Hybrid vehicle and hybrid vehicle control method

Abstract

To suppress a fastening shock of a clutch in transition from a series hybrid travel mode to a parallel hybrid travel mode.SOLUTION: A hybrid vehicle which travels selectively in one of an electric travel mode, a series hybrid travel mode and a parallel hybrid travel mode transitions from a first mode in which the engine is placed in operation in a high energy efficiency range to generate electric power to the parallel hybrid travel mode via a second mode in which the rotating speed of the engine is varied so as to reduce relative rotation of a pair of fastening elements of a clutch in a release state when transitioning from the series hybrid travel mode to the parallel hybrid travel mode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hybrid vehicle and a control method for a hybrid vehicle. [Background technology]

[0002] Patent Document 1 discloses a hybrid vehicle that has three driving modes: an EV (Electric Vehicle) driving mode in which the engine is stopped and the vehicle is driven by the traction motor, a series hybrid driving mode in which the engine drives a generator and the vehicle is driven by the traction motor, and a parallel hybrid driving mode in which the vehicle is driven by both the engine and the traction motor. This hybrid vehicle transitions from the series hybrid driving mode to the parallel hybrid driving mode by engaging a clutch that switches the connection between the engine and the traction motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-225034 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the hybrid vehicle of Patent Document 1, when operating the generator in series hybrid driving mode, only energy efficiency is considered, and the engine is operated in a high-efficiency driving range where energy efficiency is good. When switching from series hybrid driving mode to parallel hybrid driving mode, control is performed to gradually switch the clutch from a slipping state to a fully engaged state, but clutch engagement shock may still occur.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to suppress clutch engagement shock when transitioning from the series hybrid driving mode to the parallel hybrid driving mode. [Means for solving the problem]

[0006] According to one aspect of the present invention, a vehicle includes an engine, a generator driven by the engine to generate electricity, a power storage device charged with the electrical energy generated by the generator, a traction motor provided downstream of the engine in a power transmission path connecting the engine and drive wheels, the traction motor driving the drive wheels with at least one of the electrical energy generated by the generator and the electrical energy charged in the power storage device, a transmission provided downstream of the traction motor in the power transmission path, the transmission changing the speed of the power of the engine and the traction motor to drive the drive wheels, and a clutch connecting and disconnecting the transmission of power between the engine and the traction motor, and the vehicle travels by the driving force of the traction motor when the engine is stopped and the clutch is released. A hybrid vehicle that can be driven by selecting one of an electric driving mode, a series hybrid driving mode in which the generator is driven by the driving force of the engine and the clutch is disengaged to drive the vehicle by the driving force of the traction motor, and a parallel hybrid driving mode in which the clutch is engaged to drive the vehicle by the driving force of the engine and the traction motor, and when transitioning from the series hybrid driving mode to the parallel hybrid driving mode, the vehicle transitions from a first mode in which the engine is operated in a high energy efficiency range to generate electricity, through a second mode in which the rotational speed of the engine is changed so as to reduce the relative rotation of a pair of engagement elements of the clutch that is in a disengaged state, to the parallel hybrid driving mode. When the SOC of the power storage device falls below a first reference value while operating in the first mode, the mode is switched to the second mode, and when the SOC of the power storage device falls below a second reference value that is set smaller than the first reference value while operating in the second mode, the mode is shifted from the series hybrid driving mode to the parallel hybrid driving mode. A hybrid vehicle is provided.

[0007] A corresponding control method for a hybrid vehicle is also provided. [Effects of the Invention]

[0008] According to the above aspect, the vehicle transitions from a first mode in which the engine is operated in a high-energy-efficiency range to generate electricity to a second mode in which the engine speed is changed to reduce the relative rotation of a pair of engagement elements in a disengaged clutch, and then to a parallel hybrid driving mode. This allows the clutch to be engaged with reduced relative rotation between the engagement elements. This reduces clutch engagement shock when transitioning from the series hybrid driving mode to the parallel hybrid driving mode. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the controller and the main components connected to the controller. [Figure 3] FIG. 3 is a flowchart illustrating the control of switching the driving mode based on the SOC of the power storage device. [Figure 4] FIG. 4 is a conceptual diagram illustrating the control of switching the driving mode based on the SOC of the power storage device. [Figure 5] FIG. 5 is a diagram illustrating the setting of the engine rotation speed in the series hybrid driving mode. [Figure 6] FIG. 6 is a flowchart illustrating the control of switching the driving mode based on the vehicle speed. [Figure 7] FIG. 7 is a conceptual diagram illustrating the control of switching the driving mode based on the vehicle speed. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention (hereinafter referred to as the present embodiment) will be described with reference to the accompanying drawings.

[0011] (Hybrid vehicle configuration) First, a hybrid vehicle 100 according to this embodiment will be described with reference to FIG.

[0012] FIG. 1 is a schematic diagram of a hybrid vehicle 100. As shown in FIG.

[0013] 1, hybrid vehicle 100 includes an engine ENG, a rotating electric machine MG1 as a generator, a clutch CL, a rotating electric machine MG2 as a traction motor, a battery BAT as an electricity storage device, a torque converter TC, a transmission TM, drive wheels DW, a mechanical oil pump MP, an electric oil pump EP, a hydraulic control circuit 1, a controller 2 as a control device, and various sensors 3. Hybrid vehicle 100 transmits the driving force of at least one of engine ENG and rotating electric machine MG2 to drive wheels DW depending on the driving conditions.

[0014] The engine ENG is one of the drive sources that drives the drive wheels DW. The drive force of the engine ENG is transmitted to the drive wheels DW via the clutch CL, the torque converter TC, and the transmission TM. In other words, the clutch CL, the torque converter TC, and the transmission TM are provided in a power transmission path that connects the engine ENG and the drive wheels DW.

[0015] The rotating electric machine MG1 is a motor for starting the engine ENG. The rotating electric machine MG1 is provided downstream of the engine ENG in the power transmission path. Specifically, the rotating electric machine MG1 is provided between the engine ENG and the clutch CL. When the rotating electric machine MG1 is driven by the engine ENG or when regenerative control is being performed, the rotating electric machine MG1 functions as a generator. The electric energy generated by the rotating electric machine MG1 is charged into the battery BAT. Note that the rotating electric machine MG1 does not necessarily have to be provided in the power transmission path.

[0016] The clutch CL connects or disconnects the engine ENG and the rotating electric machine MG2 to connect or disconnect the transmission of power. The clutch CL is provided downstream of the engine ENG (downstream of the rotating electric machine MG1) in the power transmission path. Specifically, the clutch CL is provided between the engine ENG and the rotating electric machine MG2. When the clutch CL is engaged, that is, when the engine ENG and the rotating electric machine MG2 are connected by the clutch CL, the driving force of the engine ENG is transmitted to the drive wheels DW via the torque converter TC and the transmission TM.

[0017] The clutch CL has a pair of engagement elements PL1, PL2. One engagement element PL1 rotates integrally with the output shaft of the engine ENG and the rotating shaft of the rotating electric machine MG1, while the other engagement element PL2 rotates integrally with the rotating shaft of the rotating electric machine MG2 and the input shaft of the torque converter TC. The clutch CL is frictionally engaged by the engagement elements PL1 and PL2 coming into contact with each other.

[0018] The rotating electric machine MG2 is the other drive source that drives the drive wheels DW. The rotating electric machine MG2 drives the drive wheels DW using at least one of the electric energy generated by the rotating electric machine MG1 and the electric energy charged in the battery BAT. The rotating electric machine MG2 is provided downstream of the engine ENG in the power transmission path. Specifically, the rotating electric machine MG2 is provided between the clutch CL and the torque converter TC. The driving force of the rotating electric machine MG2 is transmitted to the drive wheels DW via the torque converter TC and the transmission TM. The rotating electric machine MG2 functions as a generator when driven by the engine ENG or when regenerative control is being performed. The rotating electric machine MG2 is configured so that its maximum output is greater than the maximum output of the rotating electric machine MG1.

[0019] The battery BAT is formed of, for example, a lithium ion secondary battery. Instead of the battery BAT, a capacitor or the like may be provided as a power storage device. The battery BAT is charged with electrical energy generated when the rotating electric machine MG1 is driven by the engine ENG and electrical energy generated when the rotating electric machines MG1 and MG2 are regeneratively controlled. The battery BAT supplies electrical energy for driving the rotating electric machines MG1 and MG2.

[0020] The torque converter TC is a driving force transmission device that transmits driving force from the engine ENG or the rotating electric machine MG2 to the transmission TM via oil as a fluid. The torque converter TC is provided downstream of the rotating electric machine MG2 in the power transmission path. Specifically, the torque converter TC is provided between the rotating electric machine MG2 and the transmission TM. The torque converter TC has a lock-up clutch LU.

[0021] When the lockup clutch LU is engaged, it directly connects the rotating electric machine MG2 and the drive wheels DW (specifically, the transmission TM). When the lockup clutch LU is engaged, that is, when the rotating electric machine MG2 and the transmission TM are connected by the lockup clutch LU, it is possible to increase the efficiency of power transmission of the driving force of the engine ENG or the rotating electric machine MG2 to the drive wheels DW.

[0022] The transmission TM changes the speed of the driving force of the engine ENG and the rotating electric machine MG2 transmitted from the torque converter TC and transmits it to the drive wheels DW. The transmission TM is provided downstream of the rotating electric machine MG2 in the power transmission path. Specifically, the transmission TM is provided between the torque converter TC and the drive wheels DW. The transmission TM may be a belt-type continuously variable transmission or a stepped transmission.

[0023] The mechanical oil pump MP pumps (supplies) oil to the hydraulic control circuit 1. The mechanical oil pump MP is driven by the driving force of the engine ENG.

[0024] The electric oil pump EP, together with the mechanical oil pump MP or independently, pressure-feeds (supplies) oil to the hydraulic control circuit 1. If the supply of oil from the mechanical oil pump MP to the hydraulic control circuit 1 is stopped or insufficient, the electric oil pump EP temporarily supplies oil to the hydraulic control circuit 1 based on a drive request to make up for the shortage of oil. The electric oil pump EP is driven by a pump drive motor PM.

[0025] The hydraulic control circuit 1 is comprised of multiple flow paths and multiple hydraulic control valves. The hydraulic control circuit 1 adjusts the pressure of oil supplied from the mechanical oil pump MP and the electric oil pump EP and supplies it to each part of the transmission TM. The hydraulic control circuit 1 also controls the hydraulic pressure of the clutch CL, lock-up clutch LU, etc. based on commands from the controller 2.

[0026] The controller 2 is composed of a microcomputer equipped with a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and input / output interfaces (I / O interfaces) 21, 22 (see FIG. 2). The controller 2 can also be composed of multiple microcomputers. Specifically, the controller 2 can also be composed of an ATCU (automatic transmission control unit) that controls the transmission TM, an SCU (shift control unit) that controls the shift range, an ECU (engine control unit) that controls the engine ENG, and the like.

[0027] The controller 2 controls the engine ENG, the hydraulic control circuit 1, the rotating electric machine MG1, and the rotating electric machine MG2 based on signals output from various sensors 3, etc. The controller 2 drives the hybrid vehicle 100 by selecting one of the following modes: an electric driving mode EV in which the engine ENG is stopped and the clutch CL is disengaged to drive the hybrid vehicle 100 using the driving force of the rotating electric machine MG2; a series hybrid driving mode SH in which the driving force of the engine ENG is used to cause the rotating electric machine MG1 to generate electricity and the clutch CL is disengaged to drive the hybrid vehicle 100 using the driving force of the rotating electric machine MG2; and a parallel hybrid driving mode PH in which the clutch CL is engaged to drive the hybrid vehicle 100 using the driving force of the engine ENG and the rotating electric machine MG2. The series hybrid driving mode SH includes a first mode SH1 and a second mode SH2. Details of the controller 2 will be described later.

[0028] The various sensors 3 are sensors that detect various parameters and include an accelerator opening detection sensor 31 that detects an accelerator opening (i.e., an acceleration request by the driver), a torque detection sensor 32 that detects the output torque of the engine ENG, a first rotational speed detection sensor 33 that detects the rotational speed of the rotating electric machine MG1, a second rotational speed detection sensor 34 that detects the rotational speed of the rotating electric machine MG2, a capacity detection sensor (oil pressure sensor) 35 that detects the capacity of the lock-up clutch LU, a battery voltage sensor 36 that detects the voltage value of the battery BAT, and a vehicle speed sensor 37 that detects the speed of the hybrid vehicle 100.

[0029] (Controller configuration) Next, the controller 2 will be described with reference to FIG.

[0030] FIG. 2 is a block diagram showing the controller 2 and the main components connected to the controller 2. As shown in FIG.

[0031] 2, the controller 2 includes an input interface 21, an output interface 22, a memory unit 23, an engine start motor control unit 24, a vehicle drive motor control unit 25, a hydraulic control circuit control unit 26 (hereinafter simply referred to as the circuit control unit 26), a determination unit 27, and an engine control unit 28, which are electrically connected to one another. The engine start motor control unit 24, the vehicle drive motor control unit 25, the circuit control unit 26, the determination unit 27, and the engine control unit 28 are virtual units that represent the functions of the controller 2 for controlling the hybrid vehicle 100, and do not represent physical entities.

[0032] The input interface 21 receives output signals from the various sensors 3 .

[0033] The storage unit 23 is a memory for temporarily storing output signals from the various sensors 3. The storage unit 23 also stores processing programs and algorithm programs executed by the engine start motor control unit 24, the vehicle drive motor control unit 25, and the circuit control unit 26. The storage unit 23 also stores SOC1, SOC2, and SOC3, which are thresholds for the SOC (State of Charge) of the battery BAT, and VT1, VT2, and VT3, which are thresholds for the vehicle speed V [m / s]. Details of SOC1, SOC2, and SOC3 and VT1, VT2, and VT3 will be described later in the section on driving mode switching control. In this embodiment, the storage unit 23 is built into the controller 2, but is not limited to this and may be provided separately from the controller 2, for example.

[0034] The engine start motor control command generated by processing of the engine start motor control unit 24, the vehicle drive motor control command generated by processing of the vehicle drive motor control unit 25, and the circuit control command generated by processing of the circuit control unit 26 are output to the rotating electric machine MG1, the rotating electric machine MG2, and the hydraulic control circuit 1, respectively, via the output interface 22.

[0035] The engine starting motor control unit 24 generates an engine starting motor control command based on the output signals output from the various sensors 3, and outputs the generated engine starting motor control command to the rotating electric machine MG1 via the output interface 22.

[0036] The vehicle drive motor control unit 25 generates a vehicle drive motor control command based on the output signals output from the various sensors 3, and outputs the generated vehicle drive motor control command to the rotating electric machine MG2 via the output interface 22.

[0037] The circuit control unit 26 generates a circuit control command based on the output signals output from the various sensors 3, and outputs the generated circuit control command to the hydraulic control circuit 1 via the output interface 22.

[0038] The circuit control unit 26 also has a clutch control module 261, a lockup clutch control module 262, and a transmission control module 263. The clutch control module 261 generates a clutch control command based on output signals output from the various sensors 3, and outputs the generated clutch control command to the hydraulic control circuit 1 via the output interface 22. The lockup clutch control module 262 generates a lockup clutch control command based on output signals output from the various sensors 3, and outputs the generated lockup clutch control command to the hydraulic control circuit 1 via the output interface 22. The transmission control module 263 generates a transmission control command based on output signals output from other various sensors (not shown), and outputs the generated transmission control command to the hydraulic control circuit 1 via the output interface 22.

[0039] The determination unit 27 performs various determinations based on the output signals output from the various sensors 3, and outputs the results of the various determinations to the engine start motor control unit 24, the vehicle drive motor control unit 25, or the circuit control unit .

[0040] The engine control unit 28 generates an engine control command based on the output signals output from the various sensors 3, and outputs the generated engine control command to the engine ENG via the output interface 22.

[0041] The engine start motor control unit 24, the vehicle drive motor control unit 25, the circuit control unit 26, the determination unit 27, and the engine control unit 28 will be described in detail later in the section on driving mode switching control.

[0042] (Driving mode switching control) Next, the control of switching the driving mode in the hybrid vehicle 100 will be described with reference to Figures 3 to 7. The control of switching the driving mode is performed by the controller 2 repeatedly executing the flows of Figures 3 and 6 at regular intervals.

[0043] First, the control of switching the driving mode based on the SOC of the battery BAT will be described with reference to FIGS.

[0044] Fig. 3 is a flowchart illustrating the control of switching between driving modes based on the SOC of the battery BAT. Fig. 4 is a conceptual diagram illustrating the control of switching between driving modes based on the SOC of the battery BAT. Fig. 5 is a diagram illustrating the setting of the engine rotation speed VE in the series hybrid driving mode SH.

[0045] The control of switching the driving mode based on the SOC of the battery BAT switches the driving mode when, for example, the vehicle speed V of the hybrid vehicle 100 is constant and the driving force D that drives the drive wheels DW is constant.

[0046] 3, the controller 2 detects the SOC of the battery BAT. Specifically, the battery voltage sensor 36 detects the voltage value of the battery BAT. The controller 2 estimates the SOC from the voltage value of the battery BAT detected by the battery voltage sensor 36 and input via the input interface 21.

[0047] In step S12, the determination unit 27 of the controller 2 determines whether the SOC of the battery BAT is smaller than SOC1, which is a threshold value that is preset and stored in the storage unit 23. SOC1 is set to, for example, 80%. If it is determined in step S12 that the SOC of the battery BAT is not smaller than SOC1, that is, is equal to or greater than SOC1, the process proceeds to step S13.

[0048] In step S13, the controller 2 sets the hybrid vehicle 100 to electric driving mode EV because the SOC of the battery BAT is 80% or higher and the remaining capacity is sufficient. Specifically, the clutch control module 261 disengages the clutch CL via the output interface 22. The engine control unit 28 stops the engine ENG via the output interface 22. In addition, the vehicle drive motor control unit 25 causes the rotating electric machine MG2 to output torque that drives the drive wheels DW via the output interface 22.

[0049] On the other hand, if it is determined in step S12 that the SOC of the battery BAT is lower than SOC1, the process proceeds to step S14.

[0050] In step S14, the determination unit 27 of the controller 2 determines whether the SOC of the battery BAT is smaller than SOC2, which is a threshold value that is preset and stored in the storage unit 23. SOC2 is set to a value smaller than SOC1, for example, 41%. This SOC2 is 1st This corresponds to the reference value. If it is determined in step S14 that the SOC of the battery BAT is not lower than SOC2, that is, is equal to or higher than SOC2, the process proceeds to step S15.

[0051] In step S15, since the SOC of the battery BAT is equal to or greater than 41% and less than 80%, and the remaining capacity is decreasing, the controller 2 sets the hybrid vehicle 100 to the first mode SH1 of the series hybrid driving mode SH (see FIG. 4). Specifically, the clutch control module 261 disengages the clutch CL via the output interface 22. The engine control unit 28 operates the engine ENG via the output interface 22 to output torque that drives the rotating electric machine MG1. The engine start motor control unit 24 operates the rotating electric machine MG1 as a generator via the output interface 22. The vehicle drive motor control unit 25 operates the rotating electric machine MG2 via the output interface 22 to output torque that drives the drive wheels DW.

[0052] In FIG. 5, the horizontal axis represents engine speed VE [rpm] and the vertical axis represents engine torque TE [N·m]. FIG. 5 also shows iso-fuel consumption curves A1, A2, and A3, which connect points at which fuel consumption rates are the same. Of the iso-fuel consumption curves A1, A2, and A3, iso-fuel consumption curve A2 has a lower fuel consumption rate than iso-fuel consumption curve A3, and iso-fuel consumption curve A1 has a lower fuel consumption rate than iso-fuel consumption curve A2. In other words, the point with the lowest fuel consumption rate is near the center of iso-fuel consumption curve A1. FIG. 5 also shows a minimum fuel consumption curve α, which connects points at which engine torque TE provides the least fuel consumption for each engine speed VE.

[0053] In the first mode SH1 of the series hybrid driving mode SH, the controller 2 sets the engine ENG to an engine rotation speed VE1 and adjusts the load on the generator to an engine torque TE1 so as to achieve the lowest fuel consumption rate. That is, the hybrid vehicle 100 generates electricity by operating the engine ENG in a high energy efficiency range.

[0054] On the other hand, if it is determined in step S14 of FIG. 3 that the SOC of the battery BAT is lower than SOC2, the process proceeds to step S16.

[0055] In step S16, the controller 2 determines whether the SOC of the battery BAT is smaller than SOC3, which is a threshold value that is preset and stored in the storage unit 23. SOC3 is set to a value that is even smaller than SOC2, for example, 40%. This SOC3 corresponds to the second reference value. If it is determined in step S16 that the SOC of the battery BAT is not lower than SOC3, that is, is equal to or higher than SOC3, the process proceeds to step S17.

[0056] In step S17, because the SOC of the battery BAT is equal to or greater than 40% but less than 41% and the remaining capacity is further decreasing, the controller 2 sets the hybrid vehicle 100 to the second mode SH2 of the series hybrid driving mode SH (see FIG. 4). Specifically, the clutch control module 261 disengages the clutch CL via the output interface 22. The engine control unit 28 operates the engine ENG via the output interface 22 to output torque that drives the rotating electric machine MG1. The engine start motor control unit 24 operates the rotating electric machine MG1 as a generator via the output interface 22. The vehicle drive motor control unit 25 operates the rotating electric machine MG2 via the output interface 22 to output torque that drives the drive wheels DW.

[0057] In a second mode SH2 of the series hybrid driving mode SH, the controller 2 changes the rotation speed of the engine ENG to reduce the relative rotation of the pair of engagement elements PL1, PL2 of the clutch CL, causing the rotating electric machine MG1 to generate electricity. Specifically, as shown in Fig. 5, the controller 2 sets the engine rotation speed VE2 to be the same as the rotation speed of the rotating electric machine MG2, and operates the engine by adjusting the load of the generator to the engine torque TE2 on the minimum fuel consumption curve α so that fuel consumption is minimized at that time. That is, in this embodiment, in the second mode SH2, the relative rotation of the pair of engagement elements PL1, PL2 of the clutch CL is zero.

[0058] In FIG. 5, engine rotation speed VE2 is lower than engine rotation speed VE1, but when the gear ratio of the transmission TM is low and the rotation speed of the rotating electrical machine MG2 is high, such as when climbing a steep slope at low speed, engine rotation speed VE2 may become equal to or higher than engine rotation speed VE1.

[0059] On the other hand, if it is determined in step S16 of FIG. 3 that the SOC of the battery BAT is lower than SOC3, the process proceeds to step S18.

[0060] In step S18, because the SOC of the battery BAT is less than 40% and the remaining capacity is further decreasing, the controller 2 sets the hybrid vehicle 100 to the parallel hybrid driving mode PH (see FIG. 4). The clutch control module 261 engages the clutch CL via the output interface 22. The engine control unit 28 operates the engine ENG via the output interface 22 to output torque that drives the drive wheels DW. The vehicle drive motor control unit 25 operates the rotating electric machine MG2 via the output interface 22 to output torque that drives the drive wheels DW.

[0061] As described above, when transitioning from series hybrid driving mode SH to parallel hybrid driving mode PH, the mode transitions from first mode SH1, in which the engine ENG is operated in a high-energy-efficiency range to generate electricity, to second mode SH2, in which the rotational speed of the engine ENG is changed to reduce the relative rotation of the pair of engagement elements PL1, PL2 of the disengaged clutch CL, and then to parallel hybrid driving mode PH. This allows the clutch CL to be engaged with reduced relative rotation between the engagement elements PL1, PL2. This reduces the engagement shock of the clutch CL when transitioning from series hybrid driving mode SH to parallel hybrid driving mode PH.

[0062] Furthermore, SOC2, which is the threshold for switching from first mode SH1 to second mode SH2 in series hybrid driving mode SH, is set to 41%, and SOC3, which is the threshold for switching from second mode SH2 to parallel hybrid driving mode PH, is set to 40%. Therefore, in series hybrid driving mode SH, most of the time is spent in first mode SH1, in which the engine ENG is operated in a high energy efficiency range to generate electricity, and the mode is switched to second mode SH2 only immediately before switching to parallel hybrid driving mode PH. This makes it possible to suppress deterioration in fuel consumption rate.

[0063] Next, the control of switching the driving mode based on the vehicle speed V will be described with reference to FIGS.

[0064] 6 is a flowchart illustrating the control of switching between driving modes based on the vehicle speed V. FIG. 7 is a conceptual diagram illustrating the control of switching between driving modes based on the vehicle speed V.

[0065] The control of switching the driving mode based on the vehicle speed V switches the driving mode when, for example, the driving force D that drives the drive wheels DW is constant and only the vehicle speed V increases in the hybrid vehicle 100. The flow of the control of switching the driving mode based on the vehicle speed V shown in Fig. 6 is executed together with the flow of the control of switching the driving mode based on the SOC of the battery BAT shown in Fig. 3.

[0066] 6, the controller 2 detects the vehicle speed V. Specifically, the vehicle speed sensor 37 detects the vehicle speed V and outputs an electrical signal corresponding to the vehicle speed V. The controller 2 receives the electrical signal corresponding to the vehicle speed V detected by the vehicle speed sensor 37 via the input interface 21.

[0067] In step S22, the determination unit 27 of the controller 2 determines whether the vehicle speed V is higher than VT1, which is a threshold value that is set in advance and stored in the memory unit 23. As shown in Fig. 7, VT1 is set to a smaller value of the driving force D as the vehicle speed V increases. If it is determined in step S22 that the vehicle speed V is not higher than VT1, that is, is equal to or lower than VT1 (for example, in Fig. 7, the vehicle speed increases from V1 to V2), the process proceeds to step S23.

[0068] In step S23, because vehicle speed V is sufficiently low, controller 2 sets hybrid vehicle 100 to electric power traveling mode EV. Details of electric power traveling mode EV are similar to those of step S13 in Figure 3, and therefore will not be described here.

[0069] On the other hand, if it is determined in step S22 that the vehicle speed V is higher than VT1, the process proceeds to step S24.

[0070] In step S24, the determination unit 27 of the controller 2 determines whether the vehicle speed V is higher than VT2, which is a threshold value that is set in advance and stored in the memory unit 23. As shown in FIG. 7, VT2 is a value of the driving force D that decreases as the vehicle speed V increases, and is set to a value greater than VT1. This VT2 corresponds to the reference value. If it is determined in step S24 that the vehicle speed V is not higher than VT2, that is, is equal to or less than VT2 (for example, in FIG. 7, the vehicle speed V increases from V2 to V3), the process proceeds to step S25.

[0071] In step S25, because vehicle speed V is increasing, controller 2 sets hybrid vehicle 100 to first mode SH1 of series hybrid driving mode SH. Details of first mode SH1 are the same as those of step S15 in FIG. 3, and therefore will not be described here.

[0072] On the other hand, if it is determined in step S24 that the vehicle speed V is higher than VT2, the process proceeds to step S26.

[0073] In step S26, the determination unit 27 of the controller 2 determines whether or not the vehicle speed V is higher than VT3, which is a threshold value that is set in advance and stored in the memory unit 23. As shown in Fig. 7, VT3 is a value of the driving force D that decreases as the vehicle speed V increases, and is set to a value even larger than VT2. If it is determined in step S26 that the vehicle speed V is not higher than VT3, that is, is equal to or less than VT3 (for example, in Fig. 7, the vehicle speed increases from V3 to V4), the process proceeds to step S27.

[0074] In step S27, because vehicle speed V is becoming even higher, controller 2 sets hybrid vehicle 100 to second mode SH2 of series hybrid driving mode SH. Details of second mode SH2 are the same as those of step S17 in FIG. 3, and therefore will not be described here.

[0075] On the other hand, if it is determined in step S26 that the vehicle speed V is higher than VT3 (for example, if the vehicle speed increases from V4 to V5 in FIG. 7), the process proceeds to step S28.

[0076] In step S28, because the vehicle speed V is becoming even higher, the controller 2 sets the hybrid vehicle 100 to the parallel hybrid driving mode PH. Details of the parallel hybrid driving mode PH are the same as those of step S18 in FIG. 3, and therefore will not be described here.

[0077] As described above, when transitioning from series hybrid driving mode SH to parallel hybrid driving mode PH, the mode transitions from first mode SH1, in which the engine ENG is operated in a high-energy-efficiency range to generate electricity, to second mode SH2, in which the rotational speed of the engine ENG is changed to reduce the relative rotation of the pair of engagement elements PL1, PL2 of the disengaged clutch CL, and then to parallel hybrid driving mode PH. This allows the clutch CL to be engaged with reduced relative rotation between the engagement elements PL1, PL2. This reduces the engagement shock of the clutch CL when transitioning from series hybrid driving mode SH to parallel hybrid driving mode PH.

[0078] As shown in FIG. 7, the difference between VT1, which is the threshold for switching from electric drive mode EV to first mode SH1 of series hybrid drive mode SH, and VT2, which is the threshold for switching from first mode SH1 to second mode SH2, is set large. In contrast, the difference between VT2, which is the threshold for switching from first mode SH1 to second mode SH2 in series hybrid drive mode SH, and VT3, which is the threshold for switching from second mode SH2 to parallel hybrid drive mode PH, is set very small. Therefore, in series hybrid drive mode SH, most of the time is spent in first mode SH1, in which the engine ENG is operated in a high energy efficiency range to generate electricity, and the mode is switched to second mode SH2 only immediately before switching to parallel hybrid drive mode PH. This prevents deterioration in fuel consumption.

[0079] (Action and effect) The configuration and effects of the present embodiment will now be described.

[0080] (1)(4) An electric travel motor comprising: an engine ENG; a rotating electric machine MG1 driven by the engine ENG to generate electricity; a battery BAT charged with the electric energy generated by the rotating electric machine MG1; a rotating electric machine MG2 provided downstream of the engine ENG in a power transmission path connecting the engine ENG and drive wheels DW, the rotating electric machine MG2 driving the drive wheels DW with at least one of the electric energy generated by the rotating electric machine MG1 and the electric energy charged in the battery BAT; a transmission TM provided downstream of the rotating electric machine MG2 in the power transmission path, the transmission TM changing the speed of the power of the engine ENG and the rotating electric machine MG2 to drive the drive wheels DW; and a clutch CL connecting and disconnecting the transmission of power between the engine ENG and the rotating electric machine MG2, the electric travel motor running by the driving force of the rotating electric machine MG2 when the engine ENG is stopped and the clutch CL is released. A hybrid vehicle 100 can travel in one of three modes: a series hybrid driving mode SH in which the driving force of the engine ENG is used to generate electricity at the rotating electric machine MG1 and the clutch CL is disengaged to travel using the driving force of the rotating electric machine MG2; and a parallel hybrid driving mode PH in which the clutch CL is engaged to travel using the driving force of the engine ENG and the rotating electric machine MG2. When transitioning from the series hybrid driving mode SH to the parallel hybrid driving mode PH, the hybrid vehicle transitions from a first mode SH1 in which the engine ENG is operated in a high energy efficiency range to generate electricity, through a second mode SH2 in which the rotational speed of the engine ENG is changed to reduce the relative rotation of the pair of engagement elements PL1, PL2 of the clutch CL in the disengaged state to generate electricity, and then to the parallel hybrid driving mode PH.

[0081] With this configuration, when transitioning from series hybrid driving mode SH to parallel hybrid driving mode PH, the system transitions from first mode SH1, in which the engine ENG is operated in a high-energy-efficiency range to generate electricity, to second mode SH2, in which the rotational speed of the engine ENG is changed to reduce the relative rotation of the pair of engagement elements PL1, PL2 of the clutch CL in the released state to generate electricity, and then to parallel hybrid driving mode PH. This allows the clutch CL to be engaged with reduced relative rotation between the engagement elements PL1, PL2. This reduces engagement shock of the clutch CL when transitioning from series hybrid driving mode SH to parallel hybrid driving mode PH.

[0082] (2) Furthermore, when the hybrid vehicle 100 is being driven in the first mode SH1, if the SOC of the battery BAT falls below a preset reference value (SOC2), the hybrid vehicle 100 switches to the second mode SH2.

[0083] According to this configuration, the first mode SH1 is switched to the second mode SH2 based on the SOC of the battery BAT. Therefore, for example, when the vehicle speed V is constant and the driving force D that drives the drive wheels DW is constant, the engagement shock of the clutch CL when transitioning from the series hybrid driving mode SH to the parallel hybrid driving mode PH can be suppressed.

[0084] (3) When hybrid vehicle 100 is being driven in first mode SH1, if vehicle speed V exceeds a preset reference value (VT2), hybrid vehicle 100 switches to second mode SH2.

[0085] According to this configuration, the first mode SH1 is switched to the second mode SH2 based on the vehicle speed V. For example, when the driving force D driving the drive wheels DW is constant and only the vehicle speed V increases, the engagement shock of the clutch CL when transitioning from the series hybrid driving mode SH to the parallel hybrid driving mode PH can be suppressed.

[0086] Although an embodiment of the present invention has been described above, the above embodiment merely shows one application example of the present invention, and is not intended to limit the technical scope of the present invention to the specific configuration of the above embodiment. [Explanation of symbols]

[0087] 100 Hybrid Vehicles BAT Battery (electricity storage device) CL Clutch DW drive wheel ENG Engine EV electric driving mode MG1 Rotating Electric Machine (Generator) MG2 rotating electric motor (driving motor) PH Parallel hybrid driving mode PL1 Fastening Elements PL2 Fastening Elements SH Series Hybrid Driving Mode SH1 1st mode SH2 2nd Mode TM transmission

Claims

1. The engine and a generator driven by the engine to generate electricity; an electricity storage device that is charged with the electrical energy generated by the generator; a traction motor that is provided downstream of the engine in a power transmission path that connects the engine and drive wheels, and that drives the drive wheels with at least one of the electric energy generated by the generator and the electric energy stored in the power storage device; a transmission provided downstream of the traction motor in the power transmission path, the transmission changing the speed of power from the engine and the traction motor to drive the drive wheels; a clutch that connects and disconnects the transmission of power between the engine and the traction motor, a series hybrid driving mode in which the generator is caused to generate electricity by the driving force of the engine and the clutch is released, and the vehicle is driven by the driving force of the driving motor; or a parallel hybrid driving mode in which the clutch is engaged and the vehicle is driven by the driving force of the engine and the driving motor, When transitioning from the series hybrid driving mode to the parallel hybrid driving mode, the mode transitions from a first mode in which the engine is operated in a high energy efficiency region to generate electricity, through a second mode in which the rotational speed of the engine is changed to reduce the relative rotation of a pair of engagement elements of the clutch in a released state to generate electricity, and then to the parallel hybrid driving mode; When the SOC of the power storage device falls below a first reference value while operating in the first mode, the mode is switched to the second mode; When the SOC of the power storage device falls below a second reference value that is set to be smaller than the first reference value while operating in the second mode, the vehicle transitions from the series hybrid driving mode to the parallel hybrid driving mode. Hybrid vehicle.

2. The engine and a generator driven by the engine to generate electricity; an electricity storage device that is charged with the electrical energy generated by the generator; a traction motor that is provided downstream of the engine in a power transmission path that connects the engine and drive wheels, and that drives the drive wheels with at least one of the electric energy generated by the generator and the electric energy stored in the power storage device; a transmission provided downstream of the traction motor in the power transmission path, the transmission changing the speed of power from the engine and the traction motor to drive the drive wheels; a clutch that connects and disconnects the transmission of power between the engine and the traction motor, A method for controlling a hybrid vehicle that runs by selecting one of an electric driving mode in which the engine is stopped and the clutch is released and the vehicle runs using the driving force of the driving motor, a series hybrid driving mode in which the generator is caused to generate electricity using the driving force of the engine and the clutch is released and the vehicle runs using the driving force of the driving motor, and a parallel hybrid driving mode in which the clutch is engaged and the vehicle runs using the driving force of the engine and the driving motor, When transitioning from the series hybrid driving mode to the parallel hybrid driving mode, the mode transitions from a first mode in which the engine is operated in a high energy efficiency region to generate electricity, through a second mode in which the rotational speed of the engine is changed to reduce the relative rotation of a pair of engagement elements of the clutch in a released state to generate electricity, and then to the parallel hybrid driving mode; When the SOC of the power storage device falls below a first reference value while operating in the first mode, the mode is switched to the second mode; When the SOC of the power storage device falls below a second reference value that is set to be smaller than the first reference value while operating in the second mode, the vehicle transitions from the series hybrid driving mode to the parallel hybrid driving mode. A method for controlling a hybrid vehicle.

Images