Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
1999-12-23
2001-03-20
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090310, C074S56800M, C464S002000, C464S160000
Reexamination Certificate
active
06202611
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
A large number of variable valve timing mechanisms have been proposed in the prior art for use in internal combustion engines and certain of such engines presently being manufactured have been equipped with mechanisms of this type. Some of the variable valve timing mechanisms that I have proposed for use in internal combustion engines are disclosed in the following U.S. patents and patent applications:
U.S. Pat. No. 5,673,659 entitled “LEAD SCREW DRIVEN SHAFT PHASE CONTROL MECHANISM”, issued on Oct. 7, 1997.
U.S. Pat. No. 5,860,328 entitled “SHAFT PHASE CONTROL MECHANISM WITH AN AXIALLY SHIFTABLE SPLINED MEMBER”, issued on Jan. 19, 1999.
U.S. patent application Ser. No. 09/283,019, entitled “TWO PART VARIABLE VALVE TIMING DEVICE”, filed on Apr. 1, 1999.
U.S. patent application Ser. No. 09/384,680 entitled “PHASE CHANGING DEVICE” filed on Aug. 27, 1999.
U.S. patent application Ser. No. 09/384,804 entitled “CAMSHAFT PHASE CONTROLLING DEVICE” filed on Aug. 27, 1999.
One characteristic of each of the mechanisms disclosed in the above-mentioned patents and patent applications is that they are all intended to be custom-made for the engines, i.e., integrally designed as part of the cylinder head and valve train mechanism of the engine. This approach can be expensive because the mechanism normally does not lend itself well for use across-the-board on different engines. In other words, there is no total unit interchangeability and, therefore, no cost reduction based on very large production volumes. This is true especially in cases where the mechanism is only being used on low volume top-of-the-line car models. The cost can also be increased if the mechanism is incorporated into the cylinder head and the valve train as the cylinder head is assembled on the engine. As new internal combustion engines are designed with variable valve timing devices, it is important to produce identical low-cost variable valve timing mechanisms suitable for uses on a variety of engines. With the possibility of large volumes, it would be possible to lower costs by designing better variable valve timing mechanisms with improved materials and higher durability.
Each of my patent applications identified above as items 3-5, disclose variable valve timing mechanisms that utilize a novel method of replacing splines by low-friction, low-wear encapsulated ball splines to angularly index the camshaft in relation to the camshaft drive gear. Another difference in these mechanisms, as compared to the prior art hydraulically operated mechanisms, is that the operational force is provided both ways by electrically driven stepper motors. In addition, the above patent applications also disclose a novel method of axially moving a shifting sleeve by using a low friction encapsulated ball lead screw as a linear motion device.
SUMMARY OF THE INVENTION
The present invention concerns a camshaft drive device that incorporates some of the features of my earlier patented and patent application designs. Also, the present invention provides a simple, compact, sturdy, low friction, low cost, self contained, and universal variable valve timing device for an internal combustion engine. By so doing, the device is usable on different engines, so long as such engines satisfy the proper standardized mounting requirements.
In the preferred form, the camshaft drive device according to the present invention has a portion thereof adapted for special mounting onto the rear end of an internal combustion engine having the usual crankshaft. More specifically, the camshaft drive device comprises a timing drive assembly located at the forward end of the engine and a control assembly located at the rear 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 front end of the engine that is connected to the drive gear. The quill shaft has a second portion located at the rear end of the engine that is formed with a plurality of hemispherical cavities located in a plane extending transversely to the longitudinal axis of the quill shaft. Each of the hemispherical cavities of the quill shaft accommodate a ball. The hollow camshaft is rigidly connected to a cylindrical extension member encircling the second portion of the quill shaft and has its inner cylindrical surface formed with straight splines extending along the longitudinal axis of the hollow camshaft. The control assembly also includes an axially movable sleeve member which is connected with a cylindrical connector member located between the balls supported by the quill shaft and the straight splines of the cylindrical extension member. The cylindrical connector member has the outer surface thereof supporting a plurality of circumferentially spaced balls which mate with the straight splines of the cylindrical extension member and has its inner surface formed with helical splines which mate with the balls of the quill shaft. 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 the sleeve member and located in a helical groove formed in the nut member. The arrangement is such that, upon rotation of the nut member, the sleeve member and the cylindrical connector member are moved axially to cause the helical splines of the cylindrical connector member, acting through the straight splines of the cylindrical extension member, to provide a phase change of the camshaft relative to the drive gear.
One object of the present invention is to provide a new and improved camshaft drive device that is provided with a timing drive assembly at the front end of an internal combustion engine and a control assembly at the rear end of the engine characterized in that a portion of the control assembly is capable of being a self-contained unit which can be easily mounted to the cylinder head of the engine through a snap-action attachment arrangement.
Another object of the present invention is to provide a new and improved camshaft drive device that includes an electromechanical actuator for indexing the cams of the exhaust camshaft or intake camshaft and in which an encapsulated ball-nut-lead-screw type subsystem is used to affect shifting motion between two sets of splines.
A further object of the present invention is to provide a new and improved camshaft drive device incorporating a non-recirculating ball-nut transmission for linearly moving a sleeve member and in which balls are encapsulated in hemispherical cavities formed in the sleeve member which is surrounded by a nut member having a helical groove for cooperating with the balls and providing axial movement of the sleeve member and, through straight splines at one end of the quill shaft and a connecting member provided with a plurality of balls located in a transverse plane and attached to the sleeve member, serves to interconnect the straight splines with the helical grooves for angularly repositioning the camshaft relative to an engine-driven drive gear of the timing gear assembly.
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DaimlerChrysler Corporation
Lo Weilun
MacLean Kenneth H.
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