JP2012249455A - Electric system in vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration in a battery caused by an overcharge.SOLUTION: An electric system in a vehicle comprises: a battery 150 storing power supplied from a power supply; and a system main relay 230 which connects the power supply and the battery 150 in their disconnected status when voltage of the battery 150 is lower than a threshold, and disconnects the power supply and the battery in their connected status when the voltage of the battery becomes higher than a predetermined value set higher than the threshold.

Description

  The present invention relates to an electric system of a vehicle, and more particularly to a technique for charging a power storage device.

  A hybrid vehicle, an electric vehicle, a fuel cell vehicle, and the like equipped with an electric motor used as a drive source are known. These vehicles are equipped with power storage devices such as a battery and a capacitor for storing electric power supplied to the electric motor. The power storage device stores electric power obtained by regenerative power generation and electric power generated by driving a generator by an engine. Some vehicles can charge power storage devices with electric power supplied from a power source outside the vehicle.

  When it is possible to charge the power storage device with electric power supplied from a power supply outside the vehicle, it is conceivable that charging is repeated without realizing that the power storage device is fully charged. When such charging is repeated, the power storage device can deteriorate quickly. Therefore, in order to prevent such charging, as described in JP-A-10-290534 (Patent Document 1), when the remaining capacity calculated from the battery current and the self-discharge amount is a predetermined value or more, It has been proposed to prohibit the charging operation.

JP-A-10-290534

  However, the battery current and the self-discharge amount greatly vary depending on factors such as the degree of deterioration of the battery and the temperature. Therefore, the remaining capacity may be calculated low even though the battery is actually fully charged. In such a case, the battery can be charged accidentally.

  The present invention has been made in view of the above-described problems, and an object thereof is to suppress deterioration of a power storage device due to overcharging.

  In one embodiment, an electric system of a vehicle stores a power storage device that stores power supplied from a power source, and the power source and the power storage device, and when the voltage of the power storage device is lower than a threshold value, And a connection device for connecting the two.

  According to this configuration, if the voltage of the power storage device is lower than the threshold value, the power storage device can be charged. If the voltage of the power storage device is equal to or higher than the threshold value, charging of the power storage device is limited. Since the voltage of the power storage device directly indicates the remaining capacity of the power storage device, by controlling charging based on the voltage of the power storage device, it is possible to accurately charge the power storage device even when the power storage device is fully charged. Can be suppressed. Therefore, deterioration of the power storage device due to overcharging can be suppressed.

  In another embodiment, the connection device shuts off the power supply and the power storage device when the voltage of the power storage device becomes higher than a predetermined value higher than the threshold after connecting the power supply and the charging device. To do.

  According to this configuration, the upper limit of the voltage that allows charging of the power storage device is set lower than the voltage at which charging of the power storage device is stopped. Therefore, overcharge of the power storage device can be further easily restricted.

  In yet another embodiment, the electrical system further includes a charging device that charges the power storage device with the power supplied from the power source. The connection device shuts off the power source and the power storage device after the charging device is connected to the power source, and connects the power storage device and the charging device when the voltage of the power storage device is lower than a threshold value.

  According to this configuration, charging of the power storage device can be limited by the connection device provided between the power storage device and the charging device.

In yet another embodiment, the power source is a power source external to the vehicle.
According to this configuration, the power storage device can be charged with electric power supplied from a power supply external to the vehicle.

It is a schematic block diagram which shows a hybrid vehicle. It is a figure which shows the alignment chart of a power split device. It is a figure (the 1) which shows the electric system of a hybrid vehicle. FIG. 2 is a second diagram illustrating an electrical system of a hybrid vehicle. It is a flowchart which shows the process which ECU performs. FIG. 6 is a third diagram illustrating the electrical system of the hybrid vehicle. FIG. 4 is a fourth diagram illustrating the electrical system of the hybrid vehicle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  Referring to FIG. 1, engine 100, first motor generator 110, second motor generator 120, power split mechanism 130, reduction gear 140, and battery 150 are mounted on the hybrid vehicle. In the following description, a hybrid vehicle will be described as an example, but an electric vehicle or a fuel cell vehicle may be used.

  Engine 100, first motor generator 110, second motor generator 120, and battery 150 are controlled by an ECU (Electronic Control Unit) 170. ECU 170 may be divided into a plurality of ECUs.

  This vehicle travels by driving force from at least one of engine 100 and second motor generator 120. That is, either one or both of engine 100 and second motor generator 120 is automatically selected as a drive source according to the operating state.

  For example, when the accelerator opening is small and the vehicle speed is low, the hybrid vehicle runs using only the second motor generator 120 as a drive source. In this case, engine 100 is stopped. However, the engine 100 may be driven for power generation or the like.

  Further, when the accelerator opening is large, the vehicle speed is high, or the remaining capacity (SOC: State Of Charge) of battery 150 is small, engine 100 is driven. In this case, the hybrid vehicle runs using only engine 100 or both engine 100 and second motor generator 120 as drive sources.

  The engine 100 may be used only for power generation without being used as a driving source for traveling. That is, the hybrid vehicle may be a series hybrid vehicle.

  The engine 100 is an internal combustion engine. As the fuel / air mixture burns in the combustion chamber, the crankshaft as the output shaft rotates. The exhaust gas discharged from the engine 100 is purified by the catalyst 102 and then discharged outside the vehicle. The catalyst 102 exhibits a purification action when the temperature is increased to a predetermined activation temperature. The catalyst 102 is warmed up by utilizing the heat of the exhaust gas. The catalyst 102 is, for example, a three-way catalyst.

  The air-fuel ratio of the engine 100 is detected from the exhaust gas by the air-fuel ratio sensor 104. Further, the temperature of the cooling water of engine 100 is detected by temperature sensor 106. The output of the air-fuel ratio sensor 104 and the output of the temperature sensor 106 are input to the ECU 170.

  Engine 100, first motor generator 110, and second motor generator 120 are connected via power split mechanism 130. The power generated by the engine 100 is divided into two paths by the power split mechanism 130. One is a path for driving the front wheels 160 via the speed reducer 140. The other is a path for driving the first motor generator 110 to generate power.

  First motor generator 110 is a three-phase AC rotating electric machine including a U-phase coil, a V-phase coil, and a W-phase coil. First motor generator 110 generates power using the power of engine 100 divided by power split mechanism 130. The electric power generated by the first motor generator 110 is selectively used according to the running state of the vehicle and the remaining capacity of the battery 150. For example, during normal traveling, the electric power generated by first motor generator 110 becomes electric power for driving second motor generator 120 as it is. On the other hand, when the SOC of battery 150 is lower than a predetermined value, the electric power generated by first motor generator 110 is converted from AC to DC by an inverter described later. Thereafter, the voltage is adjusted by a converter described later and stored in the battery 150.

  When first motor generator 110 is acting as a generator, first motor generator 110 generates negative torque. Here, the negative torque means a torque that becomes a load on engine 100. When first motor generator 110 is supplied with electric power and acts as a motor, first motor generator 110 generates positive torque. Here, the positive torque means a torque that does not become a load on the engine 100, that is, a torque that assists the rotation of the engine 100. The same applies to the second motor generator 120.

  Second motor generator 120 is a three-phase AC rotating electric machine including a U-phase coil, a V-phase coil, and a W-phase coil. Second motor generator 120 is driven by at least one of the electric power stored in battery 150 and the electric power generated by first motor generator 110.

  The driving force of the second motor generator 120 is transmitted to the front wheels 160 via the speed reducer 140. As a result, the second motor generator 120 assists the engine 100 or causes the vehicle to travel by the driving force from the second motor generator 120. The rear wheels may be driven instead of or in addition to the front wheels 160.

  During regenerative braking of the hybrid vehicle, the second motor generator 120 is driven by the front wheels 160 via the speed reducer 140, and the second motor generator 120 operates as a generator. Accordingly, second motor generator 120 operates as a regenerative brake that converts braking energy into electric power. The electric power generated by second motor generator 120 is stored in battery 150.

  Power split device 130 includes a planetary gear including a sun gear, a pinion gear, a carrier, and a ring gear. The pinion gear engages with the sun gear and the ring gear. The carrier supports the pinion gear so that it can rotate. The sun gear is connected to the rotation shaft of first motor generator 110. The carrier is connected to the crankshaft of engine 100. The ring gear is connected to the rotation shaft of second motor generator 120 and speed reducer 140.

  The engine 100, the first motor generator 110, and the second motor generator 120 are connected via a power split mechanism 130 that is a planetary gear, so that the rotational speeds of the engine 100, the first motor generator 110, and the second motor generator 120 are increased. As shown in FIG. 3, the relationship is connected by a straight line in the alignment chart.

  Returning to FIG. 1, the battery 150 is an assembled battery configured by further connecting a plurality of battery modules in which a plurality of battery cells are integrated in series. The voltage of battery 150 is detected by voltage sensor 152, and a signal representing the detected voltage is input to ECU 170. The battery 150 is charged with electric power supplied from a power source external to the vehicle in addition to the first motor generator 110 and the second motor generator 120. A capacitor may be used instead of or in addition to the battery 150.

  With reference to FIG. 3, the electric system of the hybrid vehicle will be further described. The hybrid vehicle is provided with a converter 200, a first inverter 210, a second inverter 220, a system main relay (SMR) 230, a charger 240, and an inlet 250.

  Converter 200 includes a reactor, two npn transistors, and two diodes. One end of the reactor is connected to the positive electrode side of each battery, and the other end is connected to the connection point of the two npn transistors.

  Two npn-type transistors are connected in series. The npn transistor is controlled by the ECU 170. A diode is connected between the collector and emitter of each npn transistor so that a current flows from the emitter side to the collector side.

  For example, an IGBT (Insulated Gate Bipolar Transistor) can be used as the npn transistor. Instead of the npn type transistor, a power switching element such as a power MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) can be used.

  When the electric power discharged from the battery 150 is supplied to the first motor generator 110 or the second motor generator 120, the voltage is boosted by the converter 200. Conversely, when charging the battery 150 with the electric power generated by the first motor generator 110 or the second motor generator 120, the voltage is stepped down by the converter 200.

  System voltage VH between converter 200 and each inverter is detected by voltage sensor 180. The detection result of voltage sensor 180 is transmitted to ECU 170.

  First inverter 210 includes a U-phase arm, a V-phase arm, and a W-phase arm. The U-phase arm, V-phase arm and W-phase arm are connected in parallel. Each of the U-phase arm, the V-phase arm, and the W-phase arm has two npn transistors connected in series. Between the collector and emitter of each npn-type transistor, a diode for passing a current from the emitter side to the collector side is connected. A connection point of each npn transistor in each arm is connected to an end portion different from neutral point 112 of each coil of first motor generator 110.

  First inverter 210 converts a direct current supplied from battery 150 into an alternating current and supplies the alternating current to first motor generator 110. The first inverter 210 converts the alternating current generated by the first motor generator 110 into a direct current.

  Second inverter 220 includes a U-phase arm, a V-phase arm, and a W-phase arm. The U-phase arm, V-phase arm and W-phase arm are connected in parallel. Each of the U-phase arm, the V-phase arm, and the W-phase arm has two npn transistors connected in series. Between the collector and emitter of each npn-type transistor, a diode for passing a current from the emitter side to the collector side is connected. A connection point of each npn transistor in each arm is connected to an end portion different from neutral point 122 of each coil of second motor generator 120.

  Second inverter 220 converts a direct current supplied from battery 150 into an alternating current, and supplies the alternating current to second motor generator 120. Second inverter 220 converts the alternating current generated by second motor generator 120 into a direct current.

  Converter 200, first inverter 210, and second inverter 220 are controlled by ECU 170.

  System main relay 230 is provided between battery 150 and charger 240. The system main relay 230 is a relay that switches between a state where the battery 150 and the electric system are connected and a state where the battery 150 is disconnected. When system main relay 230 is in an open state, battery 150 is disconnected from the electrical system. When system main relay 230 is in a closed state, battery 150 is connected to the electrical system.

  That is, when system main relay 230 is in an open state, battery 150 is electrically disconnected from charger 240 and an external power source 402 described later. When system main relay 230 is in a closed state, battery 150 is electrically connected to charger 240, external power supply 402, and the like. The state of system main relay 230 is controlled by ECU 170. The control mode of the system main relay 230 will be described in detail later.

  Charger 240 is connected between battery 150 and converter 200. As shown in FIG. 4, charger 240 includes an AC / DC conversion circuit 242, a DC / AC conversion circuit 244, an insulation transformer 246, and a rectifier circuit 248.

  The AC / DC conversion circuit 242 is a single-phase bridge circuit. The AC / DC conversion circuit 242 converts AC power into DC power based on a drive signal from the ECU 170. The AC / DC conversion circuit 242 also functions as a boost chopper circuit that boosts the voltage by using a coil as a reactor.

  The DC / AC conversion circuit 244 is composed of a single-phase bridge circuit. The DC / AC conversion circuit 244 converts the DC power into high-frequency AC power based on the drive signal from the ECU 170 and outputs it to the isolation transformer 246.

  Insulation transformer 246 includes a core made of a magnetic material, and a primary coil and a secondary coil wound around the core. The primary coil and the secondary coil are electrically insulated and connected to the DC / AC conversion circuit 244 and the rectification circuit 248, respectively. Insulation transformer 246 converts high-frequency AC power received from DC / AC conversion circuit 244 into a voltage level corresponding to the turn ratio of the primary coil and the secondary coil, and outputs the voltage level to rectifier circuit 248. The rectifier circuit 248 rectifies AC power output from the insulating transformer 246 into DC power.

  A voltage (voltage between terminals of the smoothing capacitor) between AC / DC conversion circuit 242 and DC / AC conversion circuit 244 is detected by voltage sensor 182, and a signal representing the detection result is input to ECU 170. The output current of charger 240 is detected by current sensor 184, and a signal representing the detection result is input to ECU 170. Further, the temperature of charger 240 is detected by temperature sensor 186, and a signal representing the detection result is input to ECU 170.

  Inlet 250 is provided, for example, on the side of the hybrid vehicle. A connector 310 of a charging cable 300 that connects the hybrid vehicle and the external power source 402 is connected to the inlet 250.

  Plug 320 of charging cable 300 is connected to an outlet 400 provided in the house. AC power is supplied to the outlet 400 from a power supply 402 outside the hybrid vehicle.

  In a state where the hybrid vehicle and the external power source 402 are connected by the charging cable 300, the power supplied from the external power source 402 is charged to the battery 150. When battery 150 is charged, system main relay 230 is closed.

  With reference to FIG. 5, a process executed by ECU 170 regarding charging of battery 150 will be described. The processing described below is executed by software, hardware, or cooperation between software and hardware. The process described below is executed, for example, in a state where the vehicle is stopped and the ignition switch (or start switch) is turned off.

  In step (hereinafter step is abbreviated as S) 100, it is determined whether or not external charging connector 310 is connected to the vehicle. For example, it is determined whether or not the external charging connector 310 is connected to the vehicle using a switch configured to be turned on when the external charging connector 310 is connected to the vehicle. The method for determining whether or not the external charging connector 310 is connected to the vehicle is not limited to this.

  When connector 310 for external charging is connected to the vehicle (YES in S100), the system main relay 230 is kept open in S102. In S104, it is determined whether or not the voltage of battery 150 is lower than the first threshold value. The first threshold value is a value determined in advance by the developer.

  It may be determined whether or not the voltage of the battery 150 is lower than the first threshold value when other conditions predetermined as conditions necessary for starting charging are satisfied. The condition necessary for starting charging may include a condition that the voltage of the battery 150 is lower than the first threshold value.

  If the voltage of battery 150 is lower than the first threshold (YES in S104), system main relay 230 is closed in S106. Further, in S108, charging of battery 150 is started.

  Thereafter, in S110, it is determined whether or not the voltage of battery 150 is higher than the second threshold value. The second threshold value is a predetermined value that is set higher than the first threshold value. The second threshold value is determined in advance by the developer. If the voltage of battery 150 is higher than the second threshold value (YES at S110), it is determined that battery 150 is fully charged, charging is stopped at S112, and system main relay 230 at S114. Is opened.

  On the other hand, even if external charging connector 310 is connected to the vehicle (YES in S100), if the voltage of battery 150 is equal to or higher than the first threshold (NO in S104), system main relay 230 is closed. The process ends without

  As described above, according to the present embodiment, battery 150 can be charged if the voltage of battery 150 is lower than the first threshold value. If the voltage of battery 150 is equal to or higher than the threshold value, charging of battery 150 is restricted. Since the voltage of the battery 150 directly indicates the remaining capacity of the battery 150, by controlling charging based on the voltage of the battery 150, it is possible to accurately charge the battery 150 even when the battery 150 is fully charged. Can be suppressed. Therefore, deterioration of the battery 150 due to overcharging can be suppressed.

  As shown in FIG. 6, another relay 232 may be provided between the charger 240 and the system main relay 230, and the relay 232 may be controlled instead of or in addition to the system main relay 230. That is, the relay 232 may be opened and the relay 232 may be closed when the voltage of the battery 150 is lower than the first threshold value. In this case, as shown in FIG. 7, a charger 240 may be connected between the battery 150 and the system main relay 230. That is, the position of the relay 232 may be anywhere between the battery 150 and the external power source 402.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  100 Engine, 102 Catalyst, 110 First motor generator, 120 Second motor generator, 130 Power split mechanism, 140 Reducer, 150 Battery, 152 Voltage sensor, 160 Front wheel, 170 ECU, 230 System main relay, 232 relay, 240 Charging 242 AC / DC conversion circuit, 244 DC / AC conversion circuit, 246 isolation transformer, 248 rectifier circuit, 250 inlet, 300 charging cable, 310 connector, 320 plug, 400 outlet, 402 power supply.

Claims (4)

A vehicle electrical system,
A power storage device for storing electric power supplied from a power source;
An electrical system comprising: a connection device that cuts off the power source and the power storage device, and connects the power source and the power storage device when a voltage of the power storage device is lower than a threshold value.   The connecting device connects the power source and the power storage device when the voltage of the power storage device becomes higher than a predetermined value higher than the threshold value after connecting the power source and the charging device. The electrical system of claim 1, wherein the electrical system is shut off. A charging device for charging the power storage device with the power supplied from the power source;
The connection device shuts off the power source and the power storage device after the charging device is connected to the power source, and when the voltage of the power storage device is lower than the threshold value, the power storage device and the power storage device The electrical system according to claim 1, wherein the electrical system is connected to a charging device.   The electric system according to claim 1, wherein the power source is a power source external to the vehicle.

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