Planetary gear transmission systems or components – Fluid drive or control of planetary gearing – Fluid controlled mechanical clutch or brake
Reexamination Certificate
2000-06-21
2002-03-26
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
06361465
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control device of an automatic transmission for vehicles.
2. Description of the Prior Art
A conventional control device of an automatic transmission for vehicles is disclosed, for example, in Japanese Patent Application Laid-open Publication No. 2-304256. This automatic transmission comprises a main transmission mechanism arranged coaxially with a torque converter and a sub transmission mechanism arranged in parallel with the main transmission mechanism. In this automatic transmission, the control device achieves a plurality of gear positions by engaging and disengaging friction elements such as planetary gear mechanisms, clutches, brakes and one-way clutches.
In the control device of the automatic transmission, an automatic transmission control unit (hereinafter referred to as an ATCU) determines a gear position suitable for driving conditions, and on-off controls solenoid valves in the control device, thereby switching shift valves by an oil pressure supplied through the solenoid valves. The gear positions are changed by supplying and releasing oil pressure to and from friction elements by the shift valves.
An ordinary control device has a parking range, a rear driving range (hereinafter referred to as a R range), a neutral range, an automatic shift driving range (hereinafter referred to as a D range), a 3 range in which a vehicle is driven forward at a first, second or third speed gear position, a 2 range in which the vehicle is driven forward at the first or second speed gear position, a 1 range in which the vehicle is driven forward only at the first speed gear position.
The conventional control device of the automatic transmission switches the gear position from the fourth speed to the third speed by switching the sub transmission mechanism from a direct driven state to a reduction state. More specifically, the control device shifts the gear position from the fourth speed down to the third speed by disengaging a direct clutch that is engaged at the fourth speed gear position and engaging a reduction one-way clutch and a reduction brake that are unengaged at the fourth speed gear position.
An engagement pressure of the reduction brake is controlled by supply and release of an oil pressure due to the gear shift, and also can be controlled gradually for a predetermined time through a reduction accumulator provided in an oil channel which supplies and releases the engagement pressure.
The gear position is shifted from the fourth speed down to the third speed by an automatic down shift in the D range or a manual down shift in a case the 3 range is manually-selected.
Normally, the manual down-shift is performed in such a manner that a driver manually operates a shift lever for the purpose of driving the vehicle with an engine brake being operable. The reduction brake must be engaged upon the disengagement of the direct clutch in order to prevent the delay in functioning the engine brake. In this case, a high back pressure is supplied to the reduction accumulator to generate a high shelf pressure and stroke the reduction accumulator. Since the engagement pressure of the reduction brake is raised quickly, the reduction brake is engaged while the reduction accumulator is stroking. Consequently, the reduction brake is engaged just after the manual down-shift operation.
In the case of the automatic down-shift in the D range, it is necessary to direct the driving power from an input shaft to an output shaft since the driver would not like to drive the vehicle with the engine brake being operable. When the direct clutch is disengaged, the reduction one-way clutch is engaged to carry on the transmission of power for forward driving. This prevents a trouble in the shift even if the engagement of the reduction brake is delayed. Therefore, the back pressure is not supplied to the reduction accumulator, and the reduction accumulator is stroked at a low shelf pressure. The reduction brake engagement pressure is kept low for a predetermined time to delay the engagement of the reduction brake. This surely prevents the shock resulting from the shift.
Either in the manual down-shift or in the automatic down-shift, a line pressure is supplied directly to the reduction brake after a finish of the stroke of the reduction accumulator so that the reduction brake can be kept engaged.
If the R range is selected in the above prior art automatic transmission, the R range pressure is supplied as the back pressure to the reduction accumulator to maintain the state wherein the reduction accumulator has finished stroking. Thus, the line pressure is directly supplied to the reduction brake to cope with a large loaded torque in backward driving. A pressure regulating valve for reducing pressure is provided in an oil channel that supplies the engagement pressure to the low reverse brake in order to adjust the shock resulting from the shift.
However, the engagement pressure of the reduction brake must be kept low for a time required for the shift plus an allowance in order to surely prevent the shock resulting from the shift by delaying the engagement of the reduction brake in the automatic down-shift. The time in which the accumulator can control the oil pressure corresponds to the time in which the accumulator is stroking, and thus depends on the capacity of the accumulator. For this reason, the reduction accumulator must be quite large in order to keep the low engagement pressure of the reduction brake for a sufficient time. On the other hand, the vehicle is recently equipped with an increasing number of devices, and there is a strong requirement for reducing the size of each device. It is therefore necessary to reduce the size of the control device of the automatic transmission.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a control device of an automatic transmission, which prevents the shock resulting from the shift in the automatic down-shift and is capable of quickly changing gear positions in the manual down-shift. It is another object of the present invention to provide a control device of an automatic transmission, which is capable of engaging friction elements by a sufficient engagement pressure in backward driving. It is yet another object of the present invention to provide a small control device of an automatic transmission.
The above objects can be accomplished by providing a control device of an automatic transmission, which comprises a plurality of forward driving gear positions and a backward driving gear position that are achieved by engaging and disengaging a plurality of friction elements and which is capable of changing the plurality of forward driving gear positions by an automatic shift or a manual shift according to driving conditions, the control device of the automatic transmission comprising: a first friction element that is engaged at least at a lowest speed forward driving gear position or at the backward driving gear position; a pressure regulating valve that is connected to an output oil channel connected to a first oil channel connected to the first friction element, a second oil channel supplied with an original pressure, a third oil channel that is drained if the forward driving gear position is designated and that is supplied with a rear range pressure if the backward driving gear position is designated, and a fourth oil channel supplied with an oil pressure for changing pressure regulating state, the pressure regulating valve outputting the rear range pressure to the output oil channel if the third oil channel is supplied with the rear range pressure, outputting an oil pressure regulated to such an extent as not to engage the first friction element to the output oil channel if the third oil channel is drained and the fourth oil channel is not supplied with oil pressure, and outputting an oil pressure regulated according to the oil pressure supplied to the fourth oil channel if the third oil channel is drained and the fourth oil channel is supp
Jatco Transtechnology Ltd.
Marmor Charles A.
Parekh Ankur
Rossi & Associates
LandOfFree
Control device of 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 Control device of automatic transmission, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control device of automatic transmission will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2858534