JP2016043800A - Hybrid-vehicular internal combustion engine start control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hybrid-vehicular internal combustion engine start control apparatus capable of suppressing deterioration of fuel economy by selecting a transmission ratio with high transmission efficiency without allowing a specific component of emission to exceed a limit when cold-starting the internal combustion engine.SOLUTION: An internal combustion engine start control apparatus performs: determining a change amount of an operation point of an internal combustion engine 2 at a start on the basis of an engine temperature and required torque so that a PN that is a specific component of emission of the internal combustion engine does not exceed a limit; selecting, from among plural transmission stages of an automatic transmission 10, a transmission stage that yields the best integrated transmission efficiency that is produced by integrating respective transmission efficiency of the automatic transmission 10 and a power division mechanism 5 after changing the operation point; and changing to the selected transmission stage before starting the internal combustion engine 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal combustion engine start control device for starting an internal combustion engine provided in a hybrid vehicle.

  As a control device applied to a hybrid vehicle equipped with an automatic transmission, there is known a control device that starts an internal combustion engine after changing the gear ratio of the automatic transmission when there is a request to start the internal combustion engine (Patent Document). 1). In addition, there is Patent Document 2 as a prior art document related to the present invention.

JP 2013-159260 A JP 2013-35528 A

  Usually, in a hybrid vehicle, the engine speed and the engine torque are determined so that the internal combustion engine is operated in an optimum fuel consumption state. However, if the internal combustion engine is not warmed up, the emission may deteriorate if the engine is started in the optimum fuel consumption state. In particular, it is known that the number of particulate matter (PN) deteriorates in this situation.

  The control device of Patent Document 1 starts the internal combustion engine after changing the gear position of the automatic transmission to the low speed side (engine high rotation side), but the specific component of the emission when the internal combustion engine is unwarmed and at a low temperature In order to suppress the deterioration of the engine, the engine speed is changed to the high rotation side and the amount of change is not determined. In addition, since the control device of Patent Document 1 does not select a gear stage in consideration of the transmission efficiency of the differential mechanism and the automatic transmission, the inefficient gear stage is selected at the start of the internal combustion engine and the fuel consumption deteriorates. There is a risk.

  Accordingly, the present invention provides an internal combustion engine start control device for a hybrid vehicle capable of suppressing deterioration in fuel consumption by selecting a gear ratio with high transmission efficiency without causing a specific component of emission to exceed a limit when the internal combustion engine is started at a low temperature. Is the first purpose. The present invention also provides an internal combustion engine start control device for a hybrid vehicle capable of suppressing deterioration of fuel efficiency due to maintaining an inefficient gear ratio while reducing a specific component of emission during low temperature start of the internal combustion engine. The purpose of 2.

  A first internal combustion engine start control device according to the present invention includes an internal combustion engine, a differential mechanism to which the internal combustion engine is coupled, and a power transmission path from the differential mechanism to a drive wheel. And an operating point defined by the engine speed and engine torque of the internal combustion engine when the internal combustion engine is at a low temperature. In an internal combustion engine start control device for a hybrid vehicle that changes to a higher rotation side than at normal temperature, an operating point change amount determination that determines the amount of change of the operating point when starting the internal combustion engine based on the engine temperature and required torque And a transmission ratio in which the combined transmission efficiency obtained by combining the transmission efficiency of the differential mechanism and the transmission mechanism after the change of the operating point is the best among the transmission ratios of the transmission mechanism and the transmission mechanism Selected, those comprising a speed ratio changing means for changing to the selected gear ratio before the start of the internal combustion engine, the (claim 1).

  According to the first internal combustion engine start control device, the operating point change amount at the start of the internal combustion engine is determined based on the engine temperature and the required torque that affect the specific component of the emission of the internal combustion engine. Sometimes it can be avoided that certain components of emissions exceed the limits when starting the internal combustion engine. In addition, a gear ratio that provides the best combined transmission efficiency after the change of the operating point is selected from the gear ratios of the transmission mechanism, so that a gear ratio with high efficiency can be selected. Thereby, it is possible to prevent the specific component of the emission from exceeding the limit while suppressing deterioration in fuel consumption due to selection of an inefficient gear ratio when the internal combustion engine is started at a low temperature.

  A second internal combustion engine start control device according to the present invention includes an internal combustion engine, a differential mechanism to which the internal combustion engine is coupled, and a power transmission path from the differential mechanism to a drive wheel. And an operating point defined by the engine speed and engine torque of the internal combustion engine when the internal combustion engine is at a low temperature. In an internal combustion engine start control device for a hybrid vehicle that changes to a higher rotation side than at normal temperature, engine start means for starting the internal combustion engine while maintaining the current speed ratio of the speed change mechanism, and specification of emissions of the internal combustion engine An operating point changing means for changing the operating point to a higher rotation side as the speed ratio of the transmission mechanism is reduced, after starting the internal combustion engine, so as to reduce a component; When there is a transmission ratio that improves the combined transmission efficiency obtained by combining the transmission efficiencies of the differential mechanism and the transmission mechanism rather than maintaining the current transmission ratio of the transmission mechanism after the change, the transmission mechanism is changed to the transmission ratio. And a gear ratio changing means for changing the gear ratio.

  According to the second internal combustion engine start control device, the operating point of the internal combustion engine is changed to the higher speed side as the speed ratio of the speed change mechanism is reduced while maintaining the current speed ratio, so that the engine temperature is started at a low temperature. Sometimes certain components of emissions can be reduced as much as possible. In addition, when there is a speed ratio that improves the combined transmission efficiency after maintaining the current speed ratio after changing the operating point of the internal combustion engine, the speed ratio is changed after the start of the internal combustion engine. It can be avoided that an inefficient gear ratio is maintained later. As a result, it is possible to suppress deterioration in fuel consumption caused by maintaining an inefficient gear ratio while reducing a specific component of emission when the internal combustion engine is started at a low temperature.

  As described above, according to the first internal combustion engine start control device of the present invention, the specific component of the emission is limited while suppressing deterioration in fuel consumption caused by selecting an inefficient gear ratio when the internal combustion engine is started at a low temperature. Can be exceeded. In addition, according to the second internal combustion engine start control device of the present invention, it is possible to suppress deterioration in fuel consumption caused by maintaining an inefficient gear ratio while reducing a specific component of emission when the internal combustion engine is started at a low temperature.

The figure which showed the whole structure of the hybrid vehicle to which the internal combustion engine starting control apparatus which concerns on one form of this invention was applied. The figure which showed the action | operation engagement table | surface of the automatic transmission. The figure which showed the alignment chart (velocity diagram) of each element of the vehicle of FIG. 1 is an overall configuration diagram of an internal combustion engine. The schematic diagram of the internal structure of an internal combustion engine. The block diagram which showed the control system of the vehicle of FIG. Explanatory drawing explaining the operating point and operating area | region of an internal combustion engine. The figure which expanded and showed the VIIB part of FIG. 7A. The flowchart which showed an example of the control routine which concerns on a 1st form. The figure which showed an example of the map which calculates | requires an operating point change amount. The figure which showed synthetic | combination transmission efficiency. The timing chart which showed an example of the control result which concerns on a 1st form. The figure which showed another example of the map which calculates | requires an operating point change amount. The alignment chart for demonstrating the significance of the control which concerns on a 2nd form. The flowchart which showed an example of the control routine which concerns on a 2nd form. The figure explaining the control content of a 2nd form. The timing chart which showed an example of the control result which concerns on a 2nd form. The figure which showed an example of the map utilized for the modification of the control which concerns on a 2nd form.

(First form)
As shown in FIG. 1, the vehicle 1 is configured as a so-called hybrid vehicle in which an internal combustion engine 2 and two motor / generators 3 and 4 are provided as a driving power source. Details of the internal combustion engine 2 will be described later. The internal combustion engine 2, the first motor / generator 3, and the second motor / generator 4 are connected to a power split mechanism 5 as a differential mechanism. The power split mechanism 5 is configured as a single pinion type planetary gear mechanism, and rotates and revolves a sun gear Sn as an external gear, a ring gear Ri as an internal gear, and a pinion P meshing with these gears Sn and Ri. And a carrier Cr that is freely supported. A first motor / generator 3 is connected to the sun gear Sn, a second motor / generator 4 is connected to the ring gear Ri, and an output shaft 2a of the internal combustion engine 2 is connected to the carrier Cr.

  An automatic transmission 10 as a speed change mechanism is provided in the power transmission path on the drive wheel side of the second motor / generator 4. The automatic transmission 10 has two input shafts 11 and 12. Two clutches C1 and C2 are provided between the input shafts 11 and 12 and the intermediate shaft 15 that rotates integrally with the ring gear Ri. By appropriately operating these clutches C1 and C2, one of the two input shafts 11 and 12 can be selectively connected to the intermediate shaft 15. The automatic transmission 10 is configured by combining two planetary gear mechanisms 21 and 22 and providing two brakes B1 and B2 and a one-way clutch F1. The two sets of planetary gear mechanisms 21, 22 are combined with each other by connecting one carrier Cr1 and the other ring gear Ri2 and connecting one ring gear Ri1 and the other carrier Cr2. . The first input shaft 11 is connected to the sun gear Sn2, and the second input shaft 12 is connected to the carrier Cr1. The carrier Cr2 is connected to the output shaft 23. The carrier Cr1 and the ring gear Ri2 that are connected to each other are provided with a one-way clutch F1 that allows rotation in only one direction. The vehicle 1 includes four forward speeds and one reverse speed as shown in the operation engagement table of FIG. 2 by appropriately changing the operation states of the clutches C1 and C2 and the brakes B1 and B2 by a hydraulic device (not shown). One shift stage can be selected from a plurality of shift stages. “N” in FIG. 2 means neutral. The speed ratio (gear ratio) of each gear stage is 3.20 for first speed (1st), 1.72 for second speed (2nd), 1.00 for third speed (3rd), and fourth speed (4th). ) Is 0.67 and retraction (Rev) is 2.04. Therefore, the automatic transmission 10 can select a gear ratio set stepwise within a certain range. “◯” in FIG. 2 means an engaged state of the clutch or the brake. The alignment chart (speed diagram) of each element of the vehicle 1 when the first to fourth gears are selected is as shown in FIG. In FIG. 3, “Eng” indicates the internal combustion engine 2, “MG1” indicates the first motor / generator 3, “MG2” indicates the second motor / generator 4, “In1” indicates the first input shaft 11, “ “In2” means the second input shaft 12, and “Out” means the output shaft 23.

  As shown in FIG. 4, the internal combustion engine 2 is configured as an in-line four-cylinder spark ignition internal combustion engine in which four cylinders 25 are arranged in one direction. The internal combustion engine 2 is configured as a so-called lean burn engine, and the operation mode can be switched between lean combustion and stoichiometric combustion. Lean combustion is an operation mode that targets an air-fuel ratio that is set on the lean side of the stoichiometric air-fuel ratio. The stoichiometric combustion is an operation mode that targets a stoichiometric air-fuel ratio that is richer than the air-fuel ratio of lean combustion or an air-fuel ratio in the vicinity thereof. Switching from lean combustion to stoichiometric combustion is performed by temporarily increasing the fuel injection amount in consideration of the response delay of the intake air amount.

  As shown in FIGS. 4 and 5, an intake passage 26 and an exhaust passage 27 are connected to each cylinder 25 of the internal combustion engine 2, respectively. The intake passage 26 is opened and closed by an intake valve 26a, and the exhaust passage 27 is opened and closed by an exhaust valve 27a. Fuel is supplied to each cylinder 25 by a port injector 29, an in-cylinder injector 30, or both of them, and an air-fuel mixture introduced into the cylinder 25 is generated by an ignition plug 31 provided for each cylinder 25. It is ignited. The combustion energy of the air-fuel mixture is transmitted to the piston 32 and output to the output shaft 2a via the connecting rod 33.

  As shown in FIG. 4, the internal combustion engine 2 is provided with a turbocharger 35 that supercharges using exhaust energy. In the intake passage 26, a compressor 35a of a turbocharger 35 is provided. A throttle valve 36 that can adjust the amount of intake air is provided in the intake passage 26 upstream of the compressor 35a. An air flow meter 37 that outputs a signal corresponding to the amount of intake air is provided in the intake passage 26 upstream of the throttle valve 36. An intercooler 38 for cooling the intake air pressurized by the compressor 35a is provided in the intake passage 26 downstream of the compressor 35a.

  In the exhaust passage 27, a turbine 35b of a turbocharger 35 is provided. The exhaust passage 27 is provided with a waste gate valve mechanism 39 that bypasses the exhaust upstream of the turbine 35b downstream of the turbine 35b. The waste gate valve mechanism 39 is provided with a waste gate valve 40 capable of adjusting the flow rate of exhaust gas guided to the turbine 35b. Therefore, as a result of adjusting the exhaust flow rate flowing into the turbine 35b by controlling the opening degree of the waste gate valve 40, the supercharging pressure of the internal combustion engine 2 is adjusted. The exhaust gas that has passed through the turbine 35b or the waste gate valve 40 is released into the atmosphere after harmful substances are removed by the start converter 41 and the post-processing device 42.

  The internal combustion engine 2 is provided with an EGR device 45 that extracts a part of the exhaust gas from the exhaust passage 27 and recirculates the exhaust gas as EGR gas in the intake passage 26. The EGR device 45 includes an EGR passage 46 that extracts a part of the exhaust gas from the exhaust passage 27 as EGR gas and guides it to the intake passage 26, an EGR valve 47 that can adjust the flow rate of the EGR gas flowing through the EGR passage 46, and the EGR passage 46. And an EGR cooler 48 for cooling the flowing EGR gas. The EGR passage 46 connects the exhaust passage 27 between the start converter 41 and the aftertreatment device 42 and the intake passage 26 between the compressor 35 a and the throttle valve 36.

  As shown in FIG. 6, the control of each part of the vehicle 1 is controlled by various electronic control units (ECUs) 50, 70, and 71 that are configured as computers and provided according to functions. The HVECU 50, the MGECU 70, and the engine ECU 71 are electrically connected so that they can exchange information with each other.

  Signals from various sensors are input to the HVECU 50 provided as a main computer. For example, the HVECU 50 includes a vehicle speed sensor 51 that outputs a signal corresponding to the vehicle speed of the vehicle 1, an accelerator opening sensor 52 that outputs a signal corresponding to a depression amount of an accelerator pedal (not shown), and rotation of the first motor / generator 3. The first MG rotational speed sensor 53 that outputs a signal corresponding to the speed, the second MG rotational speed sensor 54 that outputs a signal corresponding to the rotational speed of the second motor / generator 4, and the rotational speed of the output shaft 23 of the automatic transmission 10 An output shaft rotational speed sensor 55 that outputs a signal corresponding to the output speed, a turbine rotational speed sensor 56 that outputs a signal corresponding to the rotational speed of the turbine 35 b of the turbocharger 35, and an output signal that corresponds to the supercharging pressure of the internal combustion engine 2. Supply pressure sensor 57, SOC sensor 58 that outputs a signal corresponding to the battery storage rate (not shown), and signal corresponding to the temperature of the first motor / generator 3 , A first MG temperature sensor 59 that outputs a signal, a second MG temperature sensor 60 that outputs a signal corresponding to the temperature of the second motor / generator 4, and a temperature of a first inverter (not shown) provided for the first motor / generator 3. A first INV temperature sensor 61 that outputs a signal in accordance with the second INV temperature sensor 62 that outputs a signal in accordance with the temperature of a second inverter (not shown) provided for the second motor / generator 4, and a post-processing device 42. The catalyst temperature sensor 63 outputs a signal corresponding to the temperature of the engine, the turbine temperature sensor 64 outputs a signal corresponding to the temperature of the turbine 35b of the turbocharger 35, and the signal corresponding to the temperature of the engine coolant of the internal combustion engine 2. Output signals such as a water temperature sensor 65 and a battery temperature sensor 66 that outputs a signal corresponding to the temperature of the battery are input.

  The HVECU 50 calculates torques to be generated by the first motor / generator 3 and the second motor / generator 4, and outputs a command to the MGECU 70 regarding the torques to be generated. Further, the HVECU 50 determines the operating condition of the internal combustion engine 2 and outputs a command to the engine ECU 71 regarding the operating condition of the internal combustion engine 2. Further, the HVECU 50 controls the clutches C1 and C2 and the brakes B1 and B2 of the automatic transmission 10 so that a shift stage according to a predetermined shift schedule or a shift change request by the driver can be realized. The MGECU 70 calculates a current corresponding to the torque generated by the first motor / generator 3 and the second motor / generator 4 based on the command input from the HVECU 50, and the first motor / generator 3 and the second motor / generator 4. Output current. The engine ECU 71 performs various operations on various parts of the internal combustion engine 2 such as the throttle valve 36, the port injection injector 29, the in-cylinder injection injector 30, the spark plug 31, and the waste gate valve 40 based on a command input from the HVECU 50. Control.

  The HVECU 50 calculates the required power required by the driver with reference to the output signal of the accelerator opening sensor 52 and the output signal of the vehicle speed sensor 51, and sets various modes so as to optimize the system efficiency for the required power. The vehicle 1 is controlled while switching. For example, in the low load region where the thermal efficiency of the internal combustion engine 2 decreases, the EV travel mode in which the combustion of the internal combustion engine 2 is stopped and the second motor / generator 4 is driven is selected. When the torque is insufficient with only the internal combustion engine 2, the hybrid travel mode in which the second motor / generator 4 is used as a travel drive source together with the internal combustion engine 2 is selected.

  When the hybrid travel mode is selected, the motor torque of the first motor / generator 3 is controlled so that the operating point of the internal combustion engine 2 moves along the optimum fuel consumption line L as indicated by an arrow in FIG. 7A. . The operating point of the internal combustion engine 2 is defined by the engine speed and the engine torque, and the optimum fuel consumption line L is set in advance so that the thermal efficiency of the internal combustion engine 2 is optimized. The internal combustion engine 2 of this embodiment is configured as a lean burn engine with a supercharger. For this reason, the internal combustion engine 2 selects one of the operation modes of natural intake stoichiometric combustion, natural intake lean combustion, supercharged stoichiometric combustion, and supercharged lean combustion in accordance with the operation region shown in FIG. 7A.

  The present embodiment is characterized in the start control of the internal combustion engine 2 when there is a start request for the internal combustion engine 2 during the execution of the EV traveling mode. As described above, the internal combustion engine 2 of the present embodiment is operated along the optimum fuel consumption line L in principle. For this reason, when the internal combustion engine 2 is started during execution of the EV traveling mode, it is desirable from the viewpoint of thermal efficiency, that is, fuel consumption, that the operating point after starting is located on the optimum fuel consumption line L. However, it is known that when the internal combustion engine 2 is operated on the optimum fuel consumption line L when the temperature is not warmed up, the above-described PN deteriorates. Therefore, in this embodiment, the deterioration of PN is suppressed by starting the internal combustion engine 2 according to the control routine described below.

  It is stored in the HVECU 50 of the control routine of FIG. 8 and is read out in a timely manner and repeatedly executed at predetermined intervals. In step S1, the HVECU 50 determines whether or not the current travel mode is the EV travel mode. If it is in the EV traveling mode, the process proceeds to step S2, and if not, that is, if it is in the hybrid traveling mode, the process proceeds to step S9 so that the operating point of the internal combustion engine 2 moves on the optimum fuel consumption line L (FIG. 7A). The internal combustion engine 2 is operated. In this case, as the gear position of the automatic transmission 10, a gear speed suitable for driving on the optimum fuel consumption line L is appropriately selected.

  In step S <b> 2, the HVECU 50 determines whether there is a start request for the internal combustion engine 2. The start request is generated when various conditions are satisfied, such as when the required power increases beyond the limit of the EV driving mode, or when the battery charge rate decreases and the battery needs to be charged. If there is a start request, the process proceeds to step S3. If not, the process proceeds to step S8 to continue the EV travel mode, and a speed stage suitable for the EV travel mode is appropriately selected as the speed stage of the automatic transmission 10.

  In step S <b> 3, the HVECU 50 determines whether or not the internal combustion engine 2 is performing the lean operation in which the above-described natural intake lean combustion or supercharged lean combustion is being performed and is at a low temperature. Whether or not the temperature is low is determined by the HVECU 50 referring to a signal from the water temperature sensor 65 (FIG. 6) to obtain the engine coolant temperature (engine water temperature) as the engine temperature of the internal combustion engine 2, and the engine water temperature is a predetermined low temperature. It is carried out depending on whether or not it is below the judgment value. The engine oil temperature (engine oil temperature) can also be used as the engine temperature. If it is lean and the temperature is low, the process proceeds to step S4. Otherwise, for example, if the engine water temperature is higher than the low temperature judgment value, the process proceeds to step S7. The internal combustion engine 2 is started so that the operating point is positioned on the optimum fuel consumption line L after the internal combustion engine 2 is started while selecting the stage (see point A in FIG. 7B).

  In step S4, the HVECU 50 determines an operating point change amount for changing the operating point when the internal combustion engine 2 is started. As shown in FIG. 7B, the operating point change amount is defined by the engine speed and the engine torque, and is the change amount at which the engine speed becomes higher than before the change. The operating point change amount can be grasped as the distance between the operating points before and after the change. That is, the operating point change amount corresponds to the distance between A and B or the distance between A and C. The operating point change amount is determined based on the engine water temperature and the required torque (required power) required after the internal combustion engine 2 is started. The HVECU 50 obtains the current engine water temperature and the required torque, and determines the operating point change amount so that the lower the engine water temperature is, the larger the required torque is, based on the map of FIG. The map in FIG. 9 is set so that the operating point change amount corresponding to each required torque and each engine water temperature does not exceed the limit of PN, which is a specific component of emission, through adaptation using actual machine tests or simulations. . Therefore, by determining the operating point change amount based on the map of FIG. 9, the operating point change amount is determined so as not to exceed the PN limit.

  In step S5, the HVECU 50 selects a gear stage to be used after changing the operating point of the internal combustion engine 2, and changes the gear stage of the automatic transmission 10 to the selected gear stage. The selection of the gear position is a combination of the transmission efficiency of the power split mechanism 5 and the automatic transmission 10 after the operating point is changed from among a plurality of gear speeds (first speed to fourth speed) of the automatic transmission 10. This is implemented by selecting a gear position that provides the best transmission efficiency. The specific selection method is as follows. When the operating point change amount is determined in step S4, the operating point after the change is determined, so that the combined speed ratio obtained by combining the speed ratios of the power split mechanism 5 and the automatic transmission 10 is determined as shown by the one-dot chain line in FIG. . In this case, a plurality of intersections between the curve of the combined transmission efficiency η and the alternate long and short dash line are obtained for each shift stage, and the shift stage that gives the best combined transmission efficiency η can be specified as the shift stage to be selected at the start. For example, when considering the situation where the internal combustion engine 2 is started when the shift speed before the shift is the first speed, the second speed having a combined transmission efficiency η higher than the first speed is the shift speed to be selected at the start.

  In step S6, the HVECU 50 operates the first motor / generator 3 and the like to change the operating point of the internal combustion engine 2 by an amount corresponding to the operating point change amount, and executes fuel injection and ignition to start the internal combustion engine 2.

  In the control routine of FIG. 8, the HVECU 50 functions as an operating point change amount determining means according to the present invention by executing step S4 and as a gear ratio changing means according to the present invention by executing step S5.

  FIG. 11 shows an example of the temporal change of each parameter when the internal combustion engine 2 is started at a low temperature. FIG. 11 illustrates a case where the first speed is changed to the second speed when the internal combustion engine 2 is started. When there is a start request at time t0, the shift operation of the automatic transmission 10 is started at time t1, the brake B2 is released from the first speed where the brake B2 is engaged, and the brake B1 is engaged. Switch to 2nd speed. Between the time t1 and t3 from the start to the completion of the speed change operation, the motor rotation speed of the first motor / generator 3 and the motor torque of the second motor / generator 4 are controlled from time t2 to perform synchronous control. To be implemented.

  When the start condition of the internal combustion engine 2 is established at time t4, the motor speed of the first motor / generator 3 is increased while taking the reaction force by the second motor / generator 4 to increase the engine speed. When the engine speed reaches a predetermined speed at time t5, ignition is performed and the start of the internal combustion engine 2 is completed. Upon completion of the start, the motor torque of the second motor / generator 4 is decreased to reduce the reaction force. Then, the operating point of the internal combustion engine 2 is moved while controlling the motor torques of the first motor / generator 3 and the second motor / generator 4 from time t5. At time t6, the operating point of the internal combustion engine 2 reaches the target operating point (for example, point B in FIG. 7B).

  According to the first embodiment, since the operating point change amount at the start of the internal combustion engine 2 is determined based on the engine temperature and the required torque that affect the PN of the internal combustion engine 2, the internal combustion engine 2 is controlled when the engine temperature is low. It is possible to avoid exceeding the limit when starting. In addition, since the gear stage having the best combined transmission efficiency η after the change of the operating point is selected from the plurality of gear stages of the automatic transmission 10, a gear stage with high efficiency can be selected. Thereby, it is possible to prevent the PN from exceeding the limit while suppressing deterioration in fuel consumption caused by selecting an inefficient gear position when the internal combustion engine 2 is started at a low temperature.

  In step S4 of the control routine of FIG. 8, the operating point change amount is determined based on the engine water temperature and the required torque. However, by changing the operating point of the internal combustion engine 2 by an amount corresponding to the operating point change amount, the PN limit is not exceeded. As long as the operating point change amount may be determined by other methods.

  For example, as shown in FIG. 12, the operating point change amount may be determined based on the amount of torque compensation by the second motor / generator 4. Since the PN decreases as the internal combustion engine 2 is changed to the higher rotation and lower torque side, it is desirable to increase the operating point change amount as much as possible from the viewpoint of reducing the PN, that is, to change the operating point to a lower torque side. . However, if the engine torque decreases more than necessary, the engine torque may be insufficient with respect to the required torque (see point C in FIG. 7B). However, since the vehicle 1 can compensate for the shortage by the motor torque of the second motor / generator 4, the required torque can be satisfied even if the engine torque is insufficient by the amount corresponding to the torque compensation possible amount. This makes it possible to reduce PN as much as possible while satisfying the required torque. As a specific process of the HVECU 50, first, the amount of torque compensation can be estimated from various conditions such as the battery storage rate and temperature. Then, the operating point change amount is determined based on the map shown in FIG. 12 so that the larger the torque compensation possible amount is, the larger the operating point change amount is obtained. The map in FIG. 12 is set so that the operating point change amount corresponding to each torque-compensable amount does not exceed the limit of the PN that is a specific component of emission by adaptation using an actual machine test or simulation. . Therefore, by determining the operating point change amount based on the map of FIG. 12, the operating point change amount is determined so as not to exceed the PN limit.

(Second form)
Next, a second embodiment of the present invention will be described with reference to FIGS. The second form is common to the first form except for the control content. Therefore, FIGS. 1 to 6 are appropriately referred to for the physical configuration such as the configuration of the vehicle according to the second embodiment and the control system.

  The second mode is characterized in that the gear position of the automatic transmission 10 is changed after the internal combustion engine 2 is started when the internal combustion engine 2 is not warmed up. As shown in FIG. 13, even if the operating point of the internal combustion engine 2 is the same and the rotational speed (vehicle speed) of the output shaft 23 is the same, the first motor / generator is different if the shift stage of the automatic transmission 10 is different. 3 is different as shown in the state a and the state b. In the state a, the motor rotation speed of the first motor / generator 3 is higher and the number of electric paths is larger than in the state b, so the power transmission efficiency is low. Therefore, when the internal combustion engine 2 is started during the EV travel mode and the operation is continued from the state x or the state y to the state a, the operation is continued from the state x or the state y to the state b. Therefore, fuel consumption is worsened because extra fuel injection is required. For this reason, in the second embodiment, after the internal combustion engine 2 is started, the speed is changed to a gear stage having higher transmission efficiency than the operation of the current gear stage is continued. Specifically, this control is realized by the HVECU 50 executing the following control routine of FIG.

  It is stored in the HVECU 50 of the control routine of FIG. 14, is read out in a timely manner, and is repeatedly executed at a predetermined interval. In step S21, the HVECU 50 determines whether or not the current travel mode is the EV travel mode. If the EV traveling mode is selected, the process proceeds to step S22. If not, that is, if the hybrid traveling mode is selected, the process proceeds to step S31, and the HVECU 50 moves the operating point of the internal combustion engine 2 on the optimum fuel consumption line L (FIG. 15). The internal combustion engine 2 is operated. In this case, as the gear position of the automatic transmission 10, a gear position suitable for driving on the optimum fuel consumption line L is appropriately selected.

  In step S <b> 22, the HVECU 50 determines whether there is a start request for the internal combustion engine 2. The start request is generated when various conditions are satisfied, such as when the required power increases beyond the limit of the EV driving mode, or when the battery charge rate decreases and the battery needs to be charged. If there is a start request, the process proceeds to step S23. If not, the process proceeds to step S30 to continue the EV travel mode, and a speed stage suitable for the EV travel mode is appropriately selected as the speed stage of the automatic transmission 10.

  In step S23, the HVECU 50 determines whether or not the internal combustion engine 2 is performing the lean operation in which the above-described natural intake lean combustion or supercharged lean combustion is being performed, and is at a low temperature. Whether or not the temperature is low is determined by the HVECU 50 referring to a signal from the water temperature sensor 65 (FIG. 6) to obtain the engine coolant temperature (engine water temperature) as the engine temperature of the internal combustion engine 2, and the engine water temperature is a predetermined low temperature. It is carried out depending on whether or not it is below the judgment value. The engine oil temperature (engine oil temperature) can also be used as the engine temperature. If the engine is lean and the temperature is low, the process proceeds to step S24. Otherwise, for example, if the engine water temperature is normal temperature higher than the low temperature determination value, the process proceeds to step S29. The internal combustion engine 2 is controlled so that the operating point is positioned on the optimum fuel consumption line L while selecting a gear stage suitable for normal temperature as the gear stage (see point A in FIG. 15).

  In step S24, the HVECU 50 calculates a target operating point when the internal combustion engine 2 is at a low temperature. This target operating point is an operating point that can reduce the PN to the limit (see point B in FIG. 15). A map (not shown) in which the target operating point is set for each engine water temperature by adaptation using actual machine tests and simulations, etc. It is calculated by referring to the HVECU 50. In the map, operating points that can be realized by changing the gear position of the automatic transmission 10 together with the operation of the power split mechanism 5 are set. That is, the target operating point cannot be realized only by operating the power split mechanism 5. Therefore, even if the operating point is changed to the limit of the power split mechanism 5 on the higher rotation side without changing the gear stage of the automatic transmission 10 as the gear stage is decelerated, the actual operating point is the target operating point. (See point C in FIG. 15).

  In step S <b> 25, the HVECU 50 starts the internal combustion engine 2 by executing fuel injection and ignition while maintaining the current gear position of the automatic transmission 10. In step S <b> 26, the HVECU 50 changes the operating point of the internal combustion engine 2 to the higher speed side to the limit of the power split mechanism 5 as the gear position of the automatic transmission 10 is reduced. The limit of the power split mechanism 5 which is a differential mechanism is the power split mechanism 5 such as the limit rotational speed of the pinion P, the limit rotational speed of the first motor / generator 3, the limit rotational speed of the second motor / generator, and the like. It depends on the conditions regarding each element connected to the.

  In step S27, the HVECU 50 shifts the combined transmission efficiency η (see FIG. 10), which combines the transmission efficiencies of the power split mechanism 5 and the automatic transmission 10, more than maintaining the current shift stage of the automatic transmission 10. Is determined, and if the shift stage exists, the shift stage of the automatic transmission 10 is changed to the shift stage. The determination of whether or not the combined transmission efficiency η is improved is performed by referring to the combined transmission efficiency η determined for each gear position of the automatic transmission 10 shown in FIG. 10 of the first embodiment. In step S28, the HVECU 50 shifts the operating point of the internal combustion engine 2 to the target operating point calculated in step S24 by operating the first motor / generator 3 or the like.

  In the control routine of FIG. 14, the HVECU 50 functions as an operating point changing unit according to the present invention by executing Step S26 and as a speed ratio changing unit according to the present invention by executing Step S27.

  FIG. 16 shows an example of the temporal change of each parameter when the internal combustion engine 2 is started at a low temperature. FIG. 16 illustrates a case where the second speed is changed to the first speed after the internal combustion engine 2 is started. When there is a start request at time t0 and the start condition of the internal combustion engine 2 is satisfied at time t1, the motor speed of the first motor / generator 3 is increased while the reaction force is applied by the second motor / generator 4 to increase the engine speed. To raise. When the engine speed reaches a predetermined speed at time t2, ignition is performed and the start of the internal combustion engine 2 is completed. Upon completion of the start, the motor torque of the second motor / generator 4 is decreased to reduce the reaction force.

  Thereafter, when an operating point (for example, point C in FIG. 15) that becomes the limit of the power split mechanism 5 is reached at time t3, the operation of the internal combustion engine 2 is continued at that operating point until time t7. At time t4, the shift operation of the automatic transmission 10 is started, and the second speed in which the brake B1 is engaged is switched to the first speed in which the brake B2 is engaged and the brake B1 is released. Between time t4 and time t6 from the start to completion of the speed change operation at time t4, the motor rotation speed of the first motor / generator 3 and the motor torque of the second motor / generator 4 are controlled from time t5. Synchronous control is performed. Then, the movement of the operating point of the internal combustion engine 2 is started from time t7, the operating point reaches the target operating point (for example, point B in FIG. 15) at time t8, and the series of controls is completed.

  According to the second mode, the operating point of the internal combustion engine 2 is changed to the higher rotation side as the shift stage is decelerated while maintaining the current shift stage of the automatic transmission 10, so that the engine temperature is lower. PN can be reduced as much as possible at start-up. In addition, when there is a shift stage in which the combined transmission efficiency is improved compared to maintaining the current shift stage after changing the operating point of the internal combustion engine 2, the shift stage is changed to that shift stage after the internal combustion engine 2 is started. It is possible to avoid maintaining an inefficient gear position after the start of 2. As a result, it is possible to suppress deterioration in fuel consumption due to maintaining an inefficient shift stage while reducing PN when the internal combustion engine 2 is started at a low temperature.

  In the second embodiment, the operating point of the internal combustion engine 2 is shifted to the target operating point after the shift stage of the automatic transmission 10 is changed, but the operating point is changed to the limit of the power split mechanism 5 and the amount of change is changed. It is also possible to implement control according to the following first or second modification.

(First modification)
As shown in FIG. 15, the HVECU 50 shifts the operating point of the internal combustion engine 2 on the equal power line Lp to the point C which is the limit of the power split mechanism 5, and then the lower torque and the lower rotation D than the point C. Move to point. When the operating point of the internal combustion engine 2 is shifted to the point D, the power of the internal combustion engine 2 is reduced more than the points A and C corresponding to the required power, so that torque compensation by the second motor / generator 4 is required. Therefore, the condition for shifting to the point D is that torque compensation by the second motor / generator 4 is possible. Therefore, the HVECU 50 estimates the torque-compensable amount by the above-described method, and shifts to an operating point on the lower rotation side than the target operating point when the torque-compensable amount is sufficient. As a result, the PN can be reduced as a result of the internal combustion engine 2 being operated on the lower torque side and reducing the fuel injection amount than maintaining the operating point in a state where the operating point has been shifted to the limit of the power split mechanism 5.

(Second modification)
The difference between the operating point after changing the operating point to the limit of the power split mechanism 5 and the target operating point is defined as the operating point deviation amount, and the HVECU 50 reduces the ratio of port injection as the operating point deviation amount increases. Increase the ratio of in-cylinder injection. As described above, the internal combustion engine 2 can use both the port injection injector 29 and the in-cylinder injector 30 (FIG. 5), and can arbitrarily control the ratio between the port injection and the in-cylinder injection. Therefore, the HVECU 50 refers to the calculation map shown in FIG. 17 to calculate the ratio of the port injection corresponding to the specified operating point deviation amount, and the internal combustion engine so that the fuel injection is performed with the distribution according to the calculation result. The engine 2 is controlled. Generally, in-cylinder injection is more advantageous for reducing PN than port injection, and the larger the operating point deviation amount, the larger the fuel injection amount. Therefore, the larger the operating point deviation amount as in this control, PN can be reduced by reducing the port injection rate and increasing the in-cylinder injection rate.

  The present invention can be implemented in various forms without being limited to the above forms. In the above embodiment, a lean burn engine with a supercharger is used as the internal combustion engine mounted on the vehicle, but the internal combustion engine start control device of the present invention is applied to a hybrid vehicle mounted with a naturally aspirated engine that performs stoichiometric combustion. May be applied. Further, the scope of the present invention is not limited to the illustrated driving device as long as a differential mechanism capable of changing the operating point of the internal combustion engine is provided in addition to the speed change mechanism. For example, the present invention can also be applied to a hybrid vehicle equipped with a single motor / generator. Moreover, in the said form, the automatic transmission which can select a some gear stage as a transmission mechanism is employ | adopted. However, if the gear ratio can be selected within a certain range, not only the gear ratio that can be selected within the certain range is set in a stepwise manner as in the automatic transmission of the above embodiment, but also the gear ratio that can be selected. It is also possible to implement the present invention by adopting a continuously set transmission, for example, a continuously variable transmission as the transmission mechanism.

1 Vehicle 2 Internal combustion engine 5 Power split mechanism (differential mechanism)
10 Automatic transmission (transmission mechanism)
50 HVECU (operating point change amount determining means, transmission ratio changing means, operating point changing means)

Claims (2)

A hybrid vehicle comprising an internal combustion engine, a differential mechanism to which the internal combustion engine is coupled, and a speed change mechanism that is provided in a power transmission path from the differential mechanism to a drive wheel and that can select a speed ratio within a certain range. When the internal combustion engine is started, the operating point defined by the engine speed and the engine torque of the internal combustion engine is changed to a higher rotation side than the normal temperature when the engine temperature of the internal combustion engine is low. In the internal combustion engine start control device,
Operating point change amount determining means for determining the amount of change of the operating point when starting the internal combustion engine based on the engine temperature and the required torque;
From the transmission ratios of the transmission mechanism, a transmission ratio that combines the transmission efficiency of the differential mechanism and the transmission mechanism after the change of the operating point is selected and the combined transmission efficiency is the best, and the selected transmission ratio is selected. Gear ratio changing means for changing the ratio before starting the internal combustion engine;
An internal combustion engine start control device for a hybrid vehicle, comprising: A hybrid vehicle comprising an internal combustion engine, a differential mechanism to which the internal combustion engine is coupled, and a speed change mechanism that is provided in a power transmission path from the differential mechanism to a drive wheel and that can select a speed ratio within a certain range. When the internal combustion engine is started, the operating point defined by the engine speed and the engine torque of the internal combustion engine is changed to a higher rotation side than the normal temperature when the engine temperature of the internal combustion engine is low. In the internal combustion engine start control device,
Engine starting means for starting the internal combustion engine while maintaining the current gear ratio of the transmission mechanism;
An operating point changing means for changing the operating point to a higher rotation side as the speed ratio of the transmission mechanism is reduced after the internal combustion engine is started so that a specific component of the emission of the internal combustion engine is reduced;
If there is a gear ratio that improves the combined transmission efficiency by combining the transmission efficiency of the differential mechanism and the transmission mechanism rather than maintaining the current transmission ratio of the transmission mechanism after the change of the operating point, the transmission ratio Gear ratio changing means for changing the gear ratio of the speed change mechanism;
An internal combustion engine start control device for a hybrid vehicle, comprising:

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