Machine element or mechanism – Gearing – Interchangeably locked
Reexamination Certificate
2000-05-15
2002-06-18
Marmor, Charles A (Department: 3681)
Machine element or mechanism
Gearing
Interchangeably locked
C076S018000
Reexamination Certificate
active
06405611
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to an electrical sensing system for a vehicle shifting system. More particularly, the present invention relates to an electrical sensing system that senses the position of a shift lever.
In the early years of automobiles, most automobiles included manual shift transmissions where an operator separately controlled clutch disengagement/engagement, speed of shifting, and engine rpm (i.e., throttle operation) as part of the shifting process. Modern vehicles in the United States are predominately automatic shift transmissions, where an operator merely positions a shift lever in a selected gear position and then presses on an accelerator, while the vehicle systems automatically control the speed of clutch engagement and the timing of shifting. Specifically, in modern automatically shifted vehicles, the operator positions a shift lever in park, reverse, neutral, or drive. However, the act of positioning the shift lever in a selected gear position is totally separate from controlling the actual shifting process, such that it does not give an operator the control provided by manually shifted transmission systems. It is desirable to come up with a design that does not require drivers to learn how to shift a manual vehicle transmission, including learning how to operate a clutch pedal, a brake pedal, and an accelerator pedal while simultaneously shifting a shift lever. Further, it is desired to provide a system compatible with existing driving skills and control technologies, and to provide a system where the driver does not have to operate a clutch if he or she prefers not to do so. In short, it is desirable to give more control of the shifting process back to the vehicle driver, but it is desired to do so in a manner that does not force the driver to relearn how to operate the vehicle and that allows the driver to be as active or passive as he or she may want to be. It is also desirable to utilize technologies that are compatible with and that take full advantage of the electronic vehicle systems in modern vehicles.
In general, an automatic transmission selects the appropriate gear ratio without direct driver input. Existing automatic transmissions include a mechanical system, as well as an electronic control system. Such automatic transmissions consist of a series of mechanical sub-systems which accept rotational input from the engine and deliver it to the driving wheels. These sub-systems are sequential in that the output of the first system provides the input to the second system, and so on. The rotational output from the engine is connected via the crankshaft to the torque converter. The torque converter is a fluid coupling which transfers drive torque from the engine into the transmission. A fluid coupling is the preferred choice for this application as the rotational forces are transmitted through a fluid, rather than a fixed mechanical link. This enables some slipping in the couplings so that harsh engine vibrations and shocks are not transmitted down the driveline. A further effect is that, while the coupling is slipping, the transmitted torque is multiplied, hence the name of this component. This effect is useful in accelerating a vehicle from stationary (“launch feel”). The operation of the torque converter may be visualized as to the electric fans, face to face. As one fan is turned, the flow of air causes the second fan to rotate as well. In the case of a torque converter, the drive side is called the impeller and is connected directly to the engine crankshaft. The driven side is the turbine in which then provides the rotational input into the transmission. Modern torque converters may also include a lock-up clutch. A lock-up clutch is an internal mechanical feature which prevents the torque converter from slipping. The lock-up clutch is applied when the vehicle is at cruising speed to improve efficiency and fuel economy. Design of the torque converter is dependent on the engine characteristics. The torque converter must be able to handle the torque capacity and torsional stresses generated by the engine, while not generating too much heat. Vehicle driveability and launch feel is another important consideration.
Rotating elements within an automatic transmission are coupled by the series of clutches. By applying these clutches in specific combinations, the appropriate gears are selected to transmit the torque. The clutches and bands within the transmission are also referred to as the shifting elements. Their function is to couple the rotating elements within the transmission in order to drive or to hold the gears, and thereby achieve the different gear ratios. The shift elements are also important in controlling the shift quality, and can make the difference between a silky smooth gear shift or a harsh shift. Clutches are multiple-disc type units of automatic transmission which feature a series of friction plates stacked in parallel. When released, the individual plates are able to slip and rotate freely. When applied, the clutch pack is compressed by a servo piston forcing the individual plates to lock and rotate together. Thus, when the clutch is released rotating elements can turn independently. When a clutch is applied, rotating elements are coupled. Brake bands generally comprise a steel strap lined with a high-friction material. The strap wraps around a rotating cylinder, and permits free rotation of the cylinder when the band is released. Pressurized oil can be selectively supplied to a servo piston, thereby causing the band to wrap tightly around the cylinder and hold it stationary. Hence, brake bands are used to hold a rotating element stationary. During a shift, the clutches and bands are applied or released in combination to achieve a specific gear state. By regulating the oil pressure, the shift elements can be applied in a controlled manner such that torque is transferred smoothly.
The gear set is a mechanism of the mechanical system by which the input speed is reduced and the input torque is multiplied. One known arrangement includes planetary gears, which are axisymmetric about the centerline of the transmission. A typical arrangement in a modern automatic transmission is a “Ravigneaux” gearset including one forward sun gear, one reverse sun gear, and one planet gear supporting three long planet pinions and three short planet pinions. The Ravigneaux gearset also includes one ring gear connected to the output shaft of the transmission. By alternately driving or holding the first three elements in combination, the ring gear/output shaft is driven at different speeds, and the different gear ratios are obtained. The output from the transmission is connected to the propeller shaft (or transfer case in a 4WD vehicle). The rotation of the propeller shaft is directed to the driving wheels by the differential.
In addition to the mechanical system including the torque converter, clutches and bands, and gear set described above, modern automatic transmissions often include an electronic control system that provide the “brains” of the transmission. The electronic control system determines when gear shifts are required and then controls the shift quality during the execution of a gear shift. The electronic control system typically includes an electronic control unit (ECU), and an electrohydraulic unit (valve body). The ECU is a microprocessor which may be integrated into the engine control module or housed in a “stand alone” module. It is usually located in the vehicle interior and connected to the transmission and other systems via a wiring loom. The ECU continuously monitors a series of input signals provided by sensors. The input signals may include vehicle road speed, engine speed (rpm), transmission oil temperature, throttle position, rate of throttle opening, gear lever position, and mode switch. The ECU processes the input signals according to a series of algorithms to determine the current driving condition and the appropriate gear state for the transmission. If the appropriate gear state is diff
Bryant Eric W.
DeJonge Robert A.
Grand Haven Stamped Products
Ho Ha
Marmor Charles A
Price Heneveld Cooper DeWitt & Litton
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