Internal-combustion engines – Charge forming device – Supercharger
Reexamination Certificate
2000-02-10
2001-09-18
Nguyen, Hoang (Department: 3748)
Internal-combustion engines
Charge forming device
Supercharger
C060S611000
Reexamination Certificate
active
06289882
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE DISCLOSURE
The present invention relates to a rotary blower, such as a supercharger for supercharging an internal combustion engine. More particularly, the invention relates to a supercharger having a fluid pressure operated clutch assembly adapted to transmit torque from an input to one of the supercharger rotors.
Although the present invention may be used advantageously with superchargers having various rotor types and configurations, such as the male and female rotors found in screw compressors, it has been developed for use with a Roots blower type of supercharger, and will be described in connection therewith.
As is well known to those skilled in the art, the use of a supercharger to increase or “boost” the air pressure in the intake manifold of an internal combustion engine results in an engine having greater horsepower output capability than would occur if the engine were normally aspirated, (i.e., if the piston would draw air into the cylinder during the intake stroke of the piston). However, the conventional supercharger is mechanically driven by the engine, and therefore, represents a drain on engine horsepower whenever engine boost is not required. For the above and other reasons, it has been known for several years to provide some sort of engageable/disengageable clutch assembly disposed in series between the input (e.g., a belt driven pulley) and the blower rotors.
The assignee of the present invention has sold superchargers commercially including such clutch assemblies which operate electromagnetically. Unfortunately, the ON-OFF characteristics of electromagnetic clutches produce a transient load torque on the engine. For example, as the electromagnetic clutch is engaged, the result will be a “droop” in engine speed which will likely be perceived by the driver and may be manifested as an undesirable slowing down of the vehicle.
It is also known to provide a fluid pressure operated clutch assembly in which the clutch pack is spring biased toward a disengaged condition, and is moved toward an engaged condition in response to axial movement of a fluid pressure actuated piston member. In other words, the known supercharger clutch is of the “pressure-applied, spring-released” type. Although a supercharger with such a clutch arrangement can operate in a generally satisfactory manner, once the clutch is in either the engaged or the disengaged condition, the known arrangement does involve certain disadvantages during “transient” conditions, i.e., as the clutch assembly changes from the disengaged condition to the engaged condition, or vice versa. By way of example, a known supercharger clutch assembly of the pressure applied, spring released type requires a fairly long piston travel in order to achieve engagement of the clutch pack (or very high apply pressure), thus requiring substantial flow of fluid to accomplish the required piston movement.
Although such a high flow requirement is not a problem, once the engine has reached normal operating temperature, it frequently occurs that engagement of the clutch assembly is required soon after “cold engine start up”, while the engine oil is still cold. As a result, the known pressure applied, spring released system will have substantially longer time of engagement when the engine is cold than when the engine is warm. By way of example only, a typical engagement or release response time, as specified by the vehicle manufacturer, would be in the range of about 0.10 seconds. A substantially longer response time would result in the well known “turbo lag” feeling wherein the operator depresses the accelerator, but then there is a time lag before engine boost becomes noticeable, as is inherent in a turbo charger type of engine boost system. On the other hand, response time should not be so fast (when engaging) and so sudden as to result in a large torque spike being imposed upon the engine.
Another disadvantage associated with the pressure-applied type of supercharger clutch is that the oil pressure typically used is the engine lubrication oil circuit. As a result, the fluid pressure available to engage the clutch may be only in the range of about 20 psi., and even that very low pressure may not be available on a sufficiently consistent and predictable basis to be relied upon for engagement of the supercharger clutch, especially within the specified response time.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved supercharger and clutch assembly which overcome the above-described disadvantages of the prior art.
It is a more specific object of the present invention to provide an improved supercharger and clutch assembly which accomplishes the above-stated object, and which has both a variable and a controllable engagement and disengagement response time, thus avoiding transient overloading of the engine as well as a time lag upon engagement.
It is a further object of the present invention to provide such an improved supercharger and clutch assembly which operates in a consistent manner, substantially independent of variables such as engine oil temperature.
The above and other objects of the invention are accomplished by the provision of an improved method of controlling a rotary blower of the back flow or compression type having an input, a housing defining a blower chamber, and a pair of blower rotors disposed in the blower chamber and adapted to be driven by the input. A wet clutch is disposed in series driving relationship between the input and the blower rotors. The wet clutch includes spring means biasing the wet clutch toward one of an engaged in a disengaged condition, and a fluid pressure actuated piston having a pressure chamber biasing the wet clutch toward the other of the engaged and disengaged conditions.
The improved method of controlling the rotary blower is characterized by providing an electrohydraulic valve means operable to communicate the pressure chamber selectively to a source of high pressure and a source of low pressure. The method includes generating a command signal operable to bias the electrohydraulic valve means toward a position operable to communicate the pressure chamber to the source of whichever of the high pressure and the low pressure corresponds to the engaged condition. The method includes sensing a throttle position representative of change in commanded throttle position for the vehicle engine, and modifying the command signal in response to the throttle position whereby a change between the engaged and the disengaged conditions will occur more rapidly for a more rapid change in commanded throttle position.
REFERENCES:
patent: 4498429 (1985-02-01), Satow et al.
patent: 4669441 (1987-06-01), Okimoto
patent: 4708119 (1987-11-01), Miyake
patent: 5150693 (1992-09-01), Ohnaka et al.
Eaton Corporation
Kasper L. J.
Nguyen Hoang
LandOfFree
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