Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid controlled mechanical clutch or brake
Reexamination Certificate
2000-12-21
2002-12-17
Estremsky, Sherry (Department: 3681)
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Fluid controlled mechanical clutch or brake
C475S122000, C477S080000, C477S087000
Reexamination Certificate
active
06494803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an automatic transmission mounted in a vehicle, and more particularly to a hydraulic control apparatus for controlling friction elements in such a transmission.
2. Description of Related Art
In the automatic transmissions of vehicles in recent times, a structure is employed wherein in the hydraulic pressure circuit that controls clutches and brakes (in this specification, these shall be referred to as “friction elements”) used to achieve each speed, exclusive control means (combining a linear solenoid valve, a duty solenoid valve or a linear solenoid valve with a regulating valve) are provided for each hydraulic servo of each friction element, and these are each controlled independently in order to improve control. The control means in such a hydraulic pressure circuit is supposed to secure a certain level of running ability of the vehicle by accomplishing hydraulic output to the hydraulic servo even during signal failures, and is supposed to be a normally open valve for accomplishing hydraulic output during times of no signal. Consequently when all of the control means simultaneously experience signal failures or sticking failures, an interlock condition arises wherein friction elements that originally were not to engage simultaneously engage. In order to prevent such a condition, technology for avoiding interlocking even in the event of the control means supplying hydraulic pressure because of an electrical failure or sticking of the valves or the like (hereinafter, collectively referred to as “failures”) when the vehicle is moving forward has been disclosed in Japan Patent 53-8028.
In the aforementioned art, it is possible to prevent interlocking by providing an interlock valve (
134
,
136
,
138
and
140
in
FIG. 2
of the aforementioned disclosure) for providing hydraulic pressure to each friction element as a signal pressure during failures. Furthermore, the interlock valve is a valve used to cut off all hydraulic pressure to friction elements disengaged at preset speeds, and hence when a failure occurs at a preset speed, that speed is fixed. As a result, it is possible to resolve the problems of insufficient drive force or over-revving by maintaining a constant speed when failures occur.
However, the aforementioned art is such that each speed is achieved by engaging a friction element (
54
) that is always engaged with exclusive friction elements (
48
,
52
,
56
,
58
) engaged in each speed, and consequently, the structure is such that only hydraulic pressure to the exclusive friction elements is applied in the aforementioned interlocking. Accordingly, in a gear train where there are no exclusive friction elements in each speed, the problem arises that this technology cannot be adapted.
Hence, it is the general objective of the invention to provide a hydraulic control apparatus that can maintain the achieved speed in the event of failures in an automatic transmission comprising a plurality of speeds using the same friction elements in achieving differing speeds, that is to say in an automatic transmission in which exclusive friction elements do not exist for each speed.
SUMMARY OF THE INVENTION
In order to achieve the above-described objective, in a first aspect a hydraulic control apparatus for an automatic transmission, of the type of hydraulic control apparatus provided with a plurality of friction elements and hydraulic servos for operating such, and wherein a plurality of speeds can be achieved by engaging at least two friction elements at a time out of the plurality of friction elements; and provided with a switching means for cutting off hydraulic control to the friction elements other than the friction elements engaged in order to achieve each speed within the plurality of speeds; wherein the plurality of speeds includes a third speed which, from among the friction elements, engages at least the first and third friction element and disengages the second friction element, a fourth speed which engages the first and second friction elements and disengages the third friction element, and a fifth speed which engages the second and third friction elements and disengages the first friction element; and said switching means includes a first switching valve which cuts off hydraulic control to the first friction element by applying, as a signal pressure, hydraulic pressure to the third friction element engaged in at least the third and fifth speeds and the second friction element engaged in the fifth speed, and a second switching valve that cuts off hydraulic control to the third friction element by applying, as a signal pressure, hydraulic pressure to the first friction element engaged in the third and fourth speeds and the second friction element engaged in the fourth speed.
In the above-described structure, it is effective as a second aspect for the structure to be further equipped with a plurality of control means capable of adjusting the hydraulic pressure to each hydraulic servo that operate the plurality of friction elements; wherein the hydraulic pressure from the plurality of control means is provided to each of the hydraulic servos.
Furthermore, in the above-described structure, a third aspect is effective for the structure to be provided with a hydraulic pressure source and first and second oil paths connecting the hydraulic pressure source with the hydraulic servos of the first and third friction elements, such that from among the plurality of control means, the first and second control means are positioned on these first and second oil paths; and the first and second switching valves are respectively positioned on the first and second oil paths, and cut off the supply of hydraulic pressure from the hydraulic pressure source to the other hydraulic servos by a hydraulic pressure being applied on the downstream side of the control means regulating the hydraulic pressure to the engaged friction elements.
In addition, in the above-described structure, a fourth aspect is effective in the structure for switching means to be such that the hydraulic pressure other than the pressure on the other friction elements, to which the hydraulic pressure supply is cut off, is applied as a signal pressure.
In addition, a fifth aspect is the above-mentioned plurality of friction elements may further include a fourth friction element, with the fourth friction element disengaged in the third, fourth and fifth speeds.
In addition, a structure may also be employed as a sixth aspect wherein the plurality of speeds further includes a second speed that engages the first and fourth friction elements and disengages the second and third friction elements, and a sixth speed that engages the second and fourth friction elements and disengages the first and third friction elements; and the first switching valve cuts off the hydraulic pressure supply to the first friction element by applying, as a signal pressure, a hydraulic pressure to the fourth friction element that is engaged at least in the case of the second speed, and a hydraulic pressure on the second friction element engaged in the case of the sixth speed.
In addition, a structure may also be employed according to a seventh aspect wherein the switching means includes a third switching valve capable of cutting of the hydraulic pressure supply to the second friction element, and the third switching valve is operated by hydraulic pressure to a friction element that engages in speeds where the second friction element is disengaged.
Or, a structure may be employed according to an eighth aspect wherein the switching means includes a third switching valve capable of cutting off the hydraulic pressure supply to the second friction element, wherein the third switching valve is operated by hydraulic pressure other than the hydraulic pressure to a friction element that engages in speeds where the second friction element is disengaged.
In the above-mentioned case, as a ninth aspect it is effective for the hydraulic pressure other than the hydraulic pressure to be a f
Hayabuchi Masahiro
Hisano Takayuki
Inoue Takahiro
Nishida Masaaki
Suzuki Akitomo
Aisin AW Co. Ltd.
Estremsky Sherry
Lewis Tisha D.
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