VALVE SYSTEM

Abstract

Valve system (1) comprising: a tank (2) configured to store fluid; a pressure sensor (6) configured to detect an internal pressure of the tank (2); a valve (4) with a valve element (11) configured to open and close the tank (2); a drive device configured to move the valve element (11); and a control unit (5) comprising at least one circuit (51), wherein the at least one circuit (51) is configured to: move the valve element (11) in a valve opening direction after the start of a cycle; reverse a direction of movement of the valve element (11) and move the valve element (11) to a ready position in a valve closing state; calculate an initial pressure change rate (R2), which is a rate of change in the internal pressure since the cycle began;to determine a waiting time (Td) such that a second pressure change rate (R3), which is a change rate of the internal pressure from the start to an end of the cycle, is equal to a target change rate (R0) if the first pressure change rate (R2) is greater than the target change rate (R0); and to hold the drive device in the ready position until the predetermined waiting time (Td) has elapsed.

Description

BACKGROUND

[0001] This disclosure generally relates to valve systems.

[0002] A vehicle, such as an automobile, with an internal combustion engine is equipped with an evaporative fuel treatment system. The evaporative fuel treatment system generally includes a fuel tank, a canister that adsorbs fuel vapor (vapour) generated in the fuel tank, and a vapor passage connecting the fuel tank and the canister. The vapor passage is equipped with a sealing valve. The sealing valve is normally closed to block communication between the fuel tank and the canister. The sealing valve is opened only when necessary to allow fuel vapor to flow to the canister and adsorb the fuel vapor to the canister. JP-A-183677 discloses a conventional valve system.In the valve system, a stepper motor is driven to adjust the valve element opening amount based on the flow rate estimated from the amount of change in the internal pressure of the fuel tank. By controlling the amount of change in the internal pressure, the flow rate of fuel vapor sent from the fuel tank to the canister is controlled.

[0003] In general, if the drive device (actuator) for moving the valve element is not sufficiently responsive after receiving an operating signal, it cannot be controlled accurately. Furthermore, when using a stepper motor, there is a limitation to fine-tuning the valve element opening amount, as it is necessary to provide a waiting time to prevent jamming when reversing the direction of valve element movement. Therefore, there has been a need for improved valve systems. SUMMARY

[0004] In one aspect of the present disclosure, a valve system includes a tank configured to store a fluid, a pressure sensor configured to detect an internal pressure of the tank, a valve having a valve element configured to open and close the tank, a drive device configured to move the valve element, and a control unit having at least one circuit.The at least one circuit is configured to move the valve element in a valve opening direction after starting a cycle, reverse a movement direction of the valve element and move the valve element to a standby position in a valve closing state, calculate a first pressure change rate, which is a change rate in the internal pressure since the cycle started, determine a waiting time such that a second pressure change rate, which is a change rate of the internal pressure from the start to an end of the cycle, is equal to a target change rate if the first pressure change rate is greater than the target change rate, and hold the drive device in the standby position until the determined waiting time has elapsed. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of one embodiment of a valve system according to the principles described herein. Fig. 2 is a flowchart showing the routine of the process for controlling the rate of change at a tank pressure of the valve system of Fig. 1 shows. Fig. Figure 3 is a time diagram for the case where the rate of change at a pressure R2 up to the point after valve closure is greater than the target rate of change R0. Fig. 4 is a time diagram for the case where the rate of change R2 is less than or equal to the target rate of change R0. DETAILED DESCRIPTION

[0005] An embodiment of a valve system is shown below based on Fig. 1 to 4. As described in Fig. 1, a valve system 1 includes a tank 2, a supply path 3, and a supply destination 7. The tank 2 forms a closed space for storing fluid. The supply path 3 connects the tank 2 to the supply destination 7. The fluid in the tank 2 is supplied to the supply destination 7 via the supply path 3. The valve system 1 includes a valve 4 that can open and close the supply path 3. When the valve 4 is open, the fluid flows from the tank 2 to the supply destination 7 through the supply path 3. The valve system 1 can be applied, for example, to a hydrogen fuel supply system that includes a hydrogen tank and supplies hydrogen fuel to a fuel cell.

[0006] The valve system 1 includes a control unit 5 and a pressure sensor 6 that measures the internal pressure P of the tank 2. The control unit 5 is a computer system having at least one processor and at least one memory. The measurement signal from the pressure sensor 6 is input to the control unit 5. The control unit 5 also outputs control signals for controlling the operating state of the valve 4. The memory of the control unit 5 stores various programs and various data (including maps) for controlling the valve 4. The control unit 5 includes a plurality of circuits 51. When the programs stored in the memory are executed by the processor, the corresponding circuits 51 perform the control described below. For example, controlling a fluid flow through the valve 4 is one of the functions performed by the program when it is executed.

[0007] As in Fig. 1, the valve 4 includes a valve element 11 and a drive device (actuator) that moves the valve element 11. The drive device includes, for example, a stepper motor 12 and an output shaft 13. The stepper motor 12 includes a rotor and a stator. The output shaft 13 is assembled with the valve element 11. The output shaft 13 has external threads on its surface. The rotor of the stepper motor 12 has internal threads. The external thread of the output shaft 13 is screwed to the internal threads of the rotor of the stepper motor 12. Therefore, the output shaft 13 moves in the axial direction (up and down) due to the rotation of the rotor. As the output shaft 13 moves up and down, the valve element 11 also moves up and down.

[0008] A rubber-like sealing element 14 is provided on the underside of the valve element 11. The sealing element 14 has an annular shape. When the valve element 11 is lowered by the stepping motor 12, the sealing element 14 is pressed from above against the seat 3a of the supply path 3. This allows the valve element 11 to properly block the supply path 3 and seal the tank 2. The valve element 11 is then lifted, and the sealing element 14 is separated from the seat 3a, thereby bringing an upstream path 3b and a downstream path 3b into a continuous state. This allows fluid to flow from the tank 2 to the supply destination 7.

[0009] The controller 5 can rotate the stepping motor 12 in the forward or reverse direction by controlling the number of steps. By rotating the stepping motor 12 in the forward or reverse direction for a predetermined number of steps, the valve element 11 moves a predetermined distance (stroke amount) in the vertical direction (opening / closing direction). In other words, the stroke amount of the valve element 11 can be adjusted by controlling the number of steps.

[0010] A method for controlling the rate of change of the tank's internal pressure will be described. The flow rate of the fluid flowing from the tank 2 to the supply destination 7 depends on the amount of change per hour (change rate R) of the internal pressure P of the tank 2, which decreases with the opening of the valve 4. Therefore, flow rate control can be achieved by controlling the rate of change R of the internal pressure P of the tank 2 to be the target change rate R0, as explained below. Of course, the following method can also be used when controlling the rate of change R of the internal pressure P of the tank 2 itself is the goal.

[0011] Fig. 2 is a flowchart showing the routine of the process performed by the control unit 5 for controlling the change rate R of the internal pressure P as a specific embodiment. Fig. 3 and Fig. 4 are timing charts, each illustrating a control example. Each timing chart represents, from the top, the internal pressure P of the tank 2, the number of steps of the stepping motor 12 (i.e., the position of the valve element 11), the power supply state of the stepping motor 12, the time count while the stepping motor 12 is energized, and the time count while it is de-energized, respectively. The internal pressure P of the tank 2 is measured by the pressure sensor 6 at regular intervals and recorded in the control unit 5.

[0012] An example of the control method will be described. Initially, the valve element 11 of the valve 4, which has moved from the open position by a predetermined stroke amount in the closing direction, is in the standby position. First, it is determined whether a request to open the valve 4 has been made (step S100). If the valve opening request has not been made, this cycle is ended. If the valve opening request has been made, the stepping motor 12 is energized (time ts). After energization, the valve element 11 waits for a predetermined time Ta to prevent the stepping motor 12 from locking (step S102). This can prevent the stepping motor 12 from locking when the valve element 11 is moving. While the stepping motor 12 is energized, a time count during energization is started.

[0013] Next, the valve element 11 is 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 element 11 exceeds the predetermined position (number of steps) which is assumed to be well beyond the valve opening position (the valve element 11 is sufficiently separated from the seat 3a), even when the dimensional tolerance of each component is taken into account (step S106). If the valve element 11 has not exceeded the above predetermined position, it is determined whether the internal pressure P of the tank 2 has decreased by the judgment standard pressure ΔP (e.g., 0.2 kPa) or more from the energization start (time ts) to the present time, and whether the (average) change rate R1 of the internal pressure P from time ts to the present time exceeds the target change rate R0 (step S108).

[0014] If the internal pressure P has not decreased by more than the judgment standard pressure ΔP, or if the change rate R1 of the internal pressure P does not exceed the target change rate R0 even if the internal pressure P has decreased by more than the judgment standard pressure ΔP (ie, N in step S108), the process returns to step S104 to continue moving the valve element 11 in 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 element 11 exceeds the predetermined position mentioned above, at which it is assumed to have already opened sufficiently if the valve is normal (ie, N in step S106), the value of the abnormality counter A counting the valve 4 abnormality is incremented 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 valve 4 (step S134), and this cycle is ended. If the abnormality counter A is 1, the position of the valve element 11 is moved to the position where the number of steps of the stepping motor 12 becomes 0 (step S132). The process then returns to step S100.

[0015] If it is detected that the internal pressure P has decreased by more than the judgment standard pressure ΔP, and if the change rate R1 of the internal pressure P from time ts to the detection time (time t1) exceeds the target change rate R0, movement of the valve element 11 at that time is stopped. The judgment standard pressure ΔP can be set to a variable value proportional to the target change rate R0 of the internal pressure P (for example, 0.2 kPa, which is numerically equal to the target change rate R0 when R0 is 0.2 kPa / s), but is not limited to this. For example, it can be set to a multiple (twice) of the resolution of the pressure sensor 6 (for example, 0.1 kPa) or any other value. The opening speed of the valve element 11 can be set to a desired speed.

[0016] Then, the value of the abnormality counter A is reset to 0 (step S110), and the valve element 11 is made to wait for a predetermined time Tb (e.g., 100 ms) (step S112). After the valve element 11 is made to wait for a predetermined time Tb, the valve element 11 is 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 the valve element 11 is reversed from the valve-opening direction to the valve-closing direction, the sudden change in the moving speed of the valve element 11 is suppressed. This can prevent the stepping motor 12 from locking.

[0017] Next, when the valve element 11 reaches the standby position, movement of the valve element 11 is stopped, and a predetermined time Tc is waited after the valve element 11 stops to prevent the stepping motor 12 from locking (step S116). After the valve element 11 waits, the power supply to the stepping motor 12 is stopped (step S118).

[0018] Next, the elapsed time (power supply period) from the power supply start (time ts) to the power supply stop (time t2) is measured, and then the (average) change rate R2 of the internal pressure P from time ts to time t2 is calculated. Then, the calculated change rate R2 is compared with the target change rate R0 (step S120). If R2 > R0, power supply to the stepping motor 12 is stopped, as shown in Fig. 3. Then wait, as shown in Fig. 3, the stepping motor 12 is in a de-energized state until time t3 when the stepping motor 12 is energized again (waiting time Td). The change rate 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 change rate R of the internal pressure P after the energization start is reduced. The control unit 5 determines the waiting time Td depending on the calculated change rate R2 of the internal pressure P up to time t2 so that the change rate R3 is equal to the target change rate R0 (step S122).

[0019] For example, if the power supply period is 1000 ms, the change in the internal pressure P is 0.4 kPa, and the target change rate R0 is 0.2 kPa / s, the waiting time Td is determined to be 1000 ms. This means that the (average) change rate R3 of the internal pressure P from time ts to time t3 is calculated as below. R3=0.4 kPa / (1000+1000)ms=0.2 kPa / s

[0020] The (average) change rate R3 becomes equal to the target change rate R0. Thus, the control unit 5 can adjust the change rate R of the internal pressure P by adjusting the elapsed time using the waiting time Td (step S126). After adjusting the change rate R, the process returns to step S100.

[0021] If in step S120 R2 ≤ R0, the waiting time Td is set to 0 and the process proceeds to step S126 (step S124), as shown in Fig.4. In this case, since the waiting time Td is 0, the process returns to step S100 without waiting.

[0022] As another embodiment, in step S108, if the change rate R1 of the internal pressure P is smaller than the target change rate R0 when the change amount in the internal pressure P reaches the judgment standard pressure ΔP, the valve element 11 may be stopped from moving to continue the valve-opening state. At this time, the time count during power supply may be reset, and the change rate R of the internal pressure P may be calculated by measuring the change in the internal pressure P from this point. In step S108, if the change amount in the internal pressure P decreases by more than the judgment standard pressure ΔP, the process may proceed to step S110.

[0023] Summarizing the above description, the valve system 1 comprises the tank 2 capable of storing fluid, the pressure sensor 6 detecting the internal pressure P of the tank 2, the valve 4 having the valve element 11 and opening and closing the tank 2, the drive device (stepping motor 12) for lifting the valve element 11 of the valve 4, and the control unit 5.The control unit 5 is configured to move the valve element 11 of the valve 4 in the opening direction after the cycle starts, reverse the moving direction of the valve element 11 of the valve 4 to the standby position in the valve closed state, calculate the first pressure change rate R2, which is the change rate R of the internal pressure P since the cycle is started, and determine the waiting time such that the second pressure change rate R3, which is the change rate R of the internal pressure P from the start of the cycle 2 to the end of the cycle 2, is equal to the target change rate R0 if the first pressure change rate R2 is greater than the target change rate R0, and keep the drive device (stepping motor 12) in the standby position until the predetermined waiting time has elapsed.

[0024] According to this configuration, even if the internal pressure P of the tank 2 cannot be adjusted to the target change rate R0 by adjusting the opening degree of the valve 4, the average change rate R of the internal pressure P can be adjusted to the target change rate R0 by adjusting the waiting time in the closed valve state for each cycle. This enables precise control of the valve system 1.

[0025] The control unit 5 is configured to reverse the direction of movement of the valve element 11 of the valve 4 when the pressure sensor 6 detects that the internal pressure P of the tank 2 has decreased by a certain amount. 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.

[0026] The control unit 5 is configured to set the waiting time to 0 when the first pressure change rate R2 is equal to or less than the target change rate R0. This configuration allows the process to proceed in a responsive manner.

[0027] If the control unit 5 calculates the third pressure change rate R1, which is the change rate R of the internal pressure P since the cycle is started before the movement direction is reversed, after the valve element 11 of the valve 4 is moved in the valve-opening direction, and maintains the valve-opening state without reversing the movement direction of the valve 4 if the third pressure change rate R1 is equal to or smaller than the target change rate R0. This configuration allows the movement direction of the valve 4 not to be reversed in vain when the change rate R of the internal pressure P is small.

[0028] The power supply to the drive device (stepping motor 12) is started at the beginning of a cycle and stopped at the beginning of the waiting time, and the change rate R is calculated based on the power supply time of the drive device unit (stepping motor 12). This configuration makes it easier to manage the time when the change rate R is calculated using the power supply or non-power supply of the highly responsive drive device (stepping motor 12) as the standard.

[0029] The drive device consists of the stepper motor 12. This configuration improves control accuracy even when the stepper motor 12, which generally requires a waiting time to prevent jamming, is used as the drive device. Furthermore, manufacturing costs and power consumption can be reduced compared to the same control using a solenoid valve.

[0030] The valve system 1 described above can be applied to a hydrogen fuel supply system, as well as, for example, an evaporative fuel treatment system having a fuel tank for storing fuel and a canister for adsorbing fuel vapor evaporating from the fuel tank. The valve system can be widely applied to another system having a tank for storing fluid and a valve for opening and closing the tank.

[0031] 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 the power supply, but can be set arbitrarily. The time for calculating the pressure change rate can also be set independently of the power supply time.

[0032] In the above embodiment, the change rate R1 of the internal pressure P until the decrease in the judgment reference pressure ΔP is detected was used to determine whether the valve 4 should be reversed in the valve closing direction. However, as another embodiment, for example, the change rate R of the internal pressure P until another appropriate time, such as when a certain time has elapsed from the start of power supply or the start of valve element 11 movement, may also be used.

[0033] As another embodiment, the drive 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 element may be used.

[0034] All features disclosed in the description and / or claims are intended to be disclosed as informative, educational, and / or representative, and thus may be understood as separate and independent of each other. Furthermore, all ranges of values ​​and / or indications of groups of objects are also intended to encompass possible intermediate values ​​and / or intermediate objects for the purpose of original written disclosure, as well as for the purpose of limiting the claimed subject matter. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 183677 A

[0002]

Claims

[1] Valve system (1), with: a tank (2) designed to store fluid, a pressure sensor (6) designed to detect an internal pressure of the tank (2); a valve (4) with a valve element (11) designed to open and close the tank (2); a drive device adapted to move the valve element (11); and a control unit (5) with at least one circuit (51), in which the at least one circuit (51) is designed to: to move the valve element (5) in a valve opening direction after the start of a cycle; to reverse a direction of movement of the valve element (11) and to move the valve element (11) to a standby position in a valve closing state; calculate a first pressure change rate, which is a rate of change in the internal pressure since the cycle began; determining a waiting time such that a second pressure change rate, which is a change rate of the internal pressure from the start to an end of the cycle, is equal to a target change rate if the first pressure change rate is greater than the target change rate; and to keep the drive device in the standby position until the predetermined waiting time has elapsed. [2] Valve system (1) according to claim 1, wherein the control unit (5) is designed to reverse the direction of movement of the valve element (11) when the pressure sensor (6) detects that the internal pressure of the tank (2) has decreased by a certain value. [3] Valve system (1) according to claim 1 or 2, wherein the control unit (5) is designed to set the waiting time to 0 when the first pressure change rate is less than or equal to the target change rate. [4] Valve system (1) according to one of claims 1 to 3, wherein the control unit (5) is designed to: to calculate a third pressure change rate, which is a change rate of the internal pressure since the cycle is started, after the valve element (11) is moved in the valve opening direction and before the direction of movement is reversed; and to keep the valve (4) in an open state without reversing the direction of movement of the valve element (11) if the third pressure change rate is less than or equal to the target change rate. [5] Valve system (1) according to one of claims 1 to 4, wherein the control unit (5) is configured to start a power supply to the drive device at the start of the cycle, to stop a power supply at the start of the waiting time, and to calculate the change rate based on a power supply time of the drive device. [6] Valve system (1) according to one of claims 1 to 5, wherein the drive device comprises a stepper motor (12).