Electric vehicle control device

Abstract

To provide a control device of an electric vehicle capable of improving road holding of a vehicle, by using as much power as possible from a power supply for supplying power to a motor.SOLUTION: A control device of an electric vehicle including a motor as a driving-force source, a power supply for supplying power to the motor, and a cooling device for cooling the power supply includes a controller for controlling output of the motor. The controller is constituted so as to set an upper limit of the output of the power supply (step S4) when the cooling device fails (determined positively in step S1) based on a temperature difference between a present temperature of the power supply and an upper limit temperature determined beforehand, and remaining charge of the power supply.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control device for an electric vehicle equipped with a motor as a driving force source. [Background technology]

[0002] Patent Document 1 describes a control device for a forklift equipped with a motor as a driving force source. This control device is configured to increase the limit of the upper limit output of the motor in a stepwise manner as the temperature of the battery, which supplies power to the motor or charges the motor with power regenerated by the motor, increases when the temperature of the battery reaches or exceeds a first predetermined temperature. In other words, the motor output is reduced as the battery temperature increases. Furthermore, when the remaining charge of the battery is low, the first predetermined temperature is reduced and the upper limit temperature of the battery is reduced, taking into account the increase in temperature of the battery caused by charging the battery from an external power source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-165615 A Summary of the Invention [Problem to be solved by the invention]

[0004] The control device described in Patent Document 1 is configured to increase the limit of the motor output to make the driver feel the drop in driving force, so that the driver can recognize that the battery temperature is rising close to the upper limit temperature. Therefore, it is possible to prevent the motor output from suddenly dropping when the battery temperature reaches the upper limit temperature, causing the work to be interrupted. However, the control device described in Patent Document 1 is configured to increase the limit of the motor output when the battery has a low remaining charge, compared to when the battery has a high remaining charge. That is, even if the battery temperature is relatively low and a large amount of power can be output from the battery, the motor output is greatly limited. Therefore, the battery power cannot be fully used, and the vehicle's driving performance may be reduced.

[0005] The present invention has been made with attention to the above-mentioned technical problems, and has an object to provide a control device for an electric vehicle that can improve the driving performance of the vehicle by using as much of the power of the power source that supplies power to the motor as possible. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a control device for an electric vehicle including a motor as a driving force source, a power supply that supplies electric power to the motor, and a cooling device that cools the power supply. It is a place ,before The power supply a controller for controlling an output of the cooling device, The upper limit value of the output of the power source at which the remaining charge of the power source reaches a predetermined lower limit value at the time when the temperature of the power source reaches the upper limit temperature is set to the upper limit value. A temperature difference between the current temperature of the power source and a predetermined upper limit temperature and a remaining charge of the power source are used. Determined The present invention is characterized in that it is configured to Effect of the Invention

[0007] According to this invention, when the cooling device that cools the power source breaks down, the output of the power storage device can be restricted early and the temperature rise of the power storage device can be suppressed by determining the upper limit value of the output of the power source based on the temperature difference between the current temperature of the power source and a predetermined upper limit temperature and the remaining charge of the power source. That is, it is possible to prevent the temperature of the power storage device from reaching the upper limit temperature when the remaining charge of the power storage device is relatively high. As a result, the motor can continue to output torque by only slightly restricting the output torque of the motor. Therefore, it is possible to prevent the driving performance of the electric vehicle from being excessively deteriorated and to increase the driving distance.

[0008] Furthermore, by limiting the output of the power storage device early, it is possible to reduce the limit amount for preventing the temperature of the power storage device from rising to the upper limit temperature. In other words, it is possible to reduce the limit amount of the output torque of the motor. As a result, even after the output of the power storage device is limited, it is possible to prevent a deterioration in driving performance, such as a sudden decrease in the driving force of the electric vehicle. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an example of an electric vehicle according to an embodiment of the present invention; [Diagram 2] 4 is a flowchart illustrating an example of control of the control device according to the embodiment of the present invention. [Diagram 3] 3 is a time chart showing changes in the maximum value of the output of the power storage device, the motor torque, and the temperature of the power storage device when the control shown in FIG. 2 is executed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An electric vehicle according to an embodiment of the present invention includes a motor as a driving force source, and travels by transmitting the output torque of the motor (hereinafter, referred to as motor torque) to driving wheels. An example is shown in Fig. 1, and the vehicle Ve shown in Fig. 1 is an electric vehicle equipped with only a motor (MG) 1 as a driving force source. A differential gear unit 3 is connected to an output shaft 2 of the motor 1, and a pair of rear wheels 5 as driving wheels are connected via the differential gear unit 3 and a pair of drive shafts 4. The output shaft 2 of the motor 1 may be provided with a transmission for changing the operating point of the motor 1, a reducer for amplifying and transmitting the motor torque, or the like.

[0011] The motor 1 can be configured as an AC motor such as a permanent magnet synchronous motor or an induction motor, similar to motors provided as driving power sources in conventionally known hybrid vehicles and electric vehicles. In other words, the motor 1 is a motor generator that functions as an electric motor that outputs torque to increase the rotation speed of its output shaft 2, as well as a generator that outputs torque to reduce the rotation speed of the output shaft 2 and converts part of the power of the output shaft 2 into electric power.

[0012] An electricity storage device (Batt) 6 such as a secondary battery or a capacitor is electrically connected to the motor 1. The electricity storage device 6 corresponds to the "power source" in the embodiment of the present invention, and is configured to supply power to the motor 1 and also to be able to store the power generated by the motor 1. Various sensors are connected to the electricity storage device 6, such as a temperature sensor that detects its temperature, a voltmeter that detects its output voltage, and an SOC sensor that detects the remaining charge.

[0013] In addition, since the temperature of the power storage device 6 rises due to the internal resistance of the power storage device 6 and the like as a result of outputting electric power or charging, a cooling device 7 such as a fan is provided to prevent the temperature of the power storage device 6 from rising to a predetermined upper limit temperature. Note that the cooling device 7 is not limited to an air-cooled cooling device that cools the power storage device 6 by circulating air near the power storage device 6, but may be a water-cooled cooling device that cools the power storage device 6 by circulating a refrigerant near the case of the power storage device 6.

[0014] An electronic control unit (ECU) 8 is provided to control the above-mentioned power storage device 6 and cooling device 7. The ECU 8 corresponds to the "controller" in the embodiment of the present invention, and is mainly configured with a microcomputer. The ECU 8 receives signals from sensors that detect the operation amount (accelerator opening) of an accelerator pedal (not shown), vehicle speed, the number of revolutions of the motor 1, the temperature of the power storage device 6, the output voltage of the power storage device 6, the remaining charge (SOC) of the power storage device 6, and the like, and is configured to output command signals to the power storage device 6 and cooling device 7 based on the input signals and pre-stored arithmetic expressions, maps, and the like.

[0015] Specifically, the ECU 8 determines a required driving force and a required braking force based on the input accelerator opening degree, brake operation amount, and vehicle speed, and outputs a torque corresponding to the determined required driving force and required braking force as a command signal to the power storage device 6. As described above, the motor 1 is configured as an AC motor such as a synchronous motor or an induction motor, whereas the power storage device 6 is configured to output a DC current, and therefore includes an inverter or converter (not shown) for converting the DC current output from the power storage device 6 into an AC current, and the output of the power storage device 6 is controlled by controlling a signal input to a switch element of the inverter or converter.

[0016] In addition, the ECU 8 constantly receives a signal from a sensor that detects the temperature of the power storage device 6, and when the temperature of the power storage device 6 rises above a predetermined temperature, the ECU 8 outputs a signal to drive the cooling device 7 in order to cool the power storage device 6, and is configured to control the control amount for driving the cooling device 7 according to the temperature of the power storage device 6.

[0017] On the other hand, if the cooling device 7 breaks down, it is not possible to control the temperature of the electricity storage device 6 to a desired temperature or lower, and so the temperature of the electricity storage device 6 gradually rises as the motor 1 is driven. In particular, the greater the output (power) of the motor 1, the higher the rate of rise in the temperature of the electricity storage device 6.

[0018] Therefore, the control device in the embodiment of the present invention is configured to limit the output of the motor 1 when the cooling device 7 breaks down. FIG. 2 is a flow chart for explaining an example of this control, and first, it is determined whether or not the cooling device 7 has broken down (step S1). This step S1 can be determined, for example, based on whether or not the rate of increase in temperature of the power storage device 6 is higher than when the cooling device 7 is operating normally. Note that whether or not the cooling device 7 has broken down may be determined by detecting a current value between the cooling device 7 and a power source (not shown) for operating the cooling device 7, and the means for determining whether or not the cooling device 7 has broken down is not particularly limited.

[0019] If the cooling device 7 is not broken and therefore the determination in step S1 is negative, this routine is terminated. On the other hand, if the cooling device 7 is broken and therefore the determination in step S1 is positive, then it is determined whether the temperature of the power storage device 6 is below a first predetermined temperature T1 (step S2). This first predetermined temperature T1 is a threshold temperature determined to limit the maximum output value of the power storage device 6 regardless of the presence or absence of a failure of the cooling device 7. Therefore, if the temperature of the power storage device 6 is equal to or higher than the first predetermined temperature T1, the maximum output value of the power storage device 6 is limited in the same manner as in the conventionally known control. This control example limits the maximum output value of the power storage device 6 when the power storage device 6 is below the first predetermined temperature T1, so in the flowchart shown in FIG. 2, if the determination in step S2 is negative, this routine is terminated.

[0020] Conversely, if the temperature of the power storage device 6 is lower than the first predetermined temperature T1 and therefore the answer to step S2 is YES, a look-ahead value for the temperature of the power storage device 6 is calculated (step S3). This step S3 calculates the temperature of the power storage device 6 at the time when the remaining charge of the power storage device 6 will drop to a predetermined lower limit if the power storage device 6 continues to output its maximum output value at the current time. Specifically, this can be calculated using the following formula.

number

[0021] In addition, in equation (1), Tend is the temperature (°C) of the storage device 6 when the remaining charge of the storage device 6 reaches a lower limit, Tbatt is the current temperature (°C) of the storage device 6, Tair is the endothermic temperature (°C) at which heat is dissipated to the air or the like without operating the cooling device 7, P is the maximum output value (W) of the storage device 6, Vave is the average output voltage (V) of the storage device 6, Rbatt is the internal resistance value (Ω) of the storage device 6, Kbatt is the cooling coefficient (W / K) of the case that houses the storage device 6, Mbatt is the heat capacity (J / K) of the storage device 6, Cbatt is the total capacity (discharge capacity (Ah)) of the storage device 6, and SOC is the depth of charge (remaining charge (%)) of the storage device 6.

[0022] Following step S3, the maximum output value of the power storage device 6 is suppressed (corrected) so that the remaining charge of the power storage device 6 is depleted when the read-ahead value reaches the upper limit temperature of the power storage device 6 (step S4), and this routine is temporarily terminated. Specifically, the upper limit temperature of the power storage device 6 is substituted for the temperature Tend of the power storage device 6 when the remaining charge of the power storage device 6 reaches the lower limit in the above formula, and the maximum output value P of the power storage device 6 that satisfies this condition is calculated.

[0023] Fig. 3 shows an example of changes in the maximum output value of the power storage device 6, the motor torque, and the temperature of the power storage device 6 when the control example shown in Fig. 2 is executed. In the example shown in Fig. 3, at time t0, the cooling device 7 is not broken down, so the maximum output value of the power storage device 6 is maintained at a predetermined value. Therefore, at time t0, the maximum torque of the motor 1 is maintained based on the maximum output value of the power storage device 6. The temperature of the power storage device 6 increases gradually as the torque is output from the motor 1.

[0024] At time t1, it is determined that the cooling device 7 has failed, and thus the maximum value of the output of the power storage device 6 is set based on the temperature of the power storage device 6 and the remaining charge of the power storage device 6. Therefore, at time t1, the maximum value of the output of the power storage device 6 drops in a stepwise manner. Accordingly, the maximum torque of the motor 1 drops in a stepwise manner. Therefore, the command torque of the motor 1 is limited in accordance with the drop in the maximum torque, and drops at time t1. The temperature of the power storage device 6 is maintained approximately constant by limiting the output of the power storage device 6 as described above.

[0025] After time t1, the maximum value of the output of the power storage device 6 is maintained substantially constant, thereby maintaining the maximum torque of the motor 1 at a predetermined torque. As a result, the amount of heat dissipated from the power storage device 6 to the air and the amount of heat generated by the power storage device 6 can be maintained in a substantially balanced state, so that the temperature of the power storage device 6 is maintained substantially constant.

[0026] As described above, by determining the maximum value of the output of the power storage device 6 based on the temperature of the power storage device 6 and the remaining charge of the power storage device 6 after the cooling device 7 breaks down, the output of the power storage device 6 can be limited early, and the temperature rise of the power storage device 6 can be suppressed. In other words, it is possible to prevent the temperature of the power storage device 6 from reaching the upper limit temperature when the remaining charge of the power storage device 6 is relatively high. As a result, it is possible to continuously output torque from the motor 1 by only slightly restricting the motor torque. Therefore, it is possible to prevent the driving performance of the electric vehicle Ve from being excessively deteriorated and to increase the driving distance.

[0027] Furthermore, by limiting the output of the power storage device 6 at an early stage, it is possible to reduce the amount of limitation for preventing the temperature of the power storage device 6 from rising to the upper limit temperature. In other words, it is possible to reduce the amount of limitation on the motor torque. As a result, even after the output of the power storage device 6 is limited, it is possible to prevent a deterioration in the running performance of the electric vehicle Ve, such as a sudden decrease in the driving force.

[0028] The electric vehicle in the embodiment of the present invention is not limited to an electric vehicle having only a motor as a driving force source as described above, but may be a hybrid vehicle having an engine and a motor as driving force sources. In the case of such a hybrid vehicle, the vehicle can run using the power of the motor within the range of the output limit of the power storage device, and as a result, deterioration of fuel efficiency due to excessive driving of the engine, etc. can be suppressed. In addition, the electric vehicle is not limited to an electric vehicle having one motor as a driving force source as described above, but may be, for example, a so-called in-wheel motor vehicle having a motor in each wheel. [Explanation of symbols]

[0029] 1 Motor 2 Output shaft 3 Differential gear unit 4 Drive shaft 5 Rear wheel 6. Energy storage device 7 Cooling device 8 Electronic Control Unit (ECU) Ve Electric Vehicle

Claims

[Claim 1] A control device for an electric vehicle including a motor as a driving force source, a power source that supplies power to the motor, and a cooling device that cools the power source, A controller for controlling an output of the power supply, The controller: When the cooling device breaks down, the upper limit of the output of the power source at which the remaining charge of the power source reaches a predetermined lower limit at the time when the temperature of the power source reaches the upper limit temperature is determined based on the temperature difference between the current temperature of the power source and the predetermined upper limit temperature and the remaining charge of the power source. A control device for an electric vehicle.

Images