Patent Application
20050137770
The present invention relates to a transmission in a vehicle, and more particularly to controlling acceleration of a turbine in the transmission.
A transmission in a vehicle downshifts to a lower gear in response to various vehicle or driver behavior. For example, the transmission may downshift to a lower gear when the driver increases the throttle by a particular degree. In this instance, a throttle increase indicates a desire to accelerate the vehicle. A decrease in the speed of the vehicle may result in a coast downshift. During a coast downshift, the transmission detects that the vehicle has slowed below a certain threshold for the current gear and downshifts to a lower gear. Additionally, a manual downshift initiated by the driver causes the transmission to downshift to a lower gear. A driver may initiate a manual downshift to improve engine braking.
During a transmission downshift, the transmission turbine must accelerate to a speed level that is appropriate for the target gear. The transmission turbine spins at the same speed as the input of the transmission and determines how quickly the transmission is able to shift from one gear to another. Therefore, determining the appropriate acceleration of the turbine is important in order to establish effective downshifts. Various vehicle and environment conditions may affect the ability of the transmission turbine to accelerate properly. For example, the altitude of the vehicle affects air pressure and transmission performance. Current vehicle speed, transmission turbine speed, and torque converter slip also affect the appropriate turbine acceleration.
A turbine acceleration control system for a transmission in a vehicle comprises a shift module that determines a downshift type. An altitude model determines an altitude of the vehicle. A turbine speed sensor determines a speed of a turbine in the transmission. A controller communicates with the shift module, the altitude model, and the turbine speed sensor and determines a desired turbine acceleration based on the downshift type, the altitude, and the speed.
In another aspect of the invention, a turbine acceleration control method for a transmission in a vehicle comprises determining a downshift type at a shift module. An altitude of the vehicle is determined at an altitude model. A speed of a turbine in the transmission is determined at a turbine speed sensor. A desired turbine acceleration is determined based on the downshift type, the altitude, and the speed.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
A downshift acceleration control system 10 includes a vehicle transmission 12, an engine 14, and a torque converter 16. The transmission 12 receives rotational power from the engine 14 through the torque converter 16. The transmission 12 upshifts and downshifts based on a signal from a controller 18 as is known in the art. The transmission 12 may downshift in response to a throttle increase, vehicle deceleration, and/or a manual downshift. Typically, a downshift results in an increase in engine speed. Therefore, a downshift is accompanied by a concurrent increase in transmission turbine acceleration.
The controller 18 determines the desired transmission turbine acceleration based on inputs from a throttle position sensor 20, a shift lever 22, an altitude module 24, and a turbine speed sensor 26. The controller 18 receives a position of a throttle 28 from the throttle position sensor 20. The controller 18 receives a shift lever position from the shift lever 22.
The altitude module 24 calculates the altitude of the vehicle based upon a manifold absolute pressure (MAP) sensor 30. A method of determining altitude based on manifold absolute pressure is described in further detail in U.S. Pat. No. 5,542,390 entitled “METHOD OF ALTITUDE COMPENSATION OF EXHAUST GAS RECIRCULATION IN AN INTAKE MANIFOLD FOR AN INTERNAL COMBUSTION ENGINE,” which is hereby incorporated by reference in its entirety. The MAP sensor 30 determines a pressure of air entering the engine 14 through an intake manifold 32.
The controller 18 determines torque converter slip based on a signal from the turbine speed sensor 26 and a signal from the engine 14. Torque converter slip is calculated based on a difference between the transmission turbine speed and the engine speed. The controller 18 determines a torque gain factor based on a downshift type and applies the torque gain factor to the torque converter slip. For example, the controller 18 may consult a torque gain factor lookup table of calibrated torque gain factors. Each downshift type has a corresponding torque gain factor. The controller 18 uses the torque converter slip thus modified by the torque gain factor to adjust the desired transmission turbine acceleration.
Referring now to
The algorithm 40 determines the desired turbine acceleration according to downshift type, current turbine speed, and altitude at step 52. In the preferred embodiment, the algorithm 40 determines the desired turbine acceleration according to a second lookup table populated with turbine acceleration values. An exemplary high throttle value lookup table is shown in
Referring now to
Referring now to
The lookup tables 60 and 70 may be populated with transmission performance data sampled at various elevations. For example, the turbine acceleration values 76 are derived based on transmission performance samples at sea level. The high altitude turbine acceleration values 78 are derived based on transmission performance samples at a high elevation such as 5000 feet. This transmission performance data is evaluated based on downshift quality and performance.
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
