vehicle

Abstract

When the battery voltage drops, the effects of polarization are eliminated, allowing for optimal starting of the internal combustion engine. [Solution] The vehicle is a plug-in hybrid vehicle equipped with a battery that can be charged at the open. The vehicle runs in CD mode when the battery's SOC is equal to or greater than a first SOC value α, and runs in CS mode when the SOC falls below the first SOC value α. The ECU starts the engine when the battery voltage TB remains below a threshold Cv for a predetermined time T. The threshold Cv is set higher than Co, which corresponds to the voltage TB corresponding to the first SOC value α.

Description

Technical Field

[0001] This disclosure relates to vehicles.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2013 - 237298 (Patent Document 1) discloses a plug - in hybrid vehicle. In this hybrid vehicle of Patent Document 1, during EV driving, when the battery voltage drops below a predetermined threshold value, the engine is started and HV driving is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] During charging and discharging of the battery, polarization occurs. When polarization occurs, the battery voltage drops. In particular, when the charging and discharging current is at a high rate and when the SOC (State Of Charge) of the battery is small (low), the polarization becomes large. In Patent Document 1, the decrease in battery voltage due to polarization is not considered. Therefore, even when the battery voltage drops below the threshold value in an extremely short time due to polarization, there is a concern of starting the engine.

[0005] An object of this disclosure is to eliminate the influence of polarization and preferably start the internal combustion engine when the voltage of the battery drops.

Means for Solving the Problems

[0006] The vehicle disclosed herein is equipped with an internal combustion engine, a battery that can be externally charged by power supplied from an external power source, a rotating electric machine that generates driving force using the power stored in the battery, and a control device. The control device can switch between a CD (Charge Depleting) mode, in which the vehicle runs by consuming the power stored in the battery, and a CS (Charge Sustaining) mode, in which the vehicle runs while maintaining the battery's State of Charge (SOC) within a predetermined range. When the vehicle is running in CD mode, the control device starts the internal combustion engine when the battery voltage remains below a threshold for a predetermined period of time.

[0007] In this configuration, when driving in CD mode, the internal combustion engine is started if the battery voltage remains below a threshold for a predetermined period of time. During battery discharge, polarization may cause the battery voltage to briefly fall below the threshold. This voltage drop due to polarization does not persist for a predetermined period of time. Therefore, when the battery voltage drops, it becomes possible to start the internal combustion engine while eliminating the effects of polarization.

[0008] Preferably, the control device switches from CD mode to CS mode when the battery's SOC falls below a first SOC value, and the threshold may be set higher than the battery voltage corresponding to the first SOC value.

[0009] In this configuration, the threshold is set higher than the battery voltage corresponding to the first SOC value at which the vehicle switches from CD mode to CS mode. The internal combustion engine starts before switching to CS mode. When driving in CS mode, for example, the engine has warmed up, which can reduce emissions in CS mode.

[0010] Preferably, the control device may start the internal combustion engine when the battery's SOC is less than or equal to a second SOC value greater than a first SOC value, and the battery voltage remains below a threshold for a predetermined period of time while driving in CD mode.

[0011] This configuration allows for the effective start of an internal combustion engine by eliminating the effects of polarization, even at low states of charge (SOC) where the polarization of the battery becomes significant.

[0012] Preferably, the control device may be configured to stop the operation of the internal combustion engine after it has been started and the warm-up period has been completed.

[0013] With this configuration, the internal combustion engine is stopped once the engine has warmed up, thus effectively reducing emissions in CS mode. [Effects of the Invention]

[0014] According to this disclosure, when the battery voltage drops, the effects of polarization can be eliminated, and the internal combustion engine can be started suitably. [Brief explanation of the drawing]

[0015] [Figure 1] This diagram schematically shows the overall configuration of the vehicle according to this embodiment. [Figure 2] This flowchart shows an example of mode switching control performed by the ECU300. [Figure 3] This flowchart shows an example of engine start control performed by the ECU300. [Figure 4] This diagram illustrates the relationship between the first SOC value α and the threshold Cv. [Modes for carrying out the invention]

[0016] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0017] Figure 1 is a schematic diagram showing the overall configuration of vehicle 1 according to this embodiment. Figure 1 shows that vehicle 1 and charging equipment 5 are electrically connected by charging cable 3, and that vehicle 1 and charging equipment 9 are electrically connected by charging cable 7.

[0018] The charging device 5 is, for example, an ordinary charger installed in a general household. The charging device 5 outputs AC power supplied from the grid power, which is an external power source, to the vehicle 1. The charging device 9 is a rapid charger that converts the AC power of the grid power, which is an external power source, into DC power and outputs it to the vehicle 1. When the vehicle 1 is externally charged, either one of the charging device 5 or the charging device 9 and the vehicle 1 are electrically connected by a charging cable.

[0019] The vehicle 1 is a plug-in hybrid vehicle. The vehicle 1 includes a motor generator (MG) 101, an MG 102, an engine 103, a power split device 104, drive wheels 105, a power control unit (PCU) 106, a system main relay (SMR) 108, a battery 200, charging relays 110, 120, a charger 111, inlets 112, 122, and a control unit (ECU) 300.

[0020] Each of the MG101 and 102 is, for example, a three-phase AC rotating electric machine in which a permanent magnet is embedded in a rotor (not shown). The MG101 is connected to the crankshaft of the engine 103 via the power split device 104. The MG101 rotates the crankshaft of the engine 103 using the power of the battery 200 when starting the engine 103. Also, the MG101 can generate electricity using the power of the engine 103. The AC power generated by the MG101 is converted into DC power by the PCU106 and charged into the battery 200. Also, the AC power generated by the MG101 may be supplied to the MG102.

[0021] The MG102 rotates the drive shaft using at least one of the power from the battery 200 and the power generated by the MG101. Also, the MG102 can generate electricity by regenerative braking. The AC power generated by the MG102 is converted into DC power by the PCU106 and charged into the battery 200.

[0022] The engine 103 is an internal combustion engine such as a gasoline engine or a diesel engine, and generates power for the vehicle 1 to run according to a control signal from the ECU 300. An exhaust purification catalyst CT is provided in the exhaust passage EX of the engine 103. The exhaust purification catalyst CT may be a three-way catalyst in the case of a gasoline engine, or a NOx purification catalyst in the case of a diesel engine.

[0023] The power split device 104 is, for example, a planetary gear mechanism, and splits the power generated by the engine 103 into power transmitted to the drive wheels 105 and power transmitted to the MG 101.

[0024] The PCU 106 converts the DC power stored in the battery 200 into AC power and supplies it to the MG 101 and 102 according to a control signal from the ECU 300. The PCU 106 converts the AC power generated by the MG 101 and 102 into DC power and supplies it to the battery 200.

[0025] The SMR 108 is electrically connected to the power line connecting the PCU 106 and the battery 200. The SMR 108 switches the supply and cut-off of power between the PCU 106 and the battery 200 according to a control signal from the ECU 300.

[0026] The battery 200 is a secondary battery configured to be chargeable and dischargeable. The battery 200 may be a secondary battery such as a lithium-ion secondary battery or a nickel-metal hydride battery. The battery 200 is a battery pack in which a plurality of single cells (battery cells) are connected in series, for example. The battery 200 supplies power for generating the driving force of the vehicle 1 to the PCU 106. The battery 200 also stores the power generated by the MG 101.

[0027] The monitoring unit 210 includes a voltage sensor, a current sensor, and a temperature sensor (not shown). The voltage sensor detects the voltage VB of the battery 200 (battery cell). The current sensor detects the current IB being input to and output from the battery 200. The temperature sensor detects the temperature TB of the battery 200. The voltage VB, current IB, and temperature TB are output to the ECU 300.

[0028] The charging relay 110 is electrically connected to the power line connecting the battery 200 and the charger 111. The charging relay 110 switches between supplying and cutting off power between the battery 200 and the charger 111 in response to a control signal from the ECU 300.

[0029] The charger 111 is configured, for example, to include an AC / DC converter, which converts the AC power supplied from the charging equipment 5 via the charging cable 3 and inlet 112 into DC power and outputs it to the charging relay 110. When the vehicle 1 (battery 200) is externally charged using the power supplied from the charging equipment 5 (normal charging), the charging relay 110 is closed, and the power supplied to the vehicle 1 is controlled by the charger 111.

[0030] The inlet 122 receives DC power supplied from the charging equipment 9 when the charging cable 7 is connected to it. The charging relay 120 is electrically connected to the power line connecting the battery 200 and the inlet 122. The charging relay 120 switches the supply and interruption of power between the battery 200 and the inlet 122 according to a control signal from the ECU 300. When the vehicle 1 (battery 200) is externally charged using power supplied from the charging equipment 9 (rapid charging), the charging relay 120 is closed, and the power supplied to the vehicle 1 is controlled by a controller installed in the charging equipment 9 (rapid charger).

[0031] The ECU300 consists of a CPU (Central Processing Unit) 301, a memory 302, and a buffer (not shown). Based on inputs from the monitoring unit 210 and various sensors (not shown) (for example, accelerator opening signal, vehicle speed signal, etc.), as well as maps and programs stored in memory, the ECU300 controls each device so that the vehicle 1 reaches a desired state. One of the controls performed by the ECU300 is "mode switching control".

[0032] Vehicle 1 operates in either CD mode or CS mode. CD mode is a driving mode in which the vehicle 1 continues to operate electrically (EV) using the power of the battery 200 with the engine 103 stopped as much as possible, and consumes the power stored in the battery 200. CS mode is a driving mode in which the engine 103, MG101 and MG102 are used to maintain the state of charge (SOC) of the battery 200 within a predetermined range. In this embodiment, the vehicle operates in CD mode until the SOC of the battery 200 falls below a predetermined value.

[0033] Figure 2 is a flowchart showing an example of mode switching control performed by the ECU 300. This flowchart is repeated at predetermined intervals from the time the ignition switch 114 is turned ON until it is turned OFF. In step 10 (hereinafter, steps are abbreviated as "S"), it is determined whether the State of Charge (SOC) of the battery 200 is greater than or equal to the first SOC value α. The SOC may be calculated by the ECU 300 using a signal received from the monitoring unit 210. The SOC information calculated by the monitoring unit 210 may also be acquired by the ECU 300. If the SOC is greater than or equal to the first SOC value α, it is determined to be positive and the process proceeds to S11. The first SOC value α is, for example, a value obtained by adding a specified value to a value such that degradation is not accelerated due to a low (small) SOC of the battery 200. The first SOC value α may be set according to the specifications of the battery 200 or through experiments. In S11, the driving mode is set to CD mode. In CD mode, with the engine 103 stopped, power from the battery 200 is supplied to the MG102, and the MG102 is driven to perform electric propulsion. CD mode is a driving mode that consumes the power stored in the battery 200.

[0034] If the SOC is less than the first SOC value α, it is judged as negative in S10 and the process proceeds to S12. In S12, the driving mode is set to CS mode. In CS mode, the engine 103, MG101, and MG102 are controlled so that the SOC is maintained within a predetermined range, and so-called hybrid driving is performed.

[0035] Figure 3 is a flowchart showing an example of engine start control performed by the ECU300. This flowchart is repeated at predetermined intervals from the time the ignition switch 114 is turned ON until it is turned OFF. In S20, it is determined whether the driving mode is CD mode or not. If the driving mode is not CD mode, it is determined to be negative and the routine ends. If it is CD mode, it is determined to be positive and proceeds to S21.

[0036] In S21, it is determined whether flag F is 1 or not. Flag F is initialized to "0" when the ignition switch 114 is turned ON. If flag F is 0, it is determined to be negative and the process proceeds to S22.

[0037] In S22, it is determined whether the voltage VB of the battery 200 is less than or equal to the threshold Cv. In this embodiment, the monitoring unit 210 detects the voltage of the battery cells (cell voltage) as voltage VB. The voltage VB compared with the threshold Cv in S22 may be the cell voltage with the lowest voltage. Voltage VB may be the voltages of multiple battery cells connected in series, or it may be the total voltage of the battery 200. If voltage VB is greater than or equal to the threshold Cv, the process proceeds to S23; if voltage VB is less than the threshold Cv, the routine ends.

[0038] In S23, it is determined whether a predetermined time T has elapsed since the voltage VB fell below the threshold Cv. The predetermined time T may be, for example, 5 seconds, 10 seconds, or 1 minute. If the predetermined time T has not elapsed since the voltage VB fell below the threshold Cv, the determination is negative and the process returns to S22. If the predetermined time T has elapsed since the voltage VB fell below the threshold Cv, the determination is positive and the process proceeds to S23.

[0039] In S24, the engine 103 is started, and flag F is set to 1 before the current routine ends. When flag F is set to 1, the next time S21 is processed, it will be judged positively, and the processes of S22 to S24 will not be executed. The engine 103 is started by using the power of battery 200 to drive MG101, which rotates the crankshaft of the engine 103.

[0040] When engine 103 starts in S24, the warm-up operation of engine 103 begins. When the warm-up operation is complete, the ECU 300 terminates (stops) the operation of engine 103. The ECU 300 determines that the warm-up operation is complete when the exhaust gas purification catalyst CT reaches or exceeds its activation temperature. For example, the ECU 300 may determine that the warm-up operation is complete when the coolant temperature THW detected by a coolant temperature sensor (not shown) reaches or exceeds a predetermined value.

[0041] Figure 4 illustrates the relationship between the first SOC value α and the threshold Cv. In Figure 4, the vertical axis represents the SOC of battery 200, and the horizontal axis represents time. Figure 4 shows the progression of SOC when the vehicle is driven using battery 200, which is nearly fully charged after external charging is completed at time t0. When vehicle 1 stops engine 103 at time t0 and starts driving in CD mode by consuming power from battery 200, the SOC decreases. When vehicle 1 brakes, goes downhill, etc., regenerative braking by MG 102 charges battery 200. Therefore, the SOC decreases as battery 200 is charged and discharged.

[0042] During driving in CD mode, the SOC decreases, and at time t3, when the SOC falls below the first SOC value α, the driving mode switches to CS mode. In CS mode, engines 103, MG101, and MG102 are controlled to maintain the SOC within a predetermined range, resulting in hybrid driving.

[0043] SOC and voltage VB are correlated, with higher SOC values ​​resulting in higher voltage VB. If voltage VB corresponding to the first SOC value α is denoted as Co, then threshold Cv is set higher (larger) than Co. Therefore, at time t1, before time t3, voltage VB becomes less than or equal to threshold Cv. At time t1, voltage VB becomes less than or equal to threshold Cv, and this state continues for a predetermined time T until time t2, a positive determination is made in S23 (Figure 3), and engine 103 starts. It is preferable to set threshold Cv so that engine 103 is warmed up before time t3. This allows for a suitable reduction in engine 103 emissions when engine 103 is operated in CS mode.

[0044] According to this embodiment, when driving in CD mode, the engine 103 is started when the voltage VB remains below a threshold Cv for a predetermined time T. During battery 200 discharge, the voltage VB may briefly fall below the threshold Cv due to polarization, but the decrease in voltage VB due to polarization does not last for the predetermined time T. Therefore, when the voltage VB decreases, the effect of polarization can be eliminated and the engine 103 can be started, allowing the engine 103 to be started at an appropriate timing.

[0045] In this embodiment, the threshold Cv is set higher (larger) than Vo, which corresponds to the voltage VB corresponding to the first SOC value α. As a result, the engine 103 starts before switching from CD mode to CS mode. This makes it possible to complete the warm-up before driving in CS mode, and reduces emissions in CS mode.

[0046] In the above embodiment, the engine start control (Figure 3) process was initiated when the ignition switch 114 was turned ON. Polarization of the battery 200 due to charging and discharging increases when the State of Charge (SOC) is small (low). Therefore, the engine start control (Figure 3) process may be initiated when the SOC of the battery 200 falls below a second SOC value β (see Figure 4), which is greater than the first SOC value α. This allows the engine 103 to be started by effectively eliminating the effects of polarization at low SOC levels where polarization is large. Furthermore, the processing load on the ECU 300 can be reduced.

[0047] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0048] 1 Vehicle, 101, 102 Motor Generator (MG), 103 Engine, 104 Power Splitter, 105 Drive Wheels, 106 PCU, 108 SMR, 200 Battery, 210 Monitoring Unit, 300 Control Unit (ECU), CT Exhaust Catalytic Converter.

Claims

1. Internal combustion engines and A battery that can be charged externally using power supplied from an external power source, A rotating electric machine that generates driving force using the power stored in the aforementioned battery, A vehicle equipped with a control device, The control device is The vehicle can switch between a CD mode, in which it runs by consuming the power stored in the battery, and a CS mode, in which it runs while maintaining the battery's State of Charge (SOC) within a predetermined range. A vehicle that, while driving in the CD mode, starts the internal combustion engine when the battery voltage remains below a threshold for a predetermined period of time.

2. The control device is When the SOC falls below the first SOC value, the mode switches from CD mode to CS mode. The vehicle according to claim 1, wherein the threshold is set higher than the voltage of the battery corresponding to the first SOC value.

3. The vehicle according to claim 2, wherein the control device starts the internal combustion engine when the SOC is less than or equal to a second SOC value greater than the first SOC value, and the battery voltage remains below the threshold for a predetermined period of time while driving in CD mode.

4. The vehicle according to any one of claims 1 to 3, wherein the control device stops the operation of the internal combustion engine after the internal combustion engine has been started and the warm-up period of the internal combustion engine is complete.

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