Refridgerating device with a temperature sensor

Abstract

A refrigerating device is equipped with a temperature sensor in the form of an infrared sensor (7), for detecting an operating temperature of the device. Said infrared sensor (7) is located on a board (5) in a non-refrigerated are of the refrigerating device, together with a control circuit.

Description

[0001] The invention relates to a refrigerating device with a temperature sensor for detecting an operating temperature of the refrigerating device.

[0002] In refrigerating devices such as refrigerators, freezers or combination appliances an operating temperature such as an interior temperature or the temperature of an evaporator are conventionally detected using temperature-dependent resistances which are connected via a cable harness to a control circuit to regulate the refrigeration.

[0003] This technology which has been in normal use for a long time has various disadvantages. Firstly, it is necessary to attach the temperature-sensitive resistance directly at the location whose temperature is to be detected. However, the control circuit which regulates the operation of a refrigerating machine using the temperature detected by the temperature sensor is usually located in a non refrigerated outer area of the refrigerating device in order to avoid malfunctions caused by condensate formation on the control circuit. The spatial separation of the control circuit and the temperature sensor forced thereby makes these complicated and therefore expensive to attach.

[0004] Wiring is required to feed the measurement signal of the temperature-sensitive resistance to the control circuit. This wiring is sensitive to disturbances caused by electromagnetic stray effects. In addition, the detected temperature is not necessarily the temperature of the location to be monitored but the temperature established in the temperature-sensitive resistance. In order to avoid falsifications of the temperature measurement, it is thus necessary to insulate this efficiently from the non-refrigerated outer area.

[0005] Especially when such a conventional temperature sensor is used to monitor the temperature of an evaporator, the strong temperature fluctuations to which such a sensor is exposed and which can extend from −40° C. under normal refrigeration as far as +8° C. during defrosting, lead to considerable mechanical stresses on the insulation of the temperature sensitive resistance which can result in failures.

[0006] The object of the present invention is to provide a refrigerating device with a temperature sensor wherein the installation of the temperature sensor is simplified, wherein the sensitivity of the measurement signal of the temperature sensor to electromagnetic stray effects is reduced and wherein any failure as a result of thermal stresses is eliminated.

[0007] This object is achieved by a refrigerating device according to claim 1.

[0008] The operating temperature to be detected by the infrared sensor of this refrigerating device can be an interior temperature of the refrigerating device. In this case, a black body with which the infrared sensor is in visual contact can be provided in the interior of the refrigerating device.

[0009] The temperature of an evaporator of the refrigerating device can also be considered as the operating temperature to be measured. In this case, the infrared sensor is advantageously in visual contact with a surface of the evaporator facing the interior of the refrigerating device. This allows the temperature of this surface of the evaporator relevant for the cooling of the interior to be measured directly instead of the temperature of the back side which is easier to achieve in measurements using a temperature-sensitive resistance but may be falsified by a heat inflow from outside. Since the infrared sensor need not be located in direct contact with the object whose temperature it is to measure, it is possible to locate said sensor in the immediate neighbourhood of the control circuit, especially on a common board with the control circuit; thus the control circuit and the temperature sensor can be prefabricated as a structural unit and built into the refrigerating device according to the invention jointly during installation.

[0010] Since the temperature of the infrared sensor is not decisive for the measurement result, said sensor can be attached in a non-refrigerated outer area of the refrigerating device. In such a case it is desirable that it is separated from the measurement surface to be monitored by an infrared-transparent window which blocks an unhindered inflow of heat into the interior of the refrigerating device.

[0011] If the distance between the infrared sensor and the measurement surface to be monitored by it is large, it is desirable to provide a lens between the two to image the measurement surface on a radiation-sensitive surface of the sensor. This lens can especially form the afore-mentioned window at the same time.

[0012] Further features and advantages of the invention are deduced from the following description of embodiments with reference to the appended drawings wherein:

[0013] FIG. 1 is a schematic section through a part of the housing of a refrigerating device according to the invention according to a first embodiment of the invention; and

[0014] FIG. 2 is a similar section according to a second embodiment of the invention.

[0015] FIG. 1 shows a highly schematic section through the upper front corner of the housing of a refrigerating device according to the invention. The refrigerating device comprises a thermally insulating housing of which a part of an upper side 1 and a front side 2 with a door 3 mounted thereon can be seen in FIG. 1.

[0016] Mounted above the door 3 on the front side 2 is a screen 4 which can be a simple plastic moulding without any substantial thermal insulation effect of its own.

[0017] In the space enclosed by the screen 4 and the front side 2 there is a control circuit on a board 5 and an infrared sensor 7 mounted on its surface facing the interior 6 of the refrigerating device. Such an infrared sensor can detect the intensity of infrared radiation in various spectral ranges and allows the temperature of the radiation source to be inferred from the intensity distribution. This infrared sensor can, for example, be of a similar type to those used in so-called “ear thermometers” for measuring body temperature. The infrared radiation from the interior of a refrigerating device is certainly significantly weaker and on average of longer wavelength than that of the human body but the requirements on the measurement accuracy for regulating a refrigerating device are significantly lower than those for body temperature measurements so that such an infrared sensor is considered suitable for regulating a refrigerating device.

[0018] The attachment of the board 5 with the control circuit in the front area of the refrigerating device has the advantage that it is possible to mount display elements such as a light-emitting diode 8 on the board 5, said display elements being visible for a user through a window 9 of the screen 4 so that the user can easily confirm that the refrigerating device is operating correctly at any time. Regulators, for example, for setting a desired temperature of the interior, can also be mounted directly on the board 5 and are nevertheless easily accessible for a user.

[0019] The infrared sensor 7 is located opposite a window 10 let into the front side 2 and made of an infrared-transparent material, through which the characteristic thermal radiation of a black body 11 mounted in the interior 6 can pass substantially unhindered onto the radiation-sensitive surface of the infrared sensor 7.

[0020] With the aid of the black body 11 it is possible to specifically measure the temperature in a critical area of the interior 6. Such an area is precisely the front upper area of the interior 6, where the black body 11 is shown in the figure because the highest temperatures of the interior are generally established here as a result of the heat inflow into the interior 6 which is strongest along the edges of the door 3.

[0021] However, it is also possible to omit the black body 11 so that the infrared sensor 7 to a certain extent has a “free view” into the interior 6 through the window 10. In thermal equilibrium this interior 6 also has the radiation characteristic of a black body; so that by omitting the black body 11, a temperature averaged over the entire field of view of the infrared sensor 7 can be measured using the infrared sensor 7. Such an arrangement has the peculiarity that the measurement values detected by the infrared sensor 7 can be “falsified” if chilled goods which have only just been loaded into the refrigerating device and have not yet acquired its inner temperature, are located in its field of view. The infrared radiation power of a body increases substantially more strongly than linearly with its temperature. Such “warm” chilled goods can thus to a certain extent “swamp” their cold environment. In such a case, the temperature detected by the infrared sensor is higher than the arithmetic mean of the temperature formed taking into account the “warm” chilled goods. However, such a falsification can be absolutely desirable because it allows the refrigeration capacity of the refrigerating device to be set high before the heat brought in with the new chilled goods has spread in the interior. In this way, heating of the interior by newly brought-in relatively warm chilled goods is reliably prevented without any expensive circuitry measures being required for this.

[0022] FIG. 2 shows a section similar to that in FIG. 1 through a further developed variant of a refrigerating device according to the invention. In addition to the elements already shown in FIG. 1 and described above, FIG. 2 also shows part of the back wall 13 of its housing and an evaporator plate 14 arranged thereon. In this variant the window 10 is replaced by a lens 15 which is made of the same material as the window 10 and can be let into the front side 2 of the housing in a corresponding fashion.

[0023] The lens 15 has the effect that the field of view 16 of the lens delimited by the dashed lines in FIG. 2 is limited compared with the embodiment in FIG. 1 and merely covers a limited area 17 of the evaporator plate 14. With this arrangement the temperature of the evaporator plate 14 can be precisely monitored transversely through the interior 6.

[0024] Since the infrared sensor 7 is not itself exposed to the temperature fluctuations in the evaporator plate, its lifetime is not adversely influenced hereby and disturbances in the operation of the refrigerating device are avoided.

[0025] Various further developments of the embodiments described above are possible within the framework of the present invention. For example, it is feasible to mount a plurality of infrared sensors on the board 5, each monitoring a field of view in the interior 6 of the refrigerating device via their own window. Such differentiated temperature monitoring makes it possible for the control circuit to differentiate, for example, between newly inserted chilled goods, which merely lead to locally increased measured temperature values, and a general functional disorder when the temperature of the entire interior 6 rises as a result of failure of the cooling.

Claims

1. A refrigerating device with a temperature sensor for detecting an operating temperature of the device, characterised in that the temperature sensor is an infrared sensor (7).

2. The refrigerating device according to claim 1, characterised in that the operating temperature is the temperature of an interior (6) of the refrigerating device.

3. The refrigerating device according to claim 2, characterised in that the infrared sensor (7) is in visual contact with a black body (11) located in the interior (6).

4. The refrigerating device according to claim 1, characterised in that the operating temperature is the temperature of an evaporator (14) of the refrigerating device.

5. The refrigerating device according to claim 4, characterized in ithat the infrared sensor (7) is in visual contact with a surface of the evaporator (14) facing the interior (6) of the refrigerating device.

6. The refrigerating device according to one of the preceding claims, characterised in that the infrared sensor (7) is connected to a control circuit for the operating temperature and is located in the immediate neighhourhood thereof.

7. The refrigerating device according to claim 6, characterised in that the infrared sensor (7) is located on a common board (5) with the control circuit.

8. The refrigerating device according to one of the preceding claims, characterised in that the temperature sensor is attached in a non-refrigerated outer area of the refrigerating device and is separated from a measuring surface to be monitored by means of an infrared-transparent window (10, 15).

9. The refrigerating device according to claim 8, characterised in that the temperature sensor is accommodated below a front screen (4) of the refrigerating device.

10. The refrigerating device according to one of the preceding claims, characterised by a lens (15) for imaging a measuring surface (17) on a radiation-sensitive surface of the temperature sensor.