Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Patent
1997-02-11
1999-03-16
Wright, Dirk
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
477154, 701 58, F16H 5948
Patent
active
058822763
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a shift control method for an automatic transmission, and more particularly, to a shift control method for an automatic transmission which is capable of reducing a shift shock caused by a skip down-shift and shortening a time period required for shifting.
BACKGROUND ART
An automotive automatic transmission generally includes a transmission mechanism having planetary gear units which include shift change elements (hereinafter referred to as gears) such as sun gears and planetary carriers and having hydraulic friction engaging elements such as hydraulic wet-type multiple disk clutches and hydraulic band brakes (hereinafter referred to as clutches and brakes, respectively). In an automatic transmission of this type, the gear connection is changed over by releasing one(s) of the friction engaging elements associated with shift change and by engaging the other friction engaging element(s) associated with shift change, to select those gears which contribute to torque transmission, to thereby establish a desired shift position.
In recent years, in order to improve the drivability of automobiles and reduce the fuel consumption, attempts have been made to further enhance the degree of electronic control for automatic transmissions and increase the number of shift positions or transmission stages. A typical multi-stage automatic transmission includes a main transmission mechanism constructed by an existing transmission mechanism and a subsidiary transmission mechanism coupled in line, in respect of torque transmission, with the main transmission mechanism. Those gears of the two transmission mechanisms which contribute to torque transmission are combined in various manners, to thereby establish an arbitrary one of a required number of shift positions, e.g., five forward shift positions and one reverse shift position. For example, the gear connection in the main transmission mechanism is changed over to effect a shift change operation among the first, second and third shift positions, and the gear connection in the subsidiary transmission mechanism is changed over to effect a shift change operation between the third and fourth shift positions. Further, to carry out a shift change between the fourth and fifth shift positions, the gear connection in the main transmission mechanism is changed over, with the gear engagement state (torque transmission path) in the subsidiary transmission mechanism set so as to correspond to the fourth shift position. In other words, by use of the subsidiary transmission mechanism, a switching is made between the lower-speed shift positions including the first through third shift positions and the higher-speed shift positions including the fourth and fifth shift positions.
In an electronic controlled automatic transmission, a shift map determined as a function of vehicle speed and throttle valve opening degree, as shown in FIG. 13, is generally used to select a shift position. From this map, an optimum shift position (target shift position) suitable to detected values of the vehicle speed and throttle valve opening degree is selected. In the case of a kick-down at a rapid acceleration, the target shift position is generally determined by the throttle valve opening degrees. That is, when the throttle valve opening degree traverses the 5-4 shift line or 4-3 shift line shown in FIG. 13, a down-shift command is output. As a result, if the accelerator pedal is depressed by the driver and the throttle valve opening degree .theta. reaches the point B from the point A in FIG. 13, a down-shift is carried out from the fifth shift position to the fourth shift position. When the throttle valve opening degree .theta. reaches the point C from the point A, a so-called skip down-shift from the fifth shift position to the third shift position is effected.
On an occasion that a direct down-shift from the fifth shift position to the third shift position is effected in the aforementioned multi-stage automatic transmission, that is, a skip down-shift is effected, i
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Fujita Kenjiro
Hatta Katsuhiro
Usuki Katsutoshi
Kwon Peter T.
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
Wright Dirk
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