5,620,236
`[11] Patent Number:
`[19]
`Unlted States Patent
`
`McGrath et a1.
`[45] Date of Patent:
`Apr. 15, 1997
`
`US005620236A
`
`[54] ELECTRONIC TRAILER BRAKE
`CONTROLLER
`
`[75]
`
`Inventors: Michael C. McGrath, Farmington
`Hills; Wayne M. Groleau, Novi;
`Michael A. Hedding, Canton; Brian J.
`.
`.
`.
`Stockford, Ann Arbor, Davrd Sullivan,
`Bnghtona 811 01° MICh-
`
`[73] Assignee: Hayes Wheels International, Inc.,
`Romulus, Mich.
`
`.
`..
`,
`[21] Appl N0 . 313 703
`
`a
`
`[22]
`
`Filed:
`
`Sep. 27 1994
`’
`...................................................... B60T 13/00
`Int. Cl.
`[51]
`..............
`303/7; 303/20; 303/124
`[52] us. Cl.
`
`[58] Field of Search ............................... 303/7, 20, 3, 15,
`303/123, 124: 155, 24-1
`
`[56]
`
`References Cited
`U. S. PATENT DOCUMENTS
`
`2/1970 Umpleby -
`3,497,265
`313;? 113‘;le -hak t al
`33323513;
`0 me
`e
`,
`,
`3,780,832 12/1973 Marshall .
`3,909,075
`9/1975 Pittet, Jr. et a1.
`
`.
`
`.
`
`.
`
`TOWING VEHICLE
`
`ABS
`
`257.
`
`.
`
`.
`
`‘
`
`'
`
`3,967,863
`7/1976 Tomecek et a1.
`3,981,542
`9/1976 Abrams et a1.
`.
`3,981,544
`9/1976 Tomecek et a1.
`2:32:23 1313:? SID/gar Ital
`’
`’
`cc. er e
`1352::
`7/1383 Eran et a1.
`'
`,
`,
`ckert et a1.
`4,856,850
`8/1989 Aichele et a1.
`5,050,937
`9/1991 Eccleston.
`5,149,176
`9/1992 Eccleston .................................. 303/20
`5,333,940
`8/1994 Topfer ......................................... 303/7
`5,333,948
`8/1994 Austin et a1.
`.
`5,352,028
`10/1994 Eccleston.
`
`.......................... 303/962
`_
`
`5,427,440
`
`6/1995 Ward 6t a1.
`
`............................. 303/7 X
`
`Primary Examiner—Lee W. Young
`Attorney, Agent, or Firm—MacMillan, Sobanski & Todd
`
`ABSTRACT
`[57]
`An electronic brake controller for actuating electric wheel
`brakes of a towed vehicle in response to actuation of the
`brakes of an associated towing vehicle. The brake controller
`includes a sensor for producing a brake control signal which
`is representative of the desired braking of the towed vehicle.
`The controller also includes a microprocessor for responsive
`to the brake control signal for generating an output signal for
`actuating the electric wheel brakes of the towed vehicle.
`
`9 Claims, 5 Drawing Sheets
`
`TOWED VEHICLE
`
`2 5
`.
`.
`excl
`'
`
`25
`
`|I
`
`Curt - Exhibit 1004 - 1
`
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`
`PEDAL
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`t '
`22
`
`2‘
`
`
`
`
`Curt - Exhibit 1004 - 1
`
`

`

`US. Patent
`
`Apr. 15, 1997
`
`Sheet 1 of 5
`
`5,620,236
`
`TOWING VEHICLE
`
`TOWED VEH!CLE
`
`HYDRAULIC
`BRAKE
`SYSTEM
`
`—
`
`VEHICAL
`BRAKE
`PEDAL
`
`'
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`
`cm
`
`25
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`
`urt - Exhibit 1004 - 2
`
`Curt - Exhibit 1004 - 2
`
`

`

`US. Patent
`
`Apr. 15, 1997
`
`Sheet 2 of 5
`
`5,620,236
`
`
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`Curt - Exhibit 1004 - 3
`
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`Curt - Exhibit 1004 - 3
`
`
`
`

`

`US. Patent
`
`Apr. 15, 1997
`
`Sheet 3 of 5'
`
`5,620,236
`
`
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`rl
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`i
`
`]
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`Curt - Exhibit 1004 - 4
`
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`Curt - Exhibit 1004 - 4
`
`

`

`US. Patent '
`
`Apr. 15, 1997
`
`Sheet 4 of 5
`
`5,620,236
`
`.IIIIIIII-llllllllllIll-Illllllllllllllll ———————-_——————————————___—————_————————-
`
`-:£"IG.BB
`
`Curt - Exhibit 1004 - 5
`
`Curt - Exhibit 1004 - 5
`
`

`

`US. Patent
`
`Apr. 15, 1997
`
`Sheet 5 of 5
`
`5,620,236
`
`TOWING VEHICLE
`
`/—_A—-—\
`
`' ABS
`
`~
`
`,.
`
`252.
`
`”3mm -
`SYSTEM
`20
`
`VEHICAL
`
`PEDAL
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`
`'
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`
`TOWED VEHICLE
`
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`Curt - Exhibit 1004 - 6
`
`Curt - Exhibit 1004 - 6
`
`

`

`5,620,236
`
`1
`ELECTRONIC TRAILER BRAKE
`CONTROLLER
`
`BACKGROUND OF THE INVENTION
`
`5
`
`2
`of the pulse tr証n in proportion to the magnitude of the brake
`control signal. Thus, the duty cycle of the pulse tr証n
`corresponds to the amount of braking effort desired.
`Electronic brake controllers further include an output
`stage which is electric証ly connected to the output of the
`pulse width modulator. The output stage typically has one or
`more power transistors which are connected between the
`towing vehicle power supply and the towed vehicle brake
`electromagnets. The power transistors んnction as an elec-
`tronic switch for supplying electric current to the towed
`vehicle brakes.
`The output stage is responsive to the pulse width modu-
`lator output signal to switch the power transistors between
`conducting, or "on", and non-conducting, or "off", states. As
`the output transistors are switched between their on and off
`states in response to the modulator output signal, the brake
`current is divided into a series of pulses. The power supplied
`to the towed vehicle brakes and the resulting level of brake
`application are directly proportional to the duty cycle of the
`modulator generated output signal.
`
`SUMMARY OF THE INVENTION
`
`The present invention relates in general to an electronic
`controller for energizing electric証ly operated br水es in a
`towed vehicle and, in particular, to an electronic brake
`controller which is responsive to the brake actuation of the
`towing ve血cle for supplying electric current to the towed
`vehicle brakes.
`Towed ve屈cles, such as recreational and utility trailers
`adapted to be towed by automobiles and small trucks, are
`commonly provided with electric brakes. The electric brakes
`generally include a pair of brake shoes which, when actu-
`ated, friction証ly engage a brake drum. An electromagnet is
`mounted on one end of a lever to actuate the brake shoes.
`When an electric current is applied to the electromagnet, the
`electromagnet is 血awn against the rotating brake drum
`which pivots the lever to actuate the brakes. Typically, the
`braking force produced by the brake shoes is proportional to
`the elec垣c current applied to the electromagnet. This elec-
`tric current can be relatively large. For example, the electric
`The present invention relates to an improved electronic
`25
`brakes on a two wheeled trailer can draw six amperes of
`brake controller for actuating elec血c wheel brakes of a
`current when actuated and the electric brakes on a four
`towed vehicle in response to actuation of the brakes of an
`wheeled trailer can draw 12 amperes of current.
`associated towing vehicle which includes a microprocessor
`Automotive industry standards require that electrically-
`for controlling the flow of electric current to the electric証ly
`actuated vehicle brakes be driven against the ground poten-
`30 actuated wheel brakes.
`tial of the vehicle power supply. Accordingly, one end of
`The electronic brake controller includes a sensor for
`each of the towed vehicle brake electromagnets is electri-
`producing a brake control signal which is representative of
`cally connected to the towed vehicle ground and the towed
`the desired braking of the towed vehicle. The controller also
`vehicle ground is electrically connected to the towing
`includes a control means responsive to the brake control
`vehicle ground. The other end of each of the brake electro-
`signal for generating an output signal for actuating the
`magnets is electrically connected through an electric brake
`elec血c wheel比血es of the towed ye血cle. The output sign証
`controller to the towing vehicle power supply.
`is related to the brake control signal by a controller gain,
`Various electric brake controllers for towed vehicle elec-
`which is incrementally adjustable between a plurality of
`tric brakes are known in the art. For example, a variable
`individual gain settings. The controller 血rther includes an
`resistor, such as a rheostat, can be connected between the
`operator actuated means for selecting one of the plurality of
`towing vehicle power supply and the brake electromagnets.
`gain settings and a display means for indicating to the
`The towing vehicle operator manually adjusts the variable
`operator the selected gain setting.
`resistor setting to vary the amount of current supplied to the
`Another feature of the brake controller is a control circuit
`brake electromagnets and thereby control the amount of
`which is connected to the vehicle battery and is responsive
`braking force developed by the towed vehicle brakes.
`to said brake control signal for generating the output signal.
`Also known in the art are more sophisticated electric
`The control circuit includes means for disconnecting the
`brake controllers which include electronics to automatically
`vehicle battery from at least selected portions of the control
`supply current to the brake electromagnets when the towing
`circuit in the event the control circuit has rmaii,ed unactu-
`vehicle brakes are applied. Such electronic brake controllers
`ated for a predetermined time period.
`typically include a sensing unit which generates a brake
`50
`control signal correspon山ng to the desired braking effort.
`The brake controller includes means responsive to the
`actuation of a zero adjust switch for measuring the voltage
`For example, the sensing unit can include a pendulum which
`is 血splaced from a rest position when the towing vehicle
`level of the brake control signal and generating a zero adjust
`signal in response thereto. The control means are responsive
`decelerates and an electronic circuit which generates a brake
`control signal which is proportion証 to the pendulum dis-
`to the zero adjust voltage to adjust the brake control signal.
`55
`placement. One such unit is 血sclosed in U.S. Pat. No.
`The brake controller can further include a means for
`producing a manual brake control signal which is carried by
`4,721,344. Alternately, the hydraulic pressure in the towing
`a remote housing. The means for producing a manual brake
`vehicle's braking system or the pressure applied by the
`control signal is actuated by the operator to generate a
`driver's foot to the towing vehicle's brake pedal , can be
`manual brake control signal. The control means is respon-
`sensed to generate the brake control signal.
`sive to at least one of the manual or the sensor brake control
`Known electronic brake controllers also usually include
`signals.
`an analog pulse width modulator. The input of the pulse
`width modulator is electric証ly connected to the sensing unit
`The brake controller also can include means for generat-
`ing a triggering signal when a brake pedal of the towing
`and receives the brake control signal therefrom. The pulse
`65 vehicle is actuated. The control means is responsive to the
`width modulator is responsive to the brake control signal for
`triggering signal and the brake control signal for generating
`generating an output signal comprising a fixed frequency
`the output signal. Furthermore, the brake controller includes
`pulse train. The pulse width modulator varies the duty cycle
`
`10
`
`15
`
`20
`
`35
`
`40
`
`45
`
`60
`
`Curt - Exhibit 1004 - 7
`
`

`

`5,620,236
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`FIG. 1 is a schematic diagram illustrating an electric brake
`system which includes an electro血c brake controller accord-
`ing to the present invention.
`FIG. 2 is a block diagram of the electronic brake control-
`ler shown in FIG. 1.
`FIGS. 3A and 3B are a schematic circuit diagrams illus-
`trating a preferred embodiment of the electronic brake
`controller shown in FIG. 2.
`FIG. 4 is a schematic diagram of an alternate embodiment
`of the electronic brake controller shown in FIG. 1.
`
`4
`3
`power also is supplied through the second line 28 to the
`means for limiting the voltage level of said triggering signal
`controller 11 when the brake light switch 22 is closed.
`supplied to said control means.
`The invention 証so envisions the electro血c controller
`The brake controller 11 is normally operated in an auto-
`coupled to an anti-lock br水e system for receiving data
`matic mode wherein the towed vehicle brakes 13 and 14 are
`5 automatically actuated by the controller 11 when the towing
`concerning the operation of the towing vehicle. Accordingly,
`the controller controls the electrically actuated br水es of the
`vehicle brakes are actuated. The automatic mode is activated
`towed ve屈cle as a function of the received data.
`upon closure of the brake light switch 22. When operating in
`the automatic mode, the controller 11 senses braking force
`Other objects and advantages of the invention will
`applied to the towing vehicle and supplies an electric current
`become apparent from the following detailed description of
`10 through line 12 to actuate the towed vehicle brakes. The
`the invention and the accompanying 止awings.
`electric current is directly proportional to the braking force
`applied to the towing vehicle.
`In some instances, it may be desirable to actuate only the
`towed vehicle brakes 13 and 14. This may be desirable, for
`15 example, to stabilize the towed vehicle against vacillations
`or swinging caused by strong side winds. Therefore, the
`brake controller 11 also includes a manual mode of opera-
`tion. Accordingly, a manual switch 30 is provided on the
`electronic controller 11 to allow the vehicle driver to actuate
`the towed vehicle brakes 13 and 14 without applying the
`towing vehicle brakes. Pressing the manu証 switch 30 m血
`tiates the manual mode of operation. The amount of electric
`current supplied to the towed vehicle brakes 13 and 14 is
`proportional to the displacement of the manual switch 30. If
`the manual switch 30 is pressed while the brake pedal 21 is
`depressed, the manual operating mode overrides the auto-
`matic operating mode.
`In accordance with one feature of the present invention,
`Referring now to the drawings, there is shown in FIG. 1
`the controller 11 also is provided with a hand held manual
`a schematic diagram illustrating an electric brake system for
`remote switch 31. The manual remote switch 31 includes a
`a towed vehicle (not shown), shown generally at 10, which
`push-button which can be used to initiate the manual mode
`utilizes an electronic brake controller 11 embodying the
`of operation. Upon pressing the push-button, the manual
`principles of the present invention. The brake controller 11
`remote switch 31 functions the same as the manual switch 30
`is typically located in a towing vehicle (not shown), usually
`to actuate the towed vehicle brakes. When either the manual
`being mounted beneath the towing vehicle dashboard. When
`3 5
`actuated, the controller 11 んnctions to supply an electric
`switch 30 or the manual remote switch 31 are pressed, the
`current t血ough line 12 to energize electric brakes 13 and 14
`towing vehicle and towed vehicle brake lights 24 and 25 are
`illuminated.
`which brake the wheels of the towed vehicle (not shown).
`The controller 11 釦rther includes a gain control push-
`The electric brakes 13 and 14 each include a pair of brake
`button 32 mounted on a front surface thereof. The gain
`shoes 15 and 16 which, when actuated by a lever 17, are
`control push-button 32 allows the vehicle driver to vary the
`expanded into contact with a brake drum 18 for braking the
`overall gain of the brake control system 10 to compensate
`wheels of the towed vehicle. A separate electromagnet 19 is
`for different loads carried in the towed vehicle. For example,
`mounted on an end of each of the brake actuating levers 17.
`if the load in the towed vehicle is increased, it is necessary
`Each electromagnet 19 is positioned to abut the generally
`to increase the braking force applied to the towed vehicle
`flat side of the brake drum 18. As an electric current is
`relative to the braking force applied to the towing vehicle.
`passed through each of the electromagnets 19, the electro-
`Conversely, if the load in the towed vehicle is decreased, it
`magnets 19 are drawn into contact with the brake drums 18
`is necessary to decrease the braking force applied to the
`and the resulting drag pivots the levers 17 to engage the
`towed vehicle relative to the braking force applied to the
`brake shoes 15 and 16 in a conventional manner. It will be
`towing vehicle. By adjusting the gain control, the electric
`appreciated that, while FIG. 1 shows two sets of brakes 13
`S 0
`current supplied by the electronic controller 11 to the brake
`and 14, the invention also can be applied to towed vehicles
`electromagnets 19 can be increased or decreased for any
`having more than two sets of brakes.
`given braking requirement.
`The towing vehicle typically includes a convention証
`In the preferred embodiment, the gain control adjustment
`hydraulic brake system 20 which is actuated when a brake
`55 o可y applies to the automatic mode of operation. The manual
`pedal 21 is depressed by a vehicle driver. The brake pedal 21
`mode of operation is not affected by the gain setting. The
`is coupled to a brake light switch 22. When the brake pedal
`gain control push-button 32 also is used to check the current
`21 is depressed, the switch 22 is closed and power from a
`gain setting of the brake control system and to awaken the
`vehicle power supply 23, shown as a storage battery in FIG.
`1, is supplied to one or more towing vehicle brake lights み
`controller 11 from a sleep mode, which is described below.
`and one or more towed vehicle brake lights 25. The vehicle
`The controller 11 also includes an array of light emitting
`power supply 23 is also connected by a first line 26 through
`diodes (LED's) 33 mounted upon the front surface thereof.
`a circuit breaker 27 to the controller 11. Power is continu-
`The LED's 33 provide a visual indication of the controller
`ously supplied to the controller 11 through the first line 27.
`gain setting to the vehicle driver. During towed vehicle
`It will be appreciated that, while a circuit breaker 27 is
`brake applications, a combination of the LED's 33 are
`shown in FIG. 1, a fuse or other overcurrent protection
`65 illuminated to display the magnitude of the brake applica-
`device can be used. A second line 28 connects the brake light
`tion. The LED's are also illuminated when the gain is
`side of the brake light switch 22 to the controller 11. Thus,
`adjusted.
`
`20
`
`25
`
`30
`
`40
`
`45
`
`60
`
`Curt - Exhibit 1004 - 8
`
`

`

`5,620,236
`
`5
`
`20
`
`25
`
`30
`
`6
`5
`hereby incorporated by reference. The automatic mode
`A plurality of ground connections are shown schemati-
`brake control signal generator 52 amplifies the voltage
`cally in FIGS. 1 through 3 for both the towing and towed
`generated by the Hall effect device. The amplified voltage
`vehicles. It will be appreciated that both towing and towed
`vehicles usually have a common vehicle ground, typic証ly
`comprises an analog brake control signal which is supplied
`the chassis and/or the body. Thus, the individu証 ground
`through line 53 to the input of the first channel of the A/D
`converter 49.
`connections shown in FIG. 1 are connected to the cone-
`In the preferred embodiment, the generator 52 also
`sponding vehicle common ground. The towing and towed
`ve血cle common grounds are joined through the connection
`includes a zero adjust circuit which provides a zero adjust-
`of the towed vehicle tongue (not shown) and the towing
`ment of the deceleration sensor. The zero adjust circuit is
`vehicle hitch (not shown). A supplemental electric誠 con-
`10 connected to the microprocessor 45 by the line 54. While
`one line 54 is shown in FIG. 2 for clarity, in the preferred
`nector (not shown) also may connect the towing vehicle
`embodiment, the line 54 comprises a plurality of individual
`common ground to the towed vehicle common ground.
`lines. As will be explained below, the zero adjust circuit is
`A block diagram of the electronic brake controller 11 is
`shown in FIG. 2 and includes sever証 unique features.
`actuated over line 54 by the microprocessor 45 following
`15 initial energization of the controller 11 or when the gain
`Components of the electric brake system 10 which are
`push-button 32 is held in for a predetermined time period.
`identical to components shown in FIG. 1 have the same
`The manual switch 30 is connected by line 55 to the input
`numerical designators in FIG. 2. The electronic brake con-
`of the second channel of the A/D converter 48. As will be
`troller 11 is contained in a housing 40 which is outlined by
`a dashed line in FIGS. 2 and 3.
`described below, pressing the manual switch 30 generates an
`The controller housing 40 cont証ns a plurality of んnc-
`analog manual brake control signal. The manual brake
`control signal also can be generated by the manual remote
`tional blocks. Each of the functional blocks represents a
`subcircuit w班ch is included in the electronic brake control-
`switch 31. The manual remote switch 31 is connected by a
`pair of leads 56 and 57 to the manual switch 30. In the
`ler 11. As shown in FIG. 2, each functional block receives
`preferred embodiment, the ends of the leads 56 and 57 are
`input signals from the left and transmits output signals to the
`connected to a male plug (not shown). The male plug is
`right. Additionally, as shown in FIG. 2, power is supplied to
`the top of each 加nction証 block.
`received by a jack mounted on a side of the controller
`housing 40. Thus, the manual remote switch 31 can be
`The brake controller 11 utilizes a preprogrammed eight bit
`removed from the controller 11. As will be explained below,
`microprocessor 45 which can receive two digitized brake
`the manual switch 30 continues to function when the manual
`control signals representing desired braking levels. Under
`remote switch 31 is removed.
`normal operating conditions, the microprocessor 45 receives
`The controller 11 further includes a brake driver 59
`an automatically generated digitized brake control signal at
`having an input connected by line 60 to the microprocessor
`an automatic mode input pin 46. Alternately, the micropro-
`output pin 48. The brake driver 59 amplifies the micropro-
`cessor 45 can receive a manually generated digitized brake
`cessor output signal. The brake driver 59 has an output
`control at a manual mode input pin 47. As described above,
`35
`connected by line 61 to a brake switching circuit 62. The
`if the microprocessor 45 simultaneously receives automatic
`brake switching circuit 62 includes a plurality of P-channel
`and manual brake control signals, the microprocessor 45
`responds o凪y to the manual signal, providing an ovethde
`MOSFET's which function as a electronic switches. The
`MOSFET's are connected between the towing vehicle
`capability. In response to the brake control signals, the
`power supply 23 and the towed vehicle brake electromag-
`microprocessor 45 generates an output signal at an output
`nets 19.
`pin 48. The output signal comprises a square wave pulse
`train. The pulse tr証n has a duty cycle directly proportional
`The brake switching circuit 62 receives an amplified
`output signal from the brake driver 59. The MOSFET's in
`to the level of the brake control signal. As will be described
`below, the pulse train is used to control the electric current
`the switching circuit 62 change between conducting, or
`"on", and non-conducting, or "off", states in accordance
`which actuates the towed vehicle brakes 13 and 14.
`with the amplified output signal to control the flow of current
`The controller 11 includes a two channel analog to digital
`to the brake electromagnets 19. As the duty cycle of the
`(AID) converter 49 which is electrically coupled to the input
`output signal increases, the MOSFET' s are on for a greater
`pins 46 and 47 of the microprocessor 45. The A/D converter
`percentage of time, allowing more power to be supplied to
`49 is a conventional, commercially available device which
`changes analog brake control signals to digit証 signals. The
`the brake electromagnets 19 and thereby causing a greater
`brake application.
`output of the first channel of the AID converter 49 is
`The controller 11 also includes a brake light driver 63
`connected by line 50 to the microprocessor automatic mode
`which has an input connected by line 64 to a microprocessor
`input pin 46. Similarly, the output of the second channel of
`brake light actuation pin 65. The brake light driver 63 has an
`the A/D converter 49 is connected by line 51 to the micro-
`output which is connected to a brake light relay 66 by line
`processor manual mode input pin 47.
`67. The brake light relay 66 is connected to the towing
`A brake control signal generator 52 is connected by line
`vehicle and towed vehicle brake lights 24 and 25 by line 68.
`53 to the input of the first channel of the A/D converter 49.
`As will be explained below, the brake light driver 63 and
`The generator 52 senses a change in a towing vehicle
`brake light relay 66 respond to the voltage on the brake light
`parameter and automatically generates an analog brake
`activation pin 65 to illuminate the brake lights 24 and 25
`control signal which is proportional to the braking force
`60
`when the manual mode of operation is actuated.
`applied to the towing vehicle. As will be explained below,
`The controller 11 further includes an automatic mode
`various devices can be used for generating the brake control
`伍gger 70 which enables the automatic mode of the con-
`signal. In the preferred embodiment, a deceleration sensor
`troller 11. The trigger 70 has an input which is connected by
`(not shown) comprising a pendulum which cooperates with
`65 line 71 to the brake light side of the towing vehicle brake
`a Hall effect device to generate a voltage proportional to the
`light switch 22. The automatic mode trigger 70 senses when
`deceleration of the towing vehicle is used. Such a decelera-
`the brake switch 22 has been closed and generates a trigger
`tion sensor is described in U.S. Pat. No. 4,726,627, which is
`
`40
`
`45
`
`50
`
`55
`
`Curt - Exhibit 1004 - 9
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`

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`エ620,236
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`5
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`15
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`20
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`25
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`0
`3
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`7
`voltage. The trigger voltage is applied through line 72 to a
`trigger voltage input pin 73 of the microprocessor 45. A
`trigger voltage must be present at the input pin 73 for the
`microprocessor 45 to respond to an automatically generated
`brake control sign証. When both a trigger voltage and an
`automatically generated brake control sign司 are simulta-
`neously present at their respective microprocessor input pins
`73 and 46, the microprocessor 45 will generate an output
`signal for actuation of the towed ve血cle brakes 13 and 14.
`Upon release of the brake pedal 21, the brake light switch
`10
`22 opens. This deactivates the automatic mode trigger 70
`and removes the trigger voltage from the trigger voltage
`input pin 73. Accordingly, the microprocessor 45 ceases
`generation of the output signal allowing release of the towed
`vehicle brakes 13 and 14. The output signal generation will
`cease even if the brake control signal rem証ns at input pin 73.
`The automatic mode trigger 70 causes the microprocessor
`45 to filter out erroneous brake control signals. Such signals
`can be generated by the automatic mode brake control signal
`generator 53 in response to motion of the towing vehicle
`while traversing a rough road. If the brake pedal has not been
`depressed to cause the automatic mode 垣gger 70 to generate
`a trigger voltage, the microprocessor 45 will not respond to
`these brake control signals. Thus, the towed vehicle brakes
`13 and 14 are not erroneously actuated due to motion of the
`towing vehicle.
`A regulated power supply 74 has an output connected by
`line 75 to a power supply pin 76 of the microprocessor 45.
`The input side of the regulated power supply 74 is connected
`by a supply line 77 through the circuit breaker 27 to the
`towing vehicle power supply 23. The regulated power
`supply provides power at a regulated voltage level to the
`microprocessor 45 and other selected circuits in the control-
`ler 11. In the preferred embodiment, the regulated voltage
`level is five volts.
`The output of the regulated power supply 74 also is
`connected by a line 78 to the norm証ly open terminal of a
`single pole double throw (SPDT) switch 79. The center pole
`of the switch 79 is connected by a line 80 to a gain input pin
`81 of the microprocessor 45. The switch 79 is mechanically
`coupled to the gain control push-button 32. When the gain
`control push-button 32 is pressed, the switch 79 is closed,
`applying the regulated voltage to the microprocessor input
`pin 81. Thus, the switch 79 provides an interface between
`the vehicle driver and the microprocessor. As will be
`described below, the vehicle driver can incrementally
`change the system g証n by pressing the g証n control push-
`button 32.
`The output of the regulated power supply 76 is connected
`by line 84 to a reset circuit 85. The reset circuit 85 has an
`output which is connected to a reset pin 86 of the micro-
`processor 45 by a line 87. The reset circuit 85 functions to
`reset the microprocessor 45 when power is initially applied
`to the controller 11. The reset circuit 85 also resets the
`microprocessor 45 following restoration of power as, for
`example, can occur following maintenance of the towing
`vehicle or the controller 11.
`The microprocessor 45 actuates a light display 90 through
`a line 91. While one line 91 is shown in FIG. 2 for clarity,
`60
`the line 91 comprises a plurality of individu司 lines in the
`preferred embo山ment. The light display 90 includes the
`array of LED's 33 mounted in the front panel of the
`controller 11. As described above, the microprocessor 45 is
`operable to illuminate selected LED's 33 to provide a visual
`indication of braking level or gain setting to the vehicle
`driver.
`
`8
`The controller 11 has a sleep mode, or standby, circuit 95.
`As will be explained below, the sleep mode circuit 95 is an
`electronic switch which controls the supply of regulated
`power to selected portions of the controller 11. The sleep
`mode circuit 95 receives power from the regulated power
`supply 76 through a line 96. The sleep mode circuit 95 has
`an input which is connected by line 97 to a sleep mode
`output pin 98 of the microprocessor 45 and an output
`connected to line 99. The sleep mode circuit 95 is actuated
`after a predetermined time has elapsed following the last
`brake application. Upon actuation, the sleep mode circuit 95
`deenergizes selected portions of the controller 11 by shutting
`off the supply of regulated power through output line 99. In
`the preferred embodiment, the selected portions include the
`brake light driver 63, brake driver 59, light display 90, A/D
`converter 49, brake control signal generator 52 and manual
`remote switches 30 and 31. The sleep mode circuit 95
`conserves the towing vehicle power supply 23 during pen -
`ods of towing vehicle inactivi呼 Upon operation of the
`towing vehicle brakes or the gain control push-button 32, the
`microprocessor 45 causes the sleep mode circuit 95 to
`restore power to the deenergized portions of the controller
`11.
`A schematic circuit diagram of the brake controller 11
`shown in FIG. 2 is illustrated in FIG. 3. Components of the
`electric brake system 10 which are identical to components
`shown in FIGS. 1 and 2 have the same numerical designators
`in FIG. 3.
`As indicated above, the brake controller 11 includes a
`microprocessor 45. The microprocessor 45 is an eight bit
`integrated circuit which includes a memory. The micropro-
`cessor is programmed to control operation of the electric
`brake system 10. In the preferred embo山ment, a conuner-
`emily available microprocessor from Texas Instruments in
`Houston, Tex., is used. For clarity in FIG. 3, a conventional
`crystal circuit, which is extern証ly connected to the micro-
`processor 45 to set the internal operating frequency, is not
`shown. Similarly, any unused microprocessor connector
`pins are not shown. Following conventional practice, such
`unused pins are connected to circuit ground through a
`resistor. Ad山tionally, the arrangement of microprocessor
`pins shown in FIG. 3 does not necessarily correspond to the
`actual physical arrangement of the pins on the microproces-
`sor package.
`In the preferred embodiment, the microprocessor 45 is
`programmed during fabrication by loading specific software
`into the microprocessor memory. The software includes the
`operating instructions which control the response of the
`microprocessor 45 to various input signals. The software
`also includes a table of preset gain values for the brake
`system 10. The preset gain values range from a minimum to
`a maximum and include a default value. The default value is
`selected by the microprocessor 45 following initial energi-
`zation or reenergization. As will be explained below, the
`response of the brake system 10 can be tailored by the
`vehicle driver selecting a particular gain value to match a
`particular load. Alternately, a read only memory (ROM)
`which is preprogrammed with the ope