Control apparatus for hydraulically-operated vehicular...

Machine element or mechanism – Gearing – Interchangeably locked

Reexamination Certificate

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C477S150000, C477S155000

Reexamination Certificate

active

06397695

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control apparatus for a hydraulically-operated vehicular transmission having a plurality of hydraulic engaging elements for selectively establishing a plurality of speed transmission trains (or speed stages). In this invention, the term “vehicular transmission” means a transmission for use in a vehicle such as a motor vehicle.
2. Description of the Related Art
As this kind of control apparatus, there is known the following in Japanese Published Unexamined Patent Application No. 229179/1997. Namely, the control apparatus comprises a pair of linear solenoid valves, and switching means for switching oil passage connections into a state in which an oil pressure in a hydraulic engaging element for an arbitrary speed transmission train and an oil pressure in a hydraulic engaging element for a speed transmission train which is adjacent, as seen in an order of speed, to the arbitrary speed transmission train are controllable by the pair of linear solenoid valves. The switching means is controlled, at the time of speed changing, such that an oil pressure in an off-going hydraulic engaging element for a speed transmission train so far established and an oil pressure in an on-coming hydraulic engaging element for a speed transmission train to be established next which is adjacent, as seen in the order of speed, to the speed transmission train so far established become controllable by the pair of linear solenoid valves. (Note: The “off-going” hydraulic engaging element is a hydraulic clutch which has so far been engaged but which is to be disengaged from now on and the “on-coming” hydraulic engaging element means a hydraulic clutch which is going to be engaged from now on.) In addition, the pair of linear solenoid valves are controlled such that the oil pressure in the off-going hydraulic engaging element is lowered by one of the pair of linear solenoid valves, said one linear solenoid valve handling the off-going hydraulic engaging element, and that the oil pressure in the on-coming hydraulic engaging element is increased by the other of the pair of linear solenoid valves, said the other linear solenoid valve handling the on-coming hydraulic engaging element.
In the above-described conventional apparatus, the oil pressure in each of the on-coming and the off-going hydraulic engaging elements can be directly controlled by each of the linear solenoid valves. It is therefore advantageous in buffering or reducing a speed change shock.
In this conventional apparatus, however, it is only the two hydraulic engaging elements adjacent or next to each other as seen in the order of speed that can be controlled by the pair of linear solenoid valves. Therefore, in case a skipped speed change command (i.e., a command to change the transmission train by skipping one or more transmission trains), e.g., a command of downshifting from the 5th-speed transmission train to the 3rd-speed transmission train is issued, it is impossible to simultaneously control the oil pressures in the hydraulic engaging element for the 5th-speed transmission train and the oil pressure in the hydraulic engaging element for the 3rd-speed transmission train. As a solution, it is necessary, first, to control the oil pressures in the hydraulic engaging element for the 5th speed and in the hydraulic engaging element for the 4th-speed by the pair of linear solenoid valves to thereby downshift from the 5th-speed transmission train to the 4th-speed transmission train. It is, thereafter, necessary to control the oil pressures in the hydraulic engaging element for the 4th speed and in the hydraulic engaging element for the 3rd speed by the pair of linear solenoid valves to thereby downshift from the 4th-speed transmission train to the 3rd-speed transmission train. In this manner, it is possible with this conventional apparatus to perform the speed changing (or speed shifting) only one speed transmission train (or one speed stage) at a time. As a result, the speed change response to the skipped speed change command becomes poor.
In view of the above-described disadvantages, the present invention has an object of providing a control apparatus for a hydraulically-operated vehicular transmission in which the skipped speed changing can be smoothly performed with a good response.
SUMMARY OF THE INVENTION
In order to attain the above and other objects, the present invention is a control apparatus for a hydraulically-operated vehicular transmission having a plurality of hydraulic engaging elements for selectively estabilishing a plurality of speed transmission trains, said apparatus comprising: a pair of linear solenoid valves; switching means for switching oil passage connections into a state in which an oil pressure in a hydraulic engaging element for an arbitrary speed transmission train and an oil pressure in a hydraulic engaging element for a speed transmission train which is adjacent, as seen in an order of speed, to the arbitrary speed transmission train are controllable by the pair of linear solenoid valves; first control means for speed changing which controls the switching means at a time of speed changing such that an oil pressure in an off-going hydraulic engaging element for a speed transmission train so far established and an oil pressure in an on-coming hydraulic engaging element for a speed transmission train to be established next which is adjacent, as seen in the order of speed, to the speed transmission train so far established, become controllable by the pair of linear solenoid valves, the first control means also controlling the pair of linear solenoid valves such that the oil pressure in the off-going hydraulic engaging element is lowered by one of the pair of linear solenoid valves, said one linear solenoid valve handling the off-going hydraulic engaging element, and that the oil pressure in the on-coming hydraulic engaging element is increased by the other of the pair of linear solenoid valves, said the other linear solenoid valve handling the on-coming hydraulic engaging element; an accumulator connected to an oil passage which is in communication with a predetermined first speed transmission train; and second control means for speed changing which controls the switching means, at a time of speed changing from the first speed transmission train to a second speed transmission train which is not adjacent to the first speed transmission train as seen in the order of speed, such a) that the oil passage which is in communication with a hydraulic engaging element for the first speed transmission train is connected to an oil discharge passage, and b) that an oil pressure in a hydraulic engaging element for the second speed transmission train and an oil pressure in a hydraulic engaging element for a third speed transmission train which is adjacent to the second speed transmission train on a side near the first speed transmission train, as seen in the order of speed, are controllable by the pair of linear solenoid valves, the second control means also controlling the pair of liner solenoid valves such c) that the oil pressure in the hydraulic engaging element for the second speed transmission train is increased by one of the pair of liner solenoid valves, said one linear solenoid valve handling the hydraulic engaging element for the second speed transmission train, and d) that the oil pressure in the hydraulic engaging element for the third speed transmission train is kept to a state before the pressure increasing by the other of the pair of liner solenoid valves, said the other linear solenoid valve handling the hydraulic engaging element for the third speed transmission train. (Note: In this specification, “1st”, “2nd”, etc. as in “1st-speed transmission train”, etc. are used in a true sense of numerical order, i.e., in the meaning of No. 1, No. 2, etc. On the other hand, “first speed”, “second speed”, etc. as in “a first speed transmission train”, etc. are used not in the true numerical order but in the sense as explained herein.)
Accordi

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