Interrelated power delivery controls – including engine control – Transmission control – With clutch control
Reexamination Certificate
1999-07-15
2001-04-17
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
With clutch control
C477S070000, C477S166000, C475S207000
Reexamination Certificate
active
06217479
ABSTRACT:
TECHNICAL FIELD
The invention relates to automotive vehicle drivelines having an internal combustion engine and multiple-ratio gearing wherein the engine is connected drivably to torque input elements of the gearing without requiring a hydrokinetic torque converter.
REFERENCE TO RELATED APPLICATION
This disclosure has features that are common to the disclosure of copending U.S. patent application Ser. No. 08/353,290, filed Jul. 15, 1999, entitled “Transmission And Control System For Use With An Engine In A Hybrid Electric Vehicle”. That application is assigned to the assignee of this invention. The disclosure of that application is incorporated herein by reference.
BACKGROUND OF THE INVENTION
In a multiple-ratio automatic transmission of the kind shown, for example, in U.S. Pat. No. 4,938,097, a multiple-ratio transmission is situated on the torque output side of the hydrokinetic torque converter, the impeller of the converter being connected through the driveline damper to the crankshaft of an internal combustion engine. The turbine of the torque converter is connected to a torque input element of the gearing through a selectively engageable forward-drive friction clutch during operation in forward drive. A separate reverse drive friction clutch connects the turbine of the torque converter to another torque input element of the gearing during operation in reverse.
The torque converter of such known transmissions occupies a substantial space in the driveline assembly between the transmission gearing and the engine. It also is of a relatively large diameter relative to the diameter of the transmission gearing. Further, the converter has a substantial rotating mass, which must be accelerated by the engine during startup of the vehicle in forward drive or in reverse drive.
The effective mass of the converter, of necessity, includes the mass of the hydraulic fluid that circulates in the torus circuit defined by the converter impeller, the turbine and the stator.
The operating efficiency of the converter during startup is low. It varies from a zero value at stall to a maximum value of approximately 80-85% at the coupling point. The coupling point occurs at the transition from the torque multiplication mode to the coupling mode where the torque multiplication ratio is unity. The converter inefficiency results in power loss, which is manifested by an increase in temperature of the hydrokinetic fluid. This necessitates the use of oil coolers, which further add to the gross weight of the transmission assembly and which require additional packaging space for the automotive vehicle driveline.
The torque converter functions, as indicated above, to provide a smooth launch of the vehicle from a standing start. It also disconnects the engine from the driveline when the vehicle is at rest. A third principal function is the dampening of engine torsional vibrations.
Although the torque converter achieves a high torque multiplication ratio of about 2:1 at the outset of a vehicle launch, this torque ratio is accompanied by acceleration of a relatively large mass, which reduces useful torque at the vehicle wheels. The same is true for a transmission of the type disclosed in U.S. Pat. No. 5,836,849, which describes a large diameter startup clutch between an engine and a transmission torque input shaft.
SUMMARY OF THE INVENTION
The invention comprises a driveline with a converterless transmission in which the torque is delivered directly from the crankshaft of an internal combustion engine to the torque input element of multiple-ratio gearing. It is an objective of the invention to provide vehicle launch advantages of a torque converter transmission, as described above, without requiring a torque converter as part of the transmission assembly. In this way, the torque converter inefficiencies in the delivery of torque to the vehicle traction wheels can be avoided.
Since the torque converter is not present in the driveline of the invention, an increased proportion of the engine torque can be delivered directly to the wheels during startup, thereby compensating for any loss of torque multiplication that normally would be provided by a hydrokinetic torque converter. Further, the inefficiencies of a hydrokinetic torque converter that exist following the torque multiplication phase of the torque converter can be avoided, thus providing improved performance throughout a major portion of the operating time.
In accordance with a further objective of the invention, the engine may be disconnected from the driveline by an appropriate neutral-idle type control of the forward or reverse clutches. This is accomplished without the requirement for using a startup clutch intermediate the engine crankshaft and the transmission gearing. The inertia that otherwise would be introduced by the use of a separate startup clutch is avoided, which permits a faster response at the vehicle wheels to a command for startup torque delivered to the engine by the operator through use of an engine throttle.
Torsional isolation, which normally would be provided by a hydrokinetic torque converter, can be obtained with the invention by continuously slipping a friction element of the clutch and brake system for the gearing. During operation in the forward driving gear ratios, the slipping element may be the forward clutch. During operation in direct drive or third ratio, however, either the forward clutch or the direct clutch can be used. In overdrive or fourth ratio, the slipping element may be the direct clutch. During reverse drive operation, the reverse clutch may be used.
The invention further includes a hydraulic valve system using variable force solenoid valves for controlling the forward and reverse drive modes, the direct-drive ratio, the second and fourth drive ratios, and the low-and-reverse drive ratios. In the event that electric power is interrupted for the variable force solenoids, the low-and-reverse variable force solenoid will provide zero pressure. A shuttle valve responds to the loss of low-and-reverse variable force solenoid pressure, thereby making available engine pitot tube pressure, which provides a pressure for engaging the clutches and brakes of the transmission as a function of engine speed squared. In this way, a so-called “limp home” capability is achieved.
Loss of electric power will cause the system to default to third gear during operation of the forward drive ranges and to default to reverse drive when reverse drive range is selected by the operator.
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Brown Larry Thomas
Kraska Marvin Paul
Ortmann Walter Joseph
Estremsky Sherry
Ford Global Technologies Inc.
McKenzie Frank G.
Waddell Tisha D.
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