Control device, control system, and control method for hybrid vehicles

Abstract

To provide a technique that can reduce a possibility that an engine is driven at high output, in a hybrid vehicle.SOLUTION: A control device of a hybrid vehicle is mounted on the hybrid vehicle equipped with an engine, an electric motor generator and a battery for supplying electric power to the electric motor generator. The hybrid vehicle has an EV running mode in which the vehicle runs using the electric motor generator as a driving force source while stopping the engine, and an HV running mode in which the vehicle runs using the engine and the electric motor generator as driving force sources. The control device has: a calculating part that calculates, as an electric power threshold, an electric power value larger than an output electric power value of the battery at the time when polarization occurs in the battery, when the hybrid vehicle is running in the EV running mode; and an operation control part that when a required electric power value from the hybrid vehicle is larger than the electric power threshold value, starts the engine, and switches the running mode of the hybrid vehicle from the EV running mode to the HV running mode.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a control device, a control system, and a control method for a hybrid vehicle.

Background Art

[0002] Conventionally, in a control device for a hybrid vehicle including an engine, a motor generator, and a battery that supplies power to the motor generator, a technique for starting the engine according to the output voltage value of the battery is known (Patent Document 1). In this technique, the engine is started when the output voltage value of the battery is lower than a predetermined reference voltage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technique, the engine is started when it is detected that the output voltage value of the battery has decreased. Therefore, in order to avoid excessive decrease in the output voltage value of the battery at the time of starting the engine, control for limiting the upper limit value of the output power value of the battery may be executed. When control for limiting the upper limit value of the output power value of the battery is executed, the engine may be driven at high output at the time of starting the engine. When the engine is driven at high output, the amount of exhaust gas emissions may increase and the drivability may deteriorate.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to a first embodiment of the present disclosure, a control device for a hybrid vehicle is provided. The control device is mounted on a hybrid vehicle comprising an engine, an electric generator, and a battery that supplies power to the electric generator, wherein the hybrid vehicle has an EV driving mode in which it runs using the electric generator as a driving force source with the engine stopped, and an HV driving mode in which it runs using the engine and the electric generator as driving force sources, and the control device comprises a calculation unit that calculates a power threshold value greater than the output power value of the battery when polarization occurs in the battery when the hybrid vehicle is running in the EV driving mode, and an operation control unit that starts the engine and switches the driving mode of the hybrid vehicle from the EV driving mode to the HV driving mode when the power value requested from the hybrid vehicle is greater than the power threshold value. According to this embodiment, the control device can calculate a power threshold value that can detect signs of polarization and start the engine when the power value requested from the hybrid vehicle is greater than the power threshold value. As a result, the engine can be started in advance before control is performed to limit the upper limit of the battery's output power value, thereby reducing the possibility of the engine being driven at high output. Therefore, it is possible to reduce the possibility of increased exhaust emissions or deterioration of drivability. (2) In the above configuration, the calculation unit may include: a first calculation unit that calculates an inflection point in a discharge curve showing the relationship between the charge level of the battery and the output voltage value of the battery when discharging power from the battery as a voltage threshold; a second calculation unit that calculates an estimated value of the open-circuit voltage value of the battery using the measured value of the output current value of the battery, the measured value of the output voltage value of the battery, and the resistance value of the battery; a third calculation unit that calculates a current threshold using the voltage threshold, the estimated value of the open-circuit voltage value, and the resistance value of the battery; and a fourth calculation unit that calculates the power threshold by multiplying the current threshold and the voltage threshold. According to this configuration, the power threshold can be easily calculated using the voltage threshold and the current threshold. (3) A second embodiment of the present disclosure provides a control system for a hybrid vehicle. The control system, mounted on a hybrid vehicle comprising an engine, an electric generator, and a battery that supplies power to the electric generator, comprises the control device described in the above embodiment, a current value measuring unit that measures the actual output current value of the battery, a voltage value measuring unit that measures the actual output voltage value of the battery, and a resistance value calculating unit that calculates the resistance value of the battery. In this embodiment, the control device can calculate a power threshold using the data acquired by the current value measuring unit, the voltage value measuring unit, and the resistance value calculating unit. (4) A third embodiment of the present disclosure provides a method for controlling a hybrid vehicle. The method for controlling a hybrid vehicle comprising an engine, an electric generator, and a battery that supplies power to the electric generator, wherein the hybrid vehicle has an EV driving mode in which it runs using the electric generator as a driving force source with the engine stopped, and an HV driving mode in which it runs using the engine and the electric generator as driving force sources, and the control method comprises a calculation step of calculating a power threshold value that is greater than the output power value of the battery when polarization occurs in the battery when the hybrid vehicle is running in the EV driving mode, and an operation control step of starting the engine and switching the driving mode of the hybrid vehicle from the EV driving mode to the HV driving mode when the power value requested from the hybrid vehicle is greater than the power threshold value. Therefore, it is possible to reduce the possibility of increased exhaust emissions or deterioration of drivability. This disclosure can be implemented in various forms other than the control device, control system, and control method for the hybrid vehicle described above. For example, it can be implemented in the form of a method for manufacturing the control device and control system for the hybrid vehicle, a computer program for implementing a control method for the hybrid vehicle, and a non-temporary recording medium on which the computer program is stored. [Brief explanation of the drawing]

[0007] [Figure 1] A diagram illustrating the general configuration of a hybrid vehicle. [Figure 2] A block diagram showing the schematic configuration of the control system. [Figure 3] A flowchart illustrating the control method for hybrid vehicles. [Figure 4] A schematic diagram illustrating an example of a voltage transition map. [Figure 5] A conceptual diagram illustrating the method for estimating open-circuit voltage values ​​and calculating power thresholds. [Modes for carrying out the invention]

[0008] A. Embodiments: Figure 1 is a diagram illustrating the schematic configuration of the hybrid vehicle 1. The hybrid vehicle 1 is an automobile that runs on the driving force of at least one of the first motor 301, which acts as an electric generator, and the engine 100. In other words, the hybrid vehicle 1 has an EV driving mode in which it runs using the first motor 301 as the driving force source with the engine 100 stopped, and an HV driving mode in which it runs using the engine 100 and the first motor 301 as driving force sources. In this embodiment, the hybrid vehicle 1 is a plug-in hybrid (PHEV) vehicle in which the main battery 310 that supplies power to the first motor 301 can be charged by power from an external power source 19. Note that the hybrid vehicle 1 is not limited to a plug-in hybrid vehicle, and may be a hybrid vehicle that does not have the mechanisms 11, 13 for charging the main battery 310 by power from an external power source 19.

[0009] The hybrid vehicle 1 comprises an engine 100, a power split mechanism 200, a first motor 301 and a second motor 302 acting as an electric generator, a main battery 310, a charger 11, a vehicle-side connector 13, an inverter 330, and a first converter 320.

[0010] Engine 100 is an internal combustion engine that uses fuel gas such as gasoline as fuel. Engine 100 is the first power source of the hybrid vehicle 1. The power generated from engine 100 is transmitted to the drive wheels 12 via the reduction gear 14.

[0011] The power split mechanism 200 is a planetary gear mechanism including a sun gear, pinion gear, carrier, and ring gear. The power split mechanism 200 distributes the driving force generated from the engine 100 to the output shaft 212 and the first motor 301.

[0012] The first motor 301 generates driving force using at least one of the power stored in the main battery 310 and the power generated by the second motor 302. The first motor 301 is the second driving force source of the hybrid vehicle 1. The driving force generated by the first motor 301 is transmitted to the drive wheels 12 via the reduction gear 14. When the hybrid vehicle 1 is braking, etc., the first motor 301 is driven by the drive wheels 12 via the reduction gear 14. As a result, the first motor 301 performs regenerative power generation.

[0013] The second motor 302 generates electricity using the driving force of the engine 100, which has been split by the power split mechanism 200. The electricity generated by the second motor 302 using the driving force of the engine 100 is used to charge the main battery 310 or to drive the first motor 301.

[0014] The main battery 310 drives the first motor 301 and also supplies power to the auxiliary battery 510, which will be described later. The main battery 310 is a rechargeable battery that can be repeatedly charged and discharged. The main battery 310 is, for example, a lithium-ion battery. The output voltage of the main battery 310 is, for example, 100 volts or more.

[0015] The charger 11 converts the alternating current supplied from an external power source 19, such as a commercial power supply, into a direct current and outputs it to the main battery 310. The charger 11 controls the amount of power charged to the main battery 310 according to the control signal from the HV-ECU 404, which will be described later.

[0016] The vehicle-side connector 13 is a connecting member for connecting the charger 11 to an external power source 19. The vehicle-side connector 13 is connected to the charger 11 and is configured to be connectable to a power-side connector 15 that is connected to the external power source 19.

[0017] The inverter 330 controls the current by converting the DC current from the main battery 310 to the AC current from the first motor 301 and the second motor 302.

[0018] The first converter 320 performs power conversion between the main battery 310 and the inverter 330. Specifically, the first converter 320 boosts the output voltage of the main battery 310 and supplies the boosted power to the first motor 301. Further, the first converter 320 steps down the voltage of the power generated by the first motor 301 and the second motor 302 and supplies the stepped-down power to the main battery 310. The first converter 320 is connected between the main battery 310 and the inverter 330.

[0019] The hybrid vehicle 1 further includes an accessory battery 510, one or more accessories 550, a second converter 520, an engine ECU 406, a motor ECU 402, an HV-ECU 404, and a measurement unit 9.

[0020] The accessory battery 510 supplies power to one or more accessories 550 mounted on the hybrid vehicle 1 via an accessory power line 530. The accessory 550 referred to here is a general term for electrical devices that operate by the output power of the accessory battery 510, such as a room lamp and a car navigation device. The output voltage value of the accessory battery 510 is lower than the output voltage value of the main battery 310, for example, 12 volts. The accessory battery 510 is charged by receiving power supply from the main battery 310 via the second converter 520.

[0021] The second converter 520 is a step-down DC / DC converter that steps down the voltage of the output power of the main battery 310 and supplies the stepped-down power to the accessory battery 510. The second converter 520 is connected between the main battery 310 and the accessory battery 510.

[0022] The engine ECU 406 controls the operating state of the engine 100. The motor ECU 402 controls the charging and discharging states of the first motor 301, the second motor 302, the inverter 330, and the main battery 310 according to the state of the hybrid vehicle 1. The HV-ECU 404 controls the entire hybrid vehicle 1 by mutually managing and controlling the engine ECU 406 and the motor ECU 402, etc. Although Figure 1 shows each ECU 402, 404, and 406 as a separate configuration, they may be configured as a control device 40 that integrates two or more ECUs 402, 404, and 406. In the following, each ECU 402, 404, and 406 will not be distinguished, and will be described as a control device 40 that integrates each ECU 402, 404, and 406. The control device 40 and the measurement unit 9 together will also be called the "control system 4".

[0023] Figure 2 is a block diagram illustrating the schematic configuration of a control system 4 comprising a control device 40 and a measurement unit 9. The control device 40 includes a communication unit 42, a CPU 44, and a storage unit 46. The communication unit 42 enables communication between the control device 40 and other components of the hybrid vehicle 1.

[0024] The CPU 44 functions as a calculation unit 443 comprising a first calculation unit 443a, a second calculation unit 443b, a third calculation unit 443c, and a fourth calculation unit 443d, and as an operation control unit 445, by deploying various programs stored in the memory unit 46. Details of each function will be described later. At least some of the functions of the CPU 44 may be implemented by hardware circuits.

[0025] The storage unit 46 includes, for example, RAM, ROM, and rewritable non-volatile memory. The storage unit 46 stores various information, including various programs that control the operation of the hybrid vehicle 1, data acquired from the measurement unit 9, a voltage transition map M, and a power threshold calculation formula F. The voltage transition map M is a map for calculating the voltage threshold Vt (Figures 4 and 5 described later). The power threshold calculation formula F is a relational expression for calculating the power threshold T (Figure 5 described later). Details of the voltage transition map M and the power threshold calculation formula F will be described later.

[0026] The measurement unit 9 measures the physical quantities necessary to control the operation of the hybrid vehicle 1. In this embodiment, the measurement unit 9 includes a current value measuring unit 91, a voltage value measuring unit 92, a temperature measuring unit 93, a SOC calculation unit 94, a resistance value calculation unit 95, and an accelerator opening degree measuring unit 96.

[0027] The current value measuring unit 91 measures the actual output current value of the main battery 310 and transmits it to the control device 40. The current value measuring unit 91 is, for example, a current sensor.

[0028] The voltage measurement unit 92 measures the actual output voltage value (potential difference) of the main battery 310 and transmits it to the control device 40. The voltage measurement unit 92 is, for example, a voltage sensor.

[0029] The temperature measuring unit 93 measures the temperature of the main battery 310 and transmits it to the control device 40. The temperature measuring unit 93 is, for example, a temperature sensor.

[0030] The SOC calculation unit 94 calculates the charge level of the main battery 310 and transmits it to the control device 40. The SOC calculation unit 94 calculates the charge level of the main battery 310 by acquiring data such as the output voltage value of the main battery 310 measured by the voltage value measurement unit 92, and comparing it with an SOC database (not shown). The SOC database includes, for example, an SOC-OCV curve representing the relationship between the charge level (SOC) of the main battery 310 and the open-circuit voltage value (OCV) of the main battery 310, and temperature characteristic data representing the relationship between the charge level of the main battery 310 and the temperature of the main battery 310. However, the method for calculating the charge level of the main battery 310 is not limited to this.

[0031] The resistance calculation unit 95 calculates the resistance of the main battery 310 and transmits it to the control device 40. The resistance calculation unit 95 obtains, for example, the temperature of the main battery 310 measured by the temperature measurement unit 93 and the charge level of the main battery 310 calculated by the SOC calculation unit 94. Then, the resistance calculation unit 95 calculates the resistance of the main battery 310, corresponding to the temperature and charge level of the main battery 310, in a resistance calculation map (not shown), for example. The resistance calculation map here refers to a map that shows, for example, the relationship between the resistance of the main battery 310, the temperature of the main battery 310, and the charge level of the main battery 310. Note that the method for calculating the resistance of the main battery 310 is not limited to this. The resistance calculation unit 95 may, for example, calculate the resistance of the main battery 310 using the output current value of the main battery 310 measured by the current value measurement unit 91 and the output voltage value of the main battery 310 measured by the voltage value measurement unit 92.

[0032] The accelerator pedal position measurement unit 96 measures the amount of operation (depression) of the accelerator pedal (not shown) by the driver of the hybrid vehicle 1 as the accelerator pedal position and transmits it to the control device 40. The accelerator pedal position measurement unit 96 is, for example, an accelerator pedal position sensor. However, the configuration of the measurement unit 9 is not limited to this. The measurement unit 9 may include other measuring devices such as a vehicle speed sensor (not shown). In addition, at least some of the functions of the measurement unit 9 may be implemented as a function of the CPU 44.

[0033] In the process of continuously supplying power from the main battery 310 to the first motor 301 as shown in Figure 1, polarization may occur in the main battery 310 as the discharge duration of the main battery 310 increases, that is, as the charge level of the main battery 310 decreases. If polarization occurs in the main battery 310, there is a risk that the output voltage value of the main battery 310 will drop excessively and exceed a predetermined reference value (hereinafter referred to as the reference voltage value). If the output voltage value of the main battery 310 drops excessively and falls below the reference voltage value, there is a concern that the lifespan of the main battery 310 will be shortened or the main battery 310 will deteriorate. Therefore, in order to prevent the output voltage value of the main battery 310 from dropping excessively, the control device 40 executes a control that limits the upper limit of the output power value (allowable discharge power value) of the main battery 310 (hereinafter referred to as power limit control). Through this power limit control, the control device 40 protects the main battery 310. Power limiting control is performed continuously, for example, until the output voltage value of the main battery 310 recovers to or above the voltage reference value, that is, until the polarization of the main battery 310 is resolved.

[0034] However, when power limiting control is in operation, the upper limit of the output power value of the main battery 310 is lower than when power limiting control is not in operation. Therefore, when power limiting control is in operation, it is more difficult to meet the required driving force from the hybrid vehicle 1 solely with the driving force from the first motor 301 compared to when power limiting control is not in operation. The required driving force here is calculated, for example, by subtracting losses from the accelerator opening. Consequently, when the hybrid vehicle 1 is running in EV driving mode, if the required driving force from the hybrid vehicle 1 exceeds the driving force that can be supplied by the first motor 301, it is necessary to start the engine 100 to compensate for the insufficient driving force. In this case, if the engine 100 is started when it is detected that the output voltage value of the main battery 310 has fallen below the reference voltage value, there is a high probability that power limiting control is already in operation. Therefore, in this case, there is a high probability that the engine 100 will be driven at high output. When engine 100 is driven at high output, the amount of fuel burned in engine 100 increases, leading to an increase in exhaust gas emissions from the tailpipe (not shown). This raises concerns that the emissions of regulated substances released into the atmosphere from hybrid vehicle 1 may increase. These regulated substances include, for example, nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and particulate matter (PM). Furthermore, when engine 100 is driven at high output, the operation of engine 100 may cause vibrations felt by the user riding in hybrid vehicle 1, potentially worsening drivability. In addition, engine 100 is often at a low temperature during its initial startup. Under such low-temperature conditions, the purification performance of a purification device, which is installed in a flow path (not shown) connecting engine 100 and the tailpipe and carries a catalyst capable of capturing regulated substances, tends to decrease. This could further increase the emissions of regulated substances released into the atmosphere from hybrid vehicle 1. Furthermore, there are concerns that when engine 100 is started for the first time, users riding in hybrid vehicle 1 may experience a delay (sluggishness) in starting engine 100, further worsening drivability.

[0035] Therefore, in this embodiment, in order to reduce the possibility of the engine 100 being driven at high output, the control device 40 detects signs of polarization occurring in the main battery 310 before polarization occurs in the main battery 310 and starts the engine 100. Specifically, the control device 40 calculates a power threshold that can detect signs of polarization by utilizing the relationship between the output voltage value and charge rate of the main battery 310, and the property that the output voltage value of the main battery 310 drops sharply when polarization occurs in the main battery 310. Then, the control device 40 determines that if the requested power value, which indicates the requested driving force from the hybrid vehicle 1, is greater than the power threshold, there is a high possibility that power limit control will be executed on the main battery 310 by continuing to output at the current output power value. As a result, the control device 40 reduces the possibility of the engine 100 being driven at high output by starting the engine 100 in advance before power limit control is executed.

[0036] Figure 3 is a flowchart illustrating the control method of the hybrid vehicle 1. Figure 4 is a schematic diagram showing an example of a voltage transition map M. The vertical axis in Figure 4 represents the output voltage value of the main battery 310. The horizontal axis in Figure 4 represents the discharge duration, i.e., the elapsed time from the start of driving in EV driving mode (duration of driving in EV driving mode). The voltage transition map M is a collection of data showing discharge curves G1 and G2 for each output current value of the main battery 310. Discharge curves G1 and G2 here refer to curves (relational expressions) that show the relationship between the charge rate of the main battery 310 and the output voltage value when the output current value (discharge amount) of the main battery 310 is kept constant. Figure 4 illustrates two types of discharge curves G1 and G2 with different output current values ​​of the main battery 310. The charge rate of the main battery 310 is roughly proportional to the discharge duration. For example, the longer the discharge duration, the lower the charge rate of the main battery 310. Figure 4 illustrates the case where the main battery 310 is at 100% charge (fully charged) when driving in EV mode begins. The voltage transition map M is generated, for example, by measuring the output current value and output voltage value of the main battery 310 and calculating the charge rate of the main battery 310 at the time of measurement. However, the method of generating the voltage transition map M is not limited to this. The voltage transition map M may also be generated, for example, by adding the output current value, output voltage value, and resistance value of the main battery 310 to the SOC-OCV curve that has been stored in the memory unit 46 in advance. Furthermore, the voltage transition map M may be generated as a graph as shown in Figure 4, or as a collection of numerical data such as a table.

[0037] In discharge curves G1 and G2, points P1 and P2 indicate the output voltage values ​​at the point when polarization occurs in the main battery 310. Thus, the output voltage value of the main battery 310 has the property of dropping sharply when polarization occurs in the main battery 310. Furthermore, just before polarization occurs in the main battery 310, there are inflection points Vt1 and Vt2, which are points where the sign changes when the second derivative of the relationship equations showing discharge curves G1 and G2 is taken. In other words, by obtaining the inflection points Vt1 and Vt2 in discharge curves G1 and G2, it is possible to capture the precursors to polarization occurring in the main battery 310.

[0038] Therefore, as shown in Figure 3, the first calculation unit 443a sets the voltage values ​​that become inflection points Vt1 and Vt2 in the discharge curves G1 and G2 as the voltage threshold Vt in the first calculation step (step S1). In other words, the voltage threshold Vt is the allowable lower voltage value at which polarization does not occur in the main battery 310. At this time, as shown in Figure 4, the voltage values ​​that become inflection points Vt1 and Vt2 in the discharge curves G1 and G2 are generally constant regardless of the magnitude of the output current value of the main battery 310. Therefore, in this embodiment, the first calculation unit 443a sets the voltage threshold Vt as a fixed value in advance using the voltage transition map M and stores it in the storage unit 46.

[0039] Next, as shown in Figure 3, the second calculation unit 443b calculates an estimated value Vo of the open-circuit voltage of the main battery 310 in the second calculation step (step S2). Figure 5 is a conceptual diagram illustrating the calculation method for the estimated open-circuit voltage Vo and the power threshold T. The y-axis (vertical axis) in Figure 5 represents the output voltage value of the main battery 310. The x-axis (horizontal axis) in Figure 5 represents the output current value of the main battery 310. The unit of the current value is amperes [A]. The unit of the voltage value is volts [V]. The unit of the resistance value is ohms [Ω]. The unit of the power threshold T is kilowatts [kW].

[0040] In this embodiment, the second calculation unit 443b obtains the current output current value In, output voltage value Vn, and resistance value R of the main battery 310 from the measurement unit 9, and calculates an estimated open-circuit voltage value Vo using the obtained values ​​In, Vn, and R. Specifically, if the y-axis is the output voltage value of the main battery 310 and the x-axis is the output current value of the main battery 310, the coordinate values ​​of the output current value In and output voltage value Vn of the main battery 310 obtained from the measurement unit 9 can be expressed as the current value N(In,Vn). Furthermore, the open-circuit voltage value of the main battery 310 is the output voltage value when the output current value of the main battery 310 is zero. Therefore, when Ohm's law is applied to this coordinate system, the open-circuit voltage value of the main battery 310 corresponds to the intercept b in the linear function y = -ax + b passing through the current value N(In,Vn). At this time, in the linear function y = -ax + b passing through the current value N(In, Vn), the slope a corresponds to the resistance value R of the main battery 310 according to Ohm's law. Therefore, the second calculation unit 443b calculates the estimated open-circuit voltage value Vo of the main battery 310 using the following equation (1). In equation (1), Vo is the estimated open-circuit voltage value Vo of the main battery 310. In is the current output current value In of the main battery 310, and is the current value obtained from the current value measurement unit 91 of the measurement unit 9 shown in Figure 1. Vn is the current output voltage value Vn of the main battery 310, and is the voltage value obtained from the voltage value measurement unit 92 of the measurement unit 9. R is the current resistance value R of the main battery 310, and is the resistance value R obtained from the resistance value calculation unit 95 of the measurement unit 9. Vo = Vn + In × R Equation (1)

[0041] Next, as shown in Figure 3, the third calculation unit 443c calculates the upper limit of the current value that satisfies the voltage threshold Vt set in the first calculation step (step S1) as the current threshold It in the third calculation step (step S3). The current threshold It is the allowable upper limit of current value at the point when the voltage threshold Vt is reached, assuming that the output power value at the current output power value is continued. The current output power value here is the value obtained by multiplying the output current value In of the main battery 310 obtained from the current value measurement unit 91 by the output voltage value Vn of the main battery 310 obtained from the voltage value measurement unit 92.

[0042] As shown in Figure 5, the current threshold It can be calculated by substituting the voltage threshold Vt for y in the linear function y = -ax + b passing through the current value N(In, Vn), substituting the resistance value R of the main battery 310 for a, and substituting the estimated open-circuit voltage value Vo calculated in equation (1) above for b. Therefore, the third calculation unit 443c calculates the current threshold It using the following equation (2). In equation (2), It is the current threshold It. Vt is the voltage threshold Vt set in the first calculation step (step S1) shown in Figure 3. Vo is the estimated open-circuit voltage Vo calculated in the second calculation step (step S2). In is the current output current value In of the main battery 310, and is the current value obtained from the current value measurement unit 91 of the measurement unit 9 shown in Figure 1. Vn is the current output voltage value Vn of the main battery 310, and is the voltage value obtained from the voltage value measurement unit 92 of the measurement unit 9. R is the current resistance value R of the main battery 310, and is the resistance value R obtained from the resistance value calculation unit 95 of the measurement unit 9. It=(Vo-Vt)÷R=(Vn+In×R-Vt)÷R Formula (2)

[0043] Next, the fourth calculation unit 443d calculates the power threshold T in the fourth calculation step (step S4), as shown in Figure 3. The power threshold T is a power value greater than the output power value of the main battery 310 when polarization occurs in the main battery 310. In this embodiment, the fourth calculation unit 443d calculates the power threshold T by multiplying the voltage threshold Vt, which is the allowable lower voltage value related to the occurrence of polarization, and the current threshold It, which is the allowable upper current value corresponding to the voltage threshold Vt, as shown in Figure 5 and equation (3) below. In equation (3), T is the power threshold T. Vt is the voltage threshold Vt set in the first calculation step (step S1). It is the current threshold It calculated in the third calculation step (step S3). Equation (3) corresponds to the power threshold calculation formula F shown in Figure 2. T=Vt×It Equation (3) However, the method for calculating the power threshold T is not limited to this.

[0044] Next, the operation control unit 445 (Figure 2) of the control device 40 compares the power request value from the hybrid vehicle 1 with the power threshold T calculated in step S4 during the operation control process, as shown in Figure 3. If the power request value from the hybrid vehicle 1 is greater than the power threshold T (step S5: Yes), the operation control unit 445 starts the engine 100 and switches the driving mode of the hybrid vehicle 1 from EV driving mode to HV driving mode (step S6). Conversely, if the power request value from the hybrid vehicle 1 is less than or equal to the power threshold T (step S5: No), the operation control unit 445 continues the EV driving mode without starting the engine 100.

[0045] According to the above embodiment, the control device 40 can calculate a power threshold T that can detect signs of polarization by utilizing the relationship between the output voltage value and the charge level of the main battery 310, and the property that the output voltage value of the main battery 310 drops sharply when polarization occurs. The control device 40 can then start the engine 100 when the requested power value, which indicates the requested driving force from the hybrid vehicle 1, is greater than the power threshold T. As a result, the control device 40 can start the engine 100 in advance before power limit control is performed, thereby reducing the possibility of the engine 100 being driven at high output. Therefore, the possibility of increased exhaust gas emissions and deterioration of drivability can be reduced.

[0046] B. Other embodiments: In the above embodiment, the voltage threshold Vt was a fixed value. However, the disclosure is not limited thereto. The voltage threshold Vt may be variable according to the output current value of the main battery 310. In this case as well, the first calculation unit 443a sets the voltage threshold Vt by referring to, for example, the voltage transition map M shown in Figure 4. In this configuration, the voltage threshold Vt can be set according to the output current value of the main battery 310. This allows the voltage threshold Vt to be set more accurately, thereby improving the accuracy of the power threshold T. Therefore, the possibility of the engine 100 being driven at high output can be further reduced.

[0047] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features of the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0048] 1...Hybrid vehicle, 4...Control system, 9...Measurement unit, 11...Charger, 12...Drive wheel, 13...Vehicle-side connector, 14...Reduction gear, 15...Power supply-side connector, 19...External power supply, 40...Control device, 42...Communication unit, 44...CPU, 46...Memory unit, 91...Current value measurement unit, 92...Voltage value measurement unit, 93...Temperature measurement unit, 94...SOC calculation unit, 95...Resistance value calculation unit, 96...Accelerator opening measurement unit, 100...Engine, 200...Power split mechanism, 212...Output shaft, 301...First motor, 302...Second motor, 310...Main battery, 320...First converter, 330...Inverter, 402…Motor ECU, 404…HV-ECU, 406…Engine ECU, 443…Calculation Unit, 443a…First Calculation Unit, 443b…Second Calculation Unit, 443c…Third Calculation Unit, 443d…Fourth Calculation Unit, 445…Operation Control Unit, 510…Auxiliary Battery, 520…Second Converter, 530…Auxiliary Power Line, 550…Auxiliary Equipment, F…Power Threshold Calculation Formula, G1, G2…Discharge Curve, In…Measured Output Current Value, It…Current Threshold, M…Voltage Transition Map, N…Current Value, R…Resistance Value, T…Power Threshold, Vn…Measured Output Voltage Value, Vo…Estimated Open Circuit Voltage Value, Vt…Voltage Threshold, Vt1, Vt2…Inflection Points

Claims

1. A control device installed in a hybrid vehicle comprising an engine, an electric generator, and a battery that supplies power to the electric generator, The aforementioned hybrid vehicle is An EV driving mode in which the vehicle is driven using the electric generator as the power source with the engine stopped, It has an HV driving mode in which the vehicle is driven using the engine and the electric generator as the driving force sources, The control device, when the hybrid vehicle is driving in the EV driving mode, A calculation unit that calculates a power threshold value that is greater than the output power value of the battery when polarization occurs in the battery, The system includes an operation control unit that, when the power request value from the hybrid vehicle is greater than the power threshold, starts the engine and switches the driving mode of the hybrid vehicle from the EV driving mode to the HV driving mode, The calculation unit described above, A first calculation unit calculates an inflection point in a discharge curve that shows the relationship between the charge level of the battery and the output voltage value of the battery when discharging the power from the battery, as a voltage threshold. A second calculation unit calculates an estimated value of the open-circuit voltage of the battery using the measured output current value of the battery, the measured output voltage value of the battery, and the resistance value of the battery. A third calculation unit calculates a current threshold using the voltage threshold, the estimated value of the open-circuit voltage, and the resistance value of the battery. A control device comprising: a fourth calculation unit that calculates the power threshold by multiplying the current threshold by the voltage threshold.

2. A control system installed in a hybrid vehicle comprising an engine, an electric generator, and a battery that supplies power to the electric generator, The control device according to claim 1, A current value measuring unit that measures the actual value of the output current of the aforementioned battery, A voltage value measuring unit for measuring the actual output voltage value of the aforementioned battery, A control system comprising a resistance value calculation unit for calculating the resistance value of the aforementioned battery.

3. A control method for a hybrid vehicle comprising an engine, a motor-generator, and a battery that supplies power to the motor-generator, The aforementioned hybrid vehicle is An EV driving mode in which the vehicle is driven using the electric generator as the power source with the engine stopped, It has an HV driving mode in which the vehicle is driven using the engine and the electric generator as the driving force sources, The control method described above applies when the hybrid vehicle is driving in the EV driving mode. A calculation step of calculating a power threshold value that is greater than the output power value of the battery when polarization occurs in the battery, The operation control step includes, when the power request value from the hybrid vehicle is greater than the power threshold, starting the engine and switching the driving mode of the hybrid vehicle from the EV driving mode to the HV driving mode, The calculation process described above is: A first calculation step of calculating an inflection point in a discharge curve that shows the relationship between the charge level of the battery and the output voltage value of the battery when discharging the power from the battery, as a voltage threshold, A second calculation step involves calculating an estimated value of the open-circuit voltage of the battery using the measured output current value of the battery, the measured output voltage value of the battery, and the resistance value of the battery. A third calculation step of calculating a current threshold using the voltage threshold, the estimated value of the open-circuit voltage, and the resistance value of the battery, A control method comprising: a fourth calculation step of calculating the power threshold by multiplying the current threshold by the voltage threshold.

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