Temperature Sensor

Abstract

A temperature sensor is disclosed. In an embodiment a temperatures sensor includes a sensor element, a sheath surrounding the sensor element and a ring surrounding the sensor element, wherein the ring is covered by the sheath.

Claims

1-15. (canceled)

16. A temperature sensor comprising: a sensor element; a sheath surrounding the sensor element; and a ring surrounding the sensor element, wherein the ring is covered by the sheath.

17. The temperature sensor according to claim 16, further comprising a housing, wherein the sensor element, the ring and the sheath are arranged inside the housing.

18. The temperature sensor according to claim 16, wherein the ring has a higher thermal conductivity than the sheath.

19. The temperature sensor according to claim 16, wherein the ring comprises a ceramic material.

20. The temperature sensor according to claim 16, wherein the ring has a lower thermal conductivity than the sheath.

21. The temperature sensor according to claim 16, wherein a material of the ring comprises a plastic.

22. The temperature sensor according to claim 16, wherein the ring is fixed to the sensor element the sheath.

23. The temperature sensor according to claim 16, wherein the ring and the sensor element are separate components.

24. The temperature sensor according to claim 16, wherein the ring is fitted onto the sensor element.

25. The temperature sensor according to claim 16, wherein the ring partially covers a supply lead of the sensor element.

26. The temperature sensor according to claim 16, wherein the sensor element has a sensor head consisting essentially of an NTC material, and wherein the ring covers a contact point between the sensor head and the supply lead.

27. The temperature sensor according to claim 16, wherein the sheath comprises a thermal conductive paste, or wherein the sheath has a thermally conductive encapsulation.

28. The temperature sensor according to claim 16, wherein the temperature sensor is a temperature gauge configured to be uses in small appliances in the domestic, automotive or heating engineering sectors.

29. An assembly comprising: the temperature sensor according to claim 16; and a controller connected to the temperature sensor.

30. The assembly according to the claim 29, wherein a response of the temperature sensor is matched to the response of the controller.

31. The assembly according to claim 29, wherein a response of the temperature sensor is matched to the response of the controller by a suitable choice of a material of the ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the following, a preferred exemplary embodiment of the present invention is described based on the figures:

[0026] FIG. 1 shows a cross section through a temperature sensor; and

[0027] FIG. 2 shows a temperature sensor in a perspective view.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0028] FIG. 1 shows a cross section through a temperature sensor 1. The temperature sensor 1 comprises a sensor element 2. The sensor element 2 is an NTC element. In particular, it is a wired NTC element. The sensor element 2 has a sensor head 2a, which is made of an NTC material, and supply leads 2b, 2c. The supply leads 2b, 2c are thin long wires. The sensor head 2a is connected to two supply leads 2b, 2c, via which an electrical voltage can be applied to the sensor head 2a.

[0029] The sensor element 2 is arranged in a housing 3. The housing 3 is in the form of a sleeve. The housing 3 comprises a metallic material. The metallic material of the housing 3 has a high thermal conductivity and is therefore well suited for use in a temperature sensor 1. However, the material of the housing 3 also has an electrical conductivity, so that contact between the sensor element 2 and the housing 3 must be prevented in order to ensure a high electrical breakdown strength of the sensor element 2 and to prevent a short circuit.

[0030] The housing 3 has a front end 3a and a tail end 3b located opposite to the front end 3a. The housing 3 is closed at its front end 3a. The sensor head 2a is arranged inside the housing 3 and near the front end 3a of the housing 3. The supply leads 2b, 2c extend out of the tail end 3b of the housing.

[0031] The temperature sensor 1 also comprises a sheath 4, which surrounds the sensor element 2. The sheath 4 is arranged inside the housing 3. In particular, the sheath 4 surrounds the sensor head 2a and a part of the supply leads 2b, 2c which is attached directly to the sensor head 2a. A rear part of the supply leads 2b, 2c facing away from the sensor head 2a is not surrounded by the sheath 4.

[0032] The sheath 4 can be a potting compound or a thermal conductive paste.

[0033] The sensor element 2 and the sheath 4 are arranged inside the housing 3. The sensor element 2 is connected to the housing 3 via the sheath 4 and fixed inside the housing 3. The material of the sheath 4 is not electrically conductive, in order to avoid short-circuiting the sensor element 2. The material of the sheath 4 should have a high thermal conductivity in order to be able to pass temperature changes readily on to the sensor element 2.

[0034] In addition, the temperature sensor 1 has a ring 5 that encloses the sensor element 2. In particular, the ring 5 encloses contact points 6 at which the supply leads 2b and 2c are attached to the sensor head 2a. The ring 5 partially overlaps with the sensor head 2a.

[0035] The material of the ring 5 influences the thermal conductivity of the temperature sensor 1. The response speed of the temperature sensor 1 is directly dependent on the thermal conductivity of the temperature sensor 1. If the housing 3, the sheath 4 and the ring 5 have a high overall thermal conductivity, temperature changes can be passed on to the sensor element 2 very quickly, which results in a short response time of the temperature sensor 1. Overall thermal conductivity in this context refers to the resulting thermal conductivity for the unit consisting of the housing 3, the sheath 4 and the ring 5, wherein the overall thermal conductivity is determined by the thermal conductivities and the material quantities of the housing 3, the sheath 4 and the ring 5.

[0036] If, on the other hand, the unit formed by the housing 3, the sheath 4 and the ring 5 has a low overall thermal conductivity, this results in a slow response speed of the temperature sensor 1, as temperature changes cannot be quickly passed on to the sensor element 2. By suitable choice of the material of the ring, it is thus possible to adjust the response speed of the temperature sensor 1 in a desired manner.

[0037] For example, the ring 5 may consist of a ceramic material, the thermal conductivity of which is greater than the thermal conductivity of the sheath 4. This can increase the response speed of the temperature sensor 1 compared to a temperature sensor that does not have such a ring. The coefficient of thermal conductivity of the ceramic material can be in a range between 3 W/mK to 40 W/mK, for example. The ceramic material can be aluminum oxide, zirconium oxide or other ceramic materials, for example.

[0038] Alternatively, the ring 5 may consist of a material, the thermal conductivity of which is lower than the thermal conductivity of the sheath 4. This can slow down the response speed of the temperature sensor 1 compared to a temperature sensor that does not have such a ring 5. The material of the ring 5 can comprise a plastic, for example. The coefficient of thermal conductivity of the material of the ring 5 can be, for example, between 0.15 W/mK and 0.5 W/mK.

[0039] In addition to the adjustment of the response speed of the temperature sensor 1 in a desired manner, the ring 5 can also improve the voltage breakdown strength of the temperature sensor 1. When the sensor element 2 is being installed in the sheath 4 there is a risk that the sensor element 2 will be damaged. In particular, the supply leads 2b, 2c can become pinched or kinked if the sensor element 2 is inserted too deeply into the sleeve-shaped housing 3, which is filled with the material for the sheath 4. This may restrict the loading capacity of the supply leads 2b, 2c when a high voltage is applied. If the supply leads 2b, 2c are kinked or pinched during assembly such that they come into contact with an inner side of the housing 3, a short circuit may occur.

[0040] To prevent mechanical damage to the supply leads 2b, 2c during installing of the sensor element 2 in the housing 3, the ring 5 can be fitted onto the sensor element 2 before the sensor element 2 is installed in the housing. In particular, the ring 5 covers the contact points 6 of the supply leads 2b, 2c with the sensor head 2a. Accordingly, the ring 5 protects a mechanical weak point of the sensor element 2. The ring can prevent the supply leads 2b, 2c from becoming kinked or pinched when the sensor element 2 is installed in the housing 3, which is filled with the material of the sheath 4. This means the ring 5 can ensure that the sensor element 2 can be subjected to a high voltage, thus improving the electrical breakdown strength of the temperature sensor 1.

[0041] In the following text, the manufacturing method of the temperature sensor 1 is described:

[0042] The sheath 4 can be poured into the housing 3 as a material in liquid or paste form. Then the sensor element 2, on which the ring 5 has already been fitted, is inserted into the housing 3. The ring 5 is held on the sensor element 2 by friction forces.

[0043] The ring 5 is not irreversibly fixed to the sensor element 2 at this point.

[0044] The sensor element 2 is inserted far enough into the housing 3 that at least the sensor head 2a and the ring 5 are completely covered by the material of the sheath 4. Then the material of the sheath 4 is cured.

[0045] FIG. 2 shows the temperature sensor 1 in a perspective view. The temperature sensor 1 is a temperature measuring gauge. On an end of the supply leads 2b, 2c facing away from the sensor head 2a, a connector 7 is arranged, via which the temperature sensor 1 can be connected to a control unit, for example. The temperature sensor 1 can be used in small domestic appliances, in the automotive sector or in heating engineering.

[0046] By using the ring 5 that surrounds the sensor element 2, as described above, the response speed of the temperature sensor 1 can be adjusted as desired. In particular, the response speed can be set such that it matches the response speed of the control unit. The control unit can be the controller of a control loop.