Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid controlled mechanical clutch or brake
Reexamination Certificate
2001-04-02
2002-10-15
Marmor, Charles A. (Department: 3681)
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Fluid controlled mechanical clutch or brake
Reexamination Certificate
active
06464611
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to automatic transmissions. More particularly, the present invention pertains to a hydraulic pressure control device for an automatic transmission which shifts a gear stage by controlling the hydraulic pressure to be applied to a plurality of friction engaging elements.
BACKGROUND OF THE INVENTION
In a known type of hydraulic pressure control device for an automatic transmission, control pressure is applied to a plurality of friction engaging elements by way of a corresponding linear solenoid valve depending on the shift signal. In this device, the application of the control pressure to one friction engaging element is carried out through use of a particular linear solenoid valve so that by controlling the energization of each of the linear solenoid valves, it is possible to apply the control pressure to the corresponding friction engaging element.
However, in this known device, the number of linear solenoid valves required for effecting engagement of the friction engaging elements is equal to the number of friction engaging elements. The result is a rather expensive device because linear solenoid valves are relatively expensive. Also, the energization control of each of the linear solenoid valves which is required for shifting becomes relatively complex, thus increasing the overall cost associated with the device.
To address this problem, it has been proposed to apply control pressure to a several of the friction engaging elements by switching one linear solenoid valve. This hydraulic pressure control device is configured to operate such that a control pressure outputted from a sole control valve under the control of a linear solenoid valve is applied to a plurality of friction engaging elements by way of a shift valve which is switched by an ON-OFF solenoid valve. The shift valve is switched depending on the gear stage to be produced in order to cause the shift valve to engage or disengage each of the associated friction engaging elements. According to this device, the ON-OFF solenoid valve, which is relatively inexpensive when compared to a linear solenoid valve, is combined with a linear solenoid valve. As a result, the number of linear solenoid valves in the control device can be reduced relative to the number of friction engaging elements, thus establishing an advantage from the standpoint of cost.
However, in this device, when performing a jumping shift (e.g., a shift from the fifth gear stage to the third gear stage or a shift from the third gear stage to the fifth gear stage) or a multiple shift (i.e., during a shift to one specific gear stage, another shift is made to another gear stage by changing the shift command), it is necessary to switch the shift valve and the friction engaging elements to be applied with the respective control pressure from the control valve at the same time. More specifically, a shift valve switching operation must be performed involving switching the energization condition of the ON-OFF solenoid valves, and at the same time the energization of the linear solenoid valves must be controlled to control the control pressure. In such a case, the control valve which applies the control pressure to the shift valve is switched and a switching operation of the shift valve is performed by switching the energization condition of the ON-OFF solenoid valve. Thus, to produce the desired gear stage, the timing of the switching of the shift valve must be synchronized with the timing of the switching of the control valve which applies the control pressure to the shift valve. However, experience shows that a time lag appears which ranges from initiation of the output of the switching signal to the ON-OFF solenoid valve for switching the ON-OFF solenoid valve to termination of the switching of the shift valve, and another time lag also appears which ranges from initiation of the output of the adjusting pressure from the linear solenoid valve after energizing control thereof to the output of the control pressure from the control valve to the shift valve. It is thus quite difficult to synchronize the shift valve switching with the control valve switching, and this may cause termination of the switching operation of the linear solenoid valve prior to a termination of the switching of the shift valve and/or vice versa. Under such situations, shift related problems or drawbacks may occur such as insufficient application of the control pressure to the required friction engaging element and/or application of the control pressure to an unnecessary friction engaging element.
Thus, a need exists for a hydraulic pressure control device for an automatic transmission that is not as susceptible to the difficulties and a drawbacks mentioned above.
More particularly, a need exists for a hydraulic pressure control device for an automatic transmission that can more reliably establish a desired shift by controlling the application of control pressure to the friction engaging elements by way of a shift valve.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a hydraulic pressure control device for an automatic transmission includes a plurality of linear solenoid valves each of which adjusts a hydraulic pressure outputted from an oil pump and outputs an adjusting pressure in response to a current applied thereto, a plurality of control valves each connected to one of the linear solenoid valves and outputting a control pressure in response to the adjusting pressure outputted from the corresponding linear solenoid valve, and a plurality of friction engaging elements each engaged or disengaged depending on the control pressure applied thereto, with the friction engaging elements producing a plurality of gear stages of the automatic transmission depending on combinations of different engaged and disengaged conditions of the friction engaging elements. In addition, a plurality of shift valves are each connected to one of the control valves to switch the friction engaging elements to which the control pressure is applied depending on the hydraulic pressure applied to the shift valves, and a plurality of ON-OFF solenoid valves are each connected to one of the shift valves to control application of the hydraulic pressure to each of the shift valves through energized conditions of the ON-OFF solenoid valves. A control unit controls application of current to each of the linear solenoid valves and the ON-OFF solenoid valves, and controls the adjusting pressure applied to each of the control valves and the control pressure applied to each of the friction engaging elements by controlling the hydraulic pressure applied to each of the shift valves. The control unit establishes a first shift pattern and a second shift pattern which produce gear stages by different combinations of energized or deenergized conditions of at least some of the ON-OFF solenoid valves. The control unit establishes an intermediate shift pattern during a transfer from the first shift pattern to the second shift pattern, such that the intermediate shift pattern makes it impossible to apply the control pressure from a specific control valve to the friction engaging element in case the friction engaging element to which the control pressure is applied from the specific control valve under the first shift pattern differs from the friction engaging element to which the control pressure is applied from the specific control valve under the second shift pattern by switching the shift valve.
In accordance with the present invention, in a shift control in which a shift is made such that switching the shift valve and switching the control valve are made concurrently during transfer from the first shift pattern to the second shift pattern, the application of control pressure from the specific control valve to the friction engaging element in the intermediate shift pattern is prevented. Next, during transfer from the intermediate shift pattern to the second shift pattern, the specific control valve from which application of control pressure in the interm
Futamura Suguru
Kondoh Noriyoshi
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Marmor Charles A.
Parekh Ankur
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