Interrelated power delivery controls – including engine control – Transmission control – Engine controlled by transmission
Reexamination Certificate
2000-02-14
2003-05-27
Rodriquez, Saul (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Engine controlled by transmission
C477S107000
Reexamination Certificate
active
06569059
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. HEI 10-33613 filed on Feb. 12, 1999 including the specification, drawings, and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control apparatus for a vehicle provided with a power source and a continuously variable transmission which is capable of continuously varying the gear ratio, and more particularly to a control apparatus and a control method, each of which is capable of canceling backlash which is present in a drive system and which causes vibrations in the longitudinal direction of the vehicle (backing or transient surge and shock) to be produced.
2. Description of the Related Art
It is known that when the gear ratio of a continuously variable transmission of a vehicle provided with the continuously variable transmission is raised to meet a requirement for accelerating the vehicle or a requirement for increasing output by demand made through depression of an accelerator pedal or the like, vibrations are produced in the longitudinal direction of the vehicle at a moment of completion of the gear change. The foregoing occurrence is called “backing or transient surge” which is caused by inertia torque or the elasticity of a power transmission system. That is, when the gear ratio of the continuously variable transmission is raised to meet the requirement for increasing the output from the power source such as an engine, or the requirement for accelerating the vehicle, the number of revolutions of a rotor of the transmission of power is changed. Therefore, inertia torque corresponding to the variation of the number of the revolutions (the angular acceleration) and the inertia moment is generated. When the number of revolutions of the rotor is stabilized to a required number of revolutions after the gear shift has been completed, the inertia torque is relieved. As a result, the inertia torque temporarily increases the drive torque, causing longitudinal vibrations to be generated owing to the deflection elasticity of the power transmission system.
An apparatus for preventing longitudinal vibrations of the vehicle of the foregoing type has been disclosed in Japanese Patent Laid-Open No. HEI 8-177997. The disclosed apparatus is designed to control the gear ratio to prevent vibrations in the longitudinal direction of the vehicle. That is, the moment at which the gear shift completes is obtained in accordance with a target gear ratio and a present gear ratio. Moreover, the half period of the vibrations of the vehicle in the longitudinal direction which are expected to be generated upon completion of gear shift is predicted in accordance with input torque corresponding to the gear ratio and an actual gear ratio. Thus, the gear ratio is forcibly corrected to a gear ratio by which the vehicle speed is raised at the time of a half period of the vibrations of the vehicle in the longitudinal direction before the moment at which the gear shift is completed. When the foregoing control is performed, about half of the inertia torque is relieved at the time of the half period before the moment at which the gear shift is completed. Therefore, the peak of the vibrations substantially coincides with the moment at which the gear shift is completed. When the torque caused from the vibrations is afterwards reduced, the residual inertia torque is relieved. As a result, the inertia torque acts to prevent vibrations. This control will be hereinafter referred to as a backing or transient surge preventive control.
The backing or transient surge preventive control realized by the apparatus disclosed in Japanese Patent Laid-Open No. HEI 8-177997 is structured such that the gear ratio is controlled only when the gear shift is completed. Therefore, there is apprehension that vibrations of the vehicle in the longitudinal direction occurring when the acceleration is started cannot completely be controlled. An apparatus proposed by the applicant of the present invention in Japanese Patent Application No. HEI 10-119772 is capable of effectively preventing vibrations of the vehicle in the longitudinal direction when both the output of the power source and the gear ratio of the continuously variable transmission are changed. According to the foregoing disclosure, the apparatus is provided with means which is structured such that when the output torque of the power source is controlled to correspond to the inertia torque generated owing to change in the gear ratio, the output torque of the power source is controlled to torque corresponding to the inertia torque and the target torque determined in accordance with the requirement for changing the drive force. The foregoing apparatus is able to effectively control the vibrations of the vehicle in the longitudinal direction caused from change in the drive force even when the gear shift is started following the request for a change of power source output.
Each of the foregoing apparatuses provides theoretical control realized with an ideal model having a drive system provided with a power source and a continuously variable transmission and is free from backlash and the like. Note that an actual vehicle includes a multiplicity of non-linear elements (for example, looseness caused by the backlash of the gear portions of the drive system and the spline portions). When the drive state is changed from a driven state in which the power source such as the engine is driven by the wheels connected to the continuously variable transmission to a driving state in which the output of the power source is transmitted to the wheels to drive the wheels, the backlash of the drive system exerts a great influence. That is, the kinetic energy accumulated during the motion as backlash is impulsively transmitted when the state of driving is changed. Moreover, output transmission timing of the power source is deviated. As a result, there arises a problem in that a structure constituted by adapting the foregoing control to an actual vehicle encounters generation of impact at an unintended time, and a deviation of the timing of the prevention control. Hence it follows that the vibrations of the vehicle in the longitudinal direction cannot satisfactorily be prevented. Thus, there arises a problem in that a person riding in the vehicle feels discomfort.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide a control apparatus for a vehicle provided with a power source and a continuously variable transmission which is capable of quickly and adequately canceling backlash when the relationship between a power source and wheels connected to the continuously variable transmission is alternately changed between a driven state and a driving state in a case of a vehicle having the backlash in the drive system, and sufficiently reducing vibrations of the vehicle in the longitudinal direction owing to cancellation of the backlash so as to prevent any uncomfortable feeling for a person in the vehicle.
To achieve the foregoing object, according to a first aspect of the present invention, there is provided a control apparatus for a vehicle provided with a power source and a continuously variable transmission, comprising a backlash preventive control unit structured such that when a driving state and a driven state between the power source and the continuously variable transmission and wheels connected to the power source and continuously variable transmission through a drive system are alternately changed, the backlash preventive control unit cancels backlash present in the drive system so as to prevent vibrations of the vehicle caused from the backlash.
The backlash of the drive system is backlash which is present in a gear portion and a spline portion which transmit driving force. Note that the amount of each backlash was previously determined when the drive system was designed. The expression “cancellation of backlash” means to reduce the gaps of the tooth flanks of the gear portio
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pang Roger
Rodriquez Saul
Toyota Jidosha & Kabushiki Kaisha
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