Electric vehicle

Abstract

An electric vehicle has a control device that sets allowable power regarding power input and output to an electric storage device based on a temperature and an electric storage amount of the electric storage device, and controls an electric motor so that the power input and output to the electric storage device does not exceed the allowable power. The control device has an allowable maximum limit rate as a limit rate of a reduction speed of the allowable power. The control device is configured to reduce the allowable power at the allowable maximum limit rate in a case where an evaluation function F for a temperature of a component provided on a path of a current input and output to the electric storage device becomes a limit start value Ftag or more. The limit start value Ftag is set to a value at which the evaluation function F can be maintained at a threshold value Fm or less determined by a heat resistance limit temperature of the component in a case where the allowable power is reduced at the allowable maximum limit rate.

Description

Technical Field

[0001] This invention relates to an electric vehicle, and more specifically, to the charging and discharging control of an energy storage device mounted on an electric vehicle. Background Technology

[0002] Japanese Patent Application Publication No. 2015-147472 discloses a control device for a hybrid electric vehicle, which performs overheat protection control to suppress the rise in temperature of the electrical equipment, or to promote the decrease in temperature of the electrical equipment, when the temperature of the electrical equipment, including a drive motor and a cooling medium supplied for cooling it, exceeds a predetermined value. This overheat protection control includes controlling the reduction of the power generation load (regenerative torque) during deceleration regenerative braking and controlling the reduction of the torque assistance amount to the drive shaft. Summary of the Invention

[0003] In electric vehicles that operate on electricity stored in an energy storage device, it is necessary to suppress overheating of components located in the current path through which the current flows to and from the energy storage device. As a protective measure against component overheating, a method can be adopted that suppresses the overheating itself by limiting the current flowing through the component without increasing the heat resistance rating of the component.

[0004] However, in methods of limiting the current flowing to the aforementioned components, depending on the timing of the current limit or the magnitude of the current limit, the electric vehicle may be unable to ensure the desired output, thereby reducing the driving performance of the electric vehicle.

[0005] This invention was made to solve this problem, and its purpose is to control the charging and discharging of the energy storage device while properly protecting the components of the current path from the effects of heat, without impairing the driving performance of the electric vehicle.

[0006] The electric vehicle according to the present invention includes an electric motor that generates driving force for the electric vehicle, an energy storage device that inputs and outputs power to and from the electric motor, and a control device. The control device sets a permissible power for the input and output of power to and from the energy storage device based on the temperature and stored capacity of the energy storage device. The control device controls the electric motor to ensure that the power input and output to and from the energy storage device does not exceed the permissible power. The control device has a maximum permissible limiting rate for limiting the rate at which the permissible power is reduced. The control device is configured to reduce the permissible power at the maximum permissible limiting rate when an evaluation function for the temperature of a component disposed on a path, the path being the path through which current is input to and output from the energy storage device, is above a limit start value. The limit start value is set to a value that can maintain the evaluation function below a threshold determined by the heat resistance limit temperature of the component when reducing the permissible power at the maximum permissible limiting rate.

[0007] According to the above structure, by using the maximum allowable limit rate to limit the allowable power, it is possible to increase the limit start value and shorten the time for implementing the allowable power limit. This, in turn, can suppress component heating and prevent a decline in the driving performance of the electric vehicle.

[0008] The preferred limit start value is higher than the value that can maintain the evaluation function below the threshold when the allowable power is reduced proportionally to the deviation of the evaluation function from the limit start value. Therefore, compared to the structure where the allowable power is reduced proportionally to the deviation of the evaluation function from the limit start value, the higher limit start value and the longer time it takes for the limit rate to reach the maximum allowable limit rate, thus shortening the time required to enforce the allowable power limit.

[0009] The preferred control device, when the evaluation function reaches or exceeds the initial limit value, uses a pre-defined control mapping diagram to calculate the target value of the allowable power based on the evaluation function in each control cycle. Within a range not lower than the target value for the current control cycle, the control device reduces the target value from the previous control cycle at the maximum allowable limit rate, thereby determining the control command value of the allowable power for the current control cycle. Based on this structure, the allowable power can be rapidly reduced to the target value based on the evaluation function.

[0010] The preferred control mapping is one that can determine the target value based on the evaluation function. In the region where the evaluation function is above the limit start value and below the threshold, the target value varies non-linearly relative to the evaluation function, from a first power value determined by the temperature and power storage capacity of the energy storage device to a second power value that can maintain the evaluation function at the threshold. According to this structure, when the evaluation function is above the limit start value, the allowable power can be reduced using the maximum allowable limit rate.

[0011] Preferably, the control device has a maximum permissible easing rate for the easing rate, which is the easing speed of the permissible power. When the evaluation function is less than a limit start value, the control device calculates a target value for the current control cycle based on the temperature and capacity of the energy storage device. Within a range not exceeding the target value for the current control cycle, the control device increases the target value from the previous control cycle at the maximum permissible easing rate, thereby determining the control command value for the permissible power in the current control cycle. According to this structure, when the evaluation function is less than the limit start value according to the aforementioned permissible power limit, the permissible power can be rapidly increased to the permissible power determined by the temperature and capacity of the energy storage device.

[0012] According to the present invention, the charging and discharging of the energy storage device can be controlled while properly protecting the components of the current path from the effects of heat, without impairing the driving performance of the electric vehicle. Attached Figure Description

[0013] Hereinafter, with reference to the accompanying drawings, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described, in which the same reference numerals denote the same elements, and wherein:

[0014] Figure 1 This is a diagram illustrating an example of the overall structure of an electric vehicle according to this embodiment.

[0015] Figure 2 This is a diagram illustrating the summary of the power limitation processing allowed by the battery based on the comparative example.

[0016] Figure 3 It means Figure 2 The graph shows an example of how the output of the limiting process allows the limiting rate of power to vary over time.

[0017] Figure 4 This is a diagram illustrating a summary of the power limiting process for the battery output based on this embodiment.

[0018] Figure 5 It means Figure 4 The graph shows an example of how the output of the limiting process allows the limiting rate of power to vary over time.

[0019] Figure 6 This is a flowchart illustrating the sequence of processing for limiting the allowable power output of the battery based on this embodiment. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, identical or corresponding parts in the drawings will be labeled with the same symbols, and their descriptions will not be repeated.

[0021] The overall structure of electric vehicles

[0022] Figure 1 This diagram illustrates an example of the overall structure of the electric vehicle 1 according to this embodiment. In this embodiment, the electric vehicle 1 is, for example, a battery electric vehicle. The electric vehicle 1 can be a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.

[0023] Electric vehicle 1 is equipped with an electric generator (MG) 10, a power transmission gear 20, a drive wheel 30, a power control unit (PCU) 40, a system main relay (SMR) 50, a battery 80, a monitoring unit 90, and an electronic control unit (ECU) 100.

[0024] MG10 is an AC rotating motor, such as a three-phase AC synchronous motor with permanent magnets embedded in the rotor. MG10 is driven by receiving power from battery 80 via PCU40. The driving force of MG10 is transmitted to drive wheel 30 via power transmission gear 20, which includes a reducer and differential device.

[0025] When the electric vehicle 1 brakes or reduces acceleration while going downhill, the drive wheel 30 drives the MG10, which acts as a generator to regenerate electricity. The electricity generated by the MG10 is stored in the battery 80 via the PCU40.

[0026] PCU40 is a power conversion device that bidirectionally converts power between MG10 and battery 80. PCU40 includes, for example, an inverter and a converter that operate based on control signals from ECU100.

[0027] When battery 80 discharges, the converter boosts the DC voltage supplied from battery 80 and supplies it to the inverter. The inverter then converts the DC power supplied from the converter into AC power to drive MG10.

[0028] When the inverter charges the battery 80, it converts the AC power generated by MG10 into DC power and supplies it to the converter. The converter then steps down the DC voltage supplied by the inverter to a voltage suitable for charging the battery 80 and supplies it to the battery 80.

[0029] SMR50 is electrically connected to power line 45 connecting battery 80 and PCU40. When SMR50 is closed (ON) according to a control signal from ECU100, power can be transferred and received between battery 80 and PCU40. On the other hand, when SMR50 is opened (OFF) according to a control signal from ECU100, the electrical connection between battery 80 and PCU40 is disconnected.

[0030] Battery 80 stores the power used to drive MG10. Battery 80 is a rechargeable DC power source (secondary battery) and is configured as multiple individual cells 80a connected in series. Individual cells 80a are, for example, lithium-ion batteries.

[0031] The monitoring unit 90 is a device for monitoring the state of the battery 80, including a voltage sensor 92, a current sensor 94, and a temperature sensor 96. The voltage sensor 92 detects the voltage VB of the battery 80. The current sensor 94 detects the input and output current IB to the battery 80. The temperature sensor 96 detects the temperature TB of the battery 80. The monitoring unit 90 outputs the detection results from each sensor to the ECU 100.

[0032] The electric vehicle 1 includes a socket 60 configured to externally charge the battery 80 using a charging device (Electric Vehicle Supply Equipment: EVSE) 200. The socket 60 is configured to connect to a connector 220 located at the front end of a charging cable 210 provided at the EVSE 200. The socket 60 is electrically connected to a power line 45 via a charging circuit 70. In this embodiment, when the SMR 50 is closed, the socket 60 can be electrically connected to the battery 80 for external charging.

[0033] ECU 100 includes a Central Processing Unit (CPU) 102, Read-Only Memory (ROM) and Random Access Memory (RAM) 104, and input / output ports (not shown) for inputting and outputting various signals. ECU 100 executes controls related to vehicle operation and the charging and discharging of battery 80 based on signals received from various sensors in monitoring unit 90 and programs and mappings stored in memory 104.

[0034] Furthermore, as a protection measure against the heating of components located in the current path through which the current flows to and from the battery 80 is supplied, the ECU 100 limits the current flowing through the components based on the heating state of the components.

[0035] ECU100 corresponds to one embodiment of a "control device". ECU100 can be divided into multiple ECUs for each function. Alternatively, at least a portion of ECU100 can be constructed and processed using dedicated hardware (electronic circuitry).

[0036] Component protection measures

[0037] In the electric vehicle 1 according to this embodiment, a component in the current path through which current flows to and from the battery 80 generates heat in that component that is approximately proportional to the square of the current value. Therefore, protective measures are needed to prevent the component from overheating. The protective measures for the component in the electric vehicle according to this embodiment will be described below.

[0038] In this embodiment, as a protection measure for the component, an evaluation function representing the component's heating state is generated based on the current flowing through the component and the energizing time. Based on the output value of the evaluation function, the allowable power representing the upper limit of the power input and output to the battery 80 is limited. That is, the current flowing through the component is limited based on the component's heating state.

[0039] It is known that the heat generated by a component is proportional to the square of the current flowing through it, and that the heat dissipation from the component can be approximated by a first-order hysteresis system. If this function is expressed as an evaluation function F, it becomes, for example, equation (1).

[0040] F(n+1)={(K(n)-1}×F(n)+I(n)2} / K(n)…(1)

[0041] Here, n represents the number of control cycles since the start of control, i.e., the elapsed time. I(n) represents the current value flowing through the component at control cycle number n, and K(n) is a coefficient used for the first-order hysteresis approximation, i.e., a coefficient equivalent to the time constant. This coefficient K(n) has different values ​​for each component and is set using a mapping diagram or similar method pre-established through experiments. Furthermore, the coefficient K(n) can also have different values ​​depending on the current value.

[0042] By pre-setting the coefficient K of the evaluation function F for the component to be protected through experiments, the heating state of the component can be inferred based on the current flowing through the component and the energizing time. Then, by limiting the current to each component so that the output value of the evaluation function F does not exceed the threshold determined by the component's heat resistance limit, the heating of the component can be suppressed.

[0043] Issues regarding protective measures

[0044] Figure 2 and Figure 3 This diagram is used to illustrate the protective measures and problems of components based on comparative examples. Figure 2 This is a diagram illustrating the limited processing of the power Wout allowed by the output of battery 80 based on a comparative example. Figure 2 In the diagram, the horizontal axis shows the output value of the evaluation function F for components along the current path of battery 80, and the vertical axis shows the output allowable power Wout. The output allowable power Wout is the upper limit of the control for the power output from battery 80.

[0045] If power is initially applied to the component, its temperature gradually increases over time. Correspondingly, the output value of the component's evaluation function F also increases. A limiting start value Ftag is set for the output value of the evaluation function F to restrict the allowable power output Wout. Furthermore, a threshold Fm based on the component's thermal limit temperature is set for the output value of the evaluation function F.

[0046] When the output value of the evaluation function F is less than the limit start value Ftag, the output allowable power Wout is set to the output allowable power SWout based on the SOC and temperature of the battery 80.

[0047] When the output value of the evaluation function F becomes above the limit start value Ftag, the limit for the allowed power Wout is started to be output. Furthermore, "the limit for the allowed power Wout" refers to reducing its magnitude (equivalent to an absolute value). The same applies to the upper limit of the power input to battery 80, i.e., the limit for the allowed power Win.

[0048] like Figure 2 As shown, the output allowable power Wout decreases linearly (in the form of a linear function) relative to the output value of the evaluation function F. Furthermore, the output allowable power MWout when the output value of the evaluation function F is the threshold Fm is set based on the output power of the battery 80 at which the heat generation and dissipation in the component are balanced, and the component temperature rise is suppressed, thus maintaining it below the heat resistance limit temperature.

[0049] If the slope of the linear function of the evaluation function F and the output power Wout is set as Ko, then Swout, MWout, Ftag and Fm satisfy the relationship of equation (2).

[0050] MWout=SWout-Ko×(Fm-Ftag)…(2)

[0051] In the comparative example, based on Figure 2 The relationship between the output value of the evaluation function F and the allowable output power Wout is shown, and the allowable output power Wout is limited based on the output value of the evaluation function F. Regarding the allowable output power Wout when the output value of the evaluation function F is above the limit start value Ftag, it is calculated using the relationship Wout = SWout - Ko × (F - Ftag) according to equation (2). That is, the allowable output power Wout is calculated by performing a proportional control operation to reduce the deviation F - Ftag of the output value of the evaluation function F relative to the limit start value Ftag. Ko is equivalent to the proportional gain.

[0052] exist Figure 2 In this context, the initial limit value Ftag is set to a value that can maintain the output value of the evaluation function F below the threshold Fm when the output allowable power Wout is reduced proportionally to the deviation F-Ftag of the output value of the evaluation function F relative to the initial limit value Ftag.

[0053] Figure 3 It means Figure 2 The graph illustrates an example of how the limiting rate of output allowed power Wout changes over time in a limiting process. The "limiting rate of output allowed power Wout" refers to the rate of change of time (i.e., the rate of decrease) that causes the output allowed power Wout to decrease, denoted by dWout / dt [kW / sec]. The limiting rate is expressed as a negative value.

[0054] Furthermore, the rate at which the allowable power output Wout decreases is set to a maximum allowable rate. The "maximum allowable rate" refers to the maximum permissible magnitude (equivalent to an absolute value) of the rate at which the allowable power output Wout decreases. If the allowable power output Wout decreases drastically, the driving performance of the electric vehicle 1 may be reduced due to insufficient power output from the battery 80. Therefore, the maximum allowable rate is pre-set through experiments to prevent a decrease in the driving performance of the electric vehicle 1.

[0055] exist Figure 3 In the process, the output value of the evaluation function F between time t0 and time t1 is less than the limit start value Ftag. Therefore, no limit is imposed on the output allowed power Wout, and the limit rate is 0 [kW / sec].

[0056] If the output value of the evaluation function F exceeds the initial limit value Ftag at time t1, the limit on the allowable power Wout is started to be output. As described above, the allowable power Wout is calculated by a proportional control operation that reduces the deviation F-Ftag of the output value of the evaluation function F relative to the initial limit value Ftag. Immediately after time t1, the control quantity Ko×(F-Ftag) increases according to the deviation F-Ftag, and therefore the magnitude (absolute value) of the limit rate also increases. However, the limit rate is adjusted to not exceed the maximum allowable limit rate. Moreover, as the deviation F-Ftag decreases, the magnitude (absolute value) of the limit rate also gradually decreases.

[0057] Thus, in the comparative example, the allowable power output Wout is reduced proportionally to the deviation F-Ftag of the output value of the evaluation function F relative to the initial limit value Ftag. The output value of the evaluation function F decreases based on the square of the current flowing through the component, therefore the limit rate decreases based on the square of the current. Consequently, the maximum allowable limit rate cannot be fully utilized.

[0058] Furthermore, in order to limit the allowable power output Wout to a threshold Fm by ensuring that the output value of the evaluation function F does not exceed the threshold Fm at a rate lower than the maximum allowable limit rate, the initial limit value Ftag has to be set relatively low. Therefore, the required output of electric vehicle 1 cannot be met, raising concerns that this might reduce the driving performance of electric vehicle 1.

[0059] Protection measures according to this embodiment

[0060] To address the aforementioned issues, this embodiment proposes a protection measure that allows for more effective use of the maximum allowed rate limit. Figure 4 and Figure 5 This is a diagram used to illustrate the protection measures for the components based on this embodiment.

[0061] Figure 4This is a diagram illustrating a summary of the power Wout limitation processing allowed by the battery 80 based on this embodiment. Figure 4 In the diagram, the horizontal axis shows the output value of the evaluation function F for components along the current path of battery 80, and the vertical axis shows the output allowed power Wout. Figure 4 In the diagram, solid lines represent the waveform of the output allowable power Wout based on this embodiment, and dashed lines represent the waveform based on... Figure 2 The output of the comparative example shown allows for the waveform of the power Wout.

[0062] In this embodiment, similar to the comparative example, a limit start value Ftag for starting to output the allowed power Wout and a threshold Fm based on the component's heat resistance limit temperature are set for the output value of the evaluation function F. However, the limit start value Ftag in this embodiment is higher than the limit start value Ftag in the comparative example.

[0063] In this embodiment, the initial limit value Ftag is set to a value that, when the output allowable power Wout decreases at the maximum allowable limit rate, can maintain the output value of the evaluation function F below the threshold Fm. Therefore, unlike the comparative example, the output allowable power Wout decreases non-linearly relative to the output value of the evaluation function F.

[0064] Figure 5 It means Figure 4 The graph shown illustrates an example of how the output of the limiting process allows the limiting rate of power Wout to vary over time. Figure 3 Similarly, the rate limit is represented by a negative value. Figure 5 In the diagram, solid lines represent the limited rate based on this embodiment, and dashed lines represent the rate based on... Figure 3 The rate limit of the comparative example shown.

[0065] exist Figure 5 In the process, the output value of the evaluation function F between time t0 and time t1 is less than the limit start value Ftag. Therefore, no limit is imposed on the output allowed power Wout, and the limit rate is 0 [kW / sec].

[0066] If the output value of the evaluation function F exceeds the initial limit value Ftag at time t1, then the limit on the allowed power Wout is started to be output. The rate at which the allowed power Wout is output is set to the maximum allowed limit rate. That is, the allowed power Wout decreases at the maximum allowed limit rate after time t1.

[0067] The evaluation function F decreases by reducing the allowable power Wout by outputting a rate of decrease based on the square of the current flowing through the component. If the output value of the evaluation function F decreases to the limit start value Ftag at time t2, the limit rate is set to 0 [kW / sec].

[0068] from Figure 5 As can be seen, in this embodiment, compared to the comparative example, the initial limit value Ftag is higher, therefore the time when the limit on the allowed power Wout is output based on the increase in the output value of the evaluation function F (time t1 in the figure) is later. Furthermore, in this embodiment, compared to the comparative example, the time for the limit rate to reach the maximum allowed limit rate (the time from time t1 to t2 in the figure) is longer.

[0069] As a result, in this embodiment, the length of time during which the limiting rate is less than 0 [kW / sec], i.e. the length of time during which the limit on the output allowed power Wout is executed, is shorter than in the comparative example.

[0070] Thus, according to this embodiment, by limiting the output allowable power Wout by using the maximum allowable limiting rate, the limiting start value Ftag can be set higher than that of the comparison example, and the time for executing the limiting of the output allowable power Wout can be shortened. Therefore, it is possible to suppress component heating while meeting the required output of the electric vehicle 1. That is, it is possible to suppress the decline in the driving performance of the electric vehicle 1 caused by component protection measures.

[0071] Figure 6 This is a flowchart illustrating the sequence of limiting the output power Wout of the battery 80 based on this embodiment. It is executed by the ECU 100 according to each predetermined control cycle. Figure 6 The flowchart is shown below. Hereinafter, steps will be referred to simply as S.

[0072] like Figure 6 As shown, in S01, ECU100 obtains the detected values ​​of the voltage VB of battery 80, the detected values ​​of the current IB input and output to battery 80, and the detected values ​​of the temperature TB of battery 80 from the monitoring unit 90.

[0073] In S02, ECU100 calculates the output value of the evaluation function F of the component to be protected based on the input and output current IB of the battery 80 using Equation (1). In S02, the coefficient K(n) in Equation (1) is set using a mapping diagram or the like, which is set in advance by conducting experiments on each component.

[0074] In S03, ECU100 obtains the target value of the output allowed power Wout from the previous control cycle, namely the target power Wout*(n-1).

[0075] In S04, ECU100 compares the output value of the evaluation function F obtained in S02 with the limit start value Ftag.

[0076] If the output value of the evaluation function F is above the limit start value Ftag (when it is determined to be "yes" in S04), ECU100 calculates the target power Wout*(n) for the current control cycle based on the output value of the evaluation function F in S05. In S05, ECU100 has pre-set... Figure 4 The control mapping diagram shown represents the relationship between the output value of the evaluation function F and the allowable output power Wout. ECU100 uses this control mapping diagram to calculate the allowable output power Wout corresponding to the output value of the evaluation function F as the target power Wout*(n).

[0077] In S06, ECU100 calculates the control command value of the allowable output power Wout for the current control cycle, namely the command power Wout(n). In S06, ECU100 calculates the value of reducing the previous target power Wout*(n-1) by the maximum allowable limit rate. If the magnitude (absolute value) of the maximum allowable limit rate is set as dWout_res / dt, and the length of the control cycle is set as dt, then this value is represented by Wout*(n-1) - dWout_res. Then, ECU100 sets the larger of this value and the target power Wout*(n) for the current control cycle as the command power Wout(n).

[0078] That is, when the output value of the evaluation function F becomes above the limit start value Ftag, the ECU100 reduces the command power Wout in each control cycle at the maximum allowable limit rate within a range not lower than the target power Wout* in each control cycle.

[0079] On the other hand, if the output value of the evaluation function F is less than the limit start value Ftag (determined as "No" in S04), the ECU100 calculates the target power Wout*(n) for the current control cycle based on the SOC and temperature TB of the battery 80. In S07, the ECU100 calculates the SOC of the battery 80. The SOC calculation method uses known methods such as those utilizing the SOC-OCV (Open Circuit Voltage: OCV) curve, current accumulation-based methods, or combinations thereof. Then, the ECU100 calculates the allowable output power SWout as the target power Wout*(n) based on the SOC and temperature TB of the battery 80.

[0080] In S08, ECU100 calculates the commanded power Wout(n) for the current control cycle. In S08, ECU100 increases the commanded power Wout for each control cycle at the maximum permissible mitigation rate, within a range not exceeding the target power Wout* (=SWout) for each control cycle.

[0081] Specifically, a maximum allowable easing rate is set for the easing rate of the allowable output power Wout. The "easing rate of the allowable output power Wout" refers to the rate of change of time (i.e., the rate of increase) when the allowable output power Wout increases, denoted by dWout / dt [kW / sec]. The rate limit is expressed as a positive value. The "maximum allowable easing rate" refers to the maximum allowable magnitude (equivalent to the absolute value) of the rate of increase of the allowable output power Wout. In the event of a rapid increase in the allowable output power Wout, the drivability of the electric vehicle 1 may be reduced due to the abrupt change in the output power of the battery 80. Therefore, the maximum allowable easing rate is set in advance through experiments, etc., to avoid reducing the drivability of the electric vehicle 1.

[0082] In S08, ECU100 calculates the value of increasing the previous target power Wout*(n-1) according to the maximum allowable mitigation rate. If the magnitude (absolute value) of the maximum allowable mitigation rate is set as dWout_rel / dt, and the length of the control cycle is set as dt, then this value is represented by Wout*(n-1) + dWout_rel. ECU100 sets the smaller of this value and the target power Wout*(n) (=SWout) in the current control cycle as the command power Wout(n) in the current control cycle.

[0083] As explained above, in the limiting process of the allowable output power Wout of the battery 80, when the output value of the evaluation function F is above the limit start value Ftag, the ECU 100 reduces the allowable output power Wout at the maximum allowable limiting rate. Furthermore, when the output value of the evaluation function F is below the limit start value Ftag, the ECU 100 increases the allowable output power Wout at the maximum allowable mitigation rate. In this way, the time during which the power input and output to the battery 80 is limited is shortened, thus suppressing the decline in the driving performance of the electric vehicle 1 caused by component protection measures.

[0084] Furthermore, in the above embodiment, the limiting process for the output allowable power Wout of battery 80 has been described, but the same method applies to the limiting process for the input allowable power Win of battery 80.

[0085] It should be considered that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention is not shown in the description of the above embodiments, but is indicated by the technical solutions, and is intended to include all modifications within the meaning and scope equivalent to the technical solutions.

Claims

1. An electric vehicle, characterized in that, have: An electric motor that generates the driving force for the electric vehicle; An energy storage device that inputs and outputs power between itself and the electric motor; and A control device, based on the temperature and capacity of the energy storage device, sets an allowable power level for the input and output of power to the energy storage device, and controls the motor to ensure that the power input and output to the energy storage device does not exceed the allowable power level. The control device has a maximum allowable limit rate for the rate at which the allowable power is reduced. The control device is configured to reduce the allowable power at the maximum allowable limit rate when an evaluation function for the temperature of a component located along the path exceeds a limit start value. The path is a path for the input and output current of the energy storage device. The limit start value is set to a value that can maintain the evaluation function below a threshold determined by the heat resistance limit temperature of the component when the allowable power is reduced at the maximum allowable limit rate.

2. The electric vehicle according to claim 1, characterized in that, The starting limit value is higher than a value that can maintain the evaluation function below the threshold when the allowed power is reduced proportionally to the deviation of the evaluation function from the starting limit value.

3. The electric vehicle according to claim 1, characterized in that, When the evaluation function becomes above the limit start value, the control device performs the following processing: Using a pre-defined control mapping diagram, the target value of the allowable power based on the evaluation function is calculated in each control cycle. Within a range not lower than the target value in the current control cycle, the target value in the previous control cycle is reduced at the maximum allowable limit rate, thereby determining the control command value of the allowable power in the current control cycle.

4. The electric vehicle according to claim 3, characterized in that, The control mapping is a mapping that can determine the target value according to the evaluation function. In the region where the evaluation function is above the limit start value and below the threshold, the target value changes non-linearly relative to the evaluation function, from a first power value determined by the temperature and power storage capacity of the energy storage device to a second power value that can maintain the evaluation function at the threshold.

5. The electric vehicle according to claim 3 or 4, characterized in that, The control device has a maximum permissible mitigation rate for the mitigation rate, which is the mitigation speed of the permissible power. When the evaluation function is less than the starting limit value, the control device performs the following processing: Based on the temperature and capacity of the energy storage device, the target value for this control cycle is calculated. Within a range not exceeding the target value in the current control cycle, the target value in the previous control cycle is increased at the maximum permissible mitigation rate, thereby determining the control command value of the permissible power in the current control cycle.

Images