Vehicle

Abstract

The invention relates to a vehicle. A starting method of the present invention appropriately starts an internal combustion engine by eliminating the effect of polarization when the voltage of a battery is reduced. The vehicle is a plug-in hybrid vehicle provided with a battery that can be externally charged. The vehicle travels in the CD mode when the SOC of the battery is equal to or greater than the first SOC value [alpha], and travels in the CS mode when the SOC is less than the first SOC value [alpha]. The ECU starts the engine when the state in which the battery voltage TB is equal to or less than the threshold value Cv continues for a predetermined time T. The threshold value Cv is set to be higher than Co corresponding to the voltage TB corresponding to the first SOC value alpha.

Description

Technical Field

[0001] This invention relates to a vehicle. Background Technology

[0002] Japanese Patent Application Publication No. 2013-237298 (Patent Document 1) discloses a plug-in hybrid electric vehicle. In the hybrid electric vehicle of Patent Document 1, if the battery voltage falls below a predetermined threshold during EV driving, the engine is started to perform HV driving.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2013-237298 Summary of the Invention

[0004] Polarization occurs during battery charging and discharging. This polarization causes a decrease in battery voltage. Polarization is particularly pronounced at high charging / discharging rates and when the battery's state of charge (SOC) is low. Patent Document 1 does not consider the voltage drop caused by polarization. Therefore, even if the battery voltage drops below a threshold value in a very short time due to polarization, the engine may still start.

[0005] The purpose of this invention is to properly start the internal combustion engine by eliminating the effects of polarization when the battery voltage drops.

[0006] The vehicle of the present invention includes: an internal combustion engine; a battery capable of being externally charged by power supplied from an external power source; a rotary motor that uses the power stored in the battery to generate driving force; and a control device. The control device is capable of switching between a discharge (Charge Depleting: CD) mode, in which the vehicle operates by consuming the power stored in the battery, and a charge sustaining (Charge Sustaining: CS) mode, in which the vehicle operates by maintaining the battery's state of charge (SOC) within a specified range. During operation in CD mode, if the battery voltage remains below a threshold for a specified period of time, the internal combustion engine is started.

[0007] According to this structure, during driving in CD mode, the internal combustion engine is started when the battery voltage remains below a threshold for a specified period of time. During battery discharge, the battery voltage may briefly fall below the threshold due to polarization. The voltage drop caused by polarization does not last for the specified time. Therefore, when the battery voltage drops, the effects of polarization can be eliminated, allowing the internal combustion engine to start.

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

[0009] According to this structure, the threshold is set to be higher than the battery voltage corresponding to the first SOC value when switching from CD mode to CS mode. The internal combustion engine starts before switching to CS mode. When driving in CS mode, for example, warm-up has been completed, which can reduce emissions, etc., that occur in CS mode.

[0010] Preferably, the control device can start the internal combustion engine when the battery's SOC is below a second SOC value that is greater than the first SOC value and during driving in CD mode, and the battery voltage remains below a threshold for a specified period of time.

[0011] According to this structure, the effects of polarization can be appropriately eliminated to start the internal combustion engine in a low SOC environment where battery polarization is increased.

[0012] Preferably, the control device can stop the operation of the internal combustion engine after the internal combustion engine is started and after the warm-up of the internal combustion engine has ended.

[0013] According to this structure, the internal combustion engine stops once the warm-up process is complete, thus appropriately reducing emissions in CS mode.

[0014] Invention Effects

[0015] According to the present invention, when the battery voltage drops, the effects of polarization can be eliminated and the internal combustion engine can be started appropriately. Attached Figure Description

[0016] Figure 1 This is a diagram that roughly illustrates the overall structure of the vehicle involved in this embodiment.

[0017] Figure 2 This is a flowchart illustrating an example of mode switching control performed by ECU300.

[0018] Figure 3 This is a flowchart illustrating an example of engine start control performed by ECU300.

[0019] Figure 4 This is a graph illustrating the relationship between the first SOC value α and the threshold Cv. Detailed Implementation

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

[0021] Figure 1 This is a diagram that roughly illustrates the overall structure of the vehicle 1 according to this embodiment. Figure 1 The diagram shows a situation where vehicle 1 is electrically connected to charging device 5 via charging cable 3, and vehicle 1 is electrically connected to charging device 9 via charging cable 7.

[0022] Charging device 5 is, for example, a common charger found in a typical household. Charging device 5 outputs AC power from the system power supply, which is an external power source, to vehicle 1. Charging device 9 is a fast charger that converts the AC power from the system power supply, which is an external power source, into DC power and outputs it to vehicle 1. Furthermore, when externally charging vehicle 1, vehicle 1 is electrically connected to either charging device 5 or charging device 9 via a charging cable.

[0023] Vehicle 1 is a plug-in hybrid electric vehicle. Vehicle 1 includes: an electric generator (MG) 101, MG 102, an engine 103, a power splitter 104, drive wheels 105, a power control unit (PCU) 106, a system main relay (SMR) 108, a battery 200, charging relays 110 and 120, a charger 111, charging interfaces 112 and 122, and an electronic control unit (ECU) 300.

[0024] MG101 and MG102 are, for example, three-phase AC rotary motors with permanent magnets embedded in the rotors (not shown). MG101 is connected to the crankshaft of engine 103 via power splitting device 104. MG101 uses power from battery 200 to rotate the crankshaft of engine 103 when engine 103 is started. Furthermore, MG101 can also generate electricity using the power from engine 103. The AC power generated by MG101 is converted to DC power by PCU 106 and charged to battery 200. Additionally, the AC power generated by MG101 is sometimes also supplied to MG102.

[0025] MG102 uses at least one of the power from battery 200 and the power generated by MG101 to rotate the drive shaft. Furthermore, MG102 can also generate electricity through regenerative braking. The AC power generated by MG102 is converted to DC power by PCU106 and charged to battery 200.

[0026] Engine 103 is an internal combustion engine such as a gasoline engine or a diesel engine, which generates power to propel vehicle 1 based on control signals from ECU 300. An exhaust purification catalyst CT is installed in the exhaust passage EX of engine 103. In the case of a gasoline engine, the exhaust purification catalyst CT can be a three-way catalytic converter; in the case of a diesel engine, it can be a NOx purification catalyst.

[0027] The power splitting device 104 is, for example, a planetary gear mechanism, which splits the power generated by the engine 103 into power transmitted to the drive wheel 105 and power transmitted to the MG101.

[0028] PCU106 converts the DC power stored in battery 200 into AC power and supplies it to MG101 and 102 according to the control signal from ECU300. PCU106 also converts the AC power generated by MG101 and 102 into DC power and supplies it to battery 200.

[0029] SMR108 is electrically connected to the power line connecting PCU106 and battery 200. SMR108 switches the power supply and disconnection between PCU106 and battery 200 according to the control signal from ECU300.

[0030] Battery 200 is a rechargeable battery capable of being charged and discharged. Battery 200 can be a lithium-ion rechargeable battery, nickel-metal hydride battery, or other rechargeable battery. Battery 200 is a battery pack consisting of multiple individual cells (battery units) connected in series, for example. Battery 200 supplies electricity used to generate driving force for vehicle 1 to PCU106. Furthermore, battery 200 stores the electricity generated by MG101.

[0031] 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 input to and output to 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.

[0032] The charging relay 110 is electrically connected to the power line connecting the battery 200 and the charger 111. The charging relay 110 switches the supply and disconnection of power between the battery 200 and the charger 111 according to the control signal from the ECU 300.

[0033] The charger 111 is configured, for example, to include an AC / DC converter, which converts the AC power supplied from the charging device 5 via the charging cable 3 and the charging interface 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 device 5 (normal charging), the charging relay 110 is closed, and the power supplied to the vehicle 1 is controlled in the charger 111.

[0034] Connected via charging cable 7, charging interface 122 receives DC power supplied from charging device 9. Charging relay 120 is electrically connected to the power line connecting battery 200 and charging interface 122. Charging relay 120 switches the power supply and disconnection between battery 200 and charging interface 122 according to control signals from ECU 300. When external charging (fast charging) of vehicle 1 (battery 200) is performed using power supplied from charging device 9, charging relay 120 is closed, and the power supplied to vehicle 1 is controlled in the controller of charging device 9 (fast charger).

[0035] The ECU 300 is configured to include a Central Processing Unit (CPU) 301, a memory 302, and a buffer (not shown). The ECU 300 controls various devices to bring the vehicle 1 to a desired state based on inputs from the monitoring unit 210 or various sensors (not shown) such as throttle opening signals, vehicle speed signals, etc., as well as mappings and programs stored in the memory. One of the controls performed by the ECU 300 is "mode switching control".

[0036] Vehicle 1 operates in either CD mode or CS mode. CD mode is a driving mode that continues electric driving (EV driving) of vehicle 1 using the power of battery 200 as much as possible while the engine 103 is stopped, consuming the power stored in battery 200. CS mode is a driving mode that uses engine 103, MG101, and MG102 to maintain the state of charge (SOC) of battery 200 within a specified range. In this embodiment, vehicle 1 operates in CD mode until the SOC of battery 200 falls below the specified value.

[0037] Figure 2This is a flowchart illustrating an example of mode switching control performed by the ECU 300. In this flowchart, processing is repeated repeatedly for each predetermined period from the moment the ignition switch 114 is turned on until it is turned off. In step (hereinafter, step S) 10, it is determined whether the SOC of the battery 200 is greater than or equal to a first SOC value α. The SOC can be calculated in the ECU 300 using a signal received from the monitoring unit 210. Alternatively, the ECU 300 can obtain the SOC information calculated in the monitoring unit 210. If the SOC is greater than or equal to the first SOC value α, a positive determination is obtained, and the process proceeds to S11. The first SOC value α is, for example, a value obtained by adding a predetermined value to a value where the SOC of the battery 200 is low (small) without promoting degradation. The first SOC value α can be set according to the specifications of the battery 200 or experimental settings. In S11, the driving mode is set to CD mode. In CD mode, with engine 103 stopped, power from battery 200 is supplied to MG102, which is then driven for electric travel. CD mode is a driving mode that consumes the power stored in battery 200.

[0038] When the State of Charge (SOC) is less than the first SOC value α, the decision is rejected in S10 and proceeds to S12. In S12, the driving mode is set to CS mode. In CS mode, the engines 103, MG101, and MG102 are controlled to maintain the SOC within a specified range, thus performing so-called hybrid driving.

[0039] Figure 3 This is a flowchart illustrating an example of engine start control executed by ECU 300. In this flowchart, processing is repeated repeatedly at each predetermined interval from the moment the ignition switch 114 is turned on until it is turned off. In S20, it is determined whether the driving mode is CD mode. If the driving mode is not CD mode, the determination is negative and the current routine ends. If the driving mode is CD mode, a positive determination is obtained and the process proceeds to S21.

[0040] In S21, it is determined whether the flag F is 1. When the ignition switch 114 is turned on, the flag F is initialized and set to "0". When the flag F is 0, a negative determination is obtained and the process proceeds to S22.

[0041] In step S22, it is determined whether the voltage VB of battery 200 is below 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 can be the lowest voltage cell voltage. Voltage VB can be the voltage of multiple battery cells connected in series, or it can be the total voltage of battery 200. When voltage VB is above the threshold Cv, the process proceeds to step S23; when voltage VB is below the threshold Cv, the current routine ends.

[0042] 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 can 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, a negative determination is made, and the process returns to S22. If the predetermined time T has elapsed since the voltage VB fell below the threshold Cv, a positive determination is made, and the process proceeds to S23.

[0043] In S24, the engine 103 is started, and the flag F is set to 1, then the current routine ends. If the flag F is set to 1, it will be affirmatively determined in the next processing of S21, and the processing of S22 to S24 will not be executed. During the starting of the engine 103, the power of the battery 200 is used to drive the MG101, causing the crankshaft of the engine 103 to rotate.

[0044] If engine 103 starts in S24, engine warm-up operation begins. If warm-up operation ends, ECU 300 stops (stops) engine 103. ECU 300 determines that warm-up operation is complete when the exhaust gas purification catalyst CT reaches or exceeds its activation temperature. For example, when the coolant temperature THW detected by a coolant temperature sensor (not shown) reaches or exceeds a specified value, warm-up operation can be determined to be complete.

[0045] Figure 4 This is a graph illustrating the relationship between the first SOC value α and the threshold Cv. Figure 4 In the diagram, the vertical axis represents the SOC of the battery 200, and the horizontal axis represents time. Figure 4 This indicates the shift in State of Charge (SOC) when driving with the battery 200, which is nearly fully charged after charging has ended at time t0. If vehicle 1 stops the engine 103 at time t0 and starts driving in CD mode while consuming the power of the battery 200, the SOC decreases. The battery 200 is charged via regenerative braking through MG102 when vehicle 1 brakes, goes downhill, etc. Therefore, the SOC decreases simultaneously with the charging and discharging of the battery 200.

[0046] If the State of Charge (SOC) decreases due to driving in CD mode, and at time t3, 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 specified range, thus achieving hybrid driving.

[0047] SOC is related to voltage VB; the larger the SOC, the higher the voltage VB. If the voltage VB corresponding to the first SOC value α is set to Co, then the threshold Cv is set to be higher than (greater than) Co. Therefore, at time t1 before time t3, the voltage VB is below the threshold Cv. If at time t1, the voltage VB is below the threshold Cv, and this state lasts for a specified time T, then at S23 ( Figure 3 The engine 103 is started when the condition is confirmed. Preferably, the threshold Cv is set to complete the warm-up of the engine 103 before time t3. Therefore, when the engine 103 is running in CS mode, the emissions of the engine 103 can be appropriately reduced.

[0048] According to this embodiment, during driving in CD mode, when the voltage VB remains below the threshold Cv for a predetermined time T, the engine 103 is started. During battery 200 discharge, the internal voltage VB may sometimes fall below the threshold Cv for a short time due to polarization, but this 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 at an appropriate time.

[0049] According to this embodiment, the threshold Cv is set to be higher (greater) than Vo, which corresponds to the voltage VB corresponding to the first SOC value α. Therefore, the engine 103 starts before switching from CD mode to CS mode. Warm-up can be completed before driving in CS mode, thereby reducing emissions in CS mode.

[0050] In the above embodiment, engine start control begins when the ignition switch 114 is turned on. Figure 3 The polarization caused by charging and discharging of battery 200 increases when the SOC is low. Therefore, it can also be set that the SOC of battery 200 becomes a second SOC value β (reference) that is greater than the first SOC value α. Figure 4 When the following conditions are met, start engine start control. Figure 3 This allows for the proper elimination of the effects of polarization when the state of charge (SOC) is low, resulting in increased polarization, thus enabling the engine 103 to start. Furthermore, it reduces the processing load on the ECU 300.

[0051] It should be considered that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention is set forth in the claims, not in the description of the above embodiments, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0052] Symbol Explanation

[0053] 1-Vehicle, 101, 102-Electric Generator (MG), 103-Engine, 104-Power Split Unit, 105-Drive Wheel, 106-PCU, 108-SMR, 200-Battery, 210-Monitoring Unit, 300-Control Unit (ECU), CT-Exhaust Catalyst.

Claims

1. A vehicle characterized by comprising: Possessing: an internal combustion engine; a battery that is externally chargeable by supply electric power supplied from an external power source; a rotating electric machine that generates a driving force using electric power accumulated in the battery; and a control device, the control device performs the following processing: a CD mode in which the vehicle travels by consuming electric power accumulated in the battery and a CS mode in which the vehicle travels while maintaining a state in which a state of charge (SOC) of the battery is within a prescribed range are switchable; when a state in which a voltage of the battery is below a threshold value continues for a prescribed time during traveling in the CD mode, the internal combustion engine is started.

2. The vehicle according to claim 1, wherein the control device performs the following processing: if the SOC becomes a first SOC value or less, the CD mode is switched to the CS mode, the threshold value is set to be higher than a 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 a state in which the voltage of the battery is below the threshold value continues for the prescribed time during traveling in the CD mode while the SOC is a second SOC value that is greater than the first SOC value and is equal to or less than the first SOC value.

4. The vehicle according to any one of claims 1 to 3, wherein the control device stops operation of the internal combustion engine when the internal combustion engine is started and when a warm-up of the internal combustion engine ends. ​

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