_
`
`.
`
`United States Patent [19]
`Hosseini et a1.
`
`llllllllllllllllllllllIllllllllllllllllllllllllllllllllllllllllllllllllllll
`[11] Patent Number:
`5,189,940
`[45] Date of Patent:
`Mar. 2, 1993
`
`US00518994OA
`
`[54] METHOD AND APPARATUS FOR
`CONTROLLING AN IMPLEMENT
`
`4,166,506 9/1979 Tczuka et al. ...................... .. 91/453
`4,358,989 11/1982 Tordenmalm
`91/361
`4,552,503 11/1985 Mouri et al. ..
`. 414/687
`4,844,685 7/1989 Sagaser ............................. .. 414/700
`[75] Inventors: Javgd giosseini; Eric A. Hutchison,
`_
`_
`bot 0 Peoria; Randall M. Mitchell,
`Pmrm'y Examliler_Edward. K‘ Look
`Washington; Weldon L. Phelps,
`Assistant Examiner-F. Damel Lopez
`Dunlap; James E Schimpf,
`Attorney, Agent, or Firm-Steven R. Janda
`plain?eld, an of In‘
`[57]
`ABSTRACT
`[73] Assignee: Caterpillar Inc., Peoria, 111.
`Vehicles having implements are typically used to per
`[211 App, No _ 759 390
`form repetitive functions in work cycles. An implement
`.
`'
`"
`’
`control system raises and lowers an implement relative
`[22] P116611
`Sep- 13, 1991
`“’ the vehicle and MW“ the stresses atPPm’d 1° the
`[51] Int. Cl.5 ............................................ .. F15B 13/16
`vehicle from abruptly stopping the motion of the imple
`........ " 91/361; 91/367;
`[52] US. Cl.
`ment. A lever pilot signal is produced in response to the
`91/403; 91/435; 91/461
`Pivotal Position of a control lever- An electmhydmulic
`[58] Field of Search ............... .. 91/361, 367, 403, 43s,
`91 /45 3’ 461; 60/469 _ pilot signal is also produced. The pilot signal having the
`greater pressure is directed to a main valve for control
`ling the position of the implement. The method and
`apparatus of the instant invention are applicable to a
`“umber °f vehicles having a hydraulically °Pemed
`
`[56]
`
`References Cited
`US. PATENT DOCUMENTS
`3789 739 2/1974 Krehbiel etal. .................... .. 91/461
`
`. . . .. 91/527
`3,892,079 7/1975 Hirano et al. . . . . . . . .
`.. 214/138 R
`4,015,729 4/1977 Parquet et a1.
`4,l09,8l2 8/1978 Adams et al. ..................... .. 214/762
`
`lImplement‘
`
`25 Claims, 4 Drawing Sheets,
`
`MAX LIFT ARM HEIGHT
`
`UFT KICKOUT HEIGHT
`LIFT KICKOUT BEGIN
`MODULATION
`
`LIFT ARM
`
`rowan KICKOUT seam
`uonuumou
`LOWER KICKOUT HEIGHT
`
`MINIMUM LOWER POSITION
`
`56
`KICKOUT
`r5‘ssrswrrcn
`
`Page 1 of 13
`
`CATERPILLAR EXHIBIT 1108
`
`

`

`US. Patent
`
`Mar. 2, 1993
`
`Sheet 1 of 4
`
`5,189,940
`
`MAX LIFT AFIM HEIGHT
`
`LIFT KICKOUT HEIGHT
`LIFT KICKOUT BEGIN
`MODULATION
`
`LIFT ARM
`
`LOWER KICKOUT BEGIN
`MODULATION
`LOWER KICKOUT HEIGHT
`
`MINIMUM LOWER POSITION
`
`Page 2 of 13
`
`

`

`U.S. Patent
`
`Mar. 2, 1993
`
`Sheet 2 of 4
`
`5,189,940
`
`mm
`
`ZOE mm
`
`wmomzmm zoEmom
`‘
`wmomzwm
`
`@T\ I
`
`EMIIOEZOQ
`
`5.56;‘
`
`202.50.‘
`
`COmZmm
`
`Page 3 of 13
`
`

`

`US. Patent -
`
`Mar. 2, 1993
`
`Sheet 3 of 4
`
`5,189,940
`
`* READ CONTROL LEVER POSITION ~
`
`60
`
`IN DETENT?
`
`NO
`___'__/
`YES
`I,
`r 65
`CALCULATE LIFT ARM
`VELOCITY AND K1
`
`'
`
`F 62,
`I
`v
`CALCULATE DIFFERENCE SIGNAL
`
`64
`II
`DIFFERENCE \ YES
`SIGNAL > K1? /
`NO
`f- 66
`v
`RELEASE LEVER FROM DETENT
`
`f 68
`‘I
`CALCULATE ELECTROHYDRAULIC
`PILOT VALVE CURRENT
`
`I
`
`[70
`
`CALCULATE NEW
`DIFFERENCE SIGNAL
`
`IcLosE ELECTROHYDRAULIC
`PILOT VALVE
`
`I 1g_'-|_
`
`Page 4 of 13
`
`

`

`US. Patent
`
`Mar. 2, 1993
`
`Sheet 4 of 4 "
`
`5,189,940
`
`READ CONTROL LEVER POSITION ‘—-'-—-———'
`
`(-76
`
`;
`
`‘
`
`1a
`
`IMPLEMENT \"0
`LOWERING? /
`YES
`f‘ 80
`‘
`READ CONTROL LEVER POSITION
`
`f- 82
`v
`CALCULATE LEVER
`VELOCITY
`
`NO
`
`II
`
`84
`LEVER VELOCITY
`SIGNAL > K3?
`YES
`
`/— as
`MODULATE ELECTROHYDRAULIC
`PILOT VALVE AT PRESPECIFIED
`RATE
`.
`
`Page 5 of 13
`
`

`

`1
`
`\
`METHOD AND APPARATUS FOR CONTROLLING
`AN IMPLEMENT
`
`DESCRIPTION
`1. Technical Field
`This invention relates generally to an apparatus for
`controlling the extension and retraction of a hydraulic
`cylinder, and more particularly to an apparatus for
`reducing the speed at which a hydraulic cylinder is
`extending or retracting.
`2. Background Art
`Vehicles such as wheel type loaders include work
`implements capable of being moved through a number
`of positions during a work cycle. Such implements
`typically include buckets, forks, and other material
`handling apparatus. The typical work cycle associated
`with a bucket includes positioning the bucket and asso
`ciated lift arm in a digging position for ?lling the bucket
`with material, a carrying position, a raised position, and
`a dumping position for removing material from the
`
`25
`
`5,189,940
`2
`and reduce operator comfort. In some situations, the
`rear of the tractor can even be raised off the ground.
`To reduce these stresses, systems have been, devel
`oped to more slowly and smoothly stop the motion of
`the implement in these situations. One solution to this
`problem is disclosed in US. Pat. No. 4,109,812, issued
`to Adams et al. on Aug. 29, 1978. A device is provided
`for halting the ?ow of hydraulic ?uid to the cylinders
`just prior to the lift arms reaching the end of their range
`of motion and trapping ?uid within the cylinder to act
`as a hydraulic cushion. While this approach is accept
`able for slowing the implement before it reaches a me
`chanical stop, this device is not readily adapted to use
`with a control system that stops the implement at ad
`justable kickout positions. Such kickout positions are
`chosen in response to the parameters of the work cycle
`and are typically different from the maximum raise and
`lower positions. Furthermore, this system is unable to
`sense conditions in which the operator moves the con
`trol lever too quickly to allow the hydraulic system to
`operate smoothly. The effects of quick movement of the
`control lever are particularly pronounced when the
`vehicle is lowering a heavy load. Such a hydraulic
`cushion is also not readily controllable in response to
`changes in operating conditions.
`An alternative system is disclosed in US. Pat. No.
`4,358,989, issued to Tordenmalm on Nov. 16, 1982. This
`system utilizes an electrohydraulic valve to extend and
`retract a piston within a hydraulic cylinder. When the
`piston reaches a position that is a predetermined dis
`tance from the end of stroke, the control system pro
`gressively closes the electrohydraulic valve as the pis
`ton continues to move toward‘ the end of stroke. While
`this system adequately reduces the velocity of the pis
`ton before it reaches a hard stop, it is not operable to
`perform other desirable implement functions, such as
`adjusting kickout positions, de?ning multiple raise kick
`out positions, and performing ?oat operations in which
`?uid from the rod end of the hydraulic circuit is al
`lowed to ?ow to the hydraulic tank. Also, if the elec
`tronic system fails, the operator is unable to operate the
`hydraulic cylinders.
`The present invention is directed to overcoming one
`or more of the problems set forth above.
`‘
`
`40
`
`bucket.
`_
`Control levers are mounted at the operator’s station
`and are connected to a hydraulic circuit for moving the
`bucket and/or lift arms. The operator must manually
`move the control levers to open and close hydraulic
`valves that direct pressurized fluid to hydraulic cylin
`ders which in turn cause the implement to move. For
`example, when the lift arms are to be raised, the opera
`tor moves the control lever associated with the lift arm
`hydraulic circuit to a position at which a hydraulic
`valve causes pressurized ?uid to ?ow to the head end of
`a lift cylinder thus causing the lift arms to rise. When
`the control lever returns to a neutral position, the hy
`35
`draulic valve closes and pressurized ?uid no longer
`flows to the lift cylinder.
`In normal operation, the implement is often brought
`to an abrupt stop after performing a given work cycle
`function This can occur,‘ for example, when the imple
`ment is moved to the end of its range of motion. If the
`lift arms or hydraulic cylinders impact with a mechani
`cal stop, signi?cant forces are absorbed by the lift arm
`assembly and the hydraulic circuit. This results in in
`creased maintenance and accelerated failure of associ
`ated parts.
`A similar situation occurs when a control system
`holds the control lever in a detent position at which the '
`associated hydraulic valve is held open until the lift arm
`assembly or implement reaches a predetermined posi
`50
`tion. The control system then releases the control lever
`which is spring biased toward the neutral position. The
`springs quickly move the control lever to the neutral
`position which in turn abruptly closes the associated
`hydraulic valve. Thus, the lift arm assembly and/or
`bucket is brought to an abrupt stop. Such abrupt stops
`result in stresses being exerted on the hydraulic cylin
`ders and implement linkage from the inertia of the
`bucket, lift arm assembly, and load. The abrupt stops
`also reduce operator comfort and increase operator
`fatigue.
`Stresses are also produced when the vehicle is lower
`ing a load and the operator quickly closes the associated
`hydraulic valve. The inertia of the load and implement
`exerts forces on the lift arm assembly and hydraulic
`system when the associated hydraulic valve is quickly
`closed and the motion of the lift arms is abruptly
`stopped. Such stops cause increased wear on the vehicle
`
`45
`
`55
`
`Disclosure of the Invention
`The invention avoids the disadvantages of known
`implement controls and provides a system for controlla
`bly reducing the speed of a hydraulically operated work
`implement. The instant invention combines the advan
`tages of hydraulic and electrohydraulic implement con
`trols to provide a reliable and ?exible implement con
`trol system.
`In one aspect of the present invention, an apparatus
`for controllably raising and lowering an implement
`relative to a work vehicle is provided. The implement is
`pivotally connected to the work vehicle and is movable
`to and between maximum raised and lowered positions
`in response to the extension and retraction of a hydrau
`lic cylinder. A lever operated hydraulic valve produces
`a lever pilot signal having a ?rst pressure in response to
`the position of a control lever. An electrohydraulic
`valve produces an electrohydraulic pilot signal having a
`second pressure. One of the ?rst and second pressures is
`selected and the hydraulic cylinder is controlled in
`response to the selected pressure.
`In another aspect of the present invention, a method
`for controllably raising and lowering an implement
`
`Page 6 of 13
`
`

`

`5,189,940
`4
`3
`disposed within the hydraulic cylinders or any other
`relative to a work vehicle is provided. The implement is
`device capable of measuring, either directly or indi
`pivotally connected to the work vehicle and is movable
`rectly, the relative extension of a hydraulic cylinder.
`to and between maximum raised and lowered positions
`FIG. 2 diagrammatically illustrates the range of mo
`in response to the extension and retraction of a hydrau
`tion of the lift arm assembly 14 and a plurality of inter
`lic cylinder. A control lever is pivotally movable to and
`mediate positions through which the lift arm assembly
`between a neutral position, a predetermined raise detent
`14 is moved during a work cycle. The maximum lift arm
`position, and a predetermined lower detent position.
`height is the position of the lift arm assembly 14 at
`The method comprises the steps of producing a lever
`which a mechanical stop prevents the lift cylinders 18
`pilot signal in} response to the pivotal location of the
`from further raising the bucket 16. Similarly, the mini~
`control lever, producing an electrohydraulic pilot sig
`nal, selecting the pilot signal having the greater‘ pres
`mum lower position is the position of the lift arm assem
`bly 14 at which a mechanical stop prevents the lift cyl-'
`sure, and controlling the position of the implement in
`inders 18 from further lowering the bucket 16. A mid
`response to the selected pilot signal.
`point is shown generally by the dashed line in FIG. 2
`The invention also includes other features and advan
`and substantially bisects the range of motion of the lift
`tages which will become apparent from a more detailed
`study of the drawings and speci?cation.
`arm assembly 14 which is de?ned by the maximum lift
`arm height and the minimum lower position.
`BRIEF DESCRIPTION OF THE DRAWINGS
`The lift and lower kickout heights illustrate positions
`to which the lift arm assembly 14 is to be moved while
`For a better understanding of the present invention,
`performing a work cycle. For example, the lift kickout
`reference may be made to the accompanying drawing
`height corresponds to the desired dump height for the
`in which:
`-
`bucket 16, and the lower kickout height corresponds to
`FIG. 1 is a side view of the forward portion of a
`the return-to-dig position for the bucket 16. Advanta
`loader vehicle;
`geously, the lift and lower kickout heights are selected
`FIG. 2 illustrates a plurality of positions through
`by the operator at the beginning of a work cycle and are
`which the vlift arms of a work vehicle are moved;
`changeable in response to the parameters of the particu
`FIG. 3 is a diagrammatic illustration of an embodi
`lar work cycle being performed.
`ment of the invention;
`_
`The lift and lower kickout begin-modulation-posi
`FIG. 4 is a generalized flow chart of the operation of
`tions correspond to the positions of the lift arm assem
`a portion of an embodiment of the invention; and
`bly 14 at which the implement control system begins to
`FIG. 5 is a generalized flow chart of the operation of
`reduce the speed at which the bucket is being moved
`a portion of an embodiment of the invention.
`toward the associated kickout position. The begin
`modulation-positions are advantageously selected to
`allow the implement control system to completely stop
`the bucket at the appropriate kickout height without
`unduly stressing the lift arm assembly 14 or reducing
`- operator comfort.
`Referring now to FIG. 3, an embodiment of the im
`plement control system is diagrammatically illustrated.
`A control lever 24 is spring biased toward a neutral
`position and is connected to a detentmechanism 26
`which is actuatable to hold the control lever 24 in pre
`determined raise and lower detent positions in response
`to the control lever being moved beyond these detent
`positions. Since the velocity of the implement is a func
`tion of control lever position, the raise and lower detent
`positions are chosen in response to design preferences
`regarding the desired velocity of the implement while
`the work cycle is being performed. The detent mecha
`nism 26_includes solenoids (not shown) for controllably
`releasing the control lever 24 from the raise and lower
`detent positions in response to receiving a kickout signal
`from a controller 30. Typically, the kickout signal is
`produced in response to the lift arm assembly being
`moved to the kickout begin-modulation-position.
`The control lever 24 is connected to a lever operated
`pilot valve 28 which produces a lever pilot signal in
`response to the control lever 24 being in a position
`substantially different from the neutral position. Since
`the control lever 24 is generally movable in two direc
`tions, the lever operated pilot valve 28 directs the lever
`pilot signal to the raise pilot line 32 in response to the
`control lever 24 being moved in one of the directions,
`and directs the lever pilot signal to the lower pilot line
`34 in response to the control lever being moved in the
`other direction.
`A control lever position sensor 36 is connected to and
`between the control lever 24 and the controller 30. The
`
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`In FIG. 1 an implement control system is generally
`represented by the element number 10. Although FIG.
`1 shows a forward portion of a wheel type loader vehi
`cle 12 having a payload carrier in the form of a bucket
`16, the present invention is equally applicable to vehi
`cles such as track type loaders, hydraulic excavators,
`and other vehicles having similar loading implements.
`The bucket 16 is connected to a lift arm assembly 14,
`which is pivotally actuated by two hydraulic lift cylin
`ders 18 (only one of which is shown) about a pair of lift
`arm pivot pins 13 (only one shown) attached to the
`vehicle frame. A pair of lift arm load bearing pivot pins
`19 (only one shown) are attached to the lift arm assem
`bly 14 and the lift cylinders 18‘. The bucket 16 can also
`be tilted by a bucket tilt cylinder 20. A lift cylinder
`extension sensor 22 is included in connection with the
`lift cylinders 18 and a tilt cylinder extension sensor 23 is
`included in connection with the tilt cylinder 20.
`In the preferred embodiment, the lift and tilt cylinder
`extension sensors 22,23 are rotary potentiometers con
`nected to and between the lift arm pivot pins 13 and the
`lift arm assembly 14. The rotary potentiometers pro
`duce pulse width modulated signals in response to the
`angular position of the lift arms with respect to the
`vehicle and the bucket 16 with respect to the lift arm
`assembly 14. Since the angular position of the lift arms
`is a function of lift cylinder extension, the signal pro
`duced by the rotary potentiometer in the lift cylinder
`extension sensor is a function of lift cylinder extension.
`Similarly, since the angular position of the bucket 16 is
`a function of tilt cylinder extension, the signal produced
`the rotary potentiometer in the tilt cylinder extension
`sensor 23 is a function of tilt cylinder extension. Other
`embodiments may use a radio frequency (RF) sensor
`
`55
`
`65
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`Page 7 of 13
`
`

`

`15
`
`25
`
`35
`
`20
`
`5,189,940
`5
`6
`control lever position sensor 36 preferably includes a
`pilot signals to the raise and lower ports 50,52, the lift
`rotary potentiometer which produces a pulse width
`cylinders 18 are controllably extended and retracted in
`modulated lever position signal in response to the piv~
`response to the pilot signals being directed to the main
`valve 48 by the resolvers 44,46.
`otal position of the control lever 24; however, any sen
`sor that is capable of producing an electrical signal in
`The main valve 48 is also connected to a ?uid reser
`response to the pivotal position of the control lever
`voir (not shown). In the preferred embodiment, the
`main valve 48 performs a ?oat operation by connecting
`would be operable with the instant invention. '
`An electrohydraulic pilot supply valve 38 is con
`the hydraulic circuits associated with both the rod end
`nected to and between the controller 30, a hydraulic
`and head end of the hydraulic cylinder 18 to the fluid
`pump (not shown), and raise and lower electrohydrau
`reservoir in response to receiving a ?oat pressure signal
`lic pilot valves 40,42. The pilot supply valve 38 is in
`from the electrohydraulic pilot valves 40,42. When the
`?oat operation is performed, the implement is lowered
`cluded to control the ?ow of pressurized ?uid to the
`electrohydraulic pilot valves 40,42 and is controllably
`in response to the force of gravity rather than in re
`opened and closed in response to signals from the con
`sponse to pressurized ?uid being applied to the rod end
`troller 30. The pilot supply valve 38 is preferably a
`of the hydraulic cylinder 18.
`.
`normally closed on/off pilot valve. The controller 30
`A kickout set switch 54 is included in connection
`generally maintains the pilot supply valve 38 in an “on”
`with the controller 30 to allow the operator to select the
`state in which pressurized ?uid is directed to the elec
`desired kickout heights described above. The kickout
`trohydraulic pilot valves 40,42. In response to prese
`set switch 54 typically includes a push button 56 which
`lected fault conditions, the controller 30 closes the pilot
`is preferably mounted to the vehicle 12 at the operator’s
`supply valve 38 and prevents the pressurized ?uid from
`station. When the operator actuates the push button 56,
`reaching the electrohydraulic pilot valves 40,42.
`the controller 30 reads the lift cylinder extension signal
`The electrohydraulic pilot valves 40,42 are prefera
`from the lift cylinder extension sensor 22 and preferably
`bly normally closed, three-way, proportional pilot pres
`compares the magnitude of the cylinder extension signal
`to a predetermined magnitude corresponding to the
`sure control valves and are connected to the raise and
`lower pilot lines 32,34 via respective raise and lower
`midpoint illustrated in FIG. 2. If the lift cylinder exten
`hydraulic resolvers 44,46. The electrohydraulic pilot
`sion signal is greater than the predetermined magnitude,
`valves 40,42 controllably open and close in response to
`the lift cylinder extension signal is stored in a non~
`the magnitude of current ?owing from the controller 30
`volatile memory in the controller 30 at an upper kickout
`to each of the electrohydraulic pilot valves 40,42. The
`address (not shown). If the lift cylinder extension signal
`electrohydraulic pilot valves 40,42 are continuously
`is less than the predetermined magnitude, the lift cylin
`variable between fully opened and fully closed positions
`der extension signal is stored in the non-volatile mem
`at which the resulting electrohydraulic pilot signal di
`ory at a lower kickout address (not shown), and the
`rected toward the resolvers 44,46 varies respectively
`controller 30 reads the tilt cylinder extension signal
`from a maximum pilot pressure to substantially zero
`from the tilt cylinder extension sensor 23 and stores the
`pressure.
`signal in the non-volatile memory at a desired bucket
`The raise and lower resolvers 44,46 direct one of the
`position address. Thus when the operator actuates the
`electrohydraulic pilot signal and the lever pilot signal to
`push button 56 when the lift arm assembly 14 is below
`a main valve 48 having raise and lower ports 50,52 that
`the midpoint, signals are stored in memory which iden
`are connected respectively to the raise and lower pilot
`tify the desired location of a front portion of the bucket
`lines 32,34. The raise resolver 44 receives the electrohy
`16 when the implement is lowered.
`draulic pilot signal from the raise electrohydraulic pilot '
`In the preferred embodiment, the controller 30 is
`valve 40 and the lever pilot signal from the raise pilot
`connected to a tilt detent mechanism (not shown). In
`line 32. The raise resolver 44 allows the pilot signal
`the event that the bucket 16 is tilted below the position
`having the greater pressure to ?ow to the raise port 50
`corresponding to the signal stored at the desired bucket
`of the main valve 48 and prevents the pilot signal having
`position address and a tilt control lever (not shown) is
`the lesser pressure from reaching the main valve 48.
`moved to a rackback detent position, the tilt detent
`Thus, if the lever pilot signal has a pressure that is
`mechanism is actuated to maintain'the control lever in
`greater than that of the electrohydraulic pilot signal, the
`that position. The tilt cylinder 20 responsively moves
`the bucket toward the position de?ned by the signal
`main valve 48 is controlled in response to the position of 50
`the control lever 24; whereas if the electrohydraulic
`stored at the desired bucket position address. As the
`pilot signal has a pressure that is greater than that of the
`bucket is tilting, the controller 30 senses the tilt cylinder
`lever pilot signal, the main valve 48 is controlled in
`extension signal and deactuates the tilt detent mecha
`response to the magnitude of current ?owing from the
`nism in response to the tilt cylinder extension signal
`being substantially equivalent to the signal stored at the
`controller 30 to the electrohydraulic valve 40. While
`the operation of only the raise resolver 44 has been
`desired bucket position address. When the tilt detent
`described, it should be appreciated that the lower re
`mechanism is deactuated, the tilt control lever returns
`solver 46 operates in a similar fashion.
`to a neutral position and the tilt cylinder 20 maintains
`The main valve 48 is connected to and between the
`the bucket in substantially the same position with re
`raise and lower pilot lines 32,34, a hydraulic pump (not
`spect to the lift arm assembly 14.
`shown), and the lift cylinders 18. The raise and lower
`In the preferred embodiment, the controller 30 also
`periodically samples the lift cylinder extension signals
`pilot lines 32,34 are respectively connected to the main
`valve 48 at the raise and lower ports 50,52. The main
`and calculates the velocity of the lift arm assembly 14in
`response to recently sampled cylinder extension signals.
`valve 48 serves to controllably direct pressurized ?uid
`to the head end and rod end of the lift cylinders 18 in
`Referring now to FIG. 4, the embodiment of the
`response to receiving pilot signals in the raise and lower
`instant invention which slows the implement before
`ports 50,52. Since the raise and lower resolvers 44,46
`reaching the lift kickout height is described. It is as
`sumed that the operator has previously selected the lift
`each direct one of either the lever or electrohydraulic
`
`45
`
`55
`
`65
`
`Page 8 of 13
`
`

`

`10
`
`20
`
`25
`
`30
`
`5,189,940
`8
`7
`kickout height and lower kickout height by respectively
`tween the kickout begin modulation position and the
`associated kickout height and the controller 30 pro
`moving the lift arm assembly to the desired dump and
`return to dig positions and activating the kickout set
`duces a kickout signal 66 to cause the detent mechanism
`26 to release the control lever 24 from the detent posi
`switch. Thus, cylinder extension signals are stored in
`tion.
`the controller 30 at the respective upper and lower
`When the control lever 24 is released, the control
`kickout addresses. It should be appreciated that default
`lever 24 returns to the neutral position at which the
`kickout heights may be stored in the controller memory
`lever operated pilot valve 28 is closed. As the control
`to use as the raise and lower kickout heights if the oper
`lever 24 begins to move toward the neutral position, a
`ator does not select the raise and lower kickout heights
`modulation process is begun in which the controller 30
`himself.
`'
`calculates 68 the magnitude of current to be directed to
`The operator moves the control lever 24 to extend
`the raise electrohydraulic pilot valve 40. The magnitude
`the lift cylinders 18 and raise the bucket. At this point,
`of current is chosen as a function of the difference signal
`the electrohydraulic valves are closed and the lever
`and position of the control lever 24 prior to being re
`operated pilot valve 28 is producing the lever operated
`leased from the detent position. The raise electrohy
`' pilot signal. Since the lever operated pilot signal now
`draulic pilot valve 40 is preferably opened sufficiently
`has a greater pressure than the electrohydraulic pilot
`to produce a pilot signal having a pressure substantially
`signal, the resolver directs the lever operated pilot sig
`equivalent to or slightly less than the pressure of the
`nal to the main valve 48.
`lever pilot signal prior to the control lever 24 being
`The controller 30 reads 58 the lever position signal
`released from the detent position. Advantageously, the
`from the control lever position sensor 36 and deter
`electrohydraulic pilot signal is produced before the
`mines 60 whether the control lever 24 is positioned
`pressure of the lever pilot signal is signi?cantly reduced.
`outside the range de?ned by the upper and lower detent
`Once the electrohydraulic pilot signal is produced and
`positions. This function is performed by comparing the
`lever position signal to predetermined signals corre
`the pressure of the lever pilot signal begins to decrease, ‘
`the pressure of the electrohydraulic pilot signal is
`sponding to the lever position signal when the control
`greater than the pressure of the lever pilot signal. As a
`‘lever 24 is in the raise and lower detent positions. If the
`result, the resolver 44 directs the electrohydraulic pilot
`lever position signal is within the range between the
`signal to the main valve 48 in place of the lever pilot
`two predetermined magnitudes, the controller contin
`signal.
`ues to read 58 the lever position signal and the detent
`The controller 30 then calculates 70 the difference
`mechanism 26 is not engaged. However, if the lever
`position signal is outside the range de?ned by the prede
`signal and compares 72 the difference signal to a second
`predetermined constant, K2. In the preferred embodi
`termined magnitudes, the detent mechanism 26 engages
`ment, the second predetermined constant, K2, is chosen
`the control lever 24.
`to reflect the distance from the current implement posi
`Following the actuation of the detent mechanism 26,
`tion to the kickout height at which the controller 30 can
`the controller 30 calculates a difference signal. In the
`acceptably bring the lift arm assembly 14 to a complete
`preferred embodiment, the calculation of the difference
`signal entails determining whether the control lever is
`stop. Thus, K2 defines an acceptable error range in
`which the lift arm assembly 14 may be stopped.
`positioned to cause the lift arm assembly to raise or to
`lower, reading the present lift cylinder extension signal,
`If the difference signal is less than K2, then the elec
`trohydraulic pilot valves are completely closed. How
`selecting the appropriate raise or lower kickout address
`ever, if the difference signal is greater than K2, then the
`in response to the position of the control lever, and
`controller 30 calculates 68 the electrohydraulic pilot
`subtracting the present lift cylinder extension signal
`from the lift cylinder extension signal in the selected
`valve current as a function of the difference signal and
`the magnitude of the current that was sent to the elec
`kickout address.
`trohydraulic pilot valve at the beginning of the modula
`The difference signal is then compared 64 to a prede
`tion process. In the preferred embodiment, the electro
`termined constant, Kl. The predetermined constant,
`hydraulic pilot valve current is directly proportional to
`K1, is preferably chosen to re?ect the difference be
`tween the kickout begin-modulation-position, illus
`' the ratio of the present difference signal to the differ
`ence signal calculated at the beginning of the modula
`trated in FIG. 2, and the associated kickout height.
`tion process. Thus, the electrohydraulic pilot valve
`Thus, the value of K1 determines the distance through
`current is directly proportional to the distance from the
`which the lift arm assembly 14 moves as it is brought to
`implement to the lift kickout height when the imple
`a stop. A relatively large difference signal infers a grad
`ment is withinthe respective modulation region defined
`ual stopping of the lift arm assembly 14; whereas a
`by the kickout height and the begin-modulation-posi
`relatively small difference signal infers bringing the lift
`tion. As a result, the electrohydraulic pilot valve 40 is
`arm assembly 14 to a stop in a relatively short distance.
`progressively closed and the implement velocity is
`While Kl may be a set value irrespective of lift arm
`gradually reduced as the implement approaches the
`velocity, the preferred embodiment calculates 65 Kl as
`kickout height.
`a function of the velocity of the lift arm assembly and
`provides a substantially larger stopping distance when
`When the function described in FIG. 4 is used to
`lower the implement to the lower kickout height, the
`the lift arm assembly is moving relatively quickly. It
`60
`controller 30 reads the tilt cylinder extension sensor 23
`should be appreciated that Kl may also be determined
`to determine whether the bucket is tilted such that the
`in response to other sensed parameters, such as the
`front portion of the bucket 16 will impact the ground
`'acceleration of the implement.
`before the lift arm assembly 14 is lowered to the lower
`If the difference signal is greater than K1, the lift arm
`kickout height. To prevent this contingency, the con
`assembly 14 is not between the kickout begin-modula
`65
`troller 30 compares the signal from the tilt cylinder
`tion-position and the associated kickout height and nor
`extension sensor 23 to a predetermined signal stored in
`mal operator-lever control continues. If the difference
`memory and compensates the signal stored at the lower
`signal is less than K1, the lift arm assembly 14 is be
`
`40
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`45
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`50
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`20
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`25
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`30
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`35
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`5,189,940
`9
`kickout address when the bucket is tilted below the
`position de?ned by the predetermine