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:
May. 25, 1999
Filed:
Jun. 05, 1997
Denso Corporation, , JP;
Abstract
A hydraulic pressure control system for an automatic transmission is capable of reducing the size and simplifying the structure of a lockup controlling hydraulic circuit. An oil pressure output from a solenoid valve acts on an oil pressure chamber. The internal pressure of another oil pressure chamber becomes high only in a forward low-speed range and becomes low in all of the other gear shift ranges. The internal pressure of another oil pressure chamber becomes high only in forward ranges and becomes low in neutral and reverse ranges. The valve member moves in accordance with oil pressures applied to the oil pressure chambers to change over oil paths connected to a clutch control oil chamber and a torque converter oil chamber, whereby a lockup clutch assumes one of engaged, slip, and released states. Since an oil pressure signal according to a gear shift range and a vehicular running range is fed to the changeover valve and on the basis of this signal the changeover valve determines whether the engagement of the lockup clutch is to be permitted or inhibited, the circuit of a lockup control unit can be reduced in size and simplified.