United States Patent
`
`[19]
`
`4,721,344
`Date of Patent:
`Frait et 31.
`[45]
`Jan. 26, 1988
`
`[11]
`
`Patent Number:
`
`[54] ELECTRIC BRAKE CONTROLLER
`
`[75]
`
`Inventors:
`
`John S. Frait, Ann Arbor; Michael D.
`Warner, Oak Park; David T. Ayers,
`Birmingham, all of Mich.
`
`[73] Assignee: Kelsey-Hayes Company, Romulus,
`Mich.
`
`[21] Appl. No.: 663,638
`
`[22] Filed:
`
`Oct. 22, 1984
`
`Int. C1.4 .............................................. B60T 13/74
`[51]
`[52] US. Cl. .......................................... 303/20; 303/7;
`307/356
`[58] Field of Search ................... 303/20, 7, 93, 92, 94,
`303/95, 6 A; 188/181 R, 181 A, 181 C;
`307/519, 359, 356
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,350,142 10/1967 Schuman ................................. 303/7
`
`3,574,414 4/1971 Jacob .....
`303/20
`
`3,874,743 4/1975 Fleischer et
`303/92
`3,909,075 9/1975 Pittet ..............
`303/20
`
`4,074,194 2/1978 Wilkerson ..
`. 324/124
`
`4,084,859 4/1978 Bullet a1. ......
`303/20
`......................... 303/20
`4,295,687 10/1981 Becker et al.
`
`OTHER PUBLICATIONS
`
`'
`
`Herbert Taub and Donald Schilling, “Digital Inte-
`grated Electronics”, (New YorkchGraw—Hill Book
`Co. 1977), pp. 192—193.
`
`Primary Examiner—John W. Caldwell, Sr.
`Assistant Examiner—Alvin Oberley
`Attorney, Agent, or Firm—Ralph J. Skinkiss; Mark J.
`Sobanski
`
`[57]
`
`ABSTRACT
`
`An electric brake control circuit is responsive to an
`activation signal and a vehicle deceleration signal for
`generating a brake control signal representing a prede-
`termined amount of braking. A comparator compares
`the voltage level of the brake control signal with the
`voltage level of a sawtooth waveform to produce a
`pluse width modulated signal having a duty cycle corre-
`sponding to the predetermined amount of braking. This
`pulse width modulated signal is supplied to an output
`driver for generating a brake driving signal to energize
`the brakes. The activation signal is generated at the
`voltage level of the vehicle power supply when the
`driver actuates the vehicle stop light switch. The circuit
`is responsive to the activation signal for disabling the
`output driver when the voltage level of the activation
`signal is below a predetermined level. The circuit also
`senses the current load on the brake driving signal to
`protect the output driver in the event of a full or partial
`short circuit condition. As the sensed current load pro-
`gressively exceeds a predetermined level,
`the circuit
`progressively increases the average voltage level of the
`sawtooth waveform, thus causing the comparator to
`reduce the duty cycle of the pulse width modulated
`signal.
`
`5 Claims, 9 Drawing Figures
`
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`Curt - Exhibit 1014 - l
`
`Curt - Exhibit 1014 - 1
`
`

`

`US. Patent
`
`Jan. 26, 1988
`
`Sheet 1 0f 5
`
`4,721,344
`
`HVERAIILIC
`BRAKE
`S\STEM
`
`VEHICLE
`- BRAKE
`PEDAL
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`
`Curt - Exhibit 1014 - 2
`
`

`

`US. Patent
`
`Jan. 26, 1988
`
`Sheet 2 of 5
`
`4,721,344
`
`
`
`Curt - Exhibit 1014 - 3
`
`Curt - Exhibit 1014 - 3
`
`

`

`US. Patent
`
`Jan. 26, 1988
`
`Sheet 3 of 5
`
`4,721,344
`
`33 33
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`Curt - Exhibit 1014 - 4
`
`Curt - Exhibit 1014 - 4
`
`

`

`US. Patent
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`Curt - Exhibit 1014 - 5
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`Curt - Exhibit 1014 - 5
`
`
`
`
`
`
`

`

`US. Patent
`
`Jan. 26, 1988
`
`Sheet 5 of 5
`
`4,721,344
`
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`Curt - Exhibit 1014 - 6
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`Curt - Exhibit 1014 - 6
`
`
`

`

`4,721,344
`
`ELECTRに BRAKE CONTROLLER
`
`BACKGROUND OF THE INVENTION
`
`2
`swing to permit light to fall on the light sensing unit
`which then generates a control signal. The brake con-
`troller is responsive to the control signal for producing
`a pulsed output signal having a fixed frequency and a
`variable pulse width proportional to the level of the
`control signal.
`
`SUMMARY OF THE INVENTION
`
`The present invention relates in general to an electric
`brake controller for energizing electric可ly operated
`brakes in a towed vehicle and, in particular, to an elec-
`tric brake controller which incorporates a means for
`The present invention relates to a self-contained elec-
`sensing the deceleration of the towing vehicle and for
`tric brake controller which incorporates a unique decel-
`generating a brake energizing signal as a function of the
`eration sensing unit for generating a signal proportional
`deceleration.
`to the magnitude of deceleration of the towing vehicle.
`Recreational and utility trailers adapted to be towed
`The controller includes a circuit responsive to the de-
`by automobiles and small trucks and many similar
`celeration signal for generating a brake driving signal to
`towed vehicles are commonly provided with electric
`control the brakes of the towed vehicle.
`brakes. The electric brakes generally comprise a pair of
`brake shoes which, when actuated, frictionally engage a
`The deceleration sensing unit of the present invention
`brake drum. An electromagnet is mounted on one end
`includes a support means such as an outer housing
`of a lever coupled to actuate the brake shoes. When an
`adapted to be secured relative to the towing vehicle and
`electric current is applied to the electromagnet, the
`a pendulum mounted on an axis for pivotal movement
`electromagnet is drawn against the rotating brake drum
`relative to the housing. The pendulum is movable in one
`which pivots the lever to actuate the brakes. Typically,
`direction from a resting position to a predetermined
`the braking force produced by the brake shoes is pro-
`extended position when the vehicle is subjected to a
`portion誠 to the electric current applied to the electro-
`predetermined amount of deceleration. Means are cou-
`magnet.
`pled to the penduhun for generating a signal corre-
`To ensure proper operation, a control system for
`sponding to the predetermined extended position of the
`electrically operated brakes must be easily adjustable to
`pendulum. This signal represents the predetermined
`accommodate different relative weigh加 of the towed
`amount of deceleration to which the vehicle is sub-
`and towing vehicles. Also, the control system must be
`jected.
`predictable to give the driver of the towing vehicle a
`In accordance with the present invention, the decel-
`feeling of smooth and positive brake operation both
`eration sensing unit includes means for applying a re-
`upon applying and releasing the brakes in the towing
`storing force to the pendulum to resist further move-
`vehicle.
`ment of the pendulum in the one direction from the
`In one type of electronic brake control system, such
`extended position. It has been found that by providing
`as the system di欧】losed in U.S. Pat. No. 4,295,687, the
`such a restoring force, the outward movement of the
`electric brakes are actuated in response to the operation 35
`pendulum is limited and the pendulum can be returned
`of the towing vehicle's brake pedal by the driver. In this
`to its resting position more rapidly than if gravity pro-
`system, a transducer produces a brake control signal
`vided the sole restoring force. This stabilizes the opera-
`corresponding to the desired braking effort by sensing
`either (1) the hydra可ic pressure in the braking system
`tion of the controller and provides more accuiite brak-
`ing control. In the preferred embodiment of the inven-
`of the towing vehicle or (2) the pressure applied by a 40
`tion, the pendulum.includes a first magnet spaced from
`driver's foot to the towing vehicle's brake pedal. A
`the pivot axis of the pendulum, and the restoring force
`pulse width modulator is responsive to the brake con-
`is produced by a second magnet carried by the housing
`trol signal for generating a fixed frequency pulsed out-
`and spaced from the pendulum. This second magnet is
`put signal having a duty cycle proportional to the
`adapted to produce a magnetic field which, as the pen-
`amount of braking effort desired.
`45
`dulum swings to its extended position, opposes the mag-
`Various towed vehicle braking systems have been
`netic field produced by the first magnet and exerts a
`proposed wherein the braking of the trailer is automati-
`magnetic force on the pendulum to retard further move-
`cally controlled by the sensing of deceleration forces.
`ment of the pendulum in the one direction.
`For example, U.S. Pat. Nos. 2,242,153; 2,642,961;
`Also, the deceleration sensing unit includes damping
`2,779,443; 2,856,036; and 2,969,857 all disclose auto- 50
`means which is spaced from the magnet carried by the
`matic brake applying systems wherein the deceleration
`pendulum for reducing undesirable movement of the
`inertial force imposed upon the hitch by the trailer
`pendulum. The damping means is typically constructed
`during deceleration of a towing vehicle is sensed and
`of a ferromagnetic material which is attracted to the
`used to effect braking of the trailer.
`pendulum magnet in a direction perpendicular to the
`Also, it has been proposed to use a pendulum or a 55
`movement of the pendulum. The ferromagnetic mate-
`mass movement sensing device for sensing the decelera-
`rial dampens the movement of the pendulum such that
`tion of a towing vehicle and for operating either a me-
`chanical or an electric証 braking system in the towed
`sudden forces transmitted to the pendulum such as road
`shocks, for example, will not cause undesirable move-
`vehicle. Examples of such pendulum systems are dis-
`meat of the pendulum.
`closed in U.S. Pat. Nos. 2,870,876 and 3,053,348.
`60
`In the preferred embodiment of the invention, the
`0ne type of electronic brake controller which in-
`means coupled to the pendulum for generating a signal
`eludes a pendulum unit for sensing the deceleration of
`the towing vehicle is disclosed in U.S. Pat. No.
`corresponding to the predetermined extended position
`3,953,084. In this patent, the pendulum is provided with
`of the pendulum includes a detector such as a Hall effect
`device which is carried by the housing and is spaced
`a shield to block the passage of light from a light source 65
`to a light sensing unit when the pendulum is in a resting
`from the magnet of the pendulum. The detector is re-
`position. When the brakes of the towing vehicle are
`sponsive to the magnetic field generated by the magnet
`operated and the vehicle decelerates, the pendulum will
`for generating a position signal representing the prede-
`
`Curt - Exhibit 1014 - 7
`
`

`

`10
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`4,721,344
`
`4
`FIG. 4 is a side sectional view of the deceleration
`sensing unit taken along the line 4-4 of FIG. 3;
`FIG. 5 is a block diagram illustrating the electronic
`control circuit of the present invention;
`5 FIGS. 6a, 6b, and 6c are waveform diagrams illustrat-
`ing signals generated by the circuit of FIG. 5; and
`FIG. 7 is a schematic diagram illustrating a preferred
`embodiment of the circuit shown in FIG. 5.
`
`3
`termined extended position of the pendulum. This posi-
`don signal corresponds to the predetermined magnitude
`of deceleration of the vehicle.
`The control circuit which is responsive to the decel-
`eration signal generated by the deceleration sensing unit
`includes several unique features. Typically, the control
`circuit includes a control means responsive to an activa-
`tion signal and the deceleration signal for generating a
`brake control signal representing a predetermined
`amount of braking. A comparator means compares the
`voltage level of the brake control signal with the volt-
`Referring to the drawings, and particularly to FIG. 1,
`age level of a sawtooth waveform to produce a pulse
`there is shown a schematic diagram of an electric brake
`width modulated signal having a duty cycle corre-
`sponding to the predetermined amount of braking. This
`system 10 which utilizes an electronic brake controller
`
`pulse width modulated signal is supplied to an output 15 12 embodying the principles of the present invention.
`drive means for generating a brake driving signal to
`The brake controller 12 is generally located in the tow-
`energize the brakes.
`ing vehicle and, when activated, functions to generate
`In the circuit of the present invention, the activation
`an electric signal on a line 14 to energize electric brakes
`signal is generated when the driver either (1) steps on
`16 and 17 utilized to brake the wheels of the towed
`
`the vehicle brake pedal to close a stoplight switch or (2) 20 vehicle. The electric brakes 16 and 17 each include a
`actuates a manual control switch, either of which
`pair of brake shoes 18 and 19 which, when actuated by
`supplies the activation signal at the voltage level of the
`a lever 20, are expanded into contact with a brake drum
`vehicle power source. The circuit is provided with
`21 for braking the wheels of the towed vehicle. A sepa-
`means responsive to the activation signal for disabling
`rate electromagnet 22 is mounted on an end of each of
`
`the output drive means when the voltage level of the 25 the brake actuating levers 20. Each electromagnet 22 is
`activation signal is below a predetermined level. This
`positioned to abut the generally flat side of a brake drum
`21. As an electric current is passed t址ough each of the
`prevents the electric brake controller from generating a
`brake driving output signal in instances wherein, due to
`electromagnets 22, the electromagnets are drawn into
`circuit problems such as an insufficient ground in the
`contact with the brake drums 21 and the resulting drag
`
`stop light circuit, the control means receives a lower 30 pivots the levers 20 to engage the brakes 16 and 17 in a
`level activation signal when neither the stop light
`conventional manner.
`switch or the manual control has been actuated.
`The towing vehicle typically includes a conventional
`Also, the present invention includes means for sens-
`hydraulic brake system 24 which is activated when a
`ing the current load on the brake driving signal to pro-
`brake pedal 25 is depressed by the driver. The brake
`tect the output drive means in the event of a full or
`35 pedal 25 is coupled to a stop light switch 26 such that,
`partial short circuit condition. Such sensing means are
`when the brake pedal 25 is depressed, the switch 26 is
`responsive to a sensed current load progressively ex-
`closed and power from a vehicle power supply 27 is
`ceeding a predetermined level for progressively in-
`applied to one or more brake, lights 28. The vehicle
`creasing the average voltage level of the sawtooth
`power supply 27 is also connected to provide power to
`waveform, thus causing the comparator means to re-
`40 the controller 12 on a line 27a. When the stop light
`duce the duty cycle of the pulse width modulated sig-
`switch 26 is closed, power is supplied on a line 29 as an
`nal. Thus, in the event of a parti司 short circuit condi-
`activation signal to activate the controller 12.
`tion, limited braking is maintained.
`When the stop light switch 26 is closed and the con-
`In the present invention, a foot actuated means such
`troller 12 is activated, the controller 12 functions to
`
`as a brake pedal stop light switch can be utilized to 45 generate an electric output signal on the line 14 having
`generate a first brake control signal representing a first
`a current which is directly proportional to the braking
`desired amount of braking, while a hand actuated means
`force applied to the towing vehicle. In order to generate
`such as a manual control can be used to generate a
`such a signal, the controller 12 incorporates a unique
`second brake control signal representing a second de-
`means for sensing the deceleration of the towing vehicle
`sired amount of braking. With the present invention,
`50 and for generating a signal which is a function of the
`means are responsive to the first and second brake con-
`deceleration of the vehicle. Such a deceleration sensing
`trol signals for generating a composite brake control
`unit is generally indicated in FIG. 1 by reference nu-
`signal representing the combined braking of the first
`meral 30. As shown in FIG. 1, the deceleration sensing
`and second braking control signals.
`unit 30 is located within an outer casing 31 of the elec-
`55 tronic controller 12. As will be discussed in more detail
`BRIEF DESCRIPTION OF THE DRAWINGS
`hereinafter, the deceleration sensing unit 30 includes a
`The above, as well as other advantages of the present
`pendulum adapted to swing in one direction when the
`invention, will become readily apparent to one skilled in
`towing vehicle is decelerating, and means for generat-
`the art from reading the following detailed description
`ing a signal representing the amount of swinging move-
`in conjunction with the attached drawings, in which:
`60 ment of the pendulum. Also, the deceleration sensing
`FIG. 1 is a schematic diagram illustrating an electric
`unit includes a leveling means 33 which, as will be dis-
`braking system utilizing an electric brake controller
`cussed, extends from the side wall of the casing 31 and
`according to the present invention;
`is utilized to level the sensing unit 30 after the casing 31
`FIG. 2 is an enlarged perspective view illustrating a
`has been securely mounted to the vehicle.
`deceleration sensing unit incorporated in the brake con-
`65
`In some instances, it may be desirable to only actuate
`troller of FIG. 1;
`the brakes 16 and 17 in the towed vehicle. This may be
`FIG. 3 is a sectional view of the deceleration sensing
`desirable, for example, to stabilize the towed vehicle
`unit taken along the line 3-3 of FIG. 2;
`against vacillations or swinging caused by strong side
`
`Curt - Exhibit 1014 - 8
`
`

`

`4,721,344
`
`6
`5
`provides the necessary damping in the movement of the
`winds. Therefore, a manual slide control 34 is provided
`on the electro或c controller 12 to allow the vehicle
`pendulum such that the road shocks transmitted to the
`driver to manually apply the towed vehicle br水es 16
`pendulum 44 will not cause undesirable movement of
`the pendulum. Also, it has been found that the metal
`and 17 without applying the towing vehicle brakes.
`The electronic controller 12 可so is provided with a 5
`channel 50 shields the magnet 48 from external influenc-
`manu司 gain control 36. The g誠n control 36 allows the
`ing or demagnetization forces.
`The movement of the lower end of the pendulum
`vehicle driver to compensate for different loads in the
`relative to a norm証 vertical resting position is sensed by
`towed vehicle. For example, as the load in the towed
`a detector means such as a Hall Effect device 52 spaced
`vehicle increases, it is necessary to increase the braking
`
`force in the towed vehicle relative to the braking force 10 from and positioned adjacent one end 48a of the pendu-
`lum magnet 48. The Hall Effect device 52 is supported
`applied in the towing vehicle. By adjusting the gain
`control 36, the power applied by the electronic control-
`adjacent the magnet 48 within a square shaped opening
`1cr 12 to the electromagnets 22 may be increased or
`54a formed in a plastic carrier 54 seated within the
`decreased for any given output from the deceleration
`metal channel 50. As the pendulum swings from the
`sensing unit 30.
`resting position P, the Hall Effect device 52 is adapted
`The electronic brake controller 12 includes an indica-
`to generate a voltage proportional to the amount of
`movement of the pendulum 44.
`tor light 38. The intensity of the light 38 is proportional
`In accordance with the present invention, the decel-
`to the average current level of the signal generated on
`the line 14 used to actuate the towed vehicle brakes 16
`eration sensing unit 30 includes means for providing a
`
`and 17. The light 38 provides a visual indication to the 20 restoring force to the pendulum such that the pendulum
`driver to show that the controller 12 is operating prop-
`can be returned to its resting position more rapidly than
`if gravity provided the sole restoring force. While it will
`erly.
`Referring to FIGS. 2 t址ough 4, there are shown
`be appreciated that various types of spring biasing
`enlarged drawings illustrating a preferred embodiment
`means could be utilized to provide this function, it has
`been discovered that a separate magnet positioned in
`of the deceleration sensing unit 30 of the present inven- 25
`tion. The deceleration sensing unit 30 comprises an
`spaced apart relationship to the lower end of the pendu-
`outer plastic housing 42 which is secured to a circuit
`lum 44 can be utilized to provide a restoring force
`which increases in magnitude as the pendulum swings
`board 43 supported within the controller casing 31. A
`further from its resting position. As shown in FIG. 4, a
`pendulum 44 is supported for swinging movement rela-
`
`tive to the housing 42 by means of a pivot pm 46. As 30 restoring magnet 56 is positioned near one end of the
`upper surface of the lower arcuate wall 50a of metal
`shown in FIG. 3, the pivot pin 46 extends through aper-
`tures 42a and 42.5 formed in the side walls of the housing
`channel 50 and is supported thereon by a pair of spaced
`42 and through spaced-apart low friction bearing ele-
`apart inverted U-shaped clips 54.5 provided in the plas-
`men加 44a and 44b provided in the upper end of the
`tic carrier 54. As the pendulum swings forwardly, the
`pend可um. If desired, a lubricant can be introduced 35
`magnetic field of restoring magnet 56 will oppose the
`between the bearing elements 蝋l and 44.5 and the pin
`magnetic field of pendulum magnet 48 and a restoring
`46. The one end of the pin 46 is provided with a head
`force Fr will oppose further forward movement of the
`portion 46a received by the leveling means 33, while the
`pendulum in the direction D from the extended position
`Pe. It has been found that providing such a restoring
`opposite end 46.5 is secured by a retaining clip 47. The
`
`lower end of the pendulum is provided with a down- 40 force to the pendulum of the deceleration sensing unit
`wardly facing C -shaped clamp 44c (shown in FIG. 4)
`enhances the operator's controllability of the combined
`bra虹ng system.
`for receiving and frictionally engaging a cylindrical
`magnet 48. As will be di割】ussed, the magnet 48 func-
`In addition to supporting the Hall Effect device 52
`tions both as a weight and as a means for indicating the
`and the restoring magnet 56, the plastic carrier 54 is also
`45
`position of the lower end of the pendulum.
`provided with an upwardly projecting stop means 54c
`Normally, as shown in FIG. 4, when the vehicle is
`(shown in FIG. 4) to limit the rearward swinging move-
`traveling in a direction T and is not subjected to any
`ment of the pendulum in the direction R. The stop
`deceleration or acceleration forces, the pendulum will
`means 54c is positioned a predetermined distance S from
`be located in a resting position Pr. As the towing vehicle
`the center of the Hall Effect device 52 and, as will be
`brakes are applied and the towing vehicle is deceler- 50
`discussed, prevents the user from adjusting the pendu-
`ated, the pendulum will swing outwardly in a forward
`lum in a reverse direction.
`direction D to a predetermined extended position Pe, as
`In order to achieve proper operation, it is necessary
`determined by the magnitude of decelerati6n of the
`that the resting position of the pendulum relative to the
`towing vehicle.
`center of the Hall Effect device 52 be adjusted after the
`In order to reduce undesirable movement of the pen- 55
`controller casing 31 has been securely mounted in the
`dulum 44 when the sensing unit 30 is subjected to sud-
`towing vehicle. The controller can be mounted under
`den forces other than deceleration such as road shock,
`the vehicle dashboard, for example. This adjustment
`for example, it is desirable to dampen the movement of
`can be accomplished by leveling means 33. The leveling
`the pendulum 44. It has been 拓und th誠5飢Is魚ctory
`means 33 includes a sleeve member 33a for receiving
`damping can be achieved by locating a ferromagnetic 加
`the pivot pin 4.6. An inner lever arm 33.5 extends radially
`element such as a metal channel 50 in spaced apart
`from the sleeve member 33a and has an outer end pro-
`relationship with pendulum magnet 48. The metal chan-
`vided with an axially extending pin 33c which projects
`nd 50 includes an arcuate lower wall 50a connected to
`into an aperture SOd formed in the side wall 50b of the
`a pair of spaced apart triangular shaped side walls 50b
`metal channel 50. The outer end of the sleeve member
`and 50c having apertures formed in the upper ends 65
`33a, which is adapted to extend outwardly from the
`therefore for receiving the pivot pm 46. It has been
`casing 31, is provided with an outer lever arm 33d.
`found that the magnetic attraction between the pendu-
`In order to adjust the position of the Hall Effect
`lum magnet 48 and the surrounding metal channel 50
`device 52 relative to the pendulum 44, the lever arm 33d
`
`Curt - Exhibit 1014 - 9
`
`

`

`4,721,344
`
`8
`7
`ated that other types of deceleration sensing units could
`is pivoted about the pivot pin 46, thus causing the inner
`lever 33b and the pin 33c to pivot the met可 channel 50
`also be utilized with the circuit of the present invention.
`and the Hall Effect device 52. Typic証ly, the retaining
`Also, the brake input signal generating means 80 can be
`a transducer (not shown) coupled to the hydraulic sys-
`clip 47 is pressed sufficiently on the pin end 46b to cause
`the leveling means 33 and the metal channel 50 to be 5
`tern of the towing vehicle for generating a signal pro-
`friction誠ly held relative to the plastic housing 42 about
`portional to the hydraulic pressure in the towing vehi-
`cle braking system, or a pressure transducer which is
`the pin 46, thus maintaining the adjusted position of the
`coupled to sense the pressure applied to the vehicle
`leveling means 33. The above adjustment is relatively
`brake pedal by the driver. Such transducers are dis-
`simple, and consists of merely having the operator acti-
`closed in U.S. Pat. No. 4,295,687, which is herein incor-
`vate the controller on level ground by depressing the 10
`porated by reference.
`vehicle brake pedal, and then pivoting the outer lever
`arm 33d in a direction which causes relative movement
`The input circuit 74 also receives signals from the
`of the pendulum in the direction D until the indicator
`manual control 34 and the gain adjustment 36, whose
`functions have previously been discussed with refer-
`light 38 just begins to light. If the operator were to
`ence to FIG. 1. However, it should be noted that, in the
`accidently pivot the lever arm 33d in an opposite direc- 15
`circuit of the present invention, the voltage level of the
`tion such that pendulum moves toward the stop means
`5恥, the stop means 54c prevents movement of the pen-
`brake control signal on the line 72 represents the combi-
`nation of the signals received from the brake control
`dulum to a point which causes the indicator light 38 to
`signal generating means 80 and the manual control 34.
`turn on. Thus, the operator is prevented from adjusting
`20
`the unit in the reverse direction.
`Thus, when the input circuit is generating a brake con-
`In addition to adjusting the resting position of the
`trol signal on the line 72 at a predetermined level in
`pendulum 44 relative to the center of the Hall Effect
`response to a brake input signal received on the line 78
`device 52, another important adjustment is the spacing
`from the brake input signal generating means, actuation
`between the end wall 4&2 of the pendulum magnet 48
`of the manual control 34 will increase the level of the
`and the facing surface 5ユl of the Hall Effect device 52, 25
`brake control signal. In prior art systems, the brake
`as represented by dimension G in FIG. 3. Not only is
`control signal on the line 72 corresponded to the higher
`the initial adjustment of the spacing G important, it is
`of the two signals supplied to the input circuit, and did
`also important that this spacing be maintained during
`not represent a combination of the two.
`The PWM circuit 70 includes a sawtooth oscillator 80
`the swinging movement of the pendulum. To ensure
`that such spacing is maintained, the pendulum magnet is 30
`which functions to generate a triangular shaped wave-
`axially positioned in the C-shaped clamp 44c such that
`form on a line 82 as one input to a comparator 84. A
`the distance between the one end 48a and the side wall
`second input of the comparator 84 is connected to re-
`5叱 of the channel 50 is slightly less than the distance
`ceive the brake control signal on the line 72. When the
`between the opposite end 48b and the side wall SOb.
`level of the brake control signal on the line 72 is greater
`Thus, the magnetic attraction between the magnet 48 35
`than the level of the triangular waveform on the line 82,
`and the side wall SOc is slightly greater than the mag-
`the comparator 84 will generate a high level output
`netic attraction between the magnet 48 and the side wall
`signal such that a square wave signal will appear on the
`50b. This causes the pendulum to be biased toward the
`line 76. The duty cycle of the square wave PWM signal
`side wall 50c such that the outer end of the bearing
`on the line 76 is directly proportional to the level of the
`
`element 44b always remains in contact with the inner 40 brake control signal on the line 72.
`surface of the side wall 50c, while the outer end of the
`When the vehicle brake pedal 25 is depressed, the
`bearing element 44a is spaced from the inner surface of
`stop light switch 26 supplies a power signal to a regu-
`the side wall 50b.
`lated power source 86 which generates a regulated
`It should be noted that, while the deceleration sensing
`voltage on a line 88 to activate the input circuit 74 and
`unit of the preferred embodiment includes a pendulum 45
`the PWM circuit 70. When the input circuit 74 and the
`mounted for pivotal movement about a generally hori-
`PWM circuit 70 are activated, the PWM circuit 70 will
`zontal axis, it will be appreciated that the deceleration
`generate a PWM output signal on the line 76.
`sensing unit can utilize other types of mass movement
`Under normal operating conditions, the PWM output
`sensing elements w班ch, if desired, can be pivotally
`signal on the line 76 is supplied to the base of a transistor
`mounted about a vertical axis.
`
`50 90 having a collector coupled to supply the PWM out-
`The circuit utilized to generate the electric brake
`put signal as an input to a current amplifier 92. How-
`control signal is shown in block diagram form in FIG. 5
`ever, before the output of the PWM circuit can be sup-
`and includes several unique features. Basically, the cir-
`plied to the current amplifier 92 through the transistor
`cuit utilizes a pulse width modulating (PWM) circuit 70
`90, a second transistor 94, having a collector connected
`which receives a brake control signal representing the 55
`to the emitter of the transistor 90 and an emitter con-
`desired braking on a line 72 from an input circuit 74, and
`nected to the circuit ground potential, must receive an
`generates a square wave pulse train on a line 76 having
`enabling signal on a line 96 from the regulated power
`a duty cycle directly proportional to the level of the
`source 86. In accordance with the present invention, the
`brake control signal on the line 72. The modulated pulse
`enabling signal is only supplied to the transistor 94
`train on the line 76 is then amplified to produce a brake 60
`when the voltage level supplied to the regulated power
`driving signal on the line 14 to actuate the electric
`source 86 on the line 29 exceeds a predetermined level.
`brakes.
`Thus, in instances wherein, due to certain vehicle cir-
`The input circuit 74 receives a signal on a line 78 from
`cuit problems, the stop light switch is not actuated and
`a brake input signal generating means 80. The brake
`a lower level voltage signal may be inadvertently sup-
`input signal generating means 80 can be a deceleration 65
`pl