US 5,675,317 AGranted

Residual pressure sensor and residual pressure sensor monitoring apparatus

AssigneesNagano Keiki Seisakusho, Ltd., The Nippon Signal Co., Ltd.

InventorsMasato Ichikawa, Koichi Futsuhara, Masayoshi Sakai

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Abstract

A residual pressure sensor for verifying that a residual pressure is zero, and to a monitoring apparatus for monitoring for faults in the residual pressure sensor. In order to detect that a residual pressure has completely gone, the residual pressure sensor detects change conditions in the output therefrom, and an output for no residual pressure is not generated while there are changes. Moreover, an electrical power supply condition to a drive solenoid (21) of a solenoid valve for opening/closing a pressure supply line, is monitored using a fail-safe current sensor (21) which outputs a logic value "0" when the presence of a current is detected, and which outputs a logic value "1" when the presence of a current is not detected. Fault monitoring of the residual pressure sensor is then carried out based on the monitoring output conditions of the current sensor and the output conditions of the residual pressure sensor.

Claims23

Dependent claims

A residual pressure sensor incorporating a pressure sensing pipe with one end closed such that the closed end is displaced with an increase/decrease in pressure introduced from another end opening, and a pressure-electricity converter section which detects the displacement location of the closed end of the pressure sensing pipe and at the time of a pressure increase, decreases an electrical output in accordance with displacement of the closed end, and at the time of a pressure decrease, increases an electrical output in accordance with displacement of the closed end comprising;

an electrical output change detection means for detecting whether or not the electrical output from said pressure-electricity converter section has a changing condition, and generating a low level output in the event of a changing condition, and a high level output in the event of a constant condition, and
a fail-safe first logical product operating means for carrying out a logical product operation on an output from said electrical output change detection means and an output from said pressure-electricity converter section, and generating an output of logic value "1" corresponding to a high level indicating no residual pressure, when both outputs are at a high level equal to or above a predetermined value, and generating an output of logic value "0" corresponding to a low level, at the time of a fault.

A residual pressure sensor monitoring apparatus, applicable to a system incorporating a pressure supply control means for carrying out pressure supply to a movable section of a machine at the time of electrical power supply and for stopping pressure supply at the time of no electrical power supply, which monitors that there is no pressure supply to said movable section of the machine using a residual pressure sensor incorporating a pressure sensing pipe with one end closed such that the closed end is displaced with an increase/decrease in pressure introduced from another end opening, and a pressure-electricity converter section which detects the displacement location of the closed end of the pressure sensing pipe and at the time of a pressure increase, decreases an electrical output in accordance with displacement of the closed end, and at the time of a pressure decrease, increases an electrical output in accordance with displacement of the closed end, said residual pressure sensor monitoring apparatus being for monitoring if the operation condition of said residual pressure sensor is normal or abnormal, said residual pressure sensor monitoring apparatus comprising;

a current sensor which monitors the electrical power supply condition of said pressure supply control means, and generates a low level output of logic value "0" at the time of electrical power supply, and generates a high level output of logic value "1" at the time of no electrical power supply, and generates an output of logic value "0" at the time of a fault,
a fail-safe NOT operating means which carries out a NOT operation on the logical output from said residual pressure sensor, which generates a low level output of logic value "0" at the time of supply pressure to the movable section of the machine, and a high level output of logic value "1" at the time of no supply pressure, and generates an output of logic value "0" at the time of a fault, and which generates a low level output of logic value "0" at the time of a fault, and
judgement means for judging if there is a residual pressure sensor fault based on respective logical outputs from said current sensor and said NOT operating means, and when both logical outputs are logic value "0", generates a low level output of logic value "0" indicating a fault in the residual pressure sensor.

Dependencies are inferred from the claim text.