TRANSMISSION UNIT COMPRISING A TRANSMISSION COIL AND A TEMPERATURE SENSOR

Abstract

The invention relates to a transmitter unit (12) comprising a housing (20), a transmitter coil (18) arranged in the housing (20) for inductively transferring electrical energy to a receiver unit (14) which is provided with a receiver coil (16) and is arranged in the tissue (2) of the body (1) of a patient when the housing (20) having a contact surface (22) is placed on the body (1), and comprising a control device (30) for controlling the operation of the transmitter coil (18). According to the invention, a temperature sensor (26) is provided in the transmitter unit for determining a heating of the tissue (2) of the body (1) caused by the inductive transfer of electrical energy to the receiver unit (14). The invention also relates to methods for determining the temperature (T.sub.Korr) of the tissue (2) of a body (1) on a surface (38), by which electrical energy is inductively transmitted for supplying an electrical consumer arranged in the tissue (2) of the body (1), and to a method for inductively transferring electrical energy.

Claims

1.-27. (canceled)

28. A transmitter unit comprising: a housing comprising a transmitter coil configured to inductively transfer electrical energy to a receiver unit disposed in a part of a body of a patient in response to a contact made between a contact surface of the housing and the body of the patient, the receiver unit comprising a receiver coil; a temperature sensor configured to determine an increase in local temperature of the body caused by the inductive transfer of electrical energy to the receiver unit; and a control device configured to control operation of the transmitter coil based at least in part on the increase in local temperature of the body, wherein the control device stores a temperature determination routine configured to determine a local temperature at a surface of the body based at least in part on temperature measurement signals of the temperature sensor; wherein the temperature determination routine is configured to stop the operation of the transmitter coil at a first time point and contains an algorithm configured to calculate the local temperature based at least in part on a decay curve determined based at least in part on the temperature measurement signals from the temperature sensor after the first time point, wherein the temperature determination routine is configured to account for warming of the temperature sensor caused by eddy currents.

29. The transmitter unit of claim 28, wherein the transmitter coil is disposed in the housing and the temperature sensor is positioned between the transmitter coil and the contact surface.

30. The transmitter unit of claim 29, wherein the transmitter coil comprises conductor loops configured to form a coil winding around a coil axis that passes through and orthogonal to the contact surface.

31. The transmitter unit of claim 30, wherein the conductor loops are disposed on or in a transmitter coil carrier extending in a planar manner and parallel to the contact surface.

32. The transmitter unit of claim 31, wherein the transmitter coil carrier comprises a carrier surface which faces the contact surface of the housing.

33. The transmitter unit of claim 28, wherein the temperature determination routine is configured to account for an operating state of the transmitter coil.

34. The transmitter unit of claim 28, wherein the algorithm is configured to calculate the local temperature at the surface of the body based at least in part on extrapolation of the decay curve from a second time point following the first time point to the first time point.

35. The transmitter unit of claim 34, wherein the algorithm is configured to linearly extrapolate the progression of the decay curve from a second time point to the first time point.

36. The transmitter unit of claim 28, wherein the algorithm is configured to subtract a fixed correction value from temperature values corresponding to the temperature measurement signals.

37. The transmitter unit of claim 28, wherein the control device stores a shutdown routine configured to stop the operation of the transmitter coil, wherein the shutdown routine is configured to prevent or reduce the inductive transfer of electrical energy to the receiver unit when the local temperature determined by the temperature determination routine exceeds a threshold value.

38. The transmitter unit of claim 28, wherein the temperature sensor is at least one of: a surface-mount-device component, a temperature-dependent measuring resistor, and a thermocouple.

39. A system comprising: a temperature sensor; a transmitter coil; a memory storing computer-readable instructions; a processor configured to communicate with the temperature sensor, the transmitter coil, and the memory, wherein the computer-readable instructions, when executed, cause the processor to: prevent an inductive transfer of electrical energy from the transmitter coil at a first time point; determine temperatures of a surface of a body at a plurality of time points following the first time point; determine a decay curve based at least in part on the temperatures measured at the plurality of time points following the first time point; and calculate a local temperature of the surface of the body based at least in part on the decay curve and an algorithm configured to account for an effect of the inductive transfer of electrical energy from the transmitter coil to an electrically powered device.

40. The system of claim 39, wherein the algorithm is configured to determine the local temperature of the surface of the body at least in part by extrapolating a progression of a section of the decay curve from a second time point following the first time point to the first time point.

41. The system of claim 40, wherein the algorithm is configured to extrapolate the progression of the section of the decay curve based at least in part on a comparison of the decay curve with one or more decay curve progressions stored in the memory.

42. The system of claim 40, wherein the algorithm is configured to linearly extrapolate the progression of the decay curve from the second time point to the first time point.

43. The system of claim 40, wherein the preventing the inductive transfer of electrical energy from the transmitter coil at the first time point, the measuring the temperatures at the surface at the plurality of time points following the first time point, the determining the decay curve from the temperatures measured at the plurality of time points following the first time point, and the calculating the local temperature at the surface of the body based at least in part on the decay curve and the algorithm configured to account for an effect of inductive transfer of electrical energy from the transmitter coil to the electrically powered device are repeated continuously.

44. A method for determining a local temperature at a surface of a human body, wherein electrical energy for an electrical energy storage or an electrically powered device disposed in the body is inductively transferred through the surface, the method comprising: preventing an inductive transfer of the electrical energy at a first time point; determining temperatures measured at the surface at a plurality of time points following the first time point; determining a decay curve based at least in part on the temperatures measured at the surface at the plurality of time points following the first time point; and calculating the local temperature at the surface based at least in part on the decay curve and an algorithm accounting for an effect of the inductive transfer of electrical energy to the electrical energy storage or the electrically powered device.

45. The method of claim 44, wherein the algorithm is configured to extrapolate a progression of a section of the decay curve from a second time point following the first time point to the first time point.

46. The method of claim 45, wherein the algorithm is configured to extrapolate the progression of the section of the decay curve based at least in part on a comparison of the decay curve to one or more decay curve progressions stored in a data memory.

47. The method of claim 45, wherein the algorithm is configured to linearly extrapolate the progression of the decay curve from the second time point to the first time point.

Description

[0020] Further advantages, features and details of the invention emerge from the following description of preferred design examples. These are shown schematically in the drawings and are described below.

[0021] The figures show:

[0022] FIG. 1 an apparatus for inductively transferring energy comprising a transmitter coil and comprising a temperature sensor, which is used for inductively transferring energy into a receiver unit having a receiver coil in a VAD system disposed in a human body;

[0023] FIG. 2 a first diagram with the temporal progression of a temperature T registered by the temperature sensor in the apparatus for inductively transferring energy and with a limit temperature T.sub.Grenz, and

[0024] FIG. 3 a second diagram with the temporal progression of a temperature T registered by the temperature sensor in the apparatus for inductively transferring energy and with a limit temperature T.sub.Grenz.

[0025] The same elements or elements having the same function are provided with the same reference signs in the figures.

[0026] FIG. 1 shows the essential components of an apparatus 10 for inductively transferring energy on a receiver unit 14 disposed in the body 1 of a patient and having a receiver coil 16 in a highly simplified manner. The apparatus 10 is in particular a component of a cardiac support system in the form of a so-called ventricular assist device system (VAD system) 100. The VAD system 100 in particular includes a pump disposed in the body 1 of the patient, which supports the patient's heart function. In the body 1 of the patient, this pump is operated with electrical energy from an electrical energy store not shown in FIG. 1, e.g. a rechargeable battery, which is connected to the receiver unit 14. This electrical energy store has to be charged due to the energy consumption of the pump. By inductively transferring energy into the receiver unit 14 by means of the apparatus 10, the electrical energy store connected to the receiver unit 14 is charged.

[0027] The apparatus 10 comprises a transmitter unit 12 outside the body 1 of the patient and the receiver unit 14 with the receiver coil 16 disposed inside the body 1 of the patient. It should be noted that the receiver unit 14 may in principle comprise a plurality of receiver coils 16.

[0028] Between the transmitter unit 12 and the receiver unit 14 there is human tissue 2 or the skin of the patient. The receiver coil 16 is disposed in operative connection with the electrical energy store to be charged. The receiver coil 16 cooperates with a transmitter coil 18 disposed in the transmitter unit 12. The transmitter coil 18 is disposed inside a housing 20 of the transmitter unit 12, whereby the housing 20 is disposed at least in indirect contact with the body 1 or the tissue 2 in the region of a contact surface 22 of the housing 20.

[0029] The transmitter coil 18 has a coil winding 17, which comprises conductor loops disposed around a coil axis 19 that passes through the contact surface 22. The coil winding 17 of the transmitter coil 18 is located on a transmitter coil carrier 21, which extends in a planar manner and through which the coil axis 19 passes, and which has a carrier surface that faces the contact surface 22 of the housing 20 for the coil turns of the transmitter coil 18.

[0030] To operate the apparatus 10, it is also necessary for the receiver coil 16 and the transmitter coil 18 to be aligned with one another in order to be able to produce a magnetic field when current is supplied to the transmitter coil 18. The field lines 24 of this magnetic field, which are shown in FIG. 1, lead to the induction of an electrical voltage and thus to the flow of an electrical current in the receiver coil 16, which can then be used to charge the electrical energy store.

[0031] During operation of the transmitter coil 18, the tissue 2 of the body 1 located between the transmitter unit 12 and the receiver unit 14 is warmed by the loss-related warming of the transmitter unit 12 and the receiver unit 14. This warming of tissue 2 has to be limited to avoid physical impairments or damage and/or to comply with legal standards.

[0032] For this purpose, it is provided that the temperature of the tissue 2 in the region of contact of the housing 20 of the transmitter unit 12 with the tissue 2 is monitored by means of a temperature sensor 26 in the region of a measurement surface 38 on the surface of the tissue 2.

[0033] The temperature sensor 26 is disposed in the housing 20 of the transmitter unit 12 on a side 23 of the transmitter coil 18 facing the contact surface 22.

[0034] To make the design as compact as possible, it is in particular provided that the temperature sensor 26 is designed as an SMD component or an SMD assembly. The temperature sensor 26 is connected to a control device 30 of the transmitter unit 12 via an electrical lead 28. The control device 30 is also used to control the transmitter coil 18 via a lead 32. A further lead 34 connects the control device 30 to a further temperature sensor 36, which is configured to register the ambient temperature outside the transmitter unit 12.

[0035] As can be seen in FIG. 1, both the temperature sensor 26 and, if applicable, the lead 28 are disposed in operative connection with the magnetic field lines 24 of the transmitter coil 18. As a result, during operation of the transmitter coil 18, not only the tissue 2 is warmed, in particular by the lost heat from the transmitter unit 12 and the receiver unit 14, but also the temperature sensor 26 or the lead 28, in particular by the magnetic field of the transmitter coil 18, which can lead to the temperature sensor 26 heating up more than the surrounding tissue 2. This in turn has the consequence that the temperature increase of said components leads to a measurement error, which manifests itself in that the temperature T registered by the temperature sensor 26 in the region of the measurement surface 38 is falsified or increased by the measurement error.

[0036] To detect or take into account this measurement error or to register the actual temperature T on the measurement surface 38 of the body 1, the transmitter coil 18 is operated in a specific manner. For clarification, reference is made to FIG. 2.

[0037] FIG. 2 shows the temperature T registered by the temperature sensor 26 in the apparatus 10 at the time t as a curve progression A. The temperature sensor 26 transmits the temperature T registered at the time t to the control device 30.

[0038] The temperature T increases slightly in the period between t.sub.0 and t.sub.1. The increase in temperature T can be explained by the fact that, during operation of the transmitter coil 18, both the temperature in the tissue 2 and the temperature in the temperature sensor 26 or the lead 28 is increased by the effect of the temporally changing magnetic field produced by the transmitter coil 18, which causes eddy currents. However, the temperature T is below a limit temperature T.sub.Grenz that has to be observed. At the time point t.sub.1, the operation of the transmitter coil 18 is now stopped by the control device 30. The curve progression A then shows that the temperature T, which continues to be registered by the temperature sensor 26 and delivered to the control device 30 as an input quantity, decreases with the decay curve 40.

[0039] The curve progression A after the time point t.sub.1 results from both the now absent warming of the tissue 2, or its cooling, and from the heat dissipation or cooling of the temperature sensor 26 and the lead 28.

[0040] An algorithm with a mathematical function is stored in the control device 30 of the transmitter unit 12 or the apparatus 10, which makes it possible to infer the actual temperature T in the region of the measurement surface 38 at the time point t.sub.1 based on the values of the temperature T after the time point t.sub.1, for example by extrapolation from the cooling rate V.sub.K at a time point t.sub.2 after the time point t.sub.1. This makes use of the fact that, due to its size, the temperature sensor 26 has a significantly lower heat storage capacity than the surrounding tissue 2 and the surface of the housing 20. As a result, there is a dynamic drop in the temperature T immediately after the transmitter coil 18 is switched off at the time point t.sub.1. Once this temporary equalization process is completed at the time point t.sub.2, the temperature sensor 26 registers the actual temperature T of the tissue 2, because the low heat storage capacity of the temperature sensor 26 has been “discharged”. The mentioned extrapolation of the cooling curve at the switch-off time t.sub.1 can therefore be used to infer the actual temperature at the switch-off time t.sub.1. The additional warming of the temperature sensor 26 is thus taken into account or eliminated.

[0041] Alternatively, it can be provided that the curve progression A after the time point t.sub.1 is compared to curve progressions stored in the control device 30, and, if it matches or approximates a stored curve progression, the respective temperature T.sub.Korr at the measurement surface 38 of the body 1 at the time point t.sub.1 is inferred. The difference between the corrected temperature T.sub.Korr on the measurement surface 38 and the temperature T registered at the time point t.sub.1 is the component ΔW caused by the warming of the temperature sensor 26 and the lead 28.

[0042] As soon as the temperature T on the measurement surface 38, which has been corrected by the amount of warming of the temperature sensor 26 or the lead 28 caused by the operation of the transmitter coil 18, has been determined, the control device 30 again actuates the transmitter coil 18 in order to enable a further transfer of energy. In order to enable continuous monitoring of the (actual) temperature T on the measurement surface 38, the switching off or switching on of the transmitter coil 18 as described thus far is preferably carried out periodically, i.e. at regular intervals.

[0043] FIG. 3 shows a diagram that illustrates a simplified measurement procedure. Here, the temperature T registered by the temperature sensor 26 is again shown over the time t. A continuous, i.e. uninterrupted, operation of the transmitter coil 18 is assumed. The values of the temperature T transmitted by the temperature sensor 26 to the control device 30 are indicated by the curve progression A. The curve progression A.sub.K shows a corrected curve progression A taking into account a fixed value ΔF as the component ΔW, which is assumed to be the maximum possible measurement error resulting from the warming of the temperature sensor 26 and the lead 28 due to the warming caused by the operation of the transmitter coil 18. In other words, this means that the control device 30 assumes that the temperature T calculated using the A.sub.K is the highest possible temperature that can be present on the measurement surface 38.

[0044] Of course, in both methods it is respectively assumed that the operation of the apparatus 10 or the transmitter coil 18 is stopped when a limit temperature T.sub.Grenz is approached, for example until the determined temperature T has a specific separation from the limit temperature T.sub.Grenz.

[0045] The methods as described thus far can be altered or modified in a variety of ways without departing from the idea of the invention. It should in particular be noted that the described methods are not limited to use in a VAD system 100.

[0046] In summary, the following preferred features of the invention should in particular be noted:

[0047] A transmitter unit 12 comprises a housing 20 and a transmitter coil 18 disposed in said housing 20 for inductively transferring electrical energy to a receiver unit 14, which is disposed in the tissue 2 of the body 1 of a patient and comprises a receiver coil 16, when a contact surface 22 of said housing 20 is in contact with the body 1. The transmitter unit 12 comprises a control device 30 for controlling the operation of the transmitter coil 18. The transmitter unit comprises a temperature sensor 26 for determining a local warming of the body 1 caused by the inductive transfer of electrical energy into the receiver unit 14. The invention also relates to methods for determining the temperature (T.sub.Korr) of a body 1 on a surface 38 through which electrical energy for supplying an electrical energy store or an electrical consumer disposed in the body 1 is inductively transferred and to a method for inductively transferring electrical energy.

[0048] The invention relates, in particular, to the aspects specified in the following clauses: [0049] 1. Method for determining the temperature (T) on a surface (38) in apparatus (10) for inductively transferring energy, wherein the apparatus (10) comprises a transmitter coil (18) disposed in a housing (20) and the housing (20) is disposed at least in indirect contact with the to-be-measured surface (38), and comprising a temperature sensor (26) for registering the temperature (T) of the surface (38), wherein the temperature sensor (26) and, if applicable, the electrical lead (28) of said sensor is disposed in operative connection with the transmitter coil (18), such that, during operation of the transmitter coil (18), the temperature sensor (26) and, if applicable, the electrical lead (28) of said sensor is warmed by the fields emitted by the transmitter coil (18), so that the temperature (T) registered by the temperature sensor (26) includes a component (ΔW) that results from the warming of the temperature sensor (26) and, if applicable, the electrical lead (28) of said sensor by the transmitter coil (18), and wherein the component (ΔW) resulting from the transmitter coil (18) is taken into account in the registering of the temperature (T) of the measurement surface (38). [0050] 2. Method according to clause 1, characterized in that that the component (ΔW) is taken into account as a fixed value (ΔF), which is obtained by taking into account a given maximum operating time of the apparatus (10) and given environmental parameters. [0051] 3. Method according to clause 1, characterized in that the component (ΔW) of the warming is determined taking into account the registered temperature progression (A) of the sensed surface (38) after the operation of the transmitter coil (18) of the apparatus (10) is stopped. [0052] 4. Method according to clause 3, characterized in that the operation of the transmitter coil (18) is stopped periodically. [0053] 5. Method according to clause 3 or 4, characterized in that the component of the warming (ΔW) is determined on the basis of a mathematical function, taking into account known parameters of the temperature sensor (26), such as its heat storage capacity storage capacity, and, if applicable, environmental parameters. [0054] 6. Method according to clause 3 or 4, characterized in that the component of the warming (ΔW) is based on a comparison of the temperature progression (A) on the sensed surface (38) with stored curve progressions. [0055] 7. Method according to any one of clauses 1 to 6, characterized in that the apparatus (10) for inductively transferring energy is controlled on the basis of the determined temperature (T) and the transmitter coil (18) is periodically not operated to avoid the occurrence of excessively high temperatures (T), wherein the duration of the operating breaks of the transmitter coil (18) is based on the determined temperature (T) on the surface (38). [0056] 8. Apparatus (10) for inductively transferring energy, comprising a transmitter coil (18) disposed in a housing (20), wherein the housing (20) can be positioned at least in indirect contact with a to-be-measured surface(38), wherein the apparatus (10) is operated according to a method according to any one of Clauses 3 to 7, characterized in that a temperature sensor (26) is disposed in operative connection with the transmitter coil (18), and that the apparatus (10) comprises an algorithm for determining the component (ΔW) of a warming of the temperature sensor (26) and, if applicable, the lead (28) of said sensor caused by the fields emitted by the transmitter coil (18). [0057] 9. Apparatus according to clause 8, characterized in that the temperature sensor (26) is of an SMD design. [0058] 10. Use of the method according to any one of clauses 1 to 7 for determining the skin and/or tissue temperature of a human body (1) during an energy transfer in the human body (1), in particular in a VAD system (100).

List of Reference Signs

[0059] 1 Body [0060] 2 Human tissue [0061] 10 Apparatus [0062] 12 Transmitter unit [0063] 14 Receiver unit [0064] 16 Receiver coil [0065] 17 Coil winding [0066] 18 Transmitter coil [0067] 19 Coil axis [0068] 20 Housing [0069] 21 Transmitter coil carrier [0070] 22 Contact surface [0071] 23 Side [0072] 24 Field line [0073] 26 Temperature sensor [0074] 28 Electrical lead [0075] 30 Control device [0076] 32 Lead [0077] 34 Further lead [0078] 36 Further temperature sensor [0079] 38 Measurement surface [0080] 40 Decay curve [0081] 42 Section [0082] 100 Ventricular assist device (VAD) system [0083] A Curve progression [0084] A.sub.K Corrected curve progression [0085] T Temperature [0086] T.sub.Grenz Limit temperature [0087] T.sub.Korr Corrected temperature [0088] t Time [0089] V.sub.K Cooling rate [0090] ΔW Component [0091] ΔF Fixed value