Calibration method for a device having a fan, operating method for a device having a fan, and device having a fan

Abstract

The invention relates to a calibration method for a device (2) with a fan (8), wherein the calibration method comprises the following steps in the specified order: switching on the fan (8) and starting up the fan (8) to a predetermined rotational speed of a fan wheel of the fan (8); switching off the fan (8) at a time t equal to 0 ms; sensorless determination of the density of a gas mixture at a known or assumed relative humidity of the gas mixture as a function of an air pressure at a location where the device (2) is installed during a first time interval, starting at t equal to 0 ms; after the end of the first time interval, determination of the duration of a second time interval as a function of a predetermined reduction in the rotational speed of the fan wheel of the fan (8);Determination of a wear value for the fan (8) as a function of the duration of the second time interval and the sensorless determined density of the gas mixture during the first time interval; adjustment of a relationship stored in the control unit (6) of the device (2) between the electrical power consumption of the fan (8) and the density of the gas mixture as a function of the aforementioned wear value. Furthermore, the invention relates to an operating method for a device (2) and a device (2).

Description

[0001] The invention relates to a calibration method for a device with a fan, an operating method for a device with a fan and a device with a fan according to the preamble of patent claim 11.

[0002] Such devices with a fan and methods for their operation are already known from the prior art. For example, EP 1 342 414 A1 discloses a method for detecting the humidity in a device for treating and preparing food, as well as a device for treating and preparing food. In this method, current temperature values ​​and speed values ​​of the asynchronous motor driving a gas conveying and circulating device are compared with at least one characteristic curve stored in a computer, and the current humidity in the gas mixture is determined from the deviation of the measured speed from the speed of the stored characteristic curve. The disadvantage of this is that the accuracy of the method of EP 1 342 414 A1 depends on the quality of the characteristic curve stored in the computer and on the quality of the detected speed values ​​of the asynchronous motor.If one of these values, and especially if both of these values ​​themselves are inaccurate, this leads to a correspondingly inaccurate conclusion about the humidity in the closed cooking chamber during the cooking process.

[0003] The invention therefore addresses the problem of improving a device with a fan and a method for the device with a fan.

[0004] According to the invention, this problem is solved by a calibration method for a device having the features of patent claim 1, according to which the calibration method comprises the following method steps in the specified order: switching on the fan and running the fan up to a predetermined speed of a fan impeller of the fan; switching off the fan at a time t equal to 0 ms; sensorless determination of the density of the gas mixture at a previously known or assumed relative humidity of the gas mixture as a function of an air pressure at a location where the device is installed during a first time interval, starting with t equal to 0 ms; after the end of the first time interval, determination of a duration of a second time interval as a function of a predetermined reduction in the speed of the fan impeller of the fan;Determining a wear value to indicate the degree of wear of a bearing of the fan impeller as a function of the duration of the second time interval and the sensorless density of the gas mixture during the first time interval; adjusting a relationship stored in the device's control system between an electrical power consumption of the fan and the density of the gas mixture as a function of the aforementioned wear value. Furthermore, this problem is solved by an operating method having the features of patent claim 6 and a device having the features of patent claim 11. Advantageous embodiments and further developments of the invention emerge from the following subclaims. For example, the previously known or assumed relative humidity of the gas mixture can be 0% relative humidity of the gas mixture.

[0005] The advantage achievable with the invention lies in the particular improvement of a device with a fan and a method for the device with a fan. Due to the inventive design of the calibration method, the operating method, and the device, it is possible to determine the humidity of the gas mixture, for example an air-water mixture, in the treatment chamber, for example a cooking chamber of a device designed as a cooking appliance, more accurately, reliably, simply, and cost-effectively than before. This is because, for example, no explicit humidity sensor is required to determine the humidity of the gas mixture. At the very least, an alternative to known methods and devices is to be provided.

[0006] Thus, the power consumption of the fan's electric motor, i.e., the electrical power consumption of the fan, can be used to determine the humidity of the gas mixture in the treatment room without an explicit humidity sensor. This gas mixture can be, for example, ambient air or a gas mixture of ambient air and water vapor, or steam for short. This is based on the knowledge that the power consumption of the electric motor is proportional to the density of the gas mixture in the treatment room. From the density of this gas mixture, at a known temperature of this gas mixture, the humidity of this gas mixture and thus the humidity in the treatment room of the device can be determined.

[0007] The power consumption of the fan's electric motor depends not only on the humidity but also on the air pressure at the device's installation location and on friction in the fan's impeller bearings, i.e., the degree of wear on the fan. Accordingly, the accuracy and reliability of determining the humidity of the gas mixture can be increased by prior calibration of the relationship between the fan's electrical power consumption and the density of the gas mixture stored in the device's control system.After the fan is switched off, i.e., after the power supply is disconnected, it continues to run. This fan run-on depends on the aforementioned bearing friction and the air pressure prevailing at the device's installation location. Bearing friction increases due to increasing wear, while air pressure depends on the device's installation altitude and the weather conditions at the installation location. These influences on the relationship between the fan's electrical power consumption and the density of the gas mixture can be easily and cost-effectively accounted for using the method according to the invention.

[0008] The invention takes advantage of the following relationship: The speed of a fan motor that is sluggish due to bearing friction drops overall more quickly than, for example, with a relatively new motor. Furthermore, the fan motor is braked more rapidly at high air pressure, i.e., with a high density of the gas mixture, than at lower air pressure and thus a low density of the gas mixture. In order to differentiate between the two influences on the speed, namely the influence of bearing friction on the one hand and the influence of air pressure on the other, the effect is used that, with the fan, the speed influences the power consumption and thus also the braking power with the cube. P 1 P 2 = n 1 n 2 3

[0009] Where P stands for the electrical power consumption or the braking power of the fan and n stands for the speed of the fan.

[0010] Bearing friction, on the other hand, has an almost linear relationship. At a relatively high speed, the braking torque from the fan, influenced by the air density, has a much greater effect on the speed reduction than at low speeds. Therefore, the gradient in the first time interval can be used as a parameter for the density. At lower speeds, bearing friction has a greater effect on the run-down behavior, i.e. the fan's overrun. Thus, by measuring the second time interval, a value can be determined which is significantly influenced by bearing friction. By including the gradient determined in this way from the first time interval, which is a parameter for the density, a wear value for the aforementioned bearing friction can be determined. This can be used to minimize the influence of the fan, namely its friction, on the humidity determination using the fan speed.

[0011] In principle, the calibration method according to the invention and the operating method according to the invention can be freely selected within wide suitable limits.

[0012] An advantageous development of the calibration method according to the invention provides that the aforementioned sensorless determination of the density of the gas mixture includes an evaluation of a differential quotient of a speed-time curve during the first time interval. In this way, the influence of the air pressure on the fan speed during the aforementioned fan run-on after it has been switched off, i.e., after it has been de-energized, is taken into account in a very simple manner.

[0013] A further advantageous development of the calibration method according to the invention provides that the first time interval begins with t equal to 0 ms and ends with t less than or equal to 500 ms, preferably with t equal to 500 ms. This provides a particularly advantageous value range for the first time interval, since this value range is highly relevant in practice. This applies in particular to the preferred embodiment of this development.

[0014] Another advantageous development of the calibration method according to the invention provides that the second time interval to be determined corresponds to a reduction in the speed of the fan impeller from a speed of less than or equal to 1000 revolutions per minute and greater than 400 revolutions per minute, preferably from 1000 revolutions per minute, to a speed of less than or equal to 400 revolutions per minute, preferably from 400 revolutions per minute. In this way, a particularly advantageous value range is specified for the reduction in speed during the second time interval, since this value range is also highly relevant in practice. This applies in particular to the preferred specified values.

[0015] A further advantageous development of the calibration method according to the invention provides that the calibration method is designed as a calibration method carried out separately from an operating method for the device for performing a main function of the device. This achieves a clear separation between the calibration method according to the invention, on the one hand, and the regular operation of the device when the operating method according to the invention is carried out, so that the respective method can be designed specifically for the respective functionality.

[0016] As an alternative to the aforementioned development of the calibration method according to the invention, an advantageous development of the operating method according to the invention provides that the calibration method is designed as a calibration method integrated into an operating method for the device for performing a main function of the device. In this way, it is possible to perform the calibration according to the invention during regular operation of the device according to the invention, so that the device according to the invention does not have to be transferred to a calibration mode separate from the operating method to perform the calibration method according to the invention.

[0017] In an advantageous development of the aforementioned embodiment of the operating method according to the invention, it is provided that the calibration process takes place in a phase of the operating method in which the density of the gas mixture is essentially constant; preferably, the calibration process takes place in a preheating phase of the operating method for preheating the uncharged treatment chamber. This effectively prevents an undesirable influence of fluctuations in the density of the gas mixture. This applies in particular to the preferred embodiment of this development.

[0018] In principle, the relationship between the fan's electrical power consumption and the density of the gas mixture can be used within wide, suitable limits for the operation of the device according to the invention. The device is expediently operated depending on the humidity of the gas mixture determined using the aforementioned relationship between the fan's electrical power consumption and the density of the gas mixture.

[0019] Another advantageous development of the operating method according to the invention provides that, depending on the wear value, an automatic warning is issued to a user of the device. In this way, the invention enables additional functionality. Thus, the user of the device can be informed, for example, of an imminent fan failure, essentially without additional effort. Accordingly, the user can take timely measures for maintenance, repair, or replacement of the fan or fan components. The user can be informed in a variety of ways known to those skilled in the art.

[0020] The device according to the invention can be freely selected within wide, suitable limits in terms of type, mode of operation, material and dimensions.

[0021] An advantageous development of the device according to the invention provides that the device has a user interface connected to the controller for signal transmission and / or a device interface connected to the controller for signal transmission. This makes it possible, among other things, to manually enter the installation altitude of the device using the aforementioned user interface, so that a very precise sensorless determination of the density of the gas mixture is possible at a previously known or assumed relative humidity of the gas mixture, for example at a relative humidity of the gas mixture of 0%, depending on the installation altitude of the device at the respective installation location of the device. The aforementioned device interface makes it possible to use an installation altitude already known and stored in another device installed at the installation location for the inventive calibration method in the device according to the invention.Furthermore, a further advantageous development of the device according to the invention provides that the device is designed as a cooking appliance, preferably as an oven, a steam cooker, a microwave cooking appliance, or a combination device with radiant heating and a steam generator. In this way, devices are specified in which the invention can be used particularly meaningfully and beneficially. This is because the humidity in a treatment chamber designed as a cooking chamber is of particular importance for a cooking process taking place in the cooking chamber. However, other designs of the device according to the invention are also conceivable. Purely by way of example, reference is made here to dishwashers and tumble dryers. The device according to the invention, for example the device according to the invention designed as a cooking appliance, can be designed as a household appliance or as a commercial appliance, i.e., a device for professional use.

[0022] An embodiment of the invention is shown purely schematically in the drawings and is described in more detail below. It shows Figure 1 shows an embodiment of the device according to the invention for carrying out the calibration method according to the invention and for carrying out the operating method according to the invention, and Figure 2 shows a speed-time diagram with time on the abscissa and the speed of the fan on the ordinate.

[0023] In the Fig. 1 and 2 An embodiment of the invention is shown purely by way of example.

[0024] The appliance 2, designed as a household steam cooker, has a treatment chamber 4 designed as a cooking chamber for a product to be treated, namely a product not shown. The appliance 2 further comprises a controller 6, a fan 8, which is connected to the controller 6 for signal transmission, for flushing the treatment chamber 4 with a gas mixture (not shown), namely an air-water mixture, and a temperature sensor 10, which is connected to the controller 6 for signal transmission, for measuring the temperature of the gas mixture. The fan 8 here has an electric drive motor (not shown) designed as a BLDC motor, which is connected to the controller 6 for signal transmission and power transmission. The term "BLDC motor" stands for a brushless DC motor. Furthermore, the appliance 2 comprises a user interface 12, which is connected to the controller 6 for signal transmission, and a device interface 14, which is connected to the controller 6 for signal transmission.See the . Fig. 1 .

[0025] The functioning of the device according to the invention, the calibration method according to the invention and the operating method according to the invention according to the present embodiment are described below with reference to Fig. 1 and 2 explained in more detail.

[0026] Device 2 was delivered to the end customer and installed at a location not shown for device 2 for operation of device 2.

[0027] When commissioning the device 2 at the installation location of the device 2, the calibration method according to the invention is first carried out as follows: In a first step, the fan 8 is switched on and run up to a predetermined speed of a fan impeller (not shown) of the fan 8. For example, the fan is run up to a speed of 1800 revolutions per minute. Once the aforementioned speed is reached, the fan 8 is switched off, i.e., de-energized, so that the BLDC motor (not shown) of the fan 8 no longer drives the fan impeller of the fan 8. This switch-off time corresponds to the time t equal to 0 ms.

[0028] In a first time interval, namely in a time interval from t equal to 0 ms up to and including t equal to 500 ms, the sensorless determination of the density of the gas mixture takes place at a previously known or assumed relative humidity of the gas mixture as a function of the air pressure at the installation location of the device 2. Since the device 2 has not yet been operated and therefore no cooking process has taken place in the treatment chamber 4 designed as a cooking chamber, it can be assumed that the gas mixture in the device 2 has a relative humidity of 0%. This aforementioned sensorless determination of the density of the gas mixture comprises, in the present embodiment, an evaluation of a differential quotient of the Fig. 2 speed-time curve shown. As can be seen from the Fig. 2 As can be seen and has already been explained above, the speed of the fan 8 flows with the third power into the electrical power consumption of the fan 8 and thus also into the braking power. P 1 P 2 = n 1 n 2 3

[0029] Here, P stands for the electrical power consumption of the fan 8, namely the BLDC motor (not shown), or for the braking power of the fan 8, and n for the speed of the fan 8, namely the fan wheel. Therefore, the gradient in the speed-time curve of the Fig. 2 in the first time interval can be used as a characteristic value for the density. At a relatively high speed, the braking torque from fan 8, influenced by the air density, has a significantly greater effect on the speed reduction than at low speeds.

[0030] After the end of the first time interval, the duration of a second time interval is determined depending on a previously determined reduction in the speed of the fan wheel of the fan 8, wherein the second time interval to be determined in the present embodiment corresponds to a reduction in the speed of the fan wheel of the fan 8 from a speed of 1000 revolutions per minute to a speed of 400 revolutions per minute. See the Fig. 2 At lower speeds, bearing friction has a greater impact on the stopping behavior, i.e., the run-on time of fan 8. However, unlike the density of the gas mixture, bearing friction has an almost linear relationship with braking power. Thus, by measuring the second time interval, a value can be determined that is significantly influenced by bearing friction.

[0031] By including the gradient determined in this way from the first time interval, which is a parameter for the density, a wear value for the aforementioned bearing friction can be determined. This can be used to minimize the influence of fan 8, namely its friction, on the humidity determination explained below using the speed of fan 8.

[0032] For this purpose, according to the present calibration method, the wear value for indicating a degree of wear of the bearing of the fan wheel of the fan 8 is determined as a function of the duration of the second time interval and the sensorless determined density of the gas mixture during the first time interval, and a relationship stored in the controller 6 of the device 2 between an electrical power consumption of the fan 8 and the density of the gas mixture is adjusted as a function of the aforementioned wear value.

[0033] The wear of the fan 8, namely the wear of the bearing of the fan impeller of the fan 8, can be measured in a specially provided calibration process, which is suggested at regular intervals to a user of the device 2 (not shown), for example, via the user interface 12 of the device 2 in a manner known per se to those skilled in the art. In this case, the calibration process is designed as a calibration process carried out separately from an operating process for the device 2 for performing a main function of the device 2.

[0034] Alternatively or additionally, the aforementioned wear can also be checked during a cooking process. For this purpose, a run-down process can be performed during regular operation of the device 2 after the fan 8 has been started for the first time. However, it is important that no changes in gas density occur during this time; therefore, a preheating process, during which no food should be present in the cooking chamber, would be suitable. In this case, the calibration process is designed as a calibration process integrated into an operating process for the device 2 to perform a main function of the device 2.

[0035] In the present embodiment, the device 2 is operated to carry out a cooking process depending on the humidity of the gas mixture determined by means of the aforementioned relationship between the electrical power consumption of the fan 8 and the density of the gas mixture.

[0036] To determine the humidity of the gas mixture in the device 2 designed as a steam cooker, the electrical power consumption of the fan 8 is used, with the speed of the fan 8 being kept constant. The aforementioned power consumption is proportional to the density of the gas mixture, namely air and water vapor, in the cooking chamber 4. From the density of the gas mixture, the humidity in the cooking chamber 4 can be determined at a known temperature. Since the density also depends on the air pressure and the friction losses of the fan 8, the calibration procedure explained above is carried out beforehand. The aforementioned temperature can be determined using the temperature sensor 10 and used in the controller 6.

[0037] In addition, the device 2 was initially calibrated at the end of the production line, i.e., specific characteristic values ​​of the device 2 were stored in the control unit 6 of the device 2, so that in the delivery state, the aforementioned bearing friction and other specific data of the device 2 according to the delivery state are known for the moisture determination.

[0038] As explained above, the aging of fan 8 is determined by measuring the speed at the outlet of fan 8. This also takes into account the air pressure depending on the installation altitude of device 2 and the weather conditions at the installation location of device 2, since air pressure influences the density of the gas mixture and thus the outlet behavior of fan 8.

[0039] In the diagram according to the Fig. 2 Several run-out curves for the fan 8 at two different densities are shown purely as examples for the fan 8 with a stiff bearing and for the fan 8 with a new, i.e. smooth, bearing, whereby in the image plane the Fig. 2 the uppermost run-out curve corresponds to the smooth-running bearing at low density of the gas mixture, the second highest run-out curve to the stiff-running bearing also at low density of the gas mixture, the second lowest run-out curve to the conductive bearing at high density of the gas mixture and the lowest run-out curve to the stiff-running bearing also at high density.

[0040] Furthermore, it can be provided that, depending on the aforementioned wear value, an automatic warning is issued to a user (not shown) of the device 2. For example, the user interface 12 can be used for this purpose in a manner known per se to those skilled in the art, for example, to issue an acoustic and / or visual warning. Based on this warning, the user can then take appropriate measures to arrange for the necessary maintenance, repair, or replacement of the fan 8 or components of the fan 8.

[0041] However, the invention is not limited to the present embodiment. See, for example, the relevant statements in the introduction to the description as well as the corresponding information on optional features in the explanation of the specific embodiment.

Claims

1. Calibration method for a device (2) with a fan (8) for flushing a treatment chamber (4) of the device (2) with a gas mixture, according to which the calibration method comprises the following method steps in the specified order: - switching on the fan (8) and running the fan (8) up to a predetermined speed of a fan impeller of the fan (8); - switching off the fan (8) at a time t equal to 0 ms; - sensorless determination of the density of the gas mixture at a previously known or assumed relative humidity of the gas mixture as a function of an air pressure at an installation location of the device (2) during a first time interval, starting with t equal to 0 ms; - after the end of the first time interval, determination of a duration of a second time interval as a function of a predetermined reduction in the speed of the fan impeller of the fan (8);- Determining a wear value to indicate the degree of wear of a bearing of the fan impeller of the fan (8) as a function of the duration of the second time interval and the sensorless density of the gas mixture during the first time interval; - Adjusting a relationship stored in the controller (6) of the device (2) between an electrical power consumption of the fan (8) and the density of the gas mixture as a function of the aforementioned wear value.

2. Calibration method according to claim 1, characterized in that the aforementioned sensorless determination of the density of the gas mixture comprises an evaluation of a differential quotient of a speed-time curve during the first time interval.

3. Calibration method according to claim 1 or 2, characterized in that the first time interval begins with t equal to 0 ms and ends with t less than or equal to 500 ms, preferably with t equal to 500 ms.

4. Calibration method according to one of claims 1 to 3, characterized in that the second time interval to be determined corresponds to a reduction in the speed of the fan wheel of the fan (8) from a speed of less than or equal to 1000 revolutions per minute and greater than 400 revolutions per minute, preferably of 1000 revolutions per minute, to a speed of less than or equal to 400 revolutions per minute, preferably of 400 revolutions per minute.

5. Calibration method according to one of claims 1 to 4, characterized in that the calibration method is designed as a calibration method carried out separately from an operating method for the device (2) for carrying out a main function of the device (2).

6. Operating method for a device (2) with a fan (8) for flushing a treatment chamber (4) of the device (2) with a gas mixture, according to which the device (2) is operated as a function of the relationship between the electrical power consumption of the fan (8) and the density of the gas mixture, which relationship is adjusted by means of the calibration method according to one of claims 1 to 5.

7. Operating method according to claim 6, characterized in that the device (2) is operated as a function of the humidity of the gas mixture determined by means of the aforementioned relationship between the electrical power consumption of the fan (8) and the density of the gas mixture.

8. Operating method according to claim 6 or 7, characterized in that the calibration method is designed as a calibration method integrated into an operating method for the device (2) for carrying out a main function of the device (2).

9. Operating method according to claim 8, characterized in thatthe calibration process takes place in a phase of the operating process in which the density of the gas mixture is substantially constant, preferably that the calibration process takes place in a preheating phase of the operating process for preheating the uncharged treatment chamber (4).

10. Operating method according to one of claims 6 to 9, characterized in that Depending on the wear value, an automatic warning is issued to a user of the device (2).

11. Device (2) with a treatment chamber (4) for a material to be treated, a control system (6), a fan (8) connected to the control system (6) for transmitting signals for flushing the treatment chamber (4) with a gas mixture and a temperature sensor (10) connected to the control system (6) for measuring a temperature of the gas mixture, characterized in that the device (2) is designed and configured to carry out the method according to one of claims 1 to 10.

12. Device (2) according to claim 11, characterized in that the device (2) has a user interface (12) connected to the controller (6) in a signal-transmitting manner and / or a device interface (14) connected to the controller (6) in a signal-transmitting manner.

13. Device (2) according to claim 11 or 12, characterized in that the device (2) is designed as a cooking device, preferably as an oven, a steamer, a microwave cooking device or a combination device with a radiant heater and a steam generator.

Images