United States Patent
`
`1191
`
`[11]
`
`4,398,252
`
`
`
`
`
` Frait [45] Aug. 9, 1983
`
`[54] ELECTRIC CONTROLLER HAVING
`OUTPUT POWER LIMITING CIRCUIT
`Inventor:
`John S. Frait, Ann Arbor, Mich.
`[75]
`[73] Assignee: Kelsey—Hayes Co., Romulus, Mich.
`[21] Appl. No.: 255,595
`.
`AP“ 20’ 1981
`F11ed:
`[22]
`‘Int. Cl.3 .............................................. B60T 13/68
`[51]
`[52] US. Cl. ................................... 364/426; 188/3 R;
`303/20
`[58] Field of Search ...................... 364/426; 303/7, 20;
`188/3 R; 340/650, 653, 664
`References Cited
`US. PATENT DOCUMENTS
`
`[56]
`
`3/1970 Vandenbroek ................... 303/20 X
`3,503,652
`9/1975 Pittet, Jr. et a1.
`.
`303/20 X
`3,909,075
`3,967,863
`7/1976 Tomecek et al.
`.
`303/2ox
`4,084,859 4/1978 Bull et a1.
`..........
`........ 303/20
`‘ 4,254,998
`3/1981 Marshall et a1.
`..
`4,295,687 10/1981 Becker et a1.
`......................... 303/20
`
`303/20 X
`
`Primary Examiner—Jerry Smith
`Attorney, Agent, or Firm—Ralph J. Skinkiss; Oliver E.
`Todd; Mark 1’ Sobansk1
`[57]
`ABSTRACT
`An electronic control for electrically operated brakes
`utilizing solid state electronic components to control
`the braking mechanism in a towed vehicle. A trans-
`ducer develops a control signal corresponding to the
`braking effort desired, and may be actuated by the hy-
`draulic brake system of the towing vehicle or, alter-
`nately, may be actuated from the brake foot pedal itself
`or from a manual control. Power is applied to the brakes
`as a pulsating voltage, the pulse width of which is var-
`ied in response to the control signal. The pulse width is
`decreased with increasing currents to limit the power in
`the circuit when a short occurs in the towed vehicle
`brake circuit. The electronic control also may be used in
`other applications.
`
`8 Claims, 4 Drawing Figures
`
`+v
`
`SAWTOOTH
`
`OSCILLATOR
`
`37
`
`43
`
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` CURRENT
`
`LIMITER
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`Iéa
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`>
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`LEVEL SHIFTER
`A N D
`GAIN CONTROL
`
`‘
`—
`COMPARATOR
`+
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`
`34
`
`35
`
`36
`
`35 42
`
`Curt - Exhibit 1011 - 1
`
`Curt - Exhibit 1011 - 1
`
`

`

`US. Patent
`
`Aug. 9,1983
`
`Sheet 1 of2
`
`4,398,252
`
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`' ———‘—FIG 3
`
`Curt - Exhibit 1011 - 2
`
`Curt - Exhibit 1011 - 2
`
`

`

`
`
`U.S. Patent
`
`Aug. 9, 1983
`
`Sheet 2 of2
`
`4,398,252
`
`
`
`Curt - Exhibit 1011 - 3
`
`Curt - Exhibit 1011 - 3
`
`

`

`4,398,252
`
`BACKGROUND OF THE INVENTION
`
`5
`
`SUMMARY OF THE INVENTION
`
`55
`
`ELEcixIC CONTROLLER HAVING OUTPUT
`POWER LIMITING CIRCUIT
`
`2
`tion against short circuits in the circuit interconnecting
`the electronic brake signal generator with the electric
`brakes in the towed vehicle. The brakes in the towed
`vehicle are actuated by a pulse signal. In the event of a
`partial or resistive short circuit, the pulse width is de-
`creased to limit the output power from the electronic
`This invention relates to electric controllers and more
`controller. In other words, each pulse applied by the
`particularly to an electric controller for supplying
`electronic controller to the brake circuit is cut short in
`power to, for example, electric brake systems to be used
`response to an over current condition to limit the output
`by a towed vehicle when being pulled by a towing
`1 0
`
`power from the brake controller to a nondestructive
`vehicle.
`level. As the current demand increases, each pulse is cut
`Recreational and utility trailers adapted to be towed
`short at an earlier point. The output current load at
`by automobiles and small trucks and many similar
`which the output power is limited is selectable and can
`towed vehicles are commonly provided with electric
`be varied in response to temperature and to the power
`brakes. The electric brakes generally comprise a pair of
`1
`5
`brake shoes which, when actuated, frictionally engage a
`source voltage. In the event that a short circuit is mo-
`brake drum. An electromagnet is mounted on an end of
`mentary, full power will be reestablished immediately
`a lever which actuates the brake shoes. When an elec-
`to the towed vehicle brakes upon removal of the short
`tric current is applied to the magnet, the magnet is
`circuit.
`drawn against the rotating brake drum which pivots the
`Accordingly, it is an object of the invention to pro-
`20
`lever for actuating the brakes. The braking force is
`vide an improved electronic control suitable for use in a
`proportional to the electric current applied to the mag-
`brake system for towed vehicles.
`net. Controls for electrically operated brakes must be
`Another object of the invention is to provide an im-
`easily adjustable to accommodate different relative
`proved electronic controller having circuit protection
`weights of the towed and towing vehicles. The controls
`against partial or complete short circuits in the output
`25
`further must be predictable to give the driver of the
`circuit.
`towing vehicle a feeling of smooth control and positive
`Other objects and advantages of the invention will
`brake operation both upon applying the braking effort
`become apparent from the following detailed descrip-
`to the towing vehicle and also upon releasing the brak-
`tion, with reference being made to the accompanying
`ing effort.
`drawings.
`3 0
`The braking system for the towed vehicle typically is
`actuated either in response to hydraulic pressure in the
`braking system of the towing vehicle or in response to
`FIG. 1 is a diagrammatic illustration of an electronic
`the pressure applied by a driver's foot on a transducer
`brake system for a towed vehicle incorporating the
`mounted on the towing vehicle's brake pedal or in re-
`control of the invention;
`sponse to a manually operated control. In one type of 35
`FIG. 2 is a schematic block diagram of the electronic
`electronic control for electrically operated brakes, a
`controller of the present invention connected for operー
`pulse modulator generates a pulsating voltage having a
`ating electric brakes in a towed vehicle;
`pulse width which is varied with the amount of braking
`FIG. 3 is a graph depicting exemplary input voltages
`effort desired for the towed vehicle. The electronic
`to the comparator and the resulting output pulses from
`control is protected against short circuit conditions in 40
`the comparator in the block diagram of FIG. 2; and
`the circuit for the brake actuating magnets. In the event
`FIG. 4 is a detailed schematic circuit diagram of an
`of a sudden short circuit, the pulse output from the
`electronic controller constructed in accordance with
`pulse modulator is disabled to protect the circuit. The
`the present invention.
`pulse output may be disabled for several pulses and then
`reestablished to determine if the short circuit condition 45
`was momentary or if it still exists. Circuitry of this type
`for protecting against short circuits in the output of an
`Turning now to the drawings and particularly to
`electronic brake control works quite well for protecting
`FIG. 1, a brake system 10 is illustrated for a combined
`the control in the event of sudden and complete short
`towing vehicle and towed vehicle such as an automo-
`circuits. However the circuit is not designed to handle 50
`bile or pickup truck towing a recreational or utility
`partial short circuits which act as a resistance and
`trailer. A conventional brake system for the towing
`causes a higher than normal output current from the
`vehicle is illustrated within the dashed line 11 and in-
`brake control which is below the level which causes an
`eludes a driver operated brake pedal 12, a master cylin-
`interruption in output from the control.
`der 13 and hydraulic lines 14 for supplying brake fluid
`to conventional drum or disc brakes located at each of
`the vehicle wheels 15. When a vehicle driver applies
`According to the present invention, an improved
`pressure to the brake pedal 12, a piston is moved in the
`solid state electronic control system is provided for
`master cylinder 13 to increase the pressure of the brake
`supplying controlled power to, for example, the braking
`6o fluid applied through the lines 14 to the brakes at each
`mechanism in a towed vehicle. The brakes are actuated
`of the individual wheels 15. The pressure of the fluid
`in response to a signal corresponding to the braking
`within the brake lines 14 is proportional to the braking
`effort desired. This signal is generated by a conven-
`釦rce.
`tional transducer, such as a pressure sensing transducer
`In the illustrated brake system 10, a pressure trans-
`located in the hydraulic brake system of the towing
`65 ducer 16 is connected to the brake lines 14 for generat-
`vehicle or a transducer which measures the pressure
`ing an electric signal proportional to the pressure of the
`applied by a driver to the brake pedal for the towing
`brake fluid within the lines 14. This signal is applied to
`vehicle or in response to a manually generated signal.
`an electronic controller 17 which in turn generates and
`The control system is provided with improved protec-
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Curt - Exhibit 1011 - 4
`
`

`

`4,398,252
`
`4
`3
`control 34. Whenever the magnitude of the voltage on
`applies an electric signal over a wire 18 to electric
`the output 35 is higher than the voltage on the output
`brakes 19 and 20 for the wheels of the towed vehicle.
`from the sawtooth wave oscillator 37, the comparator
`The electric brakes 19 and 20 each include a pair of
`36 will generate an output voltage which is applied to a
`brake shoes 21 and 22 which, when actuated by a lever
`driver 38. The driver 38 establishes an output in re・
`23, are expanded into contact with a brake drum 24 for 5
`sponse to an output from the comparator 36 for control-
`braking the wheels of the towed vehicle. A separate
`ling a switching transistor 39. The transistor 39 has
`electromagnet 25 is mounted on an end of each of the
`collector-emitter electrodes which are connected in
`brake actuating levers 23. Each electromagnet 25 is
`series between a power source such as the battery for
`positioned to abut the generally flat side of a brake drum
`the towing vehicle, a current sensing resistor 40 and a
`24. As an electric current is passed through each of the 10
`junction 41. The junction 41 is connected through the
`electromagnets 25, the electromagnets are drawn into
`parallel windings of the electromagnets 25 for the
`contact with the brake drums 24 and the resulting drag
`brakes 19 and 20 to ground and also is connected
`pivots the levers 23 to engage the brakes 19 and 20 in a
`through a series current limiting resistor 42 and the light
`conventional manner.
`5 28 to ground. The light 28 may be a light emitting diode
`During normal operation of the towing and towed 1
`(LED), as shown. When the transistor 39 is turned on,
`vehicles, the electronic controller 17 applies an output
`current will flow simultaneously through each of the
`signal to the wire 18 for actuating the towed vehicle
`electromagnets 25 and the series resistor 42 and the light
`brakes 19 and 20 in response to output from the trans-
`28.
`ducer 16. The transducer 16 has been described as being
`0 Problems sometimes occur with short circuits in the
`a pressure transducer responsive to the hydraulic pres- 2
`brake circuit in a towed vehicle. The short circuit may
`sure within the brake lines 14. However, it should be
`be caused, for example, by screws coming out of con-
`noted that other types of transducers may be used for
`nectors and moving around as the towed vehicle is
`generating signals proportional to the braking force.
`jolted by rough roads. Abrasion of wire insulation also
`For example, a transducer may be mounted on the
`5 can cause short circuits. Most short circuits in an elec-
`brake pedal 12 for generating a signal which is propor- 2
`tric brake system for a towed vehicle are intermittent in
`tional to the force applied by the driver's foot to the
`nature. Furthermore, many shorts are only partial
`brake pedal 12. Such a signal would be applied to the
`shorts in that the short acts as a low value resistance.
`electronic controller 17 in place of the signal from the
`When a short circuit does occur, there will be an in-
`transducer 16. In addition, it is sometimes desirable to
`0 creased current flow through the current sensing resis-
`manually actuate the brakes 19 and 20 in the towed 3
`tor 40 and the switching transistor 39. If the short cir-
`vehicle. This may be desirable, for example, to stabilize
`cuit is a complete short or if a partial short circuit is
`the towed vehicle against vacillations or swinging
`maintained for very long, excessive currents may de-
`caused by strong side winds. Therefore, a manual slide
`stroy the switching transistor 39. Therefore, the elec-
`switch 26 is provided on the electronic controller 17 to
`5 tronic controller 17 is provided with a protection circuit
`allow the vehicle driver to manually apply the towed 3
`for limiting the output in the event of a partial or corn-
`vehicle brakes 19 and 20 without applying the towing
`plete short circuit. It will be apparent that as the current
`vehicle brakes. The electronic controller 17 also is pro-
`through the current sensing resistor 40 and the switch-
`vided with a manual gain control 27. The gain control
`ing transistor 39 increases, the voltage appearing across
`27 allows the vehicle driver to compensate for different
`0 the current sensing resistor 40 similarly will increase.
`loads in the towed vehicle. For example, as the load in 4
`This voltage is applied to a current limiter 43 which in
`the towed vehicle increases, it is necessary to increase
`turn applies a signal to the level shifter and gain control
`the braking force in the towed vehicle relative to the
`34 to decrease the voltage applied on the output 35 to
`braking force applied in the towing vehicle. By adjust-
`the comparator 36 when excessive currents are encoun-
`ing the gain control 27, the power applied by the elec-
`5 tered.
`tronic controller 17 to the electromagnets 25 may be 4
`Referring now to FIGS. 2 and 3, the operation of the
`increased or decreased for any given output from the
`electronic controller 17 is illustrated in greater detail.
`towing vehicle brake pressure sensing transducer 16.
`The sawtooth oscillator 37 generates an output wave-
`The electronic brake controller 17 also is provided with
`form 44. The waveform 44 will have a constant fre-
`an indicator light 28. The light 28 is energized with an
`0 quency which may be, for example, on the order of 400
`intensity proportional to the signal applied to the wire 5
`Hz. to 600 Hz., although frequencies outside this range
`18 to actuate the towed vehicle brakes 19 and 20. The
`also may be used. The towing vehicle brake pressure
`light 28 provides a visual indication to the driver to
`transducer 16 generates an output voltage which is
`show that the controller 17 and the towed vehicle
`proportional to the force applied by the driver to the
`brakes are operating properly.
`5 brake pedal 12. The output voltage from the transducer
`Turning now to FIG. 2, a block diagram is shown for 5
`16 is illustrated as a first constant voltage level 45a at
`the circuit of the electronic controller 17. Both the
`the left portion of FIG. 3 and at a higher level 45b at the
`brake pressure sensing transducer 16 and the manual
`right of the graph of FIG. 3. This would represent the
`slide switch 26 are depicted as potentiometers 16a and
`condition where the driver applies a light brake force
`26a, respectively, which apply a variable voltage
`0 initially, and, subsequently, a heavier braking force to
`through a diode 32 or 33, respectively, to a level shifter 6
`the pedal 12. When the transducer 16 generates the
`and gain control 34. The level shifter and gain control
`lower level output voltage 45a, the voltage 45a will be
`34 applies an output voltage on a line 35 to one input of
`above the output waveform 44 from the oscillator 37
`a comparator 36. This voltage is proportional in magni-
`only for short periods in each cycle. During these short
`tude to a desired braking force, as established by either
`5 periods, the comparator 36 generates relatively narrow
`the transducer 16 or the manually operated switch 26. A 6
`pulses 46a which are applied to the driver 38. As the
`sawtooth wave oscillator 37 applies a signal to a second
`level of the voltage on the output 35 from the level
`input of the comparator 36 which is compared with the
`shifter and gain control 34 increases to the level 45b, it
`signal on the output 35 from the level shifter and gain
`
`Curt - Exhibit 1011 - 5
`
`

`

`4,398,252
`
`5
`6
`will be seen that the comparator 36 will have an output
`ground. The signal on the emitter of the transistor 61
`in the form of pulses 46b which have a greater width
`forms the output 35 from the level shifter and gain
`than the pulses 46a. Since the pulses are wider and there
`control 34 shown in the block diagram of FIG. 2. In
`is no change in frequency, there is a greater duty cycle.
`operation, the transistors 58 and 61 are operated as
`emitter followers. The transistor 61 compensates the
`Under a maximum braking condition, the width of the 5
`output of the transistor 58 for changes in voltage and
`pulses 46b may increase until the comparator 36 applies
`a constant voltage to the driver 38 to fully actuate the
`temperature. The voltage applied to the output 35 may
`towed vehicle brakes 19 and 20. In the event that a
`be identical to the voltage appearing on the base of the
`partial short circuit occurs while the transducer 16 and
`transistor 58. The capacitor 64 is charged to a voltage to
`the level shifter and gain 34 generates the output volt- 10
`establish the duty cycle of the electronic controller 17,
`age 45b, the excessive current will cause the output
`as demanded by the setting of either the vehicle brakes
`or the manual switch 26 on the electronic controller 17.
`pulses 46b to be terminated short, such as along the
`The functions of the comparator 36 and the sawtooth
`exemplary dashed line 47. By terminating the pulses 46b
`early, the duty cycle for the transistor 39 is shortened to
`wave oscillator 37 are performed by a single integrated
`limit the power dissipated by the transistor 39 and, 15
`circuit 68 which may, for example, be a type LM 556
`therefore, to protect the transistor 39 from destruction.
`integrated circuit. The integrated circuit includes four
`In the event of a total short circuit connecting the junc-
`comparators 69-72 and two flip flops 73 and 74. The
`function of the comparator 36 is performed by the corn-
`tion 41 to ground, the width of output pulses from the
`comparator 36 will be shortened so as to terminate
`parator 69 within the integrated circuit 68. The compar-
`ator 69 has an output passed through the flip flop 73 to
`almost simultaneously with the beginning of each pulse. 20
`Therefore, the transistor 39 will be switched on and off
`a terminal 75. The comparator 70 within the integrated
`circuit 68 is not used. High impedance inputs to the
`almost simultaneously.
`Turning now to FIG. 4, a detailed schematic circuit
`comparator 69 are connected to the output 35 from the
`diagram is shown for electronic controller 17. The tow-
`level shifter and gain control 34, as taken from the emit-
`ing vehicle has a battery 50 which is connected between 25
`ter of the transistor 61, and a high impedance output 76
`from the sawtooth wave oscillator 37. The outputs of
`ground and a bus 51. The bus 51 is connected through a
`switch 52 and a second, parallel switch 26b and a series
`the two comparators 71 and 72 forming the oscillator 37
`resistor 53 to a bus 54. The switch 52 may comprise the
`are connected to the two inputs to the flip flops 74. The
`switch which controls the brake lights in the towing
`flip flop 74 has an output applied through a resistor 77
`vehicle or may be a separate switch mounted so as to be 30
`to the oscillator output 76. The oscillator output 76 also
`activated whenever a driver applies pressure to the
`is connected through a capacitor 78 to ground and is
`vehicle brake pedal 12. The switch 26b is incorporated
`connected to one input for each of the comparators 71
`along with the potentiometer 26a into the manual slide
`and 72. The other inputs to the comparators 71 and 72
`switch 26 so as to be closed whenever the slide switch
`are connected together and through a filter capacitor 79
`26 is actuated. Consequently, whenever the vehicle 35
`to ground. The oscillator 37 will generate a waveform
`on the output 76 having a sawtooth format of the type
`brakes are applied or the slide switch 26 is manually
`illustrated by the waveform 44 in FIG. 3. The fre-
`actuated, a voltage is applied from the battery 50 to the
`quency of this waveform is determined by the values of
`bus 54. The voltage on the bus 54 is regulated by a
`the capacitor 78 and the resistor 77. The oscillator out-
`parallel zener diode 49 and capacitor 48. The bus 54 is
`put 76 is applied to the comparator 69 along with the
`connected through the transducer potentiometer 16a to 40
`output 35 from the level shifter and gain control 34. The
`ground and also through the slide switch potentiometer
`comparator 69 in turn generates a pulsed output which
`26a to ground. The potentiometer 16a has a variable
`appears on the terminal 75 of the integrated circuit 68.
`voltage tap connected through the diode 32 to a june-
`The pulsed output from the comparator 36, as taken
`tion 55 and the potentiometer 26a has a variable voltage
`
`tap connected through the diode 33 to the junction 55. 45 from the terminal 75, is applied through a resistor 80 to
`the base of a pre-driver transistor 81. The emitter of the
`Therefore, a portion of the voltage on the bus 54 will be
`transistor 81 is grounded and the collector of the transis-
`applied to the junction 55, depending upon the output of
`tor 81 is connected through a zener diode 82 to ground.
`the transducer 16 and/or the output of the manual slide
`The collector of the transistor 81 also is connected
`switch 26. The junction 55 is connected through a po-
`through a resistor 83 to the base of a driver transistor 84.
`tentiometer 27a and a fixed resistor 56 to ground. The 50
`The base of the transistor 84 also is connected through
`potentiometer 27a forms the gain control 27 (shown in
`a resistor 85 to the bus 51 and through a capacitor 86 to
`FIG. 1) and has a tap connected through a potentiome-
`the output junction 41. The emitter of the transistor 84
`ter 57 back to the bus 54. The potentiometer 57 is a trim
`is connected directly to the bus 51 and the collector is
`control and has a variable output tap connected to the
`55
`base of a transistor 58.
`connected to the base of the main output transistor 39
`and also through a resistor 87 to the junction 41. The
`The trim control potentiometer 57 is adjusted during
`collector of the transistor 39 is connected through the
`calibration of electronic controller 17 so that the mini-
`mum voltage applied to the base of the transistor 58 is a
`current sensing resistor 40 to the bus 51 and the emitter
`of the transistor 39 is connected to the output junction
`predetermined percentage of the voltage on the bus 54,
`41.
`such as one-third of the voltage on the bus 54. The 60
`During operation of the electronic controller 17, the
`transistor 58 has a grounded collector and an emitter
`connected through a resistor 59 to the bus 54. The emit-
`comparator 36 will generate output pulses, appearing at
`the terminal 75 on the integrated circuit 68, having a
`ter of the transistor 58 also is connected to a junction 60
`which in turn is connected to the base of a second tran-
`fixed frequency determined by the frequency of the
`sistor 61. The transistor 61 has a collector connected to 65
`oscillator 37 and having a pulse width depending upon
`the output from the transducer 16 and/or the manual
`the bus 54 and an emitter connected through a parallel
`resistor 62 and a capacitor 63 to ground. The base of the
`slide switch 26. During each pulse appearing on the
`terminal 75, the pre-driver transistor 81 and the driver
`transistor 61 also is connected through a capacitor 64 to
`
`Curt - Exhibit 1011 - 6
`
`

`

`4,398,252
`
`7
`8
`transistor 84 will drive the transistor 39 to a fully on
`nected through the diode 102, the resistor 98 and the
`state. Consequently, current will flow from the bus 51
`transistor 96 to ground. Consequently, the capacitor 64
`through the current sensing resistor 40, the transistors
`will discharge to a lower voltage through the diode 102,
`39 and the junction 41 to the electromagnets 25 for
`the resistors 98 and the transistor 96 to decrease the
`actuating the brakes 19 and 20 on the towed vehicle. At 5
`duty cycle for the output of the electronic controller 17.
`the same time, the voltage appearing on the junction 41
`In the event of a total short circuit, the capacitor 64 will
`will cause a current to flow through the resistor 42 and
`be discharged to a predetermined minimum voltage. By
`the LED 28 the illuminate the LED 28. As voltage
`decreasing the voltage on the capacitor 64, the width of
`pulses are applied to the junction 41, the LED 28 will
`the pulses generated by a comparator 36 will decrease
`to in turn decrease the width of pulses applied to the
`have an intensity depending upon the duty cycle called 10
`for by the transducer 16 or the manual slide switch 26.
`output junction 41. This in turn limits the power han-
`This variable intensity of the LED 28 will confirm to
`dled by the output transistor 39 to prevent destruction
`of the transistor 39. Under a condition where there is a
`the vehicle driver that the brake system for the towed
`vehicle is operating properly. A diode 88 is connected
`direct short circuit connecting output junction 41 to
`from the junction 41 to the positive bus 51 and a diode 15
`ground, the transistor 92 will be turned off immediately
`89 is connected from the junction 41 to ground. Nor-
`after the main output transistor 39 is turned on. The
`mally, the two diodes 88 and 89 are reverse biased.
`capacitor 64' will discharge to the minimum voltage
`When the switching transistor 39 is turned off, the col-
`level to in turn terminate the pulse from the comparator
`lapsing magnetic field within the electromagnets 25 will
`36 which caused the output transistor 39 to be turned
`
`generate a negative spike voltage which appears on the 20 on. It should be noted that even when there is a partial
`junction 41. The diode 89 will effectively ground the
`or resistive short circuit, power limiting occurs only
`junction 41 for all negative voltages generated by the
`when the demanded duty cycle exceeds the decreased
`electromagnets 25 and the diode 88 protects against
`duty cycle. In other words, if a resistive short circuit is
`negative voltages in the power supply. The diode 88
`such that the duty cycle is limited at a 75% level, then
`may function to blow a fuse (not shown) in the event 25
`no output power limiting occurs when the vehicle
`that the battery polarity is reversed.
`driver applies the brakes to demand a lower duty cycle,
`When the transistor 39 is on and current flows to the
`such as a 50% duty cycle.
`electromagnets 25, this current also will flow through
`The transistor 96 and the resistor 97 may be elimi-
`the current sensing resistor 40, which has a low value. A
`nated and the resistors 95 and 98 connected directly to
`voltage will appear across the resistor 40 which is di- 30
`ground. However, a continuous current will then flow
`from the battery 50 through the resistors 94 and 95 to
`rectly proportional to the current flow therethrough. In
`ground. Although this current will be at a low level, it
`the event of a short circuit or a partial short circuit
`will present a continuous battery drain. The transistor
`between the junction 41 and ground, a voltage increase
`will appear across the resistor 40. This voltage increase
`96 eliminates this battery drain by acting as an open
`circuit whenever the electronic controller is turned off.
`is sensed by a transistor 92. The transistor 92 has an 35
`When either the brake actuated switch 52 or the switch
`emitter connected to the common junction between the
`26b of the manual slide switch 26 are closed to apply a
`resistor 40 and the collector of the transistor 39 and has
`voltage to the bus 54, the transistor 96 will be switched
`a collector connected through a diode 93 and a series
`on to connect the resistors 95 and 98 to ground. Thus,
`resistor 94 to the bus 51. The base of the transistor 92
`the transistor 96 protects the battery 50 from a constant
`also is connected through a resistor 95 and the collec- 40
`current drain when the electronic controller 17 is not in
`tor-emitter junctions of a transistor 96 to ground The
`operation.
`transistor 96 has a base connected through a resistor 97
`The electronic controller 17 has been described
`to the bus 54. In addition to the connection to the resis-
`above for use in an electric brake system 10 for operat-
`tor 95, the collector of the transistor 96 is connected
`ing electric brakes in a towed vehicle in synchronism
`through a resistor 98 to a junction 99. The junction 99 is 45
`with hydraulic brakes in a towing vehicle. However, it
`connected through a capacitor 100 to ground, through
`should be noted that the electronic controller 17 may be
`a resistor 101 to the collector of the current sensing
`used for other purposes where a variable pulse width
`transistor 92 and through a diode 102 to the junction 60
`D .C. signal is desired with circuit protection in the
`at the base of the transistor 61.
`event of an overload condition. For example, direct
`In operation, the transistor 96 will conduct whenever 50
`current motors sometimes are operated with pulse sig-
`voltage is applied to the bus 54. Consequently, the base
`nals having a duty cycle varied to control the speed of
`of the current sensing transistor 92 will have a voltage
`the motor. One such application for the electronic con-
`determined by the ratio of the two resistors 94 and 95.
`troller is a speed control for an electric trolling motor
`The forward biased diode 93 connected between the
`for fishing boats. Electric trolling motors are operated
`resistor 94 and the base of the transistor 92 serves for 55
`from storage batteries and speed control typically is
`temperature compensation of the operation of the tran-
`achieved through the use of a variable resistor posi-
`sistor 92. The characteristics of the diode 93 also lower
`tioned between the battery and the motor. Although the
`the trip point at which output regulation begins in re-
`use of a variable resistor is relatively inexpensive, it is
`sponse to an increase in temperature and in response to
`wasteful since at mid range speeds half the battery
`a decrease in the voltage on the bus 51. The resistors 94 60
`power is dissipated in the resistor. This reduces the
`and 95 are selected so that the transistor 92 will conduct
`range of the motor and/or the trolling time. With the
`whenever the current through the transistor 39 is within
`prior art speed controls, the electric trolling motor is
`acceptable limits. In the event that the current through
`susceptible to damage in the event that the propeller
`the transistor 39 progressively exceeds permissible lim-
`becomes fouled in weeds and creates high current con-
`its, the transistor 92 will progressively turn off. As the 65
`ditions in the stalled motor.
`transistor 92 shuts off and the diode 102 ceases to be
`The electronic controller 17 can be adapted for driv-
`back biased, the junction 60 at the base of the transistor
`ing such a motor merely by connecting the output june-
`61 in the level shifter and gain control 34 will be con-
`
`Curt - Exhibit 1011 - 7
`
`

`

`9
`10
`tion 41 to supply power to a trolling motor rather than
`signal exceeds the level of said sawtooth wave whereby
`to the electromagnets 25. The transducer 16 is replaced
`the duty cycle of such output is reduced.
`with a pedal controlled potentiometer which supplies
`4. An improved electronic controller for supplying
`an adjustable voltage signal to the level shifter and gain
`power from a D .C. source to electrically operated
`control. Or, the circui