Hybrid vehicles

Abstract

To restrain excess current without limiting torque of MG excessively in a hybrid vehicle which comprises an engine and an MG (motor generator) connected to the engine.SOLUTION: In a hybrid vehicle which comprises an engine and an MG connected to the engine, a control device executes motor torque limit control which controls so that torque of the MG does not exceed limit torque at a prescribed operation period. The control device calculates actual torque of the MG per operation period and calculates jet torque of the engine and calculates resistance torque of the engine and presumes rotational speed of the MG after the operation period has elapsed by using total amount torque which sums the actual torque of the MG and the jet torque of the engine and the resistance torque of the engine, and calculates a value obtained by dividing a predetermined excess current threshold value by the rotational speed of the MG after the operation period has elapsed as the limit torque of the MG.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a hybrid vehicle including an engine and a motor generator connected to the engine. [Background technology]

[0002] Japanese Patent Publication No. 2008-247273 (Patent Document 1) discloses a technology for preventing a phenomenon (hereinafter also referred to as "overcurrent") in which the current flowing through the power supply circuit to the motor generator exceeds an overcurrent threshold by increasing the power generated by the motor generator to reduce a power balance imbalance when the rotational speed of the motor generator suddenly drops due to a decrease in engine torque in a hybrid vehicle equipped with an engine and a motor generator connected to the engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-247273 Summary of the Invention [Problem to be solved by the invention]

[0004] In a hybrid vehicle equipped with a motor generator connected to an engine, the motor generator rotates in conjunction with the rotation of the engine. Therefore, if the engine rotation speed increases while the motor generator is outputting high torque, the rotation speed of the motor generator also increases, causing the motor generator to enter a high-torque and high-speed state, which may temporarily cause an overcurrent.

[0005] Engine torque includes the injection torque that the engine outputs when fuel is injected into the engine, and the resistance torque (friction torque and pumping torque) that acts as a resistance to engine rotation. Because these torques pulsate with engine rotation, there is a risk of temporary overcurrent occurring depending on the magnitude (amplitude) of the pulsation of the injection torque and resistance torque. If the torque of the motor-generator is excessively limited in order to suppress temporary overcurrent caused by engine torque pulsation, there is a concern that the performance of the motor-generator may not be effectively utilized.

[0006] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to suppress overcurrent in a hybrid vehicle having an engine and a motor generator connected to the engine without excessively restricting the torque of the motor generator. [Means for solving the problem]

[0007] (1) A hybrid vehicle according to the present disclosure includes an engine, a motor generator connected to the engine, and a control device that executes limit control at a predetermined calculation period to control the motor generator so that the torque of the motor generator does not exceed a limit torque. For each calculation period of the limit control, the control device calculates the actual torque of the motor generator, calculates the injection torque output by the engine by injecting fuel into the engine, calculates the resistance torque that acts as resistance to engine rotation, estimates the rotation speed of the motor generator after a predetermined time has elapsed using a total torque that is the sum of the actual torque, the injection torque, and the resistance torque, calculates the limit torque of the motor generator by dividing a predetermined overcurrent threshold by the rotation speed of the motor generator after the predetermined time has elapsed, and controls the torque of the motor generator so that the torque of the motor generator does not exceed the limit torque.

[0008] According to the above configuration, the pulsating injection torque and resistance torque of the engine are calculated for each calculation cycle of the limit control, and the results are used to calculate the limit torque of the motor-generator. This allows the limit torque of the motor-generator to accurately follow the pulsation of the engine torque, thereby suppressing overcurrent without excessively limiting the torque of the motor-generator in anticipation of the pulsation of the engine torque.

[0009] (2) In one aspect, the predetermined time is a calculation period. The control device, at a first timing during execution of limit control, estimates the rotational speed of the motor-generator at a second timing, which is the calculation period after the first timing, using a value obtained by multiplying the rotational acceleration of the motor-generator by the calculation period, and calculates the limit torque of the motor-generator using a value obtained by dividing the overcurrent threshold by the rotational speed of the motor-generator at the second timing.

[0010] According to the above configuration, at a first timing during execution of limit control, the rotation speed of the motor-generator at the next calculation timing, that is, a second timing, is estimated in advance, and the result is used to calculate the limit torque of the motor-generator. Therefore, at each calculation timing of limit control, it is possible to suppress overcurrent without excessively limiting the torque of the motor-generator.

[0011] (3) In one aspect, the control device further includes a current sensor that detects a current of the motor generator, and calculates the torque of the motor generator based on the output of the current sensor.

[0012] According to the above configuration, the actual torque of the motor generator can be calculated in real time based on the output of the current sensor.

[0013] (4) In one aspect, the engine control device further includes a rotation speed sensor that detects the rotation speed of the engine. The control device calculates the injection torque based on the output of the rotation speed sensor and the amount of fuel injected into the engine.

[0014] According to the above configuration, the injection torque of the engine can be calculated in real time based on the output of the rotational speed sensor and the amount of fuel injected into the engine.

[0015] (5) In one aspect, the engine control device further includes a water temperature sensor that detects the temperature of engine coolant and an atmospheric pressure sensor. The control device calculates the resistance torque based on the outputs of the water temperature sensor and the atmospheric pressure sensor.

[0016] According to the above configuration, the resistance torque can be calculated in real time based on the output of the water temperature sensor and the output of the atmospheric pressure sensor.

[0017] (6) In one aspect, the calculation period is set to a value shorter than the period of fuel injection into the engine.

[0018] According to the above configuration, the limit torque of the motor generator is calculated at least once within the fuel injection cycle, which allows the limit torque of the motor generator to more accurately follow the engine torque that pulsates within the fuel injection cycle. [Effects of the Invention]

[0019] According to the present disclosure, in a hybrid vehicle including an engine and a motor generator connected to the engine, it is possible to suppress overcurrent without excessively restricting the torque of the motor generator. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a hybrid vehicle. [Figure 2] FIG. 4 is a diagram showing an example of changes in MG rotation speed, MG torque, and engine torque when the engine is started. [Figure 3] 4 is a flowchart showing an example of a processing procedure when the control device executes motor torque limit control. [Figure 4]FIG. 4 is a diagram for explaining a method for calculating an MG limit torque. DETAILED DESCRIPTION OF THE INVENTION

[0021] 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.

[0022] <Overall structure> 1 is a diagram showing a schematic configuration of a hybrid vehicle 1 according to this embodiment. The hybrid vehicle 1 includes an internal combustion engine 11, a transmission 12, a motor generator 21, 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.

[0023] One end of a crankshaft 11A of the engine 11 is connected to a drive wheel (not shown) via a transmission 12 and the like. The engine 11 has a plurality of cylinders 13, each of which is provided with a fuel injection valve 15. The engine 11 is, for example, a diesel engine, and fuel is supplied to each fuel injection valve 15 via a common rail (not shown) and a fuel pipe (not shown). Each fuel injection valve 15 is driven by a control signal from the engine ECU 52 and injects fuel into the corresponding cylinder 13.

[0024] 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 or the like for generating hydraulic pressure via a belt, pulley, gear (sprocket), chain, or the like.

[0025] The engine 11 is provided with a crank angle sensor 41, a coolant temperature sensor 42, and the like. 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 engine rotation speed from the output of the crank angle sensor 41. The coolant temperature sensor 42 is attached to an outlet of a water jacket (not shown) of the engine 11, and outputs a detection signal corresponding to the coolant temperature of the coolant circulating through the water jacket to the vehicle ECU 51.

[0026] The hybrid vehicle 1 is also provided with an atmospheric pressure sensor 45. The atmospheric pressure sensor 45 outputs a detection signal corresponding to the atmospheric pressure around the hybrid vehicle 1 to the vehicle ECU 51. Although not shown, the hybrid vehicle 1 is also provided with various sensors that detect physical quantities required for driving the hybrid vehicle 1, such as an accelerator position sensor that detects the amount of accelerator pedal operation by the driver, a vehicle speed sensor that detects the vehicle speed, etc.

[0027] 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. The motor generator 21 also has the function of cranking the engine 11 in place of the starter motor 19.

[0028] When the motor generator 21 functions as an electric motor, it applies rotational torque to the second pulley 18, and the rotational torque is input to the crankshaft 11A of the engine 11 via the transmission belt 17 and the first pulley 16. In this case, the motor generator 21 assists the driving of the engine 11. On the other hand, when the motor generator 21 functions as a generator, the rotational torque of the crankshaft 11A of the engine 11 is input to the rotating shaft 21A of the motor generator 21 via the first pulley 16, the transmission belt 17, and the second pulley 18. The motor generator 21 generates electricity in response to the rotation of the rotating shaft 21A.

[0029] 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, and in accordance with a control signal from the motor ECU 53, converts the AC voltage generated by the motor generator 21 into a DC voltage and outputs it to the high-voltage battery 23, and converts the DC voltage output by the high-voltage battery 23 into an AC voltage and outputs it to the motor generator 21.

[0030] The motor generator 21 is also provided with a current sensor (hereinafter referred to as "MG current sensor") 43 that detects 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 MG current sensor 43 is configured to detect the current of each phase of the motor generator 21. The motor generator 21 is also provided with a sensor (not shown) that detects the rotational speed of the motor generator 21 (hereinafter also referred to as "MG rotational speed Nm").

[0031] The high-voltage battery 23 is, for example, a 48 V lithium-ion battery. The high-voltage battery 23 is not limited to a lithium-ion battery, and other secondary batteries (for example, nickel-metal hydride batteries) or all-solid-state secondary batteries may be used.

[0032] When the motor generator 21 functions as an electric motor, the high-voltage battery 23 supplies power to the motor generator 21. When the motor generator 21 functions as a generator, the high-voltage battery 23 is charged by receiving power from the motor generator 21. The current value, voltage value, state of charge (SOC), etc. of the high-voltage battery 23 are detected by a battery management system (BMS) 28 and output to the vehicle ECU 51.

[0033] A DC / DC converter 25 is connected to the motor generator 21 via an inverter 22. The DC / DC converter 25 is also connected to a high-voltage battery 23. The DC / DC converter 25 steps down the DC voltage output from the inverter 22 and the high-voltage battery 23 to 12 V to 15 V and outputs the stepped-down voltage. A low-voltage battery 26 is connected to the DC / DC converter 25.

[0034] 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. When the output voltage of the DC / DC converter 25 is higher than the open circuit voltage (OCV) of the low-voltage battery 26, the low-voltage battery 26 is charged by receiving power from the DC / DC converter 25.

[0035] Various accessories (vehicle electrical equipment) 27 are connected to the DC / DC converter 25 and the low-voltage battery 26. Examples of the accessories 27 include lighting-related components such as vehicle headlights, turn signals, and interior lights, as well as interior equipment such as a car navigation system and speakers. When the DC / DC converter 25 is not operating, the accessories 27 receive power from the low-voltage battery 26. When the output voltage of the DC / DC converter 25 is higher than the open-circuit voltage (OCV) of the low-voltage battery 26, the accessories 27 receive power from the DC / DC converter 25.

[0036] In addition, a starter motor 19 is connected to the DC / DC converter 25 and the low-voltage battery 26 as one of the accessories 27. The starter motor 19 is a DC motor, and an output shaft of the starter motor 19 is connected to the crankshaft 11A of the engine 11. The starter motor 19 is driven by power supplied from the low-voltage battery 26 and the DC / DC converter 25.

[0037] Each of the vehicle ECU 51, the engine ECU 52, and the motor ECU 53 includes a CPU (Central Processing Unit) as a computing device, a storage device, and an input / output port for inputting and outputting various signals (none of which are shown). The storage device includes a RAM (Random Access Memory) as a working memory, and a storage device (a rewritable nonvolatile memory such as a ROM (Read Only Memory) or an EEPROM).

[0038] 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 processed by dedicated hardware (electronic circuits).

[0039] 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 then 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 actual torque output by the motor generator 21 will also be referred to as "MG torque Tm," and the torque demand value for the motor generator 21 will also be referred to as "MG demand torque."

[0040] The motor ECU 53 controls the supply of power to the motor generator 21 via the inverter 22 based on the MG required torque input from the vehicle ECU 51. More specifically, the motor ECU 53 sets the MG command torque based on the MG required torque, and controls the inverter 22 so that the MG torque Tm becomes the MG command torque.

[0041] The engine ECU 52 performs operation control (fuel injection control, etc.) of the engine 11 based on the output requirement value input from the vehicle ECU 51. For example, when a control signal for a fuel injection amount is input from the vehicle ECU 51, the engine ECU 52 controls the fuel injection valve 15 so as to inject the input fuel injection amount into the cylinder 13. That is, 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. Hereinafter, the torque output by the engine 11 by injecting fuel into the engine 11 will also be referred to as "injection torque Tf."

[0042] Furthermore, when a request to start the engine 11 is made while the engine 11 is stopped, the vehicle ECU 51 starts the engine 11 by cranking the engine 11 with the starter motor 19 or the motor generator 21. Specifically, the vehicle ECU 51 cranks the engine 11 with the starter motor 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.

[0043] The vehicle ECU 51, engine ECU 52, and motor ECU 53 according to this embodiment are an example of a "control device" of the present disclosure. In this embodiment, the control device is divided into three parts, namely, the vehicle ECU 51, the engine ECU 52, and the motor ECU 53, but the control device is not necessarily limited to being divided into three parts. In other words, 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 50" without distinction.

[0044] <Motor torque limit control (suppression of overcurrent)> In the hybrid vehicle 1, as described above, the rotating shaft 21A of the motor generator 21 is connected to the crankshaft 11A of the engine 11 via the transmission belt 17, and therefore the motor generator 21 rotates integrally with the engine 11. Therefore, if the engine rotation speed increases while the motor generator 21 is outputting high torque, the MG rotation speed Nm also increases, causing the motor generator 21 to enter a high-torque and high-speed state, which may cause an "overcurrent" in which the current flowing through the power supply circuit to the motor generator 21 (hereinafter also referred to as the "high-voltage system") temporarily exceeds the overcurrent threshold. In particular, when the engine 11 is started while the motor generator 21 is operating, an overcurrent is likely to occur due to a sudden increase in the injection torque Tf.

[0045] Fig. 2 is a diagram showing an example of changes in MG rotation speed Nm, MG torque Tm, and torque of engine 11 when starting engine 11. Note that the torque of engine 11 includes not only injection torque Tf that contributes to an increase in engine rotation speed, but also torque that acts as rotational resistance of engine 11 (hereinafter also referred to as "resistance torque Tr"), such as friction torque and pumping torque of engine 11. In Fig. 2, the upper graph shows changes in MG rotation speed Nm, and the lower graph shows changes in MG torque Tm and torque of engine 11 (injection torque Tf and resistance torque Tr).

[0046] The "total torque" shown in the lower graph of Fig. 2 is the sum of the MG torque Tm, the injection torque Tf, and the resistance torque Tr. The larger the total torque, the larger the engine rotation speed and the MG rotation speed Nm become.

[0047] When the engine 11 is started, the injection torque Tf, which had not been generated immediately before, is generated, causing the total torque to increase sharply to a high value. This increases the MG rotation speed Nm, which may cause an overcurrent.

[0048] Here, the injection torque Tf and resistance torque Tr of the engine 11 pulsate within one fuel injection cycle, and depending on the magnitude (amplitude) of the pulsation of the injection torque Tf and resistance torque Tr, the current flowing through the high-voltage system may temporarily exceed the overcurrent threshold, causing an overcurrent. If the MG command torque is set to a value that is excessively smaller than the MG required torque in order to suppress this overcurrent, the MG torque Tm may be excessively limited, which may result in a deterioration in the startability of the engine 11. Note that this problem may occur not only when the engine 11 is started, but also while the engine 11 is running.

[0049] In order to solve the above problems, the control device 50 according to this embodiment calculates, apart from the MG required torque, an upper limit torque of the motor generator 21 for suppressing overcurrent (hereinafter also referred to as "MG limit torque") so as to follow the pulsation of the engine torque (transient changes in the injection torque Tf and the resistance torque Tr), and periodically executes a process (hereinafter also referred to as "motor torque limit control") to limit the MG required torque so that it does not exceed the MG limit torque at a calculation period Δt.

[0050] In this case, it is desirable to set the calculation period Δt of the motor torque limit control to a value shorter than the fuel injection period (for example, a value less than one-fourth of the fuel injection period) so that the MG limit torque accurately follows the pulsation of the engine torque. Note that, in view of the fact that the fuel injection period (the time it takes for the crankshaft to make a half rotation in the case of a four-stroke engine) varies depending on the engine rotation speed, the calculation period Δt may be varied in real time according to the fuel injection period, or may be fixed to a value shorter than the expected minimum value of the fuel injection period (for example, approximately several tens of microseconds).

[0051] 3 is a flowchart showing an example of a processing procedure when the control device 50 executes motor torque limit control. The motor torque limit control is executed periodically at the above-mentioned calculation period Δt. The calculation period Δt is set to a value shorter than the fuel injection period of the engine 11 (for example, a value less than one-fourth of the fuel injection period). The calculation period Δt may be a variable value or a fixed value as described above, but FIG. 3 assumes that the calculation period Δt is a fixed value (for example, approximately several tens of microseconds).

[0052] First, the control device 50 calculates the MG torque Tm based on the output of the MG current sensor 43 (step S11). For example, a map that defines the correspondence relationship between the output of the MG current sensor 43 and the MG torque Tm is stored in advance in the storage of the control device 50. The control device 50 calculates the MG torque Tm that corresponds to the output of the MG current sensor 43 by referring to this map.

[0053] Next, the control device 50 calculates the injection torque Tf of the engine 11 (step S12). For example, the control device 50 calculates the injection torque Tf at time t using the following equation (1).

[0054] Tf=A0+A1·sin(ωt+φ1)+A2·sin(2ωt+φ2)…(1) Each of "A0," "A1," "A2," "ω," "φ1," and "φ2" in Equation (1) can be determined using the fuel injection amount and the engine rotation speed as parameters. For example, a map defining the correspondence between each of "A0," "A1," "A2," "ω," "φ1," and "φ2" and the fuel injection amount and the engine rotation speed is stored in advance in the storage of the control device 50. The control device 50 refers to this map to calculate "A0," "A1," "A2," "ω," "φ1," and "φ2" corresponding to the fuel injection amount and the engine rotation speed, and calculates the injection torque Tf by substituting the calculated value into Equation (1) above. This allows the injection torque Tf to be calculated accurately by following the pulsation of the actual injection torque.

[0055] Next, the control device 50 calculates the resistance torque Tr of the engine 11 (step S13). For example, the control device 50 calculates the resistance torque Tr at time t using the following equation (2).

[0056] Tr=B0+B1·sin(ωt+φ1') …(2) Each of "B0," "B1," and "φ1'" in equation (2) can be determined using the engine water temperature and the outside air pressure as parameters. For example, a map defining the correspondence between each of "B0," "B1," and "φ1'" and the engine water temperature and the outside air pressure is pre-stored in the storage of the control device 50. The control device 50 refers to this map to calculate "B0," "B1," and "φ1'" corresponding to the engine water temperature and the outside air pressure, and calculates the resistance torque Tr by substituting the calculated value into the above equation (2). This allows the resistance torque Tr to be calculated accurately by following the pulsation of the actual resistance torque. Note that the resistance torque Tr calculated by equation (2) is a positive value representing the magnitude (absolute value) of the torque that acts as a rotational resistance of the engine 11.

[0057] Next, the control device 50 calculates the total torque by adding up the MG torque Tm, the injection torque Tf, and the resistance torque Tr (step S14). Specifically, the control device 50 calculates the total torque using the following equation (3).

[0058] Total torque = Tm + Tf - Tr ... (3) Next, the control device 50 estimates the rotational acceleration of the motor generator 21 (hereinafter also referred to as "MG rotational acceleration ΔNm") using the total torque calculated in step S14 (step S15). For example, the control device 50 calculates the MG rotational acceleration ΔNm by dividing the total torque by the weight (moment of inertia) of the motor generator 21. The MG rotational acceleration ΔNm is the amount of change in the MG rotational speed Nm per unit time.

[0059] Next, the control device 50 calculates the MG rotational speed Nm after the calculation period Δt has elapsed, using a value obtained by multiplying the MG rotational acceleration ΔNm calculated in step S15 by the calculation period Δt.i+1 Specifically, the control device 50 estimates the MG rotation speed Nm after the calculation period Δt has elapsed using the following equation (4): i+1 Calculate.

[0060] Nm i+1 =Nm i +Δt·ΔNm …(4) In equation (4), "Nm i " is the current calculation time t i MG rotation speed, and "Δt·ΔNm" is the value obtained by multiplying the MG rotation acceleration ΔNm by the calculation period Δt.

[0061] Next, the control device 50 calculates the MG rotation speed after the calculation period Δt has elapsed by setting a predetermined overcurrent threshold. Speed ​​Nm i+1 The value obtained by dividing by is calculated as the MG limit torque (step S17).

[0062] Next, the control device 50 calculates the MG required torque based on the accelerator pedal operation amount and the MG rotation speed determined by the vehicle speed, etc. (step S20).

[0063] Next, the control device 50 determines whether the MG required torque calculated in step S20 is equal to or less than the MG limit torque calculated in step S17 (step S30).

[0064] If the MG required torque is equal to or less than the MG limit torque (YES in step S30), the control device 50 sets the MG command torque to the MG required torque (step S40), thereby controlling the MG torque Tm to become the MG required torque.

[0065] On the other hand, if the MG required torque exceeds the MG limit torque (NO in step S30), the control device 50 sets the MG command torque to the MG limit torque (step S50), thereby limiting the MG torque Tm to the MG limit torque which is lower than the MG required torque.

[0066] FIG. 4 is a diagram for explaining a method for calculating the MG limit torque in the motor torque limit control described above.

[0067] calculation time t i At the calculation time t, the MG rotation acceleration ΔNm is calculated from the total torque (the sum of the MG torque Tm, the injection torque Tf, and the resistance torque Tr). i MG rotation speed Nm i The value added to the calculation period Δt is i+1 )MG rotation speed Nm i+1 It is calculated as:

[0068] Since an overcurrent can be determined by the product of the torque and rotation speed of the motor generator 21, the predetermined overcurrent threshold is calculated by multiplying the MG rotation speed Nm after the calculation period Δt has elapsed. i+1 The value divided by is calculated as the MG limit torque.

[0069] If the MG torque Tm exceeds the MG limit torque, the current flowing through the high-voltage system will exceed the overcurrent threshold, causing an overcurrent, so the MG command torque is limited so as not to exceed the MG limit torque. In the example shown in FIG. 4, the MG required torque exceeds the MG limit torque, so the MG command torque is set to the MG limit torque instead of the MG required torque. This limits the MG torque Tm so that it does not exceed the MG limit torque.

[0070] This motor torque limit control is repeated at a calculation period Δt that is shorter than the fuel injection period, so that the MG limited torque accurately follows the pulsation of the engine torque. As a result, the MG torque Tm is not excessively limited, and overcurrent can be suppressed.

[0071] As described above, the control device 50 according to this embodiment calculates the pulsating injection torque Tf and resistance torque Tr for each calculation period Δt, and calculates the MG limited torque using the results. This allows the MG limited torque to accurately follow the pulsation of the engine torque, thereby suppressing overcurrent without excessively limiting the MG torque Tm in anticipation of the pulsation of the engine torque.

[0072] In particular, in this embodiment, the calculation cycle Δt of the motor torque limit control is set to a value shorter than the fuel injection cycle, which allows the MG limit torque to more accurately follow the engine torque that pulsates within one fuel injection cycle.

[0073] 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]

[0074] 1 Hybrid vehicle, 11 Engine, 11A Crankshaft, 12 Transmission, 13 Cylinder, 15 Fuel injection valve, 16 First pulley, 17 Transmission belt, 18 Second pulley, 19 Starter motor, 21 Motor generator, 21A Rotating shaft, 22 Inverter, 23 High voltage battery, 25 Converter, 26 Low voltage battery, 27 Auxiliary equipment, 41 Crank angle sensor, 42 Coolant temperature sensor, 43 Current sensor, 45 Atmospheric pressure sensor, 51 Vehicle ECU, 52 Engine ECU, 53 Motor ECU.

Claims

1. The engine and a motor generator connected to the engine; a control device that executes limit control to control the motor generator so that the torque of the motor generator does not exceed a limit torque at a predetermined calculation period; The control device, for each calculation period of the limit control, Calculating an actual torque of the motor generator; calculating an injection torque output by the engine by injecting fuel into the engine; Calculating a resistance torque that acts as a resistance to rotation of the engine; a total torque obtained by adding up the actual torque, the injection torque, and the resistance torque is used to estimate a rotation speed of the motor generator after a predetermined time has elapsed; calculating a limit torque of the motor generator by dividing a predetermined overcurrent threshold by the rotation speed of the motor generator after the predetermined time has elapsed; controlling the torque of the motor generator so that the torque of the motor generator does not exceed the limit torque; A hybrid vehicle, wherein the calculation period is set to a value shorter than a fuel injection period for the engine.

2. the predetermined time is the calculation period, The control device, at a first timing during execution of the limit control, using a value obtained by multiplying the rotational acceleration of the motor generator by the calculation period, to estimate the rotational speed of the motor generator at a second timing when the calculation period has elapsed since the first timing; 2. The hybrid vehicle according to claim 1, wherein the limit torque of the motor generator is calculated using a value obtained by dividing the overcurrent threshold by the rotational speed of the motor generator at the second timing.

3. a current sensor for detecting a current of the motor generator; 3. The hybrid vehicle according to claim 1, wherein the control device calculates the torque of the motor generator based on the output of the current sensor.

4. a rotation speed sensor for detecting a rotation speed of the engine; 4. The hybrid vehicle according to claim 1, wherein the control device calculates the injection torque based on an output of the rotational speed sensor and an amount of fuel injected into the engine.

5. a water temperature sensor for detecting the temperature of the engine cooling water; an atmospheric pressure sensor, 5. The hybrid vehicle according to claim 1, wherein the control device calculates the resistance torque based on an output from the water temperature sensor and an output from the atmospheric pressure sensor.

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