Electronic throttle body with low friction default mechanism

[0002] This invention relates to electronic valve control systems and more particularly to electronic throttle control systems for internal combustion engines with low friction default mechanisms.

[0003] Valve assemblies for engines and related systems typically utilize rotatable valve members in fluid flow passageways to assist in regulating fluid flow through them. For example, throttle valve members are positioned in the air induction passageways in internal combustion engines. The valve assemblies are controlled either mechanically or electronically and utilize a mechanism which directly operates the valve member.

[0004] For electronic throttle bodies (ETB) or electronic control systems (ETC), it is desirable to have a failsafe mechanism or system which activates the throttle valve in the event that the electronic control or electronic system of the vehicle fails. There are several known electronic throttle control systems which utilize default (“failsafe”) mechanisms for closing the throttle valve or moving it to a slightly open position in the event of an electronic failure in the vehicle. It is desirable to minimize or reduce the frictional forces in the operation of the electronic throttle control system in order to allow the system to operate more accurately and not bind or jam. Reducing friction is important in the operation of the ETC since high friction increases gear loading and motor currents. Additionally, friction makes the ETC more difficult to control electronically as the mechanical system will become less predictable. For example, when the ETC controller issues a command, a specified motor current is issued and a particular throttle angle is expected in return. Depending on the magnitude of the requested change in plate angle, the controller calculates an expected overshoot error. Friction can make the overshoot unpredictable and the controller will have to take extra steps to correct the unexpected angle that it receives in place of the command angle.

[0005] Plunger mechanisms used in failsafe (default) mechanisms are typically made of all metal components which have high friction forces in operation and have the tendency to bind or jam. They also typically have large load differentials, that is the difference between the initial force to depress the plunger and the final force.

[0006] It would be desirable to have an electronic valve control system with an improved failsafe or limp-home mechanism and which minimizes the frictional forces in the default mechanism. It would also be desirable to have an ETC system which utilizes a plunger-type default mechanism which does not have the tendency to bind or jam and which has low friction forces.

[0007] The present invention provides an electronic throttle control assembly having a housing with a gear train and throttle valve mechanism. A throttle plate is positioned on a throttle shaft and the plate and shaft are positioned in the engine or air induction passageway, such that the throttle plate regulates airflow into the engine. A cover member enclosing the gear train contains a motor with a spur gear.

[0008] The operation of the throttle valve is accomplished through the gear train assembly which is driven by the motor. The motor is regulated by the electronic control unit of the vehicle which in turn is responsive to the input of the vehicle operator or driver. A throttle position sensor responsive to the rotation of the throttle shaft feeds back the position of the throttle plate to the electronic control unit.

[0009] In the operation of the throttle valve, a gear connected to the motor operates an intermediate gear (or idler gear), which in turn operates a sector gear which is connected to the throttle body shaft. The sector gear is biased by a spring member toward the closed position of the throttle valve. As a failsafe or default mechanism, a spring-biased plunger member is attached to the housing and positioned to interrupt operation of the sector gear in the event of an electronic failure and prevent the throttle valve from closing completely. At the default position, the vehicle can still be operated, although at a reduced capacity. This allows the driver to “limp-home.”

[0010] If the throttle valve is in its closed position when an electronic failure occurs, the spring-biased plunger member acts on the sector gear to open the throttle valve slightly to the failsafe position.

[0011] In order to minimize frictional forces in the plunger mechanism, the spring member and/or plunger member are configured to make as little contact with each other as possible. For this purpose, an “hour-glass” shaped spring member can be provided. Also, the plunger member can have a ribbed shape or a reduced outer periphery cross-section. It is also possible to make components of the default mechanism from a composite material which is impregnated with a lubricant, such as PTFE. By minimizing the sliding contact and friction between the plunger member and the spring member, the operation of the default mechanism is enhanced.

[0012] Other features and advantages of the present invention will become apparent from the following description of the invention, particularly when viewed in accordance with the accompanying drawings and appended claims.

[0013] FIG. 1 illustrates an electronic throttle control assembly in accordance with the present invention;

[0014] FIG. 2 illustrates the cover member of an electronic throttle control assembly with the gear train and throttle shaft attached thereto;

[0015] FIG. 3 is a top view of an electronic throttle control housing showing the gear mechanism;

[0016] FIG. 4 is an exploded side sectional view of the electronic throttle control mechanism of FIG. 1 showing many of the components thereof;

[0017] FIG. 5 depicts an intermediate or idler gear member which can be utilized with the present invention;

[0018] FIG. 6 illustrates a sector gear member which can be utilized with the present invention;

[0019] FIG. 7 illustrates an embodiment of a spring member which can be utilized with the present invention;

[0020] FIG. 8 illustrates a spring-biased plunger member which can be utilized with the present invention;

[0021] FIG. 9 illustrates an alternate embodiment of a spring-biased plunger member which can be utilized with the present invention;

[0022] FIG. 9A illustrates a cross-section of the plunger member shown in FIG. 9;

[0023] FIGS. 10, 11, 12 and 13 illustrate various positions of the sector gear and plunger mechanism during operation of the electronic throttle control assembly in accordance with the present invention;

[0024] FIG. 13A is an enlarged view showing the forces X and Y, points A, B and C, axis 95 and alignment line 101 more clearly; and

[0025] FIG. 14 is a schematic illustration showing a representative circuit which can be utilized with the present invention.

[0026] The drawings illustrate a preferred embodiment of an electronic throttle control assembly in accordance with the present invention. It is understood that other embodiments with alternate configurations and equivalent components and operations can be utilized in accordance with the present invention.

[0027] FIG. 1 is a perspective view of an electronic throttle control assembly or mechanism which is referred to generally by the reference numeral 10. The electronic throttle control assembly 10 (also known as an electronic throttle body) includes a housing or body member 12 and a cover member 14. The housing 12 includes a throttle valve section 16, a gear train section 18, and a throttle position sensor mechanism 28. The cover member includes a motor housing 26 and an electrical connector member 30.

[0028] The throttle valve section 16 includes an air flow passageway 32 in which a valve plate 34 is positioned to regulate the flow of air therethrough. The throttle plate 34 is attached to a throttle shaft 36 which is positioned transverse to the axis of the airflow passageway 32. The throttle shaft is positioned in the housing 12 in any conventional manner and preferably is supported by a pair of bearings 23 (one of which is shown in FIG. 4) which allow it to turn freely to regulate the airflow to the engine.

[0029] A gear train or mechanism 40 is positioned in the gear train section 18 of the housing member 12. The gear train 40 generally consists of an intermediate or idler gear member 42 and a sector gear member 44. The sector gear 44 is fixedly attached to the upper end 37 of the throttle shaft 36 such that the throttle shaft and throttle plate rotate along with the sector gear.

[0030] A motor 50 is positioned in the motor housing 26 and attached to the cover member 14. The motor 50 is preferably a reversible 13-volt DC motor and is connected to a mounting plate 51 which is secured to the cover member 14 by a plurality of fasteners 49. The motor 50 has a shaft 52 on which a small spur gear 54 is positioned. The gear 54 has a plurality of teeth 56 which mesh with and rotate the gear train. The idler gear member 42 is mounted on a shaft 58 which is positioned in the housing 12 or cover member 14, or both. The idler gear rotates freely on the shaft 58. As shown in FIG. 5, the intermediate or idler gear 42 includes a first gear member 60 with a plurality of teeth 62 and a second gear member 64 with a plurality of teeth 66. The gear teeth 66 are positioned to mesh with the gear teeth 56 on the motor driven gear 54, while the gear teeth 62 are positioned and adapted for mating with gear teeth 70 on the sector gear 44. As shown in the drawings, the teeth 70 on sector gear 44 are only provided on a portion or sector on the outer circumference of the gear member.

[0031] All of the gear members 54, 42 and 44 are preferably made of a plastic material, such as nylon, although they can be made of any other comparable material, such as a composite material, which has equivalent durability and function.

[0032] The sector gear 44 is preferably molded onto one end 37 of the throttle shaft 36. For this purpose, recesses or grooves are provided on the end 37 of the shaft in order to allow the sector gear to be integrally molded to the shaft and be permanently affixed to it.

[0033] A helical torsion spring member 80 is positioned in the gear train section 18 of the housing member 12. One embodiment of a spring member 80 which can be utilized with the present invention is shown in FIG. 7. The spring member 80 has one end 82 which is fixedly secured to the cover member 14 while the other end 84 of the spring member is positioned in opening 86 in the sector gear 44. In the embodiment illustrated in the drawings, the spring member 80 is positioned around the end 37 of the throttle shaft and between the sector gear 44 and the cover member 14 (see FIG. 3).

[0034] The spring-biased plunger mechanism which is preferably utilized with the present invention is shown in FIG. 8 and identified generally by the reference numeral 90. The plunger mechanism 90 has an elongated hollow body or housing 92 which is externally threaded to mate with threaded opening 94 in the gear train section 18 of the housing 12. A slideable plunger member 96 is positioned inside the body of the plunger mechanism 90 and is biased by a coil spring member 98 positioned inside the housing 92. A cap or plug member 100 holds the spring member and plunger member 96 in position. Threads 93 on the outer surface of the body 92 of the plunger mechanism 90 mate with corresponding threads in opening 94 in housing 12 so that the plunger mechanism can be adjusted to facilitate proper and optimum positioning and operation of the throttle valve and failsafe mechanism.

[0035] The spring-biased plunger mechanism 90, in combination with sector gear 44 and spring member 80, act together to limit and control the operation of the valve plate 34 in the failsafe or default mechanism. In this regard, the general operation of the gear assembly, sector gear, plunger member, and the other components are described in detail in the Applicant's co-pending patent application Ser. No. 09/438,122, filed on Nov. 11, 1999, and entitled Electronic Throttle Control System With Two-Spring Failsafe Mechanism, the disclosure which is hereby incorporated by reference herein.

[0036] The plunger mechanism 90 has a number of features which help to reduce friction and deter binding. The distal end 96B of the plunger member 96 is guided in channel 99 in the cap or plug member 100. This keeps the movement of the plunger member aligned with the axial or longitudinal axis 95 of the housing 92 and also minimizes friction and binding at point P where the exposed end 96A of the plunger member 96 is slidingly positioned. This alignment also allows the width “W” of flange or shoulder 97 to be reduced which in turn reduces the possible contact that it may have with the inside of the housing. Also, the spring member 98 has an “hourglass” shape, as shown in FIG. 8, which reduces the contact of the coils of the spring member with both the inner surface of the housing and the outer surface of the plunger member. Any buckling of the spring member 98 during operation of the plunger mechanism will only cause the center portion or coil 98C to make contact with the plunger member. The two outer ends 98A and 98B of the spring member are centered on shoulders of the flange 97 and the cap member 100.

[0037] The housing and cap member can also be made of a material with reduced friction, such as a composite material impregnated with PTFE lubrication. The plunger member 96 could be made of a similar material, depending on the application.

[0038] An alternate embodiment of a spring-biased plunger mechanism 200 which can be utilized with the present invention is shown in FIGS. 9 and 9A, with FIG. 9A being a cross-section of the plunger member 202. The plunger mechanism 200 has a body or housing member 204, a cap or end plug member 206, and a coil spring member 208. The outer surface 210 of the body is threaded as shown. In this embodiment, there is less available clearance for an hourglass-shaped spring member and thus a larger number of coils of the spring member 208 can make contact with the plunger member 202 during use. In order to minimize friction, the plunger member 202 has a plurality of elongated ribs 212 which extend longitudinally along a significant portion of the length thereof. In this manner, the spring coils only contact the outer edges of the radiused ribs instead of the entire diameter of the plunger member.

[0039] It is also possible to heat-stake, crimp, or otherwise securely fasten the cap member 206 to the body member 204. Once the plunger member is accurately positioned to provide the desired airflow past the throttle plate, the plunger mechanism is made tamperproof in this manner. If the cap is made of a metallic material, such as brass, it can be heated and then pressed into the housing which will melt the housing composite material and bond the cap in place. If the cap is made from a composite material, it can be securely fastened to the body member by ultrasonic welding or chemical bonding.

[0040] The operation of the electronic throttle valve assembly is shown generally by the schematic diagram set forth in FIG. 14. In general, the force applied to the accelerator pedal 110 by the operator of the vehicle 112 is read by a sensor 114 and conveyed to the electronic control unit (ECU) 116 of the vehicle. The accelerator pedal 110 is typically biased by a spring-type biasing member 118 in order to provide tactile feedback to the operator. The ECU 116 of the vehicle also receives input from a plurality of other sensors 120 connected to other mechanisms and systems in the vehicle.

[0041] In order to operate the throttle valve plate 34, a signal from the ECU 116 is sent to the motor 50. The motor rotates the spur gear 54 which then operates the gear train mechanism 40. More specifically, the spur gear member 54 rotates the intermediate or idler gear member 42 which, in turn, rotates the sector gear member 44. This, in turn, causes the throttle body shaft 36, which is fixedly attached to the sector gear member 44, to rotate. Rotation of the shaft 36 accurately positions the valve plate 34 in the passageway 32 and allows the requisite and necessary airflow into the engine in response to movement of the accelerator pedal 110.

[0042] The cover member 14 can be attached to the body or housing member 12 in any conventional manner, but preferably is connected by a plurality of fastener members, such as screws or bolts. Also, an appropriate gasket or sealing member (not shown) can be positioned between the cover member and the housing in order to protect the gear train 40 and other components from dirt, moisture, and other environment conditions. When the electronic throttle control assembly 10 is utilized, it is positioned in the engine compartment of the vehicle and bolted or otherwise securely fastened to the vehicle. For this purpose, a plurality of openings can be provided in the housing, such as openings 13 shown in FIG. 1.

[0043] The throttle position sensor (TPS) 28 is secured to the housing 12. The TPS is of conventional design and has a rotor which is attached to the lower end 39 of the throttle shaft 36. The TPS 28, together with related electronics, reads or “senses” the position of the throttle valve 34 and transmits it to the ECU 116 of the vehicle. An electrical connector 31 connects the TPS to the ECU. The connector member 31 preferably has four contacts and, through the ECU regulates the actions of the motor 50 and thus the position of the throttle valve.

[0044] Connector 30 on the cover member 14 connects the motor 50 to the ECU. Opening 33 in the cover member allows access to the upper end 37 of the throttle shaft during assembly of the throttle valve assembly and orientation/calibration of the throttle shaft and throttle valve.

[0045] Preferably, the cover member 14 is made from a plastic composite material, such as fiberglass filled polyphenyl sulfide (PPS) or polyetherimide (PEI). In order to reinforce the cover member, a metal plate member (not shown) can be molded into the cover when it is manufactured. The metal plate stiffens the cover member, holds the motor securely in position, and can maintain the center-to-center spacing of the gear members and shaft members. Also, preferably the various components of the electronic throttle valve assembly 10 are packaged and positioned in the manner shown in FIGS. 1-4 for ease of positioning and use in the vehicle, although other configurations are possible. For example, TPS can be positioned on the cover member 14 and be connected to the upper end of the throttle shaft, and the connector 30 can include the electrical connections for both the motor and the TPS.

[0046] The housing member 12 can be made of a metal material, such as aluminum, or it can also be made of a plastic composite material. Also, preferably the cover member motor, gear train, spring member, throttle shaft and gear shaft 58 are preassembled into a modular subassembly before they are mated with the housing.

[0047] When the electronic throttle control mechanism 10 is assembled, the spring member 80 biases the valve plate member 34 towards its closed position. In this regard, in many engines known today, the throttle plate is manufactured and assembled to have a slight inclination on the order of 7°-10° in the fully closed position. This is to assure proper functioning of the valve plate in all conditions and prevent it from sticking or binding in the closed position. In this regard, typically the airflow passageway 32 has a circular cross-sectional shape and configuration, while the throttle plate member 34 has a slightly elliptical shape.

[0048] Due to the bias of spring member 80 on the sector gear 44 and thus valve plate member 34, the spring member 80 acts to return the throttle plate 34 to or toward the closed position in the event of an electronic failure of the electronic throttle control mechanism 10 or the vehicle itself. In this regard, the throttle plate member 34 and sector gear 44 can be rotated by the motor 50 and gear train mechanism 40 to the fully open position of the throttle plate 34. In the open position, the throttle plate member 34 is positioned approximately parallel to the axis of the air flow passageway 32 thus allowing a full complement of air to pass into the engine. FIG. 10 illustrates the position of the sector gear and plunger mechanism when the throttle valve member 34 is in its wide open position. Stop member 19 in the housing 18 limits the throttle valve from opening past the fully open position.

[0049] The plunger mechanisms 90 and 200 act as failsafe or default mechanisms which prevent the throttle valve from closing completely in the event of an electronic failure. The plunger mechanisms act to position the throttle valve plate 34 in a slightly open position, thus allowing the vehicle to operate at a reduced speed and “limp-home.” In this regard, since throttle plate assemblies in engines known today have a slight inclination on the order of 7°-10° in the fully closed position, the default or “limp-home” position of the throttle plate in these engines is about 12°-20° from a position transverse to the axis of the airflow passageway.

[0050] The plunger mechanisms 90 and 200 are positioned in their respective housings such that the spring biased plunger members 96 and 202 contact shoulder member or surface 45 on the sector gear 44. The plunger mechanisms are positioned such that the shoulder 45 contacts the plunger member before the throttle plate 34 reaches the fully closed position. The force or bias of the spring members 98 and 208 in the plunger mechanisms 90 and 200, respectively, are stronger or greater than the force or bias of the helical torsion spring member 80, and thus the plunger mechanisms stop and prevent the sector gear 44 from rotating any further. The position of the sector gear and plunger mechanism at this point of operation is shown in FIG. 12.

[0051] In order to overcome the force of the spring members 98 and 208 and allow the throttle plate member 34 to be moved to its fully closed position, the motor 50 is operated. The motor, through the gear train mechanism 40, turns or rotates the sector gear 44 which, in turn, rotates the throttle shaft and closes the valve plate member 34. The motor forces the stop shoulder 45 against the plunger members and moves the plunger members to a depressed position against the force of the spring members. FIG. 11 illustrates the position of the components when the throttle valve member is in its closed position.

[0052] In the event of an electronic failure in a throttle control assembly 10 when the throttle plate member is closed or almost closed, the failsafe mechanism will automatically act to open the throttle plate to the default or “limp-home” position. The force of the spring biasing member 98 and 208 on the plunger members 96 and 202 will return the plunger members to their undepressed positions, thus forcing the sector gear member 44 (and throttle shaft member 36) to rotate slightly and open the throttle valve member 34 (see FIG. 12). With the use of two spring members 80 and 98 or 208, the throttle shaft member 36 (and thus the throttle valve plate member 34) is biased in all directions of operation of the throttle control valve system toward the default or limp-home position.

[0053] By strategically selecting the geometry of the position of the sector gear 44 and plunger mechanism 90, wear, friction and stresses in the gear train mechanism 40 can also be minimized. The reduction of stresses and concentration of forces reduces deflection of the gear members which increases the durability and useful use of the electronic throttle control assembly 10.

[0054] Whenever the stop shoulder 45 of the sector gear 44 and the plunger member 96 of the plunger mechanism 90 are in contact, as shown in FIGS. 11-13A, a force X is applied to the stop shoulder surface 45 of the sector gear. In addition, the torsion spring member 80 exerts a force Y on the sector gear 44 in the direction opposite to the force of the plunger member. These forces are shown in FIG. 13A.

[0055] The forces X and Y are strategically applied to the sector gear and plunger member such that stresses and normal forces in the sector gear are significantly reduced. In this regard, point A, which is the point of contact between the plunger member 96 and stop shoulder 45 of the sector gear, point B, which is the point of contact of the end 84 of the spring member 80 in the opening 86 on of the sector gear, and point C, which is the center of rotation or axis of the sector gear 44, are in alignment. Preferably, points A, B and C are aligned along a line 101 which is perpendicular to the longitudinal axis 95 of the plunger mechanism 90 when the plunger member 96 is approximately midway in the default range of travel of the sector gear and plunger member 96 (see FIG. 13A). As shown in the drawings, this means that the sector gear 44 and plunger member 96 are in the position shown in FIG. 13 which is midway between the positions of the sector gear and plunger members shown in FIGS. 11 and 12. Having these surfaces perpendicular midway through the default range of travel instead of at either end of the travel range minimizes the sliding contact and friction between the plunger member 96 and sector gear surface 45. This reduces friction in the operation of the electronic throttle control assembly 10 and enhances its performance.

[0056] While the invention has been described in connection with one or more embodiments, it is to be understood that the specific mechanisms and techniques which have been described are merely illustrative of the principles of the invention. Numerous modifications may be made to the methods and apparatus described without departing from the spirit and scope of the invention as defined by the appended claims.