Hybrid vehicles

Abstract

To provide technique for restraining a reduction of a battery charge quantity without remarkably reducing travel performance in a hybrid vehicle.SOLUTION: A hybrid vehicle 1 comprises: a driving wheel 30; a transmission 12 connected to the driving wheel 30; an engine 11 connected to the transmission 12 and generating torque for the driving wheel 30; a high-voltage battery 23; a motor generator 21 generating the torque for the driving wheel 30 by using electric power supplied from the high-voltage battery 23; and a control device which determines the upper limit value of the electric power supplied to the motor generator 21 from the high-voltage battery 23 based on rotation speed of the engine 11 and the gear ratio of the transmission 12, and controls the electric power supplied to the motor generator 21 from the high-voltage battery 23 to be less than an upper limit value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to hybrid vehicles. [Background technology]

[0002] International Publication No. 2016 / 092602 (Patent Document 1) discloses a technology for assisting the driving of a hybrid vehicle equipped with an engine and a motor generator with the output of the motor generator when the engine output alone is not sufficient to achieve a predetermined acceleration (hereinafter also referred to as "driving assist"). The hybrid vehicle disclosed in Patent Document 1 is configured to limit the output of the motor generator when the vehicle speed V reaches a vehicle speed V1 at which the power consumption of the motor generator is minimized, in order to prevent excessive reduction in the battery charge level during driving assist. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 092602 Summary of the Invention [Problem to be solved by the invention]

[0004] The hybrid vehicle disclosed in Patent Document 1 can prevent excessive reduction in the battery charge level, but because the output of the motor generator is limited based only on the vehicle speed, the driving assistance provided by the motor generator may be excessively suppressed, which could result in a significant reduction in driving performance.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a technology for suppressing a decrease in battery charge amount in a hybrid vehicle without significantly degrading driving performance. [Means for solving the problem]

[0006] A hybrid vehicle according to the present disclosure includes drive wheels, a transmission connected to the drive wheels, an engine connected to the transmission and generating torque for the drive wheels, a battery, and a motor generator using electric power supplied from the battery to generate torque for the drive wheels. , Ba The power supplied from the battery to the motor generator Power a control device that controls the value to be less than the upper limit; , a temperature sensor to measure the temperature of the battery; Equipped with. The control device stores a plurality of discharge amount determination tables, each corresponding to a plurality of gear ratios of the transmission and having an upper limit value set therein, selects from the plurality of discharge amount determination tables a discharge amount determination table corresponding to the current gear ratio of the transmission, and determines the upper limit value using the selected discharge amount determination table based on the engine rotation speed and the measurement value of the temperature sensor.

[0007] According to the above configuration, the power supplied from the battery to the motor generator is controlled to be below an upper limit determined based on the engine speed and the transmission gear ratio, thereby suppressing a decrease in the battery charge amount without significantly degrading driving performance.

[0008] Preferably, the control device determines a larger value as the upper limit when the rotation speed is the first rotation speed than when the rotation speed is a second rotation speed that is larger than the first rotation speed.

[0009] According to the above configuration, when the engine speed at which improved acceleration can be expected is lower, the upper limit of the power supplied from the battery to the motor generator is increased, thereby preventing excessive suppression of assistance by the motor generator during driving when improved acceleration can be expected.

[0010] Preferably, when the gear ratio is the first gear ratio, the control device determines a smaller value as the upper limit value than when the gear ratio is a second gear ratio that is larger than the first gear ratio.

[0011] According to the above configuration, when the transmission gear ratio at which improved acceleration can be expected is larger, the upper limit of the power supplied from the battery to the motor generator becomes larger, thereby preventing excessive suppression of assistance by the motor generator during driving when improved acceleration can be expected.

[0012] Preferably, the upper limit includes zero.

[0013] According to the above configuration, the electric power supplied from the battery to the motor generator can be set to zero, thereby stopping the assist by the motor generator.

[0014] Preferably, the motor generator uses the driving force of the driving wheels. Generated electricity Battery Supply to The control device is Based on the temperature sensor measurement value, the power generation limit level is determined, which indicates the degree to which power generation by the motor generator is limited according to the battery condition, and the engine speed and The upper limit is determined based on the power generation limit level.

[0015] According to the above configuration, the power supplied from the battery to the motor generator is determined based on the engine speed and the transmission gear ratio as well as the , release Since the power generation limit is determined based on the power generation limit level, it is possible to prevent the battery charge amount from continuously decreasing due to the power generation limit.

[0016] A hybrid vehicle according to the present disclosure includes drive wheels, a transmission connected to the drive wheels, an engine connected to the transmission and generating torque for the drive wheels, a battery, a motor generator using electric power supplied from the battery to generate torque for the drive wheels, a control device that controls the electric power supplied from the battery to the motor generator to be less than an upper limit, and a current sensor that measures current input and output to the battery. The control device stores a plurality of discharge amount determination tables, each corresponding to a plurality of gear ratios of the transmission and each having a predetermined upper limit, selects from the plurality of discharge amount determination tables a discharge amount determination table corresponding to the current gear ratio of the transmission, and uses the selected discharge amount determination table to determine the upper limit based on the engine speed and a measurement value of the current sensor.

[0017] above According to the above configuration, the power supplied from the battery to the motor generator is controlled by the engine speed and the transmission gear ratio. Controlled to below the upper limit determined based on Because, Prevents loss of battery charge without significantly reducing driving performance It is possible.

[0018] Preferably, The motor generator generates electric power using the driving force of the drive wheels and supplies the generated electric power to the battery. The control device determines, based on the measurement value of the current sensor, Indicates the degree to which power generation by the motor generator is limited according to the current input and output to the battery. Determine power generation limit level The upper limit is determined based on the engine speed and power generation limit level. .

[0019] According to the above configuration, the power supplied from the battery to the motor generator is determined by the following in addition to the engine speed and the transmission gear ratio: Power generation limit level Since the power generation limit is determined based on the above, it is possible to prevent the battery charge amount from continuously decreasing due to the power generation limit. [Effects of the Invention]

[0020] According to the present disclosure, in a hybrid vehicle, it is possible to suppress a decrease in the battery charge amount without significantly degrading the driving performance. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a diagram showing a schematic configuration of a hybrid vehicle according to an embodiment; [Figure 2] FIG. 2 is a diagram illustrating an example of driving assistance by a motor generator. [Figure 3] FIG. 4 is a diagram showing a calculation formula for calculating a vehicle speed. [Figure 4] FIG. 4 is a diagram showing vehicle speed corresponding to engine rotation speed and gear position. [Figure 5] FIG. 10 is a diagram showing gear ratios for each gear position. [Figure 6] FIG. 10 is a diagram showing a calculation formula for calculating the degree of improvement in acceleration. [Figure 7] FIG. 10 is a diagram showing a discharge amount determination table when the gear position is 1st. [Figure 8] FIG. 10 is a diagram showing a discharge amount determination table when the gear position is 6th. [Figure 9] 6 is a flowchart illustrating an example of a process executed by the control device according to the embodiment when determining an upper limit value of the battery discharge amount. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0023] [Overall configuration] Fig. 1 is a diagram showing a schematic configuration of a hybrid vehicle 1 according to an embodiment. As shown in Fig. 1, the hybrid vehicle 1 includes an engine 11, a transmission 12, a starter 19, a motor generator 21, an inverter 22, a high-voltage battery 23, a DC / DC converter 25, a low-voltage battery 26, accessories 27, a battery management system 28 (hereinafter also referred to as "BMS 28"), drive wheels 30, a crank angle sensor 41, a temperature sensor 42, a motor current sensor 43, a vehicle ECU (Electronic Control Unit) 51, an engine ECU 52, and a motor ECU 53. The hybrid vehicle 1 uses the engine 11 and the motor generator 21 as drive sources.

[0024] The engine 11 is an internal combustion engine having a plurality of cylinders 13 and a plurality of fuel injection valves 15 provided in each of the cylinders 13. Each fuel injection valve 15 is driven by a control signal from the engine ECU 52 and injects fuel into the corresponding cylinder 13.

[0025] One end of the crankshaft 11A of the engine 11 is connected to the drive wheels 30 via the transmission 12. The other end of the crankshaft 11A is connected to a first pulley 16. A transmission belt 17 is wound around the first pulley 16. Although not shown, the crankshaft 11A of the engine 11 is also connected to a hydraulic pump for generating hydraulic pressure via a belt, pulleys, gears (sprockets), chains, and the like.

[0026] The engine 11 is provided with a crank angle sensor 41. The crank angle sensor 41 outputs a detection signal corresponding to the rotation angle of the crankshaft 11A (i.e., the crank angle) to the vehicle ECU 51 and the engine ECU 52. The vehicle ECU 51 and the engine ECU 52 detect the crank angle and the rotation speed of the engine 11 (hereinafter also referred to as "engine rotation speed") based on the output of the crank angle sensor 41.

[0027] The transmission 12 is a transmission connected between the engine 11 and the drive wheels 30, and serves to adjust the torque output from the engine 11 based on a gear ratio (speed ratio) and transmit the torque to the drive wheels 30. The gear ratio indicates the ratio between the engine speed for each gear position (gear stage) and the speed changed by the transmission 12 (the speed of rotation output from the transmission 12). The transmission 12 may be a stepped automatic transmission that can change the gear ratio in stages, or a continuously variable transmission that can change the gear ratio continuously.

[0028] The motor generator 21 converts electrical energy into mechanical energy and vice versa. The motor generator 21 is, for example, a three-phase AC synchronous rotating electric machine with a permanent magnet embedded in the rotor. One end of a rotating shaft 21A of the motor generator 21 is connected to a second pulley 18. A transmission belt 17 is wound around the second pulley 18. That is, the motor generator 21 is connected to the crankshaft 11A of the engine 11 via the second pulley 18, the transmission belt 17, and the first pulley 16.

[0029] When functioning as an electric motor, motor generator 21 generates torque for drive wheels 30 using electric power supplied from high-voltage battery 23. Specifically, when motor generator 21 functions as an electric motor, rotational torque is applied from motor generator 21 to second pulley 18, and this rotational torque is input to crankshaft 11A of engine 11 via transmission belt 17 and first pulley 16. This allows motor generator 21 to assist the driving of engine 11, thereby assisting hybrid vehicle 1 in traveling.

[0030] When functioning as a generator, motor generator 21 generates electricity using the driving force of engine 11. Specifically, when motor generator 21 functions as a generator, the rotational torque of crankshaft 11A of engine 11 is input to rotating shaft 21A of motor generator 21 via first pulley 16, transmission belt 17, and second pulley 18. Motor generator 21 generates electricity in response to the rotation of rotating shaft 21A.

[0031] The motor generator 21 is electrically connected to the high-voltage battery 23 via the inverter 22. The inverter 22 is a so-called bidirectional inverter. In accordance with a control signal from the motor ECU 53, the inverter 22 converts AC power generated by the motor generator 21 into DC power and outputs the DC power to the high-voltage battery 23. The inverter 22 also converts DC power supplied from the high-voltage battery 23 into AC power and outputs the AC power to the motor generator 21.

[0032] The motor current sensor 43 is provided in the motor generator 21 and measures the current flowing through the motor generator 21. For example, if the motor generator 21 is a three-phase AC synchronous rotating electric machine, the motor current sensor 43 measures the current of each phase of the motor generator 21.

[0033] The high-voltage battery 23 is an example of the "battery" of the present disclosure, and is, for example, a 48 V lithium-ion battery. Note that the high-voltage battery 23 is not limited to a lithium-ion battery, and may be another secondary battery (for example, a nickel-metal hydride battery) or an all-solid-state secondary battery.

[0034] When the motor generator 21 functions as an electric motor, the high-voltage battery 23 supplies power to the motor generator 21 via the inverter 22. When the motor generator 21 functions as a generator, the high-voltage battery 23 is charged by receiving power generated by the motor generator 21 via the inverter 22.

[0035] The BMS 28 is an example of a "current sensor" in the present disclosure. The BMS 28 measures the current value, voltage value, and state of charge (SOC) of the high-voltage battery 23. The measured values ​​of the BMS 28 are input to the vehicle ECU 51.

[0036] DC / DC converter 25 is connected to motor generator 21 via inverter 22. DC / DC converter 25 is also connected to high-voltage battery 23. DC / DC converter 25 steps down the DC voltages output from inverter 22 and high-voltage battery 23 to 12 V to 15 V, and outputs the voltages to auxiliary equipment 27 and low-voltage battery 26.

[0037] The low-voltage battery 26 is connected to the DC / DC converter 25. The low-voltage battery 26 is a 12V lead-acid battery having a lower voltage than the high-voltage battery 23. The low-voltage battery 26 outputs a direct current voltage of 12V when the DC / DC converter 25 is not operating or when the output voltage of the DC / DC converter 25 is 12V. The low-voltage battery 26 is charged by receiving power from the DC / DC converter 25 when the output voltage of the DC / DC converter 25 is higher than the open circuit voltage (OCV) of the low-voltage battery 26.

[0038] Various accessories (vehicle electrical equipment) 27 are connected to the DC / DC converter 25 and the low-voltage battery 26. The accessories 27 include, for example, lighting-related components such as vehicle headlights, turn signals, and interior lights, as well as interior equipment such as a car navigation system or speakers. The accessories 27 are supplied with power from the low-voltage battery 26 when the DC / DC converter 25 is not operating. The accessories 27 are supplied with power from the DC / DC converter 25 when the output voltage of the DC / DC converter 25 is higher than the open-circuit voltage (OCV) of the low-voltage battery 26.

[0039] A starter 19 is connected to the DC / DC converter 25 and the low-voltage battery 26 as one of the accessories 27. The starter 19 is a DC motor, and an output shaft of the starter 19 is connected to the crankshaft 11A of the engine 11. The starter 19 is driven by power supplied from the low-voltage battery 26 or the DC / DC converter 25.

[0040] The temperature sensor 42 is provided in the high voltage battery 23 and measures the temperature of the high voltage battery 23. The measurement value of the temperature sensor 42 is input to the vehicle ECU 51.

[0041] Each of the vehicle ECU 51, the engine ECU 52, and the motor ECU 53 includes a central processing unit (CPU) as a computing device, a storage device, and input / output ports for inputting and outputting various signals (not shown). The storage device includes a random access memory (RAM) as a working memory and a storage device (a rewritable nonvolatile memory such as a read-only memory (ROM) or an EEPROM).

[0042] The vehicle ECU 51, engine ECU 52, and motor ECU 53 receive signals from various devices (sensors, etc.) connected to their input ports and control various devices connected to their output ports based on the received signals. Various controls are performed by the CPU executing programs stored in the storage device. The controls performed by the vehicle ECU 51, engine ECU 52, and motor ECU 53 are not limited to software processing, but can also be realized by processing using dedicated hardware (electronic circuits).

[0043] The vehicle ECU 51 calculates an output demand value for the engine 11 (for example, a fuel injection amount, a torque demand value, etc.) and an output demand value for the motor generator 21 (for example, a torque demand value, etc.). The vehicle ECU 51 outputs the output demand value for the engine 11 to the engine ECU 52, and outputs the output demand value for the motor generator 21 to the motor ECU 53. Hereinafter, the torque demand value for the engine 11 will also be referred to as "engine demand torque." The torque demand value for the motor generator 21 will also be referred to as "motor demand torque."

[0044] The motor ECU 53 controls the supply of power to the motor generator 21 via the inverter 22 based on the motor required torque input from the vehicle ECU 51. More specifically, the motor ECU 53 sets a command value based on the motor required torque, and controls the inverter 22 so that the actual torque output by the motor generator 21 becomes the command value.

[0045] The engine ECU 52 performs operation control (such as fuel injection control) of the engine 11 based on an output requirement value (for example, engine required torque) input from the vehicle ECU 51. For example, when a fuel injection amount control signal is input from the vehicle ECU 51, the engine ECU 52 controls the fuel injection valve 15 so that the input fuel injection amount of fuel is injected into the cylinder 13. In other words, the vehicle ECU 51 controls the fuel injection amount per injection from the fuel injection valve 15 of the engine 11 via the engine ECU 52. In this way, the engine 11 generates actual torque for the drive wheels 30.

[0046] Furthermore, when a start request for the engine 11 is made while the engine 11 is stopped, the vehicle ECU 51 starts the engine 11 by cranking the engine 11 using the starter 19 or the motor generator 21. Specifically, the vehicle ECU 51 cranks the engine 11 using the starter 19 or the motor generator 21, and when the engine rotation speed reaches a predetermined starting rotation speed as a result of the cranking, the vehicle ECU 51 injects fuel from the fuel injection valve 15 to start the engine 11.

[0047] The vehicle ECU 51, engine ECU 52, and motor ECU 53 described above are examples of the "control device" of the present disclosure. In the hybrid vehicle 1 according to the embodiment, the control device is divided into three parts: the vehicle ECU 51, the engine ECU 52, and the motor ECU 53. However, the control device is not necessarily limited to being divided into three parts. That is, the control device may be divided into four or more parts, or may be one part without being divided. Hereinafter, the vehicle ECU 51, the engine ECU 52, and the motor ECU 53 will be referred to as the "control device" without distinction.

[0048] [Driving assistance by motor generator] FIG. 2 is a diagram illustrating an example of driving assistance by the motor generator 21. FIG. 2 shows a graph representing changes in torque over time while the hybrid vehicle 1 is driving. In the graph of FIG. 2, the horizontal axis represents time and the vertical axis represents torque. The solid line represents changes in torque requested by the user of the hybrid vehicle 1 (hereinafter also referred to as "user requested torque"). The dashed line represents changes in engine requested torque. Note that "maximum shaft torque" in the diagram refers to the maximum value of torque that the hybrid vehicle 1 can tolerate.

[0049] As shown in Fig. 2, when hybrid vehicle 1 starts accelerating, user-requested torque increases in accordance with the user's accelerator pedal depression and vehicle speed. Here, assume a case where engine-requested torque is limited. For example, when the amount of air in engine 11 is insufficient, the control device controls engine 11 to reduce the maximum fuel injection amount of engine 11 from a normal value in order to prevent a deterioration in fuel efficiency and an increase in carbon dioxide emissions and to maintain the reliability of engine 11. In other words, the control device limits engine-requested torque by correcting the fuel injection amount of engine 11 to be reduced.

[0050] For example, as shown by the dashed line graph in Figure 2, if a limit is placed on the engine request torque at timing t1 after the start of acceleration, a difference will occur between the user request torque and the actual torque generated by the engine 11 after timing t1. Therefore, as shown by the solid line graph in Figure 2, in hybrid vehicle 1, driving assistance by the motor generator is started after timing t1, causing motor generator 21 to generate torque for drive wheels 30 using electric power supplied from high-voltage battery 23. As a result, hybrid vehicle 1 can compensate for the difference between the user request torque and the actual torque generated by engine 11 using the torque generated by the driving assistance of motor generator 21 until timing t2 when the driving assistance ends is reached.

[0051] [Control device suppresses driving assistance] As described above, the hybrid vehicle 1 is configured so that the motor generator 21 performs driving assistance using electric power supplied from the high-voltage battery 23. However, if the electric power used in the driving assistance is excessively large, or if driving assistance is performed frequently, the charge level of the high-voltage battery 23 may continue to decrease, and the high-voltage battery 23 may enter a shutdown state (for example, a state in which power generation and driving assistance are not possible). Therefore, to prevent the high-voltage battery 23 from entering a shutdown state, it is necessary to maintain the charge level of the high-voltage battery 23 by suppressing the electric power supplied from the high-voltage battery 23 to the motor generator 21 during driving assistance (i.e., the amount of discharge from the high-voltage battery 23).

[0052] In driving assistance, a method of suppressing the amount of discharge from the high-voltage battery 23 (hereinafter also referred to as "battery discharge amount") in accordance with the vehicle speed is conceivable. However, if the amount of battery discharge in driving assistance is suppressed based only on the vehicle speed, the driving assistance by the motor generator 21 may be excessively suppressed, which may result in a significant deterioration in driving performance.

[0053] Here, the calculation formula for vehicle speed will be explained. FIG. 3 is a diagram showing the calculation formula for calculating vehicle speed. As shown in FIG. 3, vehicle speed can be calculated using various values ​​such as the outer periphery of the drive wheels 30, engine speed, gear ratio, and differential reduction ratio. Of these values, the outer periphery of the drive wheels 30 and the differential reduction ratio are fixed values ​​determined according to the specifications of the hybrid vehicle 1. On the other hand, the engine speed and gear ratio are parameters that can change while the vehicle is traveling. In other words, vehicle speed changes according to the engine speed and gear ratio.

[0054] FIG. 4 is a diagram showing vehicle speed corresponding to engine rotation speed and gear position. FIG. 5 is a diagram showing gear ratios for each gear position. As shown in FIG. 4, hybrid vehicle 1 is provided with a plurality of gear positions from 1st to 6th. As shown in FIG. 5, gear ratios are determined for each of the plurality of gear positions. As with the calculation formula shown in FIG. 3, vehicle speed can be calculated using engine rotation speed and gear ratio. In other words, as shown in FIG. 4, vehicle speed changes depending on the combination of engine rotation speed and gear position (gear ratio).

[0055] As shown by dashed lines A and B in Figure 4, the vehicle speed may be the same even when the engine speed and gear position (gear ratio) are different. For example, as shown by dashed line A, when the gear position is 3rd and the engine speed is 2400 rpm, the vehicle speed is 57 km / h, while as shown by dashed line B, when the gear position is 4th and the engine speed is 1600 rpm, the vehicle speed is also 57 km / h.

[0056] Fig. 6 is a diagram showing a formula for calculating the degree of improvement in acceleration. As shown in Fig. 6, the degree of improvement in acceleration can be calculated using various values, such as the output [kw] of motor generator 21, engine speed [rpm], gear ratio, differential reduction ratio, outer perimeter of drive wheels [m], and weight [kg] of hybrid vehicle 1. Of these values, the outer perimeter of drive wheels 30, differential reduction ratio, and weight are fixed values ​​determined according to the specifications of hybrid vehicle 1. In other words, when the output of motor generator 21 is constant, the degree of improvement in acceleration changes depending on the engine speed and gear ratio.

[0057] 6, when the output of motor generator 21 is constant, the smaller the engine speed and the larger the gear ratio, the greater the improvement in acceleration. In other words, when the output of motor generator 21 is constant, the smaller the engine speed and the larger the gear ratio, the greater the improvement in acceleration due to driving assistance can be expected.

[0058] Therefore, suppressing battery discharge based on engine speed and gear ratio allows for more precise adjustment of driving assistance than suppressing battery discharge based solely on vehicle speed, thereby enabling appropriate suppression of battery discharge while maintaining better driving performance.

[0059] In light of the above, the hybrid vehicle 1 according to the embodiment is configured to suppress the amount of battery discharge based on the engine speed and gear ratio during driving assistance, rather than suppressing the amount of battery discharge based only on the vehicle speed.

[0060] Specifically, the control device of the hybrid vehicle 1 stores in a storage device a discharge amount determination table for determining the amount of battery discharge during travel assistance based on the engine speed and gear ratio. A discharge amount determination table is provided for each of the 1st to 6th gear positions (gear ratios). Furthermore, in each discharge amount determination table, an upper limit value for the amount of battery discharge is set based on the engine speed and power generation limit level.

[0061] The power generation limit level is the high-voltage battery 23 The state The motor generator 21 operates according to the state of the Ru The hybrid vehicle 1 has four power generation limit levels, 0 to 3. When the power generation limit level is 0, the high voltage battery 23 is at the lowest level among the four power generation limit levels. The state Since the condition is the worst, the control device , release When the power generation limit level is 3, the power generation limit is set to the highest level. The state Since the condition is the best, the control device , release It places the least restrictions on electricity.

[0062] The control device is connected to a high-voltage battery 23 The stateThe control device uses the measurement value of the temperature sensor 42 when determining the state of the high-voltage battery 23. That is, the control device determines the power generation limit level based on the temperature of the high-voltage battery 23 measured by the temperature sensor 42. Typically, the temperature of the high-voltage battery 23 is between -20°C and 60°C. For example, if the measurement value of the temperature sensor 42 is below -20°C, the control device imposes a power generation limit to prevent deterioration of the high-voltage battery 23. Also, if the measurement value of the temperature sensor 42 exceeds 60°C, the control device imposes a power generation limit for safety reasons.

[0063] Furthermore, the control device is The state In determining the power generation limit state, the control device uses the measurement value of the BMS 28. That is, the control device determines the power generation limit level based on the current input / output to / from the high-voltage battery 23 (hereinafter also referred to as "battery current") measured by the BMS 28. For example, if the battery current is represented by Ib, the control device calculates Σ(Ib 2 ) is greater than a predetermined threshold, power generation is limited to prevent deterioration of the high-voltage battery 23. That is, the control device determines the power generation limit level based on the frequency of use of the high-voltage battery 23.

[0064] The control device determines one power generation limit level from four power generation limit levels 0 to 3 based on the temperature and battery current of the high-voltage battery 23. The control device is not limited to determining the power generation limit level based on both the temperature and battery current of the high-voltage battery 23, but may determine the power generation limit level based on either the temperature or the battery current of the high-voltage battery 23.

[0065] If driving assistance is performed while power generation is limited, the charge of the high-voltage battery 23 consumed during the driving assistance cannot be replenished by power generation after the driving assistance, and there is a possibility that the charge of the high-voltage battery 23 will continue to decrease. For this reason, the discharge amount determination table sets an upper limit for the battery discharge amount based on the power generation limit level in addition to the engine speed and gear ratio.

[0066] FIG. 7 is a diagram showing a discharge amount determination table when the gear position is 1st. FIG. 8 is a diagram showing a discharge amount determination table when the gear position is 6th. In the discharge amount determination tables of FIGS. 7 and 8, any value between 0 and 10 kW is stored as the upper limit value of the battery discharge amount. The control device performs driving assistance without exceeding the upper limit value determined based on the discharge amount determination table. Note that when the upper limit value of the battery discharge amount is 10 kW, driving assistance by the control device is not suppressed, and when the upper limit value of the battery discharge amount is 0 kW, driving assistance by the control device is prohibited.

[0067] As explained with reference to the formula for calculating the degree of improvement in acceleration in Figure 6, when the output of motor generator 21 is constant, the lower the engine speed, the greater the expected improvement in acceleration due to driving assistance. For this reason, as shown in Figures 7 and 8, in the discharge amount determination table, the lower the engine speed, the larger the value set as the upper limit of the battery discharge amount, and the higher the engine speed, the smaller the value set as the upper limit of the battery discharge amount.

[0068] For example, when the gear position is 1st, the control device uses the discharge amount determination table of Figure 7 to determine the upper limit of the battery discharge amount to 10 kW when the power generation limit level is 0 and the engine speed is 800 rpm. On the other hand, when the gear position is 1st, the control device uses the discharge amount determination table of Figure 7 to determine the upper limit of the battery discharge amount to 1 kW when the power generation limit level is 0 and the engine speed is 4000 rpm. In this way, even if the gear ratio and power generation limit level are the same, the control device determines a larger value as the upper limit of the battery discharge amount when the engine speed is 800 rpm than when the engine speed is 4000 rpm.

[0069] In addition, not only when the gear position is 1st, but also when the gear position is 2nd to 6th, in the discharge amount determination table, the lower the engine rotation speed, the larger the value set as the upper limit of the battery discharge amount, and the higher the engine rotation speed, the smaller the value set as the upper limit of the battery discharge amount.

[0070] Furthermore, as explained with reference to the calculation formula for the degree of improvement in acceleration in Figure 6, when the output of motor generator 21 is constant, the greater the gear ratio, the greater the expected effect of improving acceleration due to driving assistance. For this reason, as shown in Figures 7 and 8, in the discharge amount determination table, the greater the gear ratio, the greater the value set as the upper limit of the battery discharge amount, and the smaller the gear ratio, the smaller the value set as the upper limit of the battery discharge amount.

[0071] For example, when the gear position is 1st, the control device uses the discharge amount determination table in Figure 7 to determine the upper limit of the battery discharge amount to 10 kW when the power generation limit level is 0 and the engine speed is 2000 rpm. On the other hand, when the gear position is 6th, the control device uses the discharge amount determination table in Figure 8 to determine the upper limit of the battery discharge amount to 1 kW when the power generation limit level is 0 and the engine speed is 2000 rpm. In this way, even if the engine speed and power generation limit level are the same, when the gear ratio is 1st, the control device determines a larger value as the upper limit of the battery discharge amount than when the gear ratio is 6th.

[0072] In addition, not only when comparing the 1st gear position with the 6th gear position, but also when comparing any of the 1st to 6th gear positions, the discharge amount determination table sets a larger value as the upper limit of the battery discharge amount as the gear ratio increases, and sets a smaller value as the gear ratio decreases.

[0073] Furthermore, as shown in FIGS. 7 and 8, in the discharge amount determination table, Ru The less the power generation restriction is imposed (i.e., the lower the power generation restriction level), the larger the upper limit value of the battery discharge amount is set, and the more the motor generator 21 can discharge the battery. Ru The more restricted the power is (that is, the higher the power generation restriction level), the smaller the upper limit of the battery discharge amount is set.

[0074] For example, when the gear position is 1st, the control device uses the discharge amount determination table of Figure 7 to determine the upper limit of the battery discharge amount to 10 kW when the power generation limit level is 0, when the engine speed is 2400 rpm, the upper limit of the battery discharge amount to 7 kW when the power generation limit level is 1, when the power generation limit level is 2, the upper limit of the battery discharge amount to 1 kW, and when the power generation limit level is 3, the upper limit of the battery discharge amount to 0 kW. In this way, even if the gear ratio and engine speed are the same, the control device determines a smaller value as the upper limit of the battery discharge amount as the power generation limit level increases stepwise.

[0075] It should be noted that the discharge amount determination table is not limited to the case where the gear position is 1st, but also applies to the cases where the gear position is 2nd to 6th. Ru The more the power is restricted, the larger the upper limit of the battery discharge amount is set, and the more the motor generator 21 can discharge the battery. Ru The more restricted the battery power is, the smaller the upper limit of the battery discharge amount is set.

[0076] A flowchart of the process of suppressing driving assistance by the control device will be specifically described with reference to Fig. 9. Fig. 9 is a flowchart showing an example of the process executed when the control device according to the embodiment determines the upper limit value of the battery discharge amount. The control device periodically executes the process shown in Fig. 9 while the hybrid vehicle 1 is traveling. In Fig. 9, "S" is used as an abbreviation for "STEP."

[0077] As shown in Fig. 9, the control device determines whether or not the driving assistance is in progress (S1). If the driving assistance is not in progress (NO in S1), the control device ends this process. On the other hand, if the driving assistance is in progress (YES in S1), the control device determines whether or not the discharge amount determination table shown in Fig. 7 and Fig. 8 has already been selected (S2).

[0078] If the control device has already selected a discharge amount determination table (YES in S2), the control device proceeds to the processing in S5, which will be described later. On the other hand, if the control device has not yet selected a discharge amount determination table (NO in S2), the control device acquires the current gear position (gear ratio) (S3). That is, if the driving assistance is started at timing t1 shown in FIG. 2, the control device acquires the gear position (gear ratio) at that time in the processing in S3, which is executed for the first time after the driving assistance is started.

[0079] The control device selects a discharge amount determination table corresponding to the acquired gear position (S4). For example, if the current gear position is 1st, the control device selects the discharge amount determination table shown in Fig. 7, and if the current gear position is 6th, the control device selects the discharge amount determination table shown in Fig. 8. Thereafter, the control device uses the selected discharge amount determination table until one driving assistance is completed (for example, the period from timing t1 to timing t2 shown in Fig. 2).

[0080] After selecting a discharge amount determination table, the control device acquires the engine speed and power generation limit level (S5). The control device determines the upper limit of the battery discharge amount based on the engine speed and power generation limit level using the selected discharge amount determination table (S6). The control device then terminates this process.

[0081] After determining the upper limit of the battery discharge amount through the process shown in FIG. 9, the control device performs driving assistance within a range that does not exceed the determined upper limit.

[0082] As described above, the hybrid vehicle 1 determines the upper limit of the battery discharge amount based on the engine speed and gear ratio, and controls the battery discharge amount to be less than the upper limit during driving assistance. By controlling the battery discharge amount based on the engine speed and gear ratio, the hybrid vehicle 1 can adjust the battery discharge amount during driving assistance more finely while taking driving performance into consideration than when controlling the battery discharge amount based only on vehicle speed, and therefore can suppress a decrease in the battery charge amount without significantly degrading driving performance.

[0083] The hybrid vehicle 1 increases the upper limit of the battery discharge amount when the engine speed at which an improvement in acceleration can be expected is lower, thereby preventing excessive suppression of driving assistance during driving at which an improvement in acceleration can be expected.

[0084] When the gear ratio at which improved acceleration can be expected is larger, the hybrid vehicle 1 increases the upper limit of the battery discharge amount, thereby preventing excessive suppression of driving assistance during driving at which improved acceleration can be expected.

[0085] The hybrid vehicle 1 can stop the driving assistance by setting the upper limit of the battery discharge amount to 0.

[0086] Hybrid vehicle 1 has the following characteristics: engine speed, gear ratio, and , release Since the battery discharge amount is determined based on the power generation limit level, it is possible to prevent the charge amount of the high-voltage battery 23 from continuously decreasing due to power generation limiting.

[0087] The hybrid vehicle 1 determines the battery discharge amount based on the temperature of the high-voltage battery 23 in addition to the engine speed and gear ratio, so it is possible to prevent the charge amount of the high-voltage battery 23 from continuing to decrease due to power generation restrictions.

[0088] The hybrid vehicle 1 determines the battery discharge amount based on the current input and output to the high-voltage battery 23 in addition to the engine speed and gear ratio, so it can prevent the charge amount of the high-voltage battery 23 from continuing to decrease due to power generation restrictions.

[0089] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0090] 1 Hybrid vehicle, 11 Engine, 11A Crankshaft, 12 Transmission, 13 Cylinder, 15 Fuel injector, 16 First pulley, 17 Transmission belt, 18 Second pulley, 19 Starter, 21 Motor generator, 21A Rotating shaft, 22 Inverter, 23 High voltage battery, 25 DC / DC converter, 26 Low voltage battery, 27 Auxiliary equipment, 28 Battery management system, 30 Drive wheels, 41 Crank angle sensor, 42 Temperature sensor, 43 Motor current sensor, 51 Vehicle ECU, 52 Engine ECU, 53 Motor ECU.

Claims

1. Drive wheels and a transmission coupled to the drive wheels; an engine coupled to the transmission for generating torque for the drive wheels; A battery, a motor generator that generates torque for the drive wheels using the electric power supplied from the battery; a control device that controls the electric power supplied from the battery to the motor generator to be less than an upper limit value; a temperature sensor for measuring the temperature of the battery; The control device storing a plurality of discharge amount determination tables in which the upper limit value is determined and which correspond to a plurality of gear ratios of the transmission; selecting a discharge amount determination table corresponding to a current gear ratio of the transmission from among the plurality of discharge amount determination tables; The hybrid vehicle determines the upper limit value based on the engine speed and the measurement value of the temperature sensor using the selected discharge amount determination table.

2. 2. The hybrid vehicle according to claim 1, wherein the control device determines a larger value as the upper limit when the rotation speed is a first rotation speed than when the rotation speed is a second rotation speed that is larger than the first rotation speed.

3. 3. The hybrid vehicle according to claim 1, wherein the control device determines a smaller value as the upper limit when the gear ratio is a first gear ratio than when the gear ratio is a second gear ratio that is larger than the first gear ratio.

4. The hybrid vehicle according to any one of claims 1 to 3, wherein the upper limit value includes 0.

5. the motor generator generates electric power using the driving force of the drive wheels and supplies the generated electric power to the battery; The control device determining a power generation limit level indicating a degree of limit on power generation by the motor generator in accordance with the state of the battery based on the measurement value of the temperature sensor; 5. The hybrid vehicle according to claim 1, wherein the upper limit value is determined based on the engine speed and the power generation limit level.

6. A drive wheel; a transmission coupled to the drive wheels; an engine coupled to the transmission for generating torque for the drive wheels; A battery, a motor generator that generates torque for the drive wheels using the electric power supplied from the battery; a control device that controls the electric power supplied from the battery to the motor generator to be less than an upper limit value; a current sensor for measuring a current input / output to / from the battery; The control device storing a plurality of discharge amount determination tables in which the upper limit value is determined and which correspond to a plurality of gear ratios of the transmission; selecting a discharge amount determination table corresponding to a current gear ratio of the transmission from among the plurality of discharge amount determination tables; The hybrid vehicle determines the upper limit value based on the engine speed and the measurement value of the current sensor using the selected discharge amount determination table.

7. The motor generator supplies the battery with electric power generated using the driving force of the drive wheels, The control device determining a power generation limit level indicating a degree of limit on power generation by the motor generator in accordance with the state of the battery based on the measurement value of the current sensor; The hybrid vehicle according to claim 6, wherein the upper limit value is determined based on the engine speed and the power generation limit level.

Images