JPWO2012117517A1 - Engine start control device for hybrid vehicle - Google Patents

Abstract

A hybrid vehicle including a mechanism (39) for driving and controlling the vehicle using outputs from the engine (2) and the plurality of motor generators (4, 5) and fixing the output shaft (3) of the engine (2). In the engine start control device (1), when the engine (2) is started, the torque acting on the output shaft (3) of the engine (2) is gradually reduced, and then the engine (2) The engine torque is gradually changed until the torque required for ranking is reached. Thereby, in order to avoid a step-like torque change when applying a torque required for engine start, a sudden fluctuation of the driving force can be suppressed and a shock at the time of engine start can be reduced. [Selection] Figure 1

Description

  The present invention relates to an engine start control device for a hybrid vehicle, and in particular, in a vehicle that combines power from a plurality of power sources by a power transmission mechanism (differential gear mechanism) and inputs / outputs to / from a drive shaft. The present invention relates to an engine start control device for a hybrid vehicle that controls a power source.

There are hybrid vehicles that drive and control a vehicle using outputs from an engine and a plurality of motor generators (electric motors) as a drive source.
In this hybrid vehicle, the series system (the engine is used only for turning the generator and all the driving is performed by the motor generator: the series system) and the parallel system (the engine and the motor generator are arranged in parallel, There is a system in which power is used for driving: a parallel system).
In addition to these series and parallel systems, there are other systems for hybrid vehicles.

JP-A-9-170533 JP 10-325345 A Japanese Patent No. 3578451 JP 2002-281607 A JP 2010-95051 A JP 2005-81931 A

The hybrid vehicle according to Patent Documents 1 and 2 has one planetary gear mechanism (differential gear mechanism having three rotating elements) as a three-axis power transmission mechanism and two motor generators (first as a motor generator). The motor generator: MG1 and the second motor generator: MG2) are used to divide the engine power into a generator and a drive shaft, and the motor generator provided on the drive shaft is driven using the power generated by the generator By doing so, the engine power is torque converted. Thereby, the operating point of the engine (engine operating point) can be set to an arbitrary point including the stop, and the fuel efficiency is improved.
In the hybrid vehicle according to Patent Documents 3 and 4, in the four-shaft type power transmission mechanism, the output shaft of the engine and the first motor are provided in each rotational element of the power transmission mechanism (differential gear mechanism) having four rotational elements. A generator (MG1), a second motor generator (MG2), and a drive shaft as an output member connected to the drive wheels are connected, and the engine power and the first motor generator (MG1) / second motor generator ( The power of MG2) is combined and output to the drive shaft.
The hybrid vehicles according to Patent Documents 5 and 6 are provided with a brake mechanism that controls the rotation speed of the output shaft of the engine by a braking force, and can fix the output shaft of the engine.

However, conventionally, in Patent Documents 1 and 2 described above, although not as much as the series system, a motor generator having a relatively large torque is necessary to obtain sufficient torque to the drive shaft, and the LOW gear. Since the amount of electric power transferred between the generator and the motor increases in the frequency range, the electrical loss increases, and there is still room for improvement.
In order to solve this problem, in the hybrid vehicle as disclosed in Patent Documents 3 and 4 above, the output shaft and the drive shaft of the engine are arranged on the inner rotating element on the alignment chart, and the alignment chart is displayed. The first motor generator (MG1) on the engine side and the second motor generator (MG2) on the drive shaft side are arranged on the outer rotating element above, so that the first of the power transmitted from the engine to the drive shaft. The ratio of the motor generator (MG1) and the second motor generator (MG2) can be reduced, so that the first motor generator (MG1) and the second motor generator (MG2) can be reduced in size and power Improves transmission efficiency.
In addition, a method has been proposed in which a fifth rotating element is further added to such a four-axis power transmission mechanism, and a brake is provided to stop the rotation of these rotating elements.
In the three-shaft power transmission mechanism described in Patent Document 1 described above, when the engine start determination is made, the first motor generator (MG1) drives the engine, and the reaction force or the like drives the drive shaft. By controlling the second motor generator (MG2) so as to cancel the generated driving force, torque fluctuation of the driving shaft at the time of engine start is suppressed.
Further, in Patent Document 2 described above, when the engine start determination is made, the first motor generator (MG1) is controlled so that the rotation speed of the first motor generator (MG1) becomes the target rotation speed. As a result, the engine is started, and torque fluctuation due to driving of the first motor generator (MG1) is corrected by the second motor generator (MG2), thereby suppressing torque fluctuation of the drive shaft at the time of engine startup. Yes.
In the case of a three-shaft power transmission mechanism, the torque of the second motor generator (MG2) does not affect the torque balance, so the torque of the first motor generator (MG1) output for starting the engine. Then, the reaction torque output to the drive shaft by the engine and the first motor generator (MG1) is calculated, and the torque of the second motor generator (MG2) is controlled so as to cancel the reaction torque. Thus, it is possible to start the engine by eliminating torque fluctuations on the drive shaft.
However, in the case of a 4-axis power transmission mechanism, the drive shaft and the second motor generator (MG2) are separate shafts, and the torque of the second motor generator (MG2) also affects the torque balance. For this reason, the above three-axis control method cannot be used.

Further, there are the following methods for controlling the four-axis power transmission mechanism.
In a hybrid vehicle that drives the drive shaft connected to the drive wheels by combining the engine output, the power of the first motor generator (MG1), and the second motor generator (MG2), the amount of power assist by electric power is added. The value of the driving force is set in advance as the maximum value of the target driving force, the target driving force is calculated using the accelerator operation amount and the vehicle speed as parameters, and the target driving power is obtained from the target driving force and the vehicle speed. Further, the target charge / discharge power is obtained based on the state of charge (SOC) of the battery, the value added to the target drive power is compared with the maximum output that can be output by the engine, and the smaller value is obtained as the target engine power. The target engine operating point is obtained from the target engine power, and the input / output power from the battery is calculated from the difference between the target drive power and the target engine power. The target power, which is the target value, is obtained, and the control command values (first motor generator (MG1) and second motor generator (MG2)) are determined from the torque balance formula including the target engine torque and the power balance formula including the target power. Motor torque command value) is calculated.
However, in such a method, although the torque in the four-shaft type can be controlled appropriately, there is no room for improvement because it does not mention control related to engine start.

Further, the following control is considered as the engine start control of the hybrid vehicle.
In a hybrid vehicle that combines the output of the engine, the power of the first motor generator (MG1), and the power of the second motor generator (MG2) to drive the drive shaft connected to the drive wheels, the accelerator operation amount and the vehicle speed are parameters. The target drive power is obtained, the target drive power is obtained from the target drive power and the vehicle speed, the target charge / discharge power is obtained based on the state of charge (SOC) of the battery, and the value added to the target drive power is provisional target engine When calculating the power and starting the engine, the target engine rotation speed at the time of engine start is determined from the provisional target engine power and the vehicle speed, and the torque required for engine cranking set in advance is set as the target engine torque. The target engine power is calculated from the engine speed and target engine torque, and the target driving force and vehicle speed are calculated. The target power, which is the target value of the input / output power from the battery, is obtained from the difference between the target drive power calculated from the target engine power and the target engine power. The base torque command values of the motor generator (MG1) and the second motor generator (MG2) are calculated, and the first calculated based on the deviation between the target engine speed and the actual engine speed The correction torques of the motor generator (MG1) and the second motor generator (MG2) are added to the base torque correction value, the target engine rotation acceleration is calculated from the target engine rotation speed, and the target engine rotation acceleration is calculated. Engine, first motor generator (MG1), second motor generator (M 2) The inertia correction torques of the first motor generator (MG1) and the second motor generator (MG2) for correcting the respective inertia torques of 2) are further added to the base torque command value to which the feedback correction torque is added. The final command torque values of the first motor generator (MG1) and the second motor generator (MG2) are used.
However, even with such control, the engine can be started while appropriately controlling the torque in the four-shaft type, but there is still room for improvement.

  Furthermore, in the hybrid vehicle described in Patent Document 4, a one-way clutch is provided on the output shaft of the engine so that the engine does not reversely rotate, and the second motor generator (MG2) is used during EV (electric vehicle) travel. The one-way clutch receives the reaction torque of the car and runs. In such a vehicle, the reaction torque of the second motor generator (MG2) is received by the one-way clutch during EV traveling, whereas the second motor generator (MG2) is driven by the one-way clutch during HEV (hybrid) traveling. ), The torque of the first motor generator (MG1) and the second motor generator (MG2) changes discontinuously at the moment when the engine is started. There is a possibility that the driving force may change discontinuously due to a difference in motor torque response and the like, which causes an inconvenience of giving an unpleasant shock to the driver.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an engine start control device for a hybrid vehicle that suppresses sudden fluctuations in driving force and reduces the occurrence of shock at engine start.

  The present invention controls the drive of a vehicle using outputs from an engine and a plurality of motor generators, and starts the engine in a hybrid vehicle engine start control device having a mechanism for fixing the output shaft of the engine. In this case, the torque acting on the output shaft of the engine is gradually decreased, and then the engine torque is gradually changed until the torque necessary for cranking of the engine is reached.

  The engine start control device for a hybrid vehicle according to the present invention can suppress a sudden change in driving force and reduce the occurrence of shock at the time of engine start.

FIG. 1 is a system configuration diagram of a start control device for a hybrid vehicle. (Example) FIG. 2 is a control block diagram for calculating the target engine operating point. (Example) FIG. 3 is a control block diagram for calculating a motor torque command value. (Example) FIG. 4 is a flowchart for calculating the target engine operating point. (Example) FIG. 5 is a flowchart for calculating the motor torque command value. (Example) FIG. 6 is a diagram showing changes in each torque until the engine speed increases. (Example) FIG. 7 is a collinear diagram at time Ta in FIG. (Example) FIG. 8 is a nomographic chart at time Tb in FIG. (Example) FIG. 9 is a collinear diagram at time Tc in FIG. (Example) FIG. 10 is an alignment chart at time Td in FIG. (Example) FIG. 11 is a diagram showing a target driving force search map. (Example) FIG. 12 shows a target charge / discharge power search table. (Example) FIG. 13 is a diagram showing a starting engine torque search map. (Example) FIG. 14 shows a target operating point search map. (Example) FIG. 15 is a collinear diagram when the vehicle is changed at the same engine operating point. (Example) FIG. 16 is a diagram showing each efficiency state on the equal power line. (Example) FIG. 17 is a collinear diagram showing each point (D, E, F) on the equal power line. (Example) FIG. 18 is a diagram showing the best line for engine efficiency and the best line for overall efficiency. (Example) FIG. 19 is a collinear diagram of the LOW gear ratio state. (Example) FIG. 20 is an alignment chart in the intermediate gear ratio state. (Example) FIG. 21 is a collinear diagram of the HIGH gear ratio state. (Example) FIG. 22 is a collinear diagram in a state where power circulation occurs. (Example)

  The present invention achieves the object of reducing the occurrence of a shock at the time of starting the engine by suppressing rapid fluctuations in the driving force by avoiding a step-like torque change when applying the torque necessary for starting the engine. Is.

1 to 22 show an embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes an engine start control device of a hybrid vehicle as an electric vehicle.
The engine start control device 1 includes an output shaft 3 of an engine (denoted as “ENG” in the drawing) 2 which is a driving source for outputting torque, and a first motor generator (in the drawing as a plurality of motor generators (electric motors)). In the drawing, it is denoted as “MG1”) 4 and a second motor generator (denoted as “MG2” in the drawing) 5, and a drive shaft (in the drawing as an output member) connected to the driving wheel 6 via the output transmission mechanism 7. 8), and a power transmission mechanism (differential gear mechanism) 9 coupled to the output shaft 3, the first motor generator 4, the second motor generator 5, and the drive shaft 8 of the engine 2, respectively. And. The plurality of motor generators includes a first motor generator (denoted as “MG1” in the drawing) 4 and a second motor generator (denoted as “MG2” in the drawing).
A one-way clutch 10 is provided in the middle of the output shaft 3 of the engine 2 on the engine 2 side. The one-way clutch 10 prevents the engine 2 from rotating in the reverse direction, and receives the reaction torque of the second motor generator 5 during EV (electric vehicle) traveling.
The first motor generator 4 includes a first rotor 11 and a first stator 12. The second motor generator 5 includes a second rotor 13 and a second stator 14.
The engine start control device 1 also includes a first inverter 15 that controls the operation of the first motor generator 4, a second inverter 16 that controls the operation of the second motor generator 5, the first inverter 15, Control means (drive control unit: ECU) 17 communicated with the second inverter 16 is provided.
The first inverter 15 is connected to the first stator 12 of the first motor generator 4. The second inverter 16 is connected to the second stator 14 of the second motor generator 5.
Each power supply terminal of the first inverter 15 and the second inverter 16 is connected to a battery (driving high voltage battery) 18. The battery 18 can exchange power with the first motor generator 4 and the second motor generator 5.
In the engine start control device 1, the hybrid vehicle is driven and controlled using outputs from the engine 2, the first motor generator 4, and the second motor generator 5.

The power transmission mechanism 9 is a so-called four-shaft power input / output device, which includes the output shaft 3 and the drive shaft 8 of the engine 2, and the first motor generator 4 on the engine 2 side and the drive shaft 8 side. The second motor generator 5 is arranged, the power of the engine 2, the power of the first motor generator 4 and the power of the second motor generator 5 are combined and output to the drive shaft 8, and the engine 2 and the second motor generator 5 are combined. Power is exchanged among one motor generator 4, second motor generator 5, and drive shaft 8.
That is, in the power transmission mechanism 9, four elements including the engine 2, the first motor generator 4, the second motor generator 5, and the drive shaft 8 as an output member are shown in FIGS. 7 to 10. The first motor generator (MG1) 4, the engine (ENG) 2, the drive shaft (OUT) 8 as an output member, and the second motor generator (MG2) 5 are connected in this order on the alignment chart. The gear mechanism is configured.

The power transmission mechanism 9 is configured by arranging a first planetary gear mechanism 19 and a second planetary gear mechanism 20 in which two rotation elements are connected to each other.
The first planetary gear mechanism 19 includes a first sun gear 21, a first pinion gear 22 that meshes with the first sun gear 21, and a first ring gear 23 that meshes with the first pinion gear 22. The first carrier 24 connected to the first pinion gear 22 and the output gear 25 connected to the first ring gear 23 are provided.
The second planetary gear mechanism 20 includes a second sun gear 26, a second pinion gear 27 meshed with the second sun gear 26, and a second ring gear 28 meshed with the second pinion gear 27. And a second carrier 29 connected to the second pinion gear 27.

In the power transmission mechanism 9, the first carrier 24 of the first planetary gear mechanism 19 is connected to the output shaft 3 of the engine 2. The second carrier 29 of the second planetary gear mechanism 20 is connected to the first ring gear 23 and the output gear 25 of the first planetary gear mechanism 19.
The first rotor 11 of the first motor generator 4 is connected to the first sun gear 21 via the first motor output shaft 30. The output shaft 3 of the engine 2 is connected to the first carrier 24 and the second sun gear 26. The drive shaft 8 is connected to the first ring gear 23 and the second carrier 29 via the output gear 25 and the output transmission mechanism 7. The second rotor 13 of the second motor generator 5 is connected to the second ring gear 28 via the second motor output shaft 31.
The second motor generator 5 includes a second motor output shaft 31, a second ring gear 28, a second carrier 29, a first ring gear 23, an output gear 25, an output transmission mechanism 7, and a drive shaft 8. Thus, the vehicle can be directly connected to the drive wheel 6 and the vehicle is driven only by a single output.
That is, in the power transmission mechanism 9, the first carrier 24 of the first planetary gear mechanism 19 and the second sun gear 26 of the second planetary gear mechanism 20 are coupled and connected to the output shaft 3 of the engine 2. The first ring gear 23 of the first planetary gear mechanism 19 and the second carrier 29 of the second planetary gear mechanism 20 are coupled and connected to the drive shaft 8, and the first planetary gear mechanism 19 The first motor generator 4 is connected to one sun gear 21, the second motor generator 5 is connected to the second ring gear 28 of the second planetary gear mechanism 20, the engine 2, the first motor generator 4, Power is exchanged between the second motor generator 5 and the drive shaft 8.
The control means 17 includes an accelerator operation amount detection means 32 for detecting the depression amount of the accelerator pedal as an accelerator operation amount, a vehicle speed detection means 33 for detecting the vehicle speed, and a battery charge state for detecting the state of charge (SOC) of the battery 18. The detection means 34 and the engine rotation speed detection means 35 for detecting the engine rotation speed communicate with each other.
In addition, an air amount adjustment mechanism 36, a fuel supply mechanism 37, and an ignition timing adjustment mechanism 38 communicate with the control means 17 so as to control the engine 2.

As shown in FIG. 1, the engine start control device 1 may be configured to include a brake mechanism 39 instead of the one-way clutch 10 as a mechanism for fixing the output shaft 3 of the engine 2. The brake mechanism 39 includes a brake rotor 40 that is integrally fixed to the output shaft 3 of the engine 2 and a brake shoe 41 that brakes the output shaft 3 by sandwiching the vicinity of the outer periphery of the brake rotor 40 from both sides. The brake shoe 41 is in communication with the control means 17.
The brake mechanism 39 opens in response to a command from the control means 17 when the torque acting on the output shaft 3 of the engine 2 becomes near zero (0) (Nm).
Further, the control means 17 is in communication with torque detection means 42 for detecting the actual torque of the first motor generator 4 and the second motor generator 5. The torque detection means 42 includes, for example, a torque sensor that directly detects the torque between the first motor generator 4 and the second motor generator 5. The torque detection means 42 may be a method of calculating a torque from power consumption by installing a current sensor in each coil of the first motor generator 4 and the second motor generator 5.

As shown in FIGS. 1 and 2, the control unit 17 includes a target driving force calculation unit 17A, a target driving power calculation unit 17B, a target charge / discharge power calculation unit 17C, a temporary target engine power calculation unit 17D, a target The engine torque calculation means 17E, the target engine speed calculation means 17F, the target engine power calculation means 17G, the target power calculation means 17H, and the motor torque command value calculation means 17I are provided.
The target driving force calculation unit 17A calculates a target driving force based on the accelerator operation amount detected by the accelerator operation amount detection unit 32 and the vehicle speed detected by the vehicle speed detection unit 33.
The target drive power calculation means 17B is based on the accelerator operation amount detected by the accelerator operation amount detection means 32 and the vehicle speed detected by the vehicle speed detection means 33, that is, the target drive calculated by the target drive force calculation means 17A. A target drive power is calculated based on the force and the vehicle speed detected by the vehicle speed detection means 33.
The target charge / discharge power calculation means 17C calculates the target charge / discharge power based on the state of charge of the battery 18 detected by the battery charge state detection means 34.
The temporary target engine power calculation unit 17D calculates the temporary target engine power based on the target drive power calculated by the target drive power calculation unit 17B and the target charge / discharge power calculated by the target charge / discharge power calculation unit 17C.
The target engine torque calculation means 17E calculates the torque value acting on the output shaft 3 of the engine 2 when the engine start request is generated when the engine 2 is started, and sets it as the target engine torque initial value at the engine start. The torque required for cranking 2 is calculated, and the target engine torque is gradually changed from the target engine torque initial value until the torque required for cranking of the engine 2 is reached.
The target engine speed calculation means 17F contacts the target engine torque calculation means 17E and calculates the target engine speed at the time of engine start.
The target engine power calculation unit 17G calculates the target engine power from the target engine rotation speed calculated by the target engine rotation speed calculation unit 17F and the target engine torque calculated by the target engine torque calculation unit 17E.
The target power calculation means 17H sets the difference between the target drive power calculated by the target drive power calculation means 17B and the target engine power calculated by the target engine power calculation means 17G as the target power.
The motor torque command value calculation means 17I calculates command torque values of the first motor generator and the second motor generator using a torque balance formula including the target engine torque and a power balance formula including the target power.

Then, when starting the engine 2, the engine start control device 1 gradually decreases the torque acting on the output shaft 3 of the engine 2 until the torque required for cranking of the engine 2 is reached. Change the engine torque gradually.
Further, in the engine start control device 1, when starting the engine 2, the first motor generator 4 finally generates a torque corresponding to the torque acting on the output shaft 3 of the engine 2 and the torque of the engine 2. The torque is gradually changed so as to be a torque obtained by adding the torque necessary for ranking, and the second motor generator 5 outputs a torque necessary for driving the hybrid vehicle.
In this embodiment, the time when the engine 2 is started means a period from when the engine start request is generated to when the engine 2 is cranked.

That is, in this embodiment, the output of the engine 2, the power of the first motor generator 4 and the second motor generator 5 are combined and output to the drive shaft 8, and the output shaft 3 of the engine 2 can be fixed. In a hybrid vehicle equipped with a brake mechanism 39, when starting the engine 2, the torque acting on the output shaft 3 of the engine 2 at the time when the engine start request is made is set as the initial value of the target engine torque at the start. The target engine torque is gradually changed to the torque required for cranking, the target engine power is calculated from the target engine speed and the target engine torque, and the target drive power and target calculated from the accelerator operation amount and the vehicle speed are calculated. A target power which is a target value of input / output power from the battery 18 is obtained from a difference from the engine power. Torque balance equation and power balance equation from the first motor generator 4 which includes a target power including the target engine torque, calculates a command torque value of the second motor generator 5.
In this hybrid vehicle, when starting the engine 2, the torque acting on the output shaft 3 of the engine 2 at the time when the engine start request is made is set as an initial value of the target engine torque at the start, The target engine torque is gradually changed from the starting target engine torque search map of FIG. 13 to the searched target engine torque, the target engine power is calculated from the target engine speed and the target engine torque, and the target calculated from the accelerator operation amount and the vehicle speed is calculated. A target power, which is a target value of input / output power from the battery 18, is obtained from the difference between the drive power and the target engine power, and the first motor generator is obtained from the torque balance type including the target engine torque and the electric balance type including the target power. The command torque value of the second motor generator is calculated.
Further, in this hybrid vehicle, when the output shaft 3 of the engine 2 is fixed by the brake mechanism 39, the brake is applied after the torque acting on the output shaft 3 of the engine 2 becomes near zero (0) (Nm). The mechanism 39 is opened and cranking of the engine 2 is started.
As a result, in a hybrid vehicle that can fix the output shaft 3 of the engine 2 with a four-shaft type, when applying the torque necessary for starting the engine 2 from EV traveling, the motor torque is gradually changed at the time of starting the engine. Thus, a shock at the time of starting the engine can be reduced.

Next, calculation of the target engine operating point (target engine speed, target engine torque) from the accelerator operation amount and the vehicle speed in this embodiment will be described based on the control block diagram of FIG. 2 and the flowchart of FIG.
As shown in FIG. 4, when the program of the control means 17 is started (step 101), first, various signals used for control are fetched (step 102), and the accelerator operation amount and the vehicle speed are calculated from the target driving force search map shown in FIG. The target driving force corresponding to the above is calculated (step 103). In this case, the high vehicle speed range when the accelerator operation amount is zero (0) is set to a negative value so that the driving force in the deceleration direction corresponding to the engine brake is obtained, while the creep travel can be performed in the low vehicle speed region. Positive value.
Then, a target drive power necessary for driving the hybrid vehicle with the target drive force is set by multiplying the target drive force and the vehicle speed (step 104).
Further, in order to control the state of charge (SOC) of the battery 18 within the normal use range, the target charge / discharge power is calculated from the target charge / discharge amount search table shown in FIG. 12 (step 105). In this case, when the state of charge (SOC) of the battery 18 is low, the charging power is increased to prevent overdischarge of the battery 18, and when the state of charge (SOC) of the battery 18 is high, the discharge power is increased. It is made larger to prevent overcharging. For convenience, the discharge side is treated as a positive value and the charge side is treated as a negative value.
A provisional target engine power to be output by the engine 2 is calculated from the target drive power and the target charge / discharge power (step 106). The provisional target engine power to be output by the engine 2 is a value obtained by adding (subtracting in the case of discharging) power for charging the battery 18 to power necessary for driving the hybrid vehicle. Here, since the charge side is handled as a negative value, the target charge / discharge power is subtracted from the target drive power to calculate the provisional target engine power.
Then, it is determined whether or not the control mode is a hybrid (HEV) mode (step 107).
If this step 107 is YES, a target engine operating point (target engine speed, target engine torque) in the hybrid (HEV) mode is calculated (step 108).
If step 107 is NO, it is determined whether there is a request to start the engine (step 109).
If this step 109 is NO, a target engine operating point (target engine speed, target engine torque) in the electric vehicle (EV) mode is calculated (step 110). For example, target engine rotation speed = 0 (rpm), target engine torque = 0 (Nm), and the like.
If step 109 is YES, a starting target engine speed at the start of the engine 2 is calculated (step 111). The starting target engine speed is calculated from the target engine operating point search map shown in FIG. 14 according to the temporary target engine power and the vehicle speed, or is a preset value.
Then, an initial value of the target engine torque at the time of engine start is set (step 112). The initial value of the target engine torque is the current torque that the one-way clutch 10 is receiving.
The current torque received by this one-way clutch 10 is
Current torque = K2 * actual second motor generator torque− (k1 + 1) * actual first motor generator torque
Is calculated by
It should be noted that this step 112 is executed only when the engine start request is changed to a state where there is no request for engine start.

Thereafter, a target engine torque at start-up at the time of engine start is calculated from the search map of FIG. 13 according to the actual engine speed (step 113). The starting target engine torque search map of FIG. 13 is a value set in advance based on the engine friction torque at the time of fuel cut so that the engine 2 can be cranked. When the engine rotation speed is near 0 (rpm), a value larger than the engine friction torque is set on the minus (−) side in consideration of the static friction coefficient.
Then, the rate of change of the target engine torque is limited (step 114). By limiting the rate of change of the target engine torque in this way, the target engine torque is reduced from the initial value of the target engine torque at the time of engine start obtained in step 112 to the target engine torque at start time obtained in step 113. Change gradually.
After the process of step 108, after the process of step 110 or after the process of step 114, the target engine power is calculated (step 115), and the target engine power is subtracted from the target drive power. The power is calculated (step 116). This target power is a value that means assist power by the power of the battery 18 when the target drive power is larger than the target engine power, while when the target engine power is larger than the target drive power. The value means the charging power to the battery 18.
Then, the program is returned (step 117).

As shown in FIG. 14, the target engine operating point search map includes the power transmission mechanism 9, the first motor generator 4, and the second motor generator 5 for the efficiency of the engine 2 on the equal power line. A line connecting and selecting points for each power that improve the overall efficiency taking into account the efficiency of the power transmission system is set as the target operation line. The target operation line is set for each vehicle speed. This set value may be obtained experimentally, or may be obtained by calculating from the efficiency of the engine 2, the first motor generator 4, and the second motor generator 5.
The target operation line is set to move to the high rotation side as the vehicle speed increases. This is due to the following reason.
When the same engine operating point is used as the target engine operating point regardless of the vehicle speed, as shown in FIG. 15, when the vehicle speed is low, the rotational speed of the first motor generator 4 becomes positive, and the first motor generator 4 is a generator, and the second motor generator 5 is an electric motor (state A in FIG. 15). Then, as the vehicle speed increases, the rotational speed of the first motor generator 4 approaches zero (0) (state B in FIG. 15). When the vehicle speed further increases, the rotational speed of the first motor generator 4 increases. In this state, the first motor generator 4 operates as an electric motor, and the second motor generator 5 operates as a generator (state C in FIG. 15).
When the vehicle speed is low (state A and state B in FIG. 15), power circulation does not occur, so the target operating point is generally engine efficiency as in the target operating line of vehicle speed = 40 km / h shown in FIG. Close to the good point.
However, when the vehicle speed is high (the state shown in FIG. 15C), the first motor generator 4 operates as an electric motor and the second motor generator 5 operates as a generator to generate power circulation. Decreases the efficiency.
Therefore, as shown by a point C in FIG. 16, even if the engine efficiency is good, the efficiency of the power transmission system is lowered, so that the overall efficiency is lowered.
Therefore, in order to prevent the power circulation from occurring in the high vehicle speed range, the rotational speed of the first motor generator 4 is set to zero (0) or more as shown by a point E in the alignment chart shown in FIG. However, since the engine operating point moves in the direction where the engine speed increases, the engine efficiency greatly decreases even if the efficiency of the power transmission system is improved, as shown by the point E in FIG. Overall efficiency is reduced.
Therefore, as shown in FIG. 16, a point with good engine efficiency as a whole is a point D between the two, and if this point D is set as a target engine operating point, the most efficient operation is possible.
FIG. 18 shows the three operating points, point C, point D, and point E, on the target operating point search map. In FIG. 18, when the vehicle speed is high, it is clear that the engine operating point where the overall efficiency is the best moves to the higher rotation side than the operating point where the engine efficiency is the best.

Next, with respect to the calculation of the target torque of the first motor generator 4 and the second motor generator 5 for setting the charge / discharge amount of the battery 18 to the target value while outputting the target driving force, the control block of FIG. This will be described with reference to the flowcharts of FIGS.
As shown in FIG. 5, when the program of the control means 17 is started (step 201), first, the rotational speed No of the drive shaft 8 of the first planetary gear mechanism 19 and the second planetary gear mechanism 20 is calculated from the vehicle speed. Then, the rotation speed Nmg1t of the first motor generator 4 and the rotation speed Nmg2t of the second motor generator 5 when the engine rotation speed becomes the target engine rotation speed Net are calculated (step 202). The rotation speed Nmg1t and the rotation speed Nmg2t are calculated by the following (Expression 1) and (Expression 2). This arithmetic expression is obtained from the relationship between the rotational speeds of the first planetary gear mechanism 19 and the second planetary gear mechanism 20.

    Nmg1t = (Net-No) * k1 + Net (Formula 1)

    Nmg2t = (No−Net) * k2 + No (Formula 2)

Here, in the above (Formula 1) and (Formula 2), as shown in FIGS.
k1: Lever ratio between the first motor generator (MG1) and the engine (ENG) when “1” is set between the engine (ENG) and the drive shaft (OUT) k2: Engine (ENG) and drive shaft (OUT) This is the lever ratio between the drive shaft (OUT) and the second motor generator (MG2) when the interval is “1”. That is, k1 and k2 are values determined by the gear ratio of the first planetary gear mechanism 19 and the second planetary gear mechanism 20.
Then, basic torque Tmg1i of first motor generator 4 is calculated from rotation speed Nmg1t, rotation speed Nmg2t, target power Pbatt, and target engine torque Tet (step 203). This basic torque Tmg1i is calculated by the following equation (3).

    Tmg1i = (Pbatt * 60 / 2π-Nmg2t * Tet / k2) / (Nmg1t + Nmg2t * (1 + k1) / k2) (Formula 3)

  This (Expression 3) represents a balance of torques input to the first planetary gear mechanism 19 and the second planetary gear mechanism 20 shown below (Expression 4), and the first motor generator 4 and the second planetary gear mechanism 20 It can be derived by solving simultaneous equations consisting of (Equation 5) indicating that the power generated or consumed by the motor generator 5 and the input / output power (Pbatt) to the battery 18 are equal.

    Tet + (1 + k1) * Tmg1i = k2 * Tmg2i (Formula 4)

    Nmg1t * Tmg1i * 2π / 60 + Nmg2t * Tmg2i * 2π / 60 = Pbatt (Formula 5)

In the torque balance type, as shown in the above (Formula 4), the target torque and the target engine torque of each of the plurality of motor generators 4 and 5 are converted into the machine motor. Is balanced based on the lever ratio based on the gear ratio of the power transmission mechanism 9 that is operatively connected.
Next, the basic torque Tmg2i of the second motor generator 5 is calculated from the basic torque Tmg1i and the target engine torque by the following (Equation 6) (step 204).

    Tmg2i = (Tet + (1 + k1) * Tmg1i) / k2 (Formula 6)

This (formula 6) is derived from the above formula (4).
Next, in order to bring the engine speed close to the target, the deviation from the target value of the engine speed is multiplied by a predetermined feedback gain set in advance, and the feedback correction torque Tmg1fb of the first motor generator 4 and the second motor The feedback correction torque Tmg2fb of the generator 5 is calculated (step 205).
Then, the target engine rotational acceleration is calculated from the engine rotational speed using (Equation 7) below (step 206).

    Net = (Net-Neto) / Tc (Expression 7)

In this (Equation 7),
Net: Target engine rotational acceleration
Net: Target engine speed
Neto: target engine speed previous value
Tc: This routine execution cycle
It is.

  Then, inertia correction torques of the first motor generator 4 and the second motor generator 5 are calculated from the target engine rotational acceleration using the following (Expression 8) and (Expression 9) (Step 207).

  Tmg1ine = (Img1 * (k1 + 1)) * 2π / 60 * Net + Ie * (k2 + 1 / k1 + k2 + 1) * 2π / 60 * Net (Equation 8)

  Tmg2ine = (Img2 * (− k2)) * 2π / 60 * Net + Ie * (k1 / k1 + k2 + 1) * 2π / 60 * Net (Equation 9)

In the above (Formula 8) and (Formula 9),
Tmg1ine: Inertia correction torque of the first motor generator
Tmg2ine: Inertia correction torque of the second motor generator
Img1: Inertia of the first motor generator
Img2: Inertia of the second motor generator
Net: Target engine rotational acceleration
Ie: Engine inertia
k1: Lever ratio between the first motor generator (MG1) and the engine (ENG) when “1” is set between the engine (ENG) and the drive shaft (OUT) k2: Engine (ENG) and drive shaft (OUT) This is the lever ratio between the drive shaft (OUT) and the second motor generator (MG2) when the interval is “1”.

Then, each feedback correction torque Tmg1fb, Tmg2fb and each inertia correction torque Tmg1ine, Tmg2ine are added to each basic torque Tmg1i, Tmg2i, and a torque command value Tmg1 which is a control command value of the first motor generator 4 and a second motor A torque command value Tmg2 that is a control command value for the generator 5 is calculated (step 208).
The torque command value Tmg1 of the first motor generator 4 is
Tmg1 = Tmg1i + Tmg1fb + Tmg1ine
Is calculated by
The torque command value Tmg2 of the second motor generator 5 is
Tmg2 = Tmg2i + Tmg2fb + Tmg2ine
Is calculated by
Then, by driving and controlling the first motor generator 4 and the second motor generator 5 with the calculated torque command values Tmg1 and Tmg2, the engine 2 can be started while suppressing the start shock of the engine 2. Further, charging / discharging of the battery 18 can be set as a target value while outputting a target driving force.
Thereafter, the program is returned (step 209).

FIG. 6 shows changes in the target engine torque, the target torque of the first motor generator 4, the target torque of the second motor generator 5, and the actual engine speed until the engine speed increases. Here, the torque output to the drive shaft 8 is constant.
At time Ta in FIG. 6, as shown in the collinear diagram of FIG. 7, EV traveling is performed, and the one-way clutch 10 receives the reaction torque of the second motor generator 5 and travels.
The time Tb in FIG. 6 is the timing when the engine start request is made, as shown in the alignment chart of FIG. Simultaneously with this engine start request, the current torque received by the one-way clutch 10 is set as the initial value of the target engine torque. The torques of the first motor generator 4 and the second motor generator 5 calculated from the initial values of the target engine torque are not different from the torque during EV travel, and there are no torque discontinuities.
At time Tc in FIG. 6, as shown in the nomogram of FIG. 9, the target engine torque is zero (0) (in the middle of gradually changing from the initial value of the target engine torque to the target engine torque at start-up. Nm). At this timing, the one-way clutch 10 is not receiving the reaction torque and is receiving the reaction torque of the second motor generator 5 with the torque of the first motor generator 4.
The time Td in FIG. 6 is a timing at which the target engine torque decreases to near the starting target engine torque and the engine rotation speed starts increasing, as shown in the collinear diagram of FIG.

19 to 22 show alignment charts in typical operation states.
Here, k1 and k2 are defined as follows.
k1 = ZR1 / ZS1
k2 = ZS2 / ZR2
here,
ZS1: Number of teeth of the first sun gear
ZR1: Number of teeth of the first ring gear
ZS2: Number of teeth of second sun gear
ZR2: Number of teeth of the second ring gear
It is.
Each operation state will be described with reference to the alignment charts of FIGS.
In the collinear charts of FIGS. 19 to 22, the rotational speed is the positive direction of the rotation direction of the engine 2, and the torque input to and output from each shaft is input in the same direction as the torque of the engine 2. Define the direction as positive. Therefore, when the drive shaft torque is positive, the torque to drive the vehicle rearward is being output (deceleration during forward travel, drive during reverse travel), while the drive shaft torque is In the negative case, a torque for driving the vehicle forward is output (driving when moving forward, decelerating when moving backward).
When the first motor generator 4 and the second motor generator 5 generate power or perform power running, heat is generated by the first inverter 15, the second inverter 16, the first motor generator 4, and the second motor generator 5. Therefore, the efficiency when converting between electrical energy and mechanical energy is not 100%, but for the sake of simplicity, the description will be made assuming that there is no loss.

In actuality, when loss is considered, control may be performed so that extra power is generated by the amount of energy lost due to loss.
(1), LOW gear ratio state (see FIG. 19)
The engine 2 travels and the rotation speed of the second motor generator 5 is zero (0). The alignment chart at this time is shown in FIG. Since the rotation speed of the second motor generator 5 is zero (0), no power is consumed. Therefore, when the battery 18 is not charged / discharged, it is not necessary to generate power with the first motor generator 4, so the torque command value Tmg1 of the first motor generator 4 is zero (0). Further, the ratio between the engine rotation speed and the drive shaft rotation speed is (1 + k2) / k2.
(2), intermediate gear ratio state (see FIG. 20)
The engine 2 travels and the rotation speeds of the first motor generator 4 and the second motor generator 5 are positive. The alignment chart at this time is shown in FIG. In this case, when the battery 18 is not charged / discharged, the first motor generator 4 is regenerated, and the regenerative power is used to power the second motor generator 5 (accelerating power by transmitting power to wheels (drive wheels)). (Or keep the equilibrium speed on an ascending slope).
(3), HIGH gear ratio state (see FIG. 21)
The vehicle is driven by the engine 2 and the rotation speed of the first motor generator 4 is zero (0). The alignment chart at this time is shown in FIG. Since the rotation speed of the first motor generator 4 is zero (0), no regeneration is performed. Accordingly, when the battery 18 is not charged / discharged, the second motor generator 5 is not powered or regenerated, and the torque command value Tmg2 of the second motor generator 5 is zero (0). Further, the ratio between the engine rotation speed and the drive shaft rotation speed is k1 / (1 + k1).
(4) State in which power circulation is occurring (see FIG. 22)
In a state where the vehicle speed is higher than the HIGH gear ratio state of FIG. 21, the first motor generator 4 is reversely rotated. In this state, the first motor generator 4 is powered and consumes power. Therefore, when the battery 18 is not charged / discharged, the second motor generator 5 is regenerated to generate power.

Although the embodiments of the present invention have been described above, the configuration of the above-described embodiments will be described for each claim.
First, in the first aspect of the invention, when the engine 2 is started, the torque acting on the output shaft 3 of the engine 2 is gradually reduced, and then the torque required for cranking the engine 2 is obtained. The engine torque is gradually changed until
Thereby, in order to avoid a step-like torque change when applying a torque required for engine start, a sudden fluctuation of the driving force can be suppressed and a shock at the time of engine start can be reduced.
In the second aspect of the present invention, the plurality of motor generators includes a first motor generator 4 and a second motor generator 5. Four elements composed of the engine 2, the first motor generator 4, the second motor generator 5, and the drive shaft 8 that is an output member are arranged on the nomographic chart, the first motor generator 4, the engine 2, and the output. A drive shaft 8 and a second motor generator 5 which are members are connected in this order to constitute a power transmission mechanism 9 as a gear mechanism. When starting the engine 2, the first motor generator 4 adds the torque corresponding to the torque finally acting on the output shaft 3 of the engine 2 and the torque necessary for cranking the engine 2. The second motor generator 5 outputs a torque necessary for driving the vehicle.
Accordingly, it is possible to output the torque necessary for starting the engine while outputting the torque necessary for traveling of the vehicle.
In the third aspect of the present invention, when starting the engine 2, the control means 17 calculates a torque value acting on the output shaft 3 of the engine 2 when an engine start request is generated, thereby calculating a target engine at the time of engine start. A target engine torque calculating means 17E that calculates a torque necessary for cranking the engine 2 as an initial torque value and gradually changes the target engine torque from the target engine torque initial value to a torque necessary for cranking the engine 2. A target engine speed calculating means 17F for calculating a target engine speed at the time of starting the engine, a target engine speed calculated by the target engine speed calculating means 17F and a target engine torque calculating means 17E. Target engine that calculates target engine power from engine torque A target driving power calculating means 17B for calculating a target driving power based on the accelerator operating amount detected by the accelerator operating amount detecting means 32 and the vehicle speed detected by the vehicle speed detecting means 33, and this target driving. Target power calculation means 17H that uses the difference between the target drive power calculated by the power calculation means 17B and the target engine power calculated by the target engine power calculation means 17G as the target power, a torque balance equation including the target engine torque, and a target Motor torque command value calculating means 17I for calculating command torque values of the first motor generator 4 and the second motor generator 5 using a power balance equation including electric power is provided.
Thereby, the target torques of the first motor generator 4 and the second motor generator 5 calculated from the target engine torque initial values at the time of starting the engine do not change from the target torques before the calculation, and thereafter the target torque is gradually changed. Therefore, it is possible to reduce a shock at the time of starting the engine by suppressing a rapid fluctuation of the driving force.
In the invention according to claim 4, the mechanism for fixing the output shaft 3 of the engine 2 is a brake mechanism 39. When the torque acting on the output shaft 3 of the engine 2 becomes near zero (0) (Nm), the brake mechanism 39 is released.
Thereby, generation | occurrence | production of the shock to a vehicle can be prevented.

1 Engine start control device
2 Engine (ENG)
4 First motor generator (MG1)
5 Second motor generator (MG2)
6 Drive wheels
8 Drive shaft (OUT)
9 Power transmission mechanism
15 First inverter
16 Second inverter
17 Control means
17A Target driving force calculation means
17B Target drive power calculation means
17C Target charge / discharge power calculation means
17D provisional target engine power calculation means
17E Target engine torque calculation means
17F Target engine speed calculation means
17G Target engine power calculation means
17H Target power calculation means
17I Motor torque command value calculation means
18 battery
32 Accelerator operation amount detection means
33 Vehicle speed detection means
34 Battery charge state detection means
35 Engine rotation speed detection means
39 Brake mechanism
42 Torque detection means

Claims (4)

In the engine start control device for a hybrid vehicle, which controls driving of the vehicle using outputs from the engine and a plurality of motor generators, and includes a mechanism for fixing the output shaft of the engine.
When starting the engine, after gradually reducing the torque acting on the output shaft of the engine, the engine torque is gradually changed until the torque required for cranking of the engine is reached. An engine start control device for a hybrid vehicle. The plurality of motor generators includes a first motor generator and a second motor generator,
Four elements composed of the engine, the first motor generator, the second motor generator, and an output member are arranged on the nomographic chart as the first motor generator, the engine, the output member, and the first member. When connecting the two motor generators in this order to form a gear mechanism and starting the engine,
The first motor generator gradually changes the torque so that the torque corresponding to the torque finally acting on the output shaft of the engine and the torque necessary for cranking of the engine are added. Output
2. The engine start control device for a hybrid vehicle according to claim 1, wherein the second motor generator outputs a torque necessary for driving the vehicle. In the engine start control device for a hybrid vehicle, which controls driving of the vehicle using outputs from the engine and a plurality of motor generators, and includes a mechanism for fixing the output shaft of the engine.
An accelerator operation amount detection means for detecting the accelerator operation amount is provided,
Vehicle speed detecting means for detecting the vehicle speed is provided;
When the engine is started, a torque value acting on the output shaft of the engine when an engine start request is generated is calculated as a target engine torque initial value at the time of engine start, and a torque required for cranking the engine is calculated. A target engine torque calculation means for gradually changing the target engine torque from the initial target engine torque value to a torque required for cranking the engine;
A target engine speed calculating means for calculating a target engine speed at the time of starting the engine;
Target engine power calculation means for calculating target engine power from the target engine rotation speed calculated by the target engine rotation speed calculation means and the target engine torque calculated by the target engine torque calculation means;
Target drive power calculation means for calculating target drive power based on the accelerator operation amount detected by the accelerator operation amount detection means and the vehicle speed detected by the vehicle speed detection means;
Target power calculation means for setting a target power as a difference between the target drive power calculated by the target drive power calculation means and the target engine power calculated by the target engine power calculation means;
Control means provided with motor torque command value calculating means for calculating command torque values of the plurality of motor generators using a torque balance formula including a target engine torque and a power balance formula including a target power is provided. An engine start control device for a hybrid vehicle. The mechanism for fixing the output shaft of the engine is a brake mechanism,
The engine of a hybrid vehicle according to any one of claims 1 to 3, wherein the brake mechanism opens when the torque acting on the output shaft of the engine becomes close to zero (Nm). Start control device.

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