Patent Application
20190335540
The invention relates to a method for controlling a heating system component for heating fluid media in a heating system of a household appliance. Additionally, the invention relates to a heating system comprising a controller and at least one temperature sensor.
For many types of domestic appliances or domestic machines, it is necessary to heat up a fluid medium, such as for example water. Heating up can be caused by means of one or more heating systems. To that extent, a medium circuit can be provided, a pump arranged in the circuit causing circulation of the medium in the circuit.
Basic aspects of such heating systems are that, like all other components of the medium circuit, the system is to take up only a small amount of space and is to be inexpensive to produce. Furthermore, the heating system shall be simple to assemble. Reliable safeguarding of the heating system must be guaranteed upon the occurrence of a critical operating condition which can result in plastic components within the domestic appliance melting or catching fire. In case of some domestic appliances, it may further be necessary to prevent the medium to be heated from exceeding a predetermined temperature. For example, in the case of a dishwashing machine, it may be necessary to prevent the washing water from exceeding its boiling temperature.
US patent application 2006/0236999 discloses a heating system for heating fluid media, in particular for domestic appliances, including a carrier unit, a heating unit arranged on the carrier unit and a heat transfer element which is arranged on the carrier unit and comprises a material which is a good conductor of heat. On the heat transfer element, temperature safety devices are mounted by fixing elements via corresponding through apertures.
A system with two temperature sensors, which are used to switch-off the device when a failure occurs, is disclosed in DE patent application 10 2011 002 861. A similar system is also disclosed in DE patent application 10 2016 215 266.
DE patent application 10 2012 203 715 discloses a system with a pump which comprises safety control for switching-off the pump. This safety control also may switch-off the heating unit when a failure occurs.
Moreover, from EP patent application 3 238 599 a heating unit is known, which comprises an electronic temperature sensing device being arranged thermally conductive with the thermally conductive element to detect and record the temperature of the thermally conductive element over time in order to provide information about the operating condition of the washing machine. The device is used to avoid that a trigger temperature of a fuse is reached.
It is a general object of the manufacture of heating systems and heating system components to provide ever smaller and more compact construction parts, which provide a sufficient heating power (if not the same heating power as before). It is a further object to reduce manufacturing costs.
In addition, when using conventional temperature monitoring and/or control elements (such as, e.g., thermal fuses) with continuous-flow water heaters, there is a problem when the temperature monitoring and/or control elements are fixed with, e.g., one or more screws, to a mounting plate. That is, when the mounting plate is soldered to the heating unit, it may bend. Further, when fastening respective fixing screws on a temperature monitoring and/or control element, the temperature monitoring and/or control element may be lifted from the fixing plate and remain in the air above the hot location. As a consequence, the largest amount of heat in the center of the heating unit cannot be released directly to the temperature monitoring and/or control element, but has to be released via, e.g., the mounting plate, screws, and/or the base plate flange. These effects result in an unacceptable (i.e., too slow) response time of the temperature monitoring and/or control element. Accordingly, it would be advantageous to directly mount a temperature sensor at the position where a certain temperature should be monitored. NTC thermistors are temperature sensors well known in the art. However, the rather inexpensive NTC thermistors may not continuously be exposed to temperatures exceeding 85 to 125° C. Since a heating unit of a heating system component usually reaches temperatures above 100° C., inexpensive NTC thermistors are usually not suitable for being directly mounted to or near the heating unit within the heating system component, thus preventing more compact design.
An object of the present invention is therefore to provide a method for controlling and protecting a heating system component which avoids the shortcomings of prior-art heating systems.
According to a first aspect of the invention, there is provided a method for controlling a heating system component of a heating system for heating a fluid medium, said heating system component comprising: a carrier unit; a heating unit coupled to said carrier unit; and a controller; wherein said carrier unit comprises a wet side and a dry side, wherein the wet side corresponds to a surface of said carrier unit configured to be in contact with the fluid medium, wherein the dry side is located on a surface opposite to the wet side. The heating system component further comprises at least one temperature sensor, in particular a NTC thermistor, wherein the temperature sensor is effectively in thermal contact and electrically isolated with at least a part of an upper surface of the dry side of the carrier unit. The method comprises: receiving a starting signal at the controller for starting the heating system component; carrying out a test routine for at least the at least one temperature sensor; and in case the test routine is not successful: entering a safe state of the heating system component.
Due to this method, a safe startup procedure is possible.
If there is no water inside the pump-housing present at the wet side, due to an error in the heating system, excess heating of plastic components could occur. The prior art already uses temperature sensors to monitor the whole component during the entire operation process. The present invention describes the startup procedure and the continuous safety-protection during operation.
Therefore, it is contemplated to carry out at least a test routine for the at least one temperature sensor before the heating system component is started completely. In case the test routine is not successful, a safe state of the heating system component is entered. A safe state in this instance can include that the heating unit will not be supplied with power. For example, a single operating device can be operated, in particular a fuse can be blown or a safety switch (e.g. relay, electronic switch devices) can be switched off, such that no power is supplied to the heating unit of the heating system component. The heating system component or the appliance comprising the heating system component may still stay switched-on, however, preferably outputs a failure signal, e.g. by means of a display showing a failure code. For example, a display of the appliance having the heating system component and carrying out the method could display an appropriate failure code or an instruction for an operator on a display. It could also be contemplated to show instructions how to resolve the problem.
In case the test routine is successful, preferably the startup of the heating system component is completed accordingly.
The heating unit may be any suitable heating unit and may have any suitable form. In a particularly preferred embodiment, the heating unit is recessed in a groove provided on said dry side of the carrier unit. The heating unit in this case is preferably curved and may resemble a C-shape. Further suitable forms comprise pipe heaters, free flow heaters, flat-plate heaters, thick film and thin film technology, rod shaped heating elements and the like.
Preferably, the at least one temperature sensor, in particular a NTC thermistor, is effectively in thermal contact with at least a part of an upper surface of said dry side of the carrier unit, wherein the part of the upper surface of said dry side of the carrier unit is arranged in contact with said fluid medium at the wet side, and preferably wherein the part of the upper side of the carrier unit is effectively thermally coupled to and electrically isolated from the heating unit.
Being effectively in thermal contact with at least a part of an upper surface of said dry side of the carrier unit does require a direct contact of the temperature sensor with the upper surface of the dry side of the carrier unit. However, the effective thermal contact shall be understood as providing a thermal contact which allows a measurement of the fluid medium circulating at the wet side of the carrier unit. Thus, the thermal contact should ensure a major impact on the measured temperature coming from the fluid medium on the wet side of the carrier unit. The temperature sensor may also measure a mix temperature of the fluid and the heating unit. By providing the temperature sensor, in particular a NTC thermistor, effectively in thermal contact with at least a part of an upper surface of said dry side of the carrier unit, wherein said at least part of the upper side of the carrier unit is effectively thermally coupled to the heating unit, it can be ensured that the temperature sensor is not exposed to temperatures exceeding the maximum temperature of the fluid circulated on the wet side of the carrier unit, which in most common household appliances is 85 to 125° C. Up to this temperature, it is possible to use common cost-effective NTC thermistors which further allow a compact design of the heating system component with reduced material budget.
Preferably, the test routine includes: sending a test signal from the controller to said at least one temperature sensor, preferably by using the heating element. The test signal may simply trigger a response of the temperature sensor to test whether this is still active. When a temperature sensor would not be active, a temperature control of the heating system component would not be possible during operation and an excess heating of the heating system component could easily occur. To avoid such a state, it is preferably tested whether the temperature sensor (or temperature sensors) operates in normal state and therefore the test signal by using the heating element is sent to the at least one temperature sensor.
The above step may be carried out without powering the heating unit, or during operation while the heating unit is being powered. In the second case it may be preferred to switch-off the heating unit for a short time and send the test signal while the heating unit is switched-off.
Moreover, it is preferred that the test routine includes: powering the heating unit with a predetermined test power level for a predetermined test time period; obtaining a temperature test value measured by the at least one temperature sensor; and comparing the obtained temperature test value with a predetermined temperature threshold. Preferably, these steps are carried out during operation, e.g. while the hot water is produced. Preferably, the temperature test value is obtained after the predetermined test time period has lapsed. Preferably, the temperature test value is furthermore obtained after an additional delay time (heater off time), after the predetermined test time (heater on time) period has ended. That is, the test time period may be a first time duration, and the temperature test value is obtained after a second time duration, which is longer than the first time duration. This is beneficial, since the heating system component has a certain temperature rise time (equivalent dead time), which depends on system properties, as e.g. size, material, and thermal conductivity of elements.
In the step of comparing the obtained temperature test value with a predetermined temperature threshold, it can be determined whether the heat up process results in a temperature, which is too high for the short predetermined test time period. Thus, when the obtained temperature test value is above the threshold, a dry run failure could be the reason. Therefore, in this case, the test routine is considered not being successful and the safe state is entered. In the opposite case, when it is determined that the obtained temperature test value is below the predetermined threshold, the test routine is considered being successful and the startup of the heating system component can be completed. A normal operating state can be entered.
In a preferred embodiment, the test power level is 100% or less of a maximum power level, preferably 50% or less, particularly preferred 25% or less. When the test power level is set to be relatively high, e.g. 100% of the maximum power level, a quick test result can be achieved. The heating unit is driven by the maximum power level, which is the maximum power level the system is able to supply to the heating unit, and therefore a fast heating process is achieved.
However, setting the test power level to such a high value bears the risk that excess heating of single elements or other adjacent components is caused. Therefore, it is also preferred to set the test power level to 50% or less of the maximum power level. A value of 50%, 25% or less is easily obtainable when the heating unit is powered by an alternating current. Moreover, a value of 25% or less lowers the risk of overshooting.
In a further preferred embodiment, the test power is supplied in a pulsed manner. Pulsing the supplied test power is an effective method for reducing the power level and thus increasing safety of the heating system component. Pulsing the test power in the present case could include phase angle control, leading edge and trailing edge phase control, pulse package control, and/or pulse width modulation.
Depending on whether direct current or alternating current is used, different pulsing methods are preferred.
According to a further preferred embodiment, the test routine includes powering the heating unit with a predetermined test power level at a test start time; obtaining a temperature test value measured by the at least one temperature sensor; determining that a predetermined test temperature threshold is reached at a test end time; and comparing a duration from the test start time to the test end time with a predetermined time period threshold. These steps could be carried out as an alternative or an addition to the above referenced steps of the test routine, which include powering the heating unit with a predetermined test power level for a predetermined test time period. In this present alternative, the test time period is variable and the heating unit is at least powered until the test temperature threshold is reached. Thus, in this embodiment, the duration until the temperature threshold is reached is measured. When this duration is relatively long, it is an indicator that water is present at the wet side of the carrier unit. When this time period, on the other hand, is rather short, it is an indicator for no or just some water at the carrier unit and thus an indicator for a risk of running dry. Therefore, when it is determined that the duration from the test start time to the test end time is below a predetermined time period threshold, the test routine is considered to be not successful and a safe state of the heating system component is entered. One benefit of this embodiment is that the temperature sensor can be designed in a simple manner. It is not important that the temperature sensor is able to measure a broad variety of different values; rather, it is sufficient when a temperature sensor is adapted to measure only one value i.e. the test temperature threshold. Moreover, it is possible in both above cases to calculate a gradient, in this case a temperature over time gradient (ΔT/Δt) based on which specific actions could be taken.
Preferably, powering is stopped in this embodiment after a predetermined maximum time. Additionally or alternatively, the powering is stopped at the test end time or within short thereafter. Within short thereafter, in the present case could include: within a predetermined time frame after the test end time. This predetermined time frame may be a set absolute duration or a relative duration dependent on the duration from the test start time to the test end time, a measured temperature, or the supply power. Restricting the power in this embodiment to a predetermined maximum time increases safety of the heating system component and prohibits overheating just by the test routine. Moreover, it could be contemplated to stop the powering short thereafter, e.g. within 1 second or 10 seconds after the predetermined test temperature threshold has been reached. This can avoid false signal detection and a verification measurement can be carried out in addition. It may be provided that the test temperature threshold needs to be exceeded for a certain time period to trigger the respective signal. This may avoid false signal detection.
In a further preferred embodiment, the test routine includes: powering the heating unit with a predetermined heat quantity. In this alternative, the heat quantity is kept constant.
Therefore, the method preferably also comprises: in this embodiment, determining a supply voltage of the heating unit; and calculating by the controller a start up supply time necessary to obtain the supply of the predetermined heat quantity. The supply time ts can be calculated from the following equation:
ts=W≙R/U
2; (eq. 1)
Thus, by knowing the resistance R and by measuring the supplied voltage U, the time ts, which is necessary to reach the predetermined heat quantity (work) W can be determined. This embodiment has the benefit that the supplied heat quantity for carrying out the test routine is always the same. The risk of overheating is reduced.
In a further preferred embodiment, multiple temperature test values are obtained, and the method further comprising the step: calculating a heating curve based on the multiple temperature test values. For calculating the heating curve, it is not necessary that a continuous or quasi-continuous temperature measurement is carried out, rather it is sufficient to obtain a plurality of temperature test values at discrete times. In one embodiment, it is sufficient to only obtain two temperature test values to calculate the heating curve.
Based on such a heating curve, a slope of the heating curve can be determined and the determined slope can be compared with at least a first predetermined slope threshold. In this regard it shall be noted that a relatively high difference quotient of ΔT/Δt is indicative for a fast heating and thus may be indicative for a lack of water at the wet side.
For some embodiments and applications, it is preferred that the heating system component comprises a second temperature sensor distal from said first temperature sensor. For example, the first temperature sensor may be mounted in the so called hot area, close to the heating unit, and the second temperature sensor may be mounted in the cold area, distal to the heating unit. One of the first and second temperature sensors may also be mounted between the hot and the cold area, in the so called mixed area.
It shall be noted that even though NTCs are preferred as temperature sensors, also other known devices could be used, as e.g. SMD-NTCs, thin film thermistors, thermocouples or resistive temperature sensors.
When two temperature sensors are used, for some applications it may be beneficial that the method further comprises: obtaining a second temperature test value measured by said second temperature sensor; and comparing the obtained second temperature test value with a second predetermined temperature threshold. Preferably, also the further steps described above are carried out using the second temperature sensor.
Furthermore, it is possible, that a controller is connected with the at least one temperature sensor via a primary connection and a redundant second temperature sensor by using a redundant connection. Some regulations require a redundant system by using two measuring paths. It is possible to design the system to be redundant. Safety is further increased.
In a second aspect of the invention, the object stated in the introductory portion is also solved by a heating system component for a heating system for heating a fluid medium, wherein the heating system component comprises a carrier unit; a heating unit coupled to said carrier unit; and a controller; wherein said carrier unit comprises a wet side and a dry side, wherein the wet side corresponds to a surface of the carrier unit configured to be in contact with the fluid medium, wherein the dry side is located on a surface opposite to the wet side; and wherein the heating unit is recessed in a groove provided on said dry side of the carrier unit, and further comprising at least one temperature sensor, in particular an NTC thermistor, wherein said temperature sensor is effectively in thermal contact with at least a part of an upper surface of said dry side of the carrier unit, wherein the controller comprises a memory and a processor, the memory comprises a software code, which, when run on the processor, causes the controller to carry out the method according to any of claims 1 to 12.
A controller is not necessarily directly adjacent to the carrier unit; the controller rather can also be a controller of the heating system or a higher system, e.g. a system of the appliance, which uses the heating system. It could also be provided that the controller is accessible via a network or the internet, in order to read specific temperature sensor values, which are stored in the memory. Moreover, the controller could be accessible via internet to update the software stored on the memory or initiate other actions. Before this action, the temperature sensor data of other various heater units in e.g. dishwashers can be collected also via internet.
Moreover, it shall be understood that the controller comprising the memory, processor and the software code is also claimed herein separately and independently. Furthermore, also the software code, which when carried out on a processor carries out the method of the first aspect of the invention is claimed independently and separately.
In an embodiment, said heating system further comprises a heat conducting plate covering at least a part of the groove, wherein the heat conducting plate comprises a detached portion at a circumferential part detached from the heating unit recessed in the groove, the detached portion has a projecting part extending beyond the groove of the carrier unit, the projecting part is in direct contact with the dry side of the carrier unit; and the temperature sensor is mounted at the projecting part, and wherein the detached portion of the heat conducting plate preferably comprises trenches in radial direction of respective peripheral edges of the projecting part. Preferably, the heating system component may further comprise a second temperature sensor, in particular a NTC thermistor, wherein said second temperature sensor is in thermal contact with an upper surface of the heat conducting plate covering the heating unit inside the groove or direct located on the heating-surface.
In a further embodiment, the temperature sensor is provided inside the groove of the carrier unit shielded from the heating unit by a shielding unit. Preferably, the shielding unit is made of coated steel, stainless steel or an aluminum material. In a further preferable implementation, a second temperature sensor is provided inside the groove shielded from the heating unit by a shielding unit, wherein the resulting temperature is first measured by the first and second raw temperature values and then derived by a mathematic formula (e.g. min, max, average, . . . ) out of them. In a further preferable implementation, the first and second temperature sensors are NTC thermistor pills cast in epoxy resin between the dry side of the carrier unit and the shielding unit. The compact, yet cost-efficient design provided by this embodiment allows a reliable measurement of the fluid temperature on the wet side of the carrier unit while providing an easy assemble of the heating system component within a respective household appliance. Since the temperature measurement components are provided inside the groove, the risk of damages during assembly is significantly reduced.
In an embodiment, the heating system component further comprises a heat conducting plate covering at least a part of the groove, wherein the heat conducting plate comprises a projecting part extending beyond the groove of the carrier unit, the projecting part being in direct contact with the dry side of the carrier unit; and wherein the temperature sensor is provided at a ceramic pad fixed at a projecting part of the carrier unit. Preferably, a second temperature sensor is positioned on a second ceramic pad, wherein the second ceramic pad is fixed at a position of the heat conduction plate covering the groove. In a further preferable implementation, one or more conductor paths are provided along the heat conduction plate to connect the one or more temperature sensors, wherein the conductor paths are insulated from the heat conduction plate by an insulating layer, preferable comprising a polyimide, such as—but not limited to—Kapton, a polyamide or a polyester.
In a further embodiment, the heating system component further comprises a heat conducting plate covering at least a part of the groove, wherein the heat conducting plate comprises a projecting part extending beyond the groove of the carrier unit, the projecting part being in direct contact with the dry side of the carrier unit; wherein at least a part of the heat conducting plate is covered with an insulating layer on top of which the temperature sensor and conductor paths connected to the temperature sensor are formed. Preferably, the heating system component comprises a plug with pins to be connected to the conductor paths wherein the plug also provides electric connections for the heating unit. Preferably, the temperature sensor, the conductor paths and the insulating layer are formed at the heat conducting plate by printing or thermal spraying. Alternatively, the insulating layer may also be attached directly to a portion of the dry side of the carrier unit. Preferably, the temperature sensor and the conductor paths are formed at the insulating layer before being attached to the carrier unit. The insulating layer may be jointed to a respective plug and afterwards be glued to the carrier unit, wherein the plug may be connected (e.g. welded, soldered, or the like) to the heating unit connection pins and/or the carrier unit.
In a further embodiment, the carrier unit comprises an undercut portion which is covered with a thermoplastic layer doped with a metal-plastic additive directly sprayed at the undercut portion and subsequently metalized at respective portions of an upper surface of the thermoplastic layer; wherein the temperature sensor and conductor paths connected to the temperature sensor are formed at the metalized thermoplastic layer by laser cutting. Preferably, the heating system component comprises a transparent plug comprising the electrical contacts to be connected with the conductor paths leading to the temperature sensor, wherein the transparent plug is coupled with the thermoplastic layer using laser welding.
In an embodiment, the heating system component further comprises a heat conducting plate covering at least a part of the groove, wherein the heat conducting plate comprises a projecting part extending beyond the groove of the carrier unit, the projecting part being in direct contact with the dry side of the carrier unit; wherein at least a part of the heat conducting plate is covered with a thermoplastic layer doped with a metal-plastic additive directly sprayed at least at a part of the projecting part and subsequently metalized at respective portions of an upper surface of the thermoplastic layer; wherein the temperature sensor and conductor paths connected to the temperature sensor are formed at the metalized thermoplastic layer by laser cutting. Preferably, the heating system component comprises a transparent plug comprising the electrical contacts to be connected with the conductor paths leading to the temperature sensor, wherein the transparent plug is coupled with the thermoplastic layer using laser welding.
It shall be understood that a preferred embodiment of the invention can also be any combination of the dependent claims or above embodiments with the respective independent claim.
It has to be noted that the present invention can also be used in conjunction with quartzite heaters, flow through heaters, flat plate heaters, thick film and thin film heaters.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
In the following drawings:
Heating system component 100 may be connected to, e.g., a conveyor pump of a domestic appliance such as—but not limited to—a dishwashing machine. Heating system component 100 can be attached to the conveyor pump or to a conveyor pump housing during assembly of the domestic appliance. In another example, heating system component 100 can form a pre-assembled structural unit together with the conveyor pump.
As can be seen from
Heating unit 120 is arranged on dry side 102 of carrier unit 110 as shown in
Carrier unit 110 may comprise a composite material. The composite material comprises at least an aluminum layer and a stainless steel layer. The stainless steel layer is arranged on wet side 101 of carrier unit 110. The aluminum layer is arranged on dry side 102 of carrier unit 110. In an example, the composite material may be produced by means of a cold roll bonding process.
In the embodiment illustrated in
In the embodiment illustrated in
Another possibility for addressing problems associated with an occurrence of voids between carrier unit 110 and heating unit 120 is to arrange a phase change compound between carrier unit 110 and heating unit 120. Such a compound changes its phase state above its phase change temperature and is thereby able to fill cracks, voids, slits, etc. In an embodiment, the phase change compound is applied to the surfaces of carrier unit 110 and/or heating unit 120 by means of a dispensing step. Dispensing typically implies that the phase change compound dries within a short period of time.
In the embodiment illustrated in
Optionally, a second NTC thermistor may be provided, either at a further detached portion 142 in order to determine the fluid temperature, such that the first and second NTC thermistor measurements can be averaged in order to increase the liability. Alternatively, second NTC thermistor 170b may be mounted at non-detached portion 144 of heat conducting plate 140 in order to determine the temperature of heating unit 120 itself to prevent, for instance, that the pump is running dry. In the latter case, an NTC thermistor sustaining the resulting temperatures reachable by heating unit 120 must be chosen.
When heating unit 120 is powered, it might happen that there is no water present at wet side 101, which could result in a quick overheating of the heating system component. According to the present invention, the at least one temperature sensor 170a, 180a, 270a, 370a, 460, 470a, 480, 770 is used to determine whether the heating system component is overheating or if a safe operation is possible. In this regard,
When starting signal S1 is received in receiving step 2, subsequently a test routine 3 as a second section is carried out. It shall be noted that in general there are three different options for carrying out test routine 3. One first option is carrying out test routine 3 on demand without any further heating step. A second option is carrying out test routine 3 after starting the appliance. A third option is carrying out test routine 3 during the regular operation of the appliance. It shall be understood that all three options are contemplated within the scope of the present invention, even though in the embodiment described in the following only the second option is described in detail.
According to this embodiment (
When test power level Wt is 50% or less of the maximum power level, the risk of overheating just in test routine 3 is lowered. Other preferred values are 20% or less, 25% or less, 40% or less. Preferably, test power level Wt is not lower than 10%, since then test routine 3 will not provide exact results.
After heating unit 120 has been powered with test power level Wt for the predetermined test time period Th (see
Moreover, in a comparing step 10, obtained temperature test value S4 is compared with a predetermined temperature threshold Tt (see
In
Based on this comparison, a decision 12 is made after test routine 3 has been carried out. When the determined temperature value is below predetermined temperature threshold Tt (as e.g. value Tf), it is determined that test routine 3 is successful and the normal starting procedure can be continued in step 14. Normal operation of heating unit 120 is carried out.
When in decision step 12, it is found that the measured temperature value is above predetermined temperature threshold Tt (as e.g. the value Te), it is considered that test routine 3 is not successful and subsequently a safe state 16 is entered.
Such a safe state could be e.g. cutting the power supply to heating unit 120, while the appliance still is switched-on. A test result signal S5 may be provided by controller 30 to the operator, or to a higher level control unit of the appliance.
In a first example, the two temperature sensors NTC1, NTC2 can be used to detect dry run failure. For this application, two temperature sensors NTC1, NTC2 are necessary to achieve a redundancy. In this example, the method preferably comprises determining a first slope Y1 of first heating curve 44 for first temperature sensor NTC1. First slope Y1 is defined by ΔT/Δt measured beginning at determination time Td. Then, this determined first slope Y1 is compared with a first slope threshold YT1, which might be in the range of 12 to 40 K/s, dependent on the physical inertia of heating unit 120. Preferably, the method also comprises determining a second slope Y2 of second heating curve 46 for second temperature sensor NTC2. Second slope Y2 is defined by ΔT/Δt measured beginning at determination time Td. Then, this determined second slope Y2 is compared with a second slope threshold YT2, which might be in the range of 1 to 10 K/s, dependent on the physical inertia of heating unit 120, as the second mounting position 842 is in the mixed area and therefore it is assumed that temperature rises slower there.
Furthermore, the method may comprise determining a difference TNTC1−TNTC2 with a predetermined threshold, wherein TNTC1 is the temperature measured at the determination time Td using the first temperature sensor NTC1 and TNTC2 is the temperature measured at the determination time Td using second temperature sensor NTC2. The threshold in this case may in the range of 80 to 120° C. Of course, also a comparison with a fixed predetermined threshold of only one temperature test value may be provided. For example, it may be determined whether the temperature test value of first temperature sensor NTC1 is above a predetermined threshold in the range of 180 to 220° C.
In case one or more of the above four tests are positive, i.e. the respective value is above the respective threshold, test routine 3 is not successful.
In a second example in which two temperature sensors are necessary, a so called boiled to dry procedure is carried out. During a boiled to dry procedure, heating unit is started while a maximum water level is present at wet side. Heating unit is then powered until all water is boiled and wet side is dry. Such a process may e.g. beneficially be carried out with an electric kettle.
In this process, similar steps as defined in the above first example are carried out, but the following threshold values are used:
In this process, similar steps as defined in the above first example are carried out. This process is carried out to test whether there is lime on surfaces of heating system component 100. The following threshold values are used:
In this process, the method preferably comprises the step of determining a difference TNTC1−TNTC2 with a predetermined threshold, wherein TNTC1 is the temperature measured at determination time Td using first temperature sensor NTC1 and TNTC2 is the temperature measured at determination time Td using second temperature sensor NTC2.
However, the determined difference preferably is compared with a first lime threshold YL1 and a second lime threshold YL2. First lime threshold YL1 may be in the range of <50 to 60° C. Second lime threshold YL2 may be in the range of 80 to 120° C. When the determined difference is between the two lime thresholds YL1, YL2, it may indicate that lime is present on surfaces (wet side 101) of heater unit 120. A respective notice may be give to the operator.
When the second threshold is exceeded, this may indicate that there is a relatively high amount of lime at heater unit 120, and test routine 3 is considered not successful. Safe state 16 may be entered in this event.
One of the two temperature sensors NTC1, NTC2 may be formed as a safety-related sensor, while the other one is formed as a non-safety-relevant sensor.
In this fourth example, a running dry failure may be detected based on either first or second temperature sensor NTC1, NTC2. The method in this embodiment preferably comprises determining a first slope Y1 of first heating curve 44 for first temperature sensor NTC1. First slope Y1 is defined by ΔT/Δt measured beginning at determination time Td. Then, this determined first slope Y1 is compared with a first slope threshold YT1, which might be in the range of 15 to 40 K/s, dependent on the physical inertia of heating unit 120.
In a second step, an absolute temperature test value at determination time Td is measured and compared to a respective threshold. In this case, the threshold may be in the range of 180 to 220° C.
Alternatively, second temperature sensor NTC2 is used. The respective thresholds of the difference and the absolute temperature test value are: 1 to 10 K/s, and 80 to 120°, in this case.
When both, the threshold for the difference and the threshold of the absolute temperature test value are exceeded, test routine 3 is considered not to be successful and the safe state 16 is entered.
This procedure is carried out identically to the fourth example.
In this example, only the absolute temperature test value measured at determination time Td is used. The threshold for first temperature sensor NTC1 may be set to 120 to 150° C. and the threshold for a second temperature sensor NTC2 may be set to 60 to 80°.
In an alternative, the procedure of the sixth example is carried out using a further temperature sensor, which is already present in the appliance in which the heating system component is used. By means of this further sensor, the temperature of the water can be determined accurately and by this additional value, the amount of lime may be determined properly.
Moreover, it is preferred that the method in this embodiment comprises the steps: storing the measured temperature test value in a memory of the controller; and comparing the measured value with at least one previously stored value, preferably with a plurality of previously stored values.
The previously stored values may be used to calculate a curve and the slope of this curve may also be used to carry out an analysis of lime at the heater unit. Dependent on the slope a specific notice may be provided to the operator.
The seventh example is based on the fourth example and again used to determine lime.
In this embodiment, a second temperature test value after an additional waiting time after determination time Td is obtained. The additional waiting time preferably is chosen such that the temperature measured by first and/or second temperature sensor NTC1, NTC2 substantially equals the temperature of the water present at the wet side.
Then, this second value may be used as described in the third example.
Now
In the embodiment schematically illustrated in
These connecting pins 123 are not located inside groove 112, but project towards an axial direction to be connected to a power source. Temperature sensor 180 is therefore preferably provided in the portion of groove 112 which is not covered by heating unit 120 and is located below connection pins 123. In order to shield the temperature sensor 180 from heating unit 120, a shielding unit 181 is provided inside and preferably form-fit to the walls of groove 112. Shielding unit 181 is made of a heat insulating material such as—but not limited to—stainless steel. As shown in cross-sectional view of
The embodiment schematically illustrated in
The two main connectors 408 for heating unit 120 are basically formed at a heating unit connector frame 812, which is shown in
Moreover, male contact 806 for temperature sensor 480 is attached to a basically Z-shaped lash element 824, which comprises a holding arm 826. At the free distal end of holding arm 826, temperature sensor 480 is arranged. At a little portion, there is provided a foil, in particular a Kapton-foil, which is electrically insulating and heat conductive, as particularly described in the European patent application 17188041.2.
On the left-hand side of
When clip housing 812 is mounted over frame 812 and lash element 824, holding down clip 822 will contact temperature sensor 480 and hold and push it towards heating unit 120, as basically shown in
To improve the contact properties, a contact paste 850 (e.g. silver paste) with good thermal properties can optionally be used.
Also, an elastic element 860 can optionally be used to compensate the mounting tolerances (e.g. heat resistant rubber or similar).
In
An example application of the invention generally relates to situations where a fluid medium needs to be heated in an efficient manner, for example in household appliances such as dishwashers, dryers, and washing machines, small electrical appliances such as coffeemakers, irons, steam generators etc. or in water heaters. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.
In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.
A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
Determinations like measuring a temperature performed by one or several units or devices can be performed by any other number of units or devices. For example, measuring a temperature can be performed by a single temperature sensor or by any other number of different units. The determinations and/or the control of the heating system for heating fluid media can be implemented as program code means of a computer program and/or as dedicated hardware.
A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. The term “software code” may also refer to embedded software.
Any reference signs in the claims should not be construed as limiting the scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18169327.6 | Apr 2018 | EP | regional |
