Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid controlled mechanical clutch or brake
Reexamination Certificate
2000-12-22
2003-05-27
Bonck, Rodney H. (Department: 3681)
Planetary gear transmission systems or components
Fluid drive or control of planetary gearing
Fluid controlled mechanical clutch or brake
C475S119000, C475S127000
Reexamination Certificate
active
06569050
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an automatic transmission mounted in a vehicle. In particular, the invention relates to a hydraulic control apparatus which controls the friction element in the transmission mechanism.
2. Description of Related Art
In order to control an automatic transmission for a vehicle, a hydraulic circuit controls the clutch and the brake (referred to as friction elements). The hydraulic circuit uses a specialty control valve (linear solenoid valve or duty solenoid valve) for each hydraulic servo (i.e., servo mechanism) of each friction element while independently controlling each valve. The control valves in the hydraulic circuit are permanently open to output hydraulic pressure in order to maintain certain running capabilities for the vehicle by outputting hydraulic pressure to the hydraulic servo even when signals to the control valves fail. Hence, if all of the control valves experience signal failure or stick failure simultaneously, the friction elements become engaged simultaneously. In order to avoid such a condition, Japanese patent publication No. 2689421, proposes a method in which a predetermined forward speed is achieved even when the control valves continue to output hydraulic pressure due to electrical failure or stick failure during the forward movement of the vehicle.
In the hydraulic circuit, the predetermined forward speed is established when the failure occurs while the vehicle is moving forward. However, if the vehicle is stopped and the engine is turned off after a failure occurs, for example, and the engine is turned on once again with the transmission shifted to drive (hereafter “during an engine restart time”), or the transmission is shifted to drive after shifting to neutral or park, or if a condition occurs in which all of the released friction elements now supply hydraulic pressure to all of the friction elements, the predetermined forward speed remains.
A higher predetermined forward speed is preferred so that a driver does not experience an unexpected downshift feeling when a failure occurs during actual driving. However, when a vehicle is stopped and restarted after a failure during running, a lower vehicle speed is preferred because a certain amount of driving power is needed in restarting. If the achieved speed is only one speed, like in the aforementioned hydraulic circuit, an awkward predetermined forward speed must be established, which neither eliminates the downshift feeling nor secures the driving power due to the two contradicting requirements described above.
Hence, the invention provides a hydraulic control apparatus which establishes at least two speeds to satisfy the two aforementioned requirements, the elimination of the downshift feeling caused by a failure during driving and securing a sufficient amount of driving power to restart the vehicle after the occurrence of a failure.
SUMMARY OF THE INVENTION
In a first exemplary aspect of a hydraulic control apparatus, the hydraulic control apparatus comprises a hydraulic source (
51
), a first, a second and a third hydraulic paths (L
32
, L
31
, L
5
) which are connected to the hydraulic source (
51
), a first, a second and a third hydraulic servos (
82
,
81
,
83
,
84
) which are connected with the first, second and third hydraulic paths (L
32
, L
31
, L
5
) and which operate a first, a second and a third friction elements (C-
2
, C-
1
, C-
3
, B-
1
) wherein predetermined forward speeds out of a plurality of speeds are achieved by engagement of at least two friction elements, a first, a second and a third control means (
72
,
71
,
73
,
74
) which are arranged in the first, second, and third hydraulic paths (L
32
, L
31
, L
5
) and operate an engagement release through a supply and removal of hydraulic pressure to the first, second and third servos (
82
,
81
,
83
,
84
) wherein, in the predetermined forward speeds, the first friction element (C-
2
) and the third friction element (c-
3
, B-
1
) are engaged by the first and third control means (
72
,
73
,
74
), a first valve (
55
) which is arranged in the second hydraulic path (L
31
) and which cuts off hydraulic pressure from the hydraulic source (
51
) to the second hydraulic servo (
81
) with downstream side hydraulic pressure, as a signal pressure, from at least the first control means (
72
); and a second valve (
60
) which is arranged in the first hydraulic path (L
32
) and which cuts off hydraulic pressure to the first hydraulic servo (
82
) and the signal pressure, wherein the downstream side hydraulic pressure of the first control means (
72
) and the downstream side hydraulic pressure of the third control means (
73
,
74
) can be impressed as signal pressures to the first valve (
55
), the first valve (
55
) cuts off the hydraulic pressure from the hydraulic source (
51
) to the second hydraulic servo (
81
) when both of the signal pressures are impressed.
In the above-described composition, installation of the second valve (
60
) enables the supply of hydraulic pressure to the second hydraulic servo (
81
) when a position is assumed wherein hydraulic pressure to the first hydraulic servo (
82
) and a signal pressure to the first valve (
55
) are cut off However, the supply of hydraulic pressure to the second hydraulic servo is cut off, though the supply of hydraulic pressure to the first hydraulic servo is enabled, when the position to not cut off is assumed. Hence, engagement of various friction elements is enabled due to the position of the second valve, this achieving the least two forward speeds.
In other exemplary aspects, the hydraulic control apparatus further comprises, a third valve (
53
) arranged in between the hydraulic source (
51
) and the first and second control means (
72
,
71
) and which is capable of selectively switching the supply and cutting off of hydraulic pressure to the first and second control means (
72
,
71
), wherein, the second valve (
60
) assumes a position to cut off hydraulic pressure to the first hydraulic servo (
82
) and the signal pressure to the first valve (
55
) when the third valve (
53
) assumes a position to cut off hydraulic pressure to the first and second control means (
72
,
71
).
In the above-described composition, by making the second valve (
60
) cut off the hydraulic pressure to the first hydraulic servo (
82
) and signal pressure to the first valve (
55
), when the third valve (
53
) assumes the position to cut off hydraulic pressure to the first and the second control means (
72
,
71
), supply of hydraulic pressure to the first hydraulic servo (
82
) and the signal pressure to the first valve (
55
) are cut off even when the third valve (
53
) later assumes the position to supply hydraulic pressure to the first and the second control means (
72
,
71
), enabling separate formation of forward speed, which makes it possible to set the different forward speed during operation of driving again by re-starting the engine from the condition in which the first and the second friction elements (C-
2
, C-
1
) are both released.
In other exemplary aspects, the second valve (
60
) is arranged in an upstream side of a signal pressure supply hydraulic path (L
32
), a branch of the first hydraulic path, to the first valve (
55
). Thus cutting off of hydraulic pressure to the first hydraulic servo (
82
) and the signal pressure to the first valve (
55
) may be achieved by one valve, which allows the size of the apparatus to be reduced.
In other exemplary aspects, the control apparatus is structured such that wherein when the first control means (
32
) outputs hydraulic pressure and a condition changes from engagement of the first friction element (C-
2
) to the second control means (
71
) ready to output hydraulic pressure, enabling supply of hydraulic pressure to the second hydraulic servo (
81
), at least predetermined forward speeds (5, 6 speed) are achieved by releasing the second friction element (C-
1
) using at least the first valve (
55
), and when the predetermined forward speed is high speed, the fi
Hayabuchi Masahiro
Hisano Takayuki
Inoue Takahiro
Nishida Masaaki
Suzuki Akitomo
Aisin Aw Co. Ltd.
Bonck Rodney H.
Le David D.
Oliff & Berridg,e PLC
LandOfFree
Hydraulic control apparatus for an automatic transmission does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic control apparatus for an automatic transmission, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic control apparatus for an automatic transmission will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3060548