METHOD FOR OPERATING A CONTROL VALVE

Abstract

A method for operating a control valve using an HVAC actuator is described, the method comprises a circuit of the HVAC actuator executing the steps of: monitoring (S1) a rotation angle (ϕ) associated with a drive torque (M.sub.drive) applied by the HVAC actuator for moving the valve member; detecting (S2) a blocking of the control valve, if the applied drive torque (M.sub.drive) effects a change of the rotation angle (Δϕ) which is smaller than a threshold angle (ϕ.sub.th); upon detection of the blocking, controlling the HVAC actuator to repeatedly change the applied drive torque (M.sub.drive) between a first torque value (M1) and a second torque value (M2); and controlling the HVAC actuator to periodically modulate (S4) the first torque value (M1) between a third torque value and a fourth torque.

Claims

1. A method for operating a control valve (2) using an HVAC actuator (1), the control valve (2) comprising a valve member (21) for regulating a fluid flow through the control valve (2), the method comprising a circuit (11) of the HVAC actuator (1) executing the steps of: monitoring a rotation angle (ϕ) associated with a drive torque (M.sub.drive) applied by the HVAC actuator (1) for moving the valve member (21); detecting a blocking of the control valve (2), if the applied drive torque (M.sub.drive) effects a change of the rotation angle (Δϕ) which is smaller than a threshold angle (ϕ.sub.th); upon detection of the blocking, controlling the HVAC actuator (1) to repeatedly change the applied drive torque (M.sub.drive) between a first torque value (M1) and a second torque value (M2) smaller than the first torque value (M1); and controlling the HVAC actuator (1) to periodically modulate the first torque value (M1) between a third torque value (M3) and a fourth torque value (M4) smaller than the third torque value (M3).

2. The method according to claim 1, wherein the fourth torque value (M4) is larger than the second torque value (M2).

3. The method according to claim 1, wherein the third torque value (M3) is equal to the first torque value (M1).

4. The method according to claim 1, wherein the first torque value (M1) or the third torque value (M3) is equal to a maximally applicable drive torque of the HVAC actuator (1).

5. The method according to claim 1, wherein the second torque value (M2) is equal to a holding torque value required to keep the valve member (21) at a specific position.

6. The method according to claim 1, wherein the circuit (11) controls the HVAC actuator (1) to modulate the first torque value (M1) by a rectangular modulation signal.

7. The method according to claim 6, wherein the duty cycle of the rectangular modulation signal is equal to 0.5 or deviates from 0.5.

8. The method according to claim 1, wherein the circuit (11) controls the HVAC actuator (1) to modulate the first torque value (M1) by a triangular or a sawtooth modulation signal.

9. The method according to claim 1, wherein the circuit (11) controls the HVAC actuator (1) to deactivate periodic modulation of the first torque value (M1) within a first range (c2) of the rotation angle (ϕ) from a closed position of the control valve (2).

10. The method according to claim 1, wherein the circuit (11) controls the HVAC actuator (1) to deactivate periodic modulation of the first torque value (M1) within a second range (o2) of the rotation angle (ϕ) up to a fully open position of the control valve (2).

11. The method according to claim 1, wherein the circuit (11) controls the HVAC actuator (1) to terminate periodic modulation of the first torque value (M1), if the change of the rotation angle (Δϕ) effected by the applied drive torque (M.sub.drive) exceeds the threshold angle (ϕ.sub.th).

12. The method according to claim 1, wherein the circuit (11) controls the HVAC actuator (1) to interrupt the repeated changing of the applied drive torque (M.sub.drive) between the first torque value (M1) and the second torque value (M2) after a defined number (M.sub.def) of increases of the applied drive torque (M.sub.drive) to the first torque value (M1), if the blocking of the control valve (2) persists, and to return to the second torque value (M2).

13. The method according to claim 1, wherein the circuit (11) controls the HVAC actuator (1) to repeatedly change the applied drive torque (M.sub.drive) between the first torque value (M1) and the second torque value (M2) with a first frequency and to modulate the first torque value (M1) between the third torque value (M3) and the fourth torque value (M4) with a second frequency larger than the first frequency.

14. An HVAC actuator (1) for moving a valve member (21) of a control valve (2) to regulate a fluid flow through the control valve (2), the HVAC actuator (1) comprising a circuit (11) configured to: monitor a rotation angle (ϕ) associated with a drive torque (M.sub.drive) applied by the HVAC actuator (1) for moving the valve member (21); detect a blocking of the control valve (2), if the applied drive torque (M.sub.drive) effects a change of the rotation angle (Δϕ) which is smaller than a threshold angle NO; upon detection of the blocking, control the HVAC actuator (1) to repeatedly change the applied drive torque (M.sub.drive) between a first torque value (M1) and a second torque value (M2) smaller than the first torque value (M1); and to control the HVAC actuator (1) to periodically modulate the first torque value (M1) between a third torque value (M3) and a fourth torque value (M4) smaller than the third torque value (M3).

15. A non-transitory computer-readable medium having stored thereon computer program code which, when executed by a circuit (11) of an HVAC actuator (1), such that the circuit (11) executes the steps of: monitoring a rotation angle (ϕ) associated with a drive torque (M.sub.drive) applied by the HVAC actuator (1) for moving a valve member (21) of a control valve (2); detecting a blocking of the control valve (2), if the applied drive torque (M.sub.drive) effects a change of the rotation angle (Δϕ) which is smaller than a threshold angle (ϕ.sub.th); upon detection of the blocking, controlling the HVAC actuator (1) to repeatedly change the applied drive torque between a first torque value (M1) and a second torque value (M2) smaller than the first torque value (M1); and controlling the HVAC actuator (1) to periodically modulate the first torque value (M1) between a third torque value (M3) and a fourth torque value (M4) smaller than the third torque value (M3).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be explained in more detail, by way of example, with reference to the drawings, in which:

[0034] FIG. 1 shows a graph illustrating the temporal course of an applied drive torque and a rotation angle;

[0035] FIG. 2 shows a flow diagram illustrating an exemplary sequence of steps of monitoring a rotation angle, detecting a blocking of the control valve, and changing the applied drive torque between a first torque value and a second torque value;

[0036] FIG. 3 shows a flow diagram illustrating an exemplary sequence of steps of modulating the first torque value;

[0037] FIG. 4 shows a flow diagram illustrating an exemplary sequence of steps of modulating the first torque value, wherein the modulation is terminated, if the change of the rotation angle exceeds a threshold angle;

[0038] FIG. 5 shows a flow diagram illustrating an exemplary sequence of steps of changing the applied drive torque between the first torque value and the second torque value, wherein the repeated changing of the applied drive torque is interrupted after a defined number of increases of the applied drive torque to the first torque value, if the blocking of the control valve persists;

[0039] FIG. 6 shows a graph illustrating the temporal course of the applied drive torque and the rotation angle where an overload procedure is applied to a blocked control valve;

[0040] FIG. 7 shows a graph illustrating the temporal course of the applied drive torque in a range where the first drive torque value is modulated;

[0041] FIG. 8 shows a graph illustrating the ranges near a fully closed position and a fully open position of the control valve where periodic modulation of the first drive torque value is deactivated; and

[0042] FIG. 9 shows a block diagram illustrating an HVAC actuator mounted onto a control valve.

DESCRIPTION OF THE EMBODIMENTS

[0043] FIG. 9 shows a block diagram illustrating an HVAC actuator 1 mounted onto a control valve 2. The HVAC actuator 1 comprises a circuit 11 configured to execute the steps of the overload procedure as described in FIGS. 2-7. Depending on the embodiment, the circuit 11 of the HVAC actuator 1 comprises components such as one or more microcontrollers, ASICs (Application Specific Integrated Circuits), (programmed) microprocessors and/or other electronic circuitry. The control valve 2 comprises a valve member 21 which is moved by the HVAC actuator 1 or an electric motor of the HVAC actuator 1, respectively. A blocking of the control valve 2 or the valve member 21, respectively, may be released by the circuit 11 of the HVAC actuator executing steps of an overload procedure, as described below in more detail.

[0044] FIG. 1 shows a graph illustrating the temporal course of a drive torque M.sub.drive applied by an electric motor of the HVAC actuator 1 and an associated rotation angle ϕ for moving the valve member 21 of the control valve 2, if no blocking of the control valve 2 occurs. The circuit 11 monitors the rotation angle ϕ and controls the HVAC actuator 1 such that a required rotation angle ϕ.sub.req is achieved by the applied drive torque M.sub.drive. The solid curve shows the temporal course of the drive torque M.sub.drive, whereas the dashed line shows the temporal course of the rotation angle ϕ. In the region denoted by a, an increase of the applied drive torque M.sub.drive leads to a corresponding increase of the rotation angle 4. In the shown example, the valve member 21 of the control valve 2 is moved from an open position to a fully closed position. The increase of the rotation angle ϕ exhibits two regions a1 and a2. In region a1, the valve member 21 is moved with a high velocity which is reflected by a steep increase of the rotation angle 4. In region a2, the valve member 21 is moved into a range near a closed position of the control valve 2 where the velocity of moving the valve member 21 is lower due to one or more sealing elements of the control valve 2. This is reflected by a decrease of the slope of increase of the rotation angle ϕ. The drive torque M.sub.drive is increased until point b where the drive torque M.sub.drive reaches a closing torque M5. After the rotation angle ϕ has reached a value where the control valve 2 is closed, the drive torque M.sub.drive assumes a holding torque in region c required to keep the valve member 21 in the closed position. For the control valve 2 not being blocked, as shown in FIG. 1, it can be recognized that a monotonous increase of the applied drive torque M.sub.drive leads to a monotonous increase of the rotation angle ϕ, although the slope of the rotation angle varies for different positions of the valve member 21.

[0045] FIG. 2 shows a flow diagram illustrating an exemplary sequence of steps executed by the circuit 11 of the HVAC actuator 1 for monitoring a rotation angle 4, detecting a blocking of the control valve 2, and changing the applied drive torque M.sub.drive between a first torque value M1 and a second torque value M2. In step S1, the rotation angle ϕ associated with the drive torque M.sub.drive applied by the HVAC actuator 1 for moving the valve member 21 is monitored. In step S2, a blocking of the control valve 2 is detected by checking the criterion Δϕ<ϕ.sub.th in step S21, i.e. whether the change of the rotation angle effected by the applied drive torque M.sub.drive is smaller than a defined threshold angle ϕ.sub.th. The threshold angle ϕ.sub.th may be defined for a specific test drive torque which should effect a change of the rotation angle Δϕ to be larger than the threshold angle ϕ.sub.th, if the control valve 2 is not blocked. Therefore, a change of the rotation angle Δϕ effected by the test drive torque smaller than the threshold angle ϕ.sub.th is indicative of a blocking of the control valve 2. In step S3, the applied drive torque M.sub.drive is repeatedly changed between the first torque value M1 and the second torque value M2. The first torque value M1 may be equal to a maximally applicable drive torque of the HVAC actuator 1. The second torque value M2 may be equal to a holding torque of the HVAC actuator 1 such as to keep the valve member 21 at a specific position, e.g. at the rotation angle where the blocking has occurred. The repeated change of the drive torque M.sub.drive is started in step S31 by setting the drive torque M.sub.drive to the first torque value M1. Once the drive torque M.sub.drive has reached the first torque value M1, the first torque value M1 is modulated between a third torque value and a fourth torque value in step S4. As already mentioned, the drive torque M.sub.drive may not exactly reach the first torque value M1 before the modulation of the first torque value M1 starts. The circuit 11 of the HVAC actuator 1 may be configured to allow for a certain tolerance range for the first torque value M1 within which the applied drive torque M.sub.drive is considered to have reached the first torque value M1. The circuit 11 of the HVAC actuator 1 may accordingly be configured to allow for suitable tolerance ranges for the second torque value M2, the third torque value and the fourth torque value. After a defined number of periods of the modulation of the first torque value M1 has been performed, the applied drive torque M.sub.drive returns to the second torque value M2 in step S32. After assuming the second torque value M2 for a defined period of time, which may be equal to the period of time the applied drive torque M.sub.drive is set to the first torque value M1 or where modulation of the first torque value M1 is performed, respectively, the cycle is started again by the circuit 11 of the HVAC actuator 1 executing step S31. It is clear to the person skilled in the art that the cycle can also start with step S32 after a blocking of the control valve 2 is detected in step S2.

[0046] In an embodiment, the circuit 11 detects, before detecting a blocking in step S2, if a required rotation angle is not reached, in spite of a suitably applied drive torque M.sub.drive. The required rotation angle ϕ.sub.req may not be reached for example due to dirt in the control valve 2, without the control valve 2 being blocked, i.e. without fulfilling the criterion of step S21. In particular, the movement of the valve member 21 may be slowed down, as reflected by the rotation angle not reaching the required value ϕ.sub.req. In said embodiment, the circuit 11 controls the HVAC actuator 1 to increase the applied drive torque M.sub.drive to M1 in order to overcome the slowdown of the movement of the valve member 21, such that the required rotation angle ϕ.sub.req may be reached again. After increasing the applied drive torque M.sub.drive to M1, the circuit 11 may execute step S2 in order to detect if a blocking of the control valve 2 has occurred.

[0047] FIG. 3 shows a flow diagram illustrating an exemplary sequence of steps executed by the circuit 11 of the HVAC actuator 1 for modulating the first torque value M1 in step S4. Modulation of the first torque value M1 is performed by alternatingly setting the drive torque M.sub.drive to the third torque value M3 and the fourth torque value M4 in a periodic fashion.

[0048] FIG. 4 shows a flow diagram illustrating an exemplary sequence of steps executed by the circuit 11 of the HVAC actuator 1 for modulating the first torque value M1 in step S4, wherein the modulation is terminated, if the change of the rotation angle Δϕ exceeds the threshold angle ϕ.sub.th. A change of the rotation angle Δϕ which exceeds the threshold angle ϕ.sub.th is indicative of successful release of the blocking of the control valve 2. For the shown example, the circuit 11 of the HVAC actuator 1 is configured to check the criterion Δϕ≥ϕ.sub.th in step S43, after setting the drive torque M.sub.drive to M4. If the change of the rotation angle Δϕ exceeds the threshold angle ϕ.sub.th, the modulation of the first torque value M1 is terminated and normal operation of the control valve 2 is resumed.

[0049] FIG. 5 shows a flow diagram illustrating an exemplary sequence of steps executed by the circuit 11 of the HVAC actuator 1 for changing the applied drive torque M.sub.drive between the first torque value M1 and the second torque value M2, wherein the repeated changing of the applied drive torque M.sub.drive is interrupted after a defined number N.sub.def of increases of the applied drive torque M.sub.drive to the first torque value M1, if the blocking of the control valve 2 persists. The circuit 11 of the HVAC actuator 1 is configured to check the criterion Δϕ<ϕ.sub.th in step S33 after setting the drive torque M.sub.drive to M1 in step S31. If the change of the rotation angle Δϕ exceeds the threshold angle ϕ.sub.th, the circuit 11 of the HVAC actuator 1 considers the blocking of the control valve 2 to be released and controls the HVAC actuator 1 to resume normal operation in step S6. If the blocking of the control valve 2 persists, i.e. the criterion Δϕ<ϕ.sub.th is fulfilled, the circuit 11 of the HVAC actuator 1 proceeds to checking the criterion N.sub.inc>N.sub.def in step S34, i.e. to check whether the number of increases N.sub.inc of the drive torque M.sub.drive is larger than the defined number N.sub.def of increases of the applied drive torque M.sub.drive to the first torque value M1. The HVAC actuator 1 may comprise a storage, e.g. memory, where the current number of increases of the drive torque M.sub.drive to the first torque value M1 is stored after step S31. If the number of increases N.sub.inc is larger than the defined number of increases N.sub.def, the repeated changing of the applied drive torque M.sub.drive is interrupted by setting the applied drive torque M.sub.drive to the second torque value M2 in step S7. After a certain waiting time, the overload procedure including the repeated change of the applied drive torque M.sub.drive between the first torque value M1 and the second torque value M2 may be resumed. In case step S34 results in the criterion N.sub.inc>N.sub.def to be not fulfilled, i.e. the number of increases N.sub.inc not exceeding the defined number of increases N.sub.def, the circuit 11 of the HVAC actuator 1 proceeds with modulation of the first torque value M1 in step S4.

[0050] FIG. 6 shows a graph illustrating the temporal course of the applied drive torque M.sub.drive and the rotation angle ϕ where an overload procedure is applied to a blocked control valve 2. The applied drive torque M.sub.drive is depicted by the solid curve whereas the rotation angle ϕ is depicted by the dashed curve. In region d, the valve member 21 is not blocked and the rotation angle ϕ responds to the applied drive torque M.sub.drive, i.e. the valve member 21 is moved by the rotation angle ϕ in accordance to the applied drive torque M.sub.drive. At the position denoted by f, a blocking of the control valve 2 or the valve member 21, respectively, occurs and the rotation angle ϕ does not respond anymore to the applied drive torque M.sub.drive, and starts to level out. The circuit 11 of the HVAC actuator 1 detects the blocking due to the applied drive torque effecting only a change of the rotation angle ϕ being smaller than the threshold angle ϕ.sub.th and starts the overload procedure by increasing the drive torque M.sub.drive to the first drive torque value M1 in region e. After reaching the first drive torque value M1, the applied drive torque M.sub.drive is repeatedly changed between the first drive torque value M1 and the second drive torque value M2 as denoted by g. It can be recognized that the applied drive torque M.sub.drive reaches the first drive torque value M1 and/or the second drive torque value M2 for each peak and/or dip within certain tolerances as mentioned earlier. Furthermore, the repeated change of the applied drive torque M.sub.drive is not strictly periodic, as the shape of the peaks and/or dips may vary to a certain extent. At the position h, the repeated change of the applied drive torque M.sub.drive is interrupted, due to the number of increases of the applied drive torque M.sub.drive to the first torque value M1 exceeding a defined number of increases and persisting of the blocking of the control valve 2. The applied drive torque M.sub.drive is returned to the second torque value M2, which may be the holding torque required to keep the valve member 21 at the current position. The first torque value M1 may be equal to the maximally applicable drive torque of the HVAC actuator 1. The second torque value M2 is smaller than the first torque value M1. A modulation of the first drive torque value M1 is performed each time the applied drive torque M.sub.drive is increased to the first drive torque value M1. Due to the comparatively small amplitude and the larger frequency of the modulation signal with respect to the repeated change of the applied drive torque M.sub.drive between the first torque value M1 and the second drive torque value M2, the modulation is not shown in FIG. 6. The frequency of the modulation signal may be at least 10 times larger than the frequency of the repeated change of the applied drive torque M.sub.drive. In some embodiments, the frequency of the modulation signal may be around 100 times larger than the frequency of the repeated change of the applied drive torque M.sub.drive.

[0051] FIG. 7 shows a graph illustrating the temporal course of the applied drive torque M.sub.drive in a range where the first drive torque value M1 is periodically modulated between a third torque value M3 and a fourth torque value M4. In the shown example, the first torque value M1 is equal to the third torque value M3. In other embodiments, the first torque value M1 may be between the third torque value M3 and the fourth torque value M4. In some embodiments, the first torque value M1 may be equal to the fourth torque value M4. The fourth torque value M4 is smaller than the third torque value M3 and larger than the second torque value M2. The first torque value M1 is modulated by a rectangular modulation signal. Although not shown in the Figures, it is clear to the person skilled in the art, that a triangular or a sawtooth signal or other modulation signals known in the art can be applied correspondingly to modulate the first torque value M1. The modulation shown in FIG. 7 is superimposed to the repeated change of the applied drive torque M.sub.drive, as shown in FIG. 6. Again, the applied drive torque M.sub.drive may deviate from the ideal rectangular signal as shown in FIG. 7 within tolerances known to the person skilled in the art. It can be recognized from FIG. 7, that the duty cycle of the rectangular modulation signal deviates from 0.5 in that the time where the applied drive torque M.sub.drive is set to the third torque value M3 or maximum oscillation torque, respectively, is smaller than the time where the applied drive torque M.sub.drive is set to the fourth torque value M4. The periodic modulation of the first torque value M1 as shown in FIG. 7 leads to a “hammering” effect, which is effective for releasing the blocking of the control valve 2. Furthermore, the “hammering” effect allows to reduce the time during which the applied drive torque M.sub.drive has to be kept at the first torque value M1 and/or the number of increases of the applied drive torque M.sub.drive to the first torque value M1, due to higher efficiency in releasing the blocking of the control valve 2. By reducing the time or number of increases of the applied drive torque M.sub.drive to the first torque value M1, the risk of harming the HVAC actuator 1 can be reduced or avoided.

[0052] FIG. 8 shows an illustration of the ranges near a fully closed position and a fully open position of the control valve 2 where periodic modulation of the first drive torque value is deactivated. In the course of closing the control valve 2, as shown by the arrows pointing from 90° to 0°, the overload procedure or periodic modulation of the first torque value, respectively, is performed in a range c1 as shown by the bold arrow, in the case of a blocking of the control valve 2. In a first range c2 from a closed position of the control valve 2, e.g. between 0° and 5°, the overload procedure or periodic modulation of the first torque value, respectively, is deactivated, in order to avoid “hammering” into sealing elements of the control valve 2. In the course of opening the control valve 2, as shown by the arrows pointing from 0° to 90°, the overload procedure or periodic modulation of the first torque value, respectively, is performed in a range of as shown by the bold arrow, in the case of a blocking of the control valve 2. In a second range o2 up to a fully open position of the control valve 2, e.g. between 85° and 90°, the overload procedure or periodic modulation of the first torque value, respectively, is also deactivated. In ranges c2, the circuit 11 may control the HVAC actuator 1 to apply a fifth torque value M5 equal to a closing torque. The fifth torque value M5 may be smaller than the first torque value M1 and larger than the second torque value M2. The full moving range of the valve member 21 is denoted by R. The scheme may equally be applied to a rotating valve member 21 as well as to a linearly moving valve member 21 with a suitable gear drive and/or another mechanical coupling to translate the drive torque to a rotating or linear movement.

LIST OF DESIGNATIONS

[0053] 1 HVAC actuator [0054] 11 Circuit [0055] 2 Control valve [0056] 21 Valve member [0057] M.sub.drive Applied drive torque [0058] M0 Drive torque applied at detection of the blocking [0059] M1 First torque value [0060] M2 Second torque value [0061] M3 Third torque value [0062] M4 Fourth torque value [0063] M5 Fifth torque value [0064] ϕ Rotation angle [0065] ϕ.sub.th Threshold angle [0066] Δϕ Change of the rotation angle [0067] N.sub.inc Number of increases to the first torque value M1 [0068] N.sub.def Defined number of increases to the first torque value M1 [0069] c2 First range [0070] c1 Range [0071] o2 Second range [0072] R Range