Internal-combustion engines – Charge forming device – Supercharger
Reexamination Certificate
2000-07-27
2003-09-09
Denion, Thomas (Department: 3748)
Internal-combustion engines
Charge forming device
Supercharger
C123S533000
Reexamination Certificate
active
06615809
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of mechanically driven centrifugal air compressors or superchargers (“hereinafter collectively referred to as “superchargers”).
BACKGROUND
A mechanically driven centrifugal air compressor or supercharger is typically mounted to a drive source, such as an internal combustion engine of a vehicle, that is remote from the drive source's crankshaft. Compressors or superchargers typically have an impeller, a volute chamber housing, and a drive configuration. These superchargers are mounted to a drive source or engine in order to increase the performance of the drive source or engine by forcing more air into the combustion chambers of the drive source. Since conventional impellers for superchargers are typically not very efficient for processing air, these conventional superchargers need to be operated at relatively higher speeds (rotations per minute (RPM's)) to achieve an output air pressure that is constant as possible over a wide speed range for the engine or drive source. However, the pressure of the outputted air for these conventional superchargers achieved over the wide speed range is still not very constant (i.e. may fluctuate dramatically) or is not very good.
Information relevant to attempts to address these various problems can be found in U.S. Pat. Nos. 2,835,238; 4,369,020; 5,224,459; 5,887,576 and 6,012,436. But each of these references suffers from one or more of the following disadvantages listed below.
The mechanical drive between the crankshaft and the supercharger is typically provided by a drive belt and pulley configuration wherein a generally smaller supercharger pulley is overdriven by a generally larger crankshaft pulley. But, the initial overdrive speed ratio that is derived from the primary drive configuration (i.e. belt drive and pulley configuration) is not sufficient to drive the impeller at a high enough speed for a more constant air pressure output. Therefore, gear up configurations or secondary overdrive components are provided by superchargers to further increase the speed of the impeller. Typically, an additional gear driven (i.e. gear to gear configuration) overdrive assembly is provided within the supercharger the supercharger housing to further increase or step up the output of the impeller. U.S. Pat. Nos. 2,741,234, 5,423,304 and 5,425,345 disclose examples of such gear to gear step up configurations for superchargers. These patents are incorporated by reference herein.
For example, conventional superchargers may require the impeller to be overdriven at a relatively high ratio in order to reach rotational impeller speeds in excess of 65,000 RPM. The reason the supercharger is being operated at such high speeds is because of the inefficient prior impeller designs. Also, air sealing at the gap between the impeller and the volute chamber housing needs to exist for more optimal operation of the supercharger. Typically, conventional impellers are positioned between a gap of 0.015 to 0.017 inch from the air sealing area of the volute chamber housing, and therefore, these impellers need to be rotated and driven at high speeds in order to provide a tighter air seal between the impeller and the air sealing area of the volute chamber housing. Further, conventional superchargers are not machined with high tolerances to provide for precision positioning between the parts, and it is therefore needed and desired to provide a supercharger that has precision made and/or high tolerance parts. It is also needed and desired to provide and use more precisely made and positioned supercharger parts having higher tolerances in order to achieve air sealing at the gap, especially if the impeller is to be rotated and driven at relatively lower speeds.
Other various problems and disadvantages exist with previous superchargers, impellers, and gear up configurations. The extremely relatively high speed at which a conventional impeller must be driven creates a large amount of friction and heat within the supercharger and its respective parts. These superchargers also tend to heat the air while it is being compressed thereby resulting in the output of hotter air by the supercharger. The heated air is less dense and is, therefor, less efficient than cooler air for increasing drive source or engine performance. Therefore, intercoolers have been used in conjunction with conventional superchargers to reduce the heat. Cooler air is desired since it is denser than hotter air in order to achieve the same results. Typically, conventional superchargers output higher pressurized air (i.e. ten pounds per square inch (10 psi)) because of the higher speeds at which the impeller is rotated, and the higher pressurized outputted air may cause stress and/or damage to the impeller and/or throttle components. Since the output of the supercharger is of relatively high pressure, flutter or pre-ignition of the drive source or engine may occur when the throttle is opened and closed due to the build up of reserved pressure in the output of the supercharger. Valves or waste gates have been provided to eliminate or reduce the build up of reserve air pressure. Special electronic or computer control components or fuel management systems may be necessary to regulate the manner in which the engine or drive source responds to the air pressure fluctuations and/or air density fluctuations. Therefore, in overcoming the above problems and disadvantages of operating the supercharger at relatively high speed, it is highly desired and needed to achieve better air sealing at the gap, especially if the impeller is to be rotated and driven at relatively lower speeds.
Also, the gear driven (i.e. gear to gear configuration) overdrive assembly contained within the supercharger housing typically includes at least one relatively heavy, large gear in order to achieve the necessary gear up ratio. The heavy, large gear, therefore, increases the overall size and weight of the supercharger since the housing would have to be made large enough to house the heavy large gear. Also, these gear driven overdrive assemblies typically use oil within the housing to lubricate the gears and bearings, and the oil further adds to the overall weight of the supercharger and the oil also retains heat within the supercharger.
Further, the impeller and the meshing of the overdrive gears while rotating at extremely high speeds may cause a considerable amount of friction, heat and noise to be produced. Since the impeller must be rotated at extremely high speeds and because the conventional drive components are relatively large and heavy, a substantial amount of inertia exists and must be overcome to drive and operate the supercharger and its respective components at extremely high speeds. Also, the existence of inertia within the drive configuration causes stresses and wear and tear on its respective components including the drive belts. The inertial forces are most pronounced during acceleration and deceleration, especially where these forces are uncontrolled. The power losses related to overcoming the forces of inertia results in decreased engine performance. Therefore, it is desired and needed to provide a supercharger that has a drive configuration that reduces or eliminates frictional contact, heat and inertia. Attempts have also been made to develop less noisy centrifugal superchargers by incorporating plastic gears within the overdrive gear assemblies. U.S. Pat. Nos. 5,423,304 and 5,425,345 disclose examples of such superchargers. These patents are incorporated by reference herein. However, such superchargers that attempt in overcoming the noise problem still require extremely high impeller speeds and thereby create substantial gear friction which may result in premature gear failure. Therefore, it is also desired and needed to provide a supercharger that has a drive configuration that reduces or eliminates noise but does not contribute to gear friction and/or gear failure.
External drives are known to produce relatively low speeds and low flow in contrast to inte
Ellis & Venable
Trieu Thai-Ba
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