Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Reexamination Certificate
2002-06-12
2004-07-27
Lewis, Tisha D (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
C477S045000, C477S050000
Reexamination Certificate
active
06767309
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an automatic transmission comprising a ratio-change mechanism, which transmits the rotational driving force of a drive power source varying a speed ratio, and a forward/reverse direction-change mechanism, which changes the direction of the rotation of the driving force. Furthermore, the present invention relates to an automatic transmission that comprises a belt-type continuously variable speed control mechanism as ratio-change mechanism.
BACKGROUND OF THE INVENTION
Such an automatic transmission is designed for use in a vehicle to transmit the rotational driving force of an engine (drive power source) varying a speed ratio, in which the rotational speed being transmitted is controlled in correspondence to the throttle opening of the engine, the speed of the vehicle, etc. Such an automatic transmission generally comprises hydraulic actuators such as hydraulic clutches and brakes to achieve this speed ratio control. For example, an automatic transmission may comprise a belt-type continuously variable speed control mechanism disclosed in Japanese Laid-Open Patent Publication No. H08(1996)-178059. In this case, the automatic transmission comprises a clutch mechanism that transmits the driving force of the engine to the transmission, in addition to the belt-type continuously variable speed control mechanism, and these mechanisms are controlled by supplies of hydraulic pressure. While the shift lever is at “N” position, the clutch mechanism is released to set the transmission in neutral condition. When the shift lever is shifted from “N” position to “D” position, the clutch mechanism is engaged, and the continuously variable speed control mechanism is set in speed ratio control. In this instance, if the clutch mechanism is brought into engagement abruptly, then a shock may happen. To avoid such a shock, the hydraulic pressure supplied to the clutch mechanism is gradually increased by means of a solenoid valve.
By the way, another construction of automatic transmission is known, which transmission comprises a forward/reverse direction-change mechanism provided on the output side of the engine, a belt-type continuously variable speed control mechanism provided in connection to the forward/reverse direction-change mechanism, and a starting clutch mechanism connected to the output shaft of this continuously variable speed control mechanism. In this case, the starting clutch mechanism is used for controlling the power transmission to the drive wheels. When the shift lever is at “N” position (neutral range), the transmission is set in neutral condition. In this condition, the starting clutch mechanism is in disengagement, so the power transmission through the starting clutch mechanism is cut off. In addition, the forward/reverse direction-change mechanism is also disengaged in this condition.
In this automatic transmission, when the shift lever is shifted from “N” position to “D” position (for the forward drive range), the line pressure is led to the forward drive clutch that actuates the forward/reverse direction-change mechanism into engagement. At the same time, a pressure for starting control is supplied to the starting clutch to actuate it into engagement. In this way, the rotational direction of the driving force of the engine is set by the forward/reverse direction-change mechanism, the rotational speed to be transmitted is determined by the continuously variable speed control mechanism in speed ratio control, and the transmission of this rotation to the drive wheels is controlled by the starting clutch. Especially, the starting clutch is controlled appropriately to start the vehicle smoothly.
In this automatic transmission, however, as the pulleys comprising the continuously variable speed control mechanism have a relatively large inertia, when the forward/reverse direction-change mechanism is brought into engagement by the supply of the line pressure, the continuously variable transmission having a large inertia is connected to the output shaft of the engine. As a result, even though the starting clutch is disengaged, the whole of the power plant including the engine experiences a vibration as the engine tries to rotate the transmission against the large rotational inertia. This vibration is transmitted to the body of the vehicle, which supports the power plant, and induces a shaking of the vehicle body. As the rotational speed of the engine is reduced temporarily, a rotational vibration or a noise may also occur. These same problems may be also experienced when the shift lever is shifted from “N” position to “R” position (for the rearward drive range) or when the shift lever is shifted directly from “D” position to “R” position or from “R” position to “D” position.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a control system for an automatic transmission, which system can bring the forward/reverse direction-change mechanism into engagement smoothly, preventing any vibration or noise that may otherwise occur when the shift lever is operated in the above described ways.
According to the present invention, an automatic transmission comprises a ratio-change mechanism (for example, the metal V-belt mechanism
10
described in the following embodiment, another type of continuously variable transmission, a normal transmission, etc.), a forward/reverse direction-change mechanism (for example, the forward/reverse direction-change mechanism
20
described in the following embodiment, another type of forward/reverse direction-change mechanism, etc.) and a forward/reverse direction-change actuator (for example, the forward clutch
30
and the reverse brake
25
described in the following embodiment). The ratio-change mechanism transmits rotational driving force from a drive power source (for example, the engine ENG in the following embodiment) changing a speed ratio, and the forward/reverse direction-change mechanism switches the rotational direction of the rotational driving force transmitted from the drive power source through the ratio-change mechanism. The forward/reverse direction-change actuator, by receiving a hydraulic pressure, actuates the rotational direction switching operation of the forward/reverse direction-change mechanism. A control system for this automatic transmission comprises a regulator valve (for example, the regulator valve
50
described in the following embodiment), a manual switching valve (for example, the manual valve
80
described in the following embodiment) and a switching operation detector (for example, the drive-range sensor
105
described in the following embodiment). The regulator valve generates a line pressure by adjusting the pressure of a hydraulic pressure source, the manual switching valve is operated by an external factor, to switch the supply of oil at the line pressure to the forward/reverse direction-change actuator, and the switching operation detector detects the movement of the manual switching valve. When the movement of the manual switching valve to a position where the line pressure is to be supplied to the forward/reverse direction-change actuator is detected by the switching operation detector, the line pressure, which is adjusted by the regulator valve, is lowered for a predetermined time period immediately after this detection.
With this control system, for example, when the shift lever is manipulated from “N” position to “D” position to shift the manual switching valve from its N position to its D position, the line pressure adjusted by the regulator valve is supplied to the forward clutch (or to the reverse brake), which constitutes the forward/reverse direction-change mechanism, for the engagement of the forward clutch. In this instance, during the predetermined time period after the manual switching valve has set at the D position, the line pressure, which is adjusted by the regulator valve, is lowered to gradually engage the forward clutch. In this way, the ratio-change mechanism, which has a relatively large rotational inertia
Aoki Akihira
Fujimoto Shuichi
Saotome Hiroshi
Honda Giken Kogyo Kabushiki Kaisha
Lahive & Cockfield LLP
Laurentano Anthony A.
Lewis Tisha D
Nash Deborah
LandOfFree
Automatic transmission control system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Automatic transmission control system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automatic transmission control system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3185213