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:
Mar. 02, 1999
Filed:
Feb. 12, 1996
Tatsuo Wakahara, Kawasaki, JP;
Kenichiro Murakami, Atsugi, JP;
Nissan Motor Co., Ltd., Yokohama, JP;
Abstract
A hydraulic-pressure control system for a four-wheel drive vehicle with a hydraulic-pressure operated transfer clutch, which is responsive to a controlled clutch pressure applied thereto to distribute a driving torque passing from a transmission between main drive wheels and auxiliary drive wheels, comprises a pilot-operated directional control valve connected to the transfer clutch for cutting off a supply of hydraulic fluid of the controlled clutch pressure to the transfer clutch and for directing hydraulic fluid of the controlled clutch pressure to the transfer clutch. The system includes a clutch pressure control valve provided upstream of the directional control valve, which pressure control valve is responsive to an external pilot pressure for producing the controlled clutch pressure, and a duty-ratio controlled solenoid valve for decreasingly adjusting the external pilot pressure to be output to the pressure-reduction valve in accordance with an increase in a duty ratio. A controller is provided for forcibly outputting a duty-cycle controlled exciting current of a predetermined high duty ratio such as 100% to the duty-ratio controlled solenoid valve to reduce the controlled clutch pressure to a low pressure level (preferably a minimum clutch pressure) when the directional control valve is maintained at the cut-off position in case of 4L range wherein the transmission is loaded heavier.