ACTUATOR WITH INTEGRATED DRIVE MECHANISM

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/736,490, filed November 14, 2005.

FIELD OF THE INVENTION

The present invention relates to an actuator assembly for use in a vehicle. More particularly the present invention relates to an arrangement for converting rotary motion from an actuator to axial motion.

BACKGROUND OF THE INVENTION

Actuators are used to operate a number of devices such as fluid control valves or control mechanisms used on turbochargers. The actuators may have axial motion or they may have rotary motion that is converted to axial motion. Converting rotary-to-axial motion requires an arrangement that efficiently translates the motion. Often times such arrangements require an additional element or component that increases the complexity of the device.

It is desirable to develop arrangements that eliminates complex or additional components as well as provide greater packaging advantages. Thus, the overall size, weight and cost of the device is reduced.

SUMMARY OF THE INVENTION

The present invention is directed to an actuator assembly having an actuator device operably associated with a housing, one or more rotating gear members operably associated with the actuator device, a bearing member operably associated with the one or more rotating gear members, and a cam operably associated with the one or more rotating gear members, for translating rotary motion of the gear members to axial motion. When the actuator device is actuated, the one or more rotating gear members rotate, causing the bearing member to move on the cam.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

Figure 1a is a front plan view of an actuator assembly, according to the present invention;

Figure 1 b is a side plan view of an actuator assembly, according to the present invention; Figure 2 is a sectional front plan view of an actuator assembly in a closed position, according to the present invention;

Figure 3 is a second sectional front plan view of an actuator in an open position, according to the present invention;

Figure 4 is a sectional side plan view of an actuator assembly, according to the present invention;

Figures 5A and 5B are isometric views of an alternate embodiment of the present invention; and

Figure 6 is a front plan view of an actuator assembly with the poppet valve replaced with a pin and the valve housing removed, according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

Figures 1 a and 1 b show the front and side views of an actuator assembly 10 which includes a valve assembly 12. Referring to Figures 1-4, actuator assembly 10 has a valve housing 14 and an actuator housing 16

designed to accept a connector/cover 18 with an integrated position sensor 20. An elastomer seal 22 is used to seal the connector/cover 18 to the actuator housing 16. Screws 24 secure the connector/cover 18 to the housing 16. An actuator device such as a DC motor 26 is secured by a bracket 28, and screws 30 to the actuator housing 16. The connector/cover 18 has an integrated leadframe 40 made of multiple electrical conductors 34. Terminals 32, of the motor 26, interconnect with the electrical conductors 34 of the electrical connector/cover 18. The connector/cover 18 has a connector 36 with terminals 38 that provide an external connection to a suitable electronic control unit (ECU) 42. The terminals 38 may also be a portion of the leadframe 40.

The rotating shaft 44 of the motor 26 is fitted with pinion gear 46 that engages with an intermediate gear 48. The intermediate gear 48 is located by pin 50 in actuator housing 16. The intermediate gear 48 engages output gear 52. The output gear 52 rotates about output gear shaft 54, which is located in the actuator housing 16. The shaft 54 is guided by a bearing member 56 and bushing 58 that are also located in actuator housing 16. The clip 60 secures the shaft 54 to the actuator housing 16. A cup plug 62 is used to cover the opening 64 in the actuator housing 16. A cam shown here in the form of a cam slot 66 is formed in output gear 52.

A sensor rotor 68 is attached to output gear 52 by a suitable method such as a plastic overmolding. Alternate fastening methods include ultrasonic welding, adhesives, or a "snap fit." The sensor rotor 68 is positioned relative to the associated position sensor 20 that is part of the sensing circuit 70 attached to the connector/cover 18. The position sensor 20 can be any type of sensor capable of detecting the position of the sensor rotor 68 and output gear 52. For example, one type of position sensor 20 is a non-contact position sensor, such as an induction sensor. Such a sensor can have an inductor overmolded onto the output gear 52. The electrical connections to the sensing circuit 70 are made through the leadframe 40, conductors 34, and terminals 38. The sensor rotor 68 couples a signal from a transmitter to a receiver on the position sensing circuit 70. The position sensing circuit 70

provides an output signal that is relative to the rotation and position of the output gear 52.

A stem member or valve stem 72 is fitted with a valve member or poppet valve 74 at one end and a bearing member or bearing 76 held by a pin 78 at the opposite end. The valve stem 72 is guided by a bushing 80 which is retained in valve housing 14 by suitable manner such as a press fit. Valve housing 14 has an inlet 84 and outlet 86. Inlet 84 is fitted with a valve seat 88 that will seat poppet valve 74 and block flow between the inlet 84 and outlet 86. The actuator housing 16 and valve housing 14 are shown as a single component. The actuator housing 16 and valve housing 14 can also be separated into two components. For example, the actuator housing 16 and valve housing 14 could be separated at the flange 90 and joined by a suitable means such as threaded fasteners 92 as shown in Figure 4. A spring 94 is coaxial with the output gear shaft 54. The spring 94 has features that engage the output gear 52 and the actuator housing 16. The spring 94 is designed to cause the output gear 52 to rotate in a counterclockwise direction. The cam slot 66, located in the output gear 52, is designed to receive the bearing 76 that is attached to one end of valve stem 72. The cam slot 66 is shaped to cause the bearing 76, valve stem 72, and poppet valve 74 to move in the direction of the valve seat 88 when the spring 94 applies the counterclockwise torque to the output gear ,52. The torque of the spring 94 is sufficient to cause the poppet valve 74 to seat on valve seat 88 and block flow between the valve inlet 84 and outlet 86. The actuator assembly 10 operates through the use of an engine control unit (ECU) 42 that provides a suitable electrical signal by way of terminals 38, leadframe 40, conductors 34, and motor terminals 32.

The motor 26 receives a signal from the ECU 42 and develops torque that is relative to the strength of the signal. The torque generated by the motor 26 will be transmitted through the pinion gear 46, and intermediate gear 48 to output gear 52. This torque will oppose the resistance of the spring 94. When the signal and the resulting torque is sufficient, it exceeds the resistance of the spring 94 and causes the output gear 52 to rotate.

Progressively increasing the signal provides a higher resultant torque that increases the degree of the output gear 52 rotation. Decreasing the signal reduces the degree of output gear 52 rotation.

The cam slot 66, formed in output gear 52, engages with bearing 76 that is attached to valve stem 72 by pin 78. The rotation of output gear 52 and cam slot 66, forces the bearing 76, pin 78, valve stem 72, and poppet valve 74 to move in an axial direction that unseats the poppet valve 74 from valve seat 88 and allow flow between the inlet 84 and the outlet 86.

The contour of the cam slot 66 determines the rate of axial movement versus output gear 52 rotation. The contour of the cam slot 66 also, in part, determines the operating force acting on the bearing 76, valve stem 72, and poppet valve 74. The contour is varied through the rotation to provide a variable poppet valve 74 opening/flow rate through the axial stroke of the poppet valve 74 to provide the desired operating characteristics. The contour of the cam slot 66 also controls the operating force, at a specific rotation/stroke. In one embodiment, the contour of the cam slot 66 is configured to provide a continuously variable rate through the rotation of the output gear 52. Controlling the mechanical advantage through rotation provides a method of matching the required force of the valve assembly 12 to the available torque of the motor 26. For example, in an alternate embodiment a higher force may be provided at a specific point through the rotation of output gear 52, by adjusting the contour of the cam slot 66. As the motor 26 rotates the pinion gear 46, intermediate gear 48, and output gear 52, the bearing 76 moves through the cam slot 66 changing the position of the valve stem 72 and poppet valve 74 relative to the output gear 52, thereby changing the amount of force transferred therebetween.

Sensing circuit 70 provides an output signal that is relative to the degree of output gear 52 rotation and axial poppet valve 74 movement. This output serves as an indication of relative flow through the poppet valve 74. In another aspect, the electronic sensing circuit 70 may also be programmed to provide a specific signal range for a given valve stem 72 and poppet valve 74 position. For example, the poppet valve 74 in a closed position may be programmed within a specific sensing voltage range. It is

believed that this capability improves the accuracy of valve stem 72 and poppet valve 74 position, as well as compensate for component and assembly variation. One way of achieving this is by accessing the sensing circuit 70 using a calibration procedure. The position sensor 20 and the output signal of the position sensor 20 are part of a closed loop control system for the poppet valve 74. The ECU 42 is programmed with a map of engine operating conditions and a desired flow for each condition. The desired flow is translated to the sensing circuit 70 output signal and ECU 42 signal. The ECU 42 provides the signal to the motor 26 and cause the poppet valve 74 to move to a desired position. The ECU 42 adjusts the signal to achieve-or-maintain the desired poppet valve 74 position.

The use of the cam slot 66, integrated into the output gear 52, is an effective means of converting the rotary motion of the motor 26 to axial motion of the valve stem 72. It is to be appreciated that this concept is also applicable to other devices that require axial movement. For example, the valve housing 14 portion of the actuator assembly 10 could be removed to expose the valve stem 72. The valve stem 72 can be connected to any device that would require axial operation, such as the control device of a turbocharger as shown in Figure 6. In Figure 6, a portion the valve housing 14 has been removed to expose the valve stem 72, and the poppet valve 74 has been replaced with a pin 108.

The integration of the cam slot 66 is based upon the manufacturing process of the component. For example, in one embodiment, the cam slot 66 is molded by an injection molded process, however, the cam slot may also be cast if a metal casting process is used, or compacted if a powdered metal process is used. In other embodiments, the cam slot 66 is made as a separate part and attached by suitable means such as plastic overmolding, press fit, riveting, welding, brazing, or adhesive. Also, it is not necessary that the cam slot 66 be completely formed through the output gear 52. In an alternate embodiment, a wall that limits the movement of the bearing 76 and valve stem 72 is utilized to provide the cam guidance.

Variations of the invention may be used for translating the motion. Referring to Figures 5a and 5b, the bearing 76 is attached to the output gear 52 and is offset from the center of rotation of the output gear 52. A guide slot 98 is formed with or attached to the valve stem 72; the guide slot 98 is operably configured for receiving the bearing 76. The valve stem 72 will move in an axial motion as the output gear 52 is rotated in either a clockwise or counterclockwise motion. The rate of travel and the ratio of mechanical advantage are dependent upon the shape of the slot 98, position of the slot 98, and the position of the bearing 76. In this embodiment, the pinion gear 46 is directly in mesh with the output gear 52.

In the first position, shown in Figure 5a, the bearing 76 it located at one end of the guide slot 98. As the output gear 52 rotates, the bearing 76 moves through the guide slot 98 and moves about the axis of the output gear 52. As the output gear 52 continues to rotate, the guide slot 98, valve stem 72 and poppet valve 74 arrive in the position shown in 5b. This embodiment is also not limited for use with a poppet valve 74, it is within the scope of the present invention to use the present invention in other devices that require rotary to axial motion.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.