Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid controlled mechanical clutch or brake
Reexamination Certificate
2000-03-17
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
C475S121000
Reexamination Certificate
active
06464610
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an automatic transmission, and more particularly to a hydraulic pressure control apparatus for controlling engagement elements accommodated in a planetary gear transmission mechanism of the automatic transmission.
2. Description of Related Art
Hitherto, an automatic transmission incorporates a planetary gear transmission mechanism for realizing a predetermined gear ratio by using selective engagement of friction members constituting a plurality of engagement elements, such as clutches and brakes; and a hydraulic pressure control apparatus for controlling a hydraulic pressure servo for engaging/releasing the frictional members of each engagement element of the transmission mechanism. The conventional circuit structure of the foregoing hydraulic-pressure control apparatus having a relatively small number of gear ratios is such that shift valves which are switched among the gear ratios are provided to correspond to the number of the gear ratios. Moreover, hydraulic pressure sequentially passes through the shift valves so as to be applied to a predetermined hydraulic pressure servo.
To meet requirements including a requirement for reducing fuel consumption, the number of the gear ratios of the automatic transmission has been increased. As a technique for increasing the number of gear ratios by combining a plurality of planetary gears, a technique has been disclosed in Japanese Patent Laid-Open No. 4-219553. The technique is to use a gear train constituted by combining a planetary gear for inputting reduced speed with a Ravigneaux-type planetary gear set. Thus, a small number of transmission elements and of engagement elements are able to realize six speeds in the forward direction and one speed in the reverse direction.
When the planetary gear transmission mechanism having the multiple gear ratios is controlled by a conventional circuit structure having shift valves, the number of valves undesirably increases. Thus, the cost is enlarged excessively. Moreover, the circuit structure becomes furthermore complicated, causing the size of the hydraulic-pressure control apparatus to be undesirably enlarged. Usually, the hydraulic-pressure control apparatus has a structure formed into a valve body which totally incorporates each of valves. The valve body is disposed in the side portion of the transmission mechanism. Therefore, when the size of the valve body is enlarged, the size of the transmission is correspondingly enlarged. As a result, easy mounting on the automatic transmission is inhibited. Therefore, simplification of the circuit structure free of shift valves is required.
The disclosed technique is such that a one-way clutch which is capable of mechanically shifting torque when the engagement element has been released is provided for only the first speed to realize a compact transmission. As a result, gear shift to the second or higher speed is realized by changing clutching of the friction engagement element by using control of the hydraulic pressure. The control of clutching must be performed with a satisfactory response of the hydraulic pressure servo such that either of the frictional engagement elements is engaged while the other frictional engagement element is released. To simplify the circuit structure and improve the controllability of each engagement element, it might be considered feasible to structure the hydraulic pressure circuit for controlling each engagement element. That is, a special control valve (a linear solenoid and a duty solenoid) is provided for each engagement element so as to be independently controlled.
Thus, shift of the gear to each gear ratio can be performed such that the frictional engagement element to be engaged and the frictional engagement element to be released can directly be controlled. Because each of the special control valves is provided, jump of shift is permitted. If breakdown of the solenoid of the control valve for controlling each engagement element occurs or a mistake of a signal is made, so-called interlocking occurs. That is, two or more frictional engagement elements, the engagement of which must be prevented, are engaged in a predetermined gear ratio. As a result, the durability of each frictional engagement element deteriorates.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide a hydraulic pressure control apparatus for an automatic transmission which is capable of overcoming the foregoing problems and which has a circuit structure permitting a jump of the gear ratio and enablement to prevent the occurrence of interlocking of the transmission mechanism.
To achieve the foregoing object, according to the invention, there is provided a hydraulic pressure control apparatus for an automatic transmission including a planetary gear transmission mechanism incorporating at least five engagement elements to selectively be engaged to realize a predetermined gear ratio; and a hydraulic-pressure control apparatus for controlling the engagement elements of the transmission mechanism so that when a first engagement element C-
1
and a fourth engagement element B-
3
are engaged, a first speed is realized; when the first engagement element C-
1
and a fifth engagement element B-
1
are engaged, a second speed is realized; when the first engagement element C-
1
and a third engagement element C-
3
are engaged, a third speed is realized; when the first engagement element C-
1
and a second engagement element C-
2
are engaged, a fourth speed is realized; when the second engagement element C-
2
and the third engagement element C-
3
are engaged, a fifth speed is realized; and when the second engagement element C-
2
and the fifth engagement element B-
1
are engaged, a sixth speed is realized, wherein the hydraulic-pressure control apparatus is provided with cutoff valves
75
,
76
,
77
,
78
for inhibiting combinations with which interlocking of the transmission mechanism occurs due to engagement of two or more engagement elements of the five engagement elements when each of the forward gear ratios including the first speed to the sixth speed has been realized.
Specifically, it is effective that the planetary gear transmission mechanism incorporates a planetary gear for inputting reduced speed and a planetary gear set for inputting reduced revolutions from the planetary gear for inputting the reduced speed, the first engagement element C-
1
is a first clutch for inputting the reduced revolutions to a first transmission element S
3
, the second engagement element C-
2
is a second clutch for inputting revolutions input from an engine to a second transmission element C
2
, C
3
, the third engagement element C-
3
is a third clutch for inputting reduced revolutions to a third transmission element S
2
of the planetary gear, the fourth engagement element B-
3
is a first brake for fixing the second transmission element C
2
, C
3
of the planetary gear, and the fifth engagement element B-
1
is a second brake for fixing the third transmission element S
2
of the planetary gear.
It is effective that the combinations with which interlocking of the transmission mechanism occurs when the forward gear ratio has been realized and which are inhibited incorporate a first pattern having combinations of two engagements and a second pattern having combinations of three engagements, the first pattern at least incorporates four combinations of engagements between the second engagement element C-
2
and the fourth engagement element B-
3
, between the third engagement element C-
3
and the fifth engagement element B-
1
, between the third engagement element C-
3
and the fourth engagement element B-
3
and between the fourth engagement element B-
3
and the fifth engagement element B-
1
, the second pattern incorporates two combinations of engagements among the first engagement element C-
1
, the second engagement element C-
2
and the third engagement element C-
3
and among the first engagement element C-
1
, the second engagement element C-
2
and the
Hisano Takayuki
Mae Toshiyuki
Suzuki Akitomo
Tsukamoto Kazumasa
Aisin AW Co. Ltd.
Ho Ha
Marmor Charles A
Oliff & Berridg,e PLC
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