The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 13, 1979
Filed:
Jul. 27, 1976
Takahiro Sakai, Toyota, JP;
Toyota Jidosha Kogyo Kabushiki Kaisha, Toyota, JP;
Abstract
A hydraulic pressure control device for use, for example, in an automatic transmission, in which a line pressure to be supplied from a hydraulic pressure source to a hydraulic pressure servo-device is controlled in three stages by means of a main spool which is displaced in a bleed-off valve of the line pressure by a subsidiary spool under a varying hydraulic control pressure. The subsidiary spool has at least one land forming a piston slidingly fitted in a movable sleeve having a closed end, the movable sleeve also forming a piston by being in turn slidingly fitted for limited movement in a stationary sleeve having a closed end. A first space between the outer wall of the closed end of the movable sleeve and the inner wall of the closed end of the stationary sleeve, and a second space within the piston chamber of the movable sleeve have ports for the introduction of hydraulic control pressure. A spring is confined between the subsidiary spool and the movable sleeve with an initial load for urging the movable sleeve away from the main spool and minimizing the first space. The initial load on the spring and the diameter of the spaces are so determined that an increasing hydraulic control pressure displaces only the spools until the product of the control pressure and the difference in the areas of the cross sections of the spaces exceeds the initial load on the spring. Further increase of the control pressure displaces both the movable sleeve and the subsidiary spool to the limit of movement of the movable sleeve, the movement of the spools being a function of the strain on the spring. Further increase of the control pressure acts to move only the subsidiary spool and thereby the main spool. The control device preferably includes a second land on the subsidiary spool operating in an additional space of larger diameter in the movable sleeve and an annular space between the movable sleeve and the stationary sleeve. Both the additional space and the annular space are accessed to a second control pressure for additional displacement of the subsidiary spool and thereby of the main spool.