EP1260120A1

EP1260120A1 - Cooking surface comprising a temperature sensor

Info

Publication number: EP1260120A1
Application number: EP01921276A
Authority: EP
Inventors: Dan Neumayer; Monika Zeraschi; Markus Theine; Peter Vetterl; Franz Grätz; Uwe Has
Original assignee: BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2000-02-16
Filing date: 2001-02-08
Publication date: 2002-11-27
Anticipated expiration: 2021-02-08
Also published as: DE50114094D1; DE10006953A1; ATE400981T1; EP1260120B1; WO2001062047A1; US20030042246A1

Abstract

In a cooktop with a cooktop panel, in particular, made of glass ceramic, beneath which at least one heating element is disposed for heating up a cooking vessel to be placed on the cooktop panel, and with a temperature sensor for sensing temperature of the cooktop panel, in particular, the underside thereof within the heating element and is connected to a control unit for controlling the heating power of the heating element, the temperature sensor is connected to a heat-conducting element, which is in heat-conducting connection with the underside of the cooktop panel, and the element completely covers the temperature sensor in the upward direction toward the cooktop panel, to achieve sufficient measurement accuracy with a high standard of safety.

Description

Hob with temperature sensor

The present invention relates to a hob according to the preamble of claim 1, as well as a corresponding heating element and a suitable element

Such a hob is known from the publication DE 37 03 768 C2, whereby a device for detecting the temperature of a glass ceramic plate heated by means of heating coils or halogen lamps with a temperature sensor is disclosed.This sensor emits a signal corresponding to the temperature of the glass ceramic for a control circuit. The heating coils or the Halogen lamps are inside a pot-like

Iso carrier arranged and heat the glass-ceramic plate via direct radiation The edge of the iso-carrier lies against the underside of the glass-ceramic plate under spring tension, and the temperature sensor is arranged outside of the interior of the iso-carrier, but inside the heating element. The temperature sensor is still in contact with the underside of the glass-ceramic plate Heat-conducting connection, the temperature sensor being arranged in a receptacle in the edge of the iso-carrier, the receptacle is arranged at a distance x to the inside of the edge of the iso-carrier, the minimum value of which is selected such that the heating windings or the halogen lamps are produced when the heating windings or halogen lamps are switched on and off short-term temperature changes only have a negligible influence on the temperature sensor. The maximum value of the distance x is chosen so that the delay caused by the thermal conductivity of the glass ceramic plate has a small hysteresis in the control characteristic rese results As a distance x, widths of 3 mm to 6 mm have proven to be advantageous. The temperature sensor is in the inserted or printed receptacle on the top of the attachment, which is in the interior of the

Insulating support protrudes, is inserted and is in heat-conducting connection with the underside of the glass ceramic plate. The temperature sensor is held indirectly under spring tension on the underside of the glass ceramic plate in order to keep the heat transfer resistance between the glass ceramic plate and the temperature sensor small Furthermore, a heating element for a cooking unit with a temperature sensor is known from the document EP 0 021 107 A1. In order to maintain complete heating of the entire surface of the heating element and nevertheless to closely couple the temperature sensor of the controller to the heating, a heat transfer element in the form of a sheet is used, that is partially overlapping the heated area between the radiators and the glass ceramic plate, but protrudes from the heating element and is connected there to the temperature sensor of the controller. The heat transfer element is attached to the edge of the shell supporting the heating by clamping and is normally located on the underside the glass ceramic plate from the area of the heat-dissipating area

Heat transfer element protrudes an outer section outwards beyond the edge of the heating element. It is formed in one piece with the aforementioned area, essentially parallel to it, but offset slightly downward by a bend, so that the outer section does not abut the underside of the glass ceramic plate. The sensor socket of the temperature sensor is attached to the underside of the by a pressure spring

Printed heat transfer surface of the heat transfer element, which is supported on a holding mechanism that guides the sensor socket and is attached to the outer section of the heat transfer element. However, other sensor types and connections are also possible. For example, an electrical NTC or PTC sensor that is spring-loaded can also be used or is fixedly attached to the outer portion of the heat transfer element. The heat transfer element can, if desired, be grounded, which provides protection against contact

Furthermore, a glass ceramic cooktop is known from US Pat. No. 4,447,710, in which an insulation body is arranged in the edge region of the heating element, on which a

Temperature sensor, for example a thermocouple sits The thermocouple is kept in good thermal contact with the underside of the glass ceramic plate by means of the insulation block

The object of the present invention is. to provide a generic cooktop and a corresponding heating element that are simultaneously high

Safety standard and good measurement accuracy According to the invention this is achieved in that in a cooktop according to the preamble of claim 1, the temperature sensor is connected to a heat-conducting element which is thermally conductive to the underside of the cooktop plate, and in that the element completely covers the temperature sensor upwards towards the cooktop plate the heat-conducting element, the temperature sensor is on the one hand thermally well coupled to the underside of the cooktop and on the other hand the safety regulations regarding the 4 or 8 mm clearance and creepage distance between live parts and the glass ceramic cooktop are complied with. A complex implementation of the temperature measuring arrangement, for example in protective low voltage technology, is necessary not mandatory

To improve the safety of the arrangement, it is provided that the element also covers the electrical leads of the temperature sensor upwards to the cooking plate

According to a preferred embodiment, the element is at least in the area of the temperature sensor approximately hood-shaped and has an upper and short side walls. The 8 mm air and gap distance can be maintained without having to choose too large the base area of the hood. This is This is particularly important because, together with the temperature sensor, the hood is preferably to be shielded from the heat radiation from the heating element of the heating element, but the shielding area must not be chosen too large

In order to be able to easily pour the temperature sensor into the hood, for example with a high-temperature-resistant, heat-conducting ceramic adhesive, the hood is at least partially closed on the bottom side

In order to be able to assemble the element quickly and without errors, it is provided that the heat conducting element in the region of the outer peripheral wall of the heating element or

Isohertragers attached directly or with the help of an intermediate assembly part, in particular is screwed. In particular, it can be provided that the intermediate assembly part is attached in the bottom area of the heating element and extends into the area of the outer peripheral wall of the heating element in which the element is in turn screwed to the intermediate assembly part In order to be able to set the contact pressure or the contact surface of the element and thus, among other things, the thermal coupling of the element to the underside of the hob plate well, the element can be screwed onto the outer peripheral wall of the heating element at different heights

According to a preferred embodiment, the temperature sensor is attached to the underside of the element. On the one hand, this allows a large, flat contact surface to be improved to improve the heat conduction from the underside of the glass ceramic plate to the temperature sensor The unit falls down

Element / temperature sensor, better mechanically protected

To simplify assembly, the element can have a receiving section for the temperature sensor and a mounting section for fastening the element, in particular in the heating element, the receiving section being offset radially laterally to the mounting section.This is particularly important if the

Temperature sensor is to be installed in the immediate vicinity of a temperature limiter present on the heating element. The temperature limiter limits the mounting space in the area of the outer circumferential wall of the heating element, but on the other hand it is advantageous if the various electrical connections of the temperature limiter and the temperature sensor are as close as possible in a safety-related manner lie

Advantageously, the element is formed at least in two parts. A receiving part for the temperature sensor consists of a softer material in order to be able to optimally and geometrically form the receiving part in terms of application and safety technology. The rest of the element can consist of a different material, in particular a spring material being suitable, in order to be able to print the element on the underside of the glass ceramic plate It is particularly favorable in terms of production and assembly technology if the element is designed as a torsion spring, the torsion region of the spring element being provided essentially outside the heating element and thus in a cooler region

According to a preferred embodiment, the element is designed to be electrically conductive and grounded in order to optimally meet the safety regulations with a simple structure

In order to obtain sufficient measurement accuracy, both the temperature sensor and the element are adequately shielded from heat radiation emanating from a cardiac means of the heating element by means of an insulation body

To simplify assembly and in particular to relieve strain, the electrical lines of the temperature sensor are connected to a first connection section of the element or a connection piece mounted there. Accordingly, the element can also have a second connection section to which an earth line of the element is connected

Two exemplary embodiments of the hob and heating element or element for the heating element according to the invention are described below with the aid of schematic representations

1 is a sectional view substantially along the line l-l in FIG. 2, the hob with a heating element according to the first exemplary embodiment,

2 is a perspective view from above of the heating element alone according to the first exemplary embodiment,

3 on an enlarged scale in a perspective view from below the heat conducting element from FIG. 1 and FIG. 2 without the temperature sensor,

4 shows a section from above of the heating element with the heat-conducting element according to the second exemplary embodiment and 5 shows a block diagram of the hob according to the invention

A cooktop 1 has a cooktop plate 3, in particular made of glass ceramic (Fig. 1) Below the cooktop plate 3, in a manner known per se, various heating elements 5 of the cooktop are provided, which are printed in a known manner on the underside of the cooktop plate 3 (not shown). In the area of the heating element 5 is the

The top of the cooktop 3 is usually appropriately decorated in this heated area. A cooking vessel 6 can be placed down is spaced from the plate (Fig 1) In the heated state, this air gap decreases or ideally becomes approximately zero due to the known thermally induced movement of the pot bottom. The heating element 5 has a cup-like tin pot 7, in which a circular disk-shaped insulation plate 9 is also inside Tin pot 7 on the insulation plate 9, an inner insulation ring 11 and an outer insulation ring 13 are provided in accordance with a two-circuit heating arrangement. As a result, the interior of the heating element 5 is separated into an inner and an outer heating area, in each of which there is a band heater iter 15 extends (Fig 1, Fig 2) in a conventional manner in the region of the outer peripheral wall of the tin pot 7, a heat conductor connection part 17 is attached, which is conductively connected on the one hand to the band heater 15 and on the other hand to electrical, not shown

Supply lines of the hob 1 can be connected (FIG. 2). The heating element 5 also has a temperature limiter 19 known per se, the rod of which extends across the heated area of the heating element. The connection block of the temperature limiter 19 has the known and customary, laterally flared contact pins for connection to the power supply line or to the

Heat conductor connection part 17 of the heating element 5 An insulation block 21 is arranged in the area of the temperature limiter 19 between the inner insulation ring and the outer insulation ring 13 In the edge area of the insulation block 21, a receiving recess 23 is milled in the upper side thereof. A heat conducting element 25 with its element cover 27 is arranged in this (FIG. 1, 2, 3) note that the hood 27 does not sit directly on the bottom of the recess 23, so that the hood 27 can yield slightly in the event of an impact on the hob plate 3, thereby preventing damage or breakage of the plate 3, in particular if it is made of glass or Glass ceramic material is

In the receiving space formed by the element cover 27, a PT-500 sensor with its sensor lines 30 is embedded and thereby fastened and guided by means of a temperature-resistant and heat-conductive ceramic adhesive 28 as the temperature sensor 29. The material of the element cover 27 is X7 steel and the cover 27 is for this purpose designed as a bent part The hood material must have sufficiently good heat conduction properties, must be easily deformable, as explained below, but sufficiently mechanically stable over the entire temperature range of up to 350 - 400 ° C, and maintain its properties even at these temperatures from the section serving as the top wall of the element hood 27, two side walls 31 are bent down essentially at right angles (FIG. 3). Also bent at right angles to the rare walls 31, bottom walls 33 delimit a slot-shaped open bottom of the element hood 27 The end wall 35 bent at an angle from the top wall is closed. The hood-shaped design of the element 25 ensures that the air and creepage distance prescribed in terms of safety technology to the live temperature sensor 29 in the event of a break in the hob plate

3 is adhered to without having to make the base area of the element 25 or the hood 27 and thus the insulation block 21 too large. More precise designs for the geometric design and arrangement of the temperature sensor 29, the element 25 and the insulation block 21 are described in connection with the description of the in 5 sketched third exemplary embodiment made. The hood 27 is firmly connected to an essentially L-shaped hood support 37 made of steel, preferably welded. For this purpose, the element hood 27 is seated on a connecting section 39 of the hood carrier 37 (FIG. 3) arranged slightly higher than the top of the hood support 37 and defines and delimits a flat area A, in which the element 25 rests on the underside of the cooktop plate 3 (FIG. 1, 2, 5) due to the overlapping connection of the hood 27 and the hood ager 37 is also the stability of the Connection increased While the hood support 37 is made of 0.8 mm thick material in order to be suitable for the earthing plug connections described below, the element hood 27 is made of thinner material, which further simplifies its reshaping

The hood carrier 37 merges into a mounting section 43 in a spring section 41

(Fig. 2, 3) The spring section 41 is arranged essentially outside of the heated area of the heating element 5 or the outer isolating ring 13. The mounting section 43 of the hood support 37 has a mounting plate 45 bent downwards at right angles with mounting openings 47 25 adjustable to a high degree via an intermediate mounting part 48 on the outer circumferential wall of the tin pot 7 (FIG. 2). For this purpose, it is provided that the intermediate mounting part 48 is screwed on the underside of the tin pot 7 into the bottom thereof (not shown). This part 48 extends approximately L- shaped from the bottom of the heating element to its side wall 7 in the side wall area, the heat-conducting element 25 is then screwed to the intermediate mounting part 48 and the position of the heat-conducting element 25 can thus be defined to a high degree. Thus, complex screwing openings in the side wall of the tin pot 7 can be omitted and d The openings that are always present on the bottom side in the tin pot can be used as an alternative. However, the heat-conducting element 25 can also be screwed to the outer wall of the tin pot 7 in the area of the mounting openings 47. Furthermore, a connection part can be fastened in the mounting openings 47 (not shown), with which the Electrical sensor lines 30 of the temperature sensor 29 can be connected, for example plugged in, and to which, on the other hand, electrical connection lines of a control unit 101 (FIG. 6) of the hob 1 are connected. This provides a secure strain relief for the sensor lines 30. The connecting part also has to ensure that the electrical connections of the PT temperature sensor 29 are insulated from ground or from the grounded hood support 37. The temperature sensor and the sensor lines 30 are covered over their entire length by the heat conducting element 25 on the top side for better routing of the lines 30 this at the bottom of the element 25 in

Area of the hood support 37 glued and / or held by guide elements formed on the support 37 Furthermore, the mounting plate 45 has a flat pin 49, to which a grounding line 51 or its standardized AMP plug of the hob can be plugged in directly. As a result, the heat-conducting element 25 is connected to ground potential. It must be ensured that the ohmic resistance of the element 25 is 0.1 ohm or less, in order to withstand a continuous current load of at least 25 A

The heat-conducting element 25 should also not be too stiff in order to be able to yield in a suitable manner under mechanical load or movement of the hob plate 3. Otherwise, due to the element 25 or the element hood 27 being too rigidly attached to the hob plate 3, flaked-off chips on the underside of the plate 3 or if necessary, also to fear their breakage. It should also be noted that a

Improvement of the heat conduction from the underside of the hob plate 3 to the heat conducting element 25 can be achieved if the spaces between the knobs formed on the underside of the glass ceramic plate are filled with a heat-conducting paste or a suitable adhesive

According to the second exemplary embodiment according to FIG. 4, the heat-conducting element 85, for example in the form of a hood, has an element hood 87 which corresponds to that of the first exemplary embodiment. In contrast to the first exemplary embodiment, an assembly section 89 of the hood carrier 37 is, however, not arranged radially offset to the receiving section of the element hood 87 Rather, the mounting section 89 extends in the extension of the element hood 87 along the radial offset

Outer wall of the tin pot 7 vertically downward. FIG. 4 schematically shows the area A in which the heat-conducting element 85 is in thermal contact with the underside of the hob plate 3. The size of the area is approximately 50 to 100 mm ^{2. It} is also shown that the contact area A is approximately 10 times larger than a base area B of the temperature sensor 29.This ensures, among other things, that the temperature on the underside of the hob plate is not determined by the temperature sensor in a quasi-punctiform manner, but integrally over a larger area.This is particularly important because the respective pan diameter and its soil quality are not exactly known and can also vary from pan type to pan type.

Distance a of the element 85 to the edge region of the insulation material 21 is approximately 8 mm. This provides an optimal geometry, which has the following advantages for the precise control of the heating power or the temperature, especially during roasting in pans 6 placed on the hob 3 enough to be a disadvantage when heating or roasting

To be able to prevent shading of the cooking vessel base 6 and an undesirably uneven heat distribution in the pan base caused thereby. In particular, the heat conducting element 25 is still sufficiently thermally coupled to the area of the hob plate which is heated directly by the heat radiation from the heart means 15. This is also the case with the first and the second Exemplary embodiment achieved, wherein at the same time the temperature sensor 29 is covered with respect to the hob plate 3 by an earthed protective element 27, taking into account the 4 or 8 mm gap and air gap required by the regulations. Also by increasing the area thermally in contact with the underside of the hob plate 3 achieved that, despite all assembly tolerances, a sufficiently good warm contact between the flat-sized, smaller temperature sensor and the hob plate 3 is established. This is particularly important when a glass-ceramic knurled on the underside The ochfeldplatte 3 is used whose knob geometry is in the order of magnitude of the temperature sensor 29. The above statements regarding the design of the geometries, distances and large ratios apply to all exemplary embodiments

Measuring surface A is coupled to the underside of the cooktop plate by a high-temperature lubricant, which consists in particular of glass ceramic material, in order to achieve improved heat transfer and improved damping under impact loads

5 shows a schematic block diagram which shows the most important components of the hob. The control unit 101 regulates the heating output of the

Strip heating conductor 15 corresponding to the measured values of the temperature sensor 29 to the target value specified by an input unit 103. In this way, it can be achieved in particular that scorching is almost impossible during roasting

Claims

claims

1. hob with a hob plate (3), in particular made of glass ceramic, below which at least one heating element (5) is arranged, for heating a cooking vessel that can be placed on the hob plate, and with a temperature sensor (29) for detecting the temperature of the hob plate, which temperature sensor inside the heating element, the temperature of the underside of the hob plate senses and is connected to a control unit (101) for controlling the heating power of the heating element, characterized in that the temperature sensor (29) is connected to a thermally conductive element (25; 85) which is thermally conductive with the underside of the hob plate (3) is connected, and that the element (25; 85) completely covers the temperature sensor (29) upwards towards the hob plate (3).

2. Hob according to claim 1 or 2, characterized in that the temperature sensor (29) and the element (25; 85) are shielded by means of insulation material (21) against the heat radiation of the cardiac agent (15).

3. Hob according to claim 1, 2 or 3, characterized in that the element (25; 85) covers electrical leads (30) of the temperature sensor (29) up to the hob plate (3).

4 Hob according to one of the preceding claims, in particular according to claim 2, characterized in that the element (25; 85) is at least in the area of the temperature sensor (29) is approximately hood-shaped and has an upper and apron-like side walls (31; 35) ,

5 hob according to claim 4, characterized in that the hood (27; 87) is at least partially closed on the bottom. Hob according to claim 4 or 5, characterized in that the material of the hood (27, 87) is X7 steel or X10 steel

Hob according to one of the preceding claims, characterized in that the element (25, 85) is grounded outside the heating element (5)

Hob according to claim 7, characterized in that the value of the ohmic resistance of the element (25, 85) is less than about 0.1 ohm

Hob according to claim 7 or 8, characterized in that the element (25) has a second connection section (49) to which an earth line (51) of the element (25) is connected

Hob according to one of the preceding claims, characterized in that the element (25) has a first connection section (47) to which the electrical lines (30) of the temperature sensor (29) are connected

Hob according to one of the preceding claims, characterized in that the temperature sensor (29) is attached to the element (25, 85) and is attached to it

Hob according to one of the preceding claims, characterized in that the element (25, 85) is designed as a spring element and is printed in the area of the temperature sensor (29) against the underside of the hob plate (3)

Heating element for a hob according to one of the preceding claims

Element for a heating element according to claim 13