INTRODUCTION

The information provided in this section is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

The present disclosure relates to a vehicle engine that include a gearbox for varying the compression ratio of the vehicle engine using a torque-actuated variable compression ratio (VCR) phaser. A variable compression ratio (VCR) engine typically includes an engine block that incorporates a plurality of cylinders, a piston disposed within each of the cylinders, connecting rods, a crankshaft, a bell crank, control links, a control shaft, and a gearbox. The bell crank is pivotally mounted on the crankshaft. The connecting rod connects the piston to one end of the bell crank. The control link connects the other end of the bell crank to the control shaft.

As each piston moves within a cylinder, the corresponding connecting rod applies a torque to the bell crank. The control link in turn transfers the torque from the bell crank to the control shaft, thereby causing the control shaft to rotate. The gearbox transfers torque from the control shaft back to the crankshaft and ensures that rotation of the two shafts is in time (or in phase). In addition, the gearbox couples an actuator—typically an electric motor or a hydraulic pump—to the control shaft. The actuator varies the speed of the control shaft relative to the speed of the crankshaft, and thereby varies the compression ratio of the cylinder.

SUMMARY

It is an object of the disclosure to provide a variable compression ratio (VCR) phaser configured to control a compression ratio of an engine having a crankshaft and a control shaft. The variable compress ratio phaser comprises: i) a control shaft gear configured to mesh with a gear on the control shaft of the engine and to receive torque from the control shaft; ii) a crankshaft gear configured to mesh with a gear on the crankshaft of the engine and to deliver torque to the crankshaft; and iii) a torque conversion mechanism configured to receive torque from the control shaft and to convert the torque to a linear force that changes the compression ratio of the engine.

In one embodiment, the linear force from the torque conversion mechanism phases the control shaft relative to the crankshaft to thereby increase or decrease the compression ratio of the engine.

In another embodiment, the linear force from the torque conversion mechanism adjusts a phase angle between the crankshaft gear and the control shaft gear to thereby increase or decrease the compression ratio of the engine.

In still another embodiment, the torque conversion mechanism comprises a first shaft on which the control shaft gear is mounted, the first shaft configured to rotate with the control shaft gear.

In yet another embodiment, the first shaft on which the control shaft gear comprises a helical lead screw at a distal end of the first shaft.

In a further embodiment, the torque conversion mechanism further comprises a spline connector configured to couple to the helical lead screw such that rotation of the first shaft causes the spline connector to rotate and to move linearly along the first shaft.

In a still further embodiment, the spline connector is further configured such that linear movement of the spline connector along the first shaft adjusts the phase angle between the crankshaft gear and the control shaft gear to thereby increase or decrease the compression ratio of the engine.

In a yet further embodiment, the torque conversion mechanism further comprises a spring stack configured to be compressed by the spline connector.

In one embodiment, when the torque received by the control shaft gear from the control shaft increases at higher loads, the spline connector moves in a first direction with increased linear force and compresses the spring stack, wherein the movement of the spline connector in the first direction adjusts the phase angle such that the compression ratio decreases.

In another embodiment, when the torque received by the control shaft gear from the control shaft decreases at lighter loads, the spring stack expands and moves the spline connector in a second direction opposite the first direction, wherein the movement of the spline connector in the second direction adjusts the phase angle such that the compression ratio increases.

In still another embodiment, the variable compression ratio phaser further comprises a control piston that limits the movement of the spline connector to moving only in the first direction when the torque received by the control shaft gear from the control shaft increases at higher loads.

In yet another embodiment, the control piston limits the movement of the spline connector to moving only in the second direction when the torque received by the control shaft gear from the control shaft decreases at lighter loads.

In a further embodiment, the control piston is hydraulically active and is controlled by a position of a hydraulic check valve.

Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.

