Patent Application
20080017816
An exhaust valve assembly is shown generally at 10 in
An actuator 18 drives the shaft 14 to rotate about an axis 20. The valve 12 is fixed to the shaft 14 such that the shaft 14 and valve 12 pivot about the axis 20 together. The actuator 18 can be any type of actuator including a spring actuator, an electric actuator such as a motor or solenoid, or a vacuum actuator, for example. In the example shown, the actuator 18 comprises an electric actuator. A controller 22 cooperates with the actuator 18 to control exhaust flow through the valve body 16 by varying the position of the valve 12 as known.
During operation, the exhaust gases in the valve body 16 can reach very high temperatures. Thus, the valve 12 is exposed to high heat levels. Heat is transferred along the shaft 14 from the valve 12 to the actuator 18. If the heat transfer level is too high, performance of the actuator 18 can be adversely affected. In order to reduce the amount of heat transferred to the actuator 18, a thermal isolator 30 is associated with the shaft 14. The thermal isolator 30 serves to isolate the actuator 18 from the valve 12 in order to reduce an amount of heat transfer from the valve 12 to the actuator 18.
The thermal isolator 30 can be provided in many different configurations. In each configuration, the thermal isolator 30 comprises a coupling that couples an actuator shaft 32 to the shaft 14 that supports the valve 12. The actuator shaft 32 comprises a driving output from the actuator 18 and the coupling cooperates with the actuator shaft 32 and shaft 14 to transfer torque between the actuator 18 and the valve 12.
As shown in
Further, because the bellows 40 comprises a flexible connecting member, the bellows 40 can accommodate any mis-alignment between the shaft 14 and the actuator shaft 32, and can compensate for any shaft thermal expansion that may occur. Additionally, use of the bellows 40 allows shorter shaft lengths to be used, which provides for a more compact design.
In the example shown in
The direct coupling 50 comprises a rigid connecting element that is threaded or otherwise attached to both shafts 14, 32. In this configuration, the direct coupling 50, the shaft 14 for the valve 12, and the actuator shaft 32 are co-axial with each other, and with axis 20. Because the direct coupling 50 is made from a heat insulating material, the shafts 14, 32 are thermally isolated from each other, which significantly reduces heat transfer to the actuator 18. Further, use of the direct coupling 50 allows shorter shaft lengths to be used, which provides for a more compact design.
In the example shown in
The flexible shaft 60 can be made from any type of material including metallic and non-metallic materials. A heat insulating material is preferred to reduce the amount of heat transfer from the valve 12 to the actuator 18, however, if a metallic material is used, the length of the flexible shaft 60 can be optionally increased to reduce the effects of heat transfer. Due to the flexibility of the flexible shaft, increasing the length of the shaft does not necessarily adversely affect packaging.
In the example shown in
In each of the configurations set forth above, the thermal isolator 30 serves to reduce the heat transmission from a valve subjected to high exhaust gas temperatures to an actuator. Additionally, the use of the thermal isolator 30 as described above provides for more compact and flexible design configurations.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
