Control method and control device for a hybrid vehicle

Abstract

A first drive source (internal combustion engine (2) and first motor generator (3)), a second drive source (second motor generator (4)), a first clutch (9), and a second clutch (12) are provided. In the neutral mode, the first and second clutches (9, 12) are in the disengaged state, and the rear wheels (15) are driven by the third motor generator through power generation (16) of the first motor generator (3). In the parallel mode, the first and second clutches (9, 12) are in the engaged state, and the first and second drive sources drive the front wheels (1), and the third motor generator 16 drives the rear wheels (15). When switching from the neutral mode to the parallel mode, if the battery power is sufficient, simultaneous control of the front and rear rotational speeds of the two clutches (9, 12) is performed. If the battery power is insufficient, the two synchronization controls are performed sequentially.

Description

Technical Field

[0001] The present invention relates to a hybrid vehicle having: a first drive source and a second drive source; and two clutches for disconnecting / engaging the drive sources with the drive wheels, and for switching between a neutral mode in which the first and second drive sources are disconnected from the drive wheels and a parallel mode in which the first and second drive sources are connected to the drive wheels during vehicle operation. Background Technology

[0002] Patent Document 1 discloses a structure for a series hybrid vehicle, comprising: a first clutch for disengaging / engaging the internal combustion engine connected to a generator motor with the drive wheels; and a second clutch for disengaging / engaging the drive motor with the drive wheels. Switching between these two clutches allows for switching between a series hybrid mode and an engine-direct-drive mode. In each mode, one clutch is engaged and the other is disengaged. Therefore, for example, when switching from the engine-direct-drive mode to the series hybrid mode, synchronization control is performed on the forward and backward rotational speeds of the second clutch, which was previously disengaged. When the rotational speeds are synchronized, the second clutch is engaged. Then, a torque conversion between the two drive sources is performed, causing the transmitted torque of the first clutch to approach zero, and finally, the first clutch is disengaged. In other words, the switching control of the two clutches is performed sequentially.

[0003] Therefore, if the switching control of the two clutches is performed sequentially, the responsiveness of the mode switching is low.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2020-131880 Summary of the Invention

[0005] The control method or control device for a hybrid vehicle according to the present invention includes: a first drive source; a second drive source; a first clutch for disengaging / engaging the first drive source with drive wheels; and a second clutch for disengaging / engaging the second drive source with drive wheels.

[0006] While the vehicle is in motion, it can switch between a neutral mode where the first and second drive sources are disconnected from the drive wheels, and a parallel mode where the first and second drive sources are connected to the drive wheels.

[0007] At least one of the following two switching controls is implemented: a first switching control, which, during the switching from the neutral mode to the parallel mode, simultaneously performs synchronous control of the forward and backward rotational speeds of the first clutch and the second clutch for at least a portion of the time; and a second switching control, which, during the switching from the parallel mode to the neutral mode, simultaneously performs control that brings the transmitted torque of the first clutch close to zero and control that brings the transmitted torque of the second clutch close to zero for at least a portion of the time.

[0008] This improves the responsiveness of mode switching by simultaneously controlling the switching of two clutches for at least a portion of the time. Attached Figure Description

[0009] Figure 1 This is an explanatory diagram showing the structure of the powertrain system of one embodiment of the hybrid vehicle according to the present invention.

[0010] Figure 2 It is a characteristic diagram that shows the operating range of each driving mode for different vehicle speeds and target driving forces.

[0011] Figure 3 This is an explanatory diagram showing the torque transmission path in neutral mode.

[0012] Figure 4 This is an explanatory diagram showing the torque transmission path in parallel mode.

[0013] Figure 5 This is a flowchart illustrating the control process when switching from neutral mode to parallel mode.

[0014] Figure 6 This is a flowchart illustrating the control process when switching from parallel mode to neutral mode.

[0015] Figure 7 This is a timing diagram of the switch from neutral mode to parallel mode.

[0016] Figure 8 This is a timing diagram of the switch from parallel mode to idle mode.

[0017] Figure 9 This is a flowchart illustrating the control process when switching from parallel mode to neutral mode without a waiting spring mechanism.

[0018] Figure 10 This is a timing diagram of the switch from parallel mode to neutral mode without a waiting spring mechanism. Detailed Implementation

[0019] An embodiment of the present invention will now be described in detail with reference to the accompanying drawings. Figure 1This is an explanatory diagram illustrating a structural example of the powertrain system of a hybrid vehicle to which the present invention is applied. This embodiment applies the invention to a four-wheel drive vehicle where the rear wheels are driven by an electric motor, thus having two drive sources as the drive source on the front wheels. Furthermore, it is possible to select between driving using only the rear wheels or driving using all four wheels.

[0020] That is, the drive source for the front wheel 1 includes a first drive source and a second drive source. The first drive source includes an internal combustion engine 2 and a first electric generator 3 that is always linked to the internal combustion engine 2. The second drive source is composed of a second electric generator 4. The first electric generator 3 is mainly used for generating electricity, and the second electric generator 4 is mainly used for driving. The rotation shaft of the first electric generator 3, which serves as the output shaft of the first drive source, is directly connected to the first input shaft 6 of the transfer case 5. The rotation shaft of the second electric generator 4, which serves as the second drive source, is directly connected to the second input shaft 7 of the transfer case 5.

[0021] The transfer case 5 has an output shaft 10 connected to the front wheel 1. A first input shaft 6 is configured to transmit torque to the output shaft 10 via a gear train 8 and a first clutch 9 located within the gear train 8. A second input shaft 7 is configured to transmit torque to the output shaft 10 via a gear train 11 and a second clutch 12 located within the gear train 11. Both the first clutch 9 and the second clutch 12 are claw clutches supported on an intermediate shaft 13 for the gear selector. In one embodiment, they have actuators for actuating the gear selector and a waiting spring mechanism. Furthermore, in the illustrated example, the gear train 8 includes a combination of two gears with different gear ratios: a high-speed side and a low-speed side. The first clutch 9 selectively engages with either one. However, the selection of high and low speeds is not a key aspect of this invention; therefore, engagement with either one (e.g., the high-speed side) will be referred to as "engagement" below.

[0022] Similarly, in the illustrated example, there is a combination of two gears with different gear ratios, a high-speed side and a low-speed side, between the intermediate shaft 13 and the output shaft 10, with either one selected by a third clutch 14 on the intermediate shaft 13. However, the selection of high speed and low speed is not the focus of this invention, so the following description focuses on always selecting one (e.g., the high-speed side).

[0023] Therefore, the first clutch 9 disconnects / engages the first drive source (internal combustion engine 2 and first electric generator 3) with the front wheel 1, and the second clutch 12 disconnects / engages the second electric generator 4, which is the second drive source, with the front wheel 1.

[0024] Additionally, in the illustrated example, a third electric generator 16 is provided as a third drive source to drive the rear wheel 15, and the third electric generator 16 is substantially always linked to the rear wheel 15 via the gear train 17.

[0025] The first, second, and third electric generators 3, 4, and 16 are connected to the battery 18 via inverter devices (not shown). In this embodiment of the hybrid vehicle, a powertrain controller 21 is provided to control the entire powertrain system according to driver requests, etc. This powertrain controller 21 controls each of the electric generators 3, 4, and 16 via a motor controller 22. Furthermore, the powertrain controller 21 controls the internal combustion engine 2 via an engine controller 23, and controls each clutch 9, 12, and 14 of the transfer case 5 via a transmission controller 24.

[0026] Figure 2 This is a characteristic diagram representing the regions where vehicle speed (horizontal axis) and target driving force (vertical axis) are set as parameters. As shown in the figure, it is roughly divided into region (a) neutral mode, region (b) parallel mode, region (c) ICE mode, and region (d) series mode. In this embodiment, the switching control of the target is the switching between neutral mode (a) and parallel mode (b) which requests a driving force greater than that of neutral mode (a).

[0027] Furthermore, ICE mode (c) is a mode in which the engine operates using the output of the internal combustion engine 2 and the third electric generator 16 on the rear wheel 15 side, while series mode (d) is a mode in which the second electric generator 4 and the third electric generator 16 are driven by the power generated by the first electric generator 3.

[0028] Figure 3 This is an explanatory diagram showing the torque transmission path in neutral mode. In neutral mode, both the first clutch 9 and the second clutch 12 are disengaged. Furthermore, as mentioned earlier, the third clutch 14 is arbitrary, for example, engaged with the high-speed side. Therefore, the front wheels 1 are not driven. On the other hand, the rear wheels 15 are driven by the third electric generator 16, thereby enabling the vehicle to move.

[0029] In addition, the internal combustion engine 2 drives the first electric generator 3 to supply the generated electricity to the battery 18 or the third electric generator 16.

[0030] Figure 4This is an explanatory diagram showing the torque transmission path in parallel mode. In this parallel mode, both the first clutch 9 and the second clutch 12 are engaged, and the third clutch 14 is engaged, for example, with the high-speed side. Thus, the front wheels 1 are driven by both the first drive source (internal combustion engine 2 and first electric generator 3) and the second drive source (second electric generator 4). Simultaneously, the rear wheels 15 are driven by the third electric generator 16. Therefore, four-wheel drive is achieved. Furthermore, the first electric generator 3 in the first drive source is controlled to a low-level regenerative state, becoming a positive drive force as a whole, corresponding to the output of the internal combustion engine 2.

[0031] according to Figure 2 It is clearly understood that, for example, the vehicle switches between neutral and parallel modes while driving, depending on the increase or decrease of the target driving force (requested driving force). A higher responsiveness in this switching is preferable. Specifically, when the driver depresses the accelerator pedal to switch from neutral to parallel mode, if the driving mode switch is not completed within a short time, the vehicle's acceleration responsiveness will be insufficient.

[0032] During the switch from neutral mode to parallel mode, both clutches 9 and 12 switch from disengaged to engaged. Since clutches 9 and 12 are claw clutches, this switch is achieved by synchronizing their respective forward and backward rotational speeds and actuating the actuators during the synchronization phase. The synchronization control of the forward and backward rotational speeds of clutch 9 is performed using a first electric generator 3. The synchronization control of the forward and backward rotational speeds of clutch 12 is performed using a second electric generator 4. In this embodiment, to improve the responsiveness of the driving mode switch, two synchronization controls are initiated simultaneously assuming sufficient power in the battery 18. If the power is insufficient, to avoid excessive power depletion caused by repeated synchronization controls, the two synchronization controls are performed sequentially.

[0033] During the switch from parallel mode to neutral mode, both clutches 1 and 2 switch from engaged to disengaged. This switch is achieved by bringing the transmitted torque of each clutch 9 and 12 close to zero. When clutches 9 and 12 have waiting spring mechanisms, if the actuators are switched to the disengaged side beforehand, they will naturally disengage naturally through the waiting spring mechanisms when the transmitted torque becomes approximately zero. Control to bring the transmitted torque of clutch 9 close to zero is performed using a first electric generator 3. Control to bring the transmitted torque of clutch 12 close to zero is performed using a second electric generator 4. In this embodiment, two controls are initiated simultaneously to improve the responsiveness of the driving mode switching.

[0034] Next, according to Figure 5 The flowchart illustrates the control process when switching from neutral mode to parallel mode while driving.

[0035] In addition, Figure 5 Flowcharts and Figure 7 In the timing diagram, clutch 9 and clutch 12 are abbreviated as "CL1" and "CL2" respectively, and generator 3, generator 4, and generator 16 are abbreviated as "MG1", "MG2", and "MG3" respectively. In addition, internal combustion engine 2 is abbreviated as "ICE".

[0036] If a command to switch to parallel mode is received while driving in neutral mode, the mode switch to parallel mode begins (steps 1 and 2). First, in step 3, it is determined whether the power output from battery 18 is sufficient. If it is NO, proceed to step 19; if it is YES, proceed to steps 4 and beyond. The determination criterion for step 3 is, for example, set to half the power required for simultaneous synchronous control of the forward and backward rotational speeds of the two clutches 9 and 12.

[0037] In step 4, the synchronization control of the forward and backward rotational speeds of the first clutch 9 and the second clutch 12 begins simultaneously. As mentioned earlier, this is performed using the first electric generator 3 and the second electric generator 4, respectively. Next, in step 5, it is determined whether the synchronization of each clutch is completed simultaneously.

[0038] With both synchronizing operations completed simultaneously, the second clutch 12 is engaged first, followed by the first clutch 9 (steps 6 and 7). Engaging the second clutch 12 first allows for greater power generation from the first electric generator 3. Furthermore, engaging both simultaneously increases the impact of torque fluctuations, which is not preferable. Once the engagement of the two clutches 9 and 12 is complete, torque switching occurs between the first electric generator 3, the second electric generator 4, and the third electric generator 16 (step 8). That is, the torques of each generator are gradually varied until they reach their respective target torques in parallel mode. Once this torque switching is complete, the series of mode switching processes is finished (step 9).

[0039] If the result in step 5 is NO, then in step 10 it is determined whether the synchronization of the forward and backward rotational speeds of the second clutch 12 has been completed first. If the result in step 10 is YES, then while engaging the second clutch 12 (step 11), wait for the synchronization of the forward and backward rotational speeds of the first clutch 9 to be completed (step 12). If the synchronization is completed, then engage the first clutch 9 (step 13), and then perform torque conversion (step 14).

[0040] If NO is selected in step 10, then wait for the synchronization of the forward and backward rotational speeds of the second clutch 12 to be completed while engaging the first clutch 9 (step 15) (step 16). If synchronization is completed, then engage the second clutch 12 (step 17) and then perform torque conversion (step 18).

[0041] That is, if either of the two simultaneous synchronization controls completes its synchronization first, the already completed clutch engagement will proceed first. This avoids unnecessary waiting time.

[0042] If insufficient power is determined in step 3, proceed to steps 19 and onwards, performing two synchronization controls sequentially. First, the second electric generator 4 is used to initiate the synchronization control of the forward and backward rotation speeds of the second clutch 12 (step 19). If synchronization is complete (step 20), the second clutch 12 is engaged (step 21), and the required torque conversion is performed (step 22).

[0043] Next, the synchronization control of the forward and backward rotation speeds of the first clutch 9 is initiated using the first electric generator 3 (step 23). If synchronization is complete (step 24), the first clutch 9 is engaged (step 25) to perform the required torque conversion (step 26).

[0044] In this way, when power is insufficient and two synchronous controls are performed sequentially, the synchronization / engagement of the second clutch 12 is performed before that of the first clutch 9. Therefore, it is possible to ensure a relatively large power generation based on the first electric generator 3.

[0045] Figure 7 The timing diagram illustrates an example of switching from idle mode to parallel mode. More specifically, in Figure 5 The flowchart illustrates an example where the process is executed in the order of steps 1→2→3→4→5→7→8→9. In other words, it's an example where two synchronization controls begin and complete simultaneously.

[0046] exist Figure 7The diagram, starting from the top, sequentially displays the driving mode, the rotational speed (speed) of the second clutch 12, the position (disengagement / engagement) of the second clutch 12, the rotational speed (speed) of the first clutch 9, the position (disengagement / engagement) of the first clutch 9, the control mode (speed control or torque control) of the first electric generator 3 and the second electric generator 4, and the torque of the internal combustion engine 2 and the first, second, and third electric generators 3, 4, and 16. The driving mode column lists the current driving mode and the requested driving mode; the bottom of the diagram shows the neutral mode, and the top shows the parallel mode. The positions of the actuators and the actual gear selector are listed in the first clutch 9 and second clutch 12 columns; the bottom of the diagram shows the disengaged position, and the top shows the engaged position. In the column indicating the control mode of the first electric generator 3 and the second electric generator 4, the bottom indicates torque control, and the top indicates speed control. Additionally, in the torque column, values ​​above zero indicate power operation, and values ​​below indicate regenerative operation.

[0047] exist Figure 7 In the example, at time t1, a command is issued to switch from neutral mode to parallel mode. Simultaneously, synchronization control of the forward and backward rotational speeds of the first clutch 9 and the second clutch 12, utilizing the first electric generator 3 and the second electric generator 4, begins. Furthermore, speed control is applied to the first electric generator 3 and the second electric generator 4.

[0048] At time t2, the synchronization of the first clutch 9 and the second clutch 12 is completed simultaneously, therefore, as previously stated, the second clutch 12 engages first. After the engagement of the second clutch 12, the first clutch 9 engages at time t3. Moreover, after the engagement of the first clutch 9, the required torque is converted between the first, second, and third electric generators 3, 4, and 16 during the period from time t4 to time t5. In the initial neutral mode, the vehicle is driven by the third electric generator 16 driving the rear wheels 15. In the switched parallel mode, the front wheels 1 are driven by the first drive source (internal combustion engine 2 and first electric generator 3) and the second drive source (second electric generator 4), and the rear wheels 15 are driven by the third electric generator 16.

[0049] This simultaneous parallel execution of two synchronous controls improves the responsiveness of driving mode switching. In particular, the vehicle's acceleration responsiveness is enhanced when switching from neutral mode to parallel mode as the target driving force increases.

[0050] In addition, Figure 7 In the example, during the time interval t1 to t2 when synchronization control is performed, the first electric generator 3 enters the power operation state, but it may also enter the regenerative state depending on the conditions.

[0051] Next, according to Figure 6 The flowchart illustrates the control flow when switching from parallel mode to neutral mode while driving. If a command to switch to neutral mode is received while driving in parallel mode (step 31), the actuators of the first clutch 9 and the second clutch 12 are simultaneously moved to the disengaged position (step 32). As previously described, the first clutch 9 and the second clutch 12 have waiting spring mechanisms. Therefore, even when the actuators are disengaged, the gear selector does not actually move, provided that the transmitted torque is active. When the transmitted torque becomes essentially zero, the gear selector moves naturally, and clutches 9 and 12 become disengaged.

[0052] Next, in step 33, torque conversion begins. Specifically, the torque of the first drive source (internal combustion engine 2 and first electric generator 3) is gradually reduced so that the transmitted torque of the first clutch 9 approaches zero. Similarly, the torque of the second electric generator 4, which is the second drive source, is gradually reduced so that the transmitted torque of the second clutch 12 approaches zero. Furthermore, the torque of the third electric generator 16 is gradually increased to maintain the overall driving force of the vehicle.

[0053] During the process of bringing the transmitted torque of each clutch 9 and 12 close to zero, it is determined whether the first clutch 9 or the second clutch 12 has actually disengaged (step 34). In addition, as a detection of clutch disengagement, the position of the gear selector of the claw clutch can be detected by a sensor, or clutch disengagement can be detected based on torque changes, etc.

[0054] In the next step 35, it is determined whether the first clutch 9 and the second clutch 12 have disengaged simultaneously. If they have disengaged simultaneously, the torques of the first, second, and third electric generators 3, 4, and 16 are immediately set to their respective target torques (step 36). Furthermore, after shifting to neutral mode, the target torque of the second electric generator 4 becomes zero, the target torque of the first electric generator 3 becomes a negative value for power generation, and the target torque of the third electric generator 16 becomes a positive value required for driving. Once each reaches its target torque, the series of mode switching processes are completed (step 37).

[0055] If the second clutch 12 is disengaged first (NO in step 35, YES in step 38), proceed to step 39, immediately set the torque of the second electric generator 4 to the target torque of zero, and increase the torque of the third electric generator 16 in a stepwise manner to offset the torque step difference associated with the disengagement of the second clutch 12.

[0056] Then, wait for the first clutch 9 to disengage (step 40). If the first clutch 9 disengages, set the torque of the first electric generator 3 and the torque of the third electric generator 16 to the aforementioned target torque (step 41). Once the target torque is reached, the series of mode switching processes are completed (step 37).

[0057] If the first clutch 9 is disengaged first (NO in step 35, NO in step 38), proceed to step 42, immediately set the torque of the first electric generator 3 to the target torque (a negative value for power generation), and increase the torque of the third electric generator 16 stepwise in a manner that offsets the torque step difference associated with the disengagement of the first clutch 9.

[0058] Then, wait for the second clutch 12 to disengage (step 43). If the second clutch 12 disengages, set the torque of the second electric generator 4 and the torque of the third electric generator 16 to the aforementioned target torque (step 44). Once the target torque is reached, the series of mode switching processes are completed (step 37).

[0059] Figure 8 The timing diagram illustrates an example of switching from parallel mode to idle mode. More specifically, in Figure 6 The flowchart shows an example where the processing is carried out in the order of steps 31→32→33→34→35→38→39→40→41→37. That is, an example where the second clutch 12 disengages before the first clutch 9.

[0060] exist Figure 8 In the example, at time t1, a command is issued to switch from parallel mode to neutral mode, switching the actuators of the first clutch 9 and the second clutch 12 to the disengaged side. Simultaneously, the first electric generator 3 and the second electric generator 4 are controlled to bring the transmitted torque of the first clutch 9 and the second clutch 12 close to zero. The third electric generator 16 gradually increases the driving force to maintain the overall driving force of the vehicle. Furthermore, torque control is performed on the first electric generator 3 and the second electric generator 4.

[0061] At time t2, the second clutch 12 first disengages, and the torque of the second electric generator 4 becomes zero. To compensate for the torque step difference, the torque of the third electric generator 16 simultaneously increases in a stepwise manner.

[0062] Then, at time t3, the first clutch 9 is disengaged, and the torque of the first electric generator 3 becomes negative of the target torque. At this time, to compensate for the torque step difference, the torque of the third electric generator 16 is increased in a stepwise manner. Finally, the mode switch is completed at time t3.

[0063] In this way, the control that makes the transmitted torque of the first clutch 9 approach zero and the control that makes the transmitted torque of the second clutch 12 approach zero are both executed in parallel for at least a part of the period, thereby improving the responsiveness of the driving mode switching from parallel mode to neutral mode.

[0064] Next, refer to Figure 9 Flowchart and Figure 10 The timing diagram illustrates the control during the switching from parallel mode to neutral mode in the second embodiment where the first clutch 9 and the second clutch 12 do not have a waiting spring mechanism.

[0065] exist Figure 9 In the flowchart, if a command to switch to neutral mode is received while driving in parallel mode (step 51), torque conversion begins in step 52. Specifically, the torque of the first drive source (internal combustion engine 2 and first electric generator 3) is gradually reduced so that the transmitted torque of the first clutch 9 approaches zero; similarly, the torque of the second electric generator 4, which is the second drive source, is gradually reduced so that the transmitted torque of the second clutch 12 approaches zero. Furthermore, the torque of the third electric generator 16 is gradually increased to maintain the overall driving force of the vehicle.

[0066] In this process, while bringing the transmitted torque of each clutch 9 and 12 close to zero, it is repeatedly determined whether the transmitted torque of the first clutch 9 or the second clutch 12 is less than the specified torque (G1, G2) set for each clutch (step 53). Here, the specified torques G1 and G2 are set such that the acceleration (G) of the vehicle generated when each clutch is disengaged reaches a level that will not cause disharmony to the occupants.

[0067] In the next step 54, it is determined whether the transmitted torques of the first clutch 9 and the second clutch 12 are simultaneously less than the specified torques G1 and G2. If they are both less than the specified torques, proceed to step 55, and control the actuator of the first clutch 9 to the disengaged position. Next, based on the confirmation that the transmitted torque of the second clutch 12 is less than the specified torque G2 (step 56), control the actuator of the second clutch 12 to the disengaged position (step 57).

[0068] Neither the first clutch 9 nor the second clutch 12 has a waiting spring mechanism, so the gear selector is activated and disengaged based on the actuator's action. Upon disengagement, the transmitted torque is sufficiently reduced, resulting in less impact in the vehicle. Furthermore, disengaging the first clutch 9 first ensures a relatively large power output from the first electric generator 3.

[0069] If the transmitted torque of the first clutch 9 is initially less than the specified torque G1 (NO in step 54, YES in step 58), proceed to step 55 as described above, and control the actuator of the first clutch 9 to the disengaged position. Next, wait for the transmitted torque of the second clutch 12 to be less than the specified torque G2 (step 56), and while it is less than the specified torque G2, control the actuator of the second clutch 12 to the disengaged position (step 57).

[0070] If the transmitted torque of the second clutch 12 is initially less than the specified torque G2 (NO in both step 54 and step 58), the actuator of the second clutch 12 is controlled to the disengaged position (step 59), and then the transmission torque of the first clutch 9 is waited for to become less than the specified torque G1 (step 60). During the stage where the torque is less than the specified torque G1, the actuator of the first clutch 9 is controlled to the disengaged position (step 61).

[0071] Figure 10 The timing diagram illustrates an example where the transmitted torque of clutch 9 is initially less than the specified torque. Specifically, in... Figure 9 The flowchart shows an example of a process where steps 51 → 52 → 53 → 54 → 58 → 55 → 56 → 57 are performed in that order.

[0072] exist Figure 10 In the example, at time t1, a command is issued to switch from parallel mode to neutral mode, utilizing the simultaneous activation of the first electric generator 3 and the second electric generator 4 to bring the transmitted torque of the first clutch 9 and the second clutch 12 close to zero. The third electric generator 16 gradually increases the driving force to maintain the overall driving force of the vehicle. Furthermore, torque control is performed on the first electric generator 3 and the second electric generator 4.

[0073] At time t2, the transmitted torque of the first clutch 9 is less than the specified torque G1, and the actuator of the first clutch 9 is controlled to the disengaged position. If the disengagement of the first clutch 9 is detected at time t3, the torque of the first electric generator 3 becomes the negative value of the target torque. Furthermore, in the illustrated example, in order to compensate for the torque step difference, the torque of the third electric generator 16 is increased stepwise.

[0074] Then, at time t4, the transmitted torque of the second clutch 12 is less than the specified torque G2, and the actuator of the second clutch 12 is controlled to the disengaged position. If the disengagement of the second clutch 12 is detected at time t5, the torque of the second electric generator 4 becomes 0, which is the target torque. Furthermore, in the illustrated example, in order to compensate for the torque step difference, the torque of the third electric generator 16 is increased stepwise. Finally, the mode switching is completed at time t5.

[0075] In this way, the control that makes the transmitted torque of the first clutch 9 approach zero and the control that makes the transmitted torque of the second clutch 12 approach zero are both executed in parallel for at least a portion of the time, thereby improving the responsiveness of the driving mode switching from parallel mode to neutral mode.

[0076] The present invention has been described in detail above with respect to one embodiment, but the present invention is not limited to the above embodiment and various modifications can be made. For example, in the above embodiment, a four-wheel drive vehicle using the third electric generator 16 to drive the rear wheel 15 was described as an example, but in the case of inertial driving in neutral mode, the switching between the neutral mode and the parallel mode can also be applied, for example, so the present invention is not limited to a four-wheel drive vehicle.

Claims

1. A control method for a hybrid vehicle, the hybrid vehicle comprising: a first drive source including a first electric generator; a second drive source including a second electric generator; a first clutch for disengaging / engaging the first drive source with drive wheels; and a second clutch for disengaging / engaging the second drive source with drive wheels. While the vehicle is in motion, it can switch between a neutral mode where the first and second drive sources are disconnected from the drive wheels and a parallel mode where the first and second drive sources are connected to the drive wheels. At least one of the following two switching controls is implemented: a first switching control, which, during the switching from the neutral mode to the parallel mode, simultaneously performs synchronous control of the forward and backward rotational speeds of the first clutch based on the control of the first electric generator and synchronous control of the forward and backward rotational speeds of the second clutch based on the control of the second electric generator for at least a portion of the time; and a second switching control, which, during the switching from the parallel mode to the neutral mode, simultaneously performs control that brings the transmitted torque of the first clutch, based on the control of the first electric generator, close to zero and control that brings the transmitted torque of the second clutch, based on the control of the second electric generator, close to zero for at least a portion of the time.

2. The control method for a hybrid vehicle according to claim 1, wherein, When the battery power is above a specified level, two synchronous controls are performed simultaneously for at least a portion of the period; when the battery power is below the specified level, two synchronous controls are performed sequentially.

3. The control method for a hybrid vehicle according to claim 1 or 2, wherein, When two synchronization controls are performed simultaneously for at least a portion of the time, the clutch that completes synchronization first is engaged.

4. The control method for a hybrid vehicle according to claim 3, wherein, When the synchronization of the two synchronous controls is completed simultaneously, the second clutch mentioned above is engaged first.

5. The control method for a hybrid vehicle according to claim 2, wherein, If the battery power is below the specified level and two synchronization controls are performed sequentially, the synchronization control and engagement of the second clutch side mentioned above will be performed first.

6. The control method for a hybrid vehicle according to claim 1, wherein, In the second switching control described above, control that makes the transmitted torque of the first clutch approach zero and control that makes the transmitted torque of the second clutch approach zero are simultaneously initiated.

7. The control method for a hybrid vehicle according to claim 6, wherein, The first clutch and the second clutch described above have a structure with an actuator and a waiting spring mechanism. While initiating control that brings each actuator's transmitted torque close to zero, each actuator performs an action towards the disconnect side.

8. The control method for a hybrid vehicle according to claim 6, wherein, The aforementioned first clutch and second clutch are structures that perform their actions via actuators without a waiting spring mechanism. Disengage the clutch when the transmitted torque is less than the specified torque set for each clutch.

9. The control method for a hybrid vehicle according to claim 8, wherein, If the transmitted torque is simultaneously less than the specified torque of both the first clutch and the second clutch, the first clutch shall be disengaged first.

10. The control method for a hybrid vehicle according to any one of claims 7 to 9, wherein, Hybrid vehicles have a third electric generator that drives the second drive wheel. When the first clutch is disengaged and when the second clutch is disengaged, the torque of the third electric generator is increased in a stepwise manner to offset the torque step difference associated with clutch disengagement.

11. A control device for a hybrid vehicle, the hybrid vehicle comprising: a first drive source including a first electric generator; a second drive source including a second electric generator; a first clutch for disengaging / engaging the first drive source with drive wheels; and a second clutch for disengaging / engaging the second drive source with drive wheels. While the vehicle is in motion, it can switch between a neutral mode where the first and second drive sources are disconnected from the drive wheels and a parallel mode where the first and second drive sources are connected to the drive wheels. At least one of the following two switching controls is implemented: a first switching control, which, during the switching from the neutral mode to the parallel mode, simultaneously performs synchronous control of the forward and backward rotational speeds of the first clutch based on the control of the first electric generator and synchronous control of the forward and backward rotational speeds of the second clutch based on the control of the second electric generator for at least a portion of the time; and a second switching control, which, during the switching from the parallel mode to the neutral mode, simultaneously performs control that brings the transmitted torque of the first clutch, based on the control of the first electric generator, close to zero and control that brings the transmitted torque of the second clutch, based on the control of the second electric generator, close to zero for at least a portion of the time.

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