Patent ID: 12248328

DETAILED DESCRIPTION

An embodiment of a valve system is described below based uponFIGS.1to4. As shown inFIG.1, a valve system1has a tank2, a supply path3, and a supply destination7. The tank2forms a closed space for storing fluid. The supply path3connects the tank2to the supply destination7. The fluid in the tank2is supplied to the supply destination7via the supply path3. The valve system1has a valve4that can open and close the supply path3. When the valve4is opened, the fluid flows from the tank2to the supply destination7through the supply path3. The valve system1may be applied, for example, to a hydrogen fuel supply system that has a hydrogen tank and supplies hydrogen fuel to a fuel cell.

The valve system1has a control unit5and a pressure sensor6that measures the internal pressure P of the tank2. The control unit5is a computer system having at least one processor and at least one memory. The measurement signal from the pressure sensor6is input to the control unit5. The control unit5also outputs control signals to control the operating state of the valve4. The memory of the control unit5stores various programs and various data (including maps) for controlling the valve4. The control unit5has a plurality of circuits51. When the programs stored in the memory are executed by the processor, the corresponding circuits51carry out the control described below. For example, the control of fluid flow through valve4is one of the functions performed by the program being executed.

As shown inFIG.1, the valve4has a valve member11and a driving device (actuator) that moves the valve member11. The driving device has, for example, a stepper motor12and an output shaft13. The stepper motor12includes a rotor and a stator. The output shaft13is assembled with the valve member11. The output shaft13has male threads on its surface. The rotor of the stepper motor12has female threads. The male thread of the output shaft13is screwed with the female threads of the rotor of the stepper motor12. Therefore, the output shaft13moves in the axial direction (up and down) due to the rotation of the rotor As the output shaft13moves up and down, the valve member11also moves up and down.

A rubber-like sealing member14is provided on the underside of the valve member11. The sealing member14has an annular shape. When the valve member11is lowered by the stepper motor12, the sealing member14is pressed against the seat3aof the supply path3from above. This allows the valve member11to properly shut off the supply path3and seal the tank2. The valve member11is then raised and the sealing member14is separated from the seat3a, thereby bringing an upstream path3band a downstream path3cinto a continuous state. This allows fluid to flow from the tank2to the supply destination7.

The controller5can rotate the stepper motor12in the forward or reverse direction by controlling the number of steps. By rotating the stepper motor12in the forward or reverse direction for a predetermined number of steps, the valve member11moves a predetermined distance (stroke amount) in the vertical direction (open/close direction). In other words, the stroke amount of the valve member11can be adjusted by controlling the number of steps.

A method of controlling the rate of change of the tank internal pressure will be described. The flow rate of the fluid flowing from the tank2to the supply destination7depends on the amount of change per hour (rate of change R) of the internal pressure P of the tank2, which decreases with the opening of the valve4. Control of the flow rate can therefore be achieved by controlling the rate of change R of the internal pressure P of the tank2to be the target rate of change R0as explained below. Of course, the following method can also be used when the control of the rate of change R of the internal pressure P of the tank2is itself the objective.

FIG.2is a flowchart showing the routine of the process performed by the control unit5to control the rate of change R of the internal pressure P as one specific embodiment.FIGS.3and4are time charts each representing a control example. Each time chart represents, from the top, the internal pressure P of the tank2, the number of steps of the stepper motor12(i.e., the position of valve member11), the energized state of the stepper motor12, the time count while the stepper motor12is energized, and the time count while not energized, respectively. The internal pressure P of the tank2is measured at regular intervals by the pressure sensor6and is recorded in the control unit5.

One example of the control method will be described. Initially, the valve member11of the valve4is in the standby position, which has moved in the closing direction by a predetermined stroke amount from the opening position. First, it is determined whether a request to open the valve4has been issued (step S100). If the open valve request is not issued, this cycle is terminated. If the open valve request has been issued, the stepper motor12is energized (time ts). After energizing, the valve member11waits for a predetermined time Ta to prevent the stepper motor12from stalling (step S102). This can prevent the stepper motor12from stalling when the valve member11moves. While the stepper motor12is energized, a time count during energization is started.

Next, the valve member1lis continuously moved in the opening direction at a constant opening speed (e.g., 20 ms/step) (step S104). Then, it is determined whether the position (number of steps) of the moved valve member11exceeds the predetermined position (number of steps), which is presumed to be well beyond the valve opening position (the valve member11is sufficiently separated from the seat3a) even considering the dimensional tolerance of each component (step S106). If the valve member11has not exceeded the above predetermined position, it is determined whether the internal pressure P of the tank2from the start of energization (time ts) to the present time has decreased by the judgment standard pressure ΔP (e.g. 0.2 kPa) or more and whether the (average) rate of change R1of the internal pressure P from time ts to the present time exceeds the target rate of change R0(step S108).

If the internal pressure P has not decreased by more than the judgment standard pressure ΔP, or if the rate of change R1of the internal pressure P does not exceed the target rate of change R0even though the internal pressure P has decreased by more than the judgment standard pressure ΔP (that is, N in step S108), the process returns to step S104to continue moving the valve member11in the valve opening direction. If the internal pressure P has not decreased by more than the judgment standard pressure ΔP, but the position of the valve member11exceeds the predetermined position mentioned above, which is presumed to have already opened sufficiently if the valve is normal (i.e., N in step S106), the value of the abnormality counter A, which counts the valve4abnormality, is increased by 1 (step S128). Then, it is determined whether the value of the abnormality counter A is 2 or more (step S130). If the abnormality counter A is 2 or more, it is determined that an abnormality has occurred in the valve4(step S134) and this cycle is terminated. If the abnormality counter A is 1, the position of the valve member11is moved to the position where the number of steps of the stepper motor12becomes 0 (step S132). The process then returns to step S100.

If it is detected that the internal pressure P has decreased by more than the judgment standard pressure ΔP, and if the rate of change R1of the internal pressure P from time ts to the time of detection (time t1) exceeds the target rate of change R0, movement of the valve member11is stopped at that time. The judgment standard pressure ΔP can be set to a variable value proportional to the target rate of change R0of the internal pressure P (for example, 0.2 kPa, which is numerically equal to the target rate of change R0when R0is 0.2 kPa/s), but is not limited to this. For example, it can beset as a multiple (two times) of the resolution of the pressure sensor6(e.g., 0.1 kPa), or any other arbitrary value. The opening speed of the valve member11may be set to any desired speed.

Then, the value of the abnormality counter A is reset to 0 (step S110), and the valve member11is made to wait for a predetermined time b (e.g., 100 ms)(step S112). After the valve member11is made to wait for a predetermined time Tb, the valve member11is continuously moved in the closing direction at a constant closing speed (e.g., 20 ms/step) (step S114). Thus, by waiting for a predetermined time before reversing the valve member11from the open valve direction to the closed valve direction, the sudden change in the moving speed of the valve member11is suppressed. This can prevent the stepper motor12from stalling.

Next, when the valve member11reaches the standby position, movement of the valve member11is stopped and it was waited for a predetermined time Tc after the valve member11stops to prevent the stepper motor12from stalling (step S116). After the valve member11waits, the energizing of the stepper motor12is stopped (step S118).

Next, the elapsed time (energization duration) from the start of energization (time ts) to the stop of energization (time t2) is measured, and the (average) rate of change R2of the internal pressure P from time ts to time t2is calculated. Then, the calculated rate of change R2is compared with the target rate of change R0(step S120). If R2>R0, energization to the stepper motor12is stopped, as shown inFIG.3. Then, as shown inFIG.3, the stepper motor12waits in a de-energized state until the time t3when the stepper motor12is energized again (waiting time Td). The rate of change R of the internal pressure P can be adjusted by controlling the length of this waiting time Td. In other words, by providing the waiting time Td during which the internal pressure P does not change, the average rate of change R of the internal pressure P after the start of energization is reduced. The control unit5determines the waiting time Td so that the rate of change R3equals the target rate of change R0depending on the calculated rate of change R2of the internal pressure P up to time t2(step S122).

For example, if the energization duration is 1000 ms, the change in the internal pressure P is 0.4 kPa, and the target rate of change R0is 0.2 kPa/s, the waiting time Td is determined to be 1000 ms. This means that the (average) rate of change R3of the internal pressure P from time ts to time t3is calculated as below.
R3=0.4 kPa/(1000+1000)ms=0.2 kPa/s
The (average) rate of change R3becomes equal to the target rate of change R0. Thus, the control unit5can adjust the rate of change R of the internal pressure P by adjusting the elapsed time using the waiting time Td (step S126). After adjusting the rate of change R, the process returns to step S100.

If R2≤R0in step S120, the waiting time Td is set to 0 and the process proceeds to step S126(step S124), as shown inFIG.4. In this case, since the waiting time Td is 0, the process returns to step S100without waiting.

As another embodiment, in step S108, if the rate of change R1of the internal pressure P is less than the target rate of change R0when the amount of change in the internal pressure P reaches the judgment standard pressure ΔP, the valve member11may be stopped moving to continue the open valve state. At that time, the time count during energization may be reset and the rate of change R of the internal pressure P may be calculated by measuring the change in the internal pressure P from that point. In step S108, the process may proceed to step S110when the amount of change in the internal pressure P decreases by mom than the judgment standard pressure ΔP, regardless of the rate of change R1in the internal pressure P.

To summarize the above description, the valve system1has the tank2capable of storing fluid, the pressure sensor6that detects the internal pressure P of the tank2, the valve4that has the valve member11and opens and closes the tank2, the driving device (stepper motor12) to stroke the valve member11of the valve4, and the control unit5. The control unit5is configured to move the valve member11of the valve4in the opening direction after the cycle starts, reverse the direction of movement of the valve member11of the valve4to the standby position in the closed valve state, calculate the first pressure change rate R2, which is the rate of change R of the internal pressure P since the cycle started, and determine the waiting time such that the second pressure change rate R3, which is the rate of change R of the internal pressure P from the start of the cycle to the end of the cycle, is equal to the target rate of change R0if the first pressure change rate R2is greater than the target change rate R0, and keep the driving device (stepper motor12) in the standby position until the determined waiting time has elapsed.

In accordance with this configuration, even if the internal pressure P of the tank2cannot be matched to the target rate of change R0by adjusting the opening amount of the valve4, the average rate of change R of the internal pressure P can be matched to the target rate of change R0by adjusting the waiting time in the closed valve state for each cycle. This enables accurate control of the valve system1.

The control unit5is configured to reverse the direction of movement of the valve member11of the valve4when the pressure sensor6detects that the internal pressure P of the tank2has decreased by a certain value. This configuration allows the rate of change R of the internal pressure P to be controlled more precisely by ensuring a sufficient amount of change in the internal pressure P.

The control unit5is configured to set the waiting time to 0 when the first pressure change rate R2is equal to or less than the target change rate R0. This configuration allows the process to proceed in a responsive manner.

If the control unit5calculates the third pressure change rate R1, which is the rate of change R of the internal pressure P since the cycle started before reversing the direction of movement after moving the valve member11of valve4in the open valve direction, and keeps the valve open state without reversing the direction of movement of the valve4if the third pressure change rate R1is equal to or less than the target change rate R0. This configuration allows the direction of movement of valve4not to be reversed in vain when the rate of change R of the internal pressure P is small.

The energization of the driving device (stepper motor12) is started at the beginning of a cycle and is ended at the beginning of the waiting time, and the rate of change R is calculated based on the energization time of the driving device unit (stepper motor12). This configuration makes it easy to manage the time when calculating the rate of change R by using the energizing or de-energizing of the highly responsive driving device (stepper motor12) as the standard.

The driving device is composed of the stepper motor12. This configuration improves the accuracy of control even when the stepper motor12, which generally requires a waiting time to prevent stalling, is used as the driving device. In addition, manufacturing costs and power consumption can be reduced compared to the same control using a solenoid valve.

The valve system1described above can be applied to a hydrogen fuel supply system as well as, for example, an evaporative fuel treatment system with a fuel tank to store fuel and a canister to adsorb fuel vapor that evaporates from the fuel tank. The valve system can be widely applied to any other system with a tank for storing fluid and a valve for opening and closing the tank.

As another embodiment, the start of the cycle and the start of the waiting time do not necessarily have to coincide with the start or end of energization, but may be set arbitrarily. The time for calculating the rate of pressure change can also be set independently of the energization time.

In the above embodiment, the rate of change R1of the internal pressure P until the decrease in the judgment reference pressure ΔP is detected was used to determine whether the valve4should be reversed in the closed valve direction. But as another embodiment, for example, the rate of change R of the internal pressure P until any other appropriate point in time, such as when a certain time has passed from the start of energization or the start of the valve member11movement, may also be used.

As another embodiment, the driving device may be a linear solenoid, a DC motor system, etc., in addition to a stepper motor. Other devices that can electrically drive the valve member may be used.

Allfeaturesdisclosedinthedescriptionand/ortheclaimsareintendedtobedisclosedasinfonrational, instructive and/or representative and may thus be construed separately and independently from each other. In addition, all value ranges and/or indications of groups of entities are also intended to include possible intermediate values and/or intermediate entities for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.