”Waited States Patent
`
`[19;
`
`[11]
`
`4,295,687
`
`Becker et a1,
`
`
`
`{45] Oct, 29, 198i
`
`[S4] ‘ELECTRIC BRAKE SYSTEM
`
`[75]
`
`Inventors:
`
`James Becker, Ann Arbor; Daniel L.
`Neill, Belleville, both of Mich.
`
`[73] Assignee: Kelsey Hayes Company, Romulus,
`Mich.
`
`[21] Appl. No.: 15,572
`
`[22] Filed:
`
`Feb. 26, 1979
`
`[51]
`Int. Cl.3 .............................................. B60T 13/68
`
`[52] US. Cl. ................................ 303/20; 188/3 R
`[58] Field of Search ............... 303/20, 7, 92; 188/3 R,
`188/112 R; 307/265, 267, 356; 332/9 R
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,135,358 6/ 1964 Greentree ........................... 188/3 R
`1/ 1969 Beltramo ............... 303/20
`3,423,135
`
`1/1973 Goldberg ......
`3,714,470
`307/265 X
`.. 332/9 R X
`3,740,491
`6/1973 Cook et al.
`
`.. 188/3 R X
`3,838,888 10/1974 Gynn ............
`3,909,075 9/ 1975 Pittet, Jr. et al. ......... 303/20 X
`
`......... 303/92
`3,981,544 9/1976 Tomecek et al.
`4,033,630 7/1977 Hubbard ........................... 303/20 X
`
`Primary Examiner—J. D. Miller
`Assistant Examiner—Reinhard .l. Eisenzopf
`Attorney, Agent, or Firm—Ralph I. Skinkiss; Hugh L.
`Fisher; Oliver E. Todd, Ir.
`
`ABSTRACT
`[57]
`The control system for electrically operated brakes
`utilizes solid state electronic components to control the
`braking mechanism in a towed vehicle. Energy is pro-
`vided by a pulsating voltage, the pulse width of which
`is varied by a pulse width modulator in accordance with
`the amount of braking effort desired for the vehicle
`being towed. The pulse width modulator has the width
`of its output pulse directly controlled by either a hand
`control, or by a foot pedal control, or in response to the
`brake hydraulic pressure for the hydraulic brake system
`of the towing vehicle. Protection against short circuit
`conditions in the towed vehicle is provided which dis-
`ables the modulator from producing output pulses for a
`predetermined period of time. Adjustment of the ratio
`of braking effort in the towed vehicle to the braking
`effort in the towing vehicle is provided so as to compen-
`sate for different
`towed vehicle to towing vehicle
`weight ratios. A transducer develops a control signal
`corresponding to the braking effort desired, and may be
`actuated by the hydraulic brake system of the towing
`vehicle, or alternatively may be actuated from the foot
`pedal itself. The transducer is adapted to provide a
`substantially linear relationship between the towed ve—
`hicle brake force and the towing vehicle brake effort,
`either from brake system hydraulic pressure or from
`brake pedal force.
`
`7 Claims, 9 Drawing Figures
`
`MASTER
`CYLINDER
`
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`Curt - Exhibit 1010 - 1
`
`Curt - Exhibit 1010 - 1
`
`

`

`US. Patent
`
`Oct. 20, 1981
`
`Sheet 1 of3
`
`4,295,687
`
`M.
`
`[Fig-/
`
`Kw
`\
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`54 I, 6
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`MAXGAIN
`
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`
`NOMGAIN
`
`MIN GAIN
`'
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`200
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`700
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`1200
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`BRAKE MAGNET CURRENT AMPS
`
`BRAKELINE PRESSURE FSlG
`F. 4
`
`Curt - Exhibit 1010 - 2
`
`Curt - Exhibit 1010 - 2
`
`

`

`US. Patent
`
`Oct. 20, 1981
`
`Sheet 2 of 3
`
`4,295,687
`
`
`
`Curt - Exhibit 1010 - 3
`
`Curt - Exhibit 1010 - 3
`
`

`

`U.S. Patent
`
`Oct. 20, 1981
`
`Sheet 3 of 3
`
`4,295,687
`
`
`
`Curt - Exhibit 1010 - 4
`
`Curt - Exhibit 1010 - 4
`
`

`

`4,295,687
`
`ELECTRに BRAKE SYSTEM
`
`2
`FIG. 6 is a sectional view of potentiometer used in
`the present system,
`FIG. 7 is a view partially schematic of a resistor
`employed by the FIG. 6 potentiometer,
`This invention relates to vehicle braking systems and
`5 FIG. 8 is a sectional view of a pressure transducer
`more specifically to electric braking systems to be used
`incorporating the FIG. 6 potentiometer, and
`by a towed vehicle when being pulled by a towing
`FIG. 9 is a view, partially in section, of a brake pedal
`vehicle.
`transducer assembly incorporating the FIG. 6 potenti-
`Controls for electrically operated brakes, such as
`ometer.
`those used for recreational and utility trailers adapted to
`0 Referring first to FIG. 1, the numeral 10 denotes a
`be towed by automobiles and small trucks, must be I
`easily adjustable to accommodate different relative
`brake pedal for conventional brake system for a towing
`vehicle. The brake system comprises a master cylinder
`weights of the towed and towing vehicles. The controls
`11 and hydraulic wheel brakes denoted at 12. The FIG.
`must further be reliable and give the driver of the tow-
`1 electric brake system also includes a pressure trans-
`ing vehicle a feeling of smooth control and positive
`5 ducer assembly 13 which senses the brake system hy-
`brake operation both upon applying th braking effort I
`draulic pressure and in response thereto develops a
`to the towing vehicle and also upon releasing the brak-
`corresponding control signal which is utilized by a
`ing effort.
`control system or controller, shown generally at 14.
`Among the objects and features contemplated with
`This control system 14 controls electric brakes 15 for a
`the present invention is the provision of an electric
`0 towed vehicle such as a trailer. These electric brakes 15
`brake control system for towed vehicles which can 2
`provide a wide range of control over the braking effort
`can be of any well known type and by way of example
`may include an armature disk 16 which may be a verti-
`of a towed vehicle.
`cal surface portion of the usual brake drum 17 and an
`Another object is to provide a simple and reliable
`electromagnet 18, which when energized is magneti-
`electric brake system.
`5 cally attracted to the disk 16 so as to exert a frictional
`Another object is to provide brake short circuit pro- 2
`force on a lever system 19. The lever system 19 then
`tection for an electric brake system.
`A んrther 0可ect is to provide a smooth-acting elec-
`cause brake shoes 20 to be actuated thereby providing a
`braking force in accordance with the magnitude of the
`tric brake system whose braking effort can be varied in
`input sign可．
`accordance with the pressure from a hydraulically op-
`0 FIG. 2 illustrates another embodiment of the inven-
`3
`erated braking system in a towing vehicle.
`tion wherein the brake pedal 10 includes a brake pedal
`A further object is to provide an eledtric brake system
`transducer assembly 21 which develops an input signal
`that is varied in accordance with the force applied to
`in accordance with the amount of foot pedal effort
`the towing vehicle brake pedal.
`exerted by the towing vehicle operator. This input sig-
`A further object is to provide an electric brake system
`5 nal is supplied to the controller 14 and serves the same
`that does not actuate the towed vehicle brakes until a 3
`function as the input signal in the FIG. 1 embodiment.
`certain minimum level of braking effort has been estab-
`Considering next the FIG. 5 circuitry, power for
`lished.
`operation of the circuitry is obtained from a conven-
`A further object is to provide an electric brake system
`tional vehicle battery 22 either when a brake switch 23
`that provides balanced braking between the towed and
`for the towing vehicle is actuated by the brake pedal 10,
`the towing vehicle over a wide range of braking condi- 40
`which also operates brake lights 24, or when a manual
`tions and vehicle weights.
`switch 25 is operated by a hand control 26. The hand
`A further object is to provide an electric brake system
`control 26 is shown in FIG. 1 on the front of the con-
`wherein there is a substantially linear relationship be-
`troller 14. The hand control 26 is movable in the direc-
`tween the towed vehicle brake magnet current and the
`5 tion of the arrow against the bias of a spring (not
`4
`towing vehicle brake force.
`shown). This battery voltage Vb is stabilized through a
`A further object is to provide an electric brake system
`circuit including a voltage dropping resistor 27 and a
`that can be either foot or hand operated from the tow-
`filter capacitor 28. A zener diode 29 is also provided to
`ing vehicle.
`establish the control voltage Vcc at the optimum volt-
`A further object is to provide an electric brake system
`0 age for the circuit components chosen and to prevent
`that incorporates a unique potentiometer that facilitates 5
`transient voltages from damaging components supplied
`achievement of substantial linearity between the towing
`with the voltage Vcc.
`vehicle brake effort and towed vehicle brake current.
`The voltage Vec is applied to the top of a brake force
`A further object is to provide a novel potentiometer
`potentiometer 30 which in the FIG. 1 embodiment is
`for an electric brake system that can be used either with
`5 responsive to the hydraulic brake pressure in the brake
`a braking hydraulic pressure transducer or a brake 5
`system for the towing vehicle and in the FIG. 2 embodi-
`pedal force transducer.
`ment is responsive to the force applied to the brake
`Other objects and features will be apparent from the
`pedal 10 of the towing vehicle. The voltage Vcc is also
`accompanying drawings, in which:
`applied to the top of a hand control potentiometer 31,
`FIG. 1 is a schematic diagram of an electric brake
`which is operated by the hand control 26 so that a hand
`system incorporating the principles of the invention, 60
`override is provided enabling the towed vehicle brakes
`FIG. 2 is a schematic of another embodiment of the
`to be tested or operated separate from the brakes of the
`electric brake system,
`towing vehicle, such as when descending a long grade,
`FIG. 3 is a graph depicting a typical brake force vs.
`or in an emergency when the towing vehicle brakes fail.
`brake magnetic current curve.
`5 In the absence of input from the hand control potenti-
`FIG. 4 is a graph depicting brake current vs. brake 6
`ometer 31, or when the brake force control voltage
`line pressure,
`exceeds the hand control voltage, the brake force con-
`FIG. 5 is a diagram of the circuitry for the electric
`trol voltage will prevail as the input to the controlled
`brake system,
`
`Curt - Exhibit 1010 - 5
`
`

`

`4,295,687
`
`4
`3
`second transistor 61, whose collector is directly con-
`circuits. Either this brake force control voltage or the
`nected to the base electrode of the output transistor 63.
`hand control voltage is supplied to an OR gate 32 which
`The main current path for the output of current now
`includes diodes 33 and 34 and then to a voltage divider
`goes from battery voltage Vb, through a resistor 65 of
`35 comprising a trim or gain potentiometer 36 and a
`very low value, to be described in more detail hereinaf-
`fixed resistor 37. The trim potentiometer 36 is adjusted 5
`by a control knob 38 on the side of the controller 14. As
`ter, through the emitter-collector path of the transistor
`will be explained, the trim potentiometer 36 provides
`63 and through the braking coil 51 and back to the
`gain control for the system.
`grounded side of the battery 22. The effective braking
`A threshold potentiometer 39 is provided in the base
`voltage is now variable width pulses, the duty cycle of
`circuit of a transistor 40 which amplifies the current in 1
`0 which pulses is controlled in accordance with the dis-
`accordance with the voltage applied through the base
`placement of the brake force potentiometer 30 or the
`connection. The output of the transistor 40 is applied
`hand control potentiometer 31 described above. Al-
`directly to the base of another amplifier transistor 41
`though one braking coil is shown, there is usually one
`whose output is applied across a load circuit 42. The
`- braking coil 51 for each wheel to be braked on the
`transistors 40 and 41 function as a zero offset emitter 1
`"towed vehicle.
`follower to provide required impedance match. The
`When braking current from the transistor 63 turns off,
`load circuit 42 comprises a resistor 43 and a parallel
`the diode 71 provides a current path to continue current
`capacitor 44. The output voltage developed across re-
`flow through the brake coil 51. During short duration
`sistor 43 is then applied to one of the inputs to a compar-
`(short nulse) otieration. which is with low braking cur-
`0 二一‘ ‘亡ー二二‘'L ー11 ．一」ニ」＾,．ー．:~1 一ー11..-.c.-.....' 1 ..
`ator 45 in a pulse width modulator, indicated generally 2
`leilL, LIIC じui I CIIし LIIIUu呂11 UIOUC 1J %V1II しCIさC UCIUェC LIIC
`by the reference numeral 46. The pulse width modula-
`next pulse because the energy is consummed by the
`tor 46 consists of a free running oscillator 47 whose
`resistance of the coil 51. During long on-time operation,
`frequency is controlled by an RC circuit 48 consisting
`which is with high braking current, current flows
`of a resistor 49 and a capacitor 50. For the present appli-
`く through the diode 71 until the transistor 63 turns on
`cation, the combination of resistance and capacitance is 2
`Jagain. This feature avoids damaging the transistor 63
`chosen to produce a frequency between 200 and 1000
`and other components in the amplifier 56 and conserves
`hertz. The frequency must be high enough to prevent
`energy.
`chatter at an electrically operated braking coil 51 for
`Further protection for the high current output tran-
`the electromagnet 18 but should not be so high as to
`, sistor 63 is also provided, and this is accomplished by a
`produce radio frequency interference or problems with 3
`diode 73 which has substantial peak current capability.
`high frequency propagation in the wiring of the towing
`If the circuitry is attempted to be connected in reverse
`or towed vehicle.
`fashion to the vehicle battery 2, the diode 73 will draw
`The pulse width modulator also includes compara-
`momentary very high current through the towing vehi-
`tors 53 and 54. Each comparator compares the voltage
`5cle battery 22 and will blow a fuse 75 which is to pre-
`across the capacitor 50 with a reference voltage, which 3
`vent destruction of the transistor 63 and perhaps other
`can be selected portion of the control voltage Vcc, as
`transistors as well.
`determined by a voltage divider 52. Therefore, when
`It is also possible through wear and exposure to the
`the voltage across the capacitor 50 drops below a cer-
`elements that the leads to the braking coil 51 may be-
`tamn percentage of the control voltage Vcc, an output
`come shorted. In the case of short circuit of the output
`from the comparator 53 will be supplied to the oscilla- 40
`lead, the braking system of this invention includes a
`tor 47 and set the oscillator 47 so as to produce a high
`positive-acting short circuit protection system.
`voltage. Similarly, when the voltage across the capaci-
`The short circuit protection circuitry is itidicated by
`tor 50 exceeds a certain percentage of the control volt-
`the reference numeral 77. The main current carrying
`age Vcc an output from the comparator 54 will be sup-
`5circuit for battery 22 is through the emitter-collector
`plied to the oscillator 47 and reset the oscillator 47 so as 4
`path of the transistor 63 and the resistor 65. Upon a
`to produce a low voltage. With these inputs from the
`short circuit condition developing at the output; for
`comparators 53 and 54, the oscillator 47 will develop an
`example, in the leads to the coil 51, the rise in current
`output with a rectangular wave-form which is supplied
`will generate a substantial drop across the resistor 65.
`to the capacitor 50 through the resistor 49. Conse-
`0 This voltage is applied to the base of a transistor 79,
`quently, there will be developed across the capacitor 50 5
`rendering the transistor 79 conductive. The conduction
`a voltage with an approximately triangular wave-form
`of transistor 79 then charges a capacitor 81 through a
`which voltage is supplied to the other of the inputs to
`fairly low resistance resistor 83 to bias another transis-
`the comparator 45.
`tor 85 into conduction. The output of the transistor 85
`The comparator 45 functions to compare the ampli-
`5 develops a turn off voltage across a load resistor 87
`tude of the triangular wave-form with the DC level of 5
`which is then applied to the other input of the AND
`the control signal from the transistor 41 to develop an
`gate 55. This turns off the AND gate 55 so that no
`output pulse width proportional to the DC level at the
`further output pulses are developed until the transistor
`triangular wave-form frequency and an output the aver-
`85 is turned off. The transistor 85 remains conductive
`age value of which is linear with the input.
`0 until the capacitor 81 discharges through a resistor 84
`This pulse-width modulator output is now fed 6
`and a resistor 91. The time constant of this discharge
`through an AND gate 55 to a current amplifier 56 and
`path is approximately 10 times as long as the charging
`is amplified through three stages to provide a high cur-
`time of the RC circuit including the resistor 83 and the
`rent rectangular shaped signal suitable for energizing
`capacitor 81. Therefore, the AND gate 55 is prevented
`the braking coil 51.
`5 from conducting for ten times as long as a momentary
`The pulse width modulated signal output from the 6
`pulse resulting from a short circuit condition. When the
`comparator 45 is applied through a resistor 57 to the
`transistor 85 ceases conduction after the capacitor 81
`base of the transistor 58. This amplifier transistor 58 is
`has discharged, the circuit 77 is ready to disable the
`directly coupled through a resistor 59 to the base of a
`
`Curt - Exhibit 1010 - 6
`
`

`

`4,295,687
`
`6
`5
`In FIG. 9, the details of the brake pedal transducer
`output under another output cycle from the modulator
`assembly 21, which used the potentiometer 30 of FIG. 6
`46.
`are illustrated. This pressure transducer assembly 21 is
`It should be noted that a light emitting diode 93
`adapted to be directly secured to the brake pedal 10, and
`which is connected across the coil and in series with
`5 therefore, the plunger 103 will be displaced in response
`current limiting resistor 95 will be energized as long as
`to pedal force provided by the tow vehicle operator. A
`there is no short, and thus, illuminated. When a short
`base plate 141 has a foot pedal pad; 143 hinged together
`occurs, the diode 93 will not illuminate.
`by a hinge pin 145. The pedal pad 143 is urged away
`The brake force potentiometer 30 may be of the con-
`from the base plate 141 by a spring 147 positioned be-
`struction shown in FIG. 6. The potentiometer 30 has an
`10 tween the pedal pad 143 and the base plate 141. The
`outer case 101 of insulating material, such as phenolic or
`spring 147 can be any suitable type but preferable is of
`other plastic compound. A plunger 103 is movable lon-
`the leaf spring type. The pedal pad 143, which is mov-
`gitudinally through an aperture in the end of the case
`able with respect to the base plate 141, has on one end
`101 and along guideways (not shown). The plunger 103
`an extension 149 which is positioned opposite the
`is under tension of a compression spring 105 which
`15 plunger 103 of the variable potentiometer 30.
`forces the plunger 103 and a shoulder stop 107 on the
`The variable potentiometer 30 is carried in a housing
`plunger 103 towards the case 101. Unless the plunger
`151. The housing 151 is firmly secured and is rigid with
`103 is depressed, the shoulder stop 107 will rest against
`respect to the base plate 141. Upon the application of
`the end of the outer case 101. A plug 109 of a similar
`foot pressure to the pedal pad 143, the pedal pad 143
`insulating material closes the rear end of the case 101
`20 and its extension 149 will pivot around the hinge pin 145
`and provides a suitable guide recess 110 for the spring
`and the extension 149 will cause the plunger 103 to be
`105.
`displaced toward the body of the potentiometer 30 in
`Also contained in the case 101 is a resistance board or
`accordance with the amount of pressure exerted upon
`element 111 shown in FIG. 7. Suitable leads 112, 113
`the pedal pad 143. This pedal 140 can be attached to the
`and 114 are brought to the outside of the case 101 from
`25 brake pedal 10 by positioning the base plate 141 on the
`the ends of the resistance element 111. The plunger 103
`brake pedal 10 with securing straps 153 which are at-
`includes a contact 115 which engages the resistance
`tached to the base が蹴e.
`board 111 as the plunger 103 is moved to provide the
`To explain how the present invention achieves bal-
`desired variable resistance.
`anced braking between the towing and the towed vehi-
`As viewed in FIG. 7, the resistance board 111 in-
`30 dles, it should be understood that to obtain balanced
`cludes a conductive portion 116 which is connected by
`braking, the deceleration of the towed vehicle caused
`the lead 112 to the OR gate 32 in the FIG. 5 circuit, a
`by the towed vehicle brakes alone must equal the decel-
`shorting portion 117, which is connected by the lead
`eration of the towing vehicle provided by the towing
`113 to ground, and a resistance portion 118, which is
`vehicle brakes alone. Therefore, the combined vehicles'
`connected to the top of the potentiometer 30 and thus
`35 deceleration also equals this value. Consequently, the
`the control voltage Vcc. Therefore, as the contact 115
`stopping distance of the combined vehicle will also
`is moved downwardly as observed in FIG. 7, it engages
`equal that of the towing vehicle alone. As the decelera-
`the portions 116, 117 and 118. Since the shorting portion
`tion of each mass due to its braking force alone must be
`equal, the towed vehicle braking force 伊t) must 証ways
`117 is connected to ground, it provides a short circuit to
`resistance portion 118 and no power is applied to the
`40 be proportional to the towing vehicle brake force (Ftv).
`OR gate 32 until the contact 115 moves further down-
`The proportionality constant is the ratio or the towed
`wardly and beyond the portion 117. Thereafter, the
`vehicle weight (Wt) to the towing vehicle weight
`resistance is varied and accordingly the voltage applied
`(Wtv): or, Ft=Wt/Wtv Ftv. Accordingly, a heavy
`to OR gate 32. The purpose of the shorting resistance
`towing vehicle towing a light trailer (towed vehicle)
`portion will be subsequently described in conjunction
`45 requires much less trailer brake force than would be the
`with FIGS. 3 and 4.
`case if the situation were reversed.
`In FIG. 8, the potentiometer 30 is part of the pressure
`With the foregoing in mind, reference is made to the
`transducer 13 which is adapted to be actuated by the
`FIG. 3 graph wherein the ordinates are designated as
`pressure of the hydraulic fluid from the master cylinder
`magnet current in amperes and brake force in pounds.
`11 shown in FIG. 1. The potentiometer case 101 is
`50 As illustrated by the curve, which is typical for an elec-
`carried within a cylindrical housing 121. The case 101
`tric brake, the brake force is somewhat nonlinear for
`of the potentiometer 30 is secured by a circular swage
`low values of current, then becomes linear and finally at
`123 which grips and positions the potentiometer case
`higher values of current again becomes nonlinear.
`101 in a selected position. The physical displacement for
`These deviations are emphasized by the depicted
`the plunger 103 of the potentiometer 30 is derived from
`55 straight line. While the FIG. 3 curve is typical for elec-
`a hydraulic actuator 125. The actuator 125 includes a
`tric brakes, the corresponding curve for a hydraulically
`cylinder 126 which is adapted to be connected at 127 to
`braked vehicle is a substantially straight line. This is
`the master cylinder 11. A piston 128 has a seal 129 at the
`because deceleration of a hydraulically braked vehicle
`has an almost linear relationship with the brake line
`pressure and a stop 130 at the opposite end. The front
`60 pressure. This difference between the electric brake
`end of the piston 128 abuts a separator 131 which is
`curve and the hydraulic brake curve highlights the
`spring biased by two springs 133 and 135. The spring
`problem of providing balanced braking between the
`133 is merely for preventing dimensional stack up prob-
`towing and the towed vehicles.
`lems whereas the rate of the spring 135 affects the appli-
`Referring next to the FIG. 4 graph for the controller
`cation of the towed vehicles brakes 15 when pressure is
`65 14, the depicted lines are labeled "Normal Gain",
`applied to the piston 128.
`"Maximum Gain" and "Minimum Gain". The lines
`The entire assembly 13 of FIG. 8 may be conve-
`labeled "Maximum" and "Minimum" gain indicate the
`niently mounted near the master cylinder 11. A clamp
`sensitivity variations or the specific characteristic be-
`137 may be provided to make the proper mounting.
`
`Curt - Exhibit 1010 - 7
`
`

`

`4,295,687
`
`8
`-continued
`
`Capacitor 81
`Resistor 84
`Resistor 91
`
`.47 mf
`10 Kohms
`10 Kohms
`
`7
`tween the minimum gain line and the maximum gain
`line. This variation in the present invention is provided
`by the adjustment of the gain control knob 38 on the
`side of the controller 14 (See FIG. 1). This control knob
`38 in turn adjusts the trim potentiometer 36, whereas
`the threshold potentiometer 39 establishes the threshold
`To summarize the operation reference is now made to
`or starting point for the gain lines. Therefore, the setting
`FIG. 1. Initially the foot pedal 10 is depressed to actuate
`of the trim potentiometer 36 determines whether opera-
`the towing vehicle hydraulic brakes 12 through the
`tion is at or between the minimum gain and the maxi-
`agency of the master cylinder 11. After the aforedes-
`10
`mum gain lines. The slope of the gain lines is determined
`cribed slight amount of displacement of the foot pedal
`primarily by the spring 135 in the FIG. 8 embodiment
`10 to achieve the 70 PSI brake line pressure, the brake
`and the spring 147 in the FIG. 9 embodiment.
`force potentiometer 30 becomes operative. This control
`As shown in FIG. 4 graph there is no current devel-
`signal is then transferred successively through the OR
`oped until approximately 70 PSI. This is because the
`gate 32, voltage divider network 35, the amplifying
`shorting portion 117 of the resistance element 111 shorts
`stages provided by the transistors 40 and 41, the load
`the output from the potentiometer 30 until this brake
`circuit 42 and to the input of the comparator 45 in the
`line pressure is attained. Current thereafter rises rapidly
`pulse width modulator 46. It is the DC level of the
`along the vertical line to the starting point of one of the
`control signal at the output of the brake force potenti-
`selected gain lines and then increases linearly with the
`ometer 30 that is varied to represent the brake force
`20
`brake line pressure. This abrupt step at 70 PSI over-
`applied to the brake pedal 10 in either the FIG. 1 or the
`comes the nonlinear electric brake characteristic men-
`FIG. 2 embodiments. The DC level of the control sig-
`tioned at low level currents with respect to the FIG. 3
`nal at the output of the trim potentiometer 36 addition-
`graph and also precludes generating undesired brake
`ally reflects the desired proportion of the control signal
`current for the towed vehicle when the brake pedal 10
`to be used to achieve towed vehicle deceleration equal
`25
`of the towing vehicle is being inadvertently depressed
`to the towing vehicle decleration at the weight ratio of
`without intending to develop a brake pressure, i.e., the
`the vehicles with which the controller 14 is being em-
`driver is riding the brake pedal 10 of the towing vehicle.
`ployed. This proportion is determined by the adjust-
`The potentiometer 30 provides this same feature when
`ment of the potentiometer 36.
`employed with the FIG. 9 embodiment.
`In the pulse width modulator 46, the RC circuit 48
`30
`Also, as can now be appreciated, after the initial step
`and the free running oscillator 47 combine with the
`on the FIG. 4 graph, linearity has been achieved both
`comparators 53 and 54 to develope a triangular wave
`with the FIG. 8 embodiment and the FIG. 9 embodi-
`voltage at the desired frequency. The triangular is then
`ment. Therefore, as determined by the towed vehicle!-
`supplied to the other input to the comparator 45 where
`towing vehicle weight ratio desired, the trim potenti-
`the amplitude of the triangular waveform is compared
`35
`ometer 36 is adjusted by the control knob 38 within the
`with the DC level of the control signal. A pulse width
`range provided between the minimum and maximum
`modulated output voltage is developed with a pulse
`gain lines in FIG. 4. By way of example and without
`width proportional to this DC level and at the triangu-
`limitation, a weight ratio of 0.5 to 2.0 has been deter-
`lar waveform frequency.
`mined acceptable. This weight ratio adjustment is
`40
`The modulated output from the comparator 45 is
`achieved without the need for an external compensating
`approximately linear with input and is supplied by way
`resistor.
`of the AND gate 55 to the current amplifier 56. The
`In an actual embodiment of FIG. 1, the circuit corn-
`current amplifier 56 functions to provide an output of
`ponents were as follows:
`up to 15 amperes or more. Thus, the towed vehicle
`brakes are actuated by variable width voltage pulses,
`the duty cycle of which is controlled by the displace-
`ment of the brake pedal 10.
`The foregoing operation can be achieved with the
`hand control 26 so as to actuate the towed vehicle
`brakes 15 directly without actuating towing vehicle
`brakes. The hand control 26 permits separate operation
`of towed vehicle brakes for testing or emergency pur-
`poses. To operate, the hand control 26 on the controller
`14 in FIG. 1 is moved in the direction of the arrow
`against a return spring bias. This adjusts the hand con-
`trol potentiometer 31 and the resultant control signal at
`the DC level determined by setting of the potentiometer
`31 is, as before described, transferred to the OR gate 32
`where it will prevail as long as it exceeds the DC level
`60
`from the potentiometer 30.
`If the output pulse from the current amplifier exceeds
`a selected current value; e.g., 20 amps the short circuit
`protection circuit 77 will become energized to develop
`an output cut off pulse which is transferred to the AND
`gate 55 in the pulse width modulator 46. This cut off
`pulse will turn off the AND gate 55 and shut down the
`modulator 46.
`What is claimed is:
`
`Resistor 27
`Capacitor 28
`Zener diode 29
`Potentiometer 30
`Diode 33 and 34
`Potentiometer 36
`Resistor 37
`Potentiometer 39
`Transistor 40
`Transistor 41
`Resistor 43
`Capacitor 44
`Pulse Width
`Modulater
`Resistor 49
`Capacitor 50
`Resistor 57
`Transistor 58
`Resistor 59
`Transistor 61
`Transistor 63
`Resistor 95
`Diode 71
`Diode 73
`Transistor 79
`Resistor 83
`Transistor 85
`Resistor 87
`
`5
`
`15
`
`45
`
`50
`
`55
`
`65
`
`150 0hms
`10 mf
`IN4739
`5000 ohms
`1N4148
`10 Kohms
`5.6 Kohnis
`220 Kohms
`2N4126
`2N4 124
`2.4 Kohms
`1.0 mf
`LM556
`
`39 Kohms
`.033 mf
`2 Kohms
`2N4401
`100 0hms
`T1P42
`2N5301
`680 0hms
`6amp., 400 piv
`3amp., 50 piv
`2N4403
`200 0hms
`2N4124
`4.7 Kohms
`
`Curt - Exhibit 1010 - 8
`
`

`

`10
`9
`1. A braking system for controlling electrically oper-
`having two inputs and an output, means applying such
`pulsating signal to one of said gate inputs, means for
`ated brakes for a driver controlled vehicle comprising
`braking means electrに姐y ene博zable 伽r ap叫ying a
`energizing the towed vehicle brakes from said gate
`output, and wherein said inhibiting means includes
`braking force to the brakes, an electric energy source,
`means connected to the other gate input for blocking
`control means selectively adjustable by the driver in 5
`said gate output in response to such sensed current
`accordance with a desired braking force, said control
`exceeding said predetermined maガmum current.
`means developing a control signal only after a predeter-
`4. The brake system of claim 3; wherein said inhibit-
`mined initial adjustment that varies rapidly from a
`ing means includes means for inhibiting the pulsating
`threshold magnitude to a certain magnitude and thereaf-
`signal for a predetermined limited time interval
`ter varies linearly with a further adjustment thereof, 10
`
`whereby the pulsating signal is reapplied after said lim-
`controller means operative to couple said braking
`ited time interval to reenergize the towed vehicle
`means to said source in response to such control signal,
`said controller means developing a pulsating ou中ut for
`brakes until such sensed current level again exceeds said
`predetermined maximum current.
`energizing said brake means having a predetermined
`5. A braking system for controlling electrically oper-
`frequency and having a pulse width determined by the 15
`ated brakes for a driver controlled vehicle comprising
`magnitude of such control signal, and excessive current
`protectio