ELECTRIC DRIVE SYSTEM OF A MOTOR VEHICLE AND METHOD FOR CONTROLLING THE TEMPERATURE OF DRIVE SYSTEM COMPONENTS OF SUCH AN ELECTRIC DRIVE SYSTEM

Abstract

An electric drive system of a motor vehicle and method for controlling the temperature of components of such an electric drive system, of a motor vehicle which has at least an electrical energy storage system, at least one power electronics unit, and at least one electrical machine for driving at least one drive wheel of the motor vehicle. The electrical energy storage system, the power electronics and the electrical machine each constitute a drive system component of the drive system and are functionally coupled with each other. At least two of the drive system components are part of an optimization module, which is designed to perform a performance-optimized relative temperature control of the drive system components. The invention also relates to a method of controlling the temperature of drive system components of such an electric drive system.

Claims

1. An electric drive system of a motor vehicle comprising: at least one electric energy storage system; at least one power electronics; and at least one electrical machine to drive at least one drive wheel of the motor vehicle, wherein the electrical energy storage system, the power electronics and the electrical machine each constitute a drive system component of the drive system and are functionally coupled with each other, and wherein at least two of the drive system components are part of an optimization module, which is designed to perform a performance-optimized relative temperature control of the drive system components.

2. The electric drive system according to claim 1, wherein the optimization module has at least two temperature detection units and at least one switching unit coupled to a temperature control device in order to operate the switching unit as needed depending on the actual temperature values recorded by the temperature detection units.

3. The electric drive system according to claim 1, wherein at least for each type of drive system component there is a separately controllable temperature control device that is restricted or restrictable to this drive system component.

4. The electric drive system according to claim 1, wherein at least two drive system components are functionally coupled with a common temperature control device.

5. The electric drive system according to claim 1, wherein at least one bypass is provided for a drive system component, which, via a switching device, is adapted to be brought into an open or closed configuration as needed.

6. The electric drive system according to claim 1, wherein at least one active cooler and/or at least one active heater is provided.

7. The electric drive system according to claim 1, wherein at least one additional tempering medium is provided.

8. A method for controlling a temperature of at least two drive system components comprising an electrical energy storage system, power electronics, and an electrical machine for driving at least one drive wheel of the motor vehicle, which are part of an optimization module of an electric drive system of a motor vehicle, the method comprising: determining a current performance of the drive system components in dependence on a current component temperature; comparing the currently deliverable power of the at least two drive system components in order to determine which drive system component delivers the lowest power; and controlling the temperature of the drive system component that was determined in the comparison step, and continuous or discontinuous repeating the step of determining.

9. The method according to claim 8, wherein, instead of the step of comparing or before the step of comparing, it is checked whether a drive system component or several drive system components are able to currently only deliver power below a specified temperature-dependent limit value and if this is true, all the drive system components are temperature-controlled.

10. The method according to claim 8, wherein, in the optimization module there is a map with operating points and associated control commands in order to initiate a relative temperature control of the drive system components triggered by predetermined control commands in dependence on determined operating points of the drive system component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0025] FIG. 1 shows a circuit diagram of an electric drive system according to the invention with three series-connected drive power components,

[0026] FIG. 2 is an example of a less preferred relative temperature control of the drive system components of the electric drive system shown in FIG. 1, and

[0027] FIG. 3 is an example of a preferred relative temperature control of the drive system components of the electric drive system shown in FIG. 1, in accordance with the method according to the invention.

DETAILED DESCRIPTION

[0028] FIG. 1 shows a circuit diagram of an electric drive system 10 according to the invention. The electric drive system 10 comprises, as drive system components 12, an electrical energy storage system 14, a power electronics 16 and an electrical machine 18. The drive system components 12 are connected in series in the example shown, i.e., arranged serially. This means that all drive system components 12 are connected in series and are part of a common tempering medium circuit 20. The tempering medium circuit 20 is permeated by a tempering medium, in particular a coolant. The tempering medium is conveyed and driven by a tempering medium pump 22. The tempering medium pump 22 can be, in particular, an electric coolant pump.

[0029] In the example shown, an energy storage thermostat 24 is arranged in front of the electrical energy storage system 14, a power electronics thermostat 26 in front of the power electronics 16 and a machine thermostat 28 in front of the electrical machine 18. With the help of the respective thermostat 24, 26, 28, the tempering medium can be adjusted, fully or partially, as required, by means of an energy storage bypass 30, a power electronics bypass 32 or a machine bypass 34, which bypasses the respective element and thusdepending on the switching position of the thermostat 24, 26, 28in the case of full flow, does not supply nor extract any temperature at all to or from the respective element and, in the case of partial flow, only partially extracts or supplies temperature. Temperature is supplied to the respective element when the tempering medium has a higher temperature than the respective element. Temperature is extracted when the tempering medium has a lower temperature than the respective element. In this case, the tempering medium is a coolant.

[0030] Downstream of the electrical machine 18, another temperature control device thermostat 36 is connected upstream of a temperature control device 38. For this temperature control device 38, a temperature control device bypass 40 is also provided. This temperature control device 38 can be a cooler and/or a heater. These can also be two or more separate temperature control devices 38 at different points in the tempering medium circuit 20.

[0031] The temperature control device bypass 40 is only flowed through when the temperature control device 38 is not required; in particular if the flow resistance through the temperature control device 38 is greater than that through the temperature control device bypass 40, then the flow resistance is reduced or the flow velocity is increased.

[0032] Upstream in front of the electrical energy storage system 14, which in the present case is a high-voltage battery of an electrically powered motor vehicle, an optional heat exchanger 42 is provided for air conditioning. For this heat exchanger 42, too, optionally a heat exchanger bypass can be provided.

[0033] Due to the fact that in the example shown a separate bypass 30, 32, 34 is provided for each of the drive system components 12, an increase in temperature or a reduction in temperature, i.e., a relative temperature control, can be carried out in a targeted manner only on a selected drive system component 12 or on two selected drive system components 12 by fully opening the bypass of the drive system component 12 not to be tempered and fully closing the duct section through this drive system component 12.

[0034] In particular, the energy storage thermostat 24, the power electronics thermostat 26 and the machine thermostat 28 are preferably electrically controlled thermostats. To determine a performance-optimized control of these thermostats 24, 26, 28, e.g., by means of thermostat maps, in particular simulation calculations, measurement series on component test benches and/or measurement series in prototype vehicles are performed.

[0035] In particular, this can be methodically implemented as follows: [0036] (a) Establishment of a cooling circuit with the option of optimizing the temperature control in the system [0037] b) Transfer of the designed cooling circuit to a simulation environment [0038] c) Determination of ideal thermostat maps by means of test series: [0039] i. x.sub.EM . . . Thermostat setting EM (0% . . . 100%), x.sub.LE . . . Thermostat setting LE (0% . . . 100%), x.sub.EE . . . Thermostat setting of electrical energy storage systems, in particular HV battery (0% . . . 100%) [0040] ii. Thermostat settings are dependent on ambient temperature and component temperature (x=f(T.sub.umg, T.sub.EM, T.sub.LE, T.sub.EE)) [0041] iii. Optimization of the thermostat setting, e.g., PSO, so that, taking into account the known boundary conditions (max. thermostat settings, optimal temperature ranges, min./max. component temperatures, etc.), the maximum possible system performance is available: [0042] .Math.x.sub.opt=f(T.sub.umg, T.sub.EM, T.sub.LE, T.sub.EE), so that P.sub.system(T.sub.EM, T.sub.LE, T.sub.EE) is at a maximum [0043] d) Transfer of the determined characteristic maps to the control unit, taking into account application boundary conditions [0044] e) Testing/validation of maps from simulation to component test bench [0045] f) If necessary, adaptation of the maps, taking into account boundary conditions not known in simulation or not described in sufficient detail [0046] g) Application of the determined maps to the control unit for the prototype vehicle [0047] (h) Testing/validation of the maps by means of a series of tests in the real vehicle [0048] i) If necessary, adaptation of the characteristic maps, taking into account real boundary conditions

[0049] In particular, the tempering medium circuit shown in FIG. 1 can be used to perform the relative temperature controls visualized in FIG. 2. and FIG. 3, wherein FIG. 2 shows a relative temperature control primarily directed at the electrical machine 18, whereas FIG. 3 refers to the implementation of the method according to the invention.

[0050] In both FIG. 2 and FIG. 3, in each case the entire operating range B of each drive system component 12 as well as preferred temperature ranges BB and an optimal temperature range B.sub.O are shown. These are related to the drive system components 12identical in both examplesand therefore congruent for the respective drive system components 12.

[0051] FIGS. 2 and 3 show the temperatures T of the electrical energy storage system (EE) 14, the power electronics (LE) 16 and the electrical machine (EM) 18, each marked on the side as T(14), T(16) and T(18).

[0052] The examples in FIGS. 2 and 3 differ in the way in which the relative temperature control was carried out.

[0053] In the example shown in FIG. 2, the focus was on the fact that the electrical machine (EM) 18 is in its optimum temperature range B.sub.O as quickly as possible. Such a result occurs, for example, if no bypasses 30, 32, 34 are provided or they are not used. As a result, the electrical machine (EM) 18 can output a peak power of 100 KW due to temperature, while the electrical energy storage system (EE) 14 can only deliver a peak power of 75 KW and the power electronics (LE) 16 can deliver an output of 90 KW. This results in a maximum peak power of the system of 75 KW, which is limited by the currently lowest peak power of the electrical energy storage system (RE) 14.

[0054] In the example shown in FIG. 3, the relative temperature control was performed with optimized performance as per the invention. It is true that it was taken into account that the electrical machine (EM) 18 takes on a temperature that can only be found in the preferred temperature range above the optimal temperature range. However, the power electronics (LE) 16 were brought into their optimum temperature range and the electrical energy storage system (EE) 14 into a preferred temperature range, resulting in a peak power of 85 KW for the electrical energy storage system (RE) 14 and a peak power of 95 KW for the power electronics (LE) 16. This results in a maximum peak power of the system of 85 KW, which is limited by the currently lowest peak power of the electrical energy storage system (RE) 14 but is 10 KW higher than in the example shown in FIG. 2. The currently available system performance is therefore higher in the example visualized in FIG. 3 than in the one shown in FIG. 2.

[0055] The result shown in FIG. 3 can be achieved or, alternatively, accelerated, by initial activation of all bypasses 30, 32, 34, by providing an active heater which can bring the drive system components 12 into a preferred temperature range T.sub.B or into the optimal temperature range T.sub.O as quickly as possible.

[0056] The features of the invention disclosed in the present description, in the drawings and in the claims may be essential either individually or in any combination for the realization of the invention in its various embodiments. The invention can be varied within the framework of the claims and taking into account the knowledge of the competent professional.

[0057] In particular, it is pointed out that the invention is not limited to the tempering medium circuit 20 with serial switching of the drive system components 12. It is also possible to operate two or more tempering medium circuits 20 and/or to connect the drive system components 12 in parallel by using other temperature control systems in order to realize an electric drive system 10 according to the invention and/or to carry out the method according to the invention.

[0058] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.