Valve arrangement and method for actuating a valve

Abstract

Valve arrangement (1) comprising: a thermostatic valve head (3), a valve (2) for controlling a flow of heating or cooling fluid through a heat exchanger, an actuator (12) for actuating the valve (2), a control device (15) for controlling the actuator (12), a first temperature sensor (18) connected to the control device (15), and a second temperature sensor (19) connected to the control device (15), wherein a thermal resistance between the first temperature sensor (18) and the valve (2) is greater than a thermal resistance between the second temperature sensor (19) and the valve (2), wherein the first temperature sensor (18) and the second temperature sensor (19) are part of a sensing device that detects a closed state of the valve (2).

Description

[0001] The invention relates to a valve arrangement comprising a valve for controlling a flow of heating or cooling fluid through a heat exchanger, a drive for actuating the valve, a control device for controlling the drive, a first temperature sensor connected to the control device, and a second temperature sensor connected to the control device, wherein a thermal resistance between the first temperature sensor and the valve is greater than a thermal resistance between the second temperature sensor and the valve.

[0002] Furthermore, the invention relates to a method for actuating a valve, wherein the valve controls a flow of heating or cooling fluid through a heat exchanger and is activated by a drive, wherein a first temperature is detected at a predetermined first position relative to the valve and a second temperature is detected at a predetermined position relative to the valve, wherein a thermal resistance between the second position and the valve is smaller than a thermal resistance between the first position and the valve.

[0003] A valve assembly of the type mentioned above and a method for operating a valve as mentioned above are known from GB 2 452 043 A. The first temperature sensor detects the ambient temperature of a room. The second temperature sensor detects a temperature in the vicinity of the valve. The temperature detected by the second temperature sensor is used to calculate a compensation value for the first temperature sensor, so that the ambient temperature can be determined with greater accuracy.

[0004] EP 1 235 130 A2 describes a method and device for controlling a room temperature using two temperature sensors, one of which senses the room temperature and the other a temperature near the valve. Both temperatures are combined to obtain more reliable information about the actual room temperature.

[0005] DE 10 2009 040 397 A1 describes a diagnostic system for a valve in which a positioner operates a valve via an actuator. The positioner has a housing that is attached to the valve.

[0006] A first temperature sensor and a second temperature sensor are mounted on or in the housing. Due to the position of the two sensors, the temperature measured by the first temperature sensor is more influenced by the ambient temperature, while the temperature detected by the second temperature sensor 20 is more influenced by the ambient temperature. If a gas leak occurs in the valve, a temperature difference occurs, which is evaluated to diagnose a leak. The position of the closing body or a valve stem connected to the closing body is detected by the position controller via a connecting piece.

[0007] A thermostatically controlled valve compares the actual room temperature with a preset room temperature and increases the flow of heating fluid when the actual room temperature is below the preset room temperature, and decreases the flow of heating fluid when the actual room temperature is higher than the preset room temperature. In most cases, this results in a slightly oscillating movement of a valve element relative to a valve seat. Such movement requires energy. If the actuator is electrically powered, energy waste should be avoided.

[0008] Furthermore, for a sophisticated control of the valve, information about the degree of opening of the valve is necessary, e.g. the position of the valve element relative to the valve seat.

[0009] If an electrically driven actuator is used, this information can be obtained by driving the valve in the closing direction until the force required to move the valve element increases dramatically. This increase is an indication that the valve element has contacted the valve seat and sealant is being compressed. However, this detection also requires a large amount of electrical energy, as power consumption does not increase linearly with the applied force.

[0010] The object underlying the invention is to improve the control of the valve.

[0011] This object is achieved by a valve arrangement having the features of claim 1.

[0012] This can be explained using a simple example: By comparing the two temperatures, it is possible to detect whether the valve is open or closed. When the valve is open, the two temperature sensors detect different temperatures. The first temperature sensor detects ambient or room temperature. The second temperature sensor detects a higher temperature because the second temperature sensor is thermally closer to the valve. The valve itself has a temperature close to that of the heating fluid. The same applies when using a cooling fluid. In this case, the second temperature sensor detects a temperature lower than the ambient or room temperature. If there is a temperature difference between the two temperature sensors, this is an indication that the valve is open.If there is no temperature difference or the temperature difference is smaller than a predetermined difference, it can be assumed that the valve is closed. In this case, no fresh heat is supplied to the valve by the heating or cooling fluid. Accordingly, after a certain time, the valve is almost at room or ambient temperature. However, the use of two or more temperatures can enable the controller to also detect the degree of valve opening or the position of a valve element relative to a valve seat. In this case, additional parameters can be useful, e.g., the time required to reach a predetermined temperature difference. A simple way to implement different thermal resistances is to arrange the temperature sensors at different distances relative to the valve.

[0013] In a preferred embodiment, the drive is an electric stepper motor, wherein in a detection phase the valve is opened step by step, starting from a starting point in which the valve is closed, wherein the control device detects and stores the number of a step at which the valve begins to open. The point at which the valve begins to open can be detected by an increase in temperature detected by the second temperature sensor, because the temperature detected by the first temperature sensor does not increase in the same way. To start the detection phase, the valve is moved to a state in which it can be assumed that the valve is closed. The valve is then opened step by step. At a certain step, heating or cooling fluid can flow through the valve.In this case, heat is supplied to the valve, resulting in a temperature increase of the valve, which can be detected by the second temperature sensor.

[0014] Preferably, the actuator is operated by a group of steps, and the control device comprises a timer device that defines a pause between successive groups of steps. If, for example, the actuator has to make 1000 steps to move the valve from a fully closed state to a fully open state, it would be quite time-consuming to check the temperature behavior of the valve after each step. In this case, it is advantageous for the actuator to be operated with a number of steps without waiting, e.g. 25 or any other number of steps. After such a group of steps, the opening operation is interrupted for a predetermined time. If the valve has started to open, the heat supplied by the heating or cooling fluid has increased the temperature of the valve. If the valve has not started to open, the temperature of the valve remains unchanged.The time required between successive groups of steps depends on the overall installation, particularly the length of a line between a heat source or main supply line and the valve. If such a line is short, the pause can be brief.

[0015] In a preferred embodiment, the control device has a heat source status input and only performs the detection phase if the heat source status input indicates that the heat source is active. If the heat source is not producing heat, i.e., is not supplying heating or cooling fluid at an elevated or lower temperature, the temperature of the valve will not change, regardless of whether the valve is closed or not. Indicating the operating status of the heat source saves energy because unnecessary valve operation can be avoided.

[0016] In a further preferred embodiment, the control device has an output indicating a closed state of the valve. This closed state can be reported to the heat source. If the heat source detects that all valves in a heating system are closed, it is no longer necessary to produce heat or supply a heating or cooling fluid. This saves heating energy.

[0017] Furthermore, in a monitoring phase, the control device can move the valve to a closed state and, with the help of the first temperature sensor and the second temperature sensor, monitor whether the valve is closed. The closed state can be the one that was previously detected. Such a monitoring phase can be performed once a day or once during another predetermined period. When the valve is moved to a previously detected closed state, after a certain time, the temperature detected by the second temperature sensor should be the same as the temperature detected by the first temperature sensor. If this is not the case, this is a reliable indication that the valve is not fully closed. The actuator can use another group of steps to move the valve in the closing direction.If after a time the closing state can be detected because both temperature sensors indicate the same temperature, the new step number is stored as information about the closing point.

[0018] Preferably, the second temperature sensor is arranged on a support element, the support element extending parallel to an actuating axis of the actuator and projecting beyond the actuator in a direction toward the valve. The second temperature sensor is arranged in a part of the support element that is closer to the valve. The use of a support element, which can be a printed circuit board (PCB), is a simple way to place the second temperature sensor close to the valve.

[0019] Preferably, the first temperature sensor and the second temperature sensor are offset from each other in the circumferential direction with respect to the actuation axis. In this case, both temperature sensors can be placed at optimal positions.

[0020] Furthermore, it is preferred that the support element is part of the thermostatic valve head, wherein the thermostatic valve head comprises fastening means for fastening the thermostatic valve head to the valve, wherein the second temperature sensor is arranged adjacent to the fastening means. When the thermostatic valve head is attached to the valve, the fastening means must engage with the valve. Arranging the second temperature sensor adjacent to the fastening means is a simple way to ensure that the second temperature sensor is indeed arranged close to the valve.

[0021] The object is further achieved by a method having the features of claim 10.

[0022] As explained above, the valve is considered closed when the two temperatures are equal to or within a small temperature range determined by a predetermined value. In other words, a closed state of the valve is detected when the first temperature and the second temperature differ from each other by a temperature difference smaller than a predetermined value. If the temperature difference between the two temperatures is greater than the predetermined value, it is considered that a heating or cooling fluid is supplying heat (positive or negative) to the valve, raising or lowering the valve temperature. In this case, the valve temperature will be different from the ambient or room temperature. This is a clear indication that the valve is not closed.

[0023] Preferably, in a detection phase, the valve is opened step by step, starting from a starting point where the valve is closed, and the number of the step at which the valve opens is stored as opening information. If the drive is in the form of a stepper motor, each step defines a specific degree of opening of the valve, provided that the valve has started to open. If the number of the step at which the valve opens is known, precise control of the position of the valve element relative to the valve seat is achieved. This makes it possible to take non-linear behavior of a valve into account. This non-linear behavior means that an opening movement of the valve element over a predetermined distance has a greater influence on the flow of heating or cooling fluid through the valve near the closing point than in a situation where the valve element is a greater distance from the valve seat.It is assumed that the opening and closing points are the same.

[0024] Preferably, the opening of the valve is interrupted for a predetermined period of time after a group of steps, and the first temperature and the second temperature are compared at the end of the period of time.

[0025] When the valve is closed, there is no flow of heating or cooling fluid through the valve. In this case, the first temperature and the second temperature will be the same. This situation changes when the valve begins to open. In this case, heat supplied by the heating or cooling fluid increases or decreases the temperature of the valve, which in turn leads to an increase or decrease in the second temperature. Valve opening is detected by comparing the first and second temperatures.

[0026] The detection phase should preferably only be performed when a heat source supplying the heating or cooling fluid is active. This operating state of the heat source can be indicated by a signal transmitted from the heat source to the valve controller. If the heat source is not active, there will be no temperature change, regardless of whether the valve is open or not.

[0027] Preferably, in a monitoring phase, the valve is moved to a closed state (e.g., previously detected), and it is monitored whether the valve is closed by comparing the first temperature and the second temperature. When the valve has been moved to a closed state, there should be no difference between the two temperatures. If there is still a difference, it is assumed that the valve has not fully closed, and the valve is moved further in the closing direction. The number of steps necessary to move the valve to the fully closed state is stored, and the previously stored number is decremented accordingly.

[0028] A preferred embodiment of the invention will now be described in further detail with reference to the drawing, in which the The only figure shows a schematic representation of the valve arrangement.

[0029] The single figure shows a valve arrangement 1 which has a schematically illustrated valve 2 and a thermostatic valve head 3.

[0030] The valve has an inlet 4 and an outlet 5, separated by a bore 6 in which a valve seat 7 is arranged. A valve element 8 cooperates with the valve seat. When the valve element 8 rests against the valve seat 7, the valve 2 is closed. When the valve element 8 (as shown) is a certain distance from the valve seat 7, the valve 2 is open, allowing a flow of heating or cooling fluid from the inlet 4 to the outlet 5.

[0031] The valve 2 has a non-linear characteristic. When the valve element 8 is moved in the opening direction by a predetermined stroke, e.g., 1 mm, this movement also has a greater influence on the fluid flow when the valve element 8 is close to the valve seat 7 than when the valve element 8 is at a greater distance from the valve seat 7. In other words, using the same stroke, the increase in flow becomes greater when the movement of the valve element 8 begins closer to the valve seat 7.

[0032] To control the fluid flow through the valve 2, information about the current position of the valve element 8 relative to the valve seat 7 is valuable. The method for obtaining this information will be described later.

[0033] The valve element 8 is connected to a valve spindle 9, which in turn interacts with a tappet 10 penetrating a housing 11. Sealing means are provided but not shown. Furthermore, the valve element 8 can be biased by a spring (not shown) in the opening direction, i.e., in a direction away from the valve seat 7.

[0034] The thermostatic valve head 3, shown separately from the housing 11, has a drive 12 in the form of a stepper motor connected to a drive spindle 13 via a gear 14. The drive spindle 13 is moved in one direction toward the housing 11 when the valve 2 should be closed and in the opposite direction when the valve 2 should be opened. The energy required to operate the drive 12 can be supplied by a battery. Therefore, energy consumption should be as low as possible. Oscillating movement of the valve element 8 should be avoided.

[0035] The drive 12 is controlled by a control device 15, which is shown only schematically. The control device 15 may have more elements than the box shown.

[0036] A support element 16 in the form of a printed circuit board (PCB) is arranged parallel to an actuating axis 17 and extends in a direction toward the valve housing 11. In this direction, the support element 16 is longer than the actuator 12.

[0037] A first temperature sensor 18 is arranged on a front side of the thermostatic valve head 3 and detects a first temperature, which is considered to be ambient or room temperature. A second temperature sensor 19 is arranged at an end of the support element 16 adjacent to the housing 11. When the thermostatic valve head 3 is mounted on the housing 11 of the valve 2, the second temperature sensor 19 is arranged in close proximity to the housing 11 and is therefore capable of detecting the temperature of the housing 11 or a temperature closely adjacent thereto.

[0038] The thermostatic valve head 3 has fastening means 20 that are used to attach the thermostatic valve head 3 to the housing 11. The housing 11 has a corresponding fastening geometry 21. The second temperature sensor 19 is arranged adjacent to the fastening means 20.

[0039] Furthermore, it can be seen that the first temperature sensor 18 and the second temperature sensor 19 are offset relative to each other in the circumferential direction when the circumferential direction is related to the actuating axis 17.

[0040] In a prior art valve, the position of the valve element 8 relative to the valve seat 7 was detected in the following way: The valve element was moved in a direction toward the valve seat 7. When the valve element 8 touched the valve seat 7, the force required to move the valve element 8 further toward the valve seat 7 increased. The valve element 8, which was usually formed from an elastomeric material, was compressed. The increase in force is usually associated with an increase in power consumption, which could be detected by the control device 15. However, such a procedure is energy-intensive and does not allow for an accurate determination of the closing point (or opening point) of the valve 2.

[0041] The valve arrangement 1 shown provides another possibility to determine the closing point with a relatively high accuracy.

[0042] The valve 2 is driven into a closed state. This state can be easily verified by comparing a first temperature detected by the first temperature sensor 18 and a second temperature detected by the second temperature sensor 19. If there is a temperature difference between these two temperatures that exceeds a predetermined value, this is a clear indication that there is still a flow of heating or cooling fluid from a heat source (not shown) through the valve. This heating or cooling fluid supplies heat to the housing 11 of the valve 2 (or removes heat from the housing 11), so that the temperature difference is maintained.

[0043] When the valve is closed, there is no flow of heating or cooling fluid through the valve 2 and therefore no supply of heat to the housing 11. After a short time, the temperature detected by the second temperature sensor 19 will be the same as the temperature detected by the first temperature sensor 18 (or within a certain range around this temperature).

[0044] This is a sign that valve 2 is properly closed.

[0045] Another way to ensure that valve 2 is closed is to move the actuator 12 (stepper motor) a predetermined number of steps in the closing direction. This number should be set high enough to ensure that valve 2 is reliably closed.

[0046] For example, drive 12 has a stroke of 1000 steps. Each position of drive spindle 13 is assigned a step number. Therefore, if the actual step number is known, the position of drive spindle 13 is also known.

[0047] To detect an opening point of the valve 2, the actuator 12 moves the drive spindle 13, for example, 25 steps in the opening direction. After that, a timer device of the control device 15 controls a pause of a predetermined length. If at the end of this pause the temperatures detected by the two temperature sensors 18, 19 are the same, this is an indication that the valve is still closed. In this case, the operation is repeated, e.g. the actuator 12 is moved again to move the drive spindle 13 in the opening direction by a further 25 steps. Again, the temperatures detected by the two temperature sensors 18, 19 are compared. Opening of the valve 2 is detected when the temperature detected by the second temperature sensor 19 is higher (or lower) than the temperature detected by the first temperature sensor 18.Since the controller 15 has counted the number of steps up to this point, the controller 15 has clear information about the number of the step at which valve 2 begins to open. In the described example, there is a maximum error of 25 steps, which is acceptable.

[0048] The thermostatic valve head 3 receives a signal from a heat source (not shown) indicating whether the heat source is active or not. If the heat source is inactive and not supplying heating or cooling fluid, there will be no difference between the temperatures detected by the two temperature sensors 18, 19, regardless of whether the valve 2 is closed or not.

[0049] Furthermore, it is preferred that the thermostatic valve head 3 signals the heat source whether the valve 2 is closed or not. If the heat source knows that all valves connected to this heat source are closed, it is not necessary for it to be active. It is also possible for the thermostatic valve head 3 to signal the heat source that the supply temperature needs to be increased or decreased to meet a heat demand. All communication can be done via signal lines or wirelessly via a transmitter-receiver arrangement.

[0050] It is possible that the settings of the valve (or the combination of valve 2 and thermostatic valve head 3) may change over time.

[0051] Furthermore, it is possible to record the "true" closing point of valve 2, e.g., once a day. In this case, valve 2 is moved in the closing direction, e.g., each time through a group of 25 steps. After each group, the temperatures of the first temperature sensor 18 and the second temperature sensor 19 are compared (preferably a predetermined time period after the movement). If both temperatures are the same, this is an indication that valve 2 is closed. If the step number at which valve 2 closed differs from the previously determined step number, the new step number is stored as the closing or opening point.

[0052] Detection of the closing point can also be performed during normal operation. In most cases, the control device 15 will detect the need to close the valve 2 at least once a day, e.g., when the ambient and room temperature detected by the first temperature sensor 18 is higher than a previously set temperature. This closing operation can also be used to monitor the closing point.

[0053] During the monitoring or detection phase, the pause between consecutive actuations of valve 2 should be on the order of a few minutes, e.g., 5 minutes. The optimal length of this pause depends on the heating or cooling system in which valve assembly 1 is installed. If the line between valve 2 and the heat source is short, the heating or cooling fluid reaches valve 2 more quickly than in a system with a longer line. Therefore, the length of the pause is preferably adjustable.

Claims

[1] Valve arrangement (1) comprising: a thermostatic valve head (3), a valve (2) for controlling a flow of heating or cooling fluid through a heat exchanger, a drive (12) for actuating the valve (2), a control device (15) for controlling the drive (12), a first temperature sensor (18) connected to the control device (15), and a second temperature sensor (19) connected to the control device (15), wherein a thermal resistance between the first temperature sensor (18) and the valve (2) is greater than a thermal resistance between the second temperature sensor (19) and the valve (2), wherein the first temperature sensor (18) and the second temperature sensor (19) are part of a detection device which detects a closed state of the valve (2). [2] Valve arrangement according to claim 1, characterized byin that the drive (12) is an electric stepper motor, wherein in a detection phase the valve (2) is opened step by step, starting from a starting point in which the valve (2) is closed, wherein the control device (15) detects and stores the number of a step at which the valve begins to open. [3] Valve arrangement according to claim 2, characterized by that the drive (12) is actuated by a group of steps, and the control device (15) has a timer device which defines a pause between successive groups of steps. [4] Valve arrangement according to claim 2 or 3, characterized by that the control device (15) has a heat source status input and performs the detection phase only when the heat source status input indicates that the heat source is active. [5] Valve arrangement according to one of claims 1 to 4, characterized bythat the control device (15) has an output which indicates a closed state of the valve (2). [6] Valve arrangement according to one of claims 1 to 5, characterized by that in a monitoring phase the control device (15) moves the valve (2) into a closed state and monitors with the aid of the first temperature sensor (18) and the second temperature sensor (19) whether the valve (2) is closed. [7] Valve arrangement according to one of claims 1 to 6, characterized by that the second temperature sensor (19) is arranged on a support element (16), wherein the support element extends parallel to an actuating axis (17) of the drive (12) and projects beyond the drive (12) in a direction towards the valve (2). [8] Valve arrangement according to claim 7, characterized by that the first temperature sensor (18) and the second temperature sensor (19) are offset from one another in the circumferential direction with respect to the actuating axis (17). [9] Valve arrangement according to claim 7 or 8, characterized by in that the carrier element (16) is part of a thermostatic valve head (3), wherein the thermostatic valve head has fastening means (20) for fastening the thermostatic valve head (3) to the valve (2), wherein the second temperature sensor (19) is arranged adjacent to the fastening means (20). [10] Method for actuating a valve (2) of a valve arrangement (1), wherein the valve arrangement (1) has a thermostatic valve head (3), wherein the valve (2) controls a flow of heating or cooling fluid through a heat exchanger and is activated by a drive (12), wherein a first temperature is detected at a predetermined first position relative to the valve (2) and a second temperature is detected at a predetermined second position relative to the valve (2), wherein a thermal resistance between the second position and the valve (2) is smaller than a thermal resistance between the first position and the valve (2), wherein the first temperature and the second temperature are compared with each other and the closed state of the valve (2) is detected. [11] Method according to claim 10, characterized bythat in a detection phase the valve (2) is opened step by step, starting from a starting point in which the valve (2) is closed, and the number of the step at which the valve (2) opens is stored as opening information. [12] Method according to claim 11, characterized by that after a group of steps the opening of the valve (2) is interrupted for a predetermined time period and the first temperature and the second temperature are compared at the end of the time period. [13] Method according to claim 11 or 12, characterized by that the acquisition phase is only carried out when a heat source supplying the heating or cooling fluid is active. [14] Method according to one of claims 10 to 13, characterized bythat in a monitoring phase the valve (2) is driven in a closed state and it is monitored whether the valve (2) is closed by comparing the first temperature and the second temperature

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