An evaporated fuel processing device utilizing a flow rate control valve as a valve positioned in a passage connecting a fuel tank with a canister. The device includes: a valve opening means for opening the flow rate control valve at a constant speed; an internal pressure sensor; a valve opening sta
An evaporated fuel processing device utilizing a flow rate control valve as a valve positioned in a passage connecting a fuel tank with a canister. The device includes: a valve opening means for opening the flow rate control valve at a constant speed; an internal pressure sensor; a valve opening start position detecting means for acquiring a second derivative value of the internal pressure after a valve opening motion of the flow rate control valve has started and for detecting a valve opening start position of the flow rate control valve based on the second derivative value; a learning means for storing the valve opening start position; and a valve opening speed change means for changing a valve opening speed of the valve opening means based on a variation speed of the internal pressure before the valve opening motion of the flow rate control valve has started.
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1. An evaporated fuel processing device configured to adsorb evaporated fuel within a fuel tank in a canister and supply the adsorbed evaporated fuel to an engine, utilizing a flow rate control valve as a valve positioned in a passage connecting the fuel tank with the canister, which is maintained i
1. An evaporated fuel processing device configured to adsorb evaporated fuel within a fuel tank in a canister and supply the adsorbed evaporated fuel to an engine, utilizing a flow rate control valve as a valve positioned in a passage connecting the fuel tank with the canister, which is maintained in a valve closed state when a stroke amount representing an axially traveled distance of a movable valve part relative to a valve seat from an initial state of the flow rate control valve is less than or equal to a predetermined amount from an initial state so as to allow the fuel tank to be maintained in a sealed state, the evaporated fuel processing device comprising: a valve opening means for opening the flow rate control valve from the valve closed state at a predetermined speed;an internal pressure sensor for detecting a space pressure within the fuel tank as an internal pressure;a valve opening start position detecting means for acquiring a second derivative value of the internal pressure detected by the internal pressure sensor after a valve opening motion of the flow rate control valve has started, and for detecting a valve opening start position of the flow rate control valve based on the second derivative value;a learning means for storing the valve opening start position detected by the valve opening start position detecting means as a learned value when valve opening control of the flow rate control valve is performed; anda valve opening speed change means for changing a valve opening speed of the valve opening means based on a variation speed of the internal pressure detected by the internal pressure sensor. 2. The evaporated fuel processing device of claim 1, wherein the valve opening means is configured to increase a valve opening amount of the flow rate control valve stepwise by a predetermined amount in a predetermined cycle, andthe valve opening speed change means is configured to change the predetermined cycle for increasing the valve opening amount by the valve opening means in response to the variation speed of the internal pressure. 3. The evaporated fuel processing device of claim 1, wherein the valve opening means is configured to increase a valve opening amount of the flow rate control valve stepwise by a predetermined amount in a predetermined cycle, wherein the valve opening amount is further increased by a predetermined period of time as a time for maintaining the valve opened at a timing when the valve opening amount is stepwise increased, andthe valve opening speed change means is configured to change the time for maintaining the valve opened by the valve opening means in response to the variation speed of the internal pressure. 4. The evaporated fuel processing device of claim 1, wherein the valve opening speed change means is configured to change the valve opening speed by the valve opening means based on the variation speed of the internal pressure detected by the internal pressure sensor before start of the valve opening motion of the flow rate control valve by the valve opening means. 5. The evaporated fuel processing device of claim 1, wherein the valve opening speed change means is configured to reduce the valve opening speed in response to acceleration in increasing speed of the internal pressure. 6. The evaporated fuel processing device of claim 2, wherein the valve opening speed change means is configured to extend the predetermined cycle by the valve opening means in response to acceleration in increasing speed of the internal pressure. 7. The evaporated fuel processing device of claim 3, wherein the valve opening speed change means is configured to increase the time for maintaining the valve opened by the valve opening means in response to acceleration in increasing speed of the internal pressure. 8. The evaporated fuel processing device of claim 3, wherein the valve opening speed change means is configured to extend the predetermined cycle by the valve opening means in response to acceleration in increasing speed of the internal pressure. 9. An evaporated fuel processing device configured to adsorb evaporated fuel within a fuel tank in a canister and supply the adsorbed evaporated fuel to an engine of a vehicle, utilizing a flow rate control step-motor-type closing valve as a valve positioned in a passage connecting the fuel tank with the canister, which is maintained in a valve closed state when a stroke amount representing the axially traveled distance of a movable valve part relative to a valve seat from an initial state of the valve is less than or equal to a predetermined amount so as to allow the fuel tank to be maintained in a sealed state, the evaporated fuel processing device comprising: an internal pressure sensor for detecting a space pressure within the fuel tank as an internal pressure;an electronic control unit comprising a control circuit with controller logic electronically connected to both the internal pressure sensor as well as a stepping motor for rotating an output shaft of a motor in the forward or reverse directions, wherein a male threaded portion is formed on the outer peripheral surface of the output shaft of the stepping motor and is screwed into a female threaded portion on a tube shaft portion of a valve guide of the closing valve, whereby through controlling rotation of the output shaft and the threaded connection of the shaft with the closing valve, the control circuit is able to open the flow rate control valve from a closed state of the valve, at a predetermined speed, wherein said speed comprises a set amount of rotation of the output shaft of the motor per period of time;wherein the control circuit is configured to perform a learning control process routine for learning the valve opening start position of the step-motor-type closing valve, wherein in said routine, the control circuit commences a valve opening motion by rotation of the output shaft of the motor, opening the closing valve from an initial closed state of the valve, wherein after a valve opening motion has started, the valve opening start position corresponds to the position where the valve opens to a degree such that the fuel tank can start communication with the canister due to the closing valve in the passage being open to a sufficient degree where the fuel can pass through, where said value is stored by the control circuit; wherein after the valve opening motion has started, the control circuit uses a second derivative of the internal pressure detected by the internal pressure sensor in calculating a pressure variation and comparing it to an initial tank pressure variation measured by the internal pressure sensor before the valve is opened, in finding the valve opening start position. 10. The evaporated fuel processing device of claim 9, wherein the device uses the stored value of the valve opening start position for subsequent valve opening control by the motor when the vehicle is parking for faster opening and faster communication between the fuel tank and the canister, compared to the opening of the valve prior to the learning of said value. 11. The evaporated fuel processing device of claim 10, wherein the learning process control routine of the control circuit comprises the initial tank pressure variation, wherein the valve is then cyclically opened based on a monitoring time selected proportional to the prior measured tank pressure variation speed, wherein the valve is opened a predetermined amount by the motor, the tank pressure is measured and a counter is started for the duration of the monitoring time, where once the counter reaches a predetermined value marking the end of the monitoring time, the tank pressure is measured again, and the differential variation in pressure over the period of monitoring time is determined, and compared to the initially measured tank pressure variation, such that, if the difference is greater than or equal to a predetermined value, then the total opening amount is stored as the valve opening start position, but where, if the difference is less than the predetermined value, then the cycle of steps starting after the determination of monitoring time is repeated until the difference is greater than or equal to the predetermined value. 12. The evaporated fuel processing device of claim 10, wherein the air-fuel ratio of the air-fuel mixture supplied to the engine of the vehicle is used by the control circuit together with the fuel tank internal pressure detected by the internal pressure sensor for comparing the pressure variation after the monitoring time period with the initial pressure variation in determining the valve opening start position. 13. The evaporated fuel processing device of claim 11, wherein after the valve opening motion has started, the control circuit uses the second derivative of the internal pressure detected by the internal pressure sensor in calculating the pressure variation and comparing it to the initial pressure variation, in finding the valve opening start position. 14. The evaporated fuel processing device of claim 11, wherein the air-fuel ratio of the air-fuel mixture supplied to the engine of the vehicle is used by the control circuit together with the fuel tank internal pressure detected by the internal pressure sensor for comparing the pressure variation after the monitoring time period with the initial pressure variation in determining the valve opening start position. 15. The evaporated fuel processing device of claim 11, wherein in the selection of monitoring time, if the initial pressure variation over time is increasing, then the monitoring time is for a longer duration, whereas if the initial pressure variation over time is decreasing, then the monitoring time is for a shorter duration. 16. The evaporated fuel processing device of claim 11, wherein the monitoring time comprises a first portion and a second portion, wherein the first portion comprises a period of time where the valve is opened a certain amount, wherein the second portion comprises a period of time where the valve is closed an amount such that it is opened to a greater degree than before the monitoring period but to a lesser degree than the amount opened in the first portion.
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