Unlted States Patent
`
`[19]
`
`llllllllllllllllllllllIllll||!||ll|ll||llll|l|lIlilllllllllllllllllllllllll
`U5005303581A
`[11] Patent Number:
`
`5,303,581
`
` .
`
`McQueen
`
`,
`
`[45] Date of Patent:
`
`Apr. 19, 1994
`
`[54] METHOD OF AND AN APPARATUS FOR
`Eggs?“ A FAULT IN A RETURN
`
`[56]
`
`References Cited
`U.s. PATENT DOCUMENTS
`5,150,681
`9/1992 Kull et al.
`...................... 73/118.1 X
`
`[75]
`
`Inventor: Alastair M. McQueen, Solihull,
`«
`England
`
`Primary Examiner—Jerry W. Myracle
`Attorney, Agent, or Firm—Jenner & Block
`
`,
`[73] Assrgnee:
`
`_
`_
`Lucas Industries PLC, Sohhull,
`England
`
`[21] Appl. NO': 967’297
`
`[22] Filed:
`
`001- 27, 1992
`
`Int. Cl.5 ............................................ G01M 19/00
`[51]
`[52] US. Cl. ........................... 73/118.1; 73/8659
`[58] Field of Search .................... 73/1181, 116, 865.9,
`73/8661; 123/690
`
`[57]
`
`ABSTRACT
`
`,
`_
`A return system for a throttle of an internal combustion
`engine has a first return device in the form of a spring
`for returning the throttle to a first return position and a
`second return device in the form of a motor for return-
`ing the throttle to a second return position beyond the
`first return position. A position sensor determines the
`first and second return positions and a fault is indicated
`if the second return position is not beyond the first
`return position.
`
`7 Claims, 3 Drawing Sheets
`
`
`
`
`
`CLOSING TORQUE
`50
`
`7
`
`,
`
`SHAFT TWIST
`
`
`
`VW EX1005
`
`US. Patent No. 6,588,260
`
`VW EX1005
`U.S. Patent No. 6,588,260
`
`

`

`US. Patent
`
`Apr. 19, 1994
`
`Sheet 1 of 3
`
`5,303,581
`
`
`
`
`
`CLOSING TORQUE
`50
`
`7
`
`cfi SHAFT TWIST 3
`
`
`
`

`

`US. Patent
`
`Apr. 19, 1994
`
`"Sheet 2 of 3
`
`5,303,581
`
`
`
`FlGZ
`
`

`

`US. Patent
`
`Apr. 19, 1994
`
`Sheet 3 of 3
`
`5,303,581
`
`YES
`
`33
`
`DRIVE STAGE POWER
`FULL OPENING
`
`STORE VALUE
`IN MEMORY
`
`READ THROTTLE
`ANGLE
`
`DRIVE STAGE POWER
`“OFF"
`
`READ THROTTLE
`ANGLE
`
`31
`
`32
`
`34
`
`35
`
`36
`
`FIG 3
`'
`
`'
`
`DRIVE STAGE POWER
`“FULL CLOSING”
`
`37
`
`38
`
`'
`
`39
`
`READ THROTTLE
`
`ANGLE
`
`#A >#BOs
`
`YE S
`
`NO
`
`43
`
`#1
`
`STORE FAULT FLAG
`IN MEMORY
`
`STORE .FLAG
`IN MEMORY
`
`1+4
`
`45
`
`LIMP HOME MODE
`ON POWER UP
`
`POWER DOWN
`ECU
`
`“2
`POWER DOWN
`Ecu
`
`

`

`1
`
`5,303,581
`
`METHOD OF AND AN APPARATUS FOR
`DETECTING A FAULT IN A RETURN SYSTEM
`
`The present invention relates to a method of and an
`apparatus for detecting a fault in a return system, for
`instance in a closing system for a throttle of an internal
`combustion engine.
`The mechanical connection between a driver oper-
`ated control, such as an accelerator pedal of a vehicle,
`and a throttle in an internal combustion engine induc-
`tion system is frequently replaced nowadays by a so
`called “drive-by-wire” system. In such a drive-by-wire
`system, the accelerator pedal operates a position trans-
`ducer which supplies signals to an engine control unit in
`accordance with the position of the accelerator pedal.
`The electronic control unit (ECU) supplies signals
`which control a servo motor which controls the open-
`ing of a throttle via a suitable mechanical linkage or
`mechanism. Typically, a torque motor is connected to a
`shaft carrying the throttle and connected to a position
`transducer.
`
`is a common requirement for two “return-to-
`It
`closed” systems to be provided in order to close the
`engine throttle when the ECU demands that the throttle
`be closed. These two systems are required to function
`independently of each other so that, should one system
`fail, the other system will ensure that the engine throttle
`is closed when required. Such an arrangement reduces
`the possibility of the engine operating in an undesired
`and possibly dangerous mode in the event of a fault or
`failure.
`In one known arrangement of this type, one system is
`provided by a return spring which constantly urges the
`throttle towards its closed position. The second system
`comprises the servo motor itself which, in the absence
`of a fault, drives the throttle to its closed position when
`a suitable demand signal is received from the ECU.
`Thus, in the event of a failure in the servo motor, the
`return spring closes the throttle whereas, in the event of
`a failure of the return spring, the servo motor closes the
`throttle.
`A possible problem with such an arrangement is that
`a dormant fault can develop and remain undetected
`such that, should a second failure occur, the ability of
`the ECU to return the throttle to its closed position may
`be lost. For instance, if the return spring breaks, the
`throttle can still be returned to its closed position by the
`servo motor and failure of the return spring may remain
`undetected. Should a fault subsequently occur in the
`servo motor or its drive circuitry, the engine may oper-
`ate in an undesired and possibly dangerous mode. Simi-
`larly, should a fault occur in a driver of the servo mOtor
`such that the servo motor cannot close the throttle, the
`return spring will continue to provide this function and
`the fault in the second system may remain undetected
`unless and until the return spring fails.
`According to a first aspect of the invention, there is
`provided an apparatus for detecting a fault in a return
`system, comprising first return means for urging a
`mechanism of the system to a first return position, sec-
`ond return means for urging the mechanism to a second
`return position beyond the first return position, means
`for determining the first and second return positions,
`and means for indicating a fault if the seCOnd return
`position is not beyond the first return position.
`
`10
`
`15
`
`20
`
`25
`
`3O
`
`35
`
`40
`
`45
`
`50
`
`55
`
`65
`
`2
`The return system may comprise a closing system, for
`instance a throttle closing system suitable for use with a
`throttle of an internal combustion engine.
`The first return means may comprise a return spring.
`The second return means may comprise a motor.
`The second return means and the position determin-
`ing means may be connected via resilient means, such as
`a rotationally resilient shaft forming part of the mecha-
`nism, to the throttle or other device controlled by the
`return system. Alternatively or additionally, a resilient
`return end stop may be provided.
`The position determining means may comprise a ro-
`tary position transducer. For instance, when the second
`return means is a motor, the motor and rotary position
`transducer may comprise part of a servo feedback sys-
`tem for controlling the opening of the throttle or the
`position of another device controlled by the return
`system.
`According to a second aspect of the invention, there
`is provided a method of detecting a fault in a return
`system, comprising urging a mechanism of the system
`by a first return means to a first return position, deter-
`mining the first return position, urging the mechanism
`by a second return means to a second return position
`beyond the first return position, determining the second
`return position, and indicating a fault if the second re-
`turn position is not beyond the first return position.
`It is thus possible to provide an arrangement which is
`capable of detecting a latent fault or failure in a return
`system, such as a throttle closing system. When the
`throttle is to be closed, for instance when an internal
`combustion engine is switched off, a first return means
`such as a spring causes the throttle mechanism to close
`the throttle. The second means such as a motor is then
`activated so as to increase the closing force to move the
`mechanism beyond the point which corresponds to the
`closed throttle. If both return means are functioning
`correctly, the mechanism will move further in the clos—
`ing direction and subsequent operation of the engine
`may continue as normal. However, if a failure should
`occur for instance in the motor or in the motor driver,
`the mechanism will not be urged beyond the return
`position established by the first means and a fault will be
`indicated. Suitable action may then be taken, for in-
`stance to disable further operation of the engine or to
`limit operation in order to provide a “limp home”
`mode.
`In order to detect a failure of the first return means
`such as the return spring, the first return position estab-
`lished by the first return means may be compared with
`a stored value, for instance corresponding to substantial
`closure of the throttle. If this value is not achieved by
`the first return means before the second return means is
`actuated to close the throttle, a fault indication may
`again be given and operation of the engine prevented or
`limited to a limp home mode. It is thus possible to detect
`a latent fault in a throttle closing system or the like so as
`to prevent or restrict continued operation and therefore
`improve the safety of the system.
`The invention will be further described, by way of
`example, with reference to the accompanying drawings,
`in which:
`FIG. 1 is a diagram of part of a control system for a
`throttle of an internal combustion engine;
`FIG. 2 is a block diagram of the throttle control
`system including a closing fault detection apparatus
`constituting an embodiment of the invention; and
`
`

`

`5,303,581
`
`3
`FIG. 3 is a flow diagram illustrating operation of the
`apparatus of FIG. 2.
`A throttle shaft 1 is connected at one end to a cam 2
`
`which cooperates with a throttle closed stop 3 in order
`to limit the movement of a throttle (not shown in FIG.
`1) in the closing direction. The cam 2 is shown, by way
`of example, as being connected to one end of a return
`spring 4 whose other end is fixed to a fixed part 5 of an
`engine induction system and which operates in tension
`so as to urge the cam 2 towards the stop 3.
`The other end of the shaft 1 is connected to the hub
`6 of a servo motor having motor windings 7. The wind-
`ings 7 are connected to a driver of the “H bridge” type
`comprising power transistors 8 to 11 arranged in a
`bridge configuration between a common supply line 12
`and a 12 volt positive supply line 13. In order to drive
`the motor in a first direction, the transistors 9 and 10 are
`turned on whereas the transistors 8 and 11 are turned
`off. In order to drive the motor in the opposite direc-
`tion, the transistors 8 and 11 are turned on whereas the
`transistors 9 and 10 are turned off. Drive may be by a
`continuous or analogue signal, or may be by a pulsed
`waveform, for instance of variable duty cycle.
`The motor hub 6 is connected via a shaft 14 to a
`
`rotary position sensor 15. The sensor 15 comprises a
`rotary variable potentiometer having a resistive track
`and a slider which contacts the track at a position deter-
`mined by the rotary position of the shaft 14. A fixed
`stable voltage is applied across the resistive track so that
`the voltage at the slider represents the rotary or angular
`position of the shaft 14 and hence of the motor hub 6.
`FIG. 2 shows an internal combustion engine 20 pro-
`vided with an induction system 21 including a throttle
`22 attached to the shaft 1. The throttle 22 controls the
`supply of air through the induction system and hence
`the output demand of the engine 20.
`The H bridge driver of FIG. 1 is shown at 23 as part
`ofan electronic control unit 24. The output of the posi-
`tion sensor 15 is connected to an analogue/digital con-
`verter (ADC) 25 whose output is connected to a micro-
`processor (pP) 26. A first output ofthe microprocessor
`26 is connected to the driver 23 and, in the embodiment
`shown, supplies a variable duty cycle pulse output suit-
`able for driving the motor 6, 7 directly. Alternatively, a
`digital/analogue converter may be provided between
`the microprocessor 26 and the driver 23.
`Operation of the microprocessor 26 is controlled by a
`program stored in a read only memory (ROM) 27. The
`stored program provides various functions so that the
`electronic control unit 24 operates as an engine manage-
`ment system, receiving inputs from further sensors (not
`shown) and supplying control signals to various devices
`(not shown) such as a fuel injection system and an igni-
`tion timing system. The microprocessor 26 has a further
`output connected to an indicator 28 for providing an
`indication of a fault in the throttle closing system.
`The throttle closure fault determining system oper-
`ates in accordance with the program illustrated by the
`flow diagram in FIG. 3. At 30, a periodic check is made
`on whether the engine 20 is operating. If the engine is
`operating, no further action is taken until
`the next
`check. If the engine is off, the microprocessor 26 causes,
`at 31, the driver 23 to supply full opening power to the
`motor 6, 7 so as to open the throttle fully. At 32, the
`throttle angle indicated by the sensor 15 is read and is
`stored at 33 for system calibration and checking pur-
`poses. At 34, the driver 23 is switched off.
`
`4
`In the absence of a fault, the return spring 4 closes the
`throttle such that the cam 2 abuts against the stop 3.
`After a suitable time interval to allow the throttle to
`close under the action ofthe spring 4, the throttle angle
`is read at 35 and stored as “A” at 36.
`
`10
`
`IS
`
`20
`
`25
`
`3O
`
`35
`
`4s
`
`50
`
`55
`
`65
`
`At 37, the microprocessor 26 causes the driver 23 to
`supply full closing power to the motor 6, 7. The motor
`therefore rotates the adjacent end of the throttle shaft 1
`in the direction indicated by the arrow 50 in FIG. 1.
`The closing torque of the motor acts on the resilience of
`the shaft 1 such that the sensor 15 detects a position
`which is “more closed” than the position detected when
`the throttle was closed by the Spring 4 without the
`closing torque supplied by the motor. The throttle angle
`is again read at 38 and stored as variable “B” at 39. The
`motor 6, 7 can then be deactivated by switching off the
`driver 23.
`At 40, the variables A and B are compared. If A is
`greater than B, a flag is stored in non-volatile memory
`at 41 indicating that both throttle closing systems are
`functioning correctly and the electronic control unit 24
`is powered down at 42 to await further operation of the
`engine.
`In the event of a fault in the driver 23, such as one or
`more failed transistors, or in the motor 6, 7, when full
`closing power is applied in the step 37, closing torque is
`not applied to the shaft 1 so that the position read by the
`sensor 15in the step 38 is substantially equal to or possi-
`bly greater than that read in the step 35. Thus, the step
`40 detects that A is not greater than B and a step 43
`stores a fault flag in memory. At 44, the electronic con-
`trol unit 24 is set such that, on being powered up again
`for subsequent operation of the engine 20, the engine
`may only operate in a limp home mode. For instance,
`the electronic control unit 24 may be prevented from
`opening the throttle 22 beyond a predetermined angle
`corresponding to a limited relatively low engine output.
`This allows a vehicle driven by the engine 20 to be
`driven home or to a garage while preventing damage to
`the engine or operation of the vehicle at a dangerous
`speed. Finally, the electronic control unit is powered
`down at 45 to await further operation of the engine.
`The step 43 which sets the fault flag causes the micro-
`processor 26 to illuminate a warning light 28 or provide
`any other suitable indication so as to alert a driver to the
`failure of the system 4. The limp home mode remains set
`and the indicator 28 actuated until remedial action is
`taken to repair the fault and the electronic control unit
`24 is reset, for instance by service personnel.
`Various modifications may be made within the scope
`of the invention. For instance, instead of or in addition
`to relying on the rotary resilience of the shaft 1, the end
`stop 3 may be made resilient such that the closing
`torque applied by the motor 6, 7 causes the shaft 1 to
`move beyond the throttle closed position established by
`the return spring 4. Also, the throttle angle A read at
`the step 35 may be compared with a predetermined
`angle so as to establish that the spring 40 is functioning
`correctly and has returned the throttle to its closed
`position.
`The resilience between the motor hub 6 and the cam
`2 may be provided by an existing mechanism between
`the motor and the throttle. Alternatively, steps may be
`taken to add or increase this resilience, for instance by
`providing the shaft 1 with a higher degree of resilience
`than is conventional.
`
`Although the rotary position sensor 15 is shown on
`the opposite side of the motor hub 14 to the throttle
`
`

`

`5,303,581
`
`,
`5
`shaft 1, the sensor 15 may be provided at any suitable
`location such that it is capable of detecting the addi-
`tional movement caused when the motor 6, 7 exerts
`closing torque.
`It is thus possible to provide an arrangement which
`reliably detects otherwise latent faults in one or more
`systems for closing an engine throttle. The possibility of
`an engine operating in an undesirable mode is thus sub-
`stantially reduced and a fault or failure can be rapidly
`repaired so as to restore correct full operation of the
`engine throttle control system.
`I claim:
`
`1. An apparatus for detecting a fault in a return sys-
`tem, comprising first return means for urging a mecha-
`nism of the system to a first return position, second
`return means for urging the mechanism to a second
`return position beyond the first return position, position
`determining means for determining the first and second
`return positions, and fault indicating means for indicat-
`ing a fault if the second return position is not beyond the
`first return position.
`
`6
`2. An apparatus as claimed in claim 1, in which said
`first return means comprises a spring.
`3. An apparatus as claimed in claim 1, in which said
`second return means comprises a motor.
`4. An apparatus as claimed in claim 1, in which said
`second return means and said position determining
`means are connected to the mechanism via resilient
`means.
`
`5. An apparatus as claimed in claim 4, in which said
`resilient means is a rotationally resilient shaft.
`6. An apparatus as claimed in claim 1, in which said
`position determining means is a rotary position trans-
`ducer.
`7. A method of detecting a fault in a return system,
`comprising urging a mechanism of the system by a first
`return means to a first return position, determining the
`first return position, urging the mechanism by a second
`return means to a second return position beyond the
`first return position, determining the second return posi-
`tion, and indicating a fault if the second return position
`is not beyond the first return position.
`i
`t
`t
`t
`t
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`