Split linkage mechanism for valve assembly

A linkage mechanism for a valve assembly includes one of a slot and an engagement component operably coupled to at least one drive component and located eccentrically from a rotational axis of the at least one drive component, a link operably coupled to one end of a valve stem of a valve member and being moveable with the valve stem, the link having another one of a slot and an engagement component, and a rotatable lever coupled to at least one housing, the lever including one of a first slot and a first engagement component operably engaged with the one of the slot and the engagement component of the at least one drive component and one of a second slot and a second engagement component operably engaged with the one of the slot and the engagement component of the link, wherein rotation of the at least one drive component causes the lever to rotate to convert a rotational movement of the at least one drive component to a linear movement of the link such that the link, the valve stem, and the valve member are moved axially in a direction along a longitudinal axis of the valve stem.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates generally to valves such as an air throttle valve, exhaust gas recirculation (EGR) valve, exhaust throttle valve, bypass valve, turbo waste gate valve, or recirculation valve used for vehicles and, more specifically, to a linkage mechanism for a valve assembly used in a vehicle that may afford improved performance over a range of operation of the valve assembly.

2. Description of the Related Art

Control of vehicle engine exhaust emissions and meeting fuel economy standards are mandatory requirements in most countries. Oxides of Nitrogen (NOx) and particulate matter are two components of the engine exhaust emissions that must be controlled.

Formation of NOx may occur at higher engine combustion temperatures and particulates may form at lower combustion temperatures. A system, referred to as an exhaust gas recirculation (EGR) system, has been developed to control combustion temperatures, NOx, and particulate emissions. In a typical EGR system, a portion of the exhaust gas is recirculated back to an intake manifold where it may be combined with incoming air and fuel. The exhaust gas portion of the mixture may not support combustion and, when this mixture is compressed and ignited in a cylinder of the engine, the exhaust gas may control the combustion temperature and limit the formation of NOx and particulate in the exhaust emissions.

The EGR system typically includes an EGR valve assembly having a valve and an actuator for actuation of the valve. The type of actuator and valve may be determined, in part, by the type of engine and EGR system used for emission controls or fuel economy. For example, the exhaust gas from a diesel engine may contain high amounts of residue that can form a sticky lacquer like substance that may provide resistance to opening of the valve. A higher force actuator, in excess of 300N, may be required to open the valve. D.C. motor actuators with multi-stage drives have been used for actuation of the valve in these EGR valve assemblies.

In another example, the exhaust gas from a gasoline engine may contain a lesser degree of residue due, in part, to the higher exhaust temperatures and chemical reaction during combustion. The operating force of the actuator may be substantially less for these engines. Linear solenoid actuators have been used for actuation of the valve in some of these EGR valve assemblies and their typical operating forces may range from 20N to 2N between the open and closed valve positions.

Advances in engine technology such as high pressure turbocharging may place increasing demands on valve capabilities. Not only must valves withstand these higher pressures, they also must remain closed in the event of an electrical failure. Contemporary EGR valve assemblies typically include a valve, for example a poppet valve, that is electrically operated, usually by a DC motor, a gear train, and a final linkage mechanism. Some EGR valve assemblies may incorporate a valve seat in a mating component that positions the valve downstream of the seat. The actuator must then “pull” the valve to open. Since the pneumatic force of the exhaust gas is now in the direction of opening of the valve, the actuator of the EGR valve assembly must be able to resist this force, especially in the case of an electrical failure. Therefore, it is desireable that the actuator of the valve for the EGR valve assembly be able to accommodate the inevitable tolerance stackup of the seat position relative to the valve.

A popular rotary-to-linear linkage mechanism is a scotch yoke, which is an eccentric pin (or ball bearing) and a horizontal slot. The output is simple harmonic motion (SHM). This has the desirable characteristic of a low lift-to-angle slope at the valve closed and low opening region. The eccentric position at the closed valve (“initial position”) must be some angle from the limiting position to seat the valve. This low starting angle achieves good low flow resolution, high opening force, and good anti-backdrive capability. If this starting angle is too low, the slope approaches zero at the limiting position of the eccentric. This means the linkage mechanism is incapable of accommodating any significant tolerance stackup, especially if the valve seat is in a mating part, and the valve will fail to reach the seat. Conversely, if the starting angle is too high, the anti-backdrive feature will be diminished, and the valve may be subject to blowing open at high delta pressures. A workable design to accommodate these issues would need an increased performance margin. This translates to a larger motor, return spring, package size, and cost. Thus, there is a need in the art to provide a linkage mechanism for actuating a valve in a valve assembly that overcomes these issues.

SUMMARY OF THE INVENTION

The present invention provides a linkage mechanism for a valve assembly including one of a slot and an engagement component operably coupled to at least one drive component of the valve assembly and located eccentrically from a rotational axis of the at least one drive component. The linkage mechanism also includes a link operably coupled to one end of a valve stem of a valve member of the valve assembly and being moveable with the valve stem, the link having another one of a slot and an engagement component. The linkage mechanism further includes a rotatable lever coupled to at least one housing of the valve assembly. The lever includes one of a first slot and a first engagement component operably engaged with the one of the slot and the engagement component of the at least one drive component and one of a second slot and a second engagement component operably engaged with the one of the slot and the engagement component of the link. Rotation of the at least one drive component causes the lever to rotate to convert a rotational movement of the at least one drive component to a linear movement of the link such that the link, the valve stem, and the valve member are moved axially in a direction along a longitudinal axis of the valve stem.

One advantage of the present invention is that a new linkage mechanism is provided for a valve assembly used in a vehicle. Another advantage of the present invention is that the linkage mechanism is used to pull a valve member of the valve assembly open. Yet another advantage of the present invention is that the linkage mechanism includes a lever combined with a scotch yoke to create a linear range of motion of an initial opening region of travel of the valve member. Still another advantage of the present invention is that the linkage mechanism may be capable of providing desired characteristics of good low flow resolution, high opening force, and good anti-backdrive capability over a range of valve lift while being tolerant to components and manufacturing processes. A further advantage of the present invention is that the linkage mechanism may avoid undesirable characteristics that may include a high pressure angle that may increase side loading of valve components of the valve assembly.

Other objects, features, and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description taken in connection with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures, where like numerals are used to designate like structure unless otherwise indicated, one embodiment of an EGR system10is shown inFIG. 1for a vehicle (not shown). The vehicle includes an engine11. In one embodiment, the engine11is a conventional internal combustion engine known in the art. The engine11has an intake manifold12and an exhaust manifold13. The EGR system10is used to control combustion temperatures, and control Nox and particulate emissions from the engine11. It should be appreciated that the engine could be of any suitable type to drive the vehicle, without departing from the scope of the present invention.

As illustrated inFIG. 1, the EGR system10may include an exhaust gas recirculation (EGR) valve14that may control the flow of exhaust gas to the intake manifold12and an EGR cooler15to reduce a temperature of the exhaust gas entering the intake manifold12. The EGR system10also may include one or more conduits16,17,18,19and20to provide an interconnection between the exhaust manifold13, EGR cooler15, EGR valve14, and the intake manifold12. In one embodiment, the EGR valve14may be of an electrically controlled type. The EGR system10may further include an electronic control unit (ECU)21to provide a signal that will control an opening/closing of the EGR valve14. The EGR system10may also include a throttle valve such as air throttle22to control airflow into the intake manifold13. It should be appreciated that, as the EGR valve14opens and closes, the EGR valve14may increase or decrease the flow rate of exhaust gas to the intake manifold12. It should also be appreciated that the required EGR flow rate may be dependent upon several factors that may include the displacement of the engine11and a pressure differential between an exhaust and intake system.

In operation of the EGR system10, the ECU21may be programmed with a map of engine operating conditions and a desired EGR flow rate for each condition. The EGR valve14may have a position sensor (not shown) that may be connected to the ECU21and provide an output signal that is relative to the valve position and flow rate through the EGR valve14. The desired flow is translated to a position sensor output signal and an actuator control signal. The control signal may be applied to an actuator for the EGR valve14, which may cause the EGR valve14to open and allow exhaust gas to flow from the exhaust manifold13to the intake manifold12. The position sensor and its output signal may be part of a closed loop control system for the EGR valve14. The position sensor will provide feedback to the ECU21that may indicate if the EGR valve14has achieved the desired position and related flow. The ECU21may adjust the actuator control signal to achieve-or-maintain the desired position of the EGR valve14. The recirculated exhaust gas may mix with the incoming air and be distributed to cylinders of the engine11by the intake manifold12. The mixture of exhaust gas, air, and fuel may determine the combustion temperature and control of the level of NOX and particulate matter. It should be appreciated that fuel economy may also be improved by the use of the EGR system10. It should also be appreciated that, when the EGR valve14opens, the vacuum or pressure in the intake manifold12and the exhaust manifold13may be reduced and the reduction of vacuum or pressure may reduce the pumping losses of the engine11and the amount of fuel used by the engine11.

In the EGR system10ofFIG. 1, a number of electrically controlled devices such as a linear solenoid, a brush D. C. motor, a brushless D.C. motor, a torque motor, a stepper motor, a pneumatically operated device, or a hydraulically operated device, may be used in the actuator of the EGR valve14. Valve position sensing can also be achieved by alternate methods such as counting steps of a stepper motor or by regulating fluid flow to a pneumatically or hydraulically operated EGR valve14. It should be appreciated that a number of valve types such as throttle, poppet, or flap may be used to control the flow exhaust gas.

Referring toFIGS. 2, 3, and 4, a conventional EGR valve assembly100is shown for use with the EGR system10. The EGR valve assembly100may include a valve housing101, a gear housing102, and a motor housing103. The EGR valve assembly100may also include a D.C. motor106disposed within the motor housing103and retained by a cover104. The EGR valve assembly100may include electrical connections to the D.C. motor106and other electrical components, such as a position sensor (not shown), which may be made by a lead frame (not shown). The lead frame may be operably connected to the motor housing103or embedded within motor housing103. The motor housing103may be made using a variety of processes including injection molding. The EGR valve assembly100may include an electrical connector107integrally formed as part of the motor housing103to make an external connection with other vehicle components such as the ECU21. The EGR valve assembly100may include a rotatable shaft109operably connected to and forcibly rotated by the D.C. motor106in response to an electrical control signal from the ECU21.

The EGR valve assembly100may include a gear drive assembly110to translate the rotatable force of the rotatable shaft109and may also increase the force made available by the D.C. motor106. The gear drive assembly110may include at least one drive gear111operably connected to the rotatable shaft109. The gear drive assembly110may also include a number of driven gears including an output gear112. The output gear112may be operably connected to an output shaft113that may be supported within the gear housing102. The gear drive assembly110may include a bushing114and a bearing115to support the output shaft113in the gear housing102and may provide for efficient rotation of the output shaft113. It should be appreciated that the number of driven gears may be limited to only the output gear112and, for that embodiment, the output gear112would engage with and be directly rotated by the drive gear111. It should also be appreciated that it may be desirable to provide more than one driven gear.

For an embodiment having more than one driven gear, the gear drive assembly110may include a second driven gear144, also referred to as an intermediate gear144, to engage both the drive gear111and the gear112, also referred to as the output gear112. The intermediate gear144may be supported in the gear housing102by a pin116that may provide for rotation of the intermediate gear144. The rotational force of the D.C. motor106may be translated from the drive gear111to the two driven gears144,112and to the output shaft113. The selection of the number driven gears may be determined by a number of factors that may include the desired rotational force and the desired rotational speed to operate the EGR valve assembly100. It should be appreciated that the gear housing102may be attached to the motor housing103by a suitable mechanism such as threaded fasteners, rivets, or a clinch ring117.

The valve housing101may include an inlet118for receiving a fluid flow and an outlet119for delivering the fluid flow. The valve housing101may include a valve seat120disposed within the valve housing101and secured by a suitable mechanism such as staking or casting in position.

The EGR valve assembly100may include a moveable valve or valve member, also referred to as a poppet valve121, disposed in the valve housing101and coaxial with the valve seat120for controlling the fluid flow between the inlet118and the outlet119. The poppet valve121may be fully closed and seated on the valve seat120and essentially block fluid flow between the inlet118and outlet119. The poppet valve121may move axially away from valve seat120to a fully open position where maximum flow may occur between the inlet118and outlet119. The poppet valve121may also move axially away from the valve seat120to a number of intermediate positions between the fully closed and fully open positions to control a rate of fluid flow at values that are less than a maximum fluid flow rate. The inlet118may be operably connected to an exhaust manifold13of the engine11and exhaust gas, indicated by the arrow146, may flow into the inlet118. The outlet119may be operably connected to an intake manifold12of the engine11and the exhaust gas146flowing past the valve seat120and the poppet valve121may flow through the outlet119and into the intake manifold12.

The EGR valve assembly100may include a valve stem122disposed within the valve housing101and may be coaxial with the poppet valve121and the valve seat120. The valve stem122may have a first end123that may be connected to a central location of the poppet valve121. The poppet valve121may be attached to the valve stem122by a suitable mechanism such as welding, riveting, or staking. The valve stem122may be guided and supported by a bushing124that may be coaxial with the valve stem122and disposed within the valve housing101. It should be appreciated that the bushing124may allow axial movement of the valve stem122and the poppet valve121along its longitudinal axis133.

The motion of the output shaft113is rotary and the movement of the valve stem122is linear and therefore there is a need for a linkage that may convert the rotary motion of the output shaft113to axial movement of the valve stem122and the poppet valve121. A common linkage that may provide the conversion of motion is known as a scotch yoke. The scotch yoke may include a slot formed in one moving member and an engagement component located in another moving member.

Referring toFIGS. 3 and 4, the EGR valve assembly100may include a lever125operably connected and rotatable with the output shaft113. The EGR valve assembly100may include an engagement component126operably connected to and moveable with the lever125. The engagement component126may be a ball bearing that may be attached to the lever125by a pin127.FIG. 4is a partially exploded view with some valve components displaced to provide a view of the engagement component126and the pin127. The engagement component126may also be a pin, a sleeve, a roller, a roller bearing, or other suitable engagement component. The engagement component126may be eccentrically positioned from the longitudinal axis132of the output shaft113.FIG. 5is an enlarged view shown in the direction of arrow148ofFIG. 4and shows the axis149of the engagement component126eccentrically located from the longitudinal axis132of the output shaft113. It should be appreciated that the end of the output shaft113is somewhat rectangular in shape. It should also be appreciated that this portion of the output shaft113may engage a similar rectangular geometry in the lever125and provide a “keying” feature that may orient the lever125and the engagement component126. It should further be appreciated that this may also prevent undesirable rotation of the lever125when the output gear112is held in a stationary position.

Referring again toFIGS. 3 and 4, the EGR valve assembly100may include a yoke128operably connected to a second end129of the valve stem122and moveable with the valve stem122. The yoke128may include a horizontal slot130for receiving the engagement component126. When the output shaft113and the lever125are rotated, this rotation may cause the engagement component126to bear on a horizontal surface of the slot130and forcibly move the yoke128. This movement may be described as a simple harmonic motion (SMH) that may cause the yoke128, valve stem122, and poppet valve121to move along the longitudinal axis133of the valve stem122in a valve opening direction140or a valve closing direction139(FIG. 6).

Referring toFIG. 6, the EGR valve assembly100may include a return spring138coaxially located with the output shaft113and may be operably connected to the output gear112and the gear housing102. The return spring138may provide a bias force that will forcibly rotate the output gear112, output shaft113, lever125, and engagement component126, thereby causing the yoke128, the valve stem122, and the poppet valve121to move in the valve closing direction139. The bias force of the return spring138must be overcome by the force provided by the D.C. motor106and the gear drive assembly110before the poppet valve121may move in the valve opening direction140. It should be appreciated that it may be advantageous to minimize an initial bias force of the return spring138to avoid increasing the force capability of the D.C. motor106and the gear drive assembly110. It should be appreciated that the EGR valve assembly100, shown inFIG. 2, may function in a similar manner to the EGR valve14shown inFIG. 1and previously described herein, for the EGR system10.

The EGR valve assembly100shown inFIG. 2includes the valve seat120, poppet valve121, and valve stem122. However, it may also be desirable for some EGR valve assemblies and some applications to have the valve seat120and at least the inlet118located in a separate housing detached from valve housing101. In one embodiment, the separate housing may also be a portion of another product such as an intake manifold assembly as disclosed in U.S. Pat. No. 7,204,240, the disclosure of which is expressly incorporated herein by reference. In another embodiment, the separate housing may be a portion of a component or product such as an exhaust manifold, a turbocharger, an EGR cooler, another valve, or an integrated module combining one or more components or products.

Referring toFIG. 7, another embodiment of the EGR assembly100for the EGR system10is shown. Like parts of the EGR valve assembly100have like reference numerals increased by a lower case letter “a”. In this embodiment, the EGR assembly100ais shown with a modified housing101awherein the lower portion containing the inlet118, the outlet119, and the valve seat120has been removed. As illustrated inFIGS. 7 and 8, the EGR assembly100aincludes a housing101aand a separate housing141. Similar reference numerals are used to identify similar components followed by a lower case letter “a”.FIG. 7is a partially exploded view to show the assembly of some components. The separate housing141may include a valve seat120a, an inlet118aand an outlet119a. The valve housing101aand the separate housing141may be attached together by a suitable mechanism such as one or more threaded fasteners150, rivets, or a clinch ring.FIG. 8shows the separate housing141fastened to the valve housing101a. A section of the separate housing141has been remove to show the poppet valve121aseated on the valve seat120a. It should be appreciated that the addition of the separate housing141and relocation of the valve seat120amay be advantageous for assembly or packaging, however, it may also require an increase in mechanical tolerance to ensure that the poppet valve121amay be seated in the correct position on the valve seat120a.

Referring toFIGS. 9A and 9B, a harmonic motion of the scotch yoke may provide limits of travel for the yoke128, valve stem122, and poppet valve121,121aalong the longitudinal axis133of the valve stem122. A first and second limit of travel135,136may occur when the lever125and engagement component126are rotated by the output gear112through a range of approximately 180 degrees and may define the maximum range of movement142of the poppet valve121,121afrom the valve seat120,120aas illustrated inFIGS. 9A and 9B. The angle of rotation is referenced to the longitudinal axis133of the valve stem122.FIG. 9Amay show the first limit of travel135which may occur at the valve closed position, andFIG. 9Bmay show the second limit of travel136which may occur as the poppet valve121,121ais at its maximum axial lift from the valve seat120,120a.

Referring toFIG. 10, a chart illustrates a typical lift of the poppet valve121,121aversus an angle of rotation137(FIG. 9B) of the eccentrically positioned engagement component126. For this embodiment and chart, the angle of rotation137may be lowest when the poppet valve121,121ais seated on the valve seat120,120aand the angle of rotation137may be highest when the poppet valve121,121ais at its maximum axial lift from the valve seat120,120a. As illustrated inFIG. 10, it should be appreciated that a negative angle of rotation beyond zero degrees may cause the yoke128, valve stem122, and poppet valve121,121ato reverse direction and move in the opening direction140and increasing the angle of rotation greater than approximately 180 degrees may cause the yoke128, valve stem122, and poppet valve121,121ato reverse direction and move in the closing direction139.

The initial valve lift-to-angle slope of the poppet valve121,121aafforded by the scotch yoke may be low and therefore it may provide good flow resolution, high operating force, and good anti-backdrive capability. The anti-backdrive capability may prevent the poppet valve121,121afrom opening if there is high backpressure acting on the poppet valve121,121a. This may be especially important when there is no electrical control signal applied to the EGR valve assembly100,100a. However as previously stated, as the angle of rotation moves towards zero, the first limit of travel135is approached and a negative angle of rotation may cause the poppet valve121,121ato unseat from the valve seat120,120a. It may therefore be practical to have an initial angle greater than zero to ensure the poppet valve121,121amay always seat on the valve seat120,120aand allow for the mechanical tolerances required for components and manufacturing processes that may cause variation in the position of the poppet valve121,121aand the valve seat120,120a.

FIG. 11shows an enlarged section of the chart ofFIG. 10. An initial angle of approximately twenty (20) degrees may allow for a variation of approximately 0.25 mm in the position of the poppet valve121,121aand the valve seat120,120a, but the lift-to-angle slope at the initial angle of twenty (20) degrees has increased and may substantially diminish the flow resolution, operating force, and anti-back drive capability. It should be appreciated that one workable solution may be a larger motor, higher force return spring, larger package size, and higher cost, however, these solutions may not be desirable and may not improve all characteristics. It should also be appreciated that, if the lower lift-to-angle slope could somehow be maintained as the eccentric engagement component126rotates over a greater angular range, this would afford the desired characteristics (good low flow resolution, high opening force, and good anti-backdrive capability) and accommodate the positional variation of the poppet valve121,120aand the valve seat120,120a.

Another workable solution, illustrated inFIG. 12, may be to modify a profile of the yoke slot130from a horizontal slot to an appropriate cam profile152which will meet the desired motion profile. Unfortunately, this modification can introduce a pressure angle143to the yoke128at a point151at which the engagement component126may contact the cam profile152. The pressure angle143may be up to approximately twenty-six (26) degrees and may result in a force in the direction of arrow153which may be perpendicular to the pressure angle143. It should be appreciated that this may cause a side load which may increase friction and wear of the valve stem122and bushing124and may prevent uniform seating of the poppet valve121,121aon the valve seat120,120a.

Referring toFIGS. 13 and 14, one embodiment of an EGR valve assembly200, according to the present invention, is shown for use with the EGR system10inFIG. 1. As illustrated inFIG. 13, the EGR valve assembly200may include a first housing201and a motor housing202. The first housing201may be attached to the motor housing202by a suitable mechanism such as threaded fasteners, rivets, or a clinch ring248. As illustrated inFIG. 14, the EGR valve assembly200may include a D.C. motor203that may be disposed within the motor housing202and retained by a cover204. The D.C. motor203may provide a rotational force that will actuate a valve of the EGR valve assembly200. It should be appreciated that, as previously stated, other types actuators may be used for actuation and they may include, brush D.C. motors, brushless D.C. motors, stepper motors, torque motors, pneumatic actuators, and hydraulic actuators.

Electrical connections to the D.C. motor203and other electrical components, such as a position sensor (not shown), may be made by a lead frame (not shown). The lead frame may be operably connected to the motor housing202or may be embedded within the motor housing202. The motor housing202may be made using a variety of processes including injection molding. An electrical connector205, may be integrally formed as part of the motor housing202to make an external connection with other vehicle components such as the ECU21. A rotatable shaft207may be operably connected to and forcibly rotated by the D.C. motor203in response to an electrical control signal from the ECU21.

Referring toFIGS. 15 and 16, the EGR valve assembly200may be similar to the EGR valve assembly100ain that it may have a separate housing208which may have an inlet209for receiving a fluid flow and an outlet210for delivering fluid flow. A valve seat211may be disposed within the separate housing208and secured by staking, casting in position, or other suitable mechanism. The separate housing208may also be a portion of another component or product as previously stated herein. The first housing201and the separate housing208may be attached by one or more threaded fasteners225, rivets, a clinch ring, or other suitable methods. The inlet209may be operably connected to the exhaust manifold13of the engine11and the exhaust gas, indicated by the arrow246, may flow into the inlet209. The outlet210may be operably connected to the intake manifold12of the engine11and the exhaust gas246flowing past the valve seat211may flow through the outlet210and into the intake manifold12.

The EGR valve assembly200also includes a moveable valve or valve member, also referred to as a poppet valve218, which may be coaxial with the valve seat211for controlling the fluid flow between the inlet209and the outlet210. The poppet valve218may be in a fully closed position and seated on the valve seat211and essentially block fluid flow between the inlet209and the outlet210. The poppet valve218may move axially away from the valve seat211to a fully open position where maximum fluid flow may occur between the inlet209and the outlet210. It should be appreciated that the poppet valve218may also move axially away from the valve seat211to a number of intermediate positions between the fully closed and fully open positions to control the rate of fluid flow at values that are less than the maximum fluid flow rate.

The EGR assembly200further includes a valve stem219that may be at least partially located in both of the first housing201and the separate housing208and may be coaxial with the poppet valve218and the valve seat211. The valve stem219has a first end220that may be connected to a central location of the poppet valve218. The poppet valve218may be attached to the valve stem219by welding, riveting, staking, or other suitable mechanisms. The valve stem219may be guided and supported by a bushing243as illustrated inFIG. 17. The bushing243may be coaxial with the valve stem219and may be disposed within the first housing201. It should be appreciated that the bushing243may allow axial movement of the valve stem219and the poppet valve218along its longitudinal axis221.

Referring toFIGS. 17, 18A18B, and19, the EGR valve assembly200also includes a gear drive assembly212that may be used to translate the rotational force delivered by the rotatable shaft207and may also increase the rotational force made available by the D.C. motor203. The gear drive assembly212, which may include the rotatable shaft207, may also include at least one drive gear213operably coupled or connected to the rotatable shaft207. The gear drive assembly212may also include a number of driven gears including an output gear214. The output gear214may be operably coupled or connected to a second shaft, also referred to as an output shaft215, which may be supported within the first housing201for providing efficient rotation of either or both the output gear214and the output shaft215. It should be appreciated that the number of driven gears may be limited to only the output gear214and, for that embodiment, the output gear214engages with and is directly rotated by the drive gear213.

As illustrated inFIGS. 17-19, the gear drive assembly212may include a first driven gear216and a second driven gear217that may engage the drive gear213and a third driven gear, such as the output gear214. The first and second driven gears216,217may also be referred to as intermediate gears216,217. The intermediate gears216,217may be supported in the first housing201by gear pins228and229that may provide for rotation of the intermediate gears216,217. In one embodiment, the drive and driven gears213,214,216,217are of a variety known as spur gears and each gear may have at least one section of gear teeth spread along their circumference. In one embodiment, the two intermediate gears216,217may be compound gears, each having two gear teeth sections spaced apart on circumferential sections. The first intermediate gear216may be in operable engagement with the drive gear213and the second intermediate gear217and the second intermediate gear217may be in operable engagement with the first intermediate gear216and the output gear214.

The rotational force of the D.C. motor203may be translated from the drive gear213to the three driven gears216,217, and214. The output gear214may translate the rotational force to the output shaft215if the output shaft215is operably connected to and rotatable with the output gear214. It should be appreciated that the selection of the number driven gears may be determined by a number of factors that may include the desired rotational force and the desired rotational speed to operate the EGR valve assembly200.

The EGR assembly200may also provide a rotary motion or rotational movement from the output gear214that must be translated to provide a linear movement of the valve stem219. However a linkage mechanism may be required that may have a greater tolerance to the positional variation of the poppet valve218, the valve stem219, and the valve seat211that may be increased with use of the separate housing208. It should be appreciated that the linkage mechanism must also provide the desirable characteristics of good low flow resolution, high opening force, and good anti-backdrive capability while avoiding side loading of the valve stem219that may cause excessive wear.

Referring again toFIGS. 17, 18A, 18B, 19, and 20, the EGR assembly200may include a linkage assembly or mechanism222, according to one embodiment of the present invention, for actuation of a valve such as the poppet valve218. The linkage mechanism222may include an engagement component223that may be operably coupled or connected to the output gear214by a hub portion224. The hub portion224may be formed as a portion of the output shaft215, as illustrated inFIGS. 18A and 18B, may be a separate component operably connected to the output shaft215, or may be directly connected to the output gear214. The engagement component223may be at least one of a pin, a sleeve, a roller, a ball bearing, a roller bearing, or other suitable engagement component. In one embodiment, the engagement component223is a ball bearing which is eccentrically positioned from the longitudinal axis226of the output shaft215and the output gear214. The engagement component223may be supported on the hub portion224by a pin227. The engagement component223may be operably coupled or connected to the output gear214by a number of methods that may be within the scope of the present invention. These methods may include, but are not limited to, forming the engagement component223as a portion of the output gear214, attaching the engagement component223directly to the output gear214, attaching the engagement component223to another component that is operably connected to the output gear214. It should be appreciated that the other component may be a lever, a separate hub, or other suitable component that may be moveable with the output gear214.

The linkage mechanism222may further include a lever230which is coupled to the first housing201by a gear pin229which may also couple the intermediate gear217to the first housing201. The gear pin229may allow for rotation of the lever230about an axis249of the gear pin229. The lever230may include a slot231for receiving the engagement component223. It should be appreciated thatFIGS. 18A and 18Bshow a partially exploded view in which some components have been displaced to provide a better view of components of the linkage mechanism222. It should also be appreciated thatFIG. 20shows the linkage mechanism222with a link238made transparent to provide a better view of the engagement component223in the slot231of the lever230.

When the output gear214is forcibly rotated in a first direction232, the engagement component223may rotate about the axis226of the output gear214and the output shaft215. The rotary movement of the engagement component223is depicted by an arced line252which has arrows that may show the direction of movement. The forced rotation of the output gear214in the first direction232may cause the engagement component223to make contact with a surface of the slot231and may force the lever230to rotate in a first direction250about the axis249of the gear pin229and may force the lever230to move in a first direction233which may be parallel to the longitudinal axis221of the valve stem219. When the output gear214is forcibly rotated in a second direction234, the engagement component223may contact a surface of slot231and may force the lever230to rotate in a second direction251about the axis249of the gear pin229and may force the lever230to move in a second opposite direction235which is parallel to the longitudinal axis221of the valve stem219.

In one embodiment, the lever230may also include a second engagement component236that may be at least one of a pin, a sleeve, a roller, a ball bearing, a roller bearing or other suitable engagement component. The second engagement component236may be operably coupled or connected to the lever230and extend from a surface237of the lever230.

The linkage mechanism222may further include a link238which may be operably coupled or connected to a second end239of the valve stem219and may be moveable with the valve stem219. The link238may be a separate component or it may be formed as a portion of the second end239of the valve stem219. The link238may include a transverse or horizontal slot240for receiving the second engagement component236of the lever230. It should be appreciated that the linkage mechanism222may be used with other types of valves such as an air throttle valve, exhaust throttle valve, bypass valve, turbo waste gate valve, or recirculation valve without departing from the scope of the present invention.

In operation of the linkage mechanism222, when the output gear214is forcibly rotated in the first direction232forcing the lever230to move in the first direction233, the second engagement component236may contact a surface of the horizontal slot240of the link238and may force movement of the link238, the valve stem219, and the poppet valve218in the first direction233, which may unseat the poppet valve218from the valve seat211and allow fluid flow between the inlet209and the outlet210. When the output gear214is forcibly rotated in the second direction234, forcing the lever230to move in the second direction235, the second engagement component236may contact a surface of the horizontal slot240of the link238and may force movement of the link238, the valve stem219, and the poppet valve218in the second direction235, which may seat the poppet valve218on the valve seat211and block fluid flow between the inlet209and the outlet210.

Referring toFIGS. 18A, 18B, and 20, the slot231of the lever230has a predetermined shape. In one embodiment, the predetermined shape of the slot231has an arcuate portion and a transverse or horizontal portion. The movement of the link238, valve stem219and poppet valve218may be determined by the movement of the engagement component223in the slot231of the lever230. The predetermined shape of the slot231may be contoured to provide a specific lift-to-rotation slope (lift of the poppet valve218versus rotation of the engagement component223and the output gear214). The chart ofFIG. 21shows a lift-to-rotation relationship that may be achieved with the linkage mechanism222. The initial slope241shows a constant rate of opening of the poppet valve218which may occur over a range252between minus sixty (−60) degrees and plus five (+5) degrees of rotation of the engagement component223and the output gear214. The approximate sixty-five (65) degrees of rotation may provide a range of the poppet valve lift242for accommodating variation of the seating position of the poppet valve218on the valve seat211which may be caused by the tolerances of components and assembly processes. In one embodiment, the range252of sixty-five (65) degrees for the initial slope241may occur over a poppet valve lift242of 0.80 mm, as illustrated by the chart ofFIG. 21. It should be appreciated that, however, it is possible to configure the linkage mechanism222, to achieve a range that is greater or less than sixty-five (65) degrees for the initial slope, and a poppet valve lift242that is greater or less than 0.80 mm.

In the embodiment illustrated inFIG. 20, the lever230and the valve stem219form a right angle relative to each other when either the second slot240or the second engagement component236is located on the longitudinal axis221of the valve stem219when the poppet valve218is in a closed position. More specifically, the intersection of the longitudinal axis221of the valve stem219and an axis transverse through the lever230to the axis249of the gear pin229forms a right angle when the poppet valve218is seated on the valve seat211.

FIGS. 22A-22Dshow a series of views of the linkage mechanism222setting the poppet valve218in a number of positions. Referring also to the chart ofFIG. 21,FIG. 22Ashows the linkage mechanism222positioning the poppet valve218in a closed position that may be near the end of the range252, for example at minus sixty (−60) degrees.FIG. 22Bshows the linkage mechanism222positioning the poppet valve218in a closed position that may be at a nominal position in the range252, for example at zero (0) degrees.FIG. 22Cshows the linkage mechanism222positioning the poppet valve218at a start-to-open position253that may occur at an angle of rotation of approximately ten (10) degrees.FIG. 22Dshows the linkage mechanism222positioning the poppet valve218near the full open position254that may occur at an angle of rotation of one hundred twenty-five (125) degrees.

It should be appreciated that the total angle of rotation for the linkage mechanism222is one hundred ninety (190) degrees (−65°+125°=190°) which exceeds the maximum one-hundred eighty (180) degrees of rotation for the scotch yoke of the EGR valve assembly100. The angle of rotation for the linkage mechanism222may be further increased by extending the slot231in the lever230. For example, the slot231may be extended to allow an angle of rotation of plus one hundred sixty (+160) degrees and total angle of rotation of two hundred twenty-five (225) degrees (−65°+160°=225°) as illustrated by the chart ofFIG. 21. It should be appreciated that the higher angle of rotation may afford a higher poppet valve lift255which may be a desirable feature for increasing the flow capability of the EGR valve assembly200.

With reference toFIGS. 22A, 22B, 22C, and 22D, the pressure angle256, which may occur at the point of contact258between the second engagement component236and the horizontal slot240, is essentially zero and remains essentially zero as the link238, the valve stem219, and the poppet valve218are moved between the valve closed and full open positions. The low pressure angle256may result in a force applied in the direction of arrow257which is essentially perpendicular to the pressure angle256and the horizontal slot240. It should be appreciated that the low pressure angle256may minimize or eliminate side loading on the valve stem219and minimize wear between the sliding surfaces of the valve stem219and the bushing243.

Other desirable characteristics afforded by the linkage mechanism222may be the high opening force made possible by the high mechanical advantage and high opening force that may be achieved by the low poppet valve lift-to-angle of rotation over the initial sixty-five (65) degrees of rotation. The low poppet valve lift-to-angle of rotation may also provide high anti-backdrive capability that may prevent unwanted valve opening during conditions of high backpressure and force especially when there is no electrical control signal applied to the EGR valve assembly200. It should also be appreciated that the initial slope241may also provide a desirable low flow resolution near the start-to-open point of the poppet valve218.

In one embodiment, the linkage mechanism222may have the engagement component223operably coupled or connected to a driven gear214and engaging a slot231of a lever230. It is also within the scope of the invention to reverse these positions wherein the slot231may be operably connected to the driven gear214and the engagement component223may be operably connected to the lever230. In a similar manner, the positions of the second engagement component236may be operably coupled or connected to the lever230and the slot240of the link238may be reversed wherein, the slot240may be located in the lever230and the second engagement component236may be operably coupled or connected to the link238. It should be appreciated that the location of the engagement component223, slot231, second engagement component236and slot240may in part be determined by factors such as packaging space, component design, cost, manufacturing capability, performance, or other factors.

Referring toFIGS. 17, 18A, 18B, and 19, the EGR valve assembly200may also include a return spring244that may be coaxial with the output shaft215and the output gear214. The return spring244may be operably coupled or connected to the output gear214and the first housing201. The return spring244may provide a bias force that will forcibly rotate the output gear214, engagement component223, lever230, and engagement component236and may cause the link238, the valve stem219, and the poppet valve218to move in a valve closing direction235. The bias force of the return spring244must be overcome by the force provided by the D.C. motor203and the gear drive assembly212before the poppet valve218may move in the valve opening direction233. It should be appreciated that it may be advantageous to minimize the initial bias force of the return spring244to avoid increasing the force capability of the D.C. motor203and the gear drive assembly212. It should also be appreciated that the EGR valve assembly200, shown inFIG. 15, may function in a similar manner to the EGR valve14in the EGR system10shown inFIG. 1and previously described herein.

In one embodiment, the D.C. motor203and the gear drive assembly212provide the rotational force for moving the linkage mechanism222. It is also within the scope of the present invention to only use an electrical drive device and eliminate the gear drive assembly212. It should be appreciated that this type of arrangement may be desirable for electrical drive devices, such as a torque motor, that may have a total rotation of three hundred sixty (360) degrees or less.

Referring toFIGS. 23A, 23B, and 24, another embodiment, according to the present invention, of the linkage mechanism222shown inFIGS. 18A and 18Bis used for the EGR valve assembly200. Like parts of the linkage mechanism222have like reference numerals followed by an apostrophe. In this embodiment of the linkage mechanism222′, the gear drive assembly212has been removed and the D.C. motor203′ has been repositioned. The D.C. motor203′ may provide a rotational force in response to an electrical control signal applied to the D.C. motor203′. A rotatable shaft207′ may be operably coupled to the D.C. motor203′ for translating the rotational force from the D.C. motor203′ to the linkage arrangement222′. The rotatable shaft207′ has an axis of rotation260.

Referring toFIGS. 23A, 23B, and 24, the linkage mechanism222′ may include a bar259which is operably coupled or connected to and rotatable with the rotatable shaft207′. The bar259may be a separate component operably connected to the rotatable shaft207′ or may be formed as a portion of the rotatable shaft207′. The bar259may be a variety of shapes and sizes including, but not limited to, a round bar, a rectangular bar, a square bar, or other suitable shape. The bar259may also be referred to as a lever, a link, or a hub. An engagement component223′ may be operably connected to the bar259. The engagement component223′ may be at least one of a pin, a sleeve, a roller, a ball bearing, a roller bearing or other suitable engagement component. As illustrated inFIGS. 23A and 23B, the engagement component223′ is a ball bearing which is eccentrically positioned from the rotational axis260of the rotatable shaft207′. The engagement component223′ may be supported on the bar259by a pin227′. The engagement component223′ may be operably coupled or connected to the bar259by a number of methods that may be within the scope of the present invention. It should be appreciated that these methods may include, but are not limited to, forming the engagement component223′ as a portion of the bar259, attaching the engagement component223′ directly to the bar259, or providing a rotatable connection to the bar259.

The linkage mechanism222′ may further include a lever230′ which may be coupled to a housing (not shown) by a pin229′. The pin229′ may allow for rotation of the lever230′ about the axis249′ of the pin229′. The lever230′ may include a slot231′ for receiving the engagement component223′. It should be appreciated thatFIG. 23shows a partially exploded view in which some components have been displaced to provide a better view of components of the linkage arrangement222′.

When the rotatable shaft207′ is forcibly rotated in a first direction232′, the bar259and the engagement component223′ may rotate about the axis260′ of the rotatable shaft207′. The forced rotation of the rotatable shaft207′ in the first direction232′ may cause the engagement component223′ to make contact with a surface of the slot231′ and may force the lever230′ to rotate in a first direction250′ about the axis249′ of the pin229′ and may force the lever230′ to move in a first direction233′ which may be parallel to a longitudinal axis221′ of the valve stem219′. When the rotatable shaft207′ is forcibly rotated in a second direction234′, the engagement component223′ may contact a surface of slot231′ and may force the lever230′ to rotate in a second direction251′ about the axis249′ of the pin229′ and may force the lever230′ to move in a second opposite direction235′ which is parallel to the longitudinal axis221′ of the valve stem219′.

The lever230′ may also include a second engagement component236′ that may be at least one of a pin, a sleeve, a roller, a ball bearing, a roller bearing or other suitable engagement component. The second engagement236′ may be operably coupled or connected to the lever230′ and extend from a surface237′ of the lever230′.

The linkage mechanism222′ may further include a link238′ which may be operably coupled or connected to a second end239′ of valve stem219′ and may be moveable with the valve stem219′. The link238′ may be a separate component or may be formed as a portion of the second end239′ of the valve stem219′. The link238′ may include a horizontal slot240′ for receiving the second engagement component236′ of the lever230′.

In operation of the linkage mechanism222′, when the rotatable shaft207′ is forcibly rotated in the first direction232′, forcing the lever230′ to move in the first direction233′, the second engagement component236′ may contact a surface of the horizontal slot240′ of the link238′ and may force movement of the link238′, the valve stem219′, and the poppet valve218′ in the first direction233′. When the rotatable shaft207′ is forcibly rotated in the second direction234′, forcing the lever230′ to move in the second direction235′, the second engagement component236′ may contact a surface of the horizontal slot240′ of the link238′ and may force movement of the link238′, the valve stem219′, and the poppet valve218′ in the second direction235′. The poppet valve218′, also referred to as a valve or valve member, may be connected to a first end220′ of the valve stem219′. It should be appreciated that the movement of the poppet valve218′ may be used to control fluid flow through a valve assembly, such as the EGR valve assembly200, as previously described herein.

Accordingly, the linkage mechanism222,222′ of the present invention can potentially extend the usable range of eccentric rotation to greater than one hundred eighty (180) degrees. The linkage mechanism222,222′ of the present invention allows an optimal equivalent scotch yoke starting angle over a range of stem/poppet valve axial positions to accommodate variations in the locations of mating parts, for example valve seats. The linkage mechanism222,222′ of the present invention minimizes side forces on the output or valve stem, due to a zero pressure angle at the stem-slot interface. It should be appreciated that, if the engagement component or pin is located on the stem centerline and the valve stem and lever form a right angle at closed valve, the side scrub is eliminated.

Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.