Gear drive assembly for actuator system

A gear drive assembly is used with an actuator of an actuator system. The gear drive assembly includes a housing and a gear arrangement disposed in the housing and including at least three gear stages having at least three driven gears. The at least three driven gears alternate between a plastic material and a metal material for each gear of the at least three driven gears.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to actuator systems for use on vehicles and, more specifically, to a gear drive assembly for an actuator system for use on vehicles.

2. Description of Related Art

Many devices in vehicles, such as a turbochargers and exhaust gas recirculation (EGR) valves, use an actuator system to control their functions and performance. For example, in certain actuator systems, pneumatic and electric actuators are used to provide positional control of variable vanes of a turbocharger or a valve plate of an EGR valve to adjust and maintain fluid pressure and fluid flow within an intake manifold of an engine. Controlling the fluid pressure and the fluid flow within the intake manifold provides optimum performance while maintaining legislated vehicle emissions.

Traditionally, the actuator system includes a gear drive assembly which transmits rotational motion to the device. The gear drive assembly provides a plurality of gears which collectively interact to provide a velocity and a torque to the device for moving the device. The gear drive assembly typically has three or more gear stages and uses a metal drive gear with all of the remaining gears being either all made of metal or plastic. For those actuators using all metal gears, the driven gears are typically supported by a ball bearing or a needle bearing system at each driven gear, which are larger and more costly. The all plastic driven gears cannot meet the latest medium to heavy duty vehicle requirements for a number of test cycles with an external load applied due to excessive gear wear causing failure. While an all metal gear system can meet these requirements, such a system is expensive. As such, there remains a need to provide an improved gear drive assembly.

SUMMARY OF THE INVENTION

The present invention provides a gear drive assembly for use with and driven by a motor in an actuator of an actuator system. The gear drive assembly includes a housing and a gear arrangement disposed in the housing and including at least three gear stages having at least three driven gears. The at least three driven gears alternate between a metal material and a plastic material for each gear of the at least three driven gears.

In addition, the present invention provides an actuator system including an output shaft and an actuator capable of moving the output shaft. The actuator includes a motor and a gear drive assembly driven by the motor. The gear drive assembly includes a housing and a gear arrangement disposed in the housing. The gear arrangement includes a drive gear made from a metal material, a first driven gear, a second driven gear, and at least one third driven gear to transmit rotation from the drive gear to the at least one third driven gear, the at least one third driven gear being rotatably coupled with the housing. The first driven gear, the second driven gear, and the at least one third driven gear alternate between a plastic material and a metal material.

One advantage of the present invention is that the gear drive assembly includes at least three stages with a metal drive gear, a driven plastic gear, and then metal-plastic gear material combinations for each subsequent gear. Another advantage of the present invention is that the gear drive assembly, for a metal gear that is radially supported by a metal pin, includes plastic bushings that are utilized to reduce friction at the gear to pin interface. Yet another advantage of the present invention is that the gear drive assembly includes plastic bushings that are flanged so that friction is also reduced in the direction of an axial support surface. Still another advantage of the present invention is that the gear drive assembly solves the issue of excessive gear wear enabling the durability requirements to be met while limiting the cost impact. A further advantage of the present invention is that the gear drive assembly used with actuator systems improves durability and fulfills the latest durability requirements for medium and heavy duty vehicle applications. Yet a further advantage of the present invention is that the cost of the gear drive assembly is lower than existing assemblies that use of all gears made from metal.

Other features and advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, an actuator system20is generally shown inFIG. 1. The actuator system20is typically used for controlling a control shaft21within a vehicle (not shown). In one example, the control shaft21controls the flow of a fluid to or from an engine22of the vehicle. As shown schematically inFIG. 1, the vehicle may include the engine22, an intake manifold24configured to flow air into the engine22, and an exhaust manifold26configured to flow exhaust out of the engine22. In one embodiment, the control shaft21is used in a turbocharger28which is fluidly coupled with each of the intake manifold24and the exhaust manifold26to increase flow of the air into the engine22by way of utilizing the energy of the moving exhaust flowing out of the engine22, as is commonly known to those having ordinary skill in the art. The actuator system20is positioned between the exhaust manifold26and the turbocharger28, with the actuator system20controlling a position of the turbocharger28through the control shaft21, which in-turn controls the pressure and the flow of the air into the engine22through the intake manifold24and is commonly referred to as boost pressure. It should be appreciated that the actuator system20may be used for controlling a mechanical device that shifts gears, lifts tailgates, lifts windows, etc.

The vehicle may further include an electronic control unit (ECU)30and an actuator controller32. The ECU30may be connected to the actuator controller32by a wire harness34having multiple conductors and connectors. The actuator controller32may also be connected to the actuator system20by a wire harness37having multiple conductors and connectors. For this illustration, the actuator controller32is shown as separate component. However, one having ordinary skill in the art will appreciate that the actuator controller32may be integrated within the actuator system20or the ECU30.

The ECU30may provide an electrical position input signal to the actuator controller32that may indicate a desired position of the control shaft21as controlled by the actuator system20. The actuator controller32may provide the necessary electrical control signal to the actuator system20to achieve the desired position of the control shaft21.

The actuator system20may also provide feedback in the form of an electrical position output signal to the actuator controller32. A “closed loop” control scheme may be used to maintain a desired position of the control shaft21as controlled by the actuator system20by comparing the feedback electrical position output signal value to a desired value and may adjust the electrical control signal to the actuator system20to maintain the resulting position of the control shaft21and the resultant fluid flow and boost pressure. Although the actuator system20is shown inFIG. 1controlling a position of the turbocharger28, one having ordinary skill in the art will appreciate that the actuator system20may be used anywhere within vehicles for controlling the flow of a fluid to or from an engine, such as with an exhaust gas recirculation (EGR) valve, a throttle fluidly coupled to an intake manifold24, waste gates, exhaust throttles, etc.

The actuator system20also includes an output shaft36, movable between a plurality of positions. The output shaft36may be coupled to the control shaft21of the turbocharger28, as described above. The turbocharger28may include a turbine (not shown) fluidly coupled with the exhaust manifold26and a compressor (not shown) fluidly coupled with the intake manifold24. The turbine may have a plurality of vanes (not shown). The movement of the control shaft21by the movement of the output shaft36may vary the orientation of the vanes to alter the flow of the fluid past the turbine, which in-turn alters the pressure and the flow of the fluid from the compressor into the intake manifold24.

In another embodiment, the control shaft21may be used in a valve38. The output shaft36may be coupled to the control shaft21of the valve38, as shown inFIG. 3. Movement of the output shaft36between the plurality of positions may move the control shaft21of the valve38between a plurality of positions. The valve38may be further defined as a butterfly valve40. The butterfly valve40may include a plate42coupled to the control shaft21and pivotally disposed within a valve housing44defining a bore46, with the plate42capable of changing the cross-sectional area of the bore46between the plurality of positions to alter the flow of the fluid. One having ordinary skill in the art will appreciate that the valve38may be any particular valve capable of controlling the flow of a fluid, such as a poppet valve, a flap valve, or a ball valve.

The plurality of positions of the control shaft21of the valve38may include a fully open position and a fully closed position. When the control shaft21of the valve38is in the fully open position, the valve38induces the least amount of restriction to the flow of the fluid. When the control shaft21of the valve38is in the fully closed position, the valve38induces the greatest amount of restriction to the flow of the fluid. The greatest amount of restriction to the flow of the fluid may result in complete stop of fluid flow. The plurality of positions may include at least one intermediate position between the fully open position and the fully closed position capable of partially restricting the flow of the fluid. One having ordinary skill in the art will appreciate that the plurality of positions of the control shaft21of the valve38may be any number of positions and any type of position to create a desire fluid flow. One having ordinary skill in the art will appreciate that the actuator system20may be configured to actuate any suitable component through the rotation of the output shaft36.

The actuator system20also includes an actuator48, which is shown inFIGS. 2 and 4. The actuator48is capable of moving the output shaft36between the plurality of positions. As such, the actuator48may be configured to meet desired velocity and torque characteristics of the output shaft36. The actuator48may be capable of having first and second outputs. It is to be appreciated that the actuator48may be configured to have any number of suitable outputs.

Furthermore, the actuator48may produce rotary or linear motion. For illustrative purposes, the actuator48shown in the Figures produces rotary motion. The actuator48includes a motor50(FIGS. 5A-5C). The motor50may be a direct current (D.C.) motor. The D.C. motor may or may not include brushes to produce motion. The motor50may be configured to be controlled by an electrical control signal. More specifically, at least one of the ECU30and the actuator controller32control the motor50(and, moreover, the actuator48) by the electrical control signal. One having ordinary skill in the art will appreciate that the motor50and the actuator48may be controlled by any suitable mechanism, such as a mechanical switch.

As illustrated inFIGS. 2, 4, and 5A-5C, the actuator system20further includes a gear drive assembly52, according to one embodiment of the present invention, driven by the motor50of the actuator48. The gear drive assembly52may include a housing54. The housing54includes an internal surface56defining a cavity58and a gear arrangement, generally indicated at60, disposed in the cavity58. The gear arrangement60includes at least three gear stages. In one embodiment, the gear arrangement60includes a drive gear62and at least three driven gears including a first driven gear64, a second driven gear66, and at least one third driven gear68. In one embodiment, the first driven gear64includes a first gear section64A and a second gear section64B and the second driven gear66includes a first gear section66A and a second gear section66B. The drive gear62is engageable with the first gear section64A of the first driven gear64, the second gear section64B of the first driven gear64is engageable with the first gear section66A of the second driven gear66, the second gear section66B of the second driven gear66is engageable with the at least one third driven gear68to transmit rotation from the drive gear62to the at least one third driven gear68. In one embodiment, the drive gear62is rotatably coupled to a motor housing. In another embodiment, the drive gear62may be operably coupled to the actuator housing54. The driven gears64,66,68are each rotatably coupled with the housing54. The drive gear62and the driven gears64,66,68have a gear ratio to selectively move the output shaft36and the base pitch is the same for each gear stage. One having ordinary skill in the art will appreciate that gear ratios may be determined by the respective diameters of the gears or by a number of gear teeth of each gear.

As illustrated inFIGS. 5A-5C, the motor50may have a shaft70rotatable about a shaft axis S and capable of transmitting rotational force with the shaft70. The shaft70may extend through the housing54and may be at least partially disposed in the cavity58, with the drive gear62operably coupled with the shaft70. Furthermore, the drive gear62may be fixed to and rotatable with the shaft70about the shaft axis S. As such, the drive gear62is fixed to the shaft70such that motion of the shaft70is imparted directly to the drive gear62. One having ordinary skill in the art will appreciate that the drive gear62may be coupled to the shaft70in any suitable way.

As illustrated inFIGS. 6-8, the drive gear62may have a plurality of gear teeth72extending radially and defining an input diameter of the drive gear62. As shown in the Figures, the drive gear62may have a substantially circular configuration. As such, the drive gear62may be referred to as a spur gear. Furthermore, the drive gear62may be comparatively smaller than the first driven gear64, the second driven gear66, and the at least one third driven gear68. As such, the drive gear62may be referred to as a pinion gear. One having skill in the art will appreciate that the drive gear62may have any suitable gear configuration, such as a bevel gear configuration.

The first driven gear64may have a plurality of gear teeth74on the first gear section64A extending radially and defining an output diameter of the first driven gear64. The first driven gear64may have a plurality of gear teeth76on the second gear section64B extending radially. As shown in the Figures, the first driven gear64may have a substantially circular configuration. As such, the first driven gear64may be referred to as a spur gear. Furthermore, the first driven gear64may have the first gear section64A and the second gear section64B spaced from and fixed to the first gear section64A. Both of the first and second gear sections64A,64B may have a substantially circular configuration. As such, the first driven gear64may be referred to as two spur gears. In addition, the first and second gear sections64A,64B may be fixed to one another such that the first and second gear sections64A,64B rotate in unison about an axis. As such, the first driven gear64may be referred to as a compound gear. One having ordinary skill in the art will appreciate that the first driven gear64may have any suitable gear configuration, such as a bevel gear configuration.

The second driven gear66of the gear arrangement60may have a plurality of gear teeth78on the first gear section66A extending radially and defining an output diameter of the second driven gear66. The second driven gear66may have a plurality of gear teeth80on the second gear section66B extending radially. As shown in the Figures, the second driven gear66may have a substantially circular configuration. As such, the second driven gear66may be referred to as a spur gear. Furthermore, the second driven gear66may have the first gear section66A and the second gear section66B spaced from and fixed to the first gear section66A. Both of the first and second gear sections66A,66B may have a substantially circular configuration. As such, the second driven gear66may be referred to as two spur gears. In addition, the first and second gear sections66A,66B may be fixed to one another such that the first and second gear sections66A,66B rotate in unison about an axis. As such, the second driven gear66may be referred to as a compound gear. One having ordinary skill in the art will appreciate that the second driven gear66may have any suitable gear configuration, such as a bevel gear configuration.

The third driven gear68of the gear arrangement60may have a plurality of gear teeth82extending radially and defining an output diameter of the third driven gear68. As shown in the Figures, the third driven gear68may have a substantially semi-circular configuration. As such, the third driven gear68may be referred to as a half spur gear. The third driven gear68may be rotatable about the axis A and may be operably coupled with the output shaft36. The output shaft36may extend through the housing54from the cavity58along the axis A. The output shaft36may be supported by the housing54by a bearing and a bushing, which allows the output shaft36to rotate about the axis A. The rotation of the at least one third driven gear68may rotate the output shaft36between the plurality of positions. In one embodiment, the at least one third driven gear68may be fixed to the output shaft36in what is commonly referred to in the art as a three-stage gear drive. One having ordinary skill in the art will appreciate that the at least one third driven gear68may have any suitable gear configuration, such as a complete spur gear or a bevel gear configuration.

As illustrated inFIGS. 6-8, the gear teeth74of the first gear section64A of the first driven gear64may be engageable with the gear teeth72of the drive gear62to define a first gear stage. The gear teeth76of the second gear section64B of the first driven gear64engages the gear teeth78of the first gear section66A of the second driven gear66to define a second gear stage. The gear teeth80of the second gear section66B of the second driven gear66may be engageable with the gear teeth82of the at least one third driven gear68to define a third gear stage.

In the gear arrangement60, the drive gear62is made from a metal material. The first driven gear64is made from a plastic material. The second driven gear66is made from a metal material. The at least one third driven gear68is made from a plastic material. In the embodiment illustrated, the at least one third driven gear68is also the last gear in the gear arrangement, which can also be referred to as the output gear. It should be appreciated that any gear stages after the at least one third driven gear68are made from metal-plastic gear material combinations for each subsequent gear.

The gear drive assembly52also includes a first stationary pin84that rotatably supports the first driven gear64and a second stationary pin86that rotatably supports the second driven gear66. Each of the stationary pins84and86are generally cylindrical in shape. Each of the stationary pins84and86are made of a metal material and coupled to the housing54. The gear drive assembly52further includes a pair of plastic bushings88, one on each end, to support the second driven gear66that interfaces with the second stationary pin86. Each of the plastic bushings88have a relatively thin cross section which allows the metal second driven gear66to be easily interchangeable with a lower cost plastic version of the same tooth geometry. Each of the bushings88are generally cylindrical in shape and have a flange90extending radially outwardly. It should be appreciated that the first driven gear64and the second driven gear66rotate about the first stationary pin84and the second stationary pin86, respectively.

The operation of transmitting rotation from the motor50to the output shaft36in accordance with the embodiment shown in the Figures is described below for illustrative purposes. One having ordinary skill in the art will appreciate that, although not expressly recited herein, numerous operations are possible in accordance with the present invention.

When the motor50is activated, the motor50rotates the shaft70about the shaft axis S. The shaft70is coupled to the drive gear62, which causes the drive gear62to rotate about the axis S. The drive gear62engages the first gear section64A of the first driven gear64at the first stage, which causes the first driven gear64to rotate about its axis. The first gear section64A and the second gear section64B of the first driven gear64are fixed to one another. As such, rotation of the first gear section64A results in simultaneous rotation of the second gear section64B.

The second gear section64B of the first driven gear64engages the first gear section66A of the second driven gear66, at the second stage, which causes the second driven gear66to rotate about its axis. The first gear section66A and the second gear section66B of the second driven gear66are fixed to one another. As such, rotation of the first gear section66A results in simultaneous rotation of the second gear section66B. The second gear section66B of the second driven gear66engages the third driven gear68at the third stage, which causes the at least one third driven gear68to rotate about the axis A. The at least one third driven gear68is coupled to the output shaft36, which causes the output shaft36to rotate about the axis A between the plurality of positions.

Referring toFIG. 9, a graph92showing measured wear at stage two of the gear arrangement60versus number of test cycles is shown. This test example is from an actuator durability cycling test where temperature is cycled from −40 degrees C. to +140 degrees C. with the actuator48moving against an applied external load. The graph92includes an X-axis94that represents number of cycles in the millions and a Y-axis96that represents total stage two wear in millimeters (mm). The graph92includes a plurality of plots98representing various material combinations for the stage two gears. Two of the plots98showing the least amount of wear are the material combinations of a metal gear and a plastic gear.

Accordingly, the gear drive assembly52of the present invention includes the gear arrangement60with a metal driven gear in combination with plastic driven gears at each stage. The metal-plastic coupling provides a significant improvement in gear wear. By having plastic driven gears for one-half of the coupling, a cost advantage is achieved versus a full metal system, while still getting a big advantage in wear performance by using metal for the other one-half of the coupling.

The present invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. As is now apparent to those skilled in the art, many modifications and variations of the subject invention are possible in light of the above teachings.

It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and are not to be in any way limiting, the present invention may be practiced otherwise than as specifically described.