JP2014240210A - Engine start connection control unit of hybrid vehicle - Google Patents

Abstract

[PROBLEMS] To prevent fluctuations in driving force due to an overshoot of engine rotation speed and an increase in required time for transition when an engine is started by ignition start. When engine speed NE overshoots at the time of engine start, steps S7 and S8 are executed to engage K0 clutch 34 and to reduce engine speed NE by torque control of motor generator MG. Thus, it is possible to prevent fluctuations in the driving force due to overshoot and an increase in the required transition time. Further, since the ignition start of step S4 is executed when the remaining power SOC of the battery 44 is equal to or less than the upper limit guard value SOCupg, even when regenerative control of the motor generator MG is necessary to reduce the engine speed NE, The battery 44 is not overcharged by the regenerative control, and the engine speed NE can be appropriately reduced by the regenerative control. [Selection] Figure 5

Description

  The present invention relates to a hybrid vehicle having an engine capable of ignition start, and more particularly to an engine start connection control device when an engine connecting / disconnecting device is engaged and connected to a drive system after starting the engine by ignition start. is there.

  (a) an engine capable of starting ignition by directly injecting fuel into a cylinder in an expansion stroke and igniting; (b) an engine connecting / disconnecting device for disconnecting the engine from a drive system; There is known a hybrid vehicle having (c) a motor generator that can be selectively used as an electric motor and a generator, and (d) a battery that transfers electric power to and from the motor generator. In such a hybrid vehicle, (e) ignition start means for starting ignition of the engine that is shut off from the drive system by the engine connecting / disconnecting device, and (f) engine rotation speed by the ignition start Engine connection means for engaging the engine connecting / disconnecting device and connecting the engine to a drive system when the engine reaches a predetermined target rotational speed such as a synchronous rotational speed determined according to the vehicle speed. A connection control device has been proposed (see Patent Document 1).

JP 2009-527411 A

  However, in such an ignition start, since the engine speed increases generally in a larger gradient than when the engine is cranked and started, the engine connecting / disconnecting device is engaged by the engine connecting means and connected to the drive system. In doing so, an overshoot may occur in which the engine rotation speed greatly exceeds the target rotation speed. For this reason, when the engine connecting / disconnecting device is engaged, the driving force fluctuates due to the inertia of the engine or the like, and the drivability deteriorates, or the time required to converge to the target rotational speed and shift to engine running becomes longer. There was a problem.

  On the other hand, although not yet known, it is conceivable to engage the engine connecting / disconnecting device and reduce the engine rotation speed by controlling the torque of the motor generator. However, if regenerative control of the motor generator is required to reduce the engine speed, if the battery is fully charged, the regenerative control cannot be performed. Sometimes it becomes.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is to provide an engine rotational speed when the engine connecting / disconnecting device is engaged and connected to the drive system after starting the engine by ignition start. This is to prevent fluctuations in the driving force due to the overshoot and increase of the required transition time.

  In order to achieve such an object, the first invention provides: (a) an engine capable of starting ignition by directly injecting fuel into a cylinder in an expansion stroke and igniting the engine; (B) a hybrid vehicle having an engine connection / disconnection device that disconnects and disconnects, a motor generator that can be selectively used as an electric motor and a generator, and a battery that transfers power to and from the motor generator. Ignition starting means for starting ignition of the engine which is cut off from the drive system by the engine connecting / disconnecting device; and (c) the engine when the engine rotational speed increases and reaches the target rotational speed by the ignition start. In an engine start connection control device having an engine connecting means for engaging a connecting / disconnecting device to connect the engine to a drive system, d) When an overshoot occurs in which the engine speed exceeds the target speed when the engine is started, the engine connecting / disconnecting device is engaged and the engine rotation is controlled by torque control of the motor generator including regenerative control. Overshoot suppression means for reducing the speed, and (e) ignition for starting the engine by a starting method other than the ignition starting when the remaining power storage amount of the battery exceeds a predetermined upper limit guard value And start restriction means.

  According to a second aspect of the present invention, in the engine start connection control device for a hybrid vehicle according to the first aspect, (a) the target rotational speed is a synchronous rotational speed determined according to a vehicle speed, and (b) the overshoot suppressing means includes the When the engine rotation speed exceeds the synchronous rotation speed, the engine connection speed is reduced by slip engagement of the engine connecting / disconnecting device, and driving force fluctuations caused by the decrease in the engine rotation speed are reduced by the motor generator. Absorbing is performed by torque control.

  In such an engine start connection control device for a hybrid vehicle, when the engine rotation speed exceeds the target rotation speed and overshoots when the engine is started, the engine connecting / disconnecting device is engaged and the engine generator torque control is performed. Since the rotational speed is reduced, it is possible to prevent fluctuations in the driving force due to overshoot and an increase in the required transition time. In this case, since the ignition start is executed when the remaining amount of electricity stored in the battery is equal to or lower than the upper limit guard value, even when the motor generator regenerative control is required to reduce the engine speed, the battery is There is no fear of overcharging, and the engine speed can be reliably reduced by regenerative control. Further, when the remaining amount of power storage exceeds the upper limit guard value, the engine is started by a start method other than the ignition start, for example, the crank start is started by cranking the engine by the slip control of the engine connecting / disconnecting device as in the past. Therefore, the engine can be appropriately started by suppressing fluctuations in driving force by powering control of the motor generator.

  The second invention is a case where the vehicle is running and the target rotational speed is a synchronous rotational speed determined according to the vehicle speed. If the engine rotational speed exceeds the synchronous rotational speed when the engine is started, the engine is disconnected. Since the engine speed is reduced by slip engagement of the contact device and the torque of the motor generator is controlled to absorb fluctuations in the driving force, the time required for shifting to engine running can be reduced while suppressing deterioration in drivability when the engine is connected. Can be shortened.

It is the schematic block diagram which showed the principal part of the control system | strain in addition to the main point figure of the hybrid vehicle to which this invention is applied suitably. It is sectional drawing explaining the engine of the hybrid vehicle of FIG. It is a figure explaining two types of driving modes which can be performed with the hybrid vehicle of FIG. 2 is a flowchart for explaining a main part of charge control for charging a battery to an allowable maximum value SOCmax by the charge control means of FIG. 1. 2 is a flowchart for explaining an operation when the engine is started by the engine start control means of FIG. 1 and connected to a drive system. FIG. 6 is an example of a time chart for explaining changes in operating states of respective parts when an increase in engine rotation speed NE (undershoot) occurs when the engine is started in accordance with the flowchart of FIG. 5. FIG. 6 is an example of a time chart for explaining changes in the operating state of each part when an overshoot occurs when the engine rotation speed NE exceeds a target rotation speed NEtrg when the engine is started in accordance with the flowchart of FIG. 5. It is a figure explaining the other Example of this invention, and is a figure which shows the principal part of the flowchart in case ignition start is accept | permitted on fixed conditions, even if the electrical storage residual amount SOC exceeds upper limit guard value SOCuppg. It is a figure explaining the other Example of this invention, and is a flowchart explaining the case where the electrical storage residual amount SOC of a battery is restrict | limited to the upper limit guard value SOCupg on fixed conditions.

  The present invention is preferably applied to a hybrid vehicle in which an engine is connected to or disconnected from a motor generator provided in a drive system by an engine connecting / disconnecting device. However, the engine does not necessarily have to be directly connected to the motor generator. The position of the generator is determined as appropriate. In addition to this motor generator, a traveling electric motor or the like may be provided. As the engine, a 4-cycle gasoline engine is preferably used, and an engine having various cylinder numbers including a multi-cylinder engine having four or more cylinders can be used. It is also possible to use another reciprocating internal combustion engine that can start ignition by injecting fuel into a cylinder in an expansion stroke, such as a two-cycle gasoline engine. The engine connecting / disconnecting device may be any device that can connect and disconnect power transmission between the engine and the drive system. For example, a single-plate type, multi-plate type hydraulic friction engagement device is preferably used.

  The overshoot suppressing means for reducing the engine rotation speed when the engine rotation speed overshoots reduces the engine rotation speed by slip engagement of the engine connecting / disconnecting device when the vehicle is running as in the second aspect of the invention. At the same time, it is configured to absorb fluctuations in driving force through torque control of the motor generator, but when the vehicle stops at neutral, etc., it connects (engages) the engine connecting / disconnecting device and engine regenerative control controls the engine speed. Various modes are possible, such as reducing the value.

  Whether or not the motor generator needs to be regeneratively controlled when the engine rotational speed is reduced when the engine rotational speed is overshot at the start of the engine depends on the degree of overshoot and the operating state of the motor generator. However, since the maximum amount of overshoot at the start of ignition is substantially determined by the type of engine or the like, the overshoot compensation torque (maximum compensation torque) necessary to absorb the driving force fluctuation can be obtained in advance. When the vehicle is running in which the motor generator is power-running with a torque equal to or greater than this overshoot compensation torque, there is no need to perform regenerative control in the event of overshoot, so whether the remaining battery charge exceeds the upper limit guard value. It is possible to allow ignition start regardless of whether or not. The ignition start limiting means basically prohibits ignition start when the remaining battery charge exceeds the upper guard value and starts the engine with other starting methods, but allows ignition start under certain conditions. This includes cases where

  The ignition start is limited when the remaining battery charge exceeds the upper guard value, but the battery charge control exceeds the upper guard value at least when the engine in the EV drive mode is stopped. By prohibiting charging, the limit of ignition start due to the remaining amount of power stored in the battery is reduced, the frequency of ignition start is increased, and fuel efficiency can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram including a skeleton diagram of a drive system of a hybrid vehicle 10 to which the present invention is preferably applied. The hybrid vehicle 10 includes a direct injection engine 12 that directly injects fuel into a cylinder, and a motor generator MG that functions as an electric motor and a generator as driving power sources for traveling. The outputs of the engine 12 and the motor generator MG are transmitted from the torque converter 14 which is a fluid transmission device to the automatic transmission 20 via the turbine shaft 16 and the C1 clutch 18, and further to the output shaft 22 and the differential gear. It is transmitted to the left and right drive wheels 26 via the device 24. The torque converter 14 includes a friction engagement lockup clutch (LU clutch) 30 that directly connects the pump impeller and the turbine impeller.

  In the present embodiment, the engine 12 is an eight-cylinder four-cycle gasoline engine. As specifically shown in FIG. 2, gasoline (high-pressure fine particles) is injected into a cylinder (cylinder) 100 by a fuel injection device 46. Is directly injected. In the engine 12, air flows into the cylinder 100 from the intake passage 102 via the intake valve 104 and exhaust gas is discharged from the exhaust passage 106 via the exhaust valve 108. As a result, the air-fuel mixture in the cylinder 100 explodes and burns, and the piston 110 is pushed downward. The intake passage 102 is connected to an electronic throttle valve 45, which is an intake air amount adjusting device, via a surge tank 103. From the intake passage 102 to the cylinder according to the opening of the electronic throttle valve 45 (throttle valve opening). The amount of intake air flowing into 100, that is, the engine output is controlled. The piston 110 is fitted in the cylinder 100 so as to be slidable in the axial direction, and is connected to a crankpin 116 of the crankshaft 114 via a connecting rod 112 so as to be relatively rotatable. Along with the reciprocation, the crankshaft 114 is rotationally driven as indicated by an arrow R. The crankshaft 114 is rotatably supported by a bearing in the journal portion 118, and integrally includes a crank arm 120 that connects the journal portion 118 and the crankpin 116.

  In such an engine 12, the crankshaft 114 is rotated twice (720 °), and the intake stroke, the compression stroke, the expansion (explosion) stroke, and the exhaust stroke are performed, and the crankshaft 114 is repeated by repeating these strokes. Is rotated continuously. The pistons 110 of the eight cylinders 100 are configured such that the crank angle Φ is shifted by 90 °, and the eight cylinders 100 are sequentially exploded and burned each time the crankshaft 114 rotates 90 °. A rotational torque is generated. Further, the expansion stroke in which the crankshaft 114 rotates by a predetermined angle from the compression TDC in which the piston 110 of any cylinder 100 reaches the TDC (top dead center) after the compression stroke, and both the intake valve 104 and the exhaust valve 108 are closed. When the fuel is stopped within the predetermined angle range θ, gasoline is injected into the cylinder 100 by the fuel injection device 46 and ignited by the ignition device 47, whereby the air-fuel mixture in the cylinder 100 is explosively burned and started. Ignition start is possible. The angle range θ is suitably within a range of, for example, 30 ° to 60 ° from the compression TDC. However, in the case of an 8-cylinder engine, ignition can be started even when the compression TDC is about 80 ° to 100 °. The angle range θ is appropriately determined according to the number of cylinders of the engine 12 and the like.

  Returning to FIG. 1, a K0 clutch 34 is provided between the engine 12 and the motor generator MG via a damper 38 to directly connect them. The K0 clutch 34 is a single-plate or multi-plate hydraulic friction engagement clutch that is frictionally engaged by a hydraulic cylinder, and is engaged and released by the hydraulic control device 28. The K0 clutch 34 is a hydraulic friction engagement device, and functions as an engine connecting / disconnecting device that connects or disconnects the engine 12 to / from the power transmission path from the drive system, that is, the motor generator MG to the drive wheels 26. The motor generator MG is connected to the battery 44 via the inverter 42, functions as an electric motor by performing power running control based on power supply from the battery 44, and is regeneratively controlled so as to charge the battery 44. It functions as a generator. Further, the automatic transmission 20 is a stepped automatic transmission such as a planetary gear type in which a plurality of gear stages having different gear ratios are established depending on the disengagement state of a plurality of hydraulic friction engagement devices (clutch and brake). The shift control is performed by an electromagnetic hydraulic control valve, a switching valve or the like provided in the hydraulic control device 28. The C1 clutch 18 functions as an input clutch of the automatic transmission 20 and is similarly controlled to be disengaged by the hydraulic control device 28.

  Such a hybrid vehicle 10 is controlled by the electronic control unit 70. The electronic control unit 70 includes a so-called microcomputer having a CPU, a ROM, a RAM, an input / output interface, and the like, and performs signal processing according to a program stored in advance in the ROM while using a temporary storage function of the RAM. Do. A signal representing the accelerator pedal operation amount (accelerator operation amount) Acc is supplied from the accelerator operation amount sensor 48 to the electronic control unit 70. Further, the engine speed sensor 50, the MG speed sensor 52, the turbine speed sensor 54, the vehicle speed sensor 56, the crank angle sensor 58, and the SOC sensor 60 are respectively connected to the engine speed 12 (engine speed) NE, the motor generator. MG rotational speed (MG rotational speed) NMG, turbine shaft 16 rotational speed (turbine rotational speed) NT, output shaft 22 rotational speed (output shaft rotational speed corresponds to vehicle speed V) NOUT, TDC for each of eight cylinders 100 A signal relating to the rotation angle (crank angle) Φ from (top dead center) and the remaining charge SOC of the battery 44 is supplied. In addition, various types of information necessary for various types of control are supplied. The SOC sensor 60 is configured to obtain the remaining power storage SOC from the battery voltage, for example, but it is also possible to obtain the remaining power SOC by sequentially integrating the charge amount and discharge amount of the battery 44. The accelerator operation amount Acc corresponds to the driver's requested output amount.

  The electronic control unit 70 functionally includes a hybrid control unit 72, a shift control unit 74, and a charge control unit 76, and also includes an engine start control unit 80, an assist unit 90, an overload control unit for starting the engine 12 and controlling connection to the drive system. A chute suppressing means 92 and an engine connecting means 94 are provided. The hybrid control means 72 controls the operation of the engine 12 and the motor generator MG, for example, an engine travel mode in which the engine 12 travels using the engine 12 as a drive power source, or travels using only the motor generator MG as the drive power source. The vehicle travels by switching a plurality of predetermined travel modes such as the EV travel mode in accordance with a predetermined mode switching condition based on the operation state such as the accelerator operation amount Acc and the vehicle speed V. In the engine running mode, as shown in FIG. 3, the K0 clutch 34 is engaged (completely engaged) and the engine 12 is connected to the drive system, and the motor generator MG is basically free (no load). However, the power is controlled as needed to assist the driving force when acceleration is requested. The lock-up clutch 30 is engaged and released according to a predetermined switching map with the vehicle speed V or the like as a parameter. The EV travel mode is a mode in which the K0 clutch 34 is released and the engine 12 is disconnected from the drive system, and the lockup clutch 30 is engaged (completely engaged). In this EV travel mode, the engine 12 stops rotating with the stop of fuel injection or the like, and the deterioration of fuel consumption due to the accompanying rotation is prevented. In both the engine travel mode and the EV travel mode, charging control is performed in which the motor generator MG is regeneratively controlled to charge the battery 44 when the vehicle is decelerated or braked.

  The shift control means 74 controls an electromagnetic hydraulic control valve, a switching valve and the like provided in the hydraulic control device 28 to switch the engagement / disengagement state of the plurality of hydraulic friction engagement devices. These gear stages are switched according to a predetermined shift map with the operating state such as the accelerator operation amount Acc and the vehicle speed V as parameters.

  The charge control means 76 performs control when the battery 12 is charged by regenerative control of the motor generator MG when the vehicle is decelerated or braked, for example, and the remaining power SOC is determined in advance based on the charge / discharge efficiency and the like. Control is performed so as to be held within the range of the defined allowable minimum value SOCmin and allowable maximum value SOCmax. Regarding the allowable maximum value SOCmax, for example, as shown in FIG. 4, it is determined in step R1 whether or not the remaining power SOC is equal to or lower than the allowable maximum value SOCmax. If SOC ≦ SOCmax, the battery 44 is charged in step R2, while If the remaining power storage SOC exceeds the allowable maximum value SOCmax, step R3 is executed to stop charging. Although the illustration of the allowable minimum value SOCmin is omitted, for example, when the remaining power SOC is lower than the allowable minimum value SOCmin, the assist by the motor generator MG is prohibited during traveling in the engine traveling mode, or the motor generator A command for executing a charging mode in which the MG is regeneratively controlled to charge the battery 44 is output.

  The charge control means 76 is also set with a lower limit guard value SOCdng that can start the engine 12 by cranking it with the motor generator MG or assist the engine rotation at the start of ignition. When the engine is stopped in the mode or the like, if the remaining power storage SOC falls below the lower limit guard value SOCdng, the EV running mode is prohibited to prevent further decrease in the remaining power storage SOC. That is, the remaining power SOC is managed so that the engine 12 can be started at any time while the engine 12 is stopped.

  The engine start control means 80 is for starting the engine 12 which is disconnected from the drive system and stopped by releasing the K0 clutch 34, and is functionally ignited start means 82, cranking start means 84, and ignition start limit. Means 86 is provided. FIG. 5 is a flowchart for specifically explaining engine start connection control executed by the engine start control means 80, the assist means 90, the overshoot suppression means 92, and the engine connection means 94. Steps S1 to S5 in this flowchart correspond to the engine start control means 80, in which step S3 corresponds to the ignition start limiting means 86, step S4 corresponds to the ignition start means 82, and step S5 corresponds to the cranking start means. 84. Steps S6 to S8 correspond to the overshoot suppression means 92, steps S9 to S11 correspond to the assist means 90, and steps S13 and S14 correspond to the engine connection means 94.

  The flowchart of FIG. 5 is executed while the vehicle is traveling in the EV traveling mode in which the K0 clutch 34 is released and the engine 12 is disconnected from the drive system and stopped at the engine rotational speed NE = 0 (including when the vehicle is stopped). In step S1, it is determined whether an engine start request has been made. The engine start request is, for example, when the remaining charge SOC of the battery 44 falls below the lower limit guard value SOCdng, or when the vehicle speed V or the driver's output request amount, that is, the accelerator operation amount Acc, satisfies a predetermined mode switching condition. When the EV travel mode is switched to the engine travel mode, it is supplied from the hybrid control means 72. If there is no engine start request, the process ends as it is, but if there is an engine start request, steps S2 and after are executed. FIGS. 6 and 7 are examples of time charts showing changes in the engine rotational speed NE, the MG torque TMG, the remaining power storage SOC, and the K0 torque TK0 when switching from the motor travel mode to the engine travel mode. This is the time when the engine start request is supplied and the determination in step S1 is YES. MG torque TMG is the torque of motor generator MG, and K0 torque TK0 is the engagement torque of K0 clutch 34, that is, the transmission torque.

  In step S2, it is determined whether ignition start is possible. If ignition start is possible, step S3 is executed, and if ignition start is impossible, step S5 is executed. Whether or not the ignition start is possible is determined in advance, for example, the crank angle Φ of any cylinder 100 of the engine 12 is within a predetermined angle range θ, and the engine coolant temperature is equal to or higher than a predetermined temperature. Judgment is made based on whether the basic conditions for starting ignition are satisfied. If ignition cannot be started, that is, if the determination in step S2 is NO (No), the engine 12 is started in the cranking start in step S5. During cranking, the K0 clutch 34 is slip-engaged while the vehicle is running, and the engine 12 is rotationally driven (cranking), and the engine 12 is started by performing start control such as fuel injection and ignition. The driving force fluctuation caused by the cranking is absorbed by the torque control of the motor generator MG. In this case, since the driving force of the vehicle is used to increase the engine rotational speed NE, it is necessary to increase the power running torque of the motor generator MG accordingly, and overcharging of the battery 44 does not become a problem. Further, when the engine is started in a neutral (power cut-off state) stop, the K0 clutch 34 is completely engaged, and the engine rotational speed NE is increased by the power running control of the motor generator MG. Then, when the engine 12 can be rotated on its own by the cranking start, step S6 and subsequent steps are executed.

  If the ignition start is possible and the determination in step S2 is YES, step S3 is subsequently executed to determine whether or not the remaining power SOC of the battery 44 is equal to or less than a predetermined upper limit guard value SOCupg. This is because when the engine 12 is started at the ignition start, the engine speed NE is generally higher than the cranking start, and there is a possibility that an overshoot that greatly exceeds the target speed NEtrg occurs (see FIG. 7). If the K0 clutch 34 is directly engaged and pulled down to the target rotational speed NEtrg, a large driving force fluctuation occurs due to the inertia of the engine 12 or the time required for shifting to the engine running mode becomes long. In the present embodiment, the engine speed NE is reduced by torque control of the motor generator MG. In this case, however, it is necessary to reduce the power running torque of the motor generator MG by the amount of inertia torque, and the MG torque TMG is low. Regenerative control is required. In order to perform this regenerative control, the battery 44 needs a surplus charge capacity, and the upper limit guard value SOCupg is a charge necessary to absorb the fluctuation of the driving force when the overshoot occurs by the regenerative control of the motor generator MG. It is determined that the remaining power remains. Specifically, when the engine TMG of the motor generator MG is 0 when the engine is stopped or coasting, an overshoot occurs, and when the engine speed NE is reduced by regenerative control, the electricity generated by the regenerative control is reduced. A value smaller than the permissible maximum value SOCmax is determined so as to leave sufficient charge capacity for the battery 44 to be charged. When the upper limit guard value SOCupg is set in this way and ignition start is performed when the upper limit guard value SOCupg or less, the motor generator MG is driven by the torque control of the motor generator MG regardless of whether or not the power running control is in progress. The engine speed NE can be reliably reduced while preventing force fluctuations. The target rotational speed NEtrg is, for example, the idle rotational speed NEidl when the vehicle is stopped, and the synchronous rotational speed NEsyn that is equal to the rotational speed on the drive system side of the K0 clutch 34 when traveling, specifically the vehicle speed V It is determined according to the gear ratio of the automatic transmission 20 and is the same as the rotational speed NMG of the motor generator MG in this embodiment.

  If the remaining power SOC is larger than the upper limit guard value SOCuppg, the engine 12 is started by cranking start in step S5. On the other hand, if it is equal to or lower than the upper limit guard value SOCuppg, the engine 12 is started by ignition start in step S4. Start. In this ignition start, fuel is directly injected into the cylinder 100 in the expansion stroke and ignited to start the engine 12 without external rotation assistance. Immediately after the engine 12 starts to rotate, step S6 and subsequent steps are started. Execute. FIGS. 6 and 7 both show the case where the engine 12 is started by the ignition start in accordance with the engine start request. At the beginning of the engine start, the torque TK0 of the K0 clutch 34 is 0 and is maintained in the released state. Remains disconnected from the drive train.

  In step S6, it is determined whether or not an overshoot has occurred. Specifically, it is determined whether or not the engine speed NE is higher than a predetermined determination value α than the target rotation speed NEtrg. If the engine speed NE is higher than the determination value α, it is determined that an overshoot has occurred. To do. At the beginning of the control, the engine rotational speed NE is lower than the target rotational speed NEtrg, the determination in step S6 is NO, and step S9 is executed. In step S9, it is determined whether or not the engine rotational speed NE is equal to or higher than a predetermined lower limit guard value NEg, that is, whether or not the rising of the engine rotational speed NE satisfies a predetermined rising criterion. The lower limit guard value NEg is determined by using the elapsed time from the start of the start control (time t1) as a parameter, for example, as shown by a one-dot chain line in the column of the engine speed NE in FIG. In step S12, the K0 clutch 34 is released, or the released state is maintained, thereby maintaining the increased state of the engine speed NE only by the self-rotation of the engine 12, and then step S13 is executed. Instead of the lower limit guard value NEg, it is also possible to determine whether or not the rising standard is satisfied based on whether or not the rising gradient ΔNE, which is the changing speed of the engine speed NE, is greater than or equal to a predetermined determination value β.

  On the other hand, if NE <NEg, i.e., undershoot where the engine speed NE rises slowly and the determination in step S9 is NO, the assist control of steps S10 and S11 is executed to assist the increase in the engine speed NE. Thereafter, step S13 is executed. In step S10, the K0 clutch 34 is controlled to be engaged, and in step S11, torque control of the motor generator MG is performed. That is, at the start of ignition, the rise of the engine rotational speed NE may be delayed depending on the crank angle Φ and the like. Therefore, when the vehicle is traveling when the vehicle is traveling, the engine is slip-engaged when the engine is traveling below the lower limit guard value NEg. While assisting the increase of the rotational speed NE, the driving force fluctuation caused by the assist is absorbed by the torque control (power running control) of the motor generator MG. The engagement torque TK0 of the K0 clutch 34 and the compensation torque of the motor generator MG are controlled continuously or stepwise according to, for example, the deviation between the lower limit guard value NEg and the engine speed NE, but are set to predetermined values in advance. May be. When starting the engine while the vehicle is stopped in neutral, the K0 clutch 34 is completely engaged in step S10, and in step S11, assist is provided by powering control of the motor generator MG. By repeatedly executing these steps S10 and S11, the engine speed NE is set to be equal to or higher than the lower limit guard value NEg while suppressing fluctuations in driving force, and the required time for shifting to the engine running mode is within a predetermined time. Can be suppressed. The lower limit guard value NEg and the determination value β may be set in advance regardless of the ignition start or the cranking start, but different values may be set for the ignition start and the cranking start.

  The solid line in FIG. 6 is the case where the engine start control is performed according to the flowchart in FIG. 5 while the vehicle is stopped at the neutral position, and the two-dot chain line in the column of MG torque TMG and K0 torque TK0 is the case where the vehicle is running. Time t2 to t3 is the time when the assist control is performed in steps S10 and S11, and has reached the vicinity of the target rotational speed NEtrg at time t3. The engine rotation speed NE and the remaining power storage SOC when the vehicle is running are substantially the same as when the vehicle is stopped at the neutral position indicated by the solid line. Although the remaining power storage SOC is reduced by this assist control, in the present embodiment, the engine is started at the lower limit guard value SOCdng or more, so the remaining power SOC does not fall below the allowable lower limit SOCmin, and the motor generator MG The engine speed NE can be appropriately increased by the assist control. On the other hand, for example, as shown by a broken line, if the remaining power SOC is lower than the lower limit guard value SOCdng, the assist control by the motor generator MG cannot be performed properly, and therefore the engine speed NE increases as shown by the broken line. The time t4 for reaching near the target rotational speed NEtrg is delayed while the gradient ΔNE remains low. Therefore, when an undershoot of the engine speed NE is expected, it is necessary to perform ignition start in a range where the remaining power storage SOC is equal to or greater than the lower limit guard value SOCdng. Note that the assist control in steps S10 and S11 is continued until the predetermined assist release condition is satisfied even when the engine rotational speed NE is equal to or higher than the lower limit guard value NEg. In FIG. 6, until the target rotational speed NEtrg is reached. Assist control is being executed.

  If the determination in step S6 is YES, that is, if the engine speed NE has overshooted, overshoot suppression control in steps S7 and S8 is executed, and then step S13 is executed. In step S7, the K0 clutch 34 is controlled to be engaged, and in step S8, torque control of the motor generator MG is performed. That is, if the vehicle is running, the engine rotational speed NE is reduced by slip-engaging the K0 clutch 34 in step S7, and the driving force fluctuation caused by the inertia of the engine 12 is reduced by the motor generator MG in step S8. Absorb with torque control. In this case, contrary to the assist control, it is necessary to suppress an increase in driving force. When the motor generator MG is subjected to power running control, the power running torque is reduced, and regenerative control is performed as necessary. Further, when the torque TMG = 0 of the motor generator MG during inertial running, the increase in driving force is absorbed by regenerative control. In this case, the engagement torque TK0 of the K0 clutch 34 and the compensation torque of the motor generator MG are controlled continuously or stepwise in accordance with, for example, the deviation between the engine speed NE and the target speed NEtrg. May be defined. When the engine is stopped in the neutral state, the K0 clutch 34 is completely engaged in step S7, and in step S8, the engine speed NE is reduced by regenerative control of the motor generator MG. By repeatedly executing these steps S7 and S8, overshoot of the engine rotational speed NE is suppressed while suppressing fluctuations in driving force, and the time required for shifting to the engine running mode is suppressed within a predetermined time. Can do.

  The solid line in FIG. 7 is the case where the engine start control is performed according to the flowchart in FIG. 5 while the vehicle is stopped at the neutral position, and the two-dot chain line in the column of MG torque TMG and K0 torque TK0 is the case where the vehicle is running. Also, the times t2 to t3 are the times when the overshoot suppression control is performed in the above steps S7 and S8, and converge at around the target rotational speed NEtrg at the time t3. The engine rotation speed NE and the remaining power storage SOC when the vehicle is running are substantially the same as when the vehicle is stopped at the neutral position indicated by the solid line. In this case, since the engine speed NE is reduced by the regeneration control of the motor generator MG, the remaining power storage SOC increases with the regeneration control. In this embodiment, the ignition start is performed with the upper limit guard value SOCupg or less. Therefore, the remaining power SOC does not exceed the allowable upper limit SOCmax, and the engine speed NE can be appropriately reduced by the regeneration control of the motor generator MG. On the other hand, for example, as indicated by a broken line, when the remaining power SOC is higher than the upper limit guard value SOCupg, the regenerative control of the motor generator MG cannot be performed appropriately, and the driving force is obtained only by the engagement control of the K0 clutch 34. If the engine rotational speed NE is to be lowered while suppressing the fluctuation, the engine overshoots greatly as shown by the broken line, and the time t4 that converges near the target rotational speed NEtrg is delayed. Therefore, when an overshoot of the engine speed NE is expected, it is necessary to perform ignition start in a range where the remaining power storage SOC is equal to or lower than the upper limit guard value SOCuppg.

  In step S13, a synchronization determination is made as to whether or not a state in which the state in which the engine rotational speed NE substantially matches the target rotational speed NEtrg has continued for a certain period of time has been reached. Step S6 and subsequent steps are repeated until the synchronization determination is made, and when the synchronization determination is made, the K0 clutch 34 is completely engaged in step S14. Thereby, a series of engine start connection control is completed, and the EV travel mode is switched to the engine travel mode. The time t3 in FIGS. 6 and 7 is the time when the step S14 is executed and the K0 clutch 34 is completely engaged and the mode is switched to the engine travel mode. 6 and 7, when the vehicle is stopped at the neutral position indicated by the solid line, the K0 clutch 34 is completely engaged at time t2, but the end time of the engine start connection control is time t3. In addition, when the vehicle is running in which the motor generator MG is powering controlled as indicated by a two-dot chain line in FIGS. 6 and 7, the torque TMG of the motor generator MG after the time t3 when the engine start connection control is finished. The torque is switched by gradually increasing the engine torque while gradually decreasing.

  Thus, in the engine start connection control of the hybrid vehicle 10 of the present embodiment, when the engine speed NE exceeds the target speed NEtrg at the time of engine start, that is, when the determination in step S6 becomes YES. Performs overshoot suppression control in steps S7 and S8, engages the K0 clutch 34, and lowers the engine speed NE by torque control of the motor generator MG. Therefore, fluctuations in driving force occur due to overshoot. Or a long transition time is prevented. For example, when the vehicle is running, a synchronous rotational speed NEsyn determined according to the vehicle speed V is set as the target rotational speed NEtrg, and the engine rotational speed NE exceeds the synchronous rotational speed NEsyn when the engine 12 is started. In this case, the engine rotational speed NE is reduced by slip engagement of the K0 clutch 34 and the driving force fluctuation is absorbed by the torque control of the motor generator MG. Therefore, the engine is prevented from deteriorating in drivability when the engine is connected. The time required for shifting to the driving mode can be shortened.

  On the other hand, when the remaining power SOC of the battery 44 is equal to or lower than the upper limit guard value SOCupg, the ignition start in step S4 is executed. Therefore, the regeneration control of the motor generator MG is performed in order to reduce the engine speed NE when the overshoot occurs. However, the battery 44 is not overcharged by the regenerative control, and the engine speed NE can be reliably reduced by the regenerative control. In other words, when the remaining power storage SOC exceeds the upper limit guard value SOCupg, execution of the engine start by ignition start is prohibited, so that ignition is required when regeneration control of the motor generator MG is necessary during overshoot. The start is performed, and the regenerative control cannot be performed, so that it is possible to prevent the fluctuation of the driving force from occurring and the required time for the transition from being prolonged.

  In addition, the cranking start in step S5, which starts the engine 12 by cranking the engine by the engagement control of the K0 clutch 34 and the torque control of the motor generator MG, is not limited by the upper limit guard value SOCupg, and the remaining charge SOC of the battery 44 When the engine speed exceeds the upper limit guard value SOCupg, the engine 12 is started by the cranking start. Therefore, the engine 12 is appropriately started while suppressing the driving force fluctuation by the power running control of the motor generator MG, and the engine is quickly Transition to driving mode. In the cranking start, the battery 44 is discharged by the cranking, and the possibility of overshooting is low as compared with the ignition start. Therefore, there is no possibility that the remaining charge SOC of the battery 44 reaches the allowable maximum value SOCmax.

  Next, another embodiment of the present invention will be described. In the following embodiments, parts that are substantially the same as those in the above embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the above embodiment, when the remaining power SOC of the battery 44 exceeds the upper limit guard value SOCupg, the engine start by the ignition start in step S4 is uniformly prohibited, and the cranking start in step S5 is executed. However, as shown in the flowchart of FIG. 8, it is also possible to allow ignition start under certain conditions. That is, since the maximum amount of overshoot at the start of ignition is substantially determined by the type of the engine 12 and the like, it is possible to obtain in advance the overshoot compensation torque (maximum compensation torque) TMGos necessary for reducing the engine speed NE. is there. When the motor generator MG is power-running controlled with a torque TMG that is equal to or greater than the overshoot compensation torque TMGos, it is possible to absorb fluctuations in the driving force simply by reducing the torque TMG of the motor generator MG. No control is necessary. In this case, since it is not necessary to prohibit the ignition start even if the remaining power SOC of the battery 44 exceeds the upper guard value SOCuppg, step S3-1 is provided as shown in FIG. 8, and the MG torque TMG is compensated for overshoot. It is determined whether or not the torque TMGos or more. If TMG ≧ TMGos, the ignition start in step S4 is executed. If TMG <TMGos, the engine 12 is started in the cranking start in step S5. The overshoot compensation torque TMGos may be set to a predetermined value in advance, but may be variably set using the vehicle speed V or the like as a parameter. Note that step S3-1 may be executed prior to step S3, and step S3 may be executed when TMG <TMGos. In this embodiment, steps S3 and S3-1 correspond to the ignition start limiting means 86.

  In this embodiment, when the motor generator MG is subjected to power running control with a torque equal to or higher than a predetermined overshoot compensation torque TMGos so that the driving force fluctuation can be absorbed only by controlling the power running torque of the motor generator MG. Thus, the determination in step S3-1 becomes YES and the ignition start in step S4 is executed, and the engine 12 is started in the ignition start even if the remaining charge SOC of the battery 44 exceeds the upper limit guard value SOCuppg. The That is, when the torque TMG of the motor generator MG is equal to or greater than the overshoot compensation torque TMGos, the driving force fluctuations when the engine speed NE is decreased by slip engagement of the K0 clutch 34 when the engine speed NE overshoots. Can be absorbed simply by reducing the power running torque TMG of the motor generator MG, so there is no need to perform regenerative control, and ignition can be started regardless of whether or not the remaining charge SOC of the battery 44 exceeds the upper guard value SOCuppg. The engine 12 is started. When the engine 12 is started to ignite in this manner, the consumption of the battery 44 is reduced compared to the case where the engine 12 is started by cranking, and fuel consumption can be improved.

  FIG. 9 is a flowchart for explaining still another embodiment of the present invention, and is a flowchart executed by the charge control means 76. In step Q1 in FIG. 9, it is determined whether or not the engine 12 is stopped. If the rotation is not stopped, step R1 and subsequent steps in FIG. 4 are executed to charge the battery 44 to the allowable maximum value SOCmax. On the other hand, when the engine 12 is stopped in rotation, that is, when there is a possibility of an engine start request immediately after that, step Q2 or less is executed, and the remaining power SOC of the battery 44 is limited to the upper limit guard value SOCupg or less. Charge control is performed as follows. That is, it is determined in step Q2 whether or not the remaining power SOC is equal to or lower than the upper limit guard value SOCuppg. If SOC ≦ SOCupg, the battery 44 is charged in step Q3, while the remaining power SOC exceeds the upper guard value SOCuppg. If so, step Q4 is executed to stop charging.

  In this case, there is a high possibility that the determination in step S3 of FIG. 5 will be YES, so the ignition start restriction due to the remaining amount of charge SOC of the battery 44 is reduced, the frequency of ignition start is increased, and the fuel consumption is improved. To do. Note that when the engine is started, the determination at step Q1 in FIG. 9 is NO, and charging control is performed according to step R1 and subsequent steps in FIG. 4. Therefore, when the engine is started, the engine speed NE is overshooted and the motor generator MG is regeneratively controlled. In this case, the battery 44 can be charged exceeding the upper guard value SOCuppg, and fluctuations in driving force can be appropriately suppressed by the regenerative control.

  As mentioned above, although the Example of this invention was described in detail based on drawing, these are one embodiment to the last, and this invention is implemented in the aspect which added the various change and improvement based on the knowledge of those skilled in the art. be able to.

  10: Hybrid vehicle 12: Engine 34: K0 clutch (engine connection / disconnection device) 44: Battery 70: Electronic control device 80: Engine start control means 82: Ignition start restriction means 86: Ignition start restriction means 92: Overshoot suppression means 94: Engine connection means MG: Motor generator NE: Engine rotation speed NEtrg: Target rotation speed SOC: Remaining power storage SOCupg: Upper limit guard value

Claims (2)

An engine capable of starting ignition by directly injecting and igniting fuel into a cylinder in an expansion stroke, an engine connecting / disconnecting device for disconnecting the engine from a drive system, an electric motor and a generator A hybrid vehicle having a motor generator that can be selectively used and a battery that exchanges power with the motor generator,
Ignition starting means for igniting and starting the engine which is cut off from the drive system by the engine connecting / disconnecting device;
Engine connection means for engaging the engine connecting / disconnecting device and connecting the engine to a drive system when the engine rotation speed is increased at the ignition start and reaches a target rotation speed;
In an engine start connection control device having
When an overshoot occurs in which the engine rotation speed exceeds the target rotation speed when the engine is started, the engine connecting / disconnecting device is engaged, and the engine rotation speed is controlled by torque control of the motor generator including regenerative control. Overshoot suppression means for reducing,
If the remaining amount of electricity stored in the battery exceeds a predetermined upper limit guard value, ignition start limiting means for starting the engine by a start method other than the ignition start,
An engine start connection control device for a hybrid vehicle, comprising: The target rotational speed is a synchronous rotational speed determined according to the vehicle speed,
The overshoot suppression means reduces the engine rotation speed by slip engagement of the engine connecting / disconnecting device when the engine rotation speed exceeds the synchronous rotation speed, and is generated along with the decrease in the engine rotation speed. 2. The engine start connection control device for a hybrid vehicle according to claim 1, wherein fluctuations in driving force are absorbed by torque control of the motor generator.

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