1. Field of the Invention
The present invention relates to systems and methods for managing inertial torque reaction of rotating machines.
2. Background Art
A conventional powertrain has a “stationary” structure that is attached to the vehicle chassis with resilient mounts. In conventional powertrains, rotating inertia of various engine and transmission components including the crankshaft, flywheel, and torque converter of an automatic transmission, for example, is rotated in the same direction, having a compounding effect. When a compression or combustion event of the engine causes an acceleration of the rotating inertia, generally, there is an equal but opposite inertial torque reaction imposed upon the stationary structure. As such, the stationary structure is not truly stationary, but instead, vibrates in opposition to the accelerations of the rotating inertia. This vibration of the stationary structure passes vibration through the resilient mounts into the vehicle chassis, and may result in unwanted noise and vibration within the vehicle passenger compartment.
Conventional solutions to this vibration issue include controlling the engine operating conditions to minimize the magnitude and frequency range of the inertial torsional vibrations and tuning the powertrain mounts to minimize transmission of vibrations. However, the constraints placed on the engine/powertrain operation may impact the ability to achieve other desirable operating characteristics relative to responsiveness, fuel economy, and/or emissions, for example.
Other known solutions control one or more counter-rotating elements to reduce or eliminate inertial torque reaction, such as disclosed in U.S. Pat. Nos. 5,551,928, and 5,570,615, for example. While these approaches may reduce the torque reaction on the powertrain structure, the increased mass also increases weight and reduces responsiveness of the system.
The present invention includes a system and method for managing inertial torque reaction by rotating inertial powertrain or drivetrain components a direction opposite to the rotation of engine/motor inertial components, to reduce or eliminate torque reaction on stationary powertrain components.
In one embodiment, the present invention uses a device to provide counter-rotation of one or more engine/motor components relative to rotating transmission or transaxle components to reduce or eliminate the inertial torque reaction otherwise associated with angular acceleration/deceleration of a rotating mass on stationary structure or mounting components. The device may be implemented by a plurality of drive components such as gears, belts, chains and sprockets, or any similar device used to couple an output component of an internal combustion engine to one or more components of the powertrain, such as the torque converter of an automatic transmission or the generator of a hybrid powertrain. The device causes one or more inertial powertrain components to rotate in a direction opposite to that of various engine inertial components, such as a crankshaft. The effective inertia of the counter rotating components may be substantially matched to that of the forward rotating components using a device with an appropriate input/output ratio to create a speed differential between the counter rotating engine/motor components and the forward rotating powertrain components, or by adjusting the mass or component geometry of engine or powertrain components, for example.
In a transversely mounted internal combustion engine and transaxle, as generally used in, but not limited to, front wheel drive (FWD) vehicles, for example, the crankshaft and the torque converter may be connected using toothed wheels enabling the torque converter and crankshaft to rotate in opposite directions. A separate or integrated device may be used to reduce or eliminate backlash and associated noise, such as a scissors gear, for example. The opposing direction of rotation of the crankshaft and torque converter reduces or eliminates the inertial torque reaction on the stationary powertrain structure to reduce or eliminate unwanted vibration and noise.
A longitudinally mounted engine and transmission application, as generally used in, but not limited to, rear wheel drive (RWD) vehicles, for example, may incorporate a simple planetary gear set to connect the crankshaft to the torque converter. Such a planetary gear set typically includes a sun gear, a ring gear, and a carrier with a plurality of pinions that are constantly in mesh with the sun and ring gears. In such an arrangement, for example, the carrier may be rendered stationary by using a plurality of fasteners to connect it with the engine/motor block. The sun gear of the planetary gear set may be connected to the crankshaft using any of a variety of methods including using conventional fasteners or alternatively splines with at least one retaining ring. Likewise, the ring gear or the annulus of the planetary gear set may be connected to the engine/motor flex plate using a plurality of fasteners. Such an arrangement allows the ring gear to rotate in a direction opposite to that of the sun gear when the carrier is non-rotating. Thus, at least one drivetrain component, such as the torque converter, will rotate in a direction opposite to that of the crankshaft and create corresponding rotational inertia to reduce or eliminate the inertial torque reaction otherwise associated with a change in angular acceleration/deceleration of rotating components of the engine on the stationary powertrain structure reducing or eliminating associated noise and vibration.
The present invention provides a number of advantages. For example, the present invention provides systems and methods for managing inertial torque reaction by providing a counter-rotating inertia generated by conventional powertrain components to reduce or eliminate the torque reaction on the powertrain structure and improve performance with respect to noise, vibration, and harshness (NVH). Reversing rotation of conventional powertrain components obviates the need for additional components or mass to generate balancing inertia. This reduces any adverse impact on powertrain weight, responsiveness, and overall performance relative to conventional solutions that add components solely for balancing or canceling torque reactions associated with rotating inertia.
The present invention may allow variable displacement engines to idle and drive at low engine speeds with fewer than all of the cylinders firing without unacceptable NVH. Also, the reduced or limited inertial torque reaction on the stationary powertrain structure should reduce noise, vibration, and harshness (NVH) with the uneven firing intervals that occur when an 8-cylinder engine operates in a reduced or variable displacement mode with 3, 5, 6, or 7 firing cylinders, for example.
The above advantage and other advantages and features of the present invention will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.
As those of ordinary skill in the art will understand, various features of the present invention as illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce embodiments of the present invention that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present invention may be desired for particular applications or implementations.
Referring now to
A device 20 couples crankshaft 16 of engine 10 to a rotating component of a transaxle or transmission 70, such as torque converter 30 or flywheel, for example. As illustrated and described in greater detail below, device 20 may be implemented by one or more gears, sprockets, gear sets, belts, or other cooperating components to reverse the direction of rotation of torque converter 30 relative to crankshaft 16. The actual implementation and positioning of device 20 may depend on various application specific considerations. For example, in transversely mounted powertrain applications, the implementation of device 20 may be dictated by packaging constraints such that the particular implementation does not significantly increase the transverse length of the engine/drivetrain. In various embodiments, device 20 may also increase or decrease rotational speed of torque converter 30 relative to crankshaft 16 to generally match the effective magnitude of rotational inertia produced by rotating components of transmission/transaxle 70 to that of engine 10. Depending upon the particular application and implementation, the speed differential may be fixed, continuously variable, or selectable from two or more predetermined ratios. For example, the device may be implemented by a gear-change transmission, speed-change transmission, or continuously variable transmission. Applications using a selectable or controllable speed differential may include either a mechanical, electrical, or microprocessor based controller to determine an appropriate speed differential for current operating conditions or a selected operating mode, for example.
As also illustrated in
In operation, torque from engine 10 is carried by crankshaft 16 through coupling device 20 to torque converter 30, which provides a selective fluid coupling and torque multiplication under various operating conditions to turbine shaft 40. Chain drive 50 transfers torque from turbine shaft 40 and torque converter 30 through input shaft 60 to transaxle 70. Left axle 80 and right axle 90 receive power from transmission 70. Changes in rotational speed of various rotating components of engine 10, such as crankshaft 16, for example, result in a corresponding acceleration of rotational inertia and accompanying torque or moment. However, according to the present invention, the counter-rotation of various closely coupled transmission/transaxle or drive train components, such as torque converter 30, for example, results in a corresponding rotational acceleration of opposite hand or in the opposite direction which produces a torque or moment of opposite sense or direction that tends to reduce or cancel the torque or moment generated by the engine components. As such, the net vibrational torque reaction transmitted to the engine mounts or other stationary powertrain components, such as a vehicle chassis, is reduced or eliminated. The effective magnitudes of the rotational inertias generated by components associated with engine 10 and components associated with transmission or transaxle 70 may be adjusted via component mass and geometry as well as the relative rotational speed, which may be selected or determined by coupling device 20 as described herein.
A top-view block diagram illustrating a system or method for managing inertial torque reaction according to one embodiment of the present invention is shown in
As shown in
In addition to reversing the direction of rotation of various transmission components relative to rotating engine components, coupling device 255 may also provide a selected or selectable speed differential between motor/engine output shaft/crankshaft 254 and a transmission input shaft or torque converter 260 to substantially match the effective magnitudes of rotational inertia of rotating drive line and engine components. For applications utilizing a device 255 having a selectable speed differential, a corresponding mechanical, electrical, or microprocessor based actuator/controller may be provided to select one of the available input/output ratios based on an operating mode or current operating conditions, for example. Depending on the component mass and geometry, coupling device 255 may increase or decrease the rotational speed of one or more drive train components relative to one or more engine components. In one embodiment, coupling device 255 reduces the rotational speed of torque converter 260 relative to crankshaft 254 to better match effective rotational inertia magnitudes. However, the actual input/output speed of coupling device 255 will depend upon various application and implementation specific parameters including engine and drive train component geometry, relative mass of components, and relative location of rotating components, for example.
A cross-section of one embodiment of a device for coupling a prime mover to a drive train in a system or method for managing inertial torque reaction of a powertrain according to the present invention is shown in
As shown in
In operation, crankshaft 254 rotates in a first direction indicated generally by arrows 480. (Arrows 480 and 490 illustrate direction of rotation by use of the right hand rule where rotational direction is indicated by pointing the right-hand thumb in the direction of the straight arrow and closing the hand to make a fist such that the motion of the fingers indicates the direction of rotation.) Because sun gear 320 is attached to crankshaft 254 using a plurality of fasteners 460, sun gear 320 rotates in the same direction as crankshaft 254. Planet carrier 330 is rendered stationary by a plurality of fasteners 410 attaching it to a fixed, non-rotating portion of engine 110. Planet gears 340 are in mesh with sun gear 320 and rotate about their axes in a direction opposite to that of sun gear 320. Therefore the direction of rotation of planet gears 340, as generally indicated by arrow 490, is opposite that of crankshaft 254. Planet gears 340 are also in mesh with ring gear 350. The rotation of planet gears 340 forces ring gear 350 to rotate in the same direction, opposite to the crankshaft. Ring gear 350 is connected to flex plate 310 using a plurality of fasteners 450. As such, flex plate 310 also turns in the same direction as ring gear 350. Flex plate 310 is connected to torque converter 260 using a plurality of fasteners 440 forcing torque converter 260 to also rotate in the same direction. Thus torque converter 260 rotates in a direction opposite to that of crankshaft 254. The rotational inertia of torque converter 260 moving in a direction opposite to that of crankshaft 254 will reduce or eliminate the torque reaction induced by any acceleration of rotational inertia of crankshaft 254 on stationary powertrain structure and hence improve performance with respect to noise, vibration, and harshness (NVH).
A block diagram illustrating a system and method for managing inertial torque reaction according to one embodiment of the present invention in a hybrid powertrain is shown in
Carrier 526 of device 508 is coupled via meshing engagement of gears 530, 532, and 534 to motor shaft 536 of electric motor 538. Gear 532 is coupled to intermediate shaft 540, which is in turn coupled to gear 542, which is in meshing engagement with output gear 544 coupled to output shaft 546. A battery 550 or other energy storage device is coupled via electrical connection 552 to motor 538 and generator 510.
According to the present invention, hybrid powertrain 500 includes one or more operating modes where one or more inertial components of engine 502 and powertrain 506 rotate in opposite directions to provide counter-rotating inertia to reduce or eliminate reaction torque associated with acceleration/deceleration of rotating components. When the vehicle speed is low, so that the rotational speed of planet carrier 526 is substantially less than that of crankshaft 504, sun gear 522 and generator 510 are forced to rotate in the direction opposite to that of the crankshaft. Depending upon the effective magnitude of rotational inertias of engine components and drive train components, the present invention may also provide a predetermined or selectable speed differential to substantially match effective magnitude of inertias as previously described.
While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.