WO2018189907A1

WO2018189907A1 - Control method and control device for four-wheel drive electric vehicle

Info

Publication number: WO2018189907A1
Application number: PCT/JP2017/015382
Authority: WO
Inventors: 哲庸森田; 通晴郡司; 寛志有田; 祐亮平畠; 啓史郎中村; 博志西田
Original assignee: 日産自動車株式会社
Priority date: 2017-04-14
Filing date: 2017-04-14
Publication date: 2018-10-18
Also published as: JP6725066B2; JPWO2018189907A1

Abstract

The present invention addresses the problem of preventing the occurrence of shocks at the time of a deceleration request in which clutch release control and driving force reduction control overlap, regardless of whether there is pedal switching time and this time is short or long. Provided are a control method and a control device for a four-wheel drive electric vehicle in which a drive source comprises a motor/generator (4), left/right front wheels (10L, 10R) serve as main drive wheels connected to the drive source, and left/right rear wheels (11L, 11R) serve as auxiliary drive wheels connected to the drive source via an electronic control coupling (42). A release command is output to a friction clutch at the time of a deceleration request when in a four-wheel drive state resulting from engagement of the electronic control coupling (42). In this control method for a four-wheel drive hybrid vehicle, driving force reduction control for reducing driving force generated in a driving force transmission system including the regeneration amount by the motor/generator (4) toward a negative driving force range is performed at the time of a deceleration request. At the time of a deceleration request in which driving force reduction control and release control of the electronic control coupling (42) overlap, the negative driving force resulting from the driving force reduction control is limited until the actual clutch capacity of the electronic control coupling (42) falls to zero.

Description

Control method and control apparatus for four-wheel drive electric vehicle

The present disclosure relates to a control method and a control device for a four-wheel drive electric vehicle having a motor / generator as a drive source and a friction clutch in a drive force transmission system to sub drive wheels.

Conventionally, when regenerative control by a motor / generator is intervened in a four-wheel drive state, before starting the regenerative control, a control device for a four-wheel drive electric vehicle that performs cooperative control to make the transmission torque of the electronically controlled coupling zero. It is known (see, for example, Patent Document 1).

International Publication WO 2015/052808 A1 Publication

In the above-described conventional device, even when a brake depression operation is performed, since there is a margin time including a step change time until the regeneration amount in the brake cooperative regeneration increases, the electronic control coupling before the regeneration amount increases. The clutch capacity could be reduced. The electronic control coupling detects the accelerator OFF operation and releases the electronic control coupling.

However, for example, in an electrically powered vehicle with a strong regeneration mode with an increased regeneration amount when the accelerator is OFF and an autonomous driving vehicle in which the changeover time by the control command is shorter than the driver operation, the clutch capacity of the electronically controlled coupling is removed. The amount of regeneration may increase before

The present disclosure has been made paying attention to the above-mentioned problem, and aims to prevent the occurrence of a shock regardless of whether or not there is a changeover time at the time of deceleration request where clutch release control and driving force reduction control overlap. To do.

In order to achieve the above object, the present disclosure has a motor / generator as a drive source, one of the left and right front wheels and the left and right rear wheels is a main drive wheel connected to the drive source, and the other of the left and right front wheels and the left and right rear wheels is The auxiliary drive wheel is connected to the drive source via a friction clutch.
When requesting deceleration in the four-wheel drive state due to the engagement of the friction clutch, a release command is output to the friction clutch.
In this control method for a four-wheel drive electric vehicle, a driving force reduction control is performed to reduce the driving force generated in the driving force transmission system toward the negative driving force region including the regeneration amount by the motor / generator at the time of deceleration request. Do.
At the time of a deceleration request in which the friction clutch release control and the driving force reduction control overlap, the negative driving force by the driving force reduction control is limited until the actual clutch capacity of the friction clutch is released.

In this way, by performing cooperative control that limits the negative driving force by the driving force reduction control until the actual clutch capacity is released, when there is a deceleration request in which the clutch release control and the driving force reduction control overlap, Whether it is long or short, it is possible to prevent the occurrence of shock.

1 is an overall system diagram illustrating an FF-based four-wheel drive hybrid vehicle (an example of a four-wheel drive electric vehicle) to which a control method and a control device according to a first embodiment are applied. It is the schematic which shows the electronically controlled coupling provided in the rear-wheel drive system of the four-wheel drive hybrid vehicle to which the control method and control apparatus of Example 1 were applied. It is a perspective view which shows the cam mechanism of an electronically controlled coupling. FIG. 3 is a block diagram illustrating a configuration of a four-wheel driving force distribution control system in the 4WD control unit according to the first embodiment. 4 is a flowchart illustrating a flow of 4WD control processing executed by the 4WD control unit according to the first embodiment. It is a flowchart which shows the flow of the regeneration control process based on the accelerator opening performed at the time of accelerator release operation by the hybrid control module of Example 1. FIG. It is a coast target driving force map which shows an example of the coast target driving force characteristic with respect to the vehicle speed when the weak regeneration mode is selected and the coast target driving force characteristic with respect to the vehicle speed when the strong regeneration mode is selected. It is a required braking force sharing comparison diagram showing a comparison of the ratios of coast regeneration, brake cooperative regeneration, and mechanical brake when the weak regeneration mode is selected and when the strong regeneration mode is selected. It is explanatory drawing which shows the generation | occurrence | production mechanism of the shock and noise which generate | occur | produce with the cam mechanism of an electronically controlled coupling at the time of brake depression operation after an accelerator release operation. 7 is a time chart showing characteristics of accelerator opening, PWT generation driving force, and clutch capacity of electronic control coupling when electronic control coupling release control and coast regenerative torque control are overlapped by an accelerator release operation in a comparative example. 6 is a time chart showing characteristics of accelerator opening, PWT generation driving force, and clutch capacity of electronic control coupling when release control of electronic control coupling and coast regenerative torque control are overlapped by an accelerator release operation in the first embodiment. It is a flowchart which shows the flow of the regeneration control process based on the target drive force performed at the time of the deceleration request | requirement with the hybrid control module of Example 2. FIG. It is a flowchart which shows the flow of the regeneration control process based on the clutch capacity | capacitance performed at the time of the deceleration request | requirement by the hybrid control module of Example 3. It is a concept block diagram which shows the request | requirement function for implement | achieving cooperative control with clutch release control and driving force fall control, when an application vehicle is a four-wheel drive hybrid vehicle carrying a cruise control system.

Hereinafter, the best mode for realizing the control method and the control device of the four-wheel drive electric vehicle of the present disclosure will be described based on Examples 1 to 3 shown in the drawings.

First, the configuration will be described.
The control method and control device of the first embodiment are applied to an FF-based four-wheel drive hybrid vehicle (an example of a four-wheel drive electric vehicle). Hereinafter, the configuration of the first embodiment will be described by being divided into “entire system configuration”, “detailed configuration of electronic control coupling”, “4WD control processing configuration”, and “regenerative control processing configuration based on accelerator opening”.

[Overall system configuration]
FIG. 1 shows an overall system of an FF-based four-wheel drive hybrid vehicle to which the control method and the control device of the first embodiment are applied. The overall system configuration of the FF-based four-wheel drive hybrid vehicle will be described below with reference to FIG.

As shown in FIG. 1, the front wheel drive system of the FF-based four-wheel drive hybrid vehicle includes a starter motor 1, a horizontally mounted engine 2, a first clutch 3 (abbreviated as “CL1”), and a motor / generator 4 (abbreviated as abbreviation). “MG”), a second clutch 5 (abbreviated as “CL2”), and a belt type continuously variable transmission 6 (abbreviated as “CVT”). The output shaft of the belt type continuously variable transmission 6 is drivingly connected to the left and right

front wheels

10R and 10L via a final reduction gear train 7, a front differential gear 8, and left and right front

wheel drive shafts

9R and 9L.

The starter motor 1 is a cranking motor that has a gear that meshes with an engine start gear provided on a crankshaft of the horizontal engine 2 and that rotates the crankshaft when the engine is started. The starter motor 1 is driven by using a 12V battery 22 as a power source.

The horizontal engine 2 is an engine disposed in the front room with the crankshaft direction as the vehicle width direction, and includes an electric water pump 12 and a crankshaft rotation sensor 13 that detects reverse rotation of the horizontal engine 2.

The first clutch 3 is a normally open dry multi-plate friction clutch that is hydraulically interposed between the horizontally mounted engine 2 and the motor / generator 4, and is fully engaged / slip engaged / released by the first clutch oil pressure. Be controlled.

The motor / generator 4 is a three-phase AC permanent magnet synchronous motor connected to the transverse engine 2 via the first clutch 3. The motor / generator 4 uses a high-power battery 21 described later as a power source, and an inverter 26 that converts direct current into three-phase alternating current during power running and converts three-phase alternating current into direct current during regeneration is connected to the stator coil. Connected through.

The second clutch 5 is a wet-type multi-plate friction clutch by hydraulic operation that is interposed between the motor / generator 4 and the left and right

front wheels

10R, 10L as drive wheels, and is completely engaged / slip by the second clutch hydraulic pressure. The fastening / release is controlled. The second clutch 5 of the first embodiment uses the forward clutch 5a and the reverse brake 5b provided in the forward / reverse switching mechanism of the belt-type continuously variable transmission 6 using planetary gears. That is, during forward travel, the forward clutch 5a is the second clutch 5 (CL2), and during reverse travel, the reverse brake 5b is the second clutch 5 (CL2).

The belt-type continuously variable transmission 6 is a transmission that obtains a continuously variable transmission ratio by changing the belt winding diameter by the transmission hydraulic pressure to the primary oil chamber and the secondary oil chamber. The belt type continuously variable transmission 6 includes a main oil pump 14 (mechanical drive), a sub oil pump 15 (motor drive), and a line pressure PL generated by adjusting pump discharge pressure from the main oil pump 14. And a control valve unit (not shown) that generates the first and second clutch hydraulic pressures and the transmission hydraulic pressure with the pressure as the original pressure. The main oil pump 14 is rotationally driven by a motor shaft (= transmission input shaft) of the motor / generator 4. The sub oil pump 15 is mainly used as an auxiliary pump for producing lubricating cooling oil.

The first clutch 3, the motor / generator 4 and the second clutch 5 constitute a one-motor / two-clutch drive system, and there are “EV mode” and “HEV mode” as main drive modes by this drive system. The “EV mode” is an electric vehicle mode in which the first clutch 3 is disengaged and the second clutch 5 is engaged and only the motor / generator 4 is used as a driving source. Driving in the “EV mode” is referred to as “EV driving”. . The “HEV mode” is a hybrid vehicle mode in which both the clutches 3 and 5 are engaged and the horizontal engine 2 and the motor / generator 4 are used as driving sources, and traveling in the “HEV mode” is referred to as “HEV traveling”.

Note that the regenerative cooperative brake unit 16 in FIG. 1 is a device that controls sharing of the required braking force by the brake cooperative regenerative amount and the mechanical brake when the brake is operated. The regenerative cooperative brake unit 16 includes a brake pedal, a negative pressure booster, a master cylinder, and a brake hydraulic pressure actuator. Then, during the brake operation, cooperative control for the regenerative amount / hydraulic pressure is performed so that the amount obtained by subtracting the regenerative amount from the required braking force based on the pedal operation amount is shared by the hydraulic braking force (mechanical brake).

As shown in FIG. 1, the rear wheel drive system of an FF-based four-wheel drive hybrid vehicle includes a transfer 40, a propeller shaft 41, an electronic control coupling 42, a rear differential gear 43, and left and right rear wheel drive shafts. 44R, 44L and left and right

rear wheels

11R, 11L.

When the electronic control coupling 42 is fastened, the transfer 40 transmits the driving force from the front differential gear 8 to the propeller shaft 41, the electronic control coupling 42, the rear differential gear 43, and the left and right rear wheel drive shafts 44R. , 44L to the left and right

rear wheels

11R, 11L. The detailed configuration of the electronic control coupling 42 will be described later.

As shown in FIG. 1, the power system of the FF-based four-wheel drive hybrid vehicle includes a high-power battery 21 as a motor / generator power source and a 12V battery 22 as a 12V system load power source.

The high-power battery 21 is a secondary battery mounted as a power source for the motor / generator 4. For example, a lithium ion battery in which a cell module constituted by a large number of cells is set in a battery pack case is used. The high-power battery 21 has a built-in junction box in which relay circuits for supplying / cutting off / distributing high-power are integrated, and further includes a cooling fan unit 24 having a battery cooling function, a battery charging capacity (battery SOC) and a battery. And a lithium battery controller 86 for monitoring the temperature.

The high-power battery 21 and the motor / generator 4 are connected via a DC harness 25, an inverter 26, and an AC harness 27. The inverter 26 is provided with a motor controller 83 that performs power running / regenerative control. That is, the inverter 26 converts a direct current from the DC harness 25 into a three-phase alternating current to the AC harness 27 during power running for driving the motor / generator 4 by discharging the high-power battery 21. Further, the three-phase alternating current from the AC harness 27 is converted into a direct current to the DC harness 25 during regeneration in which the high-power battery 21 is charged by power generation by the motor / generator 4.

The 12V battery 22 is a secondary battery mounted as a power source for a 12V load that is an auxiliary machine, and for example, a lead battery mounted in an engine vehicle or the like is used. The high voltage battery 21 and the 12V battery 22 are connected via a DC branch harness 25a, a DC / DC converter 37, and a battery harness 38. The DC / DC converter 37 converts a voltage of several hundred volts from the high-power battery 21 into 12V, and the charge amount of the 12V battery 22 is controlled by controlling the DC / DC converter 37 by the hybrid control module 81. The configuration is to be managed.

As shown in FIG. 1, the control system of the FF hybrid vehicle includes a hybrid control module 81 (abbreviation: “HCM”) as an integrated control means for properly managing the energy consumption of the entire vehicle. Control devices connected to the hybrid control module 81 include an engine control module 82 (abbreviation: “ECM”), a motor controller 83 (abbreviation: “MC”), and a CVT control unit 84 (abbreviation: “CVTCU”). 4WD control unit 85 (abbreviation: “4WDCU”) and lithium battery controller 86 (abbreviation: “LBC”). These control devices including the hybrid control module 81 are connected via a CAN communication line 90 (CAN is an abbreviation of “Controller Area Network”) so that bidirectional information can be exchanged.

Hybrid control module 81 performs various controls based on input information from each control device, regenerative mode selection switch 91, accelerator opening sensor 92, vehicle speed sensor 93, and the like.

The engine control module 82 performs fuel injection control, ignition control, fuel cut control, and the like of the horizontally placed engine 2.

The motor controller 83 performs power running control and regenerative control of the motor generator 4 by the inverter 26.

The CVT control unit 84 performs the engagement hydraulic pressure control of the first clutch 3, the engagement hydraulic pressure control of the second clutch 5, the transmission hydraulic pressure control of the belt type continuously variable transmission 6, and the like.

The lithium battery controller 86 manages the battery SOC, battery temperature, etc. of the high-power battery 21.

4WD control unit 85 inputs signals from 4WD mode switch 94, wheel speed sensor 95, rudder angle sensor 96, yaw rate sensor 97, G sensor 98, brake switch 99, and the like. Then, after performing a predetermined calculation process, a transmission torque command value is output to the electronic control coupling 42. For example, when AUTO is selected by the 4WD mode switch 94, the final command torque is selected by select high among the initial torque process, the differential rotation torque process, and the driving force distribution torque process, and the front wheel 10R is selected. , 10L and the driving force distribution to the

rear wheels

11R, 11L. The driving force distribution ratio to be controlled is a stepless distribution from (100%: 0%, front wheel drive) to (50%: 50%, 4 wheel distribution drive) (front wheel distribution ratio: rear wheel distribution ratio) Is the ratio.

[Detailed configuration of electronically controlled coupling]
FIG. 2 is a schematic view showing the electronic control coupling 42, and FIG. 3 is a perspective view showing a cam mechanism of the electronic control coupling 42. Hereinafter, a detailed configuration of the electronic control coupling 42 will be described with reference to FIGS. 2 and 3.

2 and 3, the electronic control coupling 42 includes a solenoid 45, a coupling input shaft 46, a coupling output shaft 47, a clutch housing 48, an armature 49, a control clutch 50, and a control. A cam 51, a main cam 52, a ball 53, a main clutch 54, and a cam groove 55 are provided.

The coupling input shaft 46 has one end connected to the propeller shaft 41 and the other end fixed to the clutch housing 48. The coupling output shaft 47 is fixed to the input gear of the rear differential gear 43.

The control clutch 50 is a multi-plate friction clutch interposed between the clutch housing 48 and the control cam 51. The main clutch 54 is a multi-plate friction clutch interposed between the clutch housing 48 and the coupling output shaft 47.

As shown in FIG. 3, a cam mechanism is constituted by the control cam 51, the main cam 52, and the balls 53 sandwiched between the

cam grooves

55 and 55 formed in the both

cams

51 and 52.

Here, the fastening operation of the electronic control coupling 42 will be described. First, when a current is passed through the solenoid 45 according to a command from the 4WD control unit 85, a magnetic field is generated around the solenoid 45, and the armature 49 is drawn toward the control clutch 50 side. The friction torque generated by the control clutch 50 is pushed by the attracted armature 49, and the friction torque generated by the control clutch 50 is transmitted to the control cam 51 of the cam mechanism to become a circumferential restraining force. The restraining force due to the torque transmitted to the control cam 51 is amplified and converted into an axial pressing force via the

cam grooves

55 and 55 and the ball 53, and presses the main cam 52 in the front direction. When the main cam 52 pushes the main clutch 54 with an axial pressing force, a frictional engagement torque proportional to the current value is generated in the main clutch 54. The frictional engagement torque generated in the main clutch 54 passes through the coupling output shaft 47 and is transmitted to the rear differential gear 43 as a driving force.

[4WD control processing configuration]
FIG. 4 shows the configuration of the four-wheel driving force distribution control system in the 4WD control unit 85 of the first embodiment. Hereinafter, the configuration of the four-wheel drive force distribution control system will be described with reference to FIG.

As a basic control system of the four-wheel driving force distribution control system, as shown by a solid line block in FIG. 4, an initial torque processing unit B01 based on the vehicle speed, a differential rotation torque processing unit B02 based on front-rear differential rotation, an accelerator opening degree And a driving force distribution torque processing unit B03 based on the driving force. And the final command torque selection part B04 selected by selection high among the torque from each process part B01, B02, B03 is provided. Further, the final command torque decrease change rate limiting unit B06 that limits the decrease change rate of the selected final command torque based on the normal (slow gradient) block B05, and the torque with the reduced change rate limited as the final command torque. And a final command torque block B07.

The regeneration control intervention cooperative control system of the four-wheel drive force distribution control system includes a regeneration control intervention prediction determination block B08, a torque switching block B09, and a control determination time (steep slope) block, as shown by the dotted line block in FIG. B10 and a gradient switching block B11.

The regeneration control intervention prediction determination block B08 inputs the accelerator opening, the vehicle speed, and the solenoid current value, the vehicle speed is in the regenerative vehicle speed region, the accelerator opening is less than the threshold value, and the solenoid energization current is less than the threshold value. When it is not maintained for a certain time or longer, a regeneration control intervention prediction determination signal is output (FIG. 5).

When the torque switching block B09 receives the regeneration control intervention prediction determination signal from the regeneration control intervention prediction determination block B08, the torque switching block B09 sets the torque from the initial torque processing unit B01 to zero (cuts) and the torque from the differential rotation torque processing unit B02. Zero (cut).

When the gradient switching block B11 receives the regeneration control intervention prediction determination signal from the regeneration control intervention prediction determination block B08, the gradient switching block B11 starts from the normal decrease gradient (slow gradient) from the normal time (slow gradient) block B05 to control determination (steep gradient). ) Switch to the decreasing gradient (steep gradient) at the time of control determination from the block B10.

FIG. 5 shows the flow of 4WD control processing executed by the 4WD control unit 85 of the first embodiment. Hereinafter, each step of FIG. 5 will be described.

In step S01, it is determined whether or not the vehicle speed VSP exceeds a lower limit threshold value for regeneration when a deceleration request is made by an accelerator release operation or a brake operation. If YES (vehicle speed VSP> lower threshold), the process proceeds to step S02. If NO (vehicle speed VSP ≦ lower threshold), the process proceeds to step S06.

In step S02, following the determination that vehicle speed VSP> lower limit threshold value in step S01, it is determined whether vehicle speed VSP is less than an upper limit threshold value for regeneration at the time of a deceleration request by an accelerator release operation or a brake operation. If YES (vehicle speed VSP <upper limit threshold), the process proceeds to step S03. If NO (vehicle speed VSP ≧ upper limit threshold), the process proceeds to step S06.

In step S03, following the determination that vehicle speed VSP <the upper limit threshold value in step S02, it is determined whether or not the accelerator opening APO is less than the threshold value. If YES (accelerator opening APO <threshold), the process proceeds to step S04. If NO (accelerator opening APO ≧ threshold), the process proceeds to step S06.

Here, the threshold value of the accelerator opening APO is a threshold for determining the accelerator OFF operation, and originally the accelerator opening APO = 0 (accelerator OFF), but a slight opening value in consideration of sensor noise or the like. Set to

In step S04, following the determination that accelerator opening APO <threshold value in step S03, it is determined whether solenoid energization current <threshold value has not been continued for a predetermined time or more. If YES (solenoid energization current <threshold duration is less than a certain time), the process proceeds to step S05. If N0 (solenoid energization current <threshold continues for a certain time or more), the process proceeds to step S06.

Here, the threshold value of the solenoid energization current is a threshold value for determining that the solenoid energization current is zero, and is originally zero, but is set to a slight current value in consideration of a slight fluctuation of the current or the like. . Further, after the solenoid energization current to the electronic control coupling 42 is set to zero for a certain time, the time required for the frictional engagement torque to become zero after the release operation of the control clutch 50 and the main clutch 54 is completed is experimentally determined. Measured and set based on the measurement result.

In step S05, following the determination that the solenoid energization current <the threshold duration time is less than a predetermined time in step S04, a regeneration control intervention prediction determination signal is output, and based on the output of the regeneration control intervention prediction determination signal, Cut the initial torque control and differential rotation control, and proceed to the end.

Here, when the initial torque control and the differential rotation control are cut, the current decrease gradient to the solenoid 45 of the electronic control coupling 42 is switched from the decrease due to the normal gentle gradient to the decrease due to the steep gradient, and the electronic control coupling 42 is switched. release.

In step S06, initial torque control and differential rotation control are performed in a state where output of the regeneration control intervention prediction determination signal is stopped following determination of NO in any of step S01, step S02, step S03, and step S04. Perform normal control without cutting and proceed to the end.

Here, if the electronic control coupling 42 is released and the process proceeds to step S06, the initial torque control and the differential rotation control are returned to the normal control. Then, the decrease gradient of the solenoid energization current is returned from the decrease due to the steep gradient to the decrease due to the normal gentle gradient.

[Regenerative control processing configuration based on accelerator opening]
FIG. 6 shows the flow of the regenerative control process based on the accelerator opening APO that is executed during the accelerator release operation by the hybrid control module 81 of the first embodiment. Hereinafter, each step of FIG. 6 will be described.

In step S11, it is determined whether or not the strong regeneration mode is selected by the regeneration mode selection switch 91. If YES (selection of strong regeneration mode), the process proceeds to step S12. If NO (selection of weak regeneration mode), the process proceeds to step S15.

Here, “weak regeneration mode” and “strong regeneration mode” will be described. As shown in FIGS. 7 and 8, the “weak regeneration mode” refers to a mode in which the braking force generation region due to the coast regeneration torque by the accelerator release operation is set to a region corresponding to the engine brake. As shown in FIG. 7 and FIG. 8, the “strong regeneration mode” means that the braking force generation region due to the coast regeneration torque by the accelerator release operation is expanded compared to the “weak regeneration mode”, and when the deceleration request by the accelerator release operation is requested, A mode with improved vehicle deceleration control performance. As shown in the map of FIG. 7, each coast target driving force is set according to the vehicle speed VSP. In the “strong regeneration mode”, the maximum negative target in the middle vehicle speed region (for example, about 30 km / h). The driving force is set. Although not shown, in the first embodiment, for example, in a high vehicle speed range of about 90 km / h or more, the “weak regeneration mode” and the “strong regeneration mode” have the same negative target driving force.

When the “weak regeneration mode” is selected, as shown by the arrow A in FIG. 7, when the vehicle is decelerated by the accelerator release operation, the regeneration amount due to the coast regeneration torque gradually decreases. On the other hand, when the “strong regeneration mode” is selected, as shown by the arrow B in FIG. 7, when the vehicle is decelerated by the accelerator release operation, the regeneration amount by the coast regeneration torque increases. That is, the “strong regeneration mode” does not require a brake pedal operation in most deceleration scenes, and can control a braking force by an accelerator return / release operation. For this reason, the “strong regeneration mode” is sometimes referred to as “one pedal mode” in which driving / braking is controlled by accelerator work to the accelerator pedal.

In FIG. 8, “coast regeneration” is a regenerative braking force that is effective when the accelerator is off and the brake is off. “Brake cooperative regeneration” is a regenerative braking force that is applied when the accelerator is off or the brake is on. “Mechanical brake” is a brake hydraulic braking force that is compensated when the braking force cannot be satisfied by the regenerative amount alone when the accelerator is OFF and the brake is ON.

In step S12, following the determination that the strong regeneration mode is selected in step S11, it is determined whether or not the accelerator opening APO is less than the threshold, as in step S03. If YES (accelerator opening APO <threshold), the process proceeds to step S13. If NO (accelerator opening APO ≧ threshold), the process proceeds to step S15.

In step S13, following the determination that accelerator opening APO <the threshold value in step S12 or the predetermined time has not elapsed in step S14, the negative driving force is limited, and the process proceeds to step S14. . Here, limiting the negative driving force means limiting the magnitude of the driving force in the negative direction to a predetermined value or less, and is a direction in which the deceleration force is limited.

Here, “negative driving force limitation” means that the negative driving force generated in the driving system is reached when a predetermined limit value is reached with the increase of the coast regeneration torque by the motor / generator 4 by the selection of the strong regeneration mode. It means to suppress an increase in the amount of regeneration so as to maintain a predetermined limit value.

The “regenerative amount” includes the case of only the coast regeneration amount (coast regeneration torque) by the motor / generator 4 and the case of both the coast regeneration amount and the brake cooperative regeneration amount (brake cooperative regeneration torque).

Also, the “limit value” is set to a negative driving force value at which the vehicle front-rear G change rate due to the increase in the regeneration amount is equal to or less than a predetermined change rate that does not cause the occupant to feel shock or noise. When the tire diameters of the left and right

front wheels

10L, 10R and the left and right

rear wheels

11L, 11R are different, the tire diameter of the front and rear wheels is changed to a value smaller than the limit value when the tire diameter is the same. Is done.

In step S14, following the negative driving force limitation in step S13, it is determined whether or not a predetermined time has elapsed since the negative driving force limitation was started. If YES (predetermined time has elapsed), the process proceeds to step S15. If NO (predetermined time has not elapsed), the process returns to step S13.

Here, the “predetermined time” is based on the release response time of the electronic control coupling 42, and when the clutch release command is output, the time required to reliably enter the clutch release state after the output of the release command (for example, 0.2sec). When a release command is output to the electronic control coupling 42, the time required from the start of output of the release command until the actual clutch capacity is released and the clutch is released is obtained in advance by an experiment or the like.

In step S15, following the selection of the weak regeneration mode in step S11 or the determination that the predetermined time has elapsed in step S14, the process proceeds to the end without limiting the negative driving force including the regeneration amount.

Here, “do not limit negative driving force” means to maintain the restriction release state when shifting from a state where no negative driving force is limited, and shift from a state where negative driving force is limited. When doing, it means releasing the restricted state.

Next, the operation will be described.
The effects of Example 1 are as follows: “Shock and noise generation mechanism during regenerative control intervention”, “Shock and noise generation effect in comparative example”, “Shock and noise suppression effect in Example 1”, “Negative This will be described separately in “characteristic action by driving force limit control”.

[Shock and noise generation mechanism during regenerative control intervention]
FIG. 9 shows a generation mechanism of shock / noise generated by the cam mechanism of the electronically controlled coupling 42 when the brake is depressed after the accelerator release operation. Hereinafter, the shock / abnormal noise generation mechanism during the regeneration control intervention will be described with reference to FIG.

Section (1) is an accelerator-on driving state in which torque is transmitted from the drive source to the drive wheels, and in this section (1), the propeller shaft torque gradually increases. In this section (1), the control cam 51 and the main cam A ball 53 is sandwiched between

cam grooves

55 and 55 formed in 52, and the main clutch 54 is fastened with a small torque transmission (drive).

In the section (2), the accelerator is turned ON → OFF, and then the brake is turned ON to start the generation of regenerative torque. As a result, the propeller shaft torque rapidly increases and decreases rapidly, but the residual torque of the 4WD coupling is in a positive drive state. It is a section. In this section (2), the ball 53 is sandwiched between the

cam grooves

55, 55 formed in the control cam 51 and the main cam 52, and the main clutch 54 is fastened with a large torque transmission (drive).

Section (3) is a section in which the propeller shaft torque decreases to a negative coast state due to an increase in regenerative torque. In this section (3), the main clutch 54 is fastened with a large torque transmission (coast) while the ball 53 is held between the

cam grooves

55 and 55 formed in the control cam 51 and the main cam 52. That is, the coast torque transmission state before the cam reversal is set.

In the section (4), when the propeller shaft torque is in a negative coast state, the regenerative torque is greater than the coupling torque, so that the control cam 51 begins to reverse, and the ball 53 between the

cam grooves

55 and 55 changes from the pinched state to the free state. It is a section. In this section (4), the torque is released at a stretch and becomes in a neutral state, so that a large coast torque suddenly fluctuates toward zero torque, and shock and noise occur due to this fluctuating torque.

As described above, the control cam 51 and the main cam 52 of the electronic control coupling 42 are distorted by the regenerative control intervention to have capacity, and the control cam 51 and the main cam 52 do not move relative to each other while the torque is small. However, when the torque increases and exceeds the capacity due to distortion, the control cam 51 and the main cam 52 suddenly move relative to each other, causing a shock or abnormal noise.

[Shock and noise generation effect in comparative example]
First, it is assumed that control is independently performed without performing cooperative control between transmission torque control to the electronically controlled coupling by the accelerator operation and regenerative torque control by the brake operation. In this case, when the regenerative torque control intervenes, the electronic control coupling has a clutch capacity, so that shock and noise occur as described in the generation mechanism.

Therefore, when regenerative control by the motor / generator intervenes, shock and noise are generated by performing coordinated control in which the transmission torque of the electronic control coupling is set to zero and the clutch capacity is released before starting the regenerative control. Is suppressed. Therefore, a comparative example is one in which cooperative control is performed by removing the clutch capacity of the electronically controlled coupling from the accelerator OFF timing before the start of brake cooperative regeneration based on the brake operation.

In this comparative example, when the “weak regeneration mode” is selected, the PWT generation driving force is almost the accelerator OFF time t2 when the accelerator release operation is started at time t1, as shown by the broken line characteristic C in FIG. Shifts from a positive driving force to a negative driving force at. Then, until the brake ON time t4, a small coast regenerative torque is maintained, and when the brake ON time t4 is passed, the regenerative amount is reduced by the brake cooperative regeneration. In other words, at the clutch release time t6 when the clutch capacity of the electronically controlled coupling is released, the negative driving force does not decrease to the limit value that generates shock and noise. This is because the changeover time from the accelerator OFF time t2 to the brake ON time t4 is long, and this changeover time can be used as an allowance time Δt until the electronic control coupling is released. “PWT” means power train (drive system).

However, when the “strong regeneration mode” is selected, the PWT generation driving force is as follows. When the accelerator release operation is started at time t1 as shown by the solid line characteristic D in FIG. Before reaching time t2, the driving force shifts from a positive driving force to a negative driving force. The coast regeneration torque continues to increase during the period from the accelerator off time t2 to the brake start time t3 to the brake ON time t5. After the brake ON time t5, the coast regeneration decreases with the regeneration amount obtained by adding brake cooperative regeneration to the coast regeneration. . Therefore, the negative driving force reaches the limit value at which the negative driving force generates shock and noise at time t4 before clutch release time t6 when the clutch capacity of the electronically controlled coupling is released. Thereafter, at clutch release time t6, the negative driving force decreases to a level exceeding the limit value for generating shock and abnormal noise. This is because the switching time from the accelerator OFF to the brake ON is substantially eliminated by selecting the “strong regeneration mode”, and the reduction in the regeneration amount cannot be suppressed. Therefore, the electronically controlled coupling greatly varies from drive torque (positive drive force) to coast torque (negative drive force) with clutch capacity, and when the coast torque exceeds the capacity due to cam distortion, two suddenly The cam moves relatively and generates shocks and noise.

[Shock and noise suppression effect in Example 1]
The shock / sound suppression action in the deceleration request scene in which the release control of the electronic control coupling 42 and the regenerative control in which the negative driving force increases in Example 1 will be described with reference to FIGS. 4, 5, and 11.

The 4WD control processing operation executed by the 4WD control unit 85 will be described with reference to FIG. A regenerative vehicle speed condition (lower limit threshold <vehicle speed <upper limit threshold) is satisfied, and an accelerator release condition (accelerator opening APO <threshold) is satisfied. If the solenoid energization current <the threshold duration time is less than a certain time when the accelerator release condition is satisfied, that is, if the electronic control coupling 42 is in the engaged state when the accelerator is OFF, step S01 → It progresses to step S02-> step S03-> step S04-> step S05. In step S05, the initial torque control and the differential rotation control are cut, and the electronic control coupling 42 is released. At this time, the decrease gradient of the solenoid energization current is switched from the decrease due to the normal gentle gradient to the decrease due to the steep gradient.

Then, when the solenoid energization current <the duration of the threshold value is longer than a certain time, that is, when the electronic control coupling 42 is in the released state when the accelerator is OFF, the process proceeds to step S01 → step S02 → step S03 → step S04 → step S06. In step S06, the initial torque control and the differential rotation control are returned to the normal control without being cut.

Next, the regeneration control processing operation in the hybrid control module 81 will be described with reference to FIG. When the “weak regeneration mode” is selected, the process proceeds from step S11 to step S15 to end in the flowchart of FIG. Further, while the accelerator release condition is not satisfied (accelerator opening APO ≧ threshold) when the “strong regeneration mode” is selected, the process proceeds from step S11 to step S12 to step S15 to end in the flowchart of FIG. . In any case, the negative driving force is not limited in step S15.

On the other hand, when the “strong regeneration mode” is selected and the accelerator release condition is satisfied (accelerator opening APO <threshold), the process proceeds from step S11 to step S12 to step S13 in the flowchart of FIG. In step S13, negative driving force limit control is started to suppress the reduction in the regeneration amount to the limit value. Until the predetermined time elapses, in the flowchart of FIG. 6, the flow from step S13 to step S14 is repeated, and the negative driving force limit control that suppresses the reduction in the regeneration amount to the limit value is maintained. The Then, when a predetermined time has elapsed from the start of the negative driving force limit control, the process proceeds from step S14 to step S15 in the flowchart of FIG. 6, and the negative driving force limit is released.

FIG. 11 is a time chart showing each characteristic in the deceleration request scene in which the release control of the electronic control coupling 42 and the regeneration control in which the negative driving force increases in the first embodiment overlap. Hereinafter, the shock / abnormal noise suppressing action in the first embodiment will be described with reference to FIG.

In the case of the first embodiment, when the “strong regeneration mode” is selected, the PWT generation driving force is equal to the coast regeneration torque when the accelerator release operation is started at time t1, as shown by the solid line characteristic E in FIG. Due to the increase, the driving force shifts from a positive driving force to a negative driving force before reaching the accelerator OFF time t2. Then, when the brake start time t3 has elapsed from the accelerator OFF time t2 and the negative driving force reaches the limit value at time t4, after the time t4, a predetermined time from the accelerator OFF time t2 to the time t7 is reached. During this time, the regeneration amount by the coast regeneration and the brake cooperative regeneration is limited so as not to fall below the limit value. Therefore, at the clutch release time t6 (<time t7) at which the clutch capacity of the electronic control coupling 42 is released, the negative driving force is maintained at the limit value, and the occurrence of shock and noise is suppressed.

In other words, by selecting the “strong regeneration mode”, there is substantially no extra time for switching from the accelerator OFF to the brake ON, which can suppress a decrease in negative driving force. However, until the clutch capacity of the electronic control coupling 42 is removed, regeneration control is performed to limit the regeneration amount by coast regeneration and brake cooperative regeneration so as not to fall below the limit value of the negative driving force. It is.

[Characteristic action by negative driving force limit control]
In the first embodiment, the driving force reduction control is performed to reduce the driving force generated in the driving force transmission system toward the negative driving force region including the amount of regeneration by the motor / generator 4 when the deceleration is requested. At the time of deceleration request in which the release control of the electronic control coupling 42 and the driving force reduction control overlap, the negative driving force by the driving force reduction control is limited until the actual clutch capacity of the electronic control coupling 42 is released.

That is, at the time of deceleration request, before the actual clutch capacity of the electronic control coupling 42 is released, the negative driving force is increased by the driving force reduction control, and the electronic control coupling 42 shifts from positive torque to neutral state to negative torque. Then, it was found that a shock occurred.
Accordingly, paying attention to the driving force reduction control side that is not affected by the release response of the electronic control coupling 42, the cooperative control that limits the negative driving force by the driving force reduction control until the actual clutch capacity of the electronic control coupling 42 is released. To do.
Therefore, when a deceleration request in which the clutch release control and the driving force reduction control overlap with each other, the occurrence of a shock is prevented regardless of the presence / absence of the changeover time and the length.

In the first embodiment, when limiting the negative driving force by the driving force reduction control, when the predetermined limit value is reached due to the increase of the regeneration amount by the motor / generator 4, the regeneration amount is maintained so as to be maintained at the predetermined limit value. Suppresses the increase of

For example, the deceleration request includes an accelerator release operation and an operation of switching from accelerator release to brake depression. In any case, if the accelerator release operation is performed, a negative driving force is generated due to an increase in the regeneration amount by the motor / generator 4. Becomes larger. Moreover, the amount of regeneration during the accelerator release operation has increased due to recent fuel efficiency requirements. Therefore, when limiting the negative driving force, pay attention to the regeneration amount by the motor / generator 4 having better control response and higher control accuracy than the brake fluid pressure in the mechanical brake, and suppress the increase in the regeneration amount. did.
Therefore, when the negative driving force is limited, the negative driving force is limited to the limit value by regenerative amount control that provides good control response and high control accuracy.

In the first embodiment, the friction clutch is a ball cam type electronically controlled coupling 42, and the limit value of the regenerative amount is a negative driving force value at which the vehicle front-rear G change rate due to the increase of the regenerative amount is equal to or less than a predetermined change rate. Set.

In other words, in the case of the ball cam type electronically controlled coupling 42, if a large negative driving force is generated until release, not only a shock is generated, but also an abnormal noise due to a striking sound when the ball 53 collides with the cam groove 55 is generated. appear.
Therefore, the occurrence of shock and abnormal noise is prevented at the time of deceleration request in which the release control of the electronic control coupling 42 and the driving force reduction control overlap.

In Example 1, when the tire diameters of the front and rear wheels are different from each other, the limit value of the regeneration amount is changed to a value smaller than the limit value when the tire diameters of the front and rear wheels are the same diameter according to the difference in tire diameters. To do.

That is, when a tire with a different diameter is worn, the load applied before and after the cam of the electronically controlled coupling 42 changes, and the larger the difference in the diameter of the tire, the greater the noise generated by the impact hitting sound. Therefore, when different diameter tires are worn on the front and rear wheels, the generation of abnormal noise can be suppressed regardless of the difference in tire diameters.

In the first embodiment, at the time of the accelerator release operation in which the release control of the electronic control coupling 42 and the regeneration control in the strong regeneration mode overlap, the accelerator opening APO becomes equal to or less than the threshold value, and then based on the release response time of the electronic control coupling 42. The negative driving force is limited by suppressing an increase in the regeneration amount until a predetermined time set in the above elapses.

That is, in the strong regeneration mode, the coast line of the target driving force has fallen, so even if a release command is issued to the electronic control coupling 42, the clutch capacity cannot be released in time, and the regeneration amount increases before the clutch capacity is released. End up.
Therefore, during the accelerator release operation in which the release control of the electronic control coupling 42 and the regeneration control in the strong regeneration mode overlap, the occurrence of shock due to the increase in the regeneration amount before the clutch capacity of the electronic control coupling 42 is released is prevented. The

Next, the effect will be described.
In the control method and control device for the four-wheel drive hybrid vehicle of the first embodiment, the effects listed below can be obtained.

(1) Having a motor / generator 4 as a drive source, the left and right

front wheels

10L, 10R as main drive wheels connected to the drive source, and the left and right

rear wheels

11L, 11R as a drive source, a friction clutch (electronic control coupling 42) It is set as the sub drive wheel connected via.
At the time of deceleration request in the four-wheel drive state by engagement of the friction clutch (electronic control coupling 42), a release command is output to the friction clutch.
In the control method of this four-wheel drive electric vehicle (four-wheel drive hybrid vehicle), when the deceleration is requested, the drive force generated in the drive force transmission system is directed toward the negative drive force region including the regeneration amount by the motor / generator 4. To reduce the driving force.
At the time of deceleration request where the release control of the friction clutch (electronic control coupling 42) and the driving force reduction control overlap, the negative driving force by the driving force reduction control is reduced until the actual clutch capacity of the friction clutch (electronic control coupling 42) is released. Limit (FIG. 11).
For this reason, there is provided a control method for a four-wheel drive electric vehicle (four-wheel drive hybrid vehicle) that prevents the occurrence of a shock regardless of whether or not there is a stepping time when the clutch release control and the driving force reduction control overlap. Can be provided.

(2) The regeneration amount by the motor / generator 4 includes the case of only the coast regeneration amount and the case of both the coast regeneration amount and the brake cooperative regeneration amount.
When the negative driving force by the driving force reduction control is limited, if the predetermined limit value is reached due to the increase in the regeneration amount by the motor / generator 4, the increase in the regeneration amount is suppressed so that the predetermined limit value is maintained. (FIG. 11).
For this reason, in addition to the effect of (1), when limiting the negative driving force, it is possible to limit the negative driving force to the limit value by regenerative amount control that provides good control response and high control accuracy. it can.

(3) The friction clutch is a ball cam type electronically controlled coupling 42.
The limit value of the regeneration amount is set to a negative driving force value at which the vehicle front-rear G change rate due to the increase of the regeneration amount is equal to or less than a predetermined change rate (FIG. 11).
For this reason, in addition to the effect of (2), it is possible to prevent the occurrence of shock and abnormal noise at the time of deceleration request in which the release control of the electronic control coupling 42 and the driving force reduction control overlap.

(4) When the tire diameter of the front and rear wheels is different, the limit value of the regeneration amount is changed to a value smaller than the limit value when the tire diameter of the front and rear wheels is the same diameter according to the difference in tire diameter ( FIG. 11).
For this reason, in addition to the effect of (3), when different diameter tires are worn on the front and rear wheels, the occurrence of abnormal noise can be suppressed regardless of the difference in tire diameter difference.

(5) At the time of accelerator release operation in the four-wheel drive state by engagement of the friction clutch (electronic control coupling 42), if the accelerator opening APO becomes less than the threshold value, a release command is output to the friction clutch (electronic control coupling 42) 4 wheel drive control is performed.
At the time of accelerator release operation, regeneration control is performed in a strong regeneration mode in which the coast regeneration torque generated by the motor / generator 4 is larger than the engine brake equivalent.
At the time of accelerator release operation in which the release control of the friction clutch (electronic control coupling 42) and the regeneration control in the strong regeneration mode overlap, the release response of the friction clutch (electronic control coupling 42) after the accelerator opening APO falls below the threshold value. The negative driving force is limited by suppressing an increase in the regenerative amount until a predetermined time set in advance based on the time in an experiment or the like has elapsed (FIG. 6).
For this reason, in addition to the effects (1) to (4), the friction clutch (electronic control coupling 42) is used during the accelerator release operation, in which the release control of the friction clutch (electronic control coupling 42) and the regeneration control in the strong regeneration mode overlap. It is possible to prevent the occurrence of shock due to the increase in the regeneration amount before the clutch capacity of the clutch is released.

(6) Having a motor / generator 4 as a drive source, the left and right

front wheels

10L and 10R as main drive wheels connected to the drive source, and the left and right

rear wheels

11L and 11R as a drive source, a friction clutch (electronic control coupling 42) It is set as the sub drive wheel connected via.
A 4WD controller (4WD control unit 85) is provided that outputs a release command to the friction clutch when a deceleration request is made in the four-wheel drive state by engagement of the friction clutch (electronic control coupling 42).
In the control device for this four-wheel drive electric vehicle (four-wheel drive hybrid vehicle), when the deceleration is requested, the drive force generated in the drive force transmission system is directed toward the negative drive force region including the regeneration amount by the motor / generator 4. A driving force controller (hybrid control module 81) for performing driving force lowering control is provided.
The driving force controller (hybrid control module 81) is configured to request the deceleration of the friction clutch (electronic control coupling 42) release control and the driving force reduction control until the actual clutch capacity of the friction clutch (electronic control coupling 42) is released. Then, the negative driving force by the driving force reduction control is limited (FIG. 11).
For this reason, a control device for a four-wheel drive electric vehicle (four-wheel drive hybrid vehicle) that prevents the occurrence of a shock regardless of whether or not there is a changeover time when the clutch release control and the driving force reduction control are overlapped. Can be provided.

Example 2 is an example in which the control based on the target driving force is used in place of the control based on the accelerator opening in Example 1 as the 4WD control for controlling the clutch capacity of the electronically controlled coupling.

First, the configuration will be described.
In addition, since “the whole system configuration” and “the detailed configuration of the electronic control coupling” are the same as those in the first embodiment, illustration and description thereof are omitted. Hereinafter, “4WD control processing configuration and regenerative control processing configuration based on target driving force” will be described.

[4WD control processing configuration and regenerative control processing configuration based on target driving force]
For the 4WD control processing configuration, the determination as to whether or not the accelerator opening in step S03 in FIG. 5 in the first embodiment <the threshold value is replaced with a determination as to whether or not the target driving force is equal to or less than a predetermined value. And That is, in the 4WD control, the target driving force (negative driving force value) at the time of the accelerator release operation is set to a predetermined value, and the electronic control coupling 42 is controlled to be released when the target driving force becomes a predetermined value or less.

FIG. 12 shows the flow of the regenerative control process based on the target driving force executed during the accelerator release operation by the hybrid control module 81 of the second embodiment. Hereinafter, each step of FIG. 12 will be described.

In step S21, it is determined whether or not the strong regeneration mode is selected by the regeneration mode selection switch 91. If YES (selection of strong regeneration mode), the process proceeds to step S22. If NO (selection of weak regeneration mode), the process proceeds to step S25.

In Step S22, following the determination that the strong regeneration mode is selected in Step S21, it is determined whether or not the target driving force is equal to or less than a predetermined value. If YES (target driving force ≦ predetermined value), the process proceeds to step S23. If NO (target driving force> predetermined value), the process proceeds to step S25.

Here, based on the accelerator opening APO, the vehicle speed VSP, and the target driving force map, the target driving force is set to drive power running torque when the accelerator opening is in the middle and high opening range, and coasting when the accelerator opening is in the low opening region. Set to regenerative torque. The predetermined value of the target driving force is set as a threshold value for determining that the coast regeneration torque (negative driving force) due to the accelerator OFF operation is being generated.

In step S23, following the determination in step S22 that the target driving force ≦ predetermined value or the determination in step S24 that the predetermined time has not elapsed, the negative driving force is limited, and the process proceeds to step S24. .

In step S24, following the negative driving force limitation in step S23, it is determined whether or not a predetermined time has elapsed since the negative driving force limitation was started. If YES (predetermined time has elapsed), the process proceeds to step S25. If NO (predetermined time has not elapsed), the process returns to step S23.

In step S25, following the selection of the weak regeneration mode in step S21 or the determination that the predetermined time has elapsed in step S24, the process proceeds to the end without limiting the negative driving force including the regeneration amount.

Next, the operation will be described.
Since “shock / noise generation mechanism during regenerative control intervention” and “shock / noise generation action in the comparative example” are the same as those in the first embodiment, description thereof is omitted. Hereinafter, the “shock / abnormal noise suppressing action in the second embodiment” will be described.

[Shock and noise suppression effect in Example 2]
The shock / sound suppressing action in the deceleration request scene in which the release control of the electronic control coupling 42 and the regenerative control in which the negative driving force increases in the second embodiment will be described.

First, the regenerative control processing operation in the hybrid control module 81 will be described with reference to FIG. When the “weak regeneration mode” is selected, the process proceeds from step S21 to step S25 to the end in the flowchart of FIG. Further, while the target driving force condition is not satisfied (target driving force> predetermined value) when the “strong regeneration mode” is selected, step S21 → step S22 → step S25 → end in the flowchart of FIG. move on. In any case, the negative driving force is not limited in step S25.

On the other hand, when the “strong regeneration mode” is selected and the target driving force condition is satisfied (target driving force ≦ predetermined value), the process proceeds from step S21 to step S22 to step S23 in the flowchart of FIG. In step S23, negative driving force limit control is started to suppress the reduction in the regeneration amount to the limit value. Then, until the predetermined time elapses, the flow from step S23 to step S24 is repeated in the flowchart of FIG. 12, and negative driving force limit control that suppresses the reduction in the regeneration amount to the limit value is maintained. The Then, when a predetermined time has elapsed from the start of the negative driving force limit control, the process proceeds from step S24 to step S25 in the flowchart of FIG. 12, and the negative driving force limit is released.

Therefore, similarly to FIG. 11 in the first embodiment, the regeneration amount by coast regeneration and brake cooperative regeneration is limited so as not to fall below the limit value for a predetermined time after the target driving force becomes equal to or less than the predetermined value. The Therefore, when the clutch is released to release the clutch capacity of the electronic control coupling 42, the negative driving force is maintained at the limit value, and the occurrence of shock and noise is suppressed.

Next, the effect will be described.
In addition to the effects (1) to (4) and (6) of the first embodiment, the following effects are obtained in the control method and control device for the four-wheel drive hybrid vehicle in the second embodiment.

(7) Release control of the friction clutch (electronic control coupling 42) is performed according to the target driving force set based on the accelerator opening APO and the vehicle speed VSP.
Based on the release response time of the friction clutch (electronic control coupling 42) after the target drive force becomes a predetermined value or less at the time of deceleration request when the release control of the friction clutch (electronic control coupling 42) and the driving force reduction control overlap. Until the set time elapses, the negative driving force by the driving force reduction control is limited (FIG. 12).
For this reason, the target driving force decreases before the clutch capacity of the friction clutch (electronic control coupling 42) is released at the time of deceleration request where the release control of the friction clutch (electronic control coupling 42) and the driving force reduction control overlap. It is possible to prevent the occurrence of shock due to.

Example 3 is an example in which an estimated clutch capacity (actual clutch capacity) is calculated in the case of 4WD control for controlling the clutch capacity of the electronically controlled coupling.

[4WD control processing configuration and regenerative control processing configuration based on target driving force]
With regard to the 4WD control processing configuration, the control to release the electronic control coupling 42 is performed based on the determination that the accelerator opening degree of the first embodiment <the threshold value or the determination that the target driving force ≦ the predetermined value in the second embodiment. Then, during release control of the electronic control coupling 42, an estimated clutch capacity value (actual clutch capacity) is calculated, and feedback control is performed based on a deviation from the target clutch capacity, for example.

FIG. 13 shows the flow of the regenerative control process based on the target driving force executed during the accelerator release operation by the hybrid control module 81 of the third embodiment. Hereinafter, each step of FIG. 13 will be described.

In step S31, it is determined whether or not the strong regeneration mode is selected by the regeneration mode selection switch 91. If YES (selection of strong regeneration mode), the process proceeds to step S32. If NO (selection of weak regeneration mode), the process proceeds to step S34.

In step S32, following the determination that the strong regeneration mode is selected in step S31, it is determined whether or not the estimated clutch capacity is greater than or equal to a predetermined value. If YES (clutch capacity estimated value ≧ predetermined value), the process proceeds to step S33. If NO (clutch capacity estimated value <predetermined value), the process proceeds to step S34.

Here, the predetermined value of the estimated clutch capacity is set as a threshold value for determining that the electronic control coupling 42 is in the released state with the clutch capacity removed.

In step S33, following the determination that clutch estimated value ≧ predetermined value in step S32, the negative driving force is limited and the process proceeds to the end. That is, when the process proceeds from step S32 to step S33, the negative driving force is limited based on the determination that the clutch capacity of the electronic control coupling 42 is not released.

In step S34, following the determination that the weak regeneration mode is selected in step S31, or the determination that the clutch capacity estimation value is smaller than the predetermined value in step S32, the process is ended without limiting the negative driving force. Proceed to That is, when the process proceeds from step S32 to step S34, the limitation on the negative driving force is released based on the determination that the clutch capacity of the electronic control coupling 42 is removed and the clutch is released.

Next, the operation will be described.
Since “shock / noise generation mechanism during regenerative control intervention” and “shock / noise generation action in the comparative example” are the same as those in the first embodiment, description thereof is omitted. Hereinafter, the “shock / abnormal noise suppressing action in the third embodiment” will be described.

[Shock and noise suppression effect in Example 3]
A shock / sound suppression operation in a deceleration request scene in which the release control of the electronic control coupling 42 and the regenerative control in which the negative driving force increases in the third embodiment will be described.

First, the regenerative control processing operation in the hybrid control module 81 will be described with reference to FIG. When the “weak regeneration mode” is selected, the process proceeds from step S31 to step S34 to end in the flowchart of FIG. Further, when the “strong regeneration mode” is selected but the clutch engagement condition is not satisfied (clutch capacity estimation value ≧ predetermined value), step S31 → step S32 → step S34 → end in the flowchart of FIG. move on. In either case, the negative driving force is not limited in step S34.

On the other hand, while the “strong regeneration mode” is selected and the clutch engagement condition is satisfied (clutch capacity estimation value ≧ predetermined value), step S31 → step S32 → step S33 → end in the flowchart of FIG. Proceed to In step S33, negative driving force limit control is performed to suppress the reduction in the regeneration amount to the limit value.

Therefore, while the clutch engagement condition is satisfied (clutch capacity estimation value ≧ predetermined value), the regeneration amount by coast regeneration and brake cooperative regeneration is limited so as not to fall below the limit value. When the clutch engagement condition is not satisfied (clutch capacity estimation value <predetermined value), that is, when the electronic control coupling 42 is in the released state, the negative driving force restriction control is released. Therefore, until it is confirmed that the clutch capacity of the electronic control coupling 42 has been released, the negative driving force is maintained at the limit value, and the occurrence of shock and noise is suppressed.

Next, the effect will be described.
In addition to the effects (1) to (4) and (6) of the first embodiment, the following effects are obtained in the control method and control apparatus for a four-wheel drive hybrid vehicle in the third embodiment.

(8) Release control of the friction clutch (electronic control coupling 42) is performed while calculating an estimated clutch capacity value of the friction clutch (electronic control coupling 42). At the time of a deceleration request in which the release control of the friction clutch (electronic control coupling 42) and the driving force reduction control overlap, the negative driving force by the driving force reduction control is limited while the estimated clutch capacity is equal to or greater than a predetermined value (FIG. 13). .
For this reason, the negative driving force decreases before the actual clutch capacity of the friction clutch (electronic control coupling 42) is released at the time of deceleration request where the release control of the friction clutch (electronic control coupling 42) and the driving force reduction control overlap. It is possible to prevent the occurrence of a shock caused by doing.

The control method and control device for the four-wheel drive electric vehicle of the present disclosure have been described based on the first to third embodiments. However, the specific configuration is not limited to these embodiments, and design changes and additions are allowed without departing from the spirit of the invention according to each claim of the claims.

In Examples 1 to 3, examples of the pedal operation by the driver such as an accelerator release operation or a change-over operation from the accelerator release to the brake depression are shown as the deceleration request. However, the deceleration request includes a case of a cruise control system-equipped vehicle or an automatically driven vehicle that outputs a deceleration request corresponding to accelerator release or stepping as a control command for the required regenerative torque.

For example, when the applicable vehicle is a four-wheel drive hybrid vehicle equipped with a cruise control system, the function shown in the concept block diagram of FIG. 14 is given to the hybrid control module (HCM) and the vehicle behavior controller (VDC). That is, FIG. 14 shows a request function for realizing cooperative control of clutch release control and driving force reduction control for the hybrid control module (HCM) and the vehicle behavior controller (VDC). In FIG. 14, “ACEP” indicates “strong regeneration mode”, and “Norma” indicates “weak regeneration mode”.

In the first to third embodiments, the ball cam type electronically controlled coupling 42 having the control clutch 50, the cam mechanism, and the main clutch 54 is used as the friction clutch. However, the friction clutch is not limited to the ball cam type electronically controlled coupling, and any friction clutch that controls the front / rear wheel driving force distribution by an external command can be used, such as a multi-plate clutch operated by the control hydraulic pressure. As an example.

Embodiments 1 to 3 show examples in which the control device of the present disclosure is applied to an FF-based four-wheel drive hybrid vehicle. However, the control device of the present disclosure can be applied not only to an FF-based four-wheel drive hybrid vehicle but also to an FR-based four-wheel drive hybrid vehicle. Furthermore, the present invention can be applied not only to a four-wheel drive hybrid vehicle but also to a four-wheel drive electric vehicle. In short, a four-wheel drive electric vehicle having a motor / generator as a drive source and a friction clutch for controlling the front and rear wheel drive force distribution by an external command in the drive force transmission path from the drive source to the sub drive wheels. If applicable.

Claims

A motor / generator is used as the drive source, and one of the left and right front wheels and the left and right rear wheels is a main drive wheel connected to the drive source, and the other of the left and right front wheels and the left and right rear wheels is connected to the drive source via a friction clutch. As a secondary drive wheel
In a control method of a four-wheel drive electric vehicle that outputs a release command to the friction clutch when requesting deceleration in a four-wheel drive state by engagement of the friction clutch,
At the time of deceleration request, drive force reduction control is performed to reduce the drive force generated in the drive force transmission system toward the negative drive force region including the regeneration amount by the motor / generator,
A four-wheel drive characterized by limiting the negative driving force by the driving force reduction control until the actual clutch capacity of the friction clutch is released at the time of deceleration request where the release control of the friction clutch and the driving force reduction control overlap. Control method of electric vehicle.
In the control method of the four-wheel drive electric vehicle according to claim 1,
The regeneration amount by the motor / generator includes the case of only the coast regeneration amount and the case of both the coast regeneration amount and the brake cooperative regeneration amount,
When limiting the negative driving force by the driving force reduction control, when the predetermined limit value is reached due to the increase in the regeneration amount by the motor / generator, the regeneration amount is increased so as to maintain the predetermined limit value. A control method for a four-wheel drive electric vehicle.
In the control method of the four-wheel drive electric vehicle according to claim 2,
The friction clutch is a ball cam type electronically controlled coupling,
The limit value of the regeneration amount is set to a negative driving force value at which the vehicle front-rear G change rate due to the increase of the regeneration amount is equal to or less than a predetermined change rate.
In the control method of the four-wheel drive electric vehicle according to claim 3,
The regenerative amount limit value is changed to a value smaller than the limit value when the front and rear wheel tire diameters are the same, depending on the difference in tire diameter when the front and rear wheel tire diameters are different. A control method for a four-wheel drive electric vehicle.
In the control method of the four-wheel drive electric vehicle according to any one of claims 1 to 4,
At the time of accelerator release operation in the four-wheel drive state by engagement of the friction clutch, four-wheel drive control is performed to output a release command to the friction clutch when the accelerator opening is below a threshold value,
At the time of accelerator release operation, regenerative control is performed in the strong regenerative mode in which the coast regenerative torque generated by the motor / generator is expanded more than the engine brake equivalent,
During the accelerator release operation in which the friction clutch release control and the regeneration control in the strong regeneration mode overlap, a predetermined time set based on the friction clutch release response time elapses after the accelerator opening becomes equal to or less than a threshold value. Until then, the negative driving force is limited by suppressing the increase in the regeneration amount. A method for controlling a four-wheel drive electric vehicle.
In the control method of the four-wheel drive electric vehicle according to any one of claims 1 to 4,
The friction clutch release control is performed according to a target driving force set based on the accelerator opening and the vehicle speed,
At the time of a deceleration request in which the friction clutch release control and the driving force reduction control overlap each other, until the set time set based on the friction clutch release response time elapses after the target driving force becomes a predetermined value or less. The negative driving force by the driving force reduction control is limited. A control method for a four-wheel drive electric vehicle.
In the control method of the four-wheel drive electric vehicle according to any one of claims 1 to 4,
Performing the release control of the friction clutch while calculating the estimated clutch capacity of the friction clutch;
The four-wheel drive is characterized in that, when the deceleration request for overlapping the friction clutch release control and the driving force reduction control overlaps, the negative driving force by the driving force reduction control is limited while the estimated clutch capacity is not less than a predetermined value. A method for controlling a drive electric vehicle.
A motor / generator is provided as the drive source, and one of the left and right front wheels and the left and right rear wheels is connected to the drive source, and the other of the left and right front wheels and the left and right rear wheels is connected to the drive source via a friction clutch. In a control device for a four-wheel drive electric vehicle comprising:
An accelerator position detector for detecting or estimating the accelerator position;
A vehicle speed detection device for detecting or estimating the vehicle speed;
A 4WD controller that outputs a release command to the friction clutch when the accelerator is depressed to a release state in the four-wheel drive state by the engagement of the friction clutch;
Provided with a driving force controller that generates a negative driving force set according to the vehicle speed in the motor / generator when the accelerator is depressed to a released state;
The driving force controller limits the negative driving force to a predetermined value or less for a predetermined time when the accelerator is depressed and released in a four-wheel drive state in which the friction clutch is engaged. A control device for a four-wheel drive electric vehicle.