variation in trim position between zero and
forty-four degrees nominal. As a practical matter, the actual
positions may, as a result of normal manufacturing tolerances and
the like, vary between 40.degree. and 48.degree. from unit to unit.
If close tolerance components are employed for the highest value
sensing resistor as well as the interrelated voltage dividing and
sensing resistors of and for the voltage regulator diode and the
like, the variation can be substantially reduced. Thus, if one
percent tolerance parts were employed, the system could be designed
for nominal displacement of approximately forty-seven degrees with
an expected total variation from unit to unit of about from
46.degree. to 48.degree..
Alternatively, the control circuits could be constructed for each
particular stern drive by a proper selection of the bias resistive
network to the comparator. The highest value position resistor 53
as well as the compensating dead band resistors 57 and 58, for
example, could be properly selected for each design. This, of
course, would require inventory of two separate control circuits,
with the attendant expense and the like. The resistors 57 and 58
thus may be adjusted to provide a desired response to the inputs of
sensor 19 and selective means 17 as applied to the amplifiers 40
and 41 of stage 20.
Sensor assembly 19 and comparator 20 are powered from the regulated
supply 50 to provide reliable logic response. The regulator 50 may
be any suitable construction, such as a Zener diode unit with a
temperature compensating diode and stabilizing capacitors to
produce the desired regulated voltage. The regulator 50 produces
the desired operating voltage such as 9.2 volts.
The amplifier output lines 55 and 56 are similarly coupled to high
gain amplifying and switching stages 23 and 23a which function as
power switches and are shown as Darlington switching circuits. As
each of the output lines is similarly connected, that for the
raising or up line 55 is described, with the corresponding elements
for the lowering circuit being identified by similar prime
numbers.
The illustrated amplifier 23 includes a pair of transistors 61 and
62 which are connected as a Darlington pair, with the input base
connected by a coupling resistor 63 to the comparator output line
53. A turn-on resistor 64 is connected between the base and the
ground and emitter to complete the input signal circuit. The
resistors 63 and 64 form a voltage divider which reduces the base
voltage at the amplifier 23 below the switching level with the
operational amplifier 40 off, and applying the relatively low
voltage signal.
The output is taken at the collector with a negative feedback
network including capacitor 65 which introduces a time constant in
the system with a delayed turn-on and rapid turn off to prohibit
the system from correcting itself from each slight variation in
position of the stern drive unit, such for example as associated
with slight wave bounce. The switching and associated feedback
circuit is more fully described in the copending application of
James Hager and no further description is given herein.
The output switching as provided by the Darlington circuitry
provides selective completion of the circuit to the relay 24, which
has a winding 67 connected in series with the output circuit of the
Darlington transistor unit to the battery power supply. The
Darlington pair normally presents a high impedance or open circuit
condition to the relay winding. When the Darlington pair is turned
on, as a result of the turn-on signal at the output line 55 of the
amplifier 40, the Darlington connected transistors rapidly switch
to full on to establish a very low impedance path thereby
completing the energizing circuit through the relay winding. This,
in turn, closes the related relay contacts 67-1 to provide power to
the motor for energizing of the electric motor in a lift direction
and thereby driving the pump 14 to power the hydraulic system to
correspondingly raise the drive unit 1. As the drive unit 1 raises,
the magnet 34 is correspondingly positioned and varies the
effective flux supplied to the Hall cell 27 and correspondingly
changes the voltage signal to the comparator 20 when the sensed
signal corresponds in a predetermined manner to the set signal as
determined by the positioning of unit 1.
If for any reason the drive unit 1 moves from the set position, the
Hall cell 27 generates an offset signal to operate the relay 24 or
25. If the stern drive unit 1 is above the desired position, a
signal appears at output line 56 which turns on the Darlington
transistors 61' and 62' and completes the power circuit to the
lower relay winding 68. This, in turn, results in the closing of
the associated contacts 68-1 to energize the electric motor 15 to
operate in the opposite direction with the hydraulic pump 14
oppositely actuated to introduce hydraulic fluid into the
piston-cylinder means 13 to lower the stern drive unit 1.
When the unit is again in the preset position, the magnet 34 is
relocated with respect to the Hall cell 27 to establish a null
condition to turn off the trim drive and establish the stable
condition.
The operator may therefore conveniently control the trim position
before and during running.
The Hall cell sensor 19 of FIGS. 5 and 6 is preferably constructed
as a small compact and potted assembly which is mounted to the
stern drive unit 1, as most clearly shown in FIGS. 3 and 4. A
cup-shaped disc housing 70 includes a plurality of outer arcuate
mounting slots 71 and 72 and is secured abutting the gimbal ring or
member 6 by suitable cap screws 73 and 74 passing through the slots
71 and 72 and threaded into appropriately tapped openings 75 in the
member 6. The housing 70 includes a central opening aligned with
the horizontal shaft 76 which is rotatably journaled in the gimbal
ring and defining the tilt axis support of the drive unit 4. The
housing 70 includes a cylindrical recess or chamber 77 in the
exterior face with a peripheral inner wall 78 of stainless steel or
other similar non-magnetic material. The Hall cell 27 and
associated circuitry of unit 19 shown for example in FIG. 6 is
located within the recess 77 which is then filled with a suitable
potting material 79 such as an epoxy resin to physically support
the elements and protect them from the severe environmental
conditions encountered in marine use. The Hall cell 27 is
diametrically located with respect to the shaft opening 75, as
shown in FIG. 4. The annular or doughnut shaped magnet 34 is
secured to the shaft 76 by a clamping nut 80 and located within the
central opening of wall 78 of the housing 70, particularly in a
common plane with the Hall cell 27. The magnet is diametrically
polarized to establish a radially outwardly directed flux which is
impressed upon the Hall cell 27. Thus, the nonmagnetic inner wall
readily transmits the flux to the potted Hall cell. As described in
connection with FIG. 6, a sine wave of flux is applied to the Hall
cell in accordance with angular orientation of the drive unit with
respect to the gimbal ring or member 6. A cover 81 may be secured
to the housing to enclose the potted recess and the magnet.
If desired, the system can be employed with a resistance sensing
element, similar to that described in U.S. Pat. No. 3,641,965 in
place of the Hall cell 27. FIG. 7 is a schematic circuit
corresponding to that of FIG. 6 with the substitution of a resistor
position sensor 81 for the Hall cell unit 19 described above and
additionally with a fail-safe circuit 82. Corresponding elements of
FIGS. 6 and 7 are correspondingly numbered and no further
description of the circuit is given other than to clearly describe
the revision to the basic circuit. The resistor position sensor 81
includes a resistor card 83 with a movable wiper 84 rotatably
mounted to scan the card. A wound resistor 85 is mounted on the
card and connected between the ground and the input terminal of the
operational amplifier 40 functioning as the comparator. The wiper
84 in turn is connected to the corresponding input and thus
selectively shorts a portion of the resistance from the circuit and
simultaneously adjusts the voltage impressed on the input terminal.
The wiper is coupled to rotate with drive unit 4, for example, by
connection to shaft 76 as disclosed in U.S. Pat. No. 3,641,965. A
fixed resistor 86 is connected between the input terminal of the
comparator forming the common connection to the position sensor and
the regulated power supply. The fixed resistor 86 and the variable
resistor 85 constitutes a variable voltage dividing network with
the variation of the lower leg being directly related to the
angular displacement. With the series resistances connected to the
regulated voltage supply, a non-linear output with angular
displacements is generated at the common junction. Applicant has
found that the voltage output varies approximately as a sine wave
with angular displacement, at least over the limited number of
degrees encountered for marine propulsion units such as stern
drives wherein the movement covers essentially 55.degree. of
displacement. The voltage dividing network as described defines a
curve which very closely approaches the sine wave curve and thus is
completely suitable for direct substitution for the Hall cell
circuit shown in FIG. 3. Further, the variable resistor 85 is
adjusted to create an offset signal corresponding to a zero degree
positioning of the drive unit 1 to stimulate the offset adjustment
of the Hall cell, with the sine wave generated from that zero
reference position.
When a resistive sensor is employed, an open circuit condition may
be caused by the wear of the unit, water contamination, corrosion
and the like. If the sensing circuit does open, the voltage applied
to the input of the comparator from the regulated voltage supply
rises as a result of the very high impedance presented by a total
or partial maximum open circuit between the input terminal and
ground. This would, of course, create a maximum turn on lower
signal at the sensing output line connected by resistors 47 and 47a
to the comparator 20 which in turn would lower the drive unit 1 to
its lowermost position, with no means at the control of the
operator for reversing or running the drive unit 1 to a lower
position. Such a malfunction may create a particularly dangerous
position under operating movement of the watercraft. To prevent
this type of condition from arising, a safety circuit 82 is
interconnected into the control system and in particular responds
to an abnormal input voltage to positively prevent the lower system
from being turned on.
The fail-safe circuit 82 in the illustrated embodiment of the
invention is connected to the circuit of lowering amplifier 41 and
particularly line 87 to the base of transistor 61' and to the
sensor signal line 32a to the comparator resistors to hold line 87
at ground in response to an abnormally high input voltage at the
sensor power terminal or line and thereby prevent turning on of the
lower switch 23a and the associated relay 68.
More particularly, the fail-safe circuit 82 includes a single high
beta transistor 88 connected between the line 87 and thus the base
of transistor 61' and ground. A Zener diode 89 in series with
resistor 90 connects the base of transistor 88 to the sensor line
91.
A small capacitor 92 is connected between the resistor and ground
which defines an inegrating circuit holding the fail-safe circuit
in the off condition for a momentary initial period of time with
the input voltage above the 8.8 volts reference level. This is
desirable to prevent actuation of the fail-safe circuit 82 during
momentary or transient periods of abnormal voltages. Thus, in the
usual wound resistor unit, the wiper 84 loses contact in moving
from one winding turn to the next and would do so in the preferred
linear resistor unit described. Zener diode 89 would be selected to
provide a threshold detection of the voltage when it rises above a
selected level greater than the voltage necessary to null the
maximum voltage from the reference or selection unit 17. When diode
89 conducts, current is supplied to the transistor 88 which shorts
the input to the lower circuit to ground. Thus, with a 9.2 volt
regulated supply and a maximum input reference signal of 7 volts,
the Zener diode 89 may be conveniently selected to respond to a
signal of 8.8 volts.
The fail-safe circuit may take any voltage sensitive form which
will detect an abnormal high voltage on the input of the sensor
circuit or the like and positively prevent the malfunctioning of
the circuit to lower the stern drive unit 1, particularly under
running conditions. For example, a differential amplifying circuit
may compare a fixed voltage with that at the sensor line and
control a control switch in the lower drive circuit.
The circuit of FIG. 7 otherwise functions in the same manner as
that previously described to provide an automatic raising and
lowering of the drive unit to various trim positions as a result of
the simple input selection by the operator.
Further, the relatively large number of selections which can be
made permit the positioning of the drive unit in a proper position
under essentially all possible operating conditions.
In addition to the electronic signal processing, the trim control
can employ a relatively simple comparison network for actuating of
the trim positioning motor or the like. For example, FIG. 8
illustrates a simple differential relay system.
In FIG. 8, a control rheostat 96 and a trim indicator rheostat 97
have one end connected in common to the battery 98 and related
movable taps connected to selectively energize a differential relay
99. The control rheostat 96 is mounted for manual adjustment. The
trim indicator rheostat 97 is coupled to the drive unit for example
as shown in previously referred to U.S. Pat. No. 3,641,965. The
rheostat taps provide corresponding power signals in accordance
with a desired trim angle and the actual trim angle.
The differential relay 99 includes a first winding 100 connected in
series with the rheostat 96 and energized accordingly. The winding
100 is electromagnetically coupled to one end of an armature 101
which is centrally pivoted at 102. The armature 101 is, generally,
a T-shaped member which is connected by a line to battery 98 and
with the stem portion carrying suitable contacts including a first
set of contacts 103 which are closed upon predetermined pivoting of
the armature 101 toward the electromagnetic unit defined by winding
100. An opposed winding 104 is similarly connected into circuit
with the rheostat 97 and is coupled to the opposite end of the
armature 101. The electromagnetic force of the winding 104 tends to
pivot the armature 101 in an opposite or counter-clockwise
direction as viewed in FIG. 8. Selected pivotal movement in this
direction results in closing of an oppositely disposed set of
contacts 106. Thus, if the currents through the windings 100 and
104 are balanced or essentially balanced, the armature 101 is held
in a central position with contacts 103 and 106 both open.
Differential energization of windings 100 and 104 results in the
closing of contacts 103 or 106 to provide corresponding
energization of a pair of power relays 107 and 108. The power relay
107 is connected to the one side of the contacts 103 and ground
such that when the contacts 103 close, power is supplied to the
power relay winding 107 to close a related set of contacts 107-1.
Similarly, power relay 108 is connected in circuit through the
contacts 106 to control a related set of contacts 108-1. The
contacts 107-1 and 108-1 are connected respectively in series with
the corresponding forward and reverse windings of a reversible
motor 109, for corresponding controlled energization thereof. The
motor 109 is coupled to drive a pump 110 which in turn provides
circulating fluid through an up-trim line 111 or a down-trim line
112 in accordance with the directional energization of the motor
109. The down-trim line includes a surge valve 113. In accordance
with a further novel aspect of the present invention, a
differential pressure switch 114 is provided in the energizing
circuit of the motor 109 to momentarily remove the automatic trim
control under log jumping conditions. The differential pressure
switch 114 includes a pressure sensor 115 which is connected in
parallel with the surge valve 113. The pressure sensor 115 is
coupled to control a normally closed switch 116 which is connected
between ground 117 and the ground side of the motor 109. If a back
pressure is created on the drive unit resulting in a greater
pressure on the down side line of the actuator in excess of the
pump pressure at line 112 and thus a net back pressure, the switch
116 opens. This effectively opens the circuit for the control and
permits the lower drive unit to move upwardly in a relatively
unrestricted manner to clear an obstruction.
The operation of the embodiment shown in FIG. 8 is otherwise
generally similar to that previously described. Thus, the current
flow of the two windings of the differential relay 99 is in
accordance with the resistance in the respective branches which in
turn is proportional to the desired setting and the actual trim
setting, with the current in the one coil or winding greater than
in the other in an amount equal to the relay threshold leve, the
corresponding contacts 103 or 106 close to provide corresponding
energization of the appropriate power relay 107 or 108. This, of
course, establishes the desired operation of the trim pump 110 to
readjust the trim angle until such time as the trim angle sensing
rheostat 97 again equals the preset rheostat 96. This then
re-establishes the null condition with the trim unit at the desired
position.
As in the previous systems, any disturbance or oil leakage may
result in a corresponding change in the trim angle from the dial
setting. This again operates the trim angle control to
automatically reset the system.
Further, various safety features can, of course, be incorporated
into the trim setting control of this invention. For example, an
interlock relay may be interconnected to open when the ignition
switch is turned off with a required manual reset switch. The
interlock relay would remove the system until such time as the
manual reset seitch is positively actuated. A simple on-off switch
could, of course, be provided with reliance on the operator to turn
off the switch whenever the ignition system is turned off. For
emergency use, a direct override control could be provided at the
trim pump to permit desired positioning if the automatic system
malfunctions or the like.
In addition to the illustrated sensing devices, any other suitable
sensors can be employed. For example, inductive and capacitive
sensors can be readily applied within the broadest concept of the
present invention as well as various photo devices such as
photoresistive and photoemissive devices. Further, although the
control setting dial is shown on the instrument panel of the boat,
it may also be incorporated in the throttle control, the steering
wheel hub or the steering column for convenient manipulation by the
operator. It may also be desirable to have the control setting dial
constructed to provide automatic indication of the setting position
through the sense of touch by the operator such that he can
maintain complete visual attention to the driving of the boat.
Various other designs can, of course, be incorporated in connection
with each of the particular portions of the circuit and the like
although that illustrated has been found to provide satisfactory
operation. It may be desirable to employ a suitable stop means to
prevent selection of the two uppermost positions while under power
and thereby eliminate the possible danger of moving the drive unit
(when running) upwardly out of the water. Other mechanical or
electrical interlocks, not shown, can also be readily designed into
the system to prevent such selection.
These and similar features can, of course, be readily provided for
those skilled in the art and thus no further particular discussion
or illustration thereof is given.
The present invention has been found to provide a relatively simple
and reliable trim power control system and apparatus.
Various modes of carrying out the invention are contemplated as
being within the scope of the following claims, particularly
pointing out and distinctly claiming the subject matter which is
regarded as the invention.
I claim:
* * * * *