Throttle control and validation sensor

Abstract: An integrated throttle control and idle validation sensor includes mechanically coupled but electrically independent throttle control and idle validation components. A single mechanical input to the protective sensor housing corresponds to an accelerator pedal position and causes selective coupling of a supply voltage to one of an idle validation conductor and a throttle validation conductor for interpretation by an electronic control system. The throttle control system within the sensor housing comprises a potentiometer adapted for movement corresponding to the mechanical input whereby a variable voltage throttle control signal may be delivered to the electronic fuel control system. The sensor integrates previous separate throttle control and idle validation functions into a single environmentally secure housing and requires no calibration. The disclosed throttle system is more reliable and less costly than previously available separate throttle control and idle validation functions.

Description: The present invention applies to engine control systems and particularly to throttle control systems for electronic fuel control systems. Many vehicle throttle control systems now use electrical circuitry to deliver an electrical signal from the accelerator, such as an accelerator pedal or a hand control lever, to an electronic fuel control system. For example, a voltage signal provided to the electronic fuel control system corresponds to accelerator pedal or hand control position. When an "in-range" voltage level arrives at the electronic fuel control system, the electronic fuel control system responds by injecting a corresponding volume of fuel into the engine fuel system. In some applications, a control device failure can result in an invalid in-range throttle condition, i.e., an unintended in-range voltage level. Under such condition, even though the accelerator control device is at an idle position, the electronic fuel control system receives an erroneous throttle control signal and undesirably injects fuel in to the engine fuel system. Loss of engine throttle control, and possibly unintended vehicle acceleration, can result. To avoid such error conditions, a separate idle validation switch has been added to the accelerator control device as backup protection against such a failure. Typically, this switch provides a single pole double throw function wherein one side of the switch delivers a logic signal corresponding to valid idle operation only and the other side validates throttle operation. The switch is mounted to the accelerator control device in such a way that actuation of the accelerator control changes the switch position from its idle validation position to its throttle validation position. The electronic fuel control system ignores the throttle control signal until it receives a throttle validation signal by way of the switch. Accordingly, if an erroneous in-range throttle signal arrives at the electronic fuel control system, unintended fuel delivery is avoided because the electronic fuel control system has not yet received a throttle validation signal. The idle validation switch is attached to the accelerator pedal or hand control as a separate component. The switch is mounted to the accelerator control device in such manner to provide for switching according to the pedal or hand control lever position. It is necessary to adjust or calibrate the point at which the switching occurs to coincide with a specified throttle signal level, i.e., a point of transition between idling and throttle operation. This insures that the switch is in the idle valid mode when the driver releases the accelerator control device, and that the engine will have a smooth idle to power transition when the driver applies the throttle. Switch transition points are typically specified by the engine manufacturer. Installation of the switch can be difficult because of the sensitive calibration required to meet the engine manufacturer specifications, and the complex test procedures needed to insure that proper switch functioning occurs. Additionally, the switch must meet stringent environmental quality standards to function reliably in typical operating environments. These factors result in an expensive idle validation switch and, in some cases, marginal product reliability. The resulting product is also virtually impossible to service in the field without replacing the entire accelerator control assembly. Such difficult field service further adds to the overall cost of such idle validation systems. In WO-A-90/07054 there is disclosed an apparatus including a potentiometer mechanically coupled to the accelerator pedal providing two output signals and in US-A-4603675 an accelerator pedal is mechanically coupled to two potentiometers and the output of the sensors is used to detect malfunctions of the pedal sensor. However, these known devices require complex and potentially expensive repair and calibration procedures on mounting. According to the present invention there is provided a throttle control and validation sensor for sensing the position of an accelerator control device and providing a throttle demand control signal and a validation signal representing the position of the control device, the sensor comprising: a sensor housing securable to the accelerator control device; a single mechanical input means responsive to the position of the accelerator control device for delivering within the housing a mechanical indication of the control device position; sensor or integrated sensor and validation means within the housing, mechanically coupled in common to the single mechanical input means and responsive to the mechanical indication of the control device position to generate a position signal and position validation signal; and signal output or delivery means making available the position signal and the position validation signal externally of the housing. This sensor has considerable advantages over the prior art since the common mechanical connection establishes and maintains constant the required mechanical registration. The resulting integrated sensor can be installed on the control device without significant adjustment, or without calibration of the switch and sensor. Also, packaging of the idle validation switch in the sensor housing protects the switch from its environment, and thereby increases its reliability. The integrated package thereby enjoys reduced number of parts, increased reliability and serviceability, and reduced overall cost. In accordance with a preferred embodiment of the present invention, an accelerator position sensor is combined in an integrated sensor package with mechanical registration of the validation switch and throttle control sensor built into the sensor. The accelerator position sensor and idle validation switch are electrically separate units, but mechanically coupled for response to a common actuation mechanism. The invention is further described below, by way of example with reference to the accompanying drawings in which like reference numerals refer to like elements. FIG. 1 is a side view of an accelerator pedal, an integrated throttle control and idle validation sensor in accordance with the invention, and an electronic fuel control system, FIG. 2 is a sectional view of the pedal and sensor of FIG.1 taken along line 2-2 of FIG. 1, FIG. 3 is a perspective view of the integrated throttle control and idle validation sensor of FIG. 1, FIG. 4 is an exploded view of the sensor of FIG. 3, FIG. 5 is a schematic diagram of the sensor and electronic fuel control system, showing electronic coupling, and FIG. 6 illustrates the relationship between mechanical operation of the sensor and production of the throttle control signal, idle validation signal and throttle validation signal. FIG. 1 shows a fuel control device in the form of an accelerator pedal 10, pivotally coupled at pin 12 to a base plate 14. Base plate 14 attaches to the floor of a vehicle (not shown) in conventional manner. An integrated throttle control and idle validation sensor 16 is mounted to the underside of the pedal 10 for the combined functions of providing a throttle control signal, an idle validation signal, an a throttle validation signal. The sensor 16 is coupled by way of a multi-conductor cable 18 to an electronic fuel control system 20. The system 20 is a conventional control system, and in the illustrated embodiment corresponds to a Cummins electronic fuel control system available under the trade name CELECT. While illustrated with reference to a specific electronic fuel control system, it will be appreciated that the sensor 16 may be adapted to operate with a wide variety of electronic fuel control systems and control devices. A lever arm 22 is pivotally mounted on the sensor 16 and carries a roller 24 at its distal end. The base plate 14 includes an inclined surface 26 engaged by the roller 24. As the operator depresses pedal 10 to accelerate the vehicle, the pedal 10 rotates about pin 12 in the direction 30, clockwise in the view of FIG. 1. As the roller 24 moves upward along surface 26 in response to downward actuation of pedal 10, the lever arm 22 pivots in the direction 32, counter clockwise in the view of FIG. 1, about the axis 34. The sensor 16 detects such movement of the lever arm 22 and delivers to the system 20 by way of the cable 18 suitable signals both indicating and validating the position of the pedal 10. FIG. 2 shows a sectional view of the assembly of FIG. 1 taken through the sensor 16 and the arm 22. In FIG. 2, a double spring 40 encircles a shaft 42 mounted upon the body of the pedal 10 for rotation about the shaft axis 34. The spring 40 couples the underside of the pedal 10 and the lever arm 22 to bias lever arm 22 in the direction 33 opposite that of direction 32. Pedal 10 is thereby spring biased in the direction 31, opposite of direction 30, and toward the idle position as shown in FIG. 1. The shaft 42 is pivotally mounted on the body of the pedal 10 but is fixedly attached to the lever arm 22 such that movement of pedal 10 results in rotation of shaft 42 relative to sensor 16 and about the axis 34. The sensor 16, being mechanically coupled to the shaft 42, responds to rotation of shaft 42 by producing the desired throttle control, idle validation, and throttle validation signals according to pedal position as described hereinafter. FIG. 3. shows in perspective the throttle control and idle validation sensor 16. The sensor 16 includes a slot formation 46 for mechanical coupling to shaft 42 and an electrical connector formation 48 for electrical coupling to the multi-conductor cable 18. The shaft 42 engages the slot formation 46 and rotates slot formation 46 about the axis 34 as a mechanical input to sensor 16. Movement of the pedal 10 about the pin 12 results in a mechanical input, by way of shaft 42, to the sensor 16 at the slot formation 46. In response, the sensor 16 generates the necessary signals at the connector formation 48 for delivery by way of the cable 18 to the electronic fuel control system 20. It will, therefore, be appreciated that the sensor 16 provides an integrated package receiving a mechanical input and developing suitable electrical outputs. Sensor 16 requires no calibration for idle validation relative to throttle control as such is built into the integrated package. Also, by enclosing the throttle control and idle validation functions in the housing of sensor 16, the risk of exposure to environmental conditions, possibly effecting operation of the sensor, is substantially eliminated. FIG. 4 is a view of the sensor 16 exploded along the axis 34. The sensor 16 comprises an external housing 50, a seal 52, a printed circuit element 54, a termination wedge 56, a rotor 58, a spring 60, and a cover 62. Within housing 50, a terminal structure 64 carries conductive elements, corresponding to those of cable 18, from within the connector formation 48 to the interior of housing 50. As described more fully below, the printed circuit element 54 includes a resistive element 66, an idle conductive element 68, and a throttle conductive element 70 suitable etched onto the substrate circuit element 54. The rotor 58 includes a throttle wiper 72 and an idle/throttle validation wiper 74. In assembly of the sensor 16, the seal 52 is first inserted within housing 50, then the circuit element 54 rests within the housing 50 so that elements 66, 68, and 70 of the circuit element 54 face inward. A flat portion 76 of printed circuit element 54 rests adjacent the terminal structure 64. The circuit element 54 includes additional conductive traces (not shown) for coupling the elements 66, 68, and 70 to suitable terminal contact points (not shown) of the flat portion 76. The termination wedge 56 suitably interconnects the elements 66, 68, and 70 of element 54 by way of the terminal contacts (not shown) of the flat portion 76, with the conductors of terminal structure 64. Electrical coupling between individual conductors of the cable 18 and portions of the circuit element 54 thereby established. The rotor 58 is received in the housing 50 within the interior of the circuit element 54, and the wipers 72 and 74 contact portions of the circuit element. Specifically the throttle wiper 72 contacts the resistive element 66 of circuit element and the idle/throttle validation wiper 74 selectively contacts one of, or neither of, the idle conductive element 68 and the throttle conductive element 70. The seal 52 seals the rotor 58 within housing 50 whilst allowing rotation about the axis 34. The spring 60 couples the rotor 58 to the housing 50 to suitably bias the rotor toward a full return position. The cover 62 attaches to housing 50 to rotatably support the rotor 54 and to seal the entire assembly. The rotor 58 includes the slot formation 46 (not shown, but indicated by its reference numeral in FIG. 4). The rotor 58 then rotates within the housing 50 and about the axis 34 according to rotation of the shaft 42, i.e., in response to actuation of the pedal 10. The throttle wiper 72 thereby moves along the resistive element 66 while, for given ranges of the angular position of the rotor 58, the validation wiper 74 contacts one of the idle validation conductive element 68, the idle validation conductive element 70, and portion 69 between them. FIG. 5 illustrates electrical connections between portions of the sensor 16 and the electronic fuel control system 20 as established by the conductors of the cable 18. In FIG. 5, the validation wiper 74 together with the conductive elements 68 and 70 and non-conductive portion 69 comprise a switch 78. The resistive element 66 and the throttle wiper 72 comprise a potentiometer 80. The switch 78 and the potentiometer 80 are mechanically coupled by way of the rotor 58, but are electrically separate. A voltage supply conductor 82 of cable 18 connects, by way of the structure 64, the wedge 56, and conductive traces of the circuit element 54, to the wiper 74, i.e., to the common pole of the switch 78. An idle active conductor 83 of cable 18 is connected in a similar manner to the idle conductive element 68. A throttle active conductor 84 of the cable 18 is similarly connected to the throttle conductive element 70. The switch 74 selectively routes the supply voltage present on the conductor 82 to neither or one of cable conductors 83 and 84 for interpretation by the electronic fuel control system 20. A supply voltage potential on idle active conductor 83 validates an idle position for the pedal 10 while a supply voltage potential on throttle active conductor 84 validates an in-range throttle control signal. A supply voltage on neither of conductors 83 and 84, i.e., an open connection, indicates to the system 20 a transition between an idle active and throttle active condition to pedal 10. A second voltage supply conductor 85 of cable 18 delivers a supply voltage to end 66b of the resistive element 66 while a ground conductor 87 of the cable is connected to the opposite end 66a of the resistive element as a ground return to electronic fuel control system 20. A throttle position conductor 86 of the cable 18 is connected to the wiper 72 of the potentiometer 80 whereby the voltage potential on the throttle position conductor 86 corresponds to the position of the wiper 72, more particularly, to the position of the pedal 10. As noted above, the switch 78 and potentiometer 80 are mechanically coupled by way of rotor 58. As rotor 58 moves from its full return position through a given range of angular movement, corresponding to full actuation of the pedal 10, the wiper 72 moves from near end 66b toward end 66a of resistive element 66. Concurrently with such rotation of the rotor 54, the wiper 74 initially contacts the conductive element 68, but as the rotor 54 moves through a given angular transition range, it disengages from the conductive element 68 and rests against the non-conductive portion 69. At the end of this transition zone range, the wiper 74 contacts conductive element 70. Thus, rotation of the rotor 54 through its angular range of motion corresponds to a continuously variable voltage signal on the throttle position conductor 86, and a suitable presentation of discrete bi-stable logic validation signals on the idle active conductor 83 and throttle active conductor 84. In the preferred embodiment, the rotor 54 has a full range of approximately 70 degrees of rotation corresponding to movement of pedal 10 from idle to full acceleration. The transition zone range, between idle validation and throttle validation, is determined by the extent of the non-conductive portion 69 of the circuit element 54 separating conductive elements 68 and 70. As will be apparent, a variety of configuration for sensor 16 will yield a variety of rotor 54 movement ranges and transition zone ranges as desired. FIG. 6 relates the position of the wiper 72, in terms of a rotation angle of the rotor 58, on the horizontal axis to the throttle control signal voltage, on the vertical axis, delivered to the electronic fuel control system 20 by way of the conductor 86. As the angular position of the rotor 58 moves from an idle position 100 to a full throttle position 102, the voltage at the wiper 72 ramps linearly from an idle voltage 104 to a full throttle voltage 106. The wiper 74 similarly moves from contact with idle conductive element 68 through a transition zone 108 and on to contact with throttle conductive element 70. Thus, as rotor 58 moves from its idle position 100 to a full throttle position 102, the voltage on the conductor 83 of the cable 18, representing an idle active signal, remains at the supply voltage V s1 until the wiper 74 loses contact with the conductive element 68. At this time the idle active conductor 83 presents an open circuit to the system 20. Continuing with rotation of rotor 58 toward the full throttle position 102, the wiper 74 eventually contacts the conductive element 70 whereat the voltage on the conductor 84, representing a throttle active signal, moves from being open to the supply voltage potential V s2 . The electronic fuel control system 20 monitors the throttle position conductor 86, the idle active conductor 83 and the throttle position conductor 86, the idle active conductor 83 and the throttle active conductor 84 of the cable 18. A supply voltage potential of the idle active conductor 83 validates the idle position for pedal 10 and the system 20 ignores the signal on the throttle position conductor 86. A supply voltage potential on throttle active conductor 84 validates an in-range throttle control signal on the throttle position conductor 86 and an appropriate volume of fuel is delivered to the vehicle engine. An open circuit on both conductors 83 and 84 indicates to the system 20 a throttle transition between an idle condition and a throttle condition. The system 20 reacts as programmed according to the necessary engine specification requirements for transition between idle and throttle. Thus, an integrated throttle control and idle validation sensor has been shown and described. The integrated package reacts to accelerator pedal position by way of a single mechanical input and delivers suitable electrical signals by way of the cable 18 to the electronic fuel control system 20. The sensor and validation switch enjoy protection from environmental conditions, i.e. the cab environment, by virtue of its integrated packaging. Also, installation of sensor 16 requires no calibration between the throttle control portions, i.e. the wiper 72 and the resistive element 66, and the idle validation portions, i.e. the wiper 74 and the conductive elements 68 and 70. It will be appreciated that the present invention is not restricted to the particular embodiment that has been described and illustrated, for example although the invention has been shown with a foot operated accelerator pedal, it may be applied to a variety of control devices where separate validation signals are desired.

Claims: A throttle control and validation sensor (16) for sensing the position of an accelerator control device (10) and providing a throttle demand control signal and a validation signal representing the position of the control device, the sensor comprising: a sensor housing (50) securable to the accelerator control device; a single mechanical input means responsive to the position of the accelerator control device for delivering within the housing (50) a mechanical indication of the control device position; sensor or integrated sensor and validation means within the housing, mechanically coupled in common to the single mechanical input means and responsive to the mechanical indication of the control device position to generate a position signal and position validation signal; and signal output or delivery means making available the position signal and the position validation signal externally of the housing. A sensor as claimed in claim 1, wherein the position signal is a continuous signal identifying control device position inside or outside a full range of the position of the control device. A sensor as claimed in claim 1 or 2, wherein the validation signal is a discrete signal identifying the control device position within a given range of control device positions, the given range being less than a full range of control device positions. A sensor as claimed in claim 3, wherein the given range of control device positions corresponds to an idle condition of the control device. A sensor as claimed in claim 1 or 2, wherein the validation signal identifies a control device position within a plurality of control device position ranges, each of the plurality of ranges being less than a full control device position range and mutually exclusive thereamong. A sensor as claimed in claim 5, wherein a first range of the plurality of ranges corresponds to an idle condition of the control device and a second one of the ranges corresponds to non-idle condition of the control device. A sensor as claimed in any preceding claim, wherein the housing (50) is arranged to protect the sensor or integrated sensor and validation means against environmental conditions surrounding the housing. A sensor as claimed in any preceding claim for an apparatus having an accelerator control device (10) and an electronic fuel control system (20), the control device being selectively positionable to indicate throttle control by way of the sensor to the electronic fuel control system, wherein: the housing (50) is arranged to be mounted on the accelerator control device and to be sealed to substantially isolate the interior of the housing against environmental conditions surrounding the sensor; the sensor means within the housing is arranged to generate an electrical throttle demand control signal corresponding to control device position and a bi-state electrical idle validation signal having a first state corresponding to an idle condition of the control device and a second state corresponding to a non-idle condition of the control device; and wherein the electrical output means makes available the throttle demand control signal and the idle validation signal externally of the housing for coupling to the electronic fuel control system. A sensor as claimed in claim 1 or 8, wherein the sensor means (68, 69, 74) produces a bi-state validation signal having a first state corresponding to a throttle condition of the control device and a second state corresponding to a non-throttle condition of the control device, and wherein the electrical output means makes available externally of the housing the validation signal. A sensor as claimed in any preceding claim, wherein the mechanical input means comprises a member (58) rotatably mounted within the housing and having a range of rotation corresponding to a range of control device positions. A sensor as claimed in claim 8, wherein the sensor means comprises: a potentiometer (80) having a first wiper (72) in contact with a resistive element (66), the resistive element carrying a first electrical potential thereacross whereby in response to the mechanical input the first wiper moves relative to the resistive element such that the electric potential at the first wiper corresponds to the throttle demand control signal; and a switch having a second wiper (74) and a contact element (70), the second wiper carrying a second electrical potential and the contact element carrying the idle validation signal whereby in response to the mechanical input the second wiper moves in coordination with the first wiper and relative to the contact element such that the second wiper selectively couples the second electrical potential to the contact element according to control device position. A sensor as claimed in claim 11, wherein the mechanical input means comprise a a body (58) rotatable within the housing and carrying the first and second wipers for mechanical coupling and coordinated movement thereof. A sensor as claimed in claim 11 or 12, wherein the second wiper (74) is arranged to selectively contact a second conductive element (68) according to control device position, whereby a validation signal may be taken from the second conductive element, and wherein the electrical output means makes available the validation signal externally of the housing (50). A sensor according to any preceding claim, wherein: the mechanical input to the interior of the housing is arranged for movement corresponding to movement of the accelerator control device, a first wiper (74) is located internally of the housing and is arranged for selective electrical contact with a first and second conductive element (68, 70) internally of the housing, a second wiper element (78) internally of the housing and arranged for electrical contact along the length of a resistive element (66) internally of the housing, and mechanical coupling means internally of the housing and responsive to the mechanical input for relative coordinated movement of the first and second wipers relative to the first and second conductive elements and the resistive element, respectively, whereby movement of the accelerator control device from an idle position through a full throttle position corresponds to the first wiper contacting the first conductive element and subsequent contacting the second conductive element and continuous contact of the second wiper element with the resistive element.

Inventors: HERING CHARLES ALLEN, SCHALLER DAVID A, HERING, CHARLES ALLEN, SCHALLER, DAVID A.
Applicants: WILLIAMS CONTROLS INC, WILLIAMS CONTROLS, INC.
Application year: 1992
Main classification: F02D41
IPC codes: F02D11, F02D9, G05G7, F02D41