Electrical heating assembly, aerosol-generating device and method for resistively heating an aerosol-forming substrate
The present invention relates to an electrical heating assembly of an aerosol-generating device for resistively heating an aerosol-forming substrate. The heating assembly comprises a control circuit configured to provide an AC driving current. The heating assembly further comprises an electrically resistive heating element comprising an electrically conductive ferromagnetic or ferrimagnetic material for heating the aerosol-forming substrate. The heating element is operatively coupled with the control circuit and configured to heat up due to Joule heating when passing an AC driving element provided by the control circuit current through the heating element. The present invention further relates to an aerosol-generating device for use with an aerosol-forming substrate, wherein the aerosol-generating device comprises a heating assembly according to the invention.
1. An aerosol-generating device for use with an aerosol-forming substrate comprising a heating assembly for restively heating the aerosol-forming substrate, the heating assembly comprising:
a control circuit configured to provide an AC driving current;
an electrically resistive heating element comprising an electrically conductive ferromagnetic or ferrimagnetic material for heating the aerosol-forming substrate, wherein the heating element is operatively coupled with the control circuit and configured to heat up due to Joule heating when passing an AC driving current provided by the control circuit through the heating element, wherein the heating element is a multi-layer heating element comprising at least one support layer and at least one heating layer, wherein at least the heating layer comprises the electrically conductive ferromagnetic or ferrimagnetic material and is an edge layer of the multi-layer heating element, and wherein a layer thickness of the at least one support layer is larger than a layer thickness of the at least one heating layers.
2. The aerosol-generating device according to claim 1 , wherein the multi-layer heating element comprises at least one further heating layer in addition to the at least one heating layer, the at least two heating layers sandwiching the support layer, wherein at least one of the heating layers comprise the electrically conductive ferromagnetic or ferrimagnetic material.
3. The aerosol-generating device according to claim 1 , wherein the at least one support layer comprises an electrically conductive material.
4. The aerosol-generating device according to claim 3 , wherein a resistivity of the electrically conductive material of the at least one or two heating layers is lower than a resistivity of the electrically conductive material of the at least one support layer.
5. The aerosol-generating device according to claim 1 , wherein a relative magnetic permeability of the electrically conductive material of the at least one or two heating layers is larger than a relative magnetic permeability of the electrically conductive material of the at least one support layer.
6. The aerosol-generating device according to claim 1 , wherein the electrically conductive material of the at least one or two heating layers is ferromagnetic or ferrimagnetic.
7. The aerosol-generating device according to claim 3 , wherein the electrically conductive material of the at least one support layer is paramagnetic.
8. The aerosol-generating device according to claim 2 , wherein the two heating layers are edge layers of the multi-layer heating element.
9. The aerosol-generating device according to claim 1 , wherein at least one layer of the multi-layer heating element is substantially made of a solid material.
10. The aerosol-generating device according to claim 1 , wherein the heating element is of a blade configuration or a rod configuration.
11. The aerosol-generating device according to claim 1 , wherein an AC resistance of the heating element is in a range between 10 mΩ and 1500 mΩ for an AC driving current passing through the heating element having a frequency in a range between 500 kHz and 30 MHz.