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Evaporated fuel treatment device of internal combustion engineRelated Patent Categories: Measuring And Testing, Motor And Engine Testing, Testing Auxiliary UnitEvaporated fuel treatment device of internal combustion engine description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060162433, Evaporated fuel treatment device of internal combustion engine. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This is a division of application Ser. No. 10/700,669 filed 5 Nov. 2003, which claims priority to Japanese Patent Application No. 2002-321687 filed 5 Nov. 2002, the contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an evaporated fuel treatment device, and more particularly to an evaporated fuel treatment device for treating evaporated fuel generated in a fuel tank without emitting it to the atmosphere. [0004] 2. Background Art [0005] A conventional evaporated fuel treatment device disclosed, for instance, by JP-A No. 2001-342914 is equipped with a canister that communicates with a fuel tank. This device is also equipped with a purge path for introducing an intake negative pressure into the canister as well as a bypass path that is positioned between the fuel tank and canister for introducing a negative pressure into the fuel tank. The bypass path is provided with a bypass control valve, which controls the continuity of the bypass path. [0006] If an open failure occurs in the bypass control valve of the above conventional device, the continuity between the canister and the fuel tank cannot be cut so that normal operations cannot be assured. Therefore, the above conventional device has a function for detecting an open failure in the bypass control valve by a method described below. [0007] More specifically, when the above conventional device needs to detect an open failure in the bypass control valve, it first issues a valve close instruction to the bypass control valve while introducing an intake negative pressure into the canister. Next, the conventional device monitors a canister internal pressure and tank internal pressure to check whether the tank internal pressure significantly follows a change in the canister internal pressure. [0008] If the bypass control valve is properly closed, the bypass control valve shuts off the intake negative pressure introduced into the canister. In this instance, therefore, the tank internal pressure does not follow the canister internal pressure. If, on the other hand, the bypass control valve is open in spite of the issued valve close instruction, the intake negative pressure introduced into the canister is also introduced into the fuel tank. As a result, the tank internal pressure significantly follows a change in the canister internal pressure. [0009] Therefore, if the tank internal pressure does not significantly follow a change in the canister internal pressure, the above conventional device concludes that the bypass control valve is normal. If, on the other hand, the tank internal pressure significantly follows a change in the canister internal pressure, the above conventional device concludes that an open failure exists in the bypass control valve. As described above, the foregoing conventional device is capable of judging in accordance with the changes in the canister internal pressure and tank internal pressure whether an open failure exists in the bypass control valve. [0010] In the above conventional device, however, the tank internal pressure varies not only with the introduction of intake negative pressure but also with fuel consumption and evaporated fuel generation. To accurately judge whether the tank internal pressure adequately follows a change the canister internal pressure, it is necessary to remove the influence of fuel consumption and evaporated fuel generation. In reality, therefore, it is necessary to exercise complicated control so as to yield an accurate diagnostic check result concerning an open failure in the bypass control valve by a method employed by the above conventional device. SUMMARY OF THE INVENTION [0011] The present invention is made to solve the foregoing problems, and has for its object to provide an evaporated fuel treatment device that is capable of exercising simple control to conduct an accurate diagnostic check for an open failure in a valve mechanism provided in path joining the canister and fuel tank. [0012] The above object of the present invention is achieved by an evaporated fuel treatment device for internal combustion engine that uses a canister to absorb evaporated fuel generated in a fuel tank for evaporated fuel treatment purposes. The device includes a sealing valve for controlling the continuity between the fuel tank and the canister. The device also includes a differential pressure detection unit for detecting the difference between a canister side pressure and a tank internal pressure. The device further includes an open failure normality judgment unit for judging that no open failure exists in the sealing valve when the differential pressure detection unit detects a differential pressure higher than a judgment value. [0013] The above object of the present invention is also achieved by an evaporated fuel treatment device for internal combustion engine that uses a canister to absorb evaporated fuel generated in a fuel tank for evaporated fuel treatment purposes. The device includes a sealing valve for controlling the continuity between the fuel tank and the canister. The device also includes a differential pressure generation condition judgment unit for judging whether a differential pressure generation condition is established. The condition is established when the sealing valve is expected to be closed and differential pressure is expected to be generated between both sides of the sealing valve. A condition establishment differential pressure detection unit is provided for detecting the difference between a canister side pressure and a tank internal pressure when the differential pressure generation condition is established. The device judges that an open failure exists in the sealing valve when the condition establishment differential pressure detection unit does not detect a differential pressure greater than a judgment value. [0014] The above object of the present invention is achieved by an evaporated fuel treatment device for internal combustion engine that uses a canister to absorb evaporated fuel generated in a fuel tank for evaporated fuel treatment purposes. The device includes a sealing valve for controlling the continuity between the fuel tank and the canister. A close failure judgment unit is provided for judging whether a close failure exists in the sealing valve. A pressure introduction unit is provided for introducing pressure into either the canister or the fuel tank in a situation where the sealing valve is closed. A sealing valve open instruction generation unit is also provided for issuing a valve open instruction to the sealing valve in a situation where pressure is introduced into either the canister or the fuel tank by the pressure introduction unit. A check is conducted before and after the issuance of the valve open instruction to judge whether a significant pressure change occurs in the canister or the fuel tank to which pressure is not introduced. The device makes a judgment that an open failure exists in the sealing valve when the significant pressure change is not verified by the pressure change judgment unit under a circumstance where no close failure record exists. [0015] Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0016] FIGS. 1A and 1B are drawings for describing a structure of a first embodiment of the present invention; [0017] FIG. 2 is a flowchart of a control routine executed in the first embodiment of the present invention; [0018] FIGS. 3A through 3D are timing diagrams for describing principal of open failure diagnosis conducted on a sealing valve in a second embodiment of the present invention; and [0019] FIG. 4 is a flowchart of a control routine executed in the second embodiment of the present invention. BEST MODE OF CARRYING OUT THE INVENTION [0020] Now, embodiments of the present invention will be described with reference to the drawings. Like reference numerals denote like components throughout the drawings, and redundant descriptions will be omitted. 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