Hybrid vehicle

Abstract

To calculate an estimated rotation speed of a motor more appropriately when terminating assist control of the motor.SOLUTION: A hybrid vehicle includes: an engine; a motor; a clutch that connects the engine and the motor and disconnects them; a torque converter having a pump impeller connected to the motor, and a turbine runner; a transmission having an input shaft connected to the turbine runner and an output shaft connected to a drive wheel; and a control device that, when a starting condition for the engine is satisfied in an electric traveling mode for traveling by using only power from the motor, starts the engine by increasing a rotation speed of the engine by slip engagement of the clutch and by assist control of the motor. The control device calculates, in the electric traveling mode, an estimated rotation speed for termination, which is an estimated rotation speed of the motor when the assist control is terminated, on the basis a rotation speed of the motor, a rotation speed of the turbine runner, and a required torque for traveling.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a hybrid vehicle.

Background Art

[0002] Conventionally, as this type of hybrid vehicle, there has been proposed one including an engine, a motor, a clutch provided between the engine and the motor, a torque converter having a pump impeller and a turbine runner connected to the motor, and a transmission having an input shaft connected to the turbine runner and an output shaft connected to drive wheels (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a hybrid vehicle, when the starting condition of the engine is satisfied in the electric driving mode in which the vehicle runs using only the power from the motor, the engine is started by increasing the rotational speed of the engine through slip engagement of the clutch and assist control of the motor. Based on this, how to calculate the predicted rotational speed at the end, which is the predicted rotational speed of the motor when ending the assist control, has been an issue.

[0005] The main object of the hybrid vehicle of the present invention is to more appropriately calculate the predicted rotational speed of the motor when ending the assist control of the motor.

Means for Solving the Problems

[0006] The hybrid vehicle of the present invention has taken the following means to achieve the above main object.

[0007] The hybrid vehicle of the present invention an engine, a motor, a clutch that connects and disconnects the engine and the motor, a torque converter having a pump impeller and a turbine runner connected to the motor, a transmission having an input shaft connected to the turbine runner and an output shaft connected to drive wheels, a control device that, when the starting condition of the engine is satisfied in an electric driving mode in which the vehicle travels using only the power from the motor, increases the rotational speed of the engine by slip engagement of the clutch and assist control of the motor to start the engine, A hybrid vehicle comprising: The control device calculates a predicted rotational speed at the end, which is the predicted rotational speed of the motor when ending the assist control, based on the rotational speed of the motor, the rotational speed of the turbine runner, and the required torque for driving in the electric driving mode. This is the gist.

[0008] In the hybrid vehicle of the present invention, when the starting condition of the engine is satisfied in the electric driving mode in which the vehicle travels using only the power from the motor, the rotational speed of the engine is increased by slip engagement of the clutch and assist control of the motor to start the engine. In this case, in the electric driving mode, a predicted rotational speed at the end, which is the predicted rotational speed of the motor when ending the assist control, is calculated based on the rotational speed of the motor, the rotational speed of the turbine runner, and the required torque for driving. In this way, the predicted rotational speed at the end can be calculated more appropriately. The inventors confirmed this through analysis and the like.

[0009] In the hybrid vehicle of the present invention, the control device may calculate the predicted rotational speed at the end in consideration of the rate of change of the rotational speed of the turbine runner in the electric driving mode. Further, the control device may calculate the predicted rotational speed at the end in consideration of the inertia of the motor and the inertia of the turbine runner in the electric driving mode. By doing so, the predicted rotational speed at the end can be calculated more appropriately.

[0010] In the hybrid vehicle of the present invention, the control device may calculate the predicted rotational speed at the end in consideration of the smoothed required torque value obtained by smoothing the required torque and the predicted reaction torque of the torque converter obtained based on the rotational speed of the motor and the rotational speed of the turbine runner.

[0011] In this case, the control device may calculate the predicted rotational speed at the end by performing an initial value setting process of setting the rotational speed of the motor and the rotational speed of the turbine runner to the initial value of the predicted rotational speed of the motor and the initial value of the predicted rotational speed of the turbine runner, respectively, and a loop calculation process of repeatedly performing, a predetermined number of times, a process of calculating the predicted angular velocity of the motor at the i-th time based on the smoothed required torque value at the i-th time, the predicted reaction torque of the torque converter at the i-th time based on the predicted rotational speed of the turbine runner and the predicted rotational speed of the motor at the (i - 1)-th time, and calculating the predicted rotational speed of the motor at the i-th time based on the predicted angular velocity of the motor at the i-th time.

[0012] In the hybrid vehicle of the present invention, the start condition is a condition that the required torque is greater than the start threshold value, and the control device may set the start threshold value based on the predicted rotational speed at the end. Since the predicted rotational speed at the end can be calculated more appropriately as described above, the start threshold value can be set more appropriately, and the presence or absence of the establishment of the start condition can be determined more appropriately.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0014] Next, modes for carrying out the present invention will be described using examples.

Example

[0015] FIG. 1 is a configuration diagram showing an outline of the configuration of a hybrid vehicle 20 as an embodiment of the present invention. As shown in the figure, the hybrid vehicle 20 of the embodiment includes an engine 22, a motor 30, an inverter 32, a battery 36, a clutch K0, a torque converter 40, an automatic transmission 42, and a hybrid electronic control unit (hereinafter referred to as "HVECU") 70.

[0016] The engine 22 is configured as an internal combustion engine that outputs power using fuel such as gasoline or light oil from a fuel tank. A crankshaft 23 of the engine 22 is connected to a rotating shaft 31 (rotor) of the motor 30 via the clutch K0. The engine 22 is controlled for operation by an engine electronic control unit (hereinafter referred to as "engine ECU") 24.

[0017] The engine ECU 24 includes a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, although not shown. Signals from various sensors necessary for controlling the operation of the engine 22 are input to the engine ECU 24 via the input ports. Examples of the signals input to the engine ECU 24 include the crank angle θcr of the crankshaft 23 from the crank position sensor 23a that detects the rotational position of the crankshaft 23 of the engine 22, and the coolant temperature Tw of the engine 22 from a water temperature sensor (not shown) that detects the temperature of the coolant of the engine 22. Various control signals for controlling the operation of the engine 22 are output from the engine ECU 24 via the output ports. Examples of the signals output from the engine ECU 24 include a control signal to the throttle valve, a control signal to the fuel injection valve, and a control signal to the spark plug. The engine ECU 24 is connected to the HV ECU 70 via the communication port. The engine ECU 24 calculates the rotational speed Ne of the engine 22 based on the crank angle θcr of the crankshaft 23 from the crank position sensor 23a.

[0018] The motor 30 is configured as a synchronous generator motor and has a rotor with permanent magnets embedded in the rotor core and a stator with three-phase coils wound around the stator core. The rotating shaft 31 to which the rotor of this motor 30 is fixed is connected to the crankshaft 23 of the engine 22 via the clutch K0 and is also connected to the torque converter 40. The inverter 32 is used to drive the motor 30 and is connected to the power line 37. The motor 30 is rotationally driven by switching control of a plurality of switching elements of the inverter 32 by a motor electronic control unit (hereinafter referred to as "motor ECU") 34.

[0019] The motor ECU 34 includes a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, and communication ports, although not shown in the figure. Signals from various sensors necessary for driving and controlling the motor 30 are input to the motor ECU 34 via the input ports. Examples of the signals input to the motor ECU 34 include the rotational position θm of the rotor of the motor 30 from a rotational position sensor 30a that detects the rotational position of the rotor of the motor 30, and the phase currents Iu and Iv of each phase of the motor 30 from a current sensor that detects the phase current of each phase of the motor 30. Control signals to the inverter 32 and the like are output from the motor ECU 34 via the output ports. The motor ECU 34 is connected to the HV ECU 70 via a communication port. The motor ECU 34 calculates the electrical angle θe, angular velocity ωm, and rotational speed Nm of the motor 30 based on the rotational position θm of the rotor of the motor 30 from the rotational position sensor 30a.

[0020] The battery 36 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and is connected to the power line 37 together with the inverter 32.

[0021] The clutch K0 is configured as, for example, a hydraulically driven friction clutch, and is controlled by the HV ECU 70 to connect and disconnect the crankshaft 23 of the engine 22 and the rotary shaft 31 of the motor 30.

[0022] The torque converter 40 is configured as a general fluid transmission device, and amplifies and transmits the torque of the power of the rotary shaft 31 of the motor 30 to the input shaft 43 of the automatic transmission 42, or transmits it as it is without amplifying the torque. This torque converter 40 has an input-side pump impeller 40p connected to the rotary shaft 31 of the motor 30, an output-side turbine runner 40t connected to the input shaft 43 of the automatic transmission 42, a stator that rectifies the flow of the working oil from the turbine runner 40t to the pump impeller 40p, a one-way clutch that restricts the rotational direction of the stator in one direction, and a hydraulically driven lock-up clutch 40c that connects the pump impeller 40p and the turbine runner 40t.

[0023] The automatic transmission 42 is configured as a six-speed automatic transmission and includes an input shaft 43, an output shaft 44 connected to the drive wheels 49 via a differential gear 48, a plurality of planetary gears, and a plurality of hydraulically driven friction engagement elements (clutches, brakes). The automatic transmission 42 forms forward and reverse gears from the first speed to the sixth speed by engaging and disengaging the plurality of friction engagement elements, and transmits power between the input shaft 43 and the output shaft 44.

[0024] For the clutch K0, the lock-up clutch 40c, and the automatic transmission 42, the hydraulic pressure of the working oil from a mechanical oil pump or an electric oil pump is regulated and supplied by a hydraulic control device (not shown). The hydraulic control device includes a valve body in which a plurality of oil passages are formed, a plurality of regulator valves, a plurality of linear solenoid valves, and the like. This hydraulic control device is controlled by the HVECU 70.

[0025] The HVECU 70 includes, although not shown, a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, and communication ports. Signals from various sensors are input to the HVECU 70 via the input ports. Examples of the signals input to the HVECU 70 include the voltage Vb of the battery 36 from a voltage sensor 36a attached between the terminals of the battery 36, the current Ib of the battery 36 from a current sensor 36b attached to the output terminal of the battery 36, and the temperature Tb of the battery 36 from a temperature sensor 36c attached to the battery 36. Also included are the rotational speed Nin of the input shaft 43 (the rotational speed Nt of the turbine runner 40t) from a rotational speed sensor 43a attached to the input shaft 43 of the automatic transmission 42 and the rotational speed Nout of the output shaft 44 from a rotational speed sensor 44a attached to the output shaft 44 of the automatic transmission 42. Further examples include the ignition signal from the ignition switch 80 and the shift position SP from a shift position sensor 82 that detects the operating position of the shift lever 81. Additionally, there are the accelerator opening Acc from an accelerator pedal position sensor 84 that detects the depression amount of the accelerator pedal 83, the brake pedal position BP from a brake pedal position sensor 86 that detects the depression amount of the brake pedal 85, the vehicle speed V from a vehicle speed sensor 87, and the acceleration α from an acceleration sensor 88.

[0026] Various control signals are output from the HVECU 70 via the output ports. Examples of the signals output from the HVECU 70 include control signals to a hydraulic control device (the clutch K0, the lock-up clutch 40c of the torque converter 40, and the automatic transmission 42). The HVECU 70 is connected to the engine ECU 24 and the motor ECU 34 via the communication ports.

[0027] The HVECU 70 calculates the state of charge SOC of the battery 36 based on the current Ib of the battery 36 from the current sensor 36b, and calculates the output limit Wout as the allowable output power of the battery 36 based on the calculated state of charge SOC and the temperature Tb of the battery 36 from the temperature sensor 36c.

[0028] In the hybrid vehicle 20 of the embodiment configured in this way, the engine 22, the clutch K0, the motor 30, the torque converter 40 (lock-up clutch 40c), and the automatic transmission 42 are controlled so as to travel in a hybrid driving mode (HV driving mode) or an electric driving mode (EV driving mode) by the cooperative control of the HVECU 70, the engine ECU 24, and the motor ECU 34. Here, the HV driving mode is a mode in which the vehicle travels using the power from the engine 22 and the motor 30 with the clutch K0 engaged, and the EV driving mode is a mode in which the vehicle travels using only the power from the motor 30 with the clutch K0 disengaged.

[0029] In the control of the automatic transmission 42 in the HV driving mode and the EV driving mode, the HVECU 70 sets the target gear stage M* of the automatic transmission 42 based on the accelerator opening Acc and the vehicle speed V, and controls the automatic transmission 42 so that the gear stage M of the automatic transmission 42 becomes the target gear stage M*. Further, in the control of the lock-up clutch 40c in the HV driving mode and the EV driving mode, the lock-up clutch 40c is controlled based on the rotational speed Nm of the motor 30 and the like.

[0030] In the control of the engine 22 and the motor 30 in the HV running mode, the HVECU 70 first sets the required torque Torq required for the output shaft 44 of the automatic transmission 42 based on the accelerator opening Acc and the vehicle speed V. Subsequently, the rotation speed ratio Gt is calculated by dividing the rotation speed Nm of the motor 30 by the rotation speed Nout of the output shaft 44 of the automatic transmission 42, and the required torque Tmrq required for the rotation shaft 31 of the motor 30 is calculated by dividing the required torque Torq by the rotation speed ratio Gt. Then, the smoothing process is performed on the required torque Tmrq to set the target torque Tmtg, and the target torque Te* of the engine 22 and the torque command Tm* of the motor 30 are set so that the set target torque Tmtg is output to the rotation shaft 31 of the motor 30. The target torque Te* of the engine 22 is transmitted to the engine ECU 24 and the torque command Tm* of the motor 30 is transmitted to the motor ECU 34. Note that the torque command Tm* of the motor 30 is set within the range not exceeding the maximum allowable torque Tmmax of the motor 30. In the embodiment, the smaller of the rated maximum torque Tmrt of the motor 30 and the maximum torque Tmbt caused by the battery obtained by dividing the output limit Wout of the battery 36 by the rotation speed Nm of the motor 30 is used as the maximum allowable torque Tmmax. When receiving the target torque Te*, the engine ECU 24 performs the operation control (such as intake air amount control, fuel injection control, ignition control, etc.) of the engine 22 so that the engine 22 is operated at the target torque Te*. When receiving the torque command Tm*, the motor ECU 34 performs the switching control of a plurality of switching elements of the inverter 32 so that the motor 30 is driven by the torque command Tm*. In this HV running mode, when the stop condition of the engine 22 is satisfied, the stop process of the engine 22 is executed to shift to the EV running mode.

[0031] In the control of the motor 30 in the EV driving mode, the HV ECU 70 sets the required torque Tmrq and the target torque Tmtg of the rotating shaft 31 of the motor 30 in the same manner as in the HV driving mode, and sets the torque command Tm* of the motor 30 so that the set target torque Tmtg is output to the rotating shaft 31 of the motor 30, and transmits it to the motor ECU 34. Note that the torque command Tm* of the motor 30 is set within a range not exceeding the maximum allowable torque Tmmax of the motor 30. The control of the inverter 32 by the motor ECU 34 has been described above. In this EV driving mode, when the starting condition of the engine 22 is satisfied, the starting process of the engine 22 is executed to shift to the HV driving mode.

[0032] In the starting process of the engine 22, the rotation speed Ne of the engine 22 is increased and made to approach the rotation speed Nm of the motor 30 by the slip engagement of the clutch K0 and the assist control of the motor 30. After the rotation speed Ne of the engine 22 substantially coincides with the rotation speed Nm of the motor 30 due to the full engagement of the clutch K0, the fuel injection and ignition control of the engine 22 are started and the assist control is terminated. Here, in the assist control, within the range not exceeding the maximum allowable torque Tmmax of the motor 30, while increasing the rotation speed Ne of the engine 22, the torque of the sum of the target torque Tmtg and the assist torque Tmas is set as the torque command Tm* of the motor 30 to control the motor 30 (inverter 32) so that the target torque Tmtg is output to the rotating shaft 31 of the motor 30. The assist torque Tmas is determined by experiments, analysis, etc. Note that during the execution of the assist control, the required torque Tmrq may be upper-limited by the value when the starting condition of the engine 22 is satisfied.

[0033] Next, the operation of the hybrid vehicle 20 of the embodiment configured in this way, particularly the operation of determining whether or not the starting condition of the engine 22 is satisfied during driving in the EV driving mode, will be described. FIG. 2 is a flowchart showing an example of a starting determination routine executed by the HV ECU 70. This routine is repeatedly executed during driving in the EV driving mode.

[0034] When the start determination routine of FIG. 2 is executed, the HVECU 70 first inputs the predicted rotational speed Nmas at the end of the motor 30 (step S100). Here, the predicted rotational speed Nmas at the end of the motor 30 is the predicted rotational speed of the motor 30 when the assist control ends, and the value calculated by the predicted rotational speed calculation routine described later is input.

[0035] After inputting the predicted rotational speed Nmas at the end of the motor 30 in this way, the maximum allowable torque Tmmax of the motor 30 is set based on the input predicted rotational speed Nmas at the end of the motor 30 (step S110), and the torque obtained by subtracting the assist torque Tmas and the margin ΔTm of the motor 30 from the set maximum allowable torque Tmmax of the motor 30 is set as the start threshold Tst (step S120). FIG. 3 is an explanatory diagram showing an example of the relationship between the predicted rotational speed Nmas at the end of the motor 30, the maximum allowable torque Tmmax, and the start threshold Tst. Note that the margin ΔTm may not be used.

[0036] After setting the start threshold Tst in this way, the required torque Tmrq of the rotating shaft 31 of the motor 30 is compared with the start threshold Tst (step S130). When the required torque Tmrq of the rotating shaft 31 of the motor 30 is less than or equal to the start threshold Tst, it is determined that the start condition of the engine 22 is not satisfied (step S140), and this routine is terminated. In this case, the EV driving mode is continued. On the other hand, when the required torque Tmrq is greater than the start threshold Tst, it is determined that the start condition of the engine 22 is satisfied (step S150), and this routine is terminated. In this case, the start process of the engine 22 is executed and the vehicle shifts to the HV driving mode.

[0037] Next, the process of calculating the predicted rotational speed Nmas at the end of the motor 30 used in the start determination routine of FIG. 2 will be described using the predicted rotational speed calculation routine of FIG. 4. This routine is repeatedly executed in parallel with the start determination routine of FIG. 2 during driving in the EV driving mode.

[0038] When the predicted rotational speed calculation routine of FIG. 4 is executed, the HVECU 70 first inputs data such as the angular velocity ωm and rotational speed Nm of the motor 30, the rotational speed Nt of the turbine runner 40t, the required torque Tmrq and target torque Tmtg of the rotational axis 31 of the motor 30 (step S200). Here, as the angular velocity ωm and rotational speed Nm of the motor 30, values calculated based on the rotational position θm of the motor 30 from the rotational position sensor 30a are input. The rotational speed Nt of the turbine runner 40t is a value detected by the rotational speed sensor 43a and input. As described above, the required torque Tmrq is a value calculated by dividing the required torque Torq of the output shaft 44 of the automatic transmission 42 by the speed ratio Gt and input.

[0039] After inputting the data in this way, the value 0 is set to the variable i (step S210), and the angular velocity ωm and rotational speed Nm of the motor 30, the rotational speed Nt of the turbine runner 40t, and the target torque Tmtg are set to the predicted angular velocity ωmes[i], predicted rotational speed Nmes[i], predicted rotational speed Ntes[i] of the turbine runner 40t, and smoothed required torque value Tmrqes[i] of the motor 30 (step S220). Here, the predicted angular velocity ωmes[i], predicted rotational speed Nmes[i], predicted rotational speed Ntes[i], and smoothed required torque value Tmrqes[i] represent initial values used in the loop calculation process described later when the variable i has the value 0, and represent predicted values when the time (Δt·i), which is the product of the predetermined time Δt and the variable i, has elapsed in the loop calculation process when the variable i is a natural number. As the predetermined time Δt, for example, about several tens of msec is used. In addition, in the process of step S210, instead of the target torque Tmtg, the previous required torque (previous Tmrq) or the torque of the motor 30 estimated based on the electrical angle θe of the motor 30 and the phase currents Iu and Iv of each phase (the torque output to the rotational axis 31) may be set to the smoothed required torque value Tmrqes[i].

[0040] Subsequently, loop operation processing is executed until the variable i becomes equal to the value N (steps S230 to S290). Here, the value N is the time obtained by dividing the execution time Tas of the assist control in the starting process of the engine 22 by a predetermined time Δt. As a value determined by experiments or analyses, the execution time Tas of the assist control can be, for example, about several hundred msec.

[0041] In the loop operation processing, first, the variable i is incremented by 1 and updated (step S230). Subsequently, as shown in Expression (1), the i-th smoothed required torque value Tmrqes[i] is calculated using the required torque Tmrq of the rotation shaft 31 of the motor 30, the (i - 1)-th smoothed required torque value Tmrqes[i - 1], and the smoothing constant K (step S240). This smoothed required torque value Tmrqes[i] can be considered as a simulated predicted value (future value) of the target torque Tmtg based on the required torque Tmrq.

[0042] Tmrqes[i]=(Tmrq - Tmrqes[i - 1]) / K + Tmrqes[i - 1] (1)

[0043] Subsequently, as shown in Expression (1), the predicted reaction torque Ttc[i] of the torque converter 40 at the i-th time is calculated using the predicted rotational speed Nmes[i - 1] of the motor 30 at the (i - 1)-th time, the predicted rotational speed Ntes[i - 1] of the turbine runner 40t at the (i - 1)-th time, and the capacity coefficient Ct of the turbine runner 40t (step S250). Here, the predicted reaction torque Ttc[i] of the torque converter 40 is a predicted value of the reaction torque acting on the input side (rotation shaft 31 of the motor 30) of the torque converter 40 from the automatic transmission 42 side during running in the EV driving mode.

[0044] Ttc[i]=Ct·(Ntes[i - 1] / Nmes[i - 1])·Nmes[i - 1] 2 (2)

[0045] Then, as shown in Equation (3), the predicted angular velocity ωmes[i] of the motor 30 at the (i - 1)-th time, the demanded torque smoothing value Tmrqes[i] at the i-th time, the predicted reaction torque Ttc[i] of the torque converter 40 at the i-th time, the torque Tlup of the lock-up clutch 40c, the inertia Im of the motor 30, the inertia Itc of the torque converter 40, and a predetermined time Δt are used to calculate the predicted angular velocity ωmes[i] of the motor 30 at the i-th time (step S260). In the embodiment, during traveling in the EV traveling mode, the lock-up clutch 40c is released, and in Equation (3), the value 0 is used as the torque Tlup of the lock-up clutch 40c. As the inertia Im of the motor 30 and the inertia Itc of the torque converter 40, values determined by experiments or analysis can be used.

[0046] ωmes[i]=ωmes[i-1]+[(Tmrqes[i]-Ttc[i]-Tlup) / (Im+Itc)]·Δt (3)

[0047] When the predicted angular velocity ωmes[i] of the motor 30 at the i-th time is calculated in this way, according to Equation (4), the predicted angular velocity ωmes[i] of the motor 30 at the i-th time is converted into the predicted rotational speed Nmes[i] of the motor 30 at the i-th time (step S270). Subsequently, it is determined whether the variable i is equal to or less than the value N (step S280). This process is a process for determining whether to continue or end the loop calculation process (steps S230 to S290).

[0048] Nmes[i]=ωmes[i]·30 / π (4)

[0049] When it is determined in step S280 that the variable i is less than the value N, it is determined to continue the loop operation process. As shown in equation (5), the predicted rotational speed Ntes[i] of the turbine runner 40t at the (i - 1)-th time is calculated using the predicted rotational speed Ntes[i - 1] of the turbine runner 40t, the rotational speed change rate dNt / dt of the turbine runner 40t, and a predetermined time Δt (step S290), and then the process returns to step S230. Here, the rotational speed change rate dNt / dt of the turbine runner 40t is the predicted change amount per unit time of the rotational speed of the turbine runner 40t. For example, values based on the acceleration α from the acceleration sensor 88, the gear stage M of the automatic transmission 42, etc. can be used.

[0050] Ntes[i]=Ntes[i-1]+dNt / dt·Δt (5)

[0051] In this way, the processes of steps S230 to S290 are repeatedly executed. When it is determined in step S280 that the variable i is equal to the value N, it is determined to end the loop operation process. At this time, the predicted rotational speed Nmes[i] of the motor 30 is set as the predicted rotational speed Nmas at the end of the motor 30 (step S300), and this routine is ended. In this way, the predicted rotational speed Nmas at the end of the motor 30, that is, the predicted rotational speed of the motor 30 when ending the assist control by the motor 30, can be calculated more appropriately. The inventors confirmed this through analysis and the like.

[0052] FIG. 5 is an explanatory diagram showing an example of the state when starting the engine 22. In the example of FIG. 5, when the starting condition of the engine 22 is satisfied (at time t0), the rotational speed Ne of the engine 22 is increased with the slip engagement of the clutch K0 and the assist control of the motor 30 (output of the torque of the sum of the target torque Tmtg and the assist torque Tmas within the range of the maximum allowable torque Tmmax) to approach the rotational speed Nm of the motor 30. Then, when the rotational speed Ne of the engine 22 substantially matches the rotational speed Nm of the motor 30 due to the full engagement of the clutch K0 (at time t1), the fuel injection and ignition control of the engine 22 are started and the assist control is terminated. Therefore, in order to suppress the drop of the driving torque when starting the engine 22 while continuing the driving in the EV driving mode as long as possible, it is preferable to execute the starting process of the engine 22 when it is predicted that the sum of the target torque Tmtg and the assist torque Tmas approaches the maximum allowable torque Tmmax sufficiently at the predicted rotational speed Nmas at the end of the assist control, that is, at the end. Based on this, in the embodiment, the starting threshold Tst is set to the torque obtained by subtracting the assist torque Tmas and the margin ΔTm of the motor 30 from the maximum allowable torque Tmmax based on the predicted rotational speed Nmas at the end, and the establishment of the starting condition of the engine 22 is determined by comparing the required torque Tmrq with the starting threshold Tst. As described above, in the embodiment, since the predicted rotational speed Nmas at the end can be calculated more appropriately, the starting threshold Tst can be set more appropriately, and the presence or absence of the establishment of the starting condition can be determined more appropriately.

[0053] In the hybrid vehicle 20 of the embodiment described above, when the engine start condition is satisfied in the EV driving mode, as the engine start process of the engine 22, the rotation speed Ne of the engine 22 is increased by the slip engagement of the clutch K0 and the assist control of the motor 30 to start the engine 22. In this case, when in the EV driving mode, the predicted rotational speed Nmas at the end of the motor 30 is calculated using the angular velocity ωm and rotational speed Nm of the motor 30, the rotational speed Nt of the turbine runner 40t, and the required torque Tmrq, and the above-described formulas (1) to (5). Thereby, the predicted rotational speed Nmas at the end can be calculated more appropriately. As a result, the start threshold Tst based on the predicted rotational speed Nmas at the end can be set more appropriately, and the presence or absence of the establishment of the start condition can be determined more appropriately by comparing the required torque Tmrq with the start threshold Tst.

[0054] In the hybrid vehicle 20 of the embodiment, during traveling in the EV driving mode, the lock-up clutch 40c is released, and in formula (3), the value 0 is used as the torque Tlup of the lock-up clutch 40c. However, when the lock-up clutch 40c is in slip engagement, a torque estimated based on the hydraulic pressure supplied to the lock-up clutch 40c may be used.

[0055] In the hybrid vehicle 20 of the embodiment, in formula (5), the predicted rotational speed Ntes[i] of the turbine runner 40t at the i-th time is calculated using the rotational speed change rate dNt / dt of the turbine runner 40t. However, the predicted rotational speed Ntes[i] of the turbine runner 40t at the i-th time may be calculated without using the rotational speed change rate dNt / dt of the turbine runner 40t, that is, the predicted rotational speed Ntes[i - 1] of the turbine runner 40t at the (i - 1)-th time may be set as the predicted rotational speed Ntes[i] at the i-th time.

[0056] In the hybrid vehicle 20 of the embodiment, in the starting process of the engine 22, the rotational speed Ne of the engine 22 is increased by the slip engagement of the clutch K0 and the assist control of the motor 30 to approach the rotational speed Nm of the motor 30. After the rotational speed Ne of the engine 22 substantially matches the rotational speed Nm of the motor 30 by the full engagement of the clutch K0, the fuel injection and ignition control of the engine 22 are started and the assist control is terminated. However, in the starting process of the engine 22, before the full engagement of the clutch K0, that is, before the rotational speed Ne of the engine 22 substantially matches the rotational speed Nm of the motor 30, the fuel injection and ignition control of the engine 22 may be started and the assist control may be terminated. In this case, compared with the embodiment, the execution time Tas of the assist control becomes shorter, so the value N obtained by dividing this execution time Tas by the predetermined time Δt also becomes smaller.

[0057] In the hybrid vehicle 20 of the embodiment, the clutch K0 is configured as a hydraulically driven friction clutch, but it may also be configured as a dry clutch such as an electromagnetic clutch.

[0058] In the hybrid vehicle 20 of the embodiment, the automatic transmission 42 is configured as a six-speed automatic transmission, but it may also be configured as an automatic transmission with four speeds, five speeds, eight speeds, ten speeds, etc.

[0059] In the hybrid vehicle 20 of the embodiment, the engine ECU 24, the motor ECU 34, and the HV ECU 70 are provided. However, at least two of these may be integrally configured.

[0060] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section of means for solving the problems will be described. In the embodiment, the engine 22 corresponds to the "engine", the motor 30 corresponds to the "motor", the clutch K0 corresponds to the "clutch", the torque converter 40 corresponds to the "torque converter", the automatic transmission 42 corresponds to the "transmission", and the engine ECU 24, the motor ECU 34, and the HV ECU 70 correspond to the "control device".

[0061] Note that the correspondence between the main elements of the embodiments and the main elements of the invention described in the column of means for solving the problems is merely an example for specifically explaining the mode for carrying out the invention described in the column of means for solving the problems in the embodiments. Therefore, it does not limit the elements of the invention described in the column of means for solving the problems. That is, the interpretation of the invention described in the column of means for solving the problems should be made based on the description in that column, and the embodiments are merely specific examples of the invention described in the column of means for solving the problems.

[0062] As described above, the embodiments have been used to explain the mode for carrying out the present invention. However, the present invention is not limited to such embodiments, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention.

Industrial Applicability

[0063] The present invention can be used in the manufacturing industry of hybrid vehicles and the like.

Explanation of Reference Numerals

[0064] 20 Hybrid vehicle, 22 Engine, 23 Crankshaft, 23a Crank position sensor, 24 Engine ECU, 30 Motor, 30a Rotation position sensor, 31 Rotation shaft, 32 Inverter, 34 Motor ECU, 36 Battery, 36a Voltage sensor, 36b Current sensor, 36c Temperature sensor, 37 Power line, 40 Torque converter, 40c Lock-up clutch, 40p Pump impeller, 40t Turbine runner, 42 Automatic transmission, 43 Input shaft, 43a Rotational speed sensor, 44 Output shaft, 44a Rotational speed sensor, 48 Differential gear, 49 Driving wheel, 70 HVECU, 80 Ignition switch, 81 Shift lever, 82 Shift position sensor, 83 Accelerator pedal, 84 Accelerator pedal position sensor, 85 Brake pedal, 86 Brake pedal position sensor, 87 Vehicle speed sensor, 88 Acceleration sensor.

Claims

【Claim 1】 An engine, a motor, a clutch that connects and disconnects the engine and the motor, a torque converter having a pump impeller and a turbine runner connected to the motor, a transmission having an input shaft connected to the turbine runner and an output shaft connected to a drive wheel, a control device that, when a starting condition of the engine is satisfied in an electric driving mode in which the vehicle travels using only the power from the motor, increases the rotational speed of the engine by slip engagement of the clutch and assist control of the motor to start the engine, A hybrid vehicle comprising: The control device calculates a predicted rotational speed at the end, which is the predicted rotational speed of the motor when ending the assist control, based on the rotational speed of the motor, the rotational speed of the turbine runner, the rate of change of the rotational speed of the turbine runner, and the required torque for driving in the electric driving mode. Hybrid vehicle.

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