Patent Grant
8408188
Superchargers can be used to significantly increase the horsepower (“HP”) and torque produced by an internal combustion engine through forced induction which boosts the mass flow rate of air to support combustion over what would normally be available through conventional or natural aspiration. Superchargers can take a variety of forms including positive displacement (e.g., roots-type and screw-type) and dynamic compressors (e.g., centrifugal), but all types are essentially pumps which need to be driven to produce the desired increase in power output. The amount of engine power consumed by the supercharger, termed “parasitic loss” can be significant especially in high boost applications.
Superchargers can be driven by a variety of means but are typically driven by the supercharged engine itself through a mechanical coupling such as a belt, gear, shaft, or chain. For example, the commonly-utilized and popular centrifugal supercharger is often belt driven, particularly in after-market applications where relatively straightforward modifications to the existing engine belt drive system can be made to accommodate the supercharger installation. For example, the serpentine belt drive used to provide input power from the crankshaft pulley to existing engine accessories such as the water pump, air conditioning compressor, alternator, power steering pump, etc., can typically be adapted to enable a belt to be routed to the supercharger input pulley.
Such belt drive adaptations can provide satisfactory performance results in some cases while minimizing the engineering expense and installation complexity that would be expected to accompany other drive systems. However, sharing the same belt between the supercharger and other engine accessories can be problematic in high boost/power applications where the parasitic supercharger loss can be high. In such cases, the engine may need to impart a large amount of power through the belt drive, for example 50 to 100 HP or more, which is far in excess of the loads the system was originally designed to bear. For example, the OEM (Original Equipment Manufacturer) components such as accessory brackets may emerge as a point of failure and present such problems as deflection under load that causes belt misalignment which reduces drive efficiency and can increase bearing load, or result in outright catastrophic failure in some cases. While replacement accessory brackets can be installed in an attempt to address this issue, such solutions can add expense and present additional installation complexity. The effectiveness of the solution can also be limited in many applications because space is typically at a premium due to the tight packaging of most modern engines.
Another problem with sharing the belt drive between the supercharger and engine accessories is posed by running the long serpentine belts that are typically necessary. Long belt paths tend to exacerbate problems with pulley alignment among the driven components and the long spans can also generate complex non-linear belt motions including vibration and resonance that can require additional components such as idlers and tensioners to be engineered and installed. Such components not only can add expense and installation complexity but may be restricted in their application in some cases because of the limited available space.
A belt drive pulley system termed a “flip drive” is configured to provide at least two belt drive pulleys that are co-axially and mechanically coupled to simultaneously rotate about a common axis and which share components such as an axle/bearings and mounting bracket. By being co-axially disposed, the belt drive pulleys can interface with belt drives which operate in separate planes. The flip drive is adapted for use in various applications so that power received on its first pulley from a first belt drive is transferred from its second pulley to a second belt drive (where the first and second belt drives are not co-planar).
Advantageously, in an illustrative example, the flip drive enables separate belt drives to be utilized for a supercharger and engine accessories. This results in shorter and more direct belt paths and removes the accessories and their associated brackets as points of failure from the supercharger belt path to increase reliability of aftermarket supercharger installations, and enables the respective belt drives to be optimized for their respective uses. For example, the belt drive between the crankshaft and supercharger can increase the contact area (i.e., “wrap”) between the belt and the supercharger pulley which can prevent belt slip.
Like reference numerals indicate like elements in the drawings. Elements are not drawn to scale unless otherwise indicated.
In an illustrative engine embodiment, a first belt drive is driven by the engine crankshaft pulley and operates in a plane that is proximal to (i.e., closest to) the engine block. A second belt drive operates in a plane that is distal to (i.e., furthest from) the engine block and is driven by the second pulley in the flip drive to operate one or more engine accessories such as the alternator and power steering pump. Thus, the flip drive can take engine power from the first belt drive off the engine crankshaft and transfer it to a second belt drive to drive the engine accessories where the pulley on the crankshaft and the pulleys on the engine accessories are not co-planar. That is, the pulley on the crankshaft can be in the proximal plane while the pulleys on the engine accessories can be in the distal plane. In this embodiment, use of the flip drive will thus enable use of a third belt drive off a second crankshaft pulley (that is co-axial with the first crankshaft pulley but located in the distal plane) to drive the supercharger, along with the water pump in some implementations.
In an illustrative usage application, the flip drive can be adapted for use with the “V” configuration eight cylinder (i.e., “V8”) Chevrolet engine such as the current “LS” series of all-aluminum engines that are used in vehicles manufactured and sold by General Motors. In this application, the flip drive is located on a mounting bracket so that when the bracket is attached to the LS engine, the axis of rotation of two co-axial pulleys in the flip drive is substantially parallel to the axis of rotation of the engine's crankshaft (i.e., the long axis of the vehicle in which the engine is mounted). The mounting bracket is then attached via 10 mm threaded fasteners to existing threaded openings in surfaces on the front portion of the engine block (where the front portion is the portion of the engine through which the end of the crankshaft opposite the flywheel or flex plate end is located). In the LS application in C5 and C6 (fifth and sixth generation) Corvettes, the mounting bracket positions the flip drive to the right and above the center of the crankshaft pulley when looking at the front of the engine, and below and to the left of the center of the power steering pump pulley.
The flip drive pulleys and mounting bracket may be fabricated from aluminum alloy such as 6061, for example, with T4 or T6 temper. The flip drive pulleys may be integrally formed as a unitary or monolithic piece and will typically be hard anodized to improve wear and belt handling characteristics. Alternatively, the flip drive pulleys may be formed from polymer or composite materials such a carbon fiber, or various combinations of materials. The surfaces of the pulley which contact the drive may also include circumferentially disposed inward radially disposed grooves to interface with corresponding ribs on the belt. However, in alternative embodiments v-type belts and corresponding pulley types may also be utilized.
In the LS Corvette implementation, the first belt drive in the proximal plane takes power off the first crankshaft pulley to drive the first flip drive pulley and the AC (air conditioner) compressor. The second belt drive in the distal plane takes power off the second flip drive pulley to drive the alternator and the power steering pump. The third belt drive in the distal plane takes power from the second crankshaft pulley to drive the supercharger (which is mounted towards the top left on the front of the engine) and the water pump.
The crankshaft 105 includes two pulleys that are arranged co-axially to drive two respective belt drives in each of the proximal and distal planes. A belt drive comprises a belt 150 that is routed to take power from the pulley on the crankshaft 105 in the proximal plane and drive the AC compressor 130. As shown, the idler 140 is utilized to provide increased wrap of the belt 150 on the pulleys of both the AC compressor 130 and crankshaft 105. In this particular example, the belt 150 is a 4-rib serpentine belt where the ribs interface with respective grooves in the pulleys and idlers.
Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/122,289, filed Dec. 12, 2008, entitled “Engine Accessory Belt Drive Pulley”, the disclosure of which is incorporated by reference with the same effect as if set forth at length herein.
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