Automatic transmission and hydraulic control method therefor
AssigneeJATCO Ltd
InventorsIkuhiro Iwamoto, Osamu Sato
Life of this patent
Estimating the term…
Abstract
A manual valve disconnects a line pressure oil passage and an R position pressure oil passage when a selector is in a D position or an N position and causes the R position pressure oil passage and the line pressure oil passage to communicate when the selector is in an R position. A switching valve is switched to disconnect a low & reverse brake pressure oil passage and the R position pressure oil passage when the selector is in the D position or the N position and a vehicle is driving at a vehicle speed equal to or lower than a predetermined vehicle speed.
Claims6
An automatic transmission which includes a planetary gear and a plurality of friction elements and realizes a plurality of gear positions by changing engaged states of the plurality of friction elements,
- the plurality of friction elements including a reverse friction element which is engaged when a selector is in an R position and released when the selector is in a D position in which an engine brake is not activated, the automatic transmission comprising:
- a hydraulic pressure source;
- a switching valve and a manual valve arranged between the hydraulic pressure source and the reverse friction element and adapted to switch oil passages in conjunction with a selector operation, the switching valve being switched later than the manual valve;
- a first oil passage connecting the reverse friction element and the switching valve;
- a second oil passage connecting the hydraulic pressure source and the manual valve;
- a third oil passage connecting the switching valve and the manual valve;
- and
- a control unit which controls the switching of the switching valve;
- wherein:
- the manual valve disconnects the second and third oil passages when the selector is in the D position or the N position and causes the second and third oil passages to communicate when the selector is in the R position;
- and
- the control unit switches the switching valve to disconnect the first and third oil passages when the selector is in the D position or the N position and a vehicle equipped with the automatic transmission is driving at a vehicle speed equal to or lower than a predetermined vehicle speed.
A hydraulic control method in an automatic transmission including a planetary gear, a plurality of friction elements including a reverse friction element which is engaged when a selector is in an R position and released when the selector is in a D position in which an engine brake is not activated, a hydraulic pressure source, a switching valve and a manual valve arranged between the hydraulic pressure source and the reverse friction element and adapted to switch oil passages in conjunction with a selector operation, the switching valve being switched later than the manual valve, a first oil passage connecting the reverse friction element and the switching valve, a second oil passage connecting the hydraulic pressure source and the manual valve, and a third oil passage connecting the switching valve and the manual valve, the manual valve disconnecting the second and third oil passages when the selector is in the D position or the N position and causing the second and third oil passages to communicate when the selector is in the R position, a plurality of gear positions being realized by changing engaged states of the plurality of friction elements, wherein
- switching the switching valve to disconnect the first and third oil passages when the selector is in the D position or the N position and a vehicle equipped with the automatic transmission is driving at a vehicle speed equal to or lower than a predetermined vehicle speed.
An automatic transmission which includes a planetary gear and a plurality of friction elements and realizes a plurality of gear positions by changing engaged states of the plurality of friction elements,
- the plurality of friction elements including a reverse friction element which is engaged when a selector is in an R position and released when the selector is in a D position in which an engine brake is not activated, the automatic transmission comprising:
- a hydraulic pressure source;
- a switching valve and a manual valve arranged between the hydraulic pressure source and the reverse friction element and adapted to switch oil passages in conjunction with a selector operation, the switching valve being switched later than the manual valve;
- a first oil passage connecting the reverse friction element and the switching valve;
- a second oil passage connecting the hydraulic pressure source and the manual valve;
- a third oil passage connecting the switching valve and the manual valve;
- and
- control means for controlling the switching of the switching valve;
- wherein:
- the manual valve disconnects the second and third oil passages when the selector is in the D position or the N position and causes the second and third oil passages to communicate when the selector is in the R position;
- and
- the control means switches the switching valve to disconnect the first and third oil passages when the selector is in the D position or the N position and a vehicle equipped with the automatic transmission is driving at a vehicle speed equal to or lower than a predetermined vehicle speed.
Dependencies are inferred from the claim text.