Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
1999-08-27
2001-04-17
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090170, C123S090180
Reexamination Certificate
active
06216654
ABSTRACT:
FIELD OF INVENTION
This invention relates to a valve train of an internal combustion engine and, more particularly, concerns a device for varying the timing of the opening and closing of the intake and/or exhaust valves with respect to the phase of the piston stroke.
BACKGROUND OF THE INVENTION
My U.S. Pat. No. 5,673,659 entitled “Lead Screw Driven Shaft Phase Control Mechanism”, issued on Oct. 7, 1997 and assigned to the assignee of this invention, discloses a mechanism that provides a selective timing or phase adjusting system between a drive gear and a driven camshaft with the drive gear being coaxially mounted and axially affixed with respect to the driven camshaft for rotation together. An intermediate connecting member is coaxially mounted with respect to the drive gear and the camshaft and is capable of axial movement and angular movement with respect to either the camshaft or the drive gear when experiencing its relative axial movement. The intermediate connection and a coupling member are connected to a geared device that is selectively activated by an electric motor which produces axial movement of both the intermediate connection and the coupling member with respect to the camshaft and the drive gear to any desired axial position between predetermined first and second positions. The gearing device provides a unidirectional drive system which allows the electric control motor to drive the mechanism to provide the optimum shaft phasing and is operably connected to a sleeve that is axially affixed to the intermediate connecting member. When in operation, the gearing device moves the sleeve axially, which in turn, moves the intermediate member axially with respect to both the drive gear and the camshaft. The intermediate connection member is an axially shifting member that has helical splines that rotationally affix it to the camshaft to allow relative rotation of the camshaft with respect to the drive gear. In one embodiment, the gearing device drives the sleeve while in another embodiment the gearing device is a threaded lead screw engaging complementary threads formed on the sleeve. In a third embodiment disclosed in the patent, the gearing device is a part of a gear sprocket that has an internally threaded hub that engages complementary external threads on the sleeve.
In my U.S. Pat. No. 5,860,328 entitled “SHAFT PHASE CONTROL MECHANISM WITH AN AXIALLY SHIFTABLE SPLINED MEMBER”, which issued Jan. 19, 1999 and assigned to the assignee of this invention, I disclose a two part variable valve timing system. In my co-pending patent application, Ser. No. 09/283,019, entitled “TWO PART VARIABLE VALVE TIMING MECHANISM”, filed on Apr. 1, 1999 and assigned to the assignee of this invention, I disclose a new form of power transmission that is substituted for the threaded jackscrew system which executes the axial motion of the shifting sleeve. Inasmuch as the lowest possible friction level is desired in phase changing devices to minimize wear and to allow use of a small electric motor for varying the position of the camshaft, it is important to have a transmission arrangement with less friction than an ACME screw. As stated in the aforementioned patent application, the optimum replacement for an ACME screw would be the ball-nut recirculating screw device which enjoys very low friction in operation. However, irrespective of the many advantages provided by such a device, using it for phase changing device is not possible from a practical standpoint because the required ball-return duct would interfere with the drive gear. Accordingly, in the mechanism covered by the above patent application, I have incorporated into the phase changing device one of the ball-nut transmissions disclosed in my co-pending patent application, Ser. No. 09/271,229, entitled “BALL-NUT TRANSMISSION”, filed on Mar. 17, 1999, and assigned to the assignee of this invention.
SUMMARY OF THE INVENTION
The present invention has certain similarities to the mechanism shown in my patent application, Ser. No. 09/283,019, entitled “TWO PART VARIABLE VALVE TIMING MECHANISM”, filed on Apr. 1, 1999, but differs therefrom in that the splined connection between the camshaft and the quill shaft, rather than being grouped together at one end or the other of the mechanism are, instead, separated so that the helical spline connection is incorporated with the control assembly and the straight spline connection is incorporated with the timing drive assembly. The advantage of so doing is to simplify the construction of the rear control assembly of the phase changing device. In addition, the power transmission includes one form of the ball-nut transmission disclosed in my above-mentioned co-pending patent application.
One object of the present invention is to provide a new and improved phase changing device that is provided with two major parts one of which is located at the front end of an internal combustion engine and the other is located at the rear end of the engine and in which the control section of the mechanism incorporates a ball-nut transmission for providing linear movement of a quill shaft interacting with straight splines incorporated with the timing drive assembly and helical splines incorporated with control section for changing the phase of a camshaft.
Another object of the present invention is to provide a new and improved phase changing device which has an axially movable quill shaft extending through a hollow camshaft and has one end of the quill shaft directly connected to the camshaft through helical splines and has the other end of the quill shaft connected by straight splines to the timing gear so that axial movement of the quill shaft provided by a ball nut transmission located at the other end of the quill shaft serves to rotate the camshaft a predetermined distance upon actuation of an electric stepper motor.
A further object of the present invention is to provide a new and improved phase changing device incorporating a non-recirculating ball-nut transmission for linearly moving a quill shaft and in which balls are encapsulated in hemispherical cavities formed in an axially movable sleeve surrounded by a nut member having a helical groove which cooperates with the balls for providing axial movement of the quill shaft and operates through helical splines at one end of the quill shaft to reposition the camshaft relative to the drive gear which forms a part of the timing gear assembly.
The above objects and others are realized in accordance with the invention by a phase changing device for an internal combustion engine that comprises a timing drive assembly located at one end of the engine and a control assembly located at the other end of the engine. The timing drive assembly has a drive gear adapted to be driven by the crankshaft of the engine and a hollow camshaft extends between the timing drive assembly and the control assembly. A quill shaft is co-axially mounted within the hollow camshaft and has a first portion located at the other end and is connected to the hollow camshaft by a plurality of helical splines surrounding the first portion of the quill shaft. A hub member is fixed with the drive gear and a second portion of the quill shaft is located at the above-mentioned one end of the engine and is connected to the hub member by a plurality of straight splines. An axially movable sleeve member is connected to and surrounds the first portion of the quill shaft located at the other end. A nut member surrounds the sleeve member and is drivingly connected to the sleeve member through a plurality of circumferentially spaced non-recirculating balls encapsulated in one of the members and located in a helical groove formed in the other of the members so that, upon rotation of the nut member, the sleeve member and the quill shaft move axially relative to the camshaft and simultaneously through the helical splines and the straight splines cause the camshaft to change its angular position with respect to the drive gear.
REFERENCES:
patent: 4438737 (1984-03-01), Burandt
patent: 4463712 (1984-08-01), Stojek
Dahbour Fadi H.
DaimlerChrysler Corporation
MacLean Kenneth H.
Walberg Teresa
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