Electrified vehicle

Abstract

The electrified vehicle of the present disclosure comprises a main power source, a drive unit, a relay, a load unit, a DC / DC converter, and an auxiliary power source. The load unit is operated by power supplied from the main power source or power supplied from the auxiliary power source through the DC / DC converter. The electrified vehicle has a Ready-on state and a Ready-off state in which the operation of the load unit is stopped. A first upper limit voltage, which is the output upper limit voltage of the DC / DC converter in the Ready-on state, is smaller than a second upper limit voltage, which is the output upper limit voltage of the DC / DC converter in the Ready-off state.

Description

Technology Field

[0001] The present disclosure relates to an electrified vehicle. Background Technology

[0002] Japanese Patent Publication No. 2014-107968 discloses an electrified vehicle equipped with a storage device (hereinafter referred to as the main power source), a driving device, a load device, a DC / DC converter, and an auxiliary power source. The driving device and the DC / DC converter are connected in parallel to the main power source. The load device and the auxiliary power source are connected in parallel to the DC / DC converter to form an auxiliary circuit. The load device is operated by power supplied from the main power source or power supplied from the auxiliary power source through the DC / DC converter. If the power supplied to the load device from the DC / DC converter is insufficient, power is supplied to the load device from the auxiliary power source. If the residual capacity of the auxiliary power source decreases due to the power supply to the load device, the auxiliary power source is charged by power from the main power source. Charging of the auxiliary power source by power from the main power source is called pumping charging. The problem to be solved

[0003] A DC / DC converter has, for example, an inductor. The inductor smooths out changes in current through the accumulation and release of energy. The energy accumulated in the inductor is determined by the current flowing through the auxiliary circuit. When a load device receiving power from the DC / DC converter stops, the inductor releases the accumulated energy to mitigate current fluctuations. The energy released from the DC / DC converter may be supplied to the auxiliary power supply as an overcurrent. Charging of the auxiliary power supply due to overcurrent may accelerate the degradation of the auxiliary power supply.

[0004] The present disclosure is made to solve the above problem, and the purpose is to provide an electrified vehicle capable of suppressing the acceleration of deterioration of an auxiliary power source by charging an overcurrent that occurs to mitigate load fluctuations. means of solving the problem

[0005] The electrified vehicle of the present disclosure comprises a main power source, a drive unit, a relay, a load unit, a DC / DC converter, and an auxiliary power source. The drive unit and the DC / DC converter are connected in parallel to the main power source. The auxiliary power source and the load unit are connected in parallel to the DC / DC converter. A relay is positioned between the main power source and the drive unit. A DC / DC converter is connected between the relay and the main power source. The drive unit generates driving power by power supplied from the main power source. The load unit is operated by power supplied from the main power source or power supplied from the auxiliary power source through the DC / DC converter. The electrified vehicle has a Ready-on state in which the relay is closed and a Ready-off state in which the operation of the load unit is stopped when the relay is opened. A first upper limit voltage, which is the output upper limit voltage of the DC / DC converter in the Ready-on state, is smaller than a second upper limit voltage, which is the output upper limit voltage of the DC / DC converter in the Ready-off state.

[0006] In the electric vehicle of the present disclosure, during pumping charging in which power is supplied from the main power source to the auxiliary power source in the Ready-off state, the output voltage of the DC / DC converter at the start of pumping charging may be increased over time so as to approach the second upper limit voltage.

[0007] The electrified vehicle of the present disclosure may include a plurality of capacitor cells connected in series as an auxiliary power source. The second upper limit voltage may be smaller than the value obtained by multiplying the nominal voltage of the plurality of capacitor cells by the number of the plurality of capacitor cells.

[0008] The electrified vehicle of the present disclosure may further be provided with a control unit that indicates an output upper limit voltage of a DC / DC converter. The control unit may acquire battery characteristic information of an auxiliary power source. The battery characteristic information may include temperature information of the auxiliary power source. The control unit may determine a second upper limit voltage based on the battery characteristic information.

[0009] The electrified vehicle of the present disclosure may further comprise a control unit for setting an output upper limit voltage of a DC / DC converter. The control unit may acquire battery characteristic information of an auxiliary power source. The battery characteristic information may include information on the open-circuit voltage of the auxiliary power source. The control unit may determine a second upper limit voltage based on the battery characteristic information. Effects of the invention

[0010] According to the electrified vehicle related to the present disclosure, the deterioration of the auxiliary power source due to overcurrent charging that occurs to mitigate load fluctuations can be suppressed. Brief explanation of the drawing

[0011] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein the same reference numerals denote the same elements. FIG. 1 is a schematic diagram of an electrified vehicle related to an embodiment of the present disclosure; FIG. 2 is a flowchart of control performed by an electrified vehicle related to an embodiment of the present disclosure; FIG. 3 is a diagram showing the relationship between temperature information related to an embodiment of the present disclosure and a second upper limit voltage; FIG. 4 is a diagram showing the relationship between information on the open-circuit voltage and the second upper limit voltage related to an embodiment of the present disclosure. Specific details for implementing the invention

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or substantial parts are given the same reference numerals, and their descriptions are not repeated.

[0013] Schematic configuration of an electrified vehicle

[0014] FIG. 1 is a diagram showing the schematic configuration of an electrified vehicle related to an embodiment of the present disclosure.

[0015] The electrified vehicle (1) is, for example, a battery electric vehicle. The electrified vehicle (1) is equipped with a drive unit (10), a system main relay (SMR) (14), an ECU (20), a battery storage unit (40), a DC / DC converter (50), a plurality of load units (60), an auxiliary power supply (70), and a monitoring unit (80).

[0016] The driving device (10) and the DC / DC converter (50) are connected in parallel to the energy storage device (40). A plurality of load devices (60) and auxiliary power sources (70) are connected in parallel to the DC / DC converter (50). The SMR (14) is positioned between the energy storage device (40) and the driving device (10). The DC / DC converter (50) is positioned between the SMR (14) and the energy storage device (40).

[0017] The driving device (10) is configured to generate driving power by power supplied from the storage device (40). The driving device (10) includes a motor generator (MG) (11) which is a rotating electric motor, a driving wheel (12), and a power control unit (PCU) (13).

[0018] MG (11) is, for example, an embedded structure permanent magnet synchronous motor (IPM motor) and has the function of a motor and a generator. The output torque of MG (11) is transmitted to the drive wheel (12) through a power transmission device including a reduction gear and a differential.

[0019] When the electric vehicle (1) is being braked, the MG (11) is driven by the drive wheel (12), and the MG (11) operates as a generator. Thus, the MG (11) also functions as a braking device that performs regenerative braking to convert the kinetic energy of the electric vehicle (1) into electricity. The regenerative power generated by the regenerative braking force in the MG (11) is stored in the battery storage device (40).

[0020] The PCU (13) is a power conversion device that converts power bidirectionally between the MG (11) and the battery storage device (40). The PCU (40) includes an inverter and a converter that operate based on a control signal from, for example, the ECU (300). When the battery storage device (40) is discharged, the converter steps up the voltage supplied from the battery storage device (40) and supplies it to the inverter. The inverter converts the DC power supplied from the converter into AC power to drive the MG (11). Additionally, the PCU (13) may be configured without the converter.

[0021] The SMR (14) is formed between the capacitor (40) and the drive unit (10). When the SMR (14) is closed (ON) (i.e., in a conductive state) according to a control signal from the ECU (20), power can be exchanged between the capacitor (40) and the PCU (13). On the other hand, when the SMR (14) is open (OFF) (i.e., in a cutoff state) according to a control signal from the ECU (20), the electrical connection between the capacitor (40) and the PCU (13) is cut off. The SMR (14) is closed (ON), for example, when the ignition power of the electrified vehicle (1) is turned ON. The SMR (14) functions as a protection device during the operation of the electrified vehicle (1). Furthermore, the SMR (14) is an example of a “relay” of the present disclosure.

[0022] The ECU (20) includes a processor (21), memory (22), storage (23), and a communication unit (24). The processor (21) is a computing device such as a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The memory (22) is a volatile memory (working memory) such as RAM (Random Access Memory). The storage (23) is a rewritable non-volatile memory such as flash memory. The storage (23) stores a system program including an OS (Operating System) and a control program including computer-readable code required for control operations. The communication unit (24) is configured to communicate with the PCU (13), the SMR (14), the DC / DC converter (50), and the monitoring unit (80). The ECU (20) realizes various processing by having the processor (21) read system programs and control programs, deploy them to memory (22), and execute them.

[0023] The ECU (20) instructs the DC / DC converter (50) to set the output upper limit voltage of the DC / DC converter (50). The ECU (20) stores the information obtained from the monitoring unit (80) in memory (22) along with time information. The information obtained from the monitoring unit (80) is called battery characteristic information.

[0024] The ECU (20) may be divided into multiple ECUs for each function. Also, the ECU (20) is an example of the “control unit” of the present disclosure.

[0025] The energy storage device (40) is mounted on an electrified vehicle (1). The energy storage device (40) supplies power to the drive unit (10) and the DC / DC converter (50). Additionally, the energy storage device (40) is an example of the “main power source” of the present disclosure.

[0026] The DC / DC converter (50) operates based on a control signal from, for example, the ECU (20). More specifically, when the capacitor (40) is discharged, the DC / DC converter (50) steps down the power supplied from the capacitor (40) to an output voltage based on instructions from the ECU (20) and supplies it to a plurality of load devices (60) or auxiliary power sources (70).

[0027] Each of the multiple load devices (60) is operated by power supplied from the storage device (40) through the DC / DC converter (50), or by power supplied from the auxiliary power source (70). The multiple load devices (60) refer to headlights, air conditioners, heaters, etc., mounted on the electrified vehicle (1).

[0028] The auxiliary power supply (70) supplies power to a plurality of load devices (60). The auxiliary power supply (70) is configured to be rechargeable by power from a DC / DC converter (50). The auxiliary power supply (70) has a plurality of capacitor cells (71) connected in series. The capacitor cells (71) are secondary batteries such as nickel-hydrogen batteries or lithium-ion batteries. A secondary battery is, for example, a battery having a liquid electrolyte between a positive electrode and a negative electrode. Additionally, the auxiliary power supply (70) may be a capacitor such as a capacitor.

[0029] The monitoring unit (80) is configured to acquire battery characteristic information. The battery characteristic information includes information on the current flowing through the auxiliary power source (70), information on the voltage of each capacitor cell (71), and information on the temperature. The monitoring unit (80) is configured to output the battery characteristic information to the ECU (20). Based on the acquired battery characteristic information of each of the multiple capacitor cells (71), the monitoring unit (80) also functions as a BMS (Battery Management System) having a SOC (State Of Charge) estimation function that estimates the SOC, a SOH (State of Health) estimation function that estimates the SOH of each of the multiple capacitor cells (71), and a communication function. The battery characteristic information also includes the SOC or SOH of each of the multiple capacitor cells (71) estimated by the monitoring unit (80). In addition, SOH is an indicator representing the degree of degradation of the battery, and is represented by the ratio of the initial full charge capacity of the battery to the actual full charge capacity. The closer the SOH is to 0%, the more the degradation of the battery is progressing. The monitoring unit (80) has a voltage sensor (81), a current sensor (82), and a temperature sensor (83).

[0030] The voltage sensor (81) is configured to measure the voltage between terminals of the auxiliary power supply (70) and output the measurement result to the ECU (20). The voltage between terminals of the auxiliary power supply (70) measured by the voltage sensor (81) includes the open-circuit voltage. Additionally, the voltage sensor (81) is configured to measure the voltage of each of the plurality of capacitor cells (71) and output the measurement result to the ECU (20). Furthermore, the voltage sensor (81) may be configured to measure only the voltage between terminals of the auxiliary power supply (70).

[0031] The current sensor (82) is formed outside the auxiliary power supply (70). The current sensor (82) is formed to measure the charging and discharging current of the auxiliary power supply (70) and output the measurement result to the ECU (20). For example, when the auxiliary power supply (70) is discharged, the current sensor (82) may use a positive value as the current value measured by the current sensor (82). Also, for example, when the auxiliary power supply (70) is being charged, the current sensor (82) may use a negative value as the current value measured by the current sensor (82).

[0032] The temperature sensor (83) is configured to measure the temperature of each of the plurality of capacitor cells (71) and output the measurement result to the ECU (20). The temperature sensor (83) may be configured to measure the temperature of at least one of the plurality of capacitor cells (71). Additionally, the temperature sensor (83) may measure the temperature of a portion of the auxiliary power supply (70). Furthermore, the ECU (20) may estimate the temperature of the plurality of capacitor cells (71) from the temperature of the portion of the auxiliary power supply (70) obtained from the temperature sensor (83).

[0033] The electrified vehicle (1) in the embodiment of the present disclosure has a Ready-on state and a Ready-off state. The Ready-on state refers to a state in which the SMR (14) is closed (ON) and power can be supplied from the storage device (40) to the driving device (10). The Ready-off state refers to a state in which the SMR (14) is open (OFF) and all operations of a plurality of load devices (60) are stopped.

[0034] In an embodiment of the present disclosure, the electrified vehicle (1) is configured to be able to charge an auxiliary power source (70) by the power of a storage device (40) in both the Ready-on state and the Ready-off state. In particular, supplying power to the auxiliary power source (70) from the storage device (40) through a DC / DC converter (50) in the Ready-off state is called pumping charging.

[0035] The ECU (20) instructs the DC / DC converter (50) to output voltage. Based on the instruction of output voltage from the ECU (20), the DC / DC converter (50) converts (steps down) the power supplied from the storage device (40) and supplies it to a plurality of load devices (60) or auxiliary power sources (70). The upper limit of the output voltage of the DC / DC converter (50) in the Ready-on state is called the first upper limit voltage V1. The upper limit of the output voltage of the DC / DC converter (50) in the Ready-off state is called the second upper limit voltage V2. The second upper limit voltage V2 refers to the upper limit of the voltage applied to the auxiliary power source (70) when the electrified vehicle (1) is in the Ready-off state. In addition, the first upper limit voltage V1, which is the output upper limit voltage of the DC / DC converter (50) in the Ready-on state, is smaller than the second upper limit voltage V2, which is the output upper limit voltage of the DC / DC converter (50) in the Ready-off state.

[0036] In an electrified vehicle (1) related to an embodiment of the present disclosure, the first upper limit voltage V1, which is the output upper limit voltage of the DC / DC converter (50) in the Ready-on state, is smaller than the second upper limit voltage V2, which is the output upper limit voltage of the DC / DC converter (50) in the Ready-off state. This allows for the suppression of the deterioration of the auxiliary power source (70) caused by the charging of overcurrents that occur to mitigate load fluctuations. Additionally, by making the second upper limit voltage V2 larger than the first upper limit voltage V1, the charging time of the auxiliary power source (70) can be shortened. Details are described below.

[0037] In the Ready-on state, power output from the DC / DC converter (50) is supplied to a plurality of load devices (60) and an auxiliary power supply (70). When the plurality of load devices (60) stop simultaneously, energy accumulated in the inductor built into the DC / DC converter (50) is released so that the power supplied from the DC / DC converter (50) does not drop rapidly. The energy released from the inductor is supplied to the auxiliary power supply (70) as an overcurrent. An overcurrent exceeding the allowable charging current may accelerate the deterioration of the auxiliary power supply (70). In the Ready-on state, in order to suppress the deterioration of the auxiliary power supply (70) due to the overcurrent, it is necessary to suppress the energy accumulated in the inductor by suppressing the first upper limit voltage V1.

[0038] Meanwhile, in the Ready-off state, since the multiple load devices (60) are stopped, no load fluctuation occurs due to the switching between operation and stop of the multiple load devices (60). Therefore, no overcurrent is generated due to load fluctuation. As a result, since there is no need to suppress the energy accumulated in the inductor, the second upper limit voltage V2 of the DC / DC converter (50) in the Ready-off state can be made greater than the first upper limit voltage V1 of the DC / DC converter (50) in the Ready-on state.

[0039] In an electrified vehicle (1) related to an embodiment of the present disclosure, the second upper limit voltage V2 is smaller than the value obtained by multiplying the nominal voltage of a plurality of capacitor cells (71) by the number of capacitor cells (71). By doing so, the voltage applied to the auxiliary power source (70) can be suppressed from exceeding the allowable charging voltage of the auxiliary power source (70). And, the deterioration of the auxiliary power source (70) can be suppressed.

[0040] Control flow of an electrified vehicle

[0041] Next, with reference to FIG. 2, a pumping charge control flow performed by an electrified vehicle (1) will be described.

[0042] In step S10 shown in FIG. 2, the ECU (20) checks whether the electrified vehicle (1) is in a Ready-off state. More specifically, the ECU (20) checks whether the SMR (14) is open (OFF) and whether all of the load devices (60) have stopped operating. If the electrified vehicle (1) is in a Ready-off state (Yes in step S10), the processing of the ECU (20) proceeds to step S20. If it is not in a Ready-off state (No in step S10), the ECU (20) processes step S10 again.

[0043] In step S20, the ECU (20) checks whether the remaining charge capacity of the auxiliary power supply (70) is less than or equal to a first threshold value C1. The first threshold value C1 is, for example, 40%. If the remaining charge capacity of the auxiliary power supply (70) is less than or equal to the first threshold value C1 (Yes in step S20), the processing of the ECU (20) proceeds to step S30. If the remaining charge capacity of the auxiliary power supply (70) is not less than or equal to the first threshold value C1 (No in step S20), the ECU (20) processes step S20 again.

[0044] In step S20, by repeatedly checking the remaining charge capacity of the auxiliary power supply (70) by the ECU (20), the remaining charge capacity of the auxiliary power supply (70) can be prevented from being depleted by the dark current from the auxiliary power supply (70) in the Ready-off state.

[0045] In step S30, the ECU (20) obtains battery characteristic information from the monitoring unit (80). The battery characteristic information includes information on the current flowing through the auxiliary power supply (70), information on the voltage of each of the plurality of capacitor cells (71), and information on the temperature.

[0046] In step S40, the ECU (20) determines a second upper limit voltage V2 based on battery characteristic information. The battery characteristic information includes, for example, information on the temperature of the auxiliary power supply (70) or information on the open-circuit voltage of the auxiliary power supply (70).

[0047] The ECU (20) stores the table shown in FIG. 3 in advance. FIG. 3 is a table showing the relationship between the information of temperature T and the second upper limit voltage V2. The temperature T shown in FIG. 3 represents higher temperatures in the order of T3, T2, and T1. The second upper limit voltage V2 shown in FIG. 3 represents higher voltages in the order of V23, V22, and V21. That is, FIG. 3 indicates that the second upper limit voltage V2 can be increased as the temperature T increases. The ECU (20) determines the second upper limit voltage V2 using the table shown in FIG. 3 based on the measurement value acquired by the temperature sensor (83) among the battery characteristic information. The ECU (20) may apply the average of the measurements of each of the multiple capacitor cells (71) acquired by the temperature sensor (83) to the temperature T of FIG. 3, or may apply the lowest value among the measurements of each of the multiple capacitor cells (71) acquired by the temperature sensor (83) to the temperature T of FIG. 3.

[0048] The ECU (20) may, for example, store the table shown in FIG. 4 in advance. FIG. 4 is a table showing the relationship between the information of the open-circuit voltage OCV of the auxiliary power supply (70) and the second upper limit voltage V2. The open-circuit voltage OCV shown in FIG. 4 shows voltages that are larger in the order of OCV3, OCV2, and OCV1. The second upper limit voltage V2 shown in FIG. 4 shows voltages that are larger in the order of V26, V25, and V24. That is, FIG. 4 indicates that the larger the OCV, the larger the second upper limit voltage V2 can be made. The ECU (20) determines the second upper limit voltage V2 using the table shown in FIG. 4 based on the measurement value acquired by the voltage sensor (81) among the battery characteristic information.

[0049] In step S50, the ECU (20) checks whether the electrified vehicle (1) is in a Ready-off state. If the electrified vehicle (1) is in a Ready-off state (Yes in step S50), the processing of the ECU (20) proceeds to step S60. If it is not in a Ready-off state (No in step S50), the ECU (20) terminates the processing of the pumping charge control.

[0050] In step S60, the ECU (20) instructs the DC / DC converter (50) to output voltage Vo and performs pumping charging. Output voltage Vo is the output voltage that the ECU (20) instructed the DC / DC converter (50) just before transitioning from the Ready-on state to the Ready-off state. Output voltage Vo may be, for example, the first upper limit voltage V1.

[0051] In step S70, the ECU (20) checks whether the remaining battery capacity of the auxiliary power source (70) is greater than or equal to a second threshold value C2. The second threshold value C2 is, for example, 90%. The ECU (20) checks whether the remaining battery capacity of the auxiliary power source (70) is greater than or equal to the second threshold value C2 based on the information on the remaining battery capacity of the auxiliary power source (70) obtained from the monitoring unit (80). Additionally, the ECU (20) may calculate the remaining battery capacity of the auxiliary power source (70) based on the battery characteristic information obtained from the monitoring unit (80). If the remaining battery capacity of the auxiliary power source (70) is greater than or equal to the second threshold value C2 (Yes in step S70), the ECU (20) terminates the processing of the pumping charge control. If the remaining battery capacity of the auxiliary power supply (70) is not greater than or equal to the second threshold value C2 (No in step S70), the processing of the ECU (20) proceeds to step S80.

[0052] In step S80, the ECU (20) checks whether the output voltage Vo has reached the second upper limit voltage V2. If the output voltage Vo has reached the second upper limit voltage V2 (Yes in step S80), the processing of the ECU (20) proceeds to step S50. If the output voltage Vo has not reached the second upper limit voltage V2 (No in step S80), the processing of the ECU (20) proceeds to step S90.

[0053] In step S90, the ECU (20) adds voltage v to the output voltage Vo. After that, the processing of the ECU (20) proceeds to step S50.

[0054] In a control flow related to an embodiment of the present disclosure, the ECU (20) repeatedly adds voltage v to the output voltage Vo until the output voltage Vo reaches a second upper limit voltage V2 (step S90). By doing so, the ECU (20) can increase the output voltage Vo of the DC / DC converter (50) at the start of pumping charging over time so that it approaches the second upper limit voltage V2. As a result, the fluctuation of the voltage applied to the auxiliary power supply (70) can be smoothed out.

[0055] The embodiments disclosed herein should be considered as illustrative and not limiting in all respects. The scope of this disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

Claim 1 An electrified vehicle comprising a main power source, a drive unit, a relay, a load unit, a DC / DC converter, and an auxiliary power source, wherein the drive unit and the DC / DC converter are connected in parallel to the main power source, the auxiliary power source and the load unit are connected in parallel to the DC / DC converter, the relay is positioned between the main power source and the drive unit, and the DC / DC converter is connected between the relay and the main power source, the drive unit generates driving force by power supplied from the main power source, and the load unit is operated by power supplied from the main power source or power supplied from the auxiliary power source through the DC / DC converter, and the electrified vehicle has a Ready-on state in which the relay is closed and a Ready-off state in which the operation of the load unit is stopped when the relay is opened, and a first upper limit voltage, which is the output upper limit voltage of the DC / DC converter in the Ready-on state, is the output upper limit voltage of the DC / DC converter in the Ready-off state An electrified vehicle with a voltage lower than the second upper limit. Claim 2 An electrified vehicle according to claim 1, wherein, during pumping charging in which power is supplied from the main power source to the auxiliary power source in the Ready-off state, the output voltage of the DC / DC converter at the start of pumping charging is increased over time so as to approach the second upper limit voltage. Claim 3 An electrified vehicle according to claim 1, wherein the auxiliary power source comprises a plurality of capacitor cells connected in series, and the second upper limit voltage is smaller than the value obtained by multiplying the nominal voltage of the plurality of capacitor cells by the number of the plurality of capacitor cells. Claim 4 An electrified vehicle according to claim 1 or 2, further comprising a control unit indicating the output upper limit voltage of the DC / DC converter, wherein the control unit acquires battery characteristic information of the auxiliary power source, wherein the battery characteristic information includes temperature information of the auxiliary power source, and wherein the control unit determines the second upper limit voltage based on the battery characteristic information. Claim 5 An electrified vehicle according to claim 1 or 2, further comprising a control unit for setting the output upper limit voltage of the DC / DC converter, wherein the control unit acquires battery characteristic information of the auxiliary power source, the battery characteristic information includes information on the open-circuit voltage of the auxiliary power source, and the control unit determines the second upper limit voltage based on the battery characteristic information.

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