Hybrid vehicle control device

Abstract

To achieve both of reduction suppression of exhaust emission performance of an engine and securing of request torque in a hybrid vehicle.SOLUTION: A control device of a hybrid vehicle 1 includes: an engine 2; a motor 30; and a control unit 10. When fuel injection amount from a fuel injection section (injector 26) is increased according to an accelerator operation of a driver, the control unit reduces recirculation amount of exhaust gas by an exhaust gas recirculation section (EGR device 20) without increasing the fuel injection amount from the fuel injection section, increases the fuel injection amount after a lapse of a prescribed time from the start of the accelerator operation, and causes the motor to output assist torque for at least the prescribed period when the fuel injection amount is not increased.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a control device for a hybrid vehicle. [Background technology]

[0002] Patent Document 1 describes a powertrain control device for a hybrid vehicle equipped with a diesel engine and a motor. When the diesel engine is determined to be in an accelerating operating state, the control device closes the EGR valve to suppress a shortage of fresh air, and gradually increases the fuel injection amount from the start of closing the EGR valve, taking into consideration the delay in the increase in the amount of fresh air drawn into the cylinder relative to the closing of the EGR valve. This suppresses the generation of smoke. In addition, the control device compensates for the torque shortage caused by the gradual increase in the fuel injection amount by the assist torque of the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-204778 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the oxygen concentration in the EGR gas changes as the amount of fuel is increased, if the fuel injection amount is gradually increased in accordance with the amount of fresh air while the EGR valve is closed, the change in the oxygen concentration in the EGR gas will result in a shortage of oxygen for the gradually increasing amount of fuel injection, resulting in a deterioration in the engine's exhaust emission performance and / or a deterioration in the engine's power performance.

[0005] The technology disclosed herein achieves both suppression of deterioration in engine exhaust emission performance and ensuring required torque in a hybrid vehicle. [Means for solving the problem]

[0006] The present disclosure relates to a control device for a hybrid vehicle. An engine that outputs a drive torque for running a vehicle; A motor that outputs an assist torque for driving the vehicle; a control unit for controlling the engine and the motor; The engine has a fuel injection unit that injects fuel into a cylinder, and an exhaust gas recirculation unit that recirculates a portion of the exhaust gas into the cylinder, When the control unit increases the amount of fuel injection from the fuel injection unit in response to the driver's accelerator operation, it reduces the amount of exhaust gas recirculated by the exhaust gas recirculation unit without increasing the amount of fuel injection from the fuel injection unit, and after a predetermined period of time has elapsed since the start of the accelerator operation, it increases the amount of fuel injection from the fuel injection unit and causes the motor to output an assist torque, at least during the predetermined period during which the amount of fuel injection is not increased.

[0007] According to this configuration, when the amount of fuel injected from the fuel injection unit is increased in response to the driver's accelerator operation, in other words, when the driver requests acceleration, the exhaust gas recirculation unit reduces the amount of exhaust gas recirculated, thereby increasing the amount of fresh air introduced into the cylinder, and ensuring an amount of oxygen in the cylinder that corresponds to the amount of fuel injected.

[0008] In the above configuration, the amount of fuel injected from the fuel injection unit is increased after a predetermined period of time has elapsed since the driver started to operate the accelerator. The amount of fuel injected is not increased while the amount of exhaust gas recirculation is being reduced. The reduction in the amount of exhaust gas recirculation is completed within the predetermined period of time, and after the predetermined period of time has elapsed, an amount of oxygen corresponding to the fuel injection amount corresponding to the driver's accelerator operation is secured in the cylinder. By increasing the amount of fuel injected after the predetermined period of time has elapsed, it is possible to avoid a shortage of oxygen for the increased amount of fuel injected. A decrease in the exhaust emission performance of the engine is suppressed.

[0009] On the other hand, during the predetermined period when the increase in the fuel injection amount is delayed, the engine drive torque is insufficient to meet the driver's request, which deteriorates the vehicle acceleration response. During the predetermined period when the fuel injection amount is not increased, the control unit causes the motor to output an assist torque. This makes up for the insufficient engine drive torque, thereby ensuring the torque required for the hybrid vehicle.

[0010] Therefore, with the above-described configuration, in a hybrid vehicle, it is possible to suppress deterioration in the exhaust emission performance of the engine while ensuring the required torque.

[0011] The control unit predicts an oxygen deficiency in the cylinder based on a required fuel injection amount corresponding to the accelerator operation and an exhaust gas recirculation amount, When the control unit predicts that there will be no shortage of oxygen, the control unit increases the fuel injection amount from the fuel injection unit to the required fuel injection amount without waiting for the predetermined period to elapse, and stops output of the assist torque from the motor. When the control unit predicts that oxygen will be insufficient, the control unit limits an increase in the amount of fuel injected from the fuel injection unit until it predicts that oxygen will not be insufficient, and causes the motor to output an assist torque while limiting the increase in the amount of fuel injected. do.

[0012] When the control unit predicts that there will be no shortage of oxygen in the cylinder, the control unit immediately increases the fuel injection amount to the required fuel injection amount and stops the motor assist torque output. The required torque can be satisfied while the exhaust emission performance of the engine is not deteriorated. Also, stopping the motor assist torque output is advantageous for improving the electric power consumption performance of the hybrid vehicle.

[0013] When the control unit predicts that there will be a shortage of oxygen in the cylinder, it limits the increase in the amount of fuel injected from the fuel injection unit. Limiting the increase in the fuel injection amount corresponds to not increasing the fuel injection amount and / or making the fuel injection amount less than the required fuel injection amount. By limiting the increase in the fuel injection amount, oxygen shortage relative to the fuel injection amount can be suppressed, thereby suppressing a deterioration in the exhaust emission performance of the engine. The control unit causes the motor to output assist torque until it predicts that there will be no shortage of oxygen, thereby ensuring the torque required for the hybrid vehicle.

[0014] The control unit switches between a first setting for setting the amount of recirculation of the exhaust gas based on a steady operating state of the engine and a second setting for setting the amount of recirculation of the exhaust gas based on a required fuel injection amount. do.

[0015] When the driver does not suddenly operate the accelerator and gentle acceleration or constant speed driving is required, the control unit sets the exhaust gas recirculation amount based on the steady operating state of the engine (i.e., the first setting). When gentle acceleration or constant speed driving is required, an amount of oxygen corresponding to the required fuel injection amount is secured in the cylinder, and the exhaust gas recirculation amount is relatively large, so that the exhaust emission performance of the engine is maintained high.

[0016] When the driver operates the accelerator suddenly and strong acceleration is required, at the beginning of acceleration, the control unit sets the amount of exhaust gas recirculation based on the required fuel injection amount. When strong acceleration is required, the boost pressure is low and the amount of air is small at the beginning of acceleration, so the amount of air is small compared to the amount of oxygen required to combust the required fuel injection amount, and the required oxygen concentration is high. The control unit sets the amount of exhaust gas recirculation to be small. If the amount of exhaust gas recirculation is reduced, the amount of fresh air increases, making it possible to increase the amount of fuel injection and increase the driving torque of the engine. As a result, the strong acceleration required by the driver is realized.

[0017] The control device for a hybrid vehicle disclosed herein comprises: An engine that outputs a drive torque for running a vehicle; A motor that outputs an assist torque for driving the vehicle; a control unit for controlling the engine and the motor; The engine has a fuel injection unit that injects fuel into a cylinder, and an exhaust gas recirculation unit that recirculates a portion of the exhaust gas into the cylinder, when the control unit increases the amount of fuel injection from the fuel injection unit in response to an accelerator operation by a driver, the control unit reduces the amount of exhaust gas recirculated by the exhaust gas recirculation unit without increasing the amount of fuel injection from the fuel injection unit, and after a predetermined period has elapsed since the start of the accelerator operation, increases the amount of fuel injection from the fuel injection unit, and causes the motor to output an assist torque at least during the predetermined period during which the amount of fuel injection is not increased; The control unit sets a first target torque that is set based on an accelerator operation by a driver, and a second target torque having a rate of change lower than a rate of change of the first target torque, The control unit causes the motor to output an assist torque so that the second target torque is achieved during the predetermined period, and increases the drive torque of the engine at a rate of change corresponding to a rate of change of the first target torque after the predetermined period has elapsed. do.

[0018] The second target torque, which has a relatively small rate of change, can be appropriately set so as to improve drivability. If the second target torque is achieved by utilizing the motor's assist torque after the driver operates the accelerator to request acceleration, the drivability of the hybrid vehicle will be improved. In addition, by utilizing the motor's assist torque, the hybrid vehicle can accelerate appropriately with high response to the driver's accelerator operation.

[0019] Furthermore, when increasing the engine drive torque after a predetermined period of time has elapsed, the control unit increases the engine drive torque at a relatively high rate of change that is equal to or greater than the rate of change of the first target torque. This causes the engine drive torque to increase quickly and reach the second target torque. Once the engine drive torque reaches the second target torque, the second target torque can be achieved without motor assist, so motor assist can be stopped. Since the reduction in the motor usage time reduces power consumption, this is advantageous for improving the fuel economy of the hybrid vehicle. Effect of the Invention

[0020] The control device for a hybrid vehicle described above can simultaneously suppress deterioration of the exhaust emission performance of the engine and ensure the required torque. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 illustrates the configuration of a hybrid vehicle. [Diagram 2] FIG. 2 illustrates the configuration of a diesel engine. [Diagram 3] FIG. 3 illustrates the configuration of a control device for a hybrid vehicle. [Figure 4] FIG. 4 illustrates a control flow of a hybrid vehicle executed by the control device. [Diagram 5] FIG. 5 is a time chart illustrating a change in torque when acceleration of a hybrid vehicle is required. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a control device for a hybrid vehicle will be described with reference to the drawings. The control device for a hybrid vehicle described here is merely an example.

[0023] (Overall configuration of hybrid vehicle 1) 1 illustrates an example of the configuration of a hybrid vehicle 1. The hybrid vehicle 1 includes an engine 2, a motor system 3, and a transmission 4. The hybrid vehicle 1 is a front-engine, rear-drive vehicle.

[0024] The engine 2 is a diesel engine that is supplied with diesel fuel. The engine 2 is installed in an engine room provided at the front of the vehicle in a so-called vertical orientation. The configuration of the engine 2 will be described in detail later.

[0025] The motor system 3 includes an electric motor 30, an inverter 31, and a battery 32. The electric motor 30 is disposed on an output shaft of the engine 2. As illustrated in FIG. 1, the electric motor 30 is disposed between the engine 2 and a transmission 4 described later. The electric motor 30 outputs a driving torque for driving the vehicle during power running, and performs regeneration to apply a braking force to the vehicle. The battery 32 is connected to the electric motor 30 via the inverter 31. The battery 32 supplies driving power to the electric motor 30, and is charged during regeneration of the electric motor 30. The inverter 31 receives a control signal from a control unit 10 described later, and supplies power from the battery 32 to the electric motor 30 during power running, and transmits the generated power of the electric motor 30 to the battery 32 during regeneration.

[0026] The transmission 4 is, for example, an automatic transmission including at least one planetary gear mechanism. However, the transmission 4 is not limited to an automatic transmission. The transmission 4 is coupled to the output shafts of the engine 2 and the electric motor 30. The transmission 4 changes the speed of the torque of the engine 2 and / or the electric motor 30 and outputs it.

[0027] A propeller shaft 51 is connected to the output shaft of the transmission 4. The propeller shaft 51 is connected to a drive shaft 53 via a differential gear 52. The drive shaft 53 is coupled to left and right rear wheels 62, which are drive wheels. The differential gear 52 adjusts the difference in rotation speed between the left and right rear wheels 62.

[0028] (Engine configuration) Fig. 2 illustrates an example of the configuration of the engine 2. The engine 2 has a plurality of cylinders 21. Note that Fig. 2 illustrates only one cylinder 21. A piston 22 is inserted into each cylinder 21. The piston 22 reciprocates within the cylinder 21. The cylinder 21 and the piston 22 form a combustion chamber.

[0029] An injector 26 is attached to the main body of the engine 2. The injector 26 is a fuel injection device that injects fuel into the cylinders 21. The injector 26 is attached to each cylinder 21.

[0030] An intake passage 23 and an exhaust passage 24 are connected to each cylinder 21 of the engine 2. The intake passage 23 guides intake air to each cylinder 21. The exhaust passage 24 guides exhaust gas discharged from each cylinder 21 to the outside of the hybrid vehicle 1.

[0031] An air cleaner 210 is disposed at the upstream end of the intake passage 23. The air cleaner 210 removes foreign matter from the intake air. In the intake passage 23, a compressor 251 of the turbocharger 25, an intake throttle valve 29, and an intercooler 211 are disposed in this order from upstream. The intercooler 211 cools the air compressed by the compressor 251. The intake throttle valve 29 throttles the intake passage 23. The intake throttle valve 29 is basically fully open.

[0032] In the exhaust passage 24, a turbine 252 of the turbocharger 25 and an exhaust purification device 212 are arranged in this order from the upstream side.

[0033] The compressor 251 and the turbine 252 of the turbocharger 25 are connected to each other. The turbine 252 rotates by the fluid energy of the exhaust gas. When the turbine 252 rotates, the compressor 251 rotates. The compressor 251 compresses the intake air.

[0034] The exhaust purification device 212 purifies harmful components in the exhaust. The exhaust purification device 212 has an oxidation catalyst and a diesel particulate filter. The oxidation catalyst promotes a reaction in which CO and HC in the exhaust are oxidized to produce CO2 and H2O. The DPF collects particulates such as soot in the exhaust. The exhaust purification device 212 may further have a catalyst for purifying NOx.

[0035] The engine 2 has an EGR device 20. The EGR device 20 recirculates a portion of the exhaust gas (i.e., EGR gas) to the intake passage 23. The EGR device 20 has an EGR passage 27 and an EGR valve 28. The EGR passage 27 connects the intake passage 23 and the exhaust passage 24. More specifically, the EGR passage 27 connects a portion of the exhaust passage 24 upstream of the turbine 252 to a portion of the intake passage 23 downstream of the intercooler 211. The EGR valve 28 is provided midway through the EGR passage 27. The EGR valve 28 adjusts the amount of recirculated EGR gas.

[0036] The following sensors are installed on engine 2 (see also Figures 1 and 3): Crank angle sensor SN1: Attached to the body of the engine 2 and outputs a measurement signal corresponding to the rotation of the crankshaft. Water temperature sensor SN2: Attached to the body of engine 2, outputs a measurement signal corresponding to the temperature of the cooling water flowing within the body of engine 2. Air flow sensor SN3: Attached to the intake passage 23 downstream of the air cleaner 210, outputs a measurement signal corresponding to the flow rate of intake air. Intake air temperature sensor SN4: Attached to the downstream of the intercooler 211 in the intake passage 23, and outputs a measurement signal corresponding to the temperature of the intake air after passing through the intercooler 211 Intake pressure sensor SN5: Attached to the surge tank of the intake passage 23, it outputs a measurement signal corresponding to the pressure of the intake air before it is introduced into the cylinder 21. Intake O2 sensor SN6: Attached to the surge tank of the intake passage 23, it outputs a measurement signal corresponding to the oxygen concentration of the intake air before it is introduced into the cylinder 21. Injection pressure sensor SN7: Attached to a supply device that supplies fuel to the injector 26, it outputs a measurement signal corresponding to the pressure of the fuel. Exhaust O2 sensor SN8: Attached to the exhaust passage 24 downstream of the turbine 252, outputs a measurement signal corresponding to the oxygen concentration in the exhaust. Differential pressure sensor SN9: Attached to the exhaust purification device 212, outputs a measurement signal corresponding to the differential pressure between the upstream end and downstream end of the DPF. Accelerator position sensor SN10: Attached to the accelerator pedal, it outputs a signal equivalent to the accelerator position depending on the amount of pressure applied to the accelerator pedal by the driver. Atmospheric pressure sensor SN11: Installed in the vehicle, it outputs a measurement signal corresponding to the atmospheric pressure. - Vehicle speed sensor SN12: Installed in the vehicle, it outputs a measurement signal corresponding to the vehicle speed.

[0037] (Configuration of a control device for a hybrid vehicle) 3 illustrates an example of the configuration of a control device for the hybrid vehicle 1. The control device includes a control unit 10. The control unit 10 is a controller based on a known microcomputer, and includes a central processing unit (CPU) 101 that executes programs, a memory 102 that is configured, for example, of a RAM (Random Access Memory) or a ROM (Read Only Memory) and that stores programs and data, and an I / F circuit 103 that inputs and outputs electric signals.

[0038] The above-mentioned sensors SN1-SN12 are connected to the control unit 10. The control unit 10 judges the running state of the hybrid vehicle 1 based on the measurement signals of these sensors. The control unit 10 outputs control signals to the injector 26, the intake throttle valve 29, the EGR valve 28, and the motor system 3. The engine 2 receives the control signal and operates to output a predetermined drive torque. The electric motor 30 receives the control signal and performs power running or regenerative braking. The torque of the engine 2, or the torque of the engine 2 and the electric motor 30, is transmitted to the rear wheels 62, and the hybrid vehicle 1 runs.

[0039] (Powertrain control in hybrid vehicles) 4 is a flowchart related to the control of the engine 2 and the motor system 3 when acceleration is required by the driver depressing the accelerator pedal. When acceleration is required, the control device of the hybrid vehicle 1 suppresses the deterioration of the exhaust emission performance of the engine 2 and ensures the required torque by utilizing the assist torque of the electric motor 30. Specifically, in order to increase the drive torque of the engine 2 in response to the request for acceleration, the control unit 10 reduces or sets to zero the opening degree of the EGR valve 28 and increases the fuel injection amount after waiting for the EGR gas introduced into the cylinder 21 to decrease with the change in the opening degree of the EGR valve 28. The control unit 10 also causes the electric motor 30 to output the assist torque while the increase in the fuel injection amount is restricted.

[0040] In step S41 after the start, the control unit 10 reads the measurement signals of the sensors SN1-SN12. In the following step S42, the control unit 10 calculates the target acceleration based on the vehicle operating conditions including the operation of the accelerator pedal. Specifically, the control unit 10 selects an acceleration characteristic map corresponding to the current vehicle speed and gear stage from among acceleration characteristic maps defined for various vehicle speeds and various gear stages, and calculates the target acceleration corresponding to the current accelerator opening degree by referring to the selected acceleration characteristic map. The acceleration characteristic map is stored in the memory 102. The calculation of the target acceleration will be described later.

[0041] In step S43, the control unit 10 calculates the input torque of the transmission 4 for realizing the target acceleration based on the set target acceleration, and further corrects this input torque to a torque that improves drivability as necessary. This torque correction will be described in detail later. In the following step S44, the control unit 10 calculates the required fuel injection amount of the engine 2 for realizing the target transmission input torque set in step S43 by the driving torque of the engine 2 alone.

[0042] After step S44, the processes of steps S45-S412 and steps S413-S416 are carried out in parallel.

[0043] Steps S413-S416 are processes related to the opening adjustment of the EGR valve 28. In step S413, the control unit 10 calculates a first target intake oxygen concentration and a second target intake oxygen concentration in the cylinder 21 based on the operating state of the engine 2 and the required fuel injection amount calculated in step S44. The first target intake oxygen concentration is an oxygen concentration (%) determined based on the steady operating state of the engine 2, and the second target intake oxygen concentration is an oxygen concentration (%) obtained by converting the amount of oxygen (g) required to achieve the required injection amount. The calculation of the first target intake oxygen concentration corresponds to the first setting, and the calculation of the second target intake oxygen concentration corresponds to the second setting. When the engine 2 is in a steady operating state, the first target intake oxygen concentration and the second target intake oxygen concentration are equal or approximately equal to each other.

[0044] Next, in step S414, the control unit 10 selects the higher of the first target intake oxygen concentration and the second target intake oxygen concentration. In other words, the control unit 10 selects the smaller opening degree of the EGR valve 28.

[0045] When the driver requests strong acceleration, the boost pressure is low at the beginning of acceleration, so the amount of air introduced into the cylinder 21 is small. The amount of air is small compared to the amount of oxygen required for combustion, and the required oxygen concentration is relatively high. In other words, the control unit 10 selects the second target intake oxygen concentration at the beginning of acceleration when the driver requests strong acceleration.

[0046] In step S415, the control unit 10 determines the EGR valve opening degree based on the target intake oxygen concentration selected in step S414. As described above, the EGR valve opening degree is set to the smaller value. In step S416, the control unit 10 adjusts the opening degree of the EGR valve 28 based on the EGR valve opening degree determined as the control value in step S415.

[0047] On the other hand, after calculating the required fuel injection amount in step S44, the control unit 10 calculates the intake oxygen concentration introduced into the cylinder 21 when combustion is performed with the required fuel injection amount at an EGR valve opening that has not reached the target opening taking into account response delay. It calculates the intake oxygen concentration when burned gas after combustion with the required fuel injection amount is recirculated to the cylinder 21 as EGR gas at an EGR valve opening that has not reached the target opening taking into account response delay. In the calculation of step S45, the influence of the delay in reduction of EGR gas with respect to the adjustment of the opening of the EGR valve 28 and the delay in supercharging of the turbocharger 25 are taken into account.

[0048] In the next step S46, the control unit 10 judges whether or not the intake oxygen concentration calculated in step S45 is predicted to be insufficient for the required fuel injection amount. If it is predicted to be insufficient, the process proceeds to step S48 and step S411. If it is predicted that there will be no oxygen shortage, the process proceeds to step S47. If it is predicted that there will be no oxygen shortage, even if fuel is injected into the cylinder 21 with the required fuel injection amount calculated in step S44, it is possible to avoid a deterioration in exhaust emission performance, such as smoke generation. Furthermore, if fuel is injected into the cylinder 21 with the required fuel injection amount, the engine 2 can output a drive torque that satisfies the target transmission input torque calculated in step S43. In other words, the assist torque of the electric motor 30 is not necessary. Therefore, the control unit 10 sets the target fuel injection amount to the required fuel injection amount calculated in step S44 in step S47, and then performs fuel injection control in step S410 to operate the engine 2. If it is predicted that there will be no oxygen shortage, the delay described below is not necessary and the fuel injection amount is increased immediately.

[0049] On the other hand, if it is predicted that there will be an oxygen deficiency, the control unit 10 delays the increase in the fuel injection amount for the engine 2 in step S48. In the following step S49, the control unit 10 calculates a target fuel injection amount. The control unit 10 calculates the target fuel injection amount based on the required fuel injection amount calculated in step S44 and an upper limit value of the fuel injection amount that does not cause an oxygen deficiency. The calculated target fuel injection amount is less than the required fuel injection amount. Thereafter, in step S410, the control unit 10 performs fuel injection control to operate the engine 2.

[0050] Furthermore, the control unit 10 calculates the assist torque of the electric motor 30 in step S411. The assist torque is set based on the target fuel injection amount calculated in step S49. Specifically, an assist torque is calculated to compensate for the torque equivalent to the difference between the required fuel injection amount calculated in step S44 and the target fuel injection amount calculated by delaying the fuel injection in step S49. After the assist torque is calculated in step S411, the control unit 10 controls the motor system 3 in the following step S412 to output the assist torque from the electric motor 30. This makes it possible to achieve the required torque by the engine 2 and the electric motor 30 while suppressing the deterioration of the exhaust emission performance of the engine 2 caused by a lack of oxygen.

[0051] The effect of the above-mentioned powertrain control will be described with reference to Fig. 5. Fig. 5 is a time chart showing an example of torque change when vehicle acceleration is required. In each of graphs 501, 502, and 503 in Fig. 5, the horizontal axis indicates time, and the vertical axis indicates target torque or actual torque.

[0052] Graph 501 is a comparative example related to a non-hybrid vehicle not equipped with a motor system. When the driver starts depressing the accelerator pedal at time t1, a target acceleration corresponding to the operation and a corresponding target torque (i.e., first target torque) 5011 are set. In graph 501, the driver requests strong acceleration, so the change rates of the target acceleration and first target torque 5011 are relatively high. However, if the change rate of the target acceleration is too high, a sudden torque change occurs and drivability decreases. Therefore, the control unit 10 reduces the change rate of the target acceleration below the change rate corresponding to the accelerator pedal depressing operation. As a result, the change rate of the target torque (i.e., second target torque) 5012 relatively decreases.

[0053] In order to achieve the second target torque 5012, it is necessary to increase the drive torque of the engine 2. In other words, the required fuel injection amount of the engine 2 increases. In order to secure an oxygen concentration that matches the required fuel injection amount, the opening of the EGR valve 28 decreases and the target boost pressure increases. However, there is a response delay in adjusting the EGR gas amount and the boost pressure. If the fuel injection amount into the cylinder 21 is immediately increased, the oxygen concentration in the cylinder 21 will be insufficient compared to the fuel injection amount due to the recirculation of exhaust gas with a low oxygen concentration. In order to maintain the exhaust emission performance of the engine 2, the fuel injection amount must be limited.

[0054] In the graph 501, the increase in the driving torque 5013 of the engine 2 is limited from time t1 to time t2. That is, the control unit 10 delays the start of the increase in the fuel injection amount from time t1 to time t2. After time t2, the driving torque 5013 of the engine 2 increases at a rate of change corresponding to the rate of change of the second target torque 5012. By setting the driving torque 5013 of the engine 2, in other words the torque of the hybrid vehicle 1, to a rate of change corresponding to the rate of change of the second target torque 5012, the jerk of the hybrid vehicle 1 becomes appropriate and the drivability is improved. In addition, in this case, the oxygen concentration corresponding to the gradually increasing fuel injection amount is secured, so that the deterioration of the exhaust emission performance of the engine 2 is suppressed. However, in the comparative example related to the non-hybrid vehicle, the increase in the torque is delayed in response to the driver's accelerator operation.

[0055] Graph 502 is an example related to the above-mentioned hybrid vehicle 1. As with graph 501, when the driver starts depressing the accelerator pedal at time t1, a target acceleration corresponding to the operation and a first target torque 5021 corresponding thereto are set, and a second target torque 5022 is set whose rate of change is lower than that of first target torque 5021. In graph 502, second target torque 5022 corresponds to a target transmission input torque.

[0056] As in the comparative example, in the embodiment, in order to maintain the exhaust emission performance, the fuel injection amount of the engine 2 is limited. The driving torque 5023 of the engine 2 cannot be increased until time t2.

[0057] In this embodiment, the assist torque of the electric motor 30 is utilized. The control unit 10 increases the assist torque 5024 of the electric motor 30 so as to follow a change in the second target torque 5022 in response to the driver's operation of the accelerator pedal. As a result, in this embodiment, the torque increases without any delay in response to the driver's operation of the accelerator pedal.

[0058] After time t2, the driving torque of the engine 2 increases. That is, a predetermined period has passed since the start of the accelerator operation (time t1), and it is determined that there is no oxygen shortage in the cylinder 21, so that the fuel injection amount from the injector 26 increases. As illustrated in the graph 502, the control unit 10 increases the driving torque 5023 of the engine 2 at a relatively high rate of change that corresponds to or is greater than the rate of change of the first target torque 5021. As described above, the opening degree of the EGR valve 28 is set according to the accelerator operation by the driver during strong acceleration. The driving torque of the engine 2 can be increased at a relatively high rate of change that corresponds to the rate of change of the first target torque 5021, and in this case, no oxygen shortage occurs with respect to the increase in the fuel injection amount. The deterioration of the exhaust emission performance is suppressed.

[0059] Since the driving torque of the engine 2 increases quickly, the driving torque of the engine 2 reaches the second target torque 5022 at time t3. At time t3, the assist torque of the electric motor 30 can be made zero. If the driving torque of the engine 2 increases quickly, the torque assist of the electric motor 30 ends quickly, which is advantageous for improving the electric fuel efficiency performance of the hybrid vehicle 1.

[0060] As a modified example, as shown in graph 503, the increase in assist torque 5034 of the electric motor 30 may be started at time t4, which is delayed by a predetermined time from the start time t1 of the accelerator operation by the driver. This makes the torque increase responsive to the accelerator operation by the driver more appropriate, improving drivability. In graph 503, reference numeral 5031 denotes a first target torque corresponding to the depression of the accelerator pedal, reference numeral 5032 denotes a second target torque having a reduced rate of change with respect to the first target torque 5031, and reference numeral 5033 denotes the drive torque of the engine 2. [Explanation of symbols]

[0061] 1 Hybrid vehicles 10. Control Unit 2 Engine 20 EGR device (exhaust gas recirculation section) 26 Injector (fuel injection part) 30 Electric Motor

Claims

1. An engine that outputs a drive torque for running a vehicle; A motor that outputs an assist torque for driving the vehicle; a control unit for controlling the engine and the motor, The engine has a fuel injection unit that injects fuel into a cylinder, and an exhaust gas recirculation unit that recirculates a portion of the exhaust gas into the cylinder, when the control unit increases the amount of fuel injection from the fuel injection unit in response to an accelerator operation by a driver, the control unit reduces the amount of exhaust gas recirculated by the exhaust gas recirculation unit without increasing the amount of fuel injection, and after a predetermined period has elapsed since the start of the accelerator operation, increases the amount of fuel injection from the fuel injection unit, and causes the motor to output an assist torque at least during the predetermined period during which the amount of fuel injection is not increased; The control unit predicts an oxygen deficiency in the cylinder based on a required fuel injection amount corresponding to the accelerator operation and an exhaust gas recirculation amount, When the control unit predicts that there will be no shortage of oxygen, the control unit increases the fuel injection amount from the fuel injection unit to the required fuel injection amount without waiting for the predetermined period to elapse, and stops output of the assist torque from the motor. When the control unit predicts that an oxygen shortage will occur, the control unit limits an increase in the fuel injection amount from the fuel injection unit until it predicts that an oxygen shortage will not occur, and causes the motor to output an assist torque while limiting the increase in the fuel injection amount; The control unit switches between a first setting for setting the amount of recirculation of the exhaust gas based on a steady operating state of the engine and a second setting for setting the amount of recirculation of the exhaust gas based on a required fuel injection amount. A control device for a hybrid vehicle.

2. An engine that outputs a drive torque for driving a vehicle; A motor that outputs an assist torque for driving the vehicle; a control unit for controlling the engine and the motor; The engine has a fuel injection unit that injects fuel into a cylinder, and an exhaust gas recirculation unit that recirculates a portion of the exhaust gas into the cylinder, when the control unit increases the amount of fuel injection from the fuel injection unit in response to an accelerator operation by a driver, the control unit reduces the amount of exhaust gas recirculated by the exhaust gas recirculation unit without increasing the amount of fuel injection, and after a predetermined period has elapsed since the start of the accelerator operation, increases the amount of fuel injection from the fuel injection unit, and causes the motor to output an assist torque at least during the predetermined period during which the amount of fuel injection is not increased; the control unit sets a first target torque corresponding to an accelerator operation by a driver and a second target torque having a rate of change lower than a rate of change of the first target torque; the control unit causes the motor to output an assist torque so that the second target torque is achieved during the predetermined period, and increases the drive torque of the engine at a rate of change corresponding to a rate of change of the first target torque after the predetermined period has elapsed. A control device for a hybrid vehicle.

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