Resistor unit comprising a fluid-cooled electrical resistor element and method for estimating a temperature of the fluid-cooled electrical resistor element

Abstract

The present invention relates to a resistor unit (1, 1', 1''), comprising: at least one electrical resistor (10), at least one fluid-carrying cooling unit (30) on and / or in which at least part of the at least one electrical resistor (10) is arranged, at least one detection unit (3, 4, 5, 6, 7, 71, 72) and at least one evaluation device (40) that can be operatively connected to the at least one detection unit (3, 4, 5, 6, 7, 71, 72), the at least one detection unit (3, 4, 5, 6, 7, 71, 72) being configured to measure a variable that represents the temperature (TR) of the at least one electrical resistor (10) per se or in combination with a further detection unit (3, 4, 5, 6, 7, 71, 72) and that relates to an electrical property of the at least one electrical resistor (10) and / or to a property of a fluid flowing through the fluid-carrying cooling unit (30). The present invention additionally relates to a brake system and to a vehicle having such a resistor unit and to a method for estimating a temperature of the fluid-cooled electrical resistor.

Description

[0001] DESCRIPTION

[0002] Resistance unit with a fluid-cooled electrical resistance element and method for estimating the temperature of the fluid-cooled electrical resistance element

[0003] The present invention relates to a resistance unit with a fluid-cooled electrical resistance element, a braking system, a vehicle with such a resistance unit, and a method for estimating the temperature of the fluid-cooled electrical resistance element.

[0004] Electrical resistors are used in vehicles, particularly electric and hybrid vehicles, to convert excess energy into heat. These resistors can be at least partially located in and / or on a fluid-filled cooling unit to transfer the generated heat to the fluid. This increases energy conversion capacity and allows the generated heat to be used elsewhere, for example, in a heating circuit. Despite the cooling, the electrical resistor can still experience thermal overload, or an excessively high temperature may indicate another type of fault.Accordingly, direct temperature measurement is performed using a thermistor or other temperature sensor, which is mounted on the electrical resistance element or on a substrate for the electrical resistance element for connection to the cooling device. Direct measurement therefore requires a separate temperature sensor and is subject to, among other things, structural restrictions regarding accessibility, installation space, and connection requirements to an evaluation device.

[0005] The object of the present invention is to provide a temperature monitoring system for a fluid-cooled electrical resistance element, thereby offering an alternative to direct temperature measurement at the electrical resistance element itself. This object is achieved by the dependent claims. Advantageous embodiments are the subject of the dependent claims.

[0006] According to the invention, a resistance unit comprises at least one electrical resistance element, at least one fluid-flowing cooling unit, and / or in which the at least one electrical resistance element is at least partially arranged, at least one detection unit and at least one evaluation device, which is operatively connectable to the at least one detection unit or which has at least one detection unit. The at least one detection unit is configured to detect at least one electrical property of the at least one electrical resistance element and / or at least one property of a fluid flowing through the fluid-flowing cooling unit and to transmit it to the evaluation device.The evaluation device is configured to determine a quantity representing the temperature of the at least one electrical resistance element from the at least one electrical property of the at least one electrical resistance element and / or at least one property of a fluid flowing through the fluid-through cooling unit.

[0007] The above configuration of the resistance unit can thus be used to replace direct temperature measurement with indirect temperature determination or estimation by detecting properties that, individually or in combination, represent a temperature of the electrical resistance element, or to supplement it for reasons of plausibility, redundancy, and / or other factors. For this purpose, the resistance unit comprises at least one electrical property of the at least one electrical resistance element and / or at least one property of a fluid flowing through the fluid-cooling unit. Preferably, the properties are detected using existing detection units, so that additional detection units, as required for direct temperature measurement, can be dispensed with.

[0008] An active sensor can serve as the detection unit, capturing at least one property and transmitting it to the evaluation device. Alternatively, a signal input can also act as the detection unit, allowing the resistor unit to acquire measurement signals, status data, and / or control signals. Status data, for example, relates to a state in which at least one property is expected to have a predetermined value. Control signals, in this context, are signals that, for instance, create changing conditions within a state, for which a predetermined value for at least one property is also expected.The status and / or control signals can each be forwarded to the evaluation device as a signal representing the status or the control command, whereby the evaluation device can then derive the corresponding representative quantity from a database and / or using an algorithm.

[0009] The operational connectivity of the evaluation device to the at least one detection unit refers to the aforementioned signal connection, which can be established directly or indirectly via intermediate components such as a signal converter, amplifier, or the like. Connectivity itself also includes the possibility of making the connection switchable, i.e., of selectively establishing and / or disconnecting the connection.

[0010] The at least one electrical resistance element is arranged as a fluid-cooled electrical resistance element, at least partially in or on a fluid-flowing cooling unit. The arrangement can be at least partially direct in or on the fluid-flowing cooling unit, but it can also be provided, at least partially, via a support between the electrical resistance element and the fluid-flowing cooling unit. The support or support material serves, for example, to improve the connection of the electrical resistance element to the fluid-flowing cooling unit.Provided that the determination of the representative quantity by the evaluation device takes into account at least one property of the fluid flowing through the fluid-cooled unit, as described below, the heat transfer properties of the medium must also be considered in the arrangement between the electrical resistance element and the fluid-cooled unit. The fluid flowing through the fluid-cooled unit can be a gas or a liquid.

[0011] In one embodiment, at least one electrical resistance element is an electrical braking resistor of a vehicle.

[0012] In electric vehicles or hybrid vehicles, at least one electrical brake resistor can be assigned to a regenerative brake, i.e., a drive motor or electric motor in recuperation mode, in order to convert excess braking energy, which cannot be used in other ways such as charging a battery, into heat and dissipate it during conventional operation.

[0013] In one embodiment, the resistance unit comprises at least one current detection unit and / or at least one voltage detection unit as detection units. The at least one evaluation device is configured to calculate the electrical resistance, representing the temperature of the at least one electrical resistance element, from the signal of the current detected by the at least one current detection unit and / or the signal of the voltage detected by the at least one voltage detection unit, and to estimate the temperature of the at least one electrical resistance element from this calculation.

[0014] The electrical resistance, as the quantity representing the temperature of at least one electrical resistance element, can be determined from the voltage applied to the at least one electrical resistance element and the current flowing through it. Preferably, both the voltage and the current are detected by separate detection units or a common detection unit and forwarded to the evaluation device for calculating the electrical resistance. Alternatively, the calculation by the evaluation device can be based on a constant current or a constant voltage, so that only the voltage or the current needs to be measured.In one embodiment, the at least one evaluation device is configured to estimate the temperature of the at least one electrical resistance element at a time t as a function of the electrical resistance R(t) = U(t) / I(t), in particular via Tn(t) = a * (R(t)) with TR as the temperature of the electrical resistance and a as the proportionality factor, particularly preferably via the equation R(TR(12)) = R(TR(H )) * (1 + ß * (TR(t2)- T. R (t1 )) with ß as the proportionality factor.

[0015] Accordingly, the evaluation unit estimates the temperature of the electrical resistance element based on its electrical resistance at any given time, the voltage applied to the element, and the current. This estimation can be performed proportionally to the electrical resistance or, alternatively, by comparing values ​​to a stored database.

[0016] To determine the temperature TR(12) of the electrical resistance element at time t2 as a temperature TR(12) of the electrical resistance element after time t1, the equation R(TR(12)) = R(TR(H )) * (1 + β * (TR(t2)- T) can preferably be used. R(t1 )). To determine this, an initial condition can be set for time t1, for which the temperature TR(H ) of the electrical resistance element is known. The temperature TR(FI ) of the electrical resistance element thus represents a reference temperature under known conditions. For example, room temperature, such as 20°C, can be used as the reference temperature, at which the electrical resistance is known or measured. The subsequent temperatures of the electrical resistance element can then be estimated back to t1 or more generally using the equation R(T (tn+1 )) = R(T (tn)) * (1 + β * (T (tn+1 )- T (tn)) with n as the index for the reference time.

[0017] In one embodiment, the resistance unit comprises at least one temperature input detection unit, which detects the input temperature of the fluid flowing into the fluid-through cooling unit, and at least one temperature output detection unit, which detects the output temperature of the fluid flowing out of the fluid-through cooling unit. The at least one evaluation device is configured to calculate the temperature change of the fluid, representing the temperature of the at least one electrical resistance element, from the signal of the input temperature of the fluid detected by the at least one temperature input detection unit and / or the signal of the output temperature of the fluid detected by the at least one temperature output detection unit, and to estimate the temperature of the at least one electrical resistance element from this.

[0018] The alternative or supplementary estimation of the temperature of the electrical resistance element thus considers the temperature difference between the inlet and outlet temperatures as the representative quantity. This temperature difference is a measure of the heat transfer from the at least one electrical resistance element to the fluid in the cooling unit. As the positive value of the temperature difference increases, a corresponding increase in the temperature of the at least one electrical resistance element can be assumed. Accordingly, the current temperature of the at least one electrical resistance element can be estimated from the positive value of this temperature relative to a reference temperature.Assuming that the inlet temperature of the fluid flowing through the fluid-cooling unit is constant, only the outlet temperature of the fluid flowing through the fluid-cooling unit can be compared to the temperature of at least one electrical resistance element for estimation purposes.

[0019] Other factors that can be taken into account when estimating the temperatures of the fluid flowing through the fluid-cooling unit, in order to make the estimation more precise, are factors influencing the heat transfer from the at least one electrical resistance element to the fluid, such as the thermal resistance and / or heat losses.

[0020] In one embodiment, the at least one evaluation device is configured to estimate the temperature of the at least one electrical resistance element at a time t as a function of the temperature change of the fluid, in particular via T R (t) = Y * (T aus (t) - Tein(t)) with Y as the proportionality factor, particularly preferably via Pthermisch = ö * cp * (Taus(t) - Tein(t)) with Pthermisch as thermal power, ö as mass flow-dependent proportionality factor, and cp as specific heat capacity of the fluid, and Pthermisch = (TR - Ttiuid) / Rth, where Rth is the thermal resistance depending on the conductive and convective heat coefficients with respect to the thermal resistance. Ttiuid can represent the average fluid temperature of Tein(t) and Taus(t) or Tein(t).

[0021] With regard to thermal performance, the temperature of at least one electrical resistance element can be estimated as follows:

[0022] T R (t) = (ö * cp * (T out (t) - Tein (t)) * Rth) + Ttiuid(t)

[0023] In one embodiment, the resistance unit comprises at least one mass flow detection unit that measures the mass flow rate of the fluid flowing through the fluid-cooled unit, and / or at least one evaluation device that has a mass flow signal input for receiving a signal representing the mass flow rate of the fluid. The at least one evaluation device is configured to calculate the quantity representing the temperature of the at least one electrical resistance element from the temperature change of the fluid as a function of the mass flow rate of the fluid.

[0024] According to the preceding description for estimating the temperature of at least one electrical resistance element based on the inlet and outlet temperatures of the fluid flowing through the fluid-cooled unit, a constant mass flow rate of the fluid is assumed. If this is not the case, or if the mass flow rate of the fluid exhibits fluctuations exceeding a predetermined amount, the estimation of the temperature of the at least one electrical resistance element can be further refined by appropriately considering the mass flow rate. In other words, with an increased mass flow rate and a constant temperature difference, a comparatively higher temperature of the at least one electrical resistance element would be expected compared to a reduced mass flow rate with the same temperature difference.

[0025] In one embodiment, the at least one evaluation device is configured to estimate the temperature of the at least one electrical resistance element at a time t as a function of the temperature change and the mass flow rate of the fluid, in particular via Tn(t) = £ * dm / dt * (Taus(t) - Tein(t)) with £ as the proportionality factor, particularly preferably via Pthermisch = dm / dt * c P * (T from — Tein) and Pthermic = (TR - Tfiuid) / Rth, where Rth is the thermal resistance and depends on the conductive and convective heat coefficients.

[0026] With regard to thermal performance, the temperature of at least one electrical resistance element can be estimated as follows:

[0027] TR(1) = (dm / dt * Cp * (Taus(t) - Tein(t)) * Rth) + Tfluid(t)

[0028] In one embodiment, the resistance unit comprises at least one input pressure detection unit, which detects the input pressure of the fluid flowing into the fluid-through cooling unit, and / or at least one output pressure detection unit, which detects the output pressure of the fluid flowing out of the fluid-through cooling unit, as mass flow detection units. The at least one evaluation device is configured to calculate the mass flow rate of the fluid from the signal of the input pressure of the fluid detected by the at least one input pressure detection unit and / or the signal of the output pressure of the fluid detected by the at least one output pressure detection unit.

[0029] The mass flow rate therefore does not need to be measured directly, but can be derived from the inlet and outlet pressures of the fluid, or from the difference between these two pressures. This is particularly advantageous, for example, when the mass flow rate of the fluid varies locally, meaning that measuring the mass flow rate at one location is not representative of the overall change in mass flow rate. Regardless of whether the mass flow rate is constant, deriving it from the pressure difference can also be advantageous if suitable detection units are already available, as their signals can then be easily used to estimate the temperature of at least one electrical resistance element.

[0030] In one embodiment, the at least one evaluation device is configured to calculate the mass flow rate at a time t as a function of the inlet pressure and the outlet pressure of the fluid, in particular via dm / dt = * (pein(t) - Paus(t)) with as the proportionality factor, especially preferably via dm / dt = v(t) * A s * p and p e in(t)-paus(t) = (A * L * p * v(t) 2 ) / (dh * 2) with v(t) as fluid velocity, A s as flow cross-section, p as fluid density, A as pipe friction factor, L as length of flow and dh as hydraulic diameter.

[0031] The mass flow rate is thus derived as proportional to the pressure difference between the inlet pressure and the outlet pressure of the fluid in order to estimate the temperature of at least one electrical resistance element.

[0032] Preferably, the mass flow rate can then be expressed as dm / dt = v(t) * A s* p can be calculated, whereby the fluid velocity v(t) does not need to be recorded, but can be calculated using the equation p e in(t)-p a us(t) = (A * L * p * v(t) 2 ) / (dh * 2) can be expressed according to the pressure difference. In other words, from rearranging the equation, one obtains and thus In one embodiment, the resistance unit has at least one control device which is operationally connected to the at least one electrical resistance element via at least one electrical line and / or a signal line and includes at least one evaluation device which includes at least one detection unit and / or at least one switching device to disconnect or close the connection via the electrical line and / or another electrical connection of the at least one electrical resistance element.

[0033] The control device can, for example, be designed as a brake chopper. A brake chopper, as used here, is understood to be a device that includes at least one switching device capable of connecting and disconnecting an electric motor, particularly an electric motor for powering an electric or hybrid vehicle, via the electrical conductor to at least one electrical resistance element. When connected, energy from the electric motor can be conducted through the at least one electrical resistance element to convert excess energy into heat. Accordingly, the control device can actuate the switching device to connect or disconnect the connection as needed when energy dissipation is required. For this purpose, the switching device can be located within the electrical conductor.

[0034] Alternatively or additionally, the control device can also be connected to the at least one electrical resistance element via a signal line in order to, for example, tap a voltage and / or current signal via at least one detection unit.

[0035] Alternatively or additionally, the control device can also be configured to increase the cooling capacity of the fluid-cooled cooling unit in order to reduce the temperature of the at least one electrical resistance element to a tolerable level. In one embodiment, the control device includes at least one switching device and is configured to disconnect the connection via the electrical conductor and / or another electrical connection of the at least one electrical resistance element when the temperature of the at least one electrical resistance element reaches or exceeds a predetermined limit.Alternatively or additionally, the control device is configured to establish the connection via the electrical line and / or the other electrical connection of the at least one electrical resistance element when the temperature of the at least one electrical resistance element falls below the predetermined limit, particularly in the presence of a signal representing a need to dissipate excess energy.

[0036] For example, the control device is configured to actuate the switching device such that, in the event of a need for energy dissipation, as described above using the electric motor as an example, the connection via electrical conductor or other electrical connection to the at least one resistive element is closed. If the energy dissipation occurs via a temperature increase of the at least one resistive element, it can overheat. The estimated temperature of the at least one resistive element can be used by the control device as overheat protection. If the temperature of the at least one resistive element exceeds the predetermined limit, the connection is broken.This form of temperature monitoring can also be used to estimate the amount of energy dissipation according to the temperature reached by at least one electrical resistance element and, based on this, to stop further energy dissipation by disconnecting the connection.

[0037] Establishing the connection via the electrical conductor and / or the other electrical connection of the at least one electrical resistance element when the temperature of the at least one electrical resistance element falls below the predetermined limit value can, for example, be provided again in relation to a previous disconnection according to an overheating protection if, accordingly, no critical temperature is present, but an energy dissipation requirement still exists or exists again.

[0038] According to a further aspect, the present invention relates to a braking system for a vehicle with at least one regenerative braking unit and at least one resistance unit described above, wherein the at least one regenerative braking unit can be operationally connected to the at least one resistance unit.

[0039] As already described in the section on the resistance unit, it can be particularly advantageous for use in regenerative braking systems. While the energy generated by regenerative braking systems is typically used to charge a vehicle battery or power other vehicle components, the resistance unit acts as an energy sink for excess energy. This is the case, for example, when the battery is already fully charged or charged to a predetermined level, and / or no other electrical component is available to draw energy. Due to potentially fluctuating energy levels, which are converted into heat via the at least one electrical resistor, there is a risk of overheating, especially with increased energy dissipation. However, this risk can be adequately monitored by the resistance unit.

[0040] The features described in the description of the resistance unit are equally applicable to the braking system. Likewise, features described for the braking system are transferable to the resistance unit, provided they have not already been described for the resistance unit.

[0041] According to a further aspect, the present invention relates to a vehicle with at least one resistance unit described above, wherein at least one electronic consumer of the vehicle, an electrical energy source of the vehicle for the at least one electronic consumer and / or an electrical connection via which the at least one energy source and the at least one electronic consumer can be connected, with which the at least one resistance unit can be operationally connected, and / or with at least one braking system described above.

[0042] The vehicle in question is, in particular, an electric vehicle or a hybrid vehicle.

[0043] The features described in the description of the resistance unit and brake unit are equally applicable to the vehicle. Likewise, features described for the vehicle relating to the resistance unit and / or brake system are transferable to the resistance unit and / or brake system, provided they have not already been described for the resistance unit and / or brake system.

[0044] According to a further aspect, the present invention relates to a method for estimating the temperature of at least one fluid-cooled electrical resistor of a resistor unit described above, comprising the steps:

[0045] Determine at least one quantity representing the temperature of the at least one electrical resistance element, which relates to an electrical property of the at least one electrical resistance element and / or a property of a fluid flowing through a fluid-based cooling unit, and

[0046] Estimating the temperature of at least one fluid-cooled electrical resistance element based on at least one specific representing quantity.

[0047] As already described for the resistance unit, this method involves temperature estimation based on determining a quantity representing the temperature of at least one electrical resistance element, thus eliminating the need for direct temperature measurement of the electrical resistance element itself. The features described for the resistance unit are equally applicable to this method. Likewise, features described for the resistance unit method are transferable to the resistance unit, provided they have not already been described for the resistance unit.

[0048] Exemplary embodiments of the present invention are described below with the aid of the accompanying drawing.

[0049] In detail, they show

[0050] Fig. 1 shows a schematic representation of an exemplary embodiment of a fluid-cooled electrical resistance element to which the present invention is applicable;

[0051] Fig. 2 shows a schematic representation of a resistance unit according to a first exemplary embodiment;

[0052] Fig. 3 shows a schematic representation of a resistance unit according to a second exemplary embodiment; and

[0053] Fig. 4 shows a schematic representation of a resistance unit according to a third exemplary embodiment.

[0054] Fig. 1 shows a schematic representation of an exemplary embodiment of a fluid-cooled electrical resistance element 10 to which the present invention is applicable. The electrical resistance element 10 is arranged on a fluid-flowing cooling unit 30 via an intermediate support 20.

[0055] A fluid is supplied to the fluid-flowing cooling unit 30 via a fluid inlet line 31 and discharged again via a fluid outlet line 32. The electrical resistance 20 is, in this case, an exemplary electrical braking resistor to which energy from a regenerative braking unit 80 (Fig. 2) can be supplied via the electrical line 11 in order to be converted into heat via the electrical resistance 10. The heat is dissipated by convection, but in particular by conduction via the support to the fluid flowing through the fluid-flowing cooling unit 20.

[0056] For the sake of clarity, in the following figures the electrical resistance element 10, the support 20 and the cooling unit 20 are no longer shown individually, but are combined as a resistance assembly 50.

[0057] Fig. 2 shows a schematic representation of a resistance unit 1 according to a first exemplary embodiment. The resistance unit 1 can be connected to a regenerative braking unit 80 via an electrical line 11. Specifically, the electrical resistance element 10 of the resistance unit 1 can be connected to the regenerative braking unit 80. The resistance unit 1 also includes a control device 2, which is exemplary here designed as a brake chopper and is arranged between the electrical resistance element 10 and the regenerative braking unit 80, through which the electrical line 11 passes. In alternative embodiments, the resistance unit 1 or the electrical resistance element 10 can also be connected alternatively or additionally to an energy storage unit, such as a battery.Descriptions relating to the connection with the regenerative braking unit 80 can therefore be applied analogously to a connection with an energy storage unit. The energy storage unit can, for example, be charged with electrical energy directly via the regenerative braking unit 80 or via the electrical resistance element 10. Furthermore, the electrical resistance element 10 can also be connected to the energy storage unit in order to selectively discharge energy, at least partially, via the electrical resistance element 10.

[0058] The control device 2 has a switching device 8 in the electrical line 11 to establish and disconnect the connection between the electrical resistance element 10 and the regenerative braking unit 80. The control device 2 also includes a current detection unit 3 and a voltage detection unit 4, each connected to the electrical line 11, to detect a current or voltage flowing through the electrical line and thus through the electrical resistance element 10. The current signals from the current detection unit 3, corresponding to a detected current l(t), and the voltage signals from the voltage detection unit 4, corresponding to a detected voltage U(t), are transmitted to an evaluation device 40 of the control device 2.

[0059] The evaluation device 40 determines the electrical resistance R(t) as a quantity representing the temperature of the electrical resistance element 10, as R(t) = U(t) / I(t). Furthermore, the evaluation device 40 estimates the temperature of the electrical resistance element 10 using the equation R(TR(12)) = R(Tn(t1 )) * (1 + β * (TR(12)- T R (t1 )) with ß as the proportionality factor.

[0060] If the evaluation device 40 estimates a temperature of the electrical resistance element 10 that reaches or exceeds a predetermined limit value, the control device 2 controls the switching device 8 in such a way that the connection between the electrical resistance 10 and the regenerative braking unit 40 is disconnected, thus preventing overheating of the electrical resistance 10.

[0061] Fig. 3 shows a schematic representation of a resistance unit 1 according to a second exemplary embodiment. The second embodiment differs from the first embodiment in that, instead of using an electrical property to estimate the temperature of the electrical resistance element 10, the properties of the fluid are considered. Therefore, Fig. 3 shows a representation limited to essential components compared to Fig. 2, due to an otherwise identical structure. Accordingly, identical components also bear the same reference numerals.

[0062] Instead of the electrical resistance R(t) according to the first embodiment, in the second embodiment the estimation of the temperature of the electrical resistance element 10 is based on a temperature difference of the fluid flowing through the fluid-flowing cooling unit 20 and a mass flow rate of the fluid as quantities representing the temperature of the electrical resistance element 10. Accordingly, a mass flow detection unit 7 and an input temperature detection unit 5 are arranged in the fluid inlet line 31. An output temperature detection unit 6 is arranged in the fluid outlet line 32. The signals from the detection units 5, 6, and 7 are transmitted to the evaluation device 40 via corresponding signal lines. The mass flow detection unit 7 can alternatively be arranged in the fluid outlet line 32.

[0063] The evaluation device estimates the temperature of at least one electrical resistance element at a time t as a function of the temperature change and the mass flow rate of the fluid. This estimation is performed using Tn(t) = Σ * dm / dt * (Taus(t) - Tein(t)) with Σ as the proportionality factor, taking into account Pthermisch = dm / dt * Cp * (Taus — Tein) And Pthermic = (TR - Tfluid) / Rth, where Rth is the thermal resistance and depends on the conductive and convective heat coefficients. According to the estimation of the temperature of the electrical resistance element 10 via

[0064] TR(1) = (dm / dt * cp * (Taus(t) - Tein(t)) * Rth) + Tfluid(t) corresponds to the proportionality factor £ here cp * Rth, where the temperature Tpiuid is also taken into account.

[0065] Fig. 4 shows a schematic representation of a resistance unit 1 according to a third exemplary embodiment. The third embodiment differs from the second embodiment in that the mass flow rate is not detected via the mass flow detection unit 7, but is derived from the pressure difference between an inlet pressure of the fluid flowing through the fluid-cooling unit 20 and an outlet pressure of the fluid. Otherwise, the description given for Fig. 2 applies. Accordingly, identical components also bear the same reference numerals. In contrast to the second embodiment, the fluid inlet line 31 has, in addition to the inlet temperature detection unit 5, an inlet pressure detection unit 71 for detecting an inlet pressure p instead of a mass flow detection unit 7. ein(t) of the fluid. The fluid outlet line 31, in addition to the outlet temperature detection unit 6, has an outlet pressure detection unit 71 for detecting an outlet pressure p. aus (t) of the fluid. The signals from the detection units 5, 6, 71, 72 are forwarded to the evaluation device 40 via corresponding signal lines.

[0066] The evaluation device then determines the mass flow rate dm / dt as dm / dt = v(t) * A s * p taking further account of the equation p e in(t)-p a us(t) = (A * L * p * v(t) 2 ) / (dh * 2). In other words, the transformation of the equation yields and thus

[0067] The estimation of the temperature of the electrical resistance element 10 by the evaluation unit 40 is then carried out analogously to the procedure described for the second embodiment with the mass flow rate dm / dt determined according to the above equation.

[0068] The invention is not limited to the described embodiment. In particular, features described in relation to this embodiment, other described embodiments, and further developments of the invention can be combined with one another, provided they are not reasonably mutually exclusive, and are accordingly also disclosed as independent individual features for further combination. Furthermore, the estimation of the temperature of the electrical resistance element 10 can alternatively or additionally be carried out using a characteristic map stored in the evaluation device 40, in addition to a calculation described by the embodiments.

[0069] REFERENCE MARK LIST

[0070] 1, r, 1 resistance unit

[0071] 2 Chopper (switching device?)

[0072] 3 Current detection unit

[0073] 4 voltage detection unit

[0074] 5 Input temperature detection unit

[0075] 6 Output temperature detection unit

[0076] 7 Mass flow detection unit

[0077] 8 Switching device

[0078] 10 electrical resistance element

[0079] 11 electrical line

[0080] 20 carriers

[0081] 30 cooling units

[0082] 31 Fluid inlet line

[0083] 32 Fluid outlet line

[0084] 40 Evaluation device

[0085] 50 resistor assembly

[0086] 71 Inlet pressure detection unit

[0087] 72 Output pressure detection unit

[0088] 80 regenerative braking unit dm / dt mass flow

[0089] I current

[0090] Paus output pressure (fluid)

[0091] Pain Inlet Pressure (Fluid)

[0092] R electrical resistance

[0093] U voltage t time

[0094] TR Temperature (electrical resistance element)

[0095] Tein inlet temperature (fluid)

[0096] Dew's initial temperature (fluid)

Claims

PATENT CLAIMS 1. Resistance unit (1, 1', 1"), comprising: at least one electrical resistance element (10), at least one fluid-flowed cooling unit (30) on and / or in which the at least one electrical resistance element (10) is at least partially arranged, at least one detection unit (3, 4, 5, 6, 7, 71, 72) and at least one evaluation device (40) which is operatively connectable to the at least one detection unit (3, 4, 5, 6, 7, 71, 72) or which comprises at least one detection unit (3, 4, 5, 6, 7, 71, 72), wherein the at least one detection unit (3, 4, 5, 6, 7, 71, 72) is configured to detect at least one electrical property of the at least one electrical resistance element (10) and / or at least one property of the fluid-flowed cooling unit (30). to detect the fluid flowing through the cooling unit (30) and transmit it to the evaluation device (40), and the evaluation device (40) is configured to do so,to determine a quantity representing the temperature (TR) of the at least one electrical resistance element (10) from the at least one electrical property of the at least one electrical resistance element (10) and / or at least one property of a fluid flowing through the fluid-through cooling unit (30).

2. Resistance unit (1 , 1 ', 1 ") according to claim 1 , wherein the at least one electrical resistance element (10) is an electrical braking resistor of a vehicle.

3. Resistance unit (1) according to one of claims 1 or 2, wherein the resistance unit comprises at least one current detection unit (3) and / or at least one voltage detection unit (4) as detection units, and the at least one evaluation device (40) is configured to derive the electrical resistance (R) as the temperature (TR) from the signal of the current (I) detected by the at least one current detection unit (3) and / or the signal of the voltage (U) detected by the at least one voltage detection unit (4). to calculate the quantity representing at least one electrical resistance element (10) and to estimate the temperature (TR) of the at least one electrical resistance element (10) from it.

4. Resistance unit (1) according to claim 3, wherein the at least one evaluation device (40) is configured to estimate the temperature (TR) of the at least one electrical resistance element (10) at a time t as a function of the electrical resistance R(t) = U(t) / I(t), in particular via Tn(t) = a * (R(t)) with a as the proportionality factor, particularly preferably via the equation R(TR(12)) = R(TR(t1 )) * (1 + ß * (TR(t2)- Tn(t1)) with ß as the proportionality factor.

5. Resistance unit (1 ', 1 ") according to one of the preceding claims, wherein the resistance unit (1 ', 1 ") comprises at least one temperature input detection unit (5) that detects an input temperature of the fluid flowing into the fluid-through cooling unit (30), and at least one temperature output detection unit (6) that detects an output temperature of the fluid flowing out of the fluid-through cooling unit (30), and which is configured to include at least one evaluation device (40)to calculate the temperature change of the fluid as the quantity representing the temperature of the at least one electrical resistance element (10) from the signal of the input temperature of the fluid detected by the at least one temperature input detection unit (5) and / or the signal of the output temperature of the fluid detected by the at least one temperature output detection unit (6), and to estimate the temperature of the at least one electrical resistance element (10) from this.

6. Resistance unit (1 ', 1 ") according to claim 5, wherein the at least one evaluation device (40) is configured to estimate the temperature of the at least one electrical resistance element (10) at a time t as a function of the temperature change of the fluid, in particular via Tn(t) = y * (Taus(t) - Tein(t)) with Y as the proportionality factor, particularly preferably via Pthermisch = ö * c p* (Taus(t) - Tein(t)) with Pthermisch as thermal power, ö as proportionality factor and c P as the specific heat capacity of the fluid and Pthermic = (TR - Ttiuid) / Rth, where Rth is the thermal resistance depending on the conductive and convective heat coefficients.

7. Resistance unit (1 1 ") according to claim 5, wherein the resistance unit (1 ) comprises at least one mass flow detection unit (7, 71 , 72) which has a mass flow rate (dm / dt) of the fluid flowing through the fluid-through cooling unit (30) and / or the at least one evaluation device (40) which has a mass flow rate signal input for receiving a signal representing the mass flow rate (dm / dt) of the fluid, and the at least one evaluation device (40) which is configured to calculate the quantity representing the temperature of the at least one electrical resistance element (10) from the temperature change of the fluid as a function of the mass flow rate (dm / dt) of the fluid.

8. Resistance unit (1 ', 1 ") according to claim 7, wherein the at least one evaluation device (40) is configured to estimate the temperature of the at least one electrical resistance element (10) at a time t as a function of the temperature change and the mass flow rate (dm / dt) of the fluid, in particular via Tn(t) = £ * dm / dt * (Taus(t) - Tein(t)) with £ as the proportionality factor, particularly preferably via Pthermic = dm / dt * Cp * (Taus - Tein) and Pthermic = (TR - Ttiuid) / Rth, where Rth is the thermal resistance and depends on the conductive and convective heat coefficients.

9. Resistance unit (1) according to claim 7 or 8, wherein the resistance unit (1) comprises at least one input pressure detection unit (71) that detects an input pressure (pein) of the fluid flowing into the fluid-through cooling unit (30), and / or at least one output pressure detection unit (72) that detects an output pressure (p aus) of the fluid flowing out of the fluid-through cooling unit (30), has mass flow detection units, and the at least one evaluation device (40) is configured to derive from the signal of the input pressure (pein) of the fluid detected by the at least one input pressure detection unit (71) and / or the signal of the fluid detected by the at least one The outlet pressure detection unit (72) is used to calculate the mass flow rate (dm / dt) of the fluid from the detected outlet pressure (paus) of the fluid.

10. Resistance unit (1") according to claim 9, wherein the at least one evaluation device (40) is configured to calculate the mass flow rate (dm / dt) at a time t as a function of the inlet pressure (pein) and the outlet pressure (paus) of the fluid, in particular via dm / dt = * (pein(t) - paus(t)) with as proportionality factor, particularly preferably via dm / dt = v(t) * A s * p and p e in(t)-p a us(t) = (A * L * p * v(t)2 ) / (dh * 2) with v(t) as fluid velocity, A s as flow cross-section, p as fluid density, A as pipe friction factor, L as length of flow and dh as hydraulic diameter.

11. Resistance unit (1 , 1 ', 1 ") according to one of the preceding claims, wherein the resistance unit (1 , 1 ', 1 ") comprises at least one control device (2) which is operationally connected to the at least one electrical resistance element (10) via at least one electrical line (1 1 ) and / or a signal line and comprises at least one evaluation device (40) which includes at least one detection unit (3, 4, 5, 6, 7, 71 , 72) and / or at least one switching device (8) to open or close the connection via the electrical line (1 1 ) and / or another electrical connection of the at least one electrical resistance element (10).

12. Resistance unit (1 , 1 ', 1 ") according to claim 1 1 , wherein the control device (2) comprises at least one switching device (8) and is configured to disconnect the connection via the electrical line (1 1 ) and / or any other electrical connection of the at least one electrical resistance element (10) when the temperature (TR) of the at least one electrical resistance element (10) reaches or exceeds a predetermined limit value and / or to establish the connection via the electrical line (1 1 ) and / or the other electrical connection of the at least one electrical resistance element (10) when the temperature (TR) of the at least one electrical resistance element (10) falls below the predetermined limit, particularly in the presence of a signal representing a need to dissipate excess energy.

13. Braking system for a vehicle comprising at least one regenerative braking unit and at least one resistance unit (1 , 1 ', 1 ") according to one of the preceding claims, wherein the at least one regenerative braking unit is operationally connectable to the at least one resistance unit (1 , 1 ', 1 ").

14. Vehicle with at least one resistance unit (1 , 1 ', 1 ") according to any one of claims 1 to 12, wherein at least one electronic consumer of the vehicle, an electrical energy source of the vehicle for the at least one electronic consumer and / or an electrical connection via which the at least one energy source and the at least one electronic consumer can be connected, with which at least one resistance unit (1 , 1 ', 1 ") can be operationally connected, and / or with at least one braking system according to claim 13.

15. Method for estimating a temperature (TR) of at least one fluid-cooled electrical resistance element (10) of a resistance unit (1 , 1 ', 1 ") according to any one of claims 1 to 12, comprising the steps: Determine at least one quantity representing the temperature (TR) of the at least one electrical resistance element (10), which relates to an electrical property of the at least one electrical resistance element (10) and / or a property of a fluid flowing through a fluid-through cooling unit (30), and Estimating the temperature (TR) of at least one fluid-cooled electrical resistance element (10) based on at least one specific representing quantity.

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