Electric vehicle

Abstract

To provide an electric vehicle capable of avoiding deterioration of driving performance while a temperature of a power storage device is effectively risen.SOLUTION: A BEV 1 comprises a battery 10, inverters 25, 55, motors 27, 57, a switch 40, and an ECU 70. The motors 27, 57 respectively generate a first driving force and a second driving force. The switch 40 is provided in an electric path for connecting the inverter 55 to power lines PL1, PL2. When the switch 40 is in a closed state, the ECU 70 controls the inverters 25, 55 according to a required driving force of the BEV 1 so as to generate the first driving force and the second driving force. When a temperature rise start condition for starting the temperature rise of the battery 10 is satisfied in a case where the switch 40 is in the closed state, the ECU 70 switches the switch 40 from the closed state to an open state and controls the inverter 25 according to the required driving force so that the first driving force increases in accordance with the second driving force before switching of the switch 40.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an electric vehicle.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2022-155349 (Patent Document 1) discloses an electric vehicle. This electric vehicle includes a power storage device, an inverter, a motor, and a control device. The motor is driven by the inverter to generate a driving force for the electric vehicle to travel. When there is a temperature increase requirement for the power storage device, the control device controls the inverter so that the frequency of the current ripple generated in the electric circuit including the power storage device approaches the resonance frequency of the electric circuit. As a result, the current ripple input to and output from the power storage device increases, and the amount of heat generated due to the internal resistance of the power storage device increases. Consequently, the temperature of the power storage device rises.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An electric vehicle including a plurality of sets of the above-described inverter and motor is known. For example, a four-wheel drive electric vehicle in which the front wheels and the rear wheels are driven by separate inverters and motors is known. In this case, the front wheels are driven by a first inverter and a first motor, and the rear wheels are driven by a second inverter and a second motor connected in parallel to the first inverter with respect to the power storage device.

[0005] In the electric vehicle as described above, in addition to the electrical resonance component between the power storage device and the first inverter, a resonance component between the first inverter and the second inverter may exist. As a result, when the temperature rise of the power storage device is required, the resonance component between the power storage device and the first inverter is affected by the resonance component between the first and second inverters, and the current ripple input to the power storage device is reduced, and there is a possibility that the power storage device may not be effectively heated. Further, since the frequency of the current ripple described above depends on the control state and the rotational speed of the motor by the inverter, if the control state of the motor or the like is changed in order to bring the frequency of the current ripple closer to the resonance frequency inherent to the electric circuit, the driving force required for the electric vehicle cannot be ensured, and the running performance of the electric vehicle may deteriorate.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to avoid a decrease in the running performance of an electric vehicle while effectively heating a power storage device.

Means for Solving the Problems

[0007] The electric vehicle of the present disclosure includes a power storage device, a first inverter, a first rotating electric machine, a second inverter, a second rotating electric machine, a switch, and a control device. The first inverter is connected to the power storage device through a pair of power lines. The first rotating electric machine is driven by the first inverter and generates a first driving force. The second inverter is configured to be connectable to the pair of power lines and is provided electrically in parallel with the first inverter with respect to the power storage device. The second rotating electric machine is configured to be drivable by the second inverter and can generate a second driving force. The switch is provided in a circuit that connects the second inverter to the pair of power lines. When the switch is in the closed state, the control device controls the first inverter and the second inverter according to the required driving force of the electric vehicle so that the first driving force and the second driving force are generated. When the switch is in the closed state and a temperature rise start condition for starting the temperature rise of the power storage device is satisfied, the control device switches the switch from the closed state to the open state, and controls the first inverter according to the required driving force so that the first driving force increases according to the second driving force before the switch is switched.

Effect of the Invention

[0008] According to the present disclosure, it is possible to effectively raise the temperature of the power storage device while avoiding a decrease in the running performance of the electric vehicle.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0010] FIG. 1 is an overall configuration diagram of an electric vehicle according to the present embodiment. This vehicle is a battery electric vehicle (BEV) and can switch the running state between two-wheel drive and four-wheel drive. Referring to FIG. 1, the BEV 1 includes a battery 10, a sensor unit 15, an SMR 17, power lines PL1, NL1, PLa, NLa, PL2, NL2, drive devices 20, 50, a switch 40, and an ECU 70.

[0011] The battery 10 is a secondary battery such as a lithium-ion battery and corresponds to an example of the "power storage device" of the present disclosure. The internal resistance and reactance component of the battery 10 are also represented as "internal resistance Rb" and "reactance component Lb". The sensor unit 15 detects the current Ib, voltage Vb, and temperature Tb of the battery 10. When the temperature Tb decreases, the current Ib may decrease and the performance of the battery 10 may deteriorate. Therefore, it is necessary to appropriately raise the temperature of the battery 10 when the battery 10 is at a low temperature. In the embodiment, the temperature rise start condition for starting the temperature rise of the battery 10 is that the temperature Tb is lower than a predetermined threshold temperature. The SMR 17 is connected to the battery 10. The power lines PL1, NL1 are connected to the SMR 17.

[0012] The drive device 20 includes a capacitor C1, an inverter 25, current sensors 26u, 26v, and 26w, and a motor 27.

[0013] The capacitor C1 is connected between the power lines PL1 and NL1. The inverter 25 is connected to the battery 10 through the power lines PL1 and NL1 when the SMR17 is turned on. The inverter 25 receives the current Ib from the battery 10 and converts the current Ib into an alternating current. The alternating current is the U-phase current (current Iu), V-phase current, or W-phase current of the motor 27.

[0014] The current sensors 26u, 26v, and 26w detect the U-phase current, V-phase current, and W-phase current, respectively. These currents are also collectively referred to as "motor currents". The frequency of the motor current is also referred to as the "motor current frequency".

[0015] The motor 27 is a permanent magnet synchronous motor connected to the inverter 25 and generates a driving force for traveling. The motor 27 receives the alternating current from the inverter 25 and is driven by the inverter 25. The driving force generated by the motor 27 is also represented as the "first driving force".

[0016] A current ripple (ripple of the current Ib) is superimposed on the power lines PL1 and NL1 due to the operation of the inverter 25. The frequency and amplitude of the above ripple are also represented as the "ripple frequency" and the "ripple amplitude Ra", respectively. Each of the ripple frequency and the ripple amplitude Ra depends on the control state of the motor 27. The ripple amplitude Ra represents the magnitude of the ripple. The greater the resonance component between the inverter 25 and the battery 10, the greater the ripple amplitude Ra. The greater the ripple amplitude Ra, the greater the input / output current of the battery 10 and the greater the power loss due to the internal resistance Rb. Therefore, the heat generation amount of the battery 10 is large.

[0017] The power lines PLa and NLa are connected to the power lines PL1 and NL1, respectively. The switch 40 is provided in a circuit (power lines PLa, NLa, PL2, NL2) that connects the inverter 55 (described later) to the power lines PL1 and NL1.

[0018] The drive device 50 includes a capacitor C2, an inverter 55, and a motor 57. The capacitor C2 is connected between power lines PL2 and NL2. The inverter 55 can be connected to power lines PL1 and NL1 through power lines PLa, NLa, PL2, and NL2 when the switch 40 is in the closed state. The inverter 55 is provided electrically in parallel with the inverter 25 with respect to the battery 10. During four-wheel drive, the inverter 55 receives a current Ib from the battery 10 and generates an alternating current. The motor 57 is a permanent magnet synchronous motor connected to the inverter 55, receives the alternating current from the inverter 55, and is driven by the inverter 55 to generate a driving force for running. The driving force that can be generated by the motor 57 is also referred to as the "second driving force".

[0019] The ECU 70 controls various devices of the BEV1, such as the switch 40 and the inverters 25 and 55. The ECU 70 determines the first driving force and the second driving force according to the required driving force of the BEV1 determined based on the accelerator opening of the BEV1, and thereby controls the inverters 25 and 55. For example, when the switch is in the closed state, the ECU 70 can control the inverters 25 and 55 according to the required driving force so that both the first driving force and the second driving force are generated (four-wheel drive). When the switch is in the open state, the ECU 70 controls the inverter 25 according to the required driving force so that the first driving force that achieves the required driving force is generated (two-wheel drive).

[0020] When the switch 40 is in the closed state, resonance components may exist between the inverters 25 and 55. As a result, even when the temperature rise of the battery 10 is required, the ripple amplitude Ra can be reduced. Therefore, there is a possibility that the heat generation amount of the battery 10 decreases and the battery 10 is not effectively heated. Furthermore, when the battery 10 is heated during the running of the electric vehicle, the situation where the running performance of the BEV1 deteriorates is not preferable.

[0021] Therefore, in the present embodiment, when the temperature rise start condition described above is satisfied while the switch 40 is in the closed state, the ECU 70 switches (opens) the switch 40 from the closed state to the open state. After the switch 40 is switched, the motor 57 stops due to the interruption of the electrical connection between the battery 10 and the inverter 55, and the second driving force decreases (disappears) to zero. However, the ECU 70 controls the inverter 25 according to the required driving force so that the first driving force increases according to the second driving force before the switch 40 is switched (in this example, by applying the second driving force to the first driving force so that the first driving force increases by the amount of decrease in the second driving force). Thereafter, the inverter 25 is controlled so that the motor 27 generates the (total) required driving force of the BEV 1.

[0022] With such a configuration, the electrical connection between the inverters 25 and 55 is interrupted, and resonance components and the like between them disappear. As a result, the resonance component between the inverter 25 and the battery 10 increases, and the ripple amplitude Ra increases. As a result, the heat generation amount of the battery 10 increases, and the battery 10 can be effectively heated. Furthermore, the decrease in the second driving force is compensated by the increase in the first driving force, and the required driving force is ensured by the first driving force. As a result, it is possible to avoid a situation where the running performance of the BEV 1 deteriorates due to the decrease in the second driving force when the switch 40 is switched and ensure the required driving force.

[0023] FIG. 2 is a diagram for explaining the frequency characteristics of the ripple amplitude. Referring to FIG. 2, line 105 represents the relationship between the ripple amplitude and the carrier frequency of the inverter 25 when the switch 40 is in the closed state. Line 110 represents the relationship between the ripple amplitude and the carrier frequency when the switch 40 is in the open state.

[0024] The frequency range RNG is the range of values that the carrier frequency can take. The frequency range RNGa is defined as the range within the frequency range RNG in which the ripple amplitude when the switch 40 is in the open state is larger than the ripple amplitude when the switch 40 is in the closed state. The inventors confirmed that the increase in the ripple amplitude Ra (increase in the heat generation amount of the battery 10) caused by the switching of the switch 40 occurs within a wide frequency range (frequency range RNGa).

[0025] In order to achieve the required driving force of BEV1, since the motor current frequency needs to be determined based on the required driving force, the control state of the inverter 25 can be restricted to some extent. On the other hand, the control state of the inverter 25 that is suitable from the perspective of the required driving force does not necessarily coincide with the control state of the inverter 25 that is suitable from the perspective of the temperature rise (ripple amplitude) of the battery 10. In this case, complex control may be required to balance the temperature rise of the battery 10 and the required driving force.

[0026] In the embodiment, the ECU 70 only needs to control the inverter 25 within the frequency range RNGa so that the first driving force increases by switching the switch 40 from the closed state to the open state in order to increase the heat generation amount (ripple amplitude) of the battery 10 during the running of the BEV1. As a result, complex control is not required to balance the temperature rise of the battery 10 and the required driving force. Therefore, it is possible to balance the temperature rise of the battery 10 and the required driving force while simplifying the control of the BEV1 during the temperature rise of the battery 10 during running.

[0027] FIG. 3 is a flowchart illustrating the procedure of the process executed by the ECU 70. At the start of this flowchart, the switch 40 is in the closed state. In the subsequent steps (also abbreviated as "S"), the carrier frequency is controlled within the frequency range RNGa.

[0028] Referring to FIG. 3, the ECU 70 determines whether the warm-up start condition is satisfied. In this example, it determines whether the temperature Tb is less than the threshold temperature (S105). If the temperature Tb is greater than or equal to the threshold temperature (NO in S105), the process ends. If the temperature Tb is less than the threshold temperature (YES in S105), the ECU 70 switches the switch 40 from the closed state to the open state (S110). As a result, due to the increase in the ripple amplitude, the heat generation amount of the battery 10 increases and the temperature Tb rises. The ECU 70 controls the inverter 25 so that the first driving force increases to the maximum in order to cope with the disappearance of the second driving force caused by the switching of the switch 40 (S115). In this example, only the first driving force increases by the amount of the second driving force before the switching of the switch 40.

[0029] The ECU 70 determines whether the temperature Tb has risen to the threshold temperature (S125). If the temperature Tb has not yet risen to the threshold temperature (NO in S125), the process returns to S125. When the temperature Tb rises to the threshold temperature (YES in S125), the ECU 70 switches the switch 40 from the open state to the closed state (S135). As a result, the warming-up of the battery 10 ends. Thereafter, the ECU 70 determines the first driving force and the second driving force again according to the required driving force, and controls the inverters 25 and 55 so that only the first driving force is reduced by the amount of the second driving force thus determined and the second driving force is generated again by the motor 57 (S140). Then, the process ends.

[0030] As described above, according to the embodiment, it is possible to avoid a decrease in the running performance of the BEV 1 while effectively warming up the battery 10.

[0031] [Modification Example] BEV1 may further include a high-voltage auxiliary machine (e.g., an air conditioner) and a switch for the high-voltage auxiliary machine (not shown) provided in the electric circuit between this auxiliary machine and the battery 10. The high-voltage auxiliary machine is connected to the battery 10 and is provided in parallel with the inverter 25 with respect to the battery 10. When the temperature rise start condition is satisfied when the switch for the high-voltage auxiliary machine is in the closed state, the ECU 70 switches this switch from the closed state to the open state (for example, when both the switch 40 and the switch for the high-voltage auxiliary machine are in the closed state, both of these switches are switched from the closed state to the open state). As a result, the electrical connection between the high-voltage auxiliary machine and the battery 10 is interrupted, and the resonance component between the high-voltage auxiliary machine and the battery 10 disappears. As a result, the resonance component between the inverter 25 and the battery 10 increases and the ripple amplitude Ra increases. Therefore, even when BEV1 further includes a high-voltage auxiliary machine, the battery 10 can be heated up easily and effectively.

[0032] [Other Modifications] BEV1 may be replaced by other types of electric vehicles such as an HEV (Hybrid Electric Vehicle) further including an internal combustion engine.

[0033] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0034] 10 Battery, 25, 55 Inverter, 27, 57 Motor, 40 Switch, 70 ECU.

Claims

【Claim 1】 An electric vehicle, comprising: a power storage device; a first inverter connected to the power storage device through a pair of power lines; a first rotating electric machine driven by the first inverter to generate a first driving force; a second inverter configured to be connectable to the pair of power lines and provided electrically in parallel with the first inverter with respect to the power storage device; a second rotating electric machine configured to be drivable by the second inverter and capable of generating a second driving force; a switch provided in a circuit connecting the second inverter to the pair of power lines; a control device configured to control the first inverter and the second inverter according to a required driving force of the electric vehicle such that the first driving force and the second driving force are generated when the switch is in a closed state; when the switch is in a closed state and a temperature rise start condition for starting a temperature rise of the power storage device is satisfied, the control device switches the switch from the closed state to an open state, and controls the first inverter according to the required driving force such that the first driving force increases according to the second driving force before the switching of the switch.

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