Interrelated power delivery controls – including engine control – Transmission control – With clutch control
Reexamination Certificate
2002-03-22
2004-04-27
Bonck, Rodney H. (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
With clutch control
C475S127000, C475S128000
Reexamination Certificate
active
06726595
ABSTRACT:
This application is based on and claims priority under 35 U.S.C. §119 with respect to a Japanese Patent Application 2001-083100 filed on Mar. 22, 2001, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
This invention generally relates to an oil pressure control apparatus for an automatic transmission. More particularly, this invention pertains to an oil pressure control apparatus for an automatic transmission for changing a shift stage by selectively supplying control pressure outputted from plural control valves to a required friction engagement element.
BACKGROUND OF THE INVENTION
A known oil pressure control apparatus for an automatic transmission switches a shift stage from a neutral shift stage to a first shift stage by selectively supplying control pressure outputted from plural control valves to a required friction engagement element. Assuming the neutral shift stage is performed by a first combination of the friction engagement elements to be engaged, the control pressure supplied from each control valve to each friction engagement element is set to be approximately at a maximum oil pressure level to maintain the friction engagement elements for the first combination under an engaged condition.
Assuming the first shift stage is performed by a second combination of the friction elements to be engaged upon a shifting operation of the shift stage from the neutral shift stage to the first shift stage, a hydraulic circuit of the oil pressure control apparatus is switched for supplying the control pressure from each control valve to each friction engagement element for the second combination while the friction engagement elements for the first combination have been maintained under the engaged condition by continuously supplying the control pressure from the control valves thereto. The control pressure supplied to the friction engagement elements for the second combination is then gradually increased and the control pressure supplied to the other friction engagement elements is gradually decreased. Therefore, the friction engagement elements for the second combination are gradually shifted to the engaged condition and the other friction engagement elements are gradually shifted to a disengaged condition to smoothly shift the shift stage from the neutral shift stage to the first shift stage.
The control pressure supplied to the friction engagement elements for the second combination is then set to be approximately at a maximum oil pressure level to maintain the friction engagement elements for the second combination under the engaged condition. On the other hand, the control pressure supplied to the other friction engagement elements is set to be approximately at a minimum oil pressure level to release the friction engagement elements from the engaged condition. Under the above described condition, the first shift stage is continuously performed.
However, the above described oil pressure control apparatus may suffer from the following drawbacks. The engaging and disengaging operations of the required friction engagement elements are performed only by increasing or decreasing the control pressure to be supplied to the elements from the control valves. In this case, the engaging force for engaging the friction engagement elements is required to have a certain amount of engaging force when the first shift stage with a large torque is continuously performed. Therefore, a maximum pressure level of the control pressure is required to be sufficiently large for engaging the friction engagement elements.
However, when the shift stage is shifted to the first shift stage as described above, the control pressure supplied to the required friction engagement elements is required to be gradually increased. In this case, the adjusting range of the control pressure will be increased when the maximum oil pressure level of the control pressure is set to be sufficiently large based upon the engaging force of the friction engagement elements to be engaged for continuously performing the first shift stage. Therefore, the pressure adjustment ability may be deteriorated and the shifting operation may not be accurately performed. On the other hand, in case the maximum pressure level of the control pressure is restrained by heightening the resolving ability of the pressure adjustment, the friction engagement elements to be engaged for the first shift stage may slip when the torque is increased in response to a depressing operation of the accelerator pedal. Therefore, the friction engagement elements may not be maintained under the engagement condition.
Accordingly, the above-mentioned automatic transmission oil pressure control apparatus is still susceptible of certain improvements with respect to ensuring sufficient oil pressure to be supplied to the friction engagement elements for performing at least any one of the first shift stage or a reverse shift stage. Further, the apparatus is susceptible of certain improvements with respect to preferably performing the pressure adjustment of the oil pressure supplied to the friction engagement elements upon the shifting operation of the shift stage from the neutral shift stage to at least any one of the first shift stage and the reverse shift stage.
SUMMARY OF THE INVENTION
An oil pressure control apparatus for an automatic transmission including an output shaft is provided with plural linear solenoid valves, plural control valves, plural friction engagement elements, plural shift valves, and plural ON-OFF solenoid valves. The plural linear solenoid valves output modulated pressure in response to electric current applied to the linear solenoid valves. The plural control valves output control pressure in response to the modulated pressure from the linear solenoid valves. The plural friction engagement elements are engaged or disengaged in response to the supply of either the control pressure from the control valves or the line pressure for performing plural shift stages through engagement and disengagement of combinations of the plural friction engagement elements. The plural shift valves change the friction engagement element supplied with the control pressure or the line pressure in response to oil pressure applied to the shift valves. The plural ON-OFF solenoid valves change the supply condition of oil pressure to the shift valves in response to electric current applied to the ON-OFF solenoid valves.
The oil pressure control apparatus for the automatic transmission is further provided with a control unit for controlling the control pressure from the control valves by controlling the electric current applied to the linear solenoid valves and for changing the friction engagement element to be supplied with the control pressure or the line pressure via the shift valve by controlling the electric current applied to the ON-OFF solenoid valves. The control unit consequently sets a first shift pattern for supplying the control pressure to the friction engagement element for a first shift stage or a reverse shift stage from the control valve by a first combination of the current applied condition of the plural ON-OFF solenoid valves upon performing the first shift stage or the reverse shift stage and a second pattern for supplying the line pressure to the friction engagement element for the first shift stage or the reverse shift stage by a second combination of the current applied condition of the plural ON-OFF solenoid valves upon performing the first shift stage or the reverse shift stage.
Therefore, when the shift stage is shifted from the neutral shift stage to either the first shift stage or the reverse shift stage, pressure adjustment can be performed accurately by setting the first shift pattern, and the oil pressure to be supplied to the friction engagement element can be sufficiently ensured by setting the second shift pattern.
According to another aspect of the present invention, the control unit can determine the control pressure to be supplied to the common friction engagement element to be engaged at the first s
Aisin Seiki Kabushiki Kaisha
Bonck Rodney H.
Burns Doane , Swecker, Mathis LLP
Le David D.
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