FLOW HEATER WITH CALORIMETRIC FLOW SENSOR

Abstract

A flow heater for vehicles is described. The flow heater has a housing, which has an inlet and an outlet. A flow channel for fluid to be heated is disposed in the housing and leads from the fluid inlet to the fluid outlet. A heating plate forms a wall of a heated section of the flow channel and carries an electric heating resistor. A calorimetric flow sensor is provided for measuring a fluid flow in the flow channel.

Claims

1. A flow heater for vehicles, comprising: a housing having an inlet and an outlet; a flow channel configured for liquid to be heated and leading from the inlet to the outlet; a heating plate forming a wall of a heated section of the flow channel, the heating plate carrying an electrical heating resistor; and a calorimetric flow sensor configured for measuring a flow in the flow channel.

2. The flow heater according to claim 1, wherein the flow sensor comprises a sensor resistor as a sensor element, which is formed as a conductive track.

3. The flow heater according to claim 2, wherein the conductive track is arranged on the housing.

4. The flow heater according to claim 2, wherein the conductive track is arranged on the heating plate.

5. The flow heater according to claim 2, wherein the conductive track is a printed conductive track.

6. The flow heater according to claim 2, wherein the conductive path contains metal particles.

7. The flow heater according to claim 2, wherein the heating resistor is a conductive track.

8. The flow heater according to claim 7, wherein the heating resistor is a conductive track, which contains ceramic particles.

9. The flow heater according to claim 1, wherein the flow sensor is connected to a control device, which switches off the electrical heating resistor if the measured flow drops below a predetermined threshold value.

10. The flow heater according to claim 1, wherein the flow sensor is located closer to the inlet than the heating resistor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0017] FIG. 1 shows an illustrative embodiment of a flow heater for vehicles in a schematic exploded view; and

[0018] FIG. 2 shows a schematic sectional view of the flow heater.

DESCRIPTION

[0019] The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

[0020] FIGS. 1 and 2 show schematically a housing 1 of a flow heater without a cover. The housing 1 has an inlet 2 for liquid to be heated and an outlet 3 for heated liquid, which can be provided with integrated, or separately inserted, connections for fluid lines, as shown in FIG. 1. The housing 1 carries electrical connectors 4, for purposes of connecting the flow heater to the electrical system of a vehicle. In other embodiments, the connectors may also be fitted to the housing cover, which is not shown.

[0021] A flow guide plate 5 and a heating plate 6 are arranged inside the housing 1. Fluid entering the housing 1 through the inlet 2 flows between the flow guide plate 5 and the heating plate 6, as indicated by arrows in FIG. 2, to the outlet 3. The heating plate 6 thus forms a wall of a heated section of the flow channel, which leads from the inlet 2 to the outlet 3.

[0022] The heating plate 6 comprises a substrate, for example a metal plate, which carries a heating resistor 7. The heating resistor 7 is preferably arranged on the dry side of the heating plate 6. In the embodiment shown, the heating plate 6 is a steel sheet that is covered with an insulation layer 8, on which the heating resistor 7, shown only schematically in FIG. 1, is designed in the form of conductive tracks, which can be arranged in a meandering pattern, for example.

[0023] The heating resistor 7 can, for example, be a resistive layer, which contains ceramic and metal particles, in particular contains at least 10% by weight of ceramic particles. The heating resistor 7 can thus be printed on as a paste at low cost.

[0024] The heating plate 6 also carries a sensor resistor 9, which is also only shown schematically in FIG. 1. The sensor resistor 9 may be a conductive track of metal, for example of platinum. The sensor resistor 9 can also be printed on, for example by using a suitable platinum ink or similar.

[0025] For purposes of making contact with the heating resistor 7 and the sensor resistor, a printed circuit board with control electronics can be used, arranged, for example, above the heating plate 6, which is not shown in FIG. 1, and can be integrated in the cover, for example.

[0026] The sensor resistor 9 forms a calorimetric flow sensor, with which the quantity of liquid flowing from the inlet 2 to the outlet 3 can be determined. In operation, the sensor resistor 9 is heated with a predetermined electrical power, and is cooled by the liquid flowing past the heating plate. The temperature of the sensor resistor 9 thus depends on the flow rate. From the instantaneous electrical resistance of the sensor resistor 9, its temperature and thus the flow rate can be determined, using its resistance-temperature characteristic.

[0027] If the flow rate of the liquid to be heated falls below a critical threshold, a control device can reduce, or completely switch off, the electrical power of the heating resistor 7 to prevent any overheating.

[0028] While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

LIST OF REFERENCE SYMBOLS

[0029] 1 Housing [0030] 2 Inlet [0031] 3 Outlet [0032] 4 Connector [0033] 5 Flow guide plate [0034] 6 Heating plate [0035] 7 Heating resistor [0036] 8 Insulation layer [0037] 9 Sensor resistor