JP6725066B2 - Control method and control device for four-wheel drive electric vehicle - Google Patents

Description

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 an auxiliary drive wheel.

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

International Publication WO 2015/052808 A1 Publication

In the above conventional device, even when the brake depression operation is performed, there is a margin time including the pedal change time until the regeneration amount in the brake cooperative regeneration increases, so that the electronically controlled coupling before the regeneration amount increases The clutch capacity could be reduced. Note that the electronically controlled coupling releases the electronically controlled coupling by detecting an accelerator OFF operation.

However, for example, in an electric vehicle equipped with a strong regeneration mode in which the amount of regeneration with the accelerator off is expanded, or in an automatic driving vehicle in which the stepping time by a control command is shorter than driver operation, the clutch capacity of the electronically controlled coupling is removed. The regenerative capacity may increase before

The present disclosure was made in view of the above problems, and an object thereof is to prevent the occurrence of a shock at the time of a deceleration request in which the clutch release control and the driving force reduction control overlap, regardless of the presence or absence or the length of the stepping time. To do.

To achieve the above object, the present disclosure has a motor/generator as a 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 used. The auxiliary drive wheel is connected to the drive source via a friction clutch.
When a deceleration request is made in the four-wheel drive state by engaging the friction clutch, a release command is output to the friction clutch.
In this control method for a four-wheel drive electric vehicle, when a deceleration request is made, a driving force reduction control is performed in which the driving force generated in the driving force transmission system is reduced toward the negative driving force region including the amount of regeneration by the motor/generator. To do.
When the friction clutch disengagement control and the driving force reduction control overlap, the negative driving force is limited by the driving force reduction control until the actual clutch capacity of the friction clutch is exhausted.

In this way, by performing the cooperative control that limits the negative driving force by the driving force reduction control until the actual clutch capacity is exhausted, when there is a deceleration request in which the clutch release control and the driving force reduction control overlap, whether or not there is a stepping time, It is possible to prevent a shock from occurring regardless of the length.

FIG. 1 is an overall system diagram showing an FF-based four-wheel drive hybrid vehicle (an example of a four-wheel drive electric vehicle) to which the control method and control device of the first embodiment are applied. FIG. 3 is a schematic diagram showing an electronically controlled coupling provided in a rear wheel drive system of a four-wheel drive hybrid vehicle to which the control method and control device of the first embodiment is applied. It is a perspective view which shows the cam mechanism of an electronically controlled coupling. FIG. 3 is a block diagram showing a configuration of a four-wheel drive force distribution control system in the 4WD control unit of the first embodiment. 5 is a flowchart showing a flow of 4WD control processing executed by the 4WD control unit of the first embodiment. 5 is a flowchart showing a flow of a regeneration control process based on an accelerator opening degree, which is executed at the accelerator release operation in the hybrid control module of the first embodiment. 6 is a coast target driving force map showing an example of a coast target driving force characteristic with respect to a vehicle speed when a weak regeneration mode is selected and a coast target driving force characteristic with respect to a vehicle speed when a strong regeneration mode is selected. FIG. 6 is a required braking force sharing comparison diagram showing a comparison of the sharing ratios of coast regeneration/brake cooperative regeneration/mechanical braking 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 the abnormal noise which generate|occur|produce with the cam mechanism of an electronically controlled coupling at the time of the brake depression operation after accelerator release operation. 8 is a time chart showing each characteristic of accelerator opening, PWT generated driving force, and clutch capacity of electronically controlled coupling when electronically controlled coupling release control and coast regenerative torque control are overlapped by accelerator release operation in a comparative example. 5 is a time chart showing each characteristic of an accelerator opening degree, a PWT generated driving force, and a clutch capacity of an electronically controlled coupling when electronically controlled coupling release control and coast regenerative torque control are overlapped by an accelerator release operation in the first embodiment. 9 is a flowchart showing a flow of a regenerative control process based on a target driving force executed when a deceleration request is made in the hybrid control module of the second embodiment. 9 is a flowchart showing a flow of a regeneration control process based on a clutch capacity executed when a deceleration request is made by the hybrid control module of the third embodiment. FIG. 11 is a conceptual block diagram showing required functions for realizing cooperative control of clutch release control and driving force reduction control when the applied vehicle is a four-wheel drive hybrid vehicle equipped with a cruise control system.

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

First, the configuration will be described.
The control method and the control device according to 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 an "overall system configuration", a "electronic control coupling detailed configuration", a "4WD control processing configuration", and an "accelerator opening-based regenerative control processing configuration".

[Overall system configuration]
FIG. 1 shows an overall system of a FF-based four-wheel drive hybrid vehicle to which the control method and control device of the first embodiment is 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, a front wheel drive system of an FF-based four-wheel drive hybrid vehicle includes a starter motor 1, a horizontal engine 2, a first clutch 3 (abbreviation “CL1”), and a motor/generator 4 (abbreviation). “MG”), a second clutch 5 (abbreviation “CL2”), and a belt type continuously variable transmission 6 (abbreviation “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 starting gear provided on the crankshaft of the horizontal engine 2 and that rotationally drives the crankshaft when the engine is started. The starter motor 1 is driven by the 12V battery 22 as a power source.

The horizontal engine 2 is an engine arranged in the front room with the crankshaft direction being the vehicle width direction, and has 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 which is interposed between the horizontal engine 2 and the motor/generator 4, and is a normally open dry multi-disc friction clutch, which is completely engaged/slip engaged/released by the first clutch hydraulic pressure. Controlled.

The motor/generator 4 is a three-phase AC permanent magnet synchronous motor that is connected to the horizontal engine 2 via the first clutch 3. This motor/generator 4 uses a high-voltage battery 21 described later as a power source, and an inverter 26 that converts direct current to three-phase alternating current during power running and three-phase alternating current to direct current during regeneration is provided in the stator coil with an AC harness 27. Connected through.

The second clutch 5 is a hydraulically actuated multi-plate friction clutch interposed between the motor/generator 4 and the left and right front wheels 10R and 10L that are drive wheels, and is completely engaged/slipped by the second clutch hydraulic pressure. Fastening/releasing 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 a planetary gear. In other words, the forward clutch 5a is the second clutch 5 (CL2) when traveling forward, and the reverse brake 5b is the second clutch 5 (CL2) when traveling backward.

The belt type continuously variable transmission 6 is a transmission that obtains a stepless gear ratio by changing the winding diameter of the belt by changing the 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) for generating the first and second clutch hydraulic pressures and the shift hydraulic pressure with the above as a source pressure. The main oil pump 14 is rotationally driven by the motor shaft of the motor/generator 4 (=transmission input shaft). The sub oil pump 15 is mainly used as an auxiliary pump that produces 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 the main drive modes of this drive system are "EV mode" and "HEV mode". The "EV mode" is an electric vehicle mode in which the first clutch 3 is disengaged, the second clutch 5 is engaged, and only the motor/generator 4 is used as a drive source, and traveling in the "EV mode" is referred to as "EV traveling". .. 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 drive sources, and traveling in the "HEV mode" is called "HEV traveling".

The regenerative cooperative braking unit 16 in FIG. 1 is a device that controls the sharing of the required braking force by the brake cooperative regenerative amount and the mechanical brake amount 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 actuator. Then, when the brake is operated, a cooperative control of the regenerative amount/the hydraulic pressure is performed such 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 and 44L and left and right rear wheels 11R and 11L are provided.

When the electronic control coupling 42 is fastened, the transfer 40 transfers 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 electronically controlled coupling 42 will be described later.

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

The high voltage battery 21 is a secondary battery mounted as a power source of the motor/generator 4, and for example, a lithium ion battery in which a cell module including a large number of cells is set in a battery pack case is used. The high-voltage battery 21 has a built-in junction box in which relay circuits for supplying/interrupting/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 voltage 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 for performing powering/regenerative control. That is, the inverter 26 converts the direct current from the DC harness 25 into a three-phase alternating current to the AC harness 27 during the power running to drive the motor/generator 4 by discharging the high voltage battery 21. In addition, when the high-power battery 21 is regenerated by the power generation of the motor/generator 4, the three-phase alternating current from the AC harness 27 is converted into the direct current to the DC harness 25.

The 12V battery 22 is a secondary battery mounted as a power source of a 12V load, which is an auxiliary machine, and for example, a lead battery mounted in an engine car 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 the voltage of several hundreds of volts from the high voltage battery 21 into 12V. By controlling the DC/DC converter 37 with the hybrid control module 81, the charge amount of the 12V battery 22 is reduced. It is configured to manage.

As a control system for an FF hybrid vehicle, as shown in FIG. 1, a hybrid control module 81 (abbreviation: “HCM”) is provided as an integrated control means having a function of appropriately managing energy consumption of the entire vehicle. As control devices connected to the hybrid control module 81, an engine control module 82 (abbreviation: “ECM”), a motor controller 83 (abbreviation: “MC”), 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 for “Controller Area Network”) so that bidirectional information can be exchanged.

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

The engine control module 82 performs fuel injection control, ignition control, fuel cut control, etc. of the horizontal engine 2.

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

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

The lithium battery controller 86 manages the battery SOC and battery temperature of the high voltage battery 21.

The 4WD control unit 85 inputs signals from the 4WD mode switch 94, wheel speed sensor 95, steering angle sensor 96, yaw rate sensor 97, G sensor 98, brake switch 99 and the like. Then, after performing a predetermined calculation process, the 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 the 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 rear wheels 11R, 11L are controlled. The controlled driving force distribution ratio is (step front wheel distribution ratio:rear wheel distribution ratio) from (100%:0%, front wheel drive) to (50%:50%, four-wheel equal distribution drive) Is the ratio.

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

As shown in FIGS. 2 and 3, the electronically controlled 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 clutch 50. A cam 51, a main cam 52, a ball 53, a main clutch 54, and a cam groove 55 are provided.

One end of the coupling input shaft 46 is connected to the propeller shaft 41, and the other end is 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-disc 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.

The control cam 51, the main cam 52, and the balls 53 sandwiched between the cam grooves 55, 55 formed in the two cams 51, 52 constitute a cam mechanism as shown in FIG.

Here, the fastening operation of the electronically controlled coupling 42 will be described. First, when a current is applied to 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. When the armature 49 is attracted to the armature 49, friction torque is generated in the control clutch 50, and the friction torque generated in the control clutch 50 is transmitted to the control cam 51 of the cam mechanism and becomes a restraining force in the circumferential direction. 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, 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 by the axial pressing force, a friction engagement torque proportional to the current value is generated in the main clutch 54. The friction 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 drive force distribution control system in the 4WD control unit 85 of the first embodiment. The configuration of the four-wheel drive force distribution control system will be described below with reference to FIG.

As a basic control system of the four-wheel drive force distribution control system, as shown by a solid line block in FIG. 4, an initial torque processing unit B01 based on vehicle speed, a differential rotation torque processing unit B02 based on front-rear differential rotation, and an accelerator opening degree. And a driving force distribution torque processing unit B03 based on the driving force. Then, a final command torque selection unit B04, which selects among the torques from the processing units B01, B02, and B03 by select high, is provided. Furthermore, 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 time (gradient gradient) block B05, and the torque whose decrease change rate is limited are used as the final command torque. And a final command torque block B07.

As the regeneration control intervention cooperative control system of the four-wheel drive force distribution control system, as shown by a dotted line block in FIG. 4, a regeneration control intervention prediction determination block B08, a torque switching block B09, and a control determination (steep) block. B10 and a gradient switching block B11 are provided.

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 or equal to the threshold, and the solenoid energization current is less than the threshold. When it is not maintained for a certain time or longer, the regeneration control intervention prediction determination signal is output (FIG. 5).

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

When the gradient switching block B11 receives the regenerative control intervention prediction determination signal from the regenerative control intervention prediction determination block B08, the normal switching gradient (slow gradient) to the control determination (steep gradient) from the normal time (slow gradient) block B05. ) Switching to the decreasing slope (steep slope) 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 limit threshold), the process proceeds to step S02, and if NO (vehicle speed VSP≦lower limit threshold), the process proceeds to step S06.

In step S02, following the determination in step S01 that vehicle speed VSP>lower limit threshold value, it is determined whether vehicle speed VSP is less than an upper 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<upper threshold), the process proceeds to step S03, and if NO (vehicle speed VSP≧upper threshold), the process proceeds to step S06.

In step S03, following the determination that vehicle speed VSP<the upper limit threshold in step S02, it is determined whether accelerator opening APO is less than the threshold. If YES (accelerator opening APO<threshold value), the process proceeds to step S04, and if NO (accelerator opening APO≧threshold value), the process proceeds to step S06.

Here, the threshold value of the accelerator opening APO is a threshold value for determining the accelerator OFF operation and is originally the accelerator opening APO=0 (accelerator OFF), but a small opening value considering sensor noise and the like. Is set to.

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

Here, the threshold value of the solenoid energizing current is a threshold value for determining that the solenoid energizing current is zero, and is originally zero, but is set to a slight current value in consideration of a minute fluctuation of the current. .. In addition, for a certain period of time, after the solenoid energizing current to the electronically controlled coupling 42 is set to zero, the time required for the releasing operation of the control clutch 50 and the main clutch 54 to be completed and the frictional engagement torque to become zero is experimentally determined. It is measured and set based on the measurement result.

In step S05, following the determination that the duration of solenoid energization current <threshold value in step S04 is less than a certain time, a regenerative control intervention prediction determination signal is output, and based on the output of this regenerative control intervention prediction determination signal, Cut off 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 decreasing gradient to the solenoid 45 of the electronic control coupling 42 is switched from the normal gradual decrease to the steep decrease to reduce the electronic control coupling 42. release.

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

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

[Regenerative control processing configuration based on accelerator opening]
FIG. 6 shows a flow of a regenerative control process based on the accelerator opening APO executed at the accelerator release operation in 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. In the case of YES (selection of the strong regeneration mode), the process proceeds to step S12, and in the case of NO (selection of the weak regeneration mode), the process proceeds to step S15.

Here, the "weak regeneration mode" and the "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 by the coast regeneration torque due to the accelerator release operation is set to a region corresponding to the engine brake. As shown in FIGS. 7 and 8, the “strong regenerative mode” means that the braking force generation region by the coast regenerative torque due to the accelerator release operation is expanded as compared with the “weak regenerative mode”, and when the deceleration request is made through the accelerator release operation, A mode in which the control performance of vehicle deceleration is enhanced. Then, as shown in the map of FIG. 7, each coast target driving force is set according to the vehicle speed VSP, and in the "strong regenerative mode", the maximum negative target in the medium vehicle speed range (for example, about 30 km/h). The driving force is set. Although not shown, in the first embodiment, for example, in the 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 arrow A in Fig. 7, when the accelerator is released to decelerate, the regeneration amount due to the coast regeneration torque gradually decreases. On the other hand, when the "strong regenerative mode" is selected, as shown by an arrow B in Fig. 7, when the accelerator is released to decelerate, the regenerative amount due to the coast regenerative torque increases. In other words, the "strong regenerative mode" does not require a brake pedal operation in most deceleration scenes and can control the braking force by an accelerator return/release operation. Therefore, the "strong regenerative mode" is sometimes referred to as the "1 pedal mode" in which drive/braking is controlled by the accelerator work on the accelerator pedal.

In addition, 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 the regenerative braking force that is applied when the accelerator is off and the brake is on. “Mechanical brake” is a brake hydraulic braking force that compensates when the braking force cannot be satisfied only by the regeneration amount 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 value, as in step S03. If YES (accelerator opening APO<threshold value), the process proceeds to step S13, and if NO (accelerator opening APO≧threshold value), the process proceeds to step S15.

Here, the threshold value of the accelerator opening APO is a threshold value for determining the accelerator OFF operation and is originally the accelerator opening APO=0 (accelerator OFF), but a small opening value considering sensor noise and the like. Is set to.

In step S13, following the determination in step S12 that the accelerator opening APO is smaller than the threshold value or the determination in step S14 that the predetermined time has not elapsed, 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 the direction in which the deceleration force is limited.

Here, the "negative drive force limit" means the negative drive force generated in the drive system when a predetermined limit value is reached with the increase of the coast regenerative torque by the motor/generator 4 due to the selection of the strong regenerative mode. It means suppressing an increase in the amount of regeneration so as to maintain the predetermined limit value.

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

In addition, 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 at which the occupant does not feel a shock or an abnormal noise. Then, 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 diameters of the front and rear wheels are changed to values smaller than the limit value when the tire diameters of the front and rear wheels are the same diameter, depending on the difference in tire diameters. To be 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, and if NO (predetermined time has not elapsed), the process returns to step S13.

Here, the “predetermined time” is the time required from when the clutch release command is output to when the clutch release command is output based on the release response time of the electronically-controlled coupling 42 until the clutch is securely released (for example, 0.2sec). When the release command is output to the electronic control coupling 42, the time required from the start of the output of the release command until the actual clutch capacity is released and the clutch is released is acquired in advance by experiments 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 the negative driving force" means to maintain the limit release state when shifting from the state where the negative driving force is not limited, and shift from the state where the negative driving force is limited. When doing, it means to release the restricted state.

Next, the operation will be described.
The action of Example 1 is "shock/noise generation mechanism during regenerative control intervention", "shock/noise generation action in Comparative Example", "shock/noise suppression action in Example 1", "negative" The characteristic effect of the driving force limitation control of the above" will be described separately.

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

The section (1) is an accelerator ON drive state in which torque is transmitted from the drive source to the drive wheels, and is a section in which the propeller shaft torque gradually rises. In this section (1), the control cam 51 and the main cam are The ball 53 is sandwiched between the cam grooves 55 formed in 52, and the main clutch 54 is fastened by 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, which causes the propeller shaft torque to rapidly increase and decrease, 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 by a large torque transmission (drive).

The section (3) is a section in which the torque of the propeller shaft torque decreases to the negative coast state due to the increase of the regenerative torque. In this section (3), the main clutch 54 is engaged with large torque transmission (coast) with the ball 53 being held between the cam grooves 55 formed in the control cam 51 and the main cam 52. That is, the coast torque is transmitted before the cam is reversed.

In the section (4), when the propeller shaft torque is in a negative coast state, the regenerative torque>coupling torque causes the control cam 51 to start reversing, and the ball 53 between the cam grooves 55, 55 is changed from being pinched to being free. It is a section. In this section (4), the torque is released all at once and enters the neutral state, so that the large coast torque abruptly changes toward zero torque, and shock and abnormal noise are generated due to this change torque.

As described above, the control cam 51 and the main cam 52 of the electronically controlled coupling 42 are distorted due to the intervention of the regenerative control to have a 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, and a shock or abnormal noise occurs.

[Shock/abnormal noise generation effect in comparative example]
First, it is assumed that the transmission torque control to the electronically controlled coupling by the accelerator operation and the regenerative torque control by the brake operation are independently controlled without performing the cooperative control. In this case, when the regenerative torque control intervenes, since the electronically controlled coupling has the clutch capacity, the shock/abnormal noise is generated as described in the above generation mechanism.

Therefore, when the regenerative control by the motor/generator intervenes, shock and abnormal noise are generated by performing the coordinated control to set the transmission torque of the electronically controlled coupling to zero and to disengage the clutch capacity before starting the regenerative control. Can be suppressed. Therefore, a comparative example is one in which cooperative control is performed to remove the clutch capacity of the electronically controlled coupling from the timing when the accelerator is turned off before the brake cooperative regeneration based on the brake operation is started.

In this comparative example, the PWT generated driving force when the "weak regeneration mode" is selected 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. At, the positive driving force shifts to the negative driving force. Then, a small coast regenerative torque is maintained and maintained until the brake ON time t4, and after the brake ON time t4, the regeneration amount by the brake cooperative regeneration is reduced. That is, 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 at which shock and abnormal noise are generated. This is because the pedal change time from the accelerator OFF time t2 to the brake ON time t4 is long, and this pedal change time can be used as a margin time Δt until the electronic control coupling is released. In addition, "PWT" means a power train (driving system).

However, as shown by the solid line characteristic D in FIG. 10, the PWT generated driving force when the “strong regenerative mode” is selected, when the accelerator release operation is started at time t1, the accelerator is turned off due to an increase in coast regenerative torque. Before the time t2 is reached, the positive driving force is changed to the negative driving force. Then, the coast regenerative torque continues to increase from the accelerator off time t2 to the brake start time t3 to the brake on time t5, and after the brake on time t5, the regenerative amount including coast regenerative braking cooperative regeneration decreases. .. Therefore, the negative driving force reaches the limit value at which the shock/abnormal noise is generated at time t4 before the clutch release time t6 when the clutch capacity of the electronically controlled coupling is released. After that, at the clutch disengagement time t6, the negative driving force decreases to a level exceeding the limit value for generating a shock or abnormal noise. This is because the selection of the "strong regenerative mode" virtually eliminates the stepping time from the accelerator OFF to the brake ON, and the reduction in the regeneration amount cannot be suppressed. Therefore, there is a large change from drive torque (positive driving force) to coast torque (negative driving force) with the clutch capacity held by the electronically controlled coupling, and suddenly when the coast torque exceeds the capacity due to cam distortion, two The cam moves relative to each other, causing shock and noise.

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

The operation of the 4WD control process executed by the 4WD control unit 85 will be described with reference to FIG. The regenerative vehicle speed condition (lower limit threshold<vehicle speed<upper threshold) is satisfied, and the accelerator release condition (accelerator opening APO<threshold) is satisfied. Then, when the duration of the solenoid energizing current <threshold value is less than the fixed time when the accelerator release condition is satisfied, that is, when the electronically controlled coupling 42 is in the engaged state when the accelerator is off, in the flowchart of FIG. The process proceeds to step S02→step S03→step S04→step S05. In step S05, the initial torque control and the differential rotation control are cut off, and the electronically controlled coupling 42 is released. At this time, the decreasing gradient of the solenoid energizing current is switched from the decrease due to the normal gentle gradient to the decrease due to the steep gradient.

Then, when the duration of solenoid energization current <threshold value is a certain time or more, that is, when the electronically controlled coupling 42 is released 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 in which they are not cut.

Next, the regeneration control processing operation of the hybrid control module 81 will be described based on FIG. When the "weak regeneration mode" is selected, the process proceeds to step S11→step S15→end in the flowchart of FIG. Further, when the “strong regenerative mode” is selected but the accelerator release condition is not satisfied (accelerator opening APO≧threshold value), the process proceeds to step S11→step S12→step S15→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 regenerative mode" is selected and the accelerator release condition is satisfied (accelerator opening APO<threshold value), the process proceeds to step S11→step S12→step S13 in the flowchart of FIG. In step S13, negative driving force limit control for suppressing the decrease in the regeneration amount to the limit value is started. Then, 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 for suppressing the decrease of the regeneration amount to the limit value is maintained. It Then, when a predetermined time has elapsed from the start of the negative driving force limitation control, the process proceeds from step S14 to step S15 in the flowchart of FIG. 6, and the negative driving force limitation is released.

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

In the case of the first embodiment, the PWT-generated driving force when the “strong regenerative mode” is selected is, as shown by the solid line characteristic E in FIG. 11, when the accelerator release operation is started at time t1, the coast regenerative torque Due to the increase, the positive driving force is changed to the negative driving force before the accelerator OFF time t2 is reached. 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 During this period, the amount of regeneration by coast regeneration and brake coordinated regeneration is limited so as not to fall below the limit value. Therefore, at the clutch release time t6 (<time t7) when the clutch capacity of the electronically controlled coupling 42 is removed, the negative driving force is maintained at the limit value, and the occurrence of shock and abnormal noise is suppressed.

In other words, by selecting the "strong regenerative mode", the margin of the pedal change from accelerator OFF to brake ON, in which the reduction of the negative driving force is suppressed, is substantially eliminated. However, until the clutch capacity of the electronically controlled coupling 42 is removed, regenerative control is performed so that the regenerative amount by coast regenerative and brake cooperative regenerative does not fall below the negative drive force limit value. Is.

[Characteristic effect of negative driving force limit control]
In the first embodiment, when the deceleration is requested, 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 regeneration amount of the motor/generator 4. When the release control of the electronically controlled coupling 42 and the driving force reduction control overlap, a negative driving force is limited by the driving force reduction control until the actual clutch capacity of the electronically controlled coupling 42 is exhausted.

That is, when a deceleration request is made, the negative driving force increases due to the driving force reduction control before the actual clutch capacity of the electronically controlled coupling 42 is released, and the electronically controlled coupling 42 shifts from positive torque to neutral state to negative torque. Then, they found that shock occurred.
Therefore, focusing on the driving force reduction control side that is not affected by the release response of the electronically controlled coupling 42, the cooperative control that limits the negative driving force by the driving force reduction control until the actual clutch capacity of the electronically controlled coupling 42 is exhausted. To do.
Therefore, at the time of deceleration request in which the clutch release control and the driving force reduction control overlap, a shock is prevented from occurring regardless of the presence/absence or the length of the stepping time.

In the first embodiment, when limiting the negative drive force by the drive force reduction control, when the predetermined limit value is reached due to the increase in the regenerative amount by the motor/generator 4, the regenerative amount is maintained at the predetermined limit value. Suppress the increase of.

For example, the deceleration request includes an accelerator release operation and a stepping operation 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. Will grow. Moreover, due to recent demands for fuel efficiency, the amount of regeneration at the time of accelerator release operation is increasing. Therefore, when limiting the negative driving force, pay attention to the amount of regeneration by the motor/generator 4 that has better control response and higher control accuracy than the brake fluid pressure in the mechanical brake, and suppresses an increase in the amount of regeneration. did.
Therefore, when limiting the negative driving force, the negative driving force is limited to the limit value by the regenerative amount control that provides good control responsiveness and high control accuracy.

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

That is, in the case of the ball-cam type electronically controlled coupling 42, if a large negative driving force is generated before the release, not only a shock is generated, but also an abnormal noise due to a hitting sound when the ball 53 collides with the cam groove 55. appear.
Therefore, when a deceleration request in which the release control of the electronically controlled coupling 42 and the driving force reduction control overlap, a shock and an abnormal noise are prevented from occurring.

In Example 1, the limit value of the amount of regeneration is changed to a value smaller than the limit value when the tire diameters of the front and rear wheels are the same when the tire diameters of the front and rear wheels have different diameters, depending on the difference in the different diameters of the tires. To do.

That is, when a tire with a different diameter is worn, the load applied to the front and rear of the cam of the electronically controlled coupling 42 changes, and the greater the difference in the different diameters of the tires, the greater the abnormal noise due to the collision impact sound. Therefore, when tires of different diameters are worn on the front and rear wheels, generation of abnormal noise is suppressed regardless of the difference in diameter of the tires.

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

That is, in the strong regenerative mode, the coast line of the target driving force is lowered, 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. Will end up.
Therefore, at the time of accelerator release operation in which the release control of the electronically-controlled coupling 42 and the regenerative control in the strong regenerative mode overlap, a shock is prevented from occurring due to an increase in the regenerative amount before the clutch capacity of the electronically-controlled coupling 42 is removed. It

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

(1) The drive source has a motor/generator 4, the left and right front wheels 10L, 10R are the main drive wheels connected to the drive source, and the left and right rear wheels 11L, 11R are the drive sources and a friction clutch (electronically controlled coupling 42) The auxiliary drive wheel is connected via.
When a deceleration request is made in the four-wheel drive state by engaging the friction clutch (electronically controlled coupling 42), a release command is output to the friction clutch.
In this control method for a 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 to the negative drive force region including the regeneration amount by the motor/generator 4. The driving force reduction control is performed to reduce the driving force.
At the time of deceleration request in which the release control of the friction clutch (electronically controlled coupling 42) and the driving force reduction control overlap, a negative driving force by the driving force reduction control is applied until the actual clutch capacity of the friction clutch (electronically controlled coupling 42) is exhausted. Limit (Fig. 11).
Therefore, a control method for a four-wheel drive electric vehicle (four-wheel drive hybrid vehicle) that prevents a shock from occurring regardless of whether or not there is a stepping time and the length of the deceleration request when the clutch release control and the driving force reduction control overlap is provided. 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 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 4, the increase in the regeneration amount is suppressed so as to be maintained at the predetermined limit value. (FIG. 11).
Therefore, in addition to the effect of (1), when limiting the negative driving force, the negative driving force can be limited to the limit value by the regenerative amount control that can obtain 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 with which the vehicle front-rear G change rate due to the increase of the regeneration amount becomes equal to or less than a predetermined change rate (FIG. 11).
Therefore, in addition to the effect of (2), it is possible to prevent the occurrence of shock and abnormal noise when the deceleration request in which the release control of the electronically-controlled coupling 42 and the driving force reduction control overlap is requested.

(4) When the tire diameters of the front and rear wheels are different, 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, depending on the difference in the different diameters of the tires ( (Fig. 11).
Therefore, in addition to the effect of (3), when wearing tires of different diameters on the front and rear wheels, generation of abnormal noise can be suppressed regardless of the difference in diameter of the tires.

(5) When releasing the accelerator in four-wheel drive by engaging the friction clutch (electronically controlled coupling 42), output a release command to the friction clutch (electronically controlled coupling 42) when the accelerator opening APO falls below a threshold value. 4 wheel drive control is performed.
During the accelerator release operation, regenerative control is performed in the strong regenerative mode in which the coast regenerative torque generated by the motor/generator 4 is expanded more than the engine brake equivalent.
Disengagement response of the friction clutch (electronically controlled coupling 42) after the accelerator opening APO becomes equal to or less than the threshold value during accelerator release operation when the release control of the friction clutch (electronically controlled coupling 42) and the regenerative control in the strong regeneration mode overlap. The negative driving force is limited by suppressing an increase in the regeneration amount until a predetermined time set in advance by experiments based on the time has elapsed (FIG. 6).
Therefore, in addition to the effects of (1) to (4), the friction clutch (electronically controlled coupling 42) is released during the accelerator release operation in which the release control of the frictional clutch (electronically controlled coupling 42) and the regenerative control in the strong regeneration mode overlap. It is possible to prevent the occurrence of a shock due to an increase in the amount of regeneration before the clutch capacity is removed.

(6) The drive source has the motor/generator 4, the left and right front wheels 10L, 10R are the main drive wheels connected to the drive source, and the left and right rear wheels 11L, 11R are the drive sources and the friction clutch (electronically controlled coupling 42) The auxiliary drive wheel is connected via.
A 4WD controller (4WD control unit 85) that outputs a release command to the friction clutch when a deceleration request is made in a four-wheel drive state by engaging the friction clutch (electronically controlled coupling 42) is provided.
In this control device for a four-wheel drive electric vehicle (four-wheel drive hybrid vehicle), when a deceleration request is made, the drive force generated in the drive force transmission system is directed to the negative drive force region including the regeneration amount by the motor/generator 4. A driving force controller (hybrid control module 81) that performs driving force reduction control for reducing the driving force is provided.
The driving force controller (hybrid control module 81), when the deceleration request in which the release control of the friction clutch (electronically controlled coupling 42) and the driving force reduction control overlap, is performed, until the actual clutch capacity of the frictional clutch (electronically controlled coupling 42) is released. , 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 a shock from occurring regardless of whether or not there is a stepping time and the length of the deceleration request when the clutch release control and the driving force reduction control overlap each other. Can be provided.

The second embodiment is an example in which the 4WD control for controlling the clutch capacity of the electronically controlled coupling is performed by the target driving force instead of the control by the accelerator opening of the first embodiment.

First, the configuration will be described.
The "overall system configuration" and the "detailed configuration of the electronically controlled coupling" are the same as those in the first embodiment, and therefore illustration and description thereof are omitted. The "4WD control processing configuration and the regenerative control processing configuration based on the target driving force" will be described below.

[4WD control processing configuration and regenerative control processing configuration based on target driving force]
Regarding the 4WD control processing configuration, the determination whether or not the accelerator opening degree <threshold value in step S03 of FIG. 5 in the first embodiment is replaced with the 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) during the accelerator release operation is set to a predetermined value, and when the target driving force becomes equal to or less than the predetermined value, the electronically controlled coupling 42 is released.

FIG. 12 shows a flow of a regenerative control process based on a target driving force executed at the time of accelerator release operation in 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. In the case of YES (selection of the strong regeneration mode), the process proceeds to step S22, and in the case of NO (selection of the 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 the target driving force is equal to or less than a predetermined value. If YES (target drive force≦predetermined value), the process proceeds to step S23, and if NO (target drive force>predetermined value), the process proceeds to step S25.

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

In step S23, following the determination in step S22 that the target drive force≦the predetermined value or the determination that the predetermined time has not elapsed in step S24, the negative drive 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.
The “shock/abnormal noise generation mechanism at the time of intervention of regenerative control” and the “shock/abnormal noise generation action in the comparative example” are the same as those in the first embodiment, and a description thereof will be omitted. Hereinafter, the "shock/abnormal noise suppressing action in the second embodiment" will be described.

[Shock/abnormal noise suppressing action in the second embodiment]
In the second embodiment, the shock/sound suppressing action in the deceleration request scene in which the release control of the electronically controlled coupling 42 and the regenerative control in which the negative driving force increases will be described.

First, the regeneration control processing operation of the hybrid control module 81 will be described with reference to FIG. When the "weak regeneration mode" is selected, the process proceeds to step S21→step S25→end in the flowchart of FIG. Further, when the “strong regeneration mode” is selected but the target driving force condition is not satisfied (target driving force>predetermined value), in the flowchart of FIG. 12, step S21→step S22→step S25→end. 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 to step S21→step S22→step S23 in the flowchart of FIG. In step S23, the negative driving force limit control for suppressing the decrease in the regeneration amount to the limit value is started. Then, until the predetermined time elapses, the flow from step S23 to step S24 in the flowchart of FIG. 12 is repeated, and the negative driving force limit control for suppressing the decrease of the regeneration amount to the limit value is maintained. It Then, when a predetermined time has elapsed from the start of the negative driving force limitation control, the process proceeds from step S24 to step S25 in the flowchart of FIG. 12, and the negative driving force limitation is released.

Therefore, as in the case of FIG. 11 in the first embodiment, the amount of regeneration due to coast regeneration and brake cooperative regeneration is restricted 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. It Therefore, when the clutch capacity of the electronically controlled coupling 42 is released and the clutch is released, the negative driving force is maintained at the limit value, and the occurrence of shock and abnormal noise is suppressed.

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

(7) Disengagement control of the friction clutch (electronically controlled 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 (electronically controlled coupling 42) after the target drive force becomes equal to or less than the predetermined value when the deceleration request in which the release control of the frictional clutch (electronically controlled coupling 42) and the driving force reduction control overlap is performed. The negative driving force by the driving force reduction control is limited until the set time set by the above has passed (FIG. 12).
Therefore, when the release control of the friction clutch (electronically controlled coupling 42) and the driving force reduction control overlap with each other, the target driving force is reduced before the clutch capacity of the frictional clutch (electronically controlled coupling 42) is removed. It is possible to prevent the occurrence of shock due to.

The third embodiment is an example in which a clutch capacity estimated value (actual clutch capacity) is calculated during the 4WD control for controlling the clutch capacity of the electronically controlled coupling.

First, the configuration will be described.
The "overall system configuration" and the "detailed configuration of the electronically controlled coupling" are the same as those in the first embodiment, and therefore illustration and description thereof are omitted. The "4WD control processing configuration and the regenerative control processing configuration based on the target driving force" will be described below.

[4WD control processing configuration and regenerative control processing configuration based on target driving force]
Regarding the 4WD control processing configuration, the control for releasing the electronically controlled coupling 42 is performed based on the determination that accelerator opening<threshold value in the first embodiment or the target driving force≦predetermined value in the second embodiment. Then, when the electronically controlled coupling 42 is disengaged, an estimated clutch capacity value (actual clutch capacity) is calculated, and feedback control is performed based on, for example, a deviation from the target clutch capacity.

FIG. 13 shows a flow of a regenerative control process based on a target driving force executed at the time of accelerator release operation in 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. In the case of YES (selection of the strong regeneration mode), the process proceeds to step S32, and in the case of NO (selection of the 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 the clutch capacity estimated value is equal to or greater than a predetermined value. If YES (clutch capacity estimated value≧predetermined value), the process proceeds to step S33, and if NO (clutch capacity estimated value<predetermined value), the process proceeds to step S34.

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

In step S33, following the determination in step S32 that the clutch capacity estimated value≧the predetermined value, 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 electronically controlled coupling 42 is not disengaged.

In step S34, following the determination that the weak regeneration mode is being selected in step S31 or the clutch capacity estimated value <predetermined value in step S32, the negative driving force is not limited and the end is performed. Go to. That is, when the process proceeds from step S32 to step S34, the limitation of the negative driving force is released based on the determination that the clutch capacity of the electronically controlled coupling 42 is released and the clutch is released.

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

[Shock/abnormal noise suppressing action in Example 3]
In the third embodiment, the shock/sound suppressing action in the deceleration request scene in which the release control of the electronically controlled coupling 42 and the regenerative control in which the negative driving force increases overlaps will be described.

First, the regeneration control processing operation of the hybrid control module 81 will be described with reference to FIG. When the "weak regeneration mode" is selected, the process proceeds to step S31→step S34→end in the flowchart of FIG. Further, when the “strong regenerative mode” is selected but the clutch engagement condition is not satisfied (clutch capacity estimated 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, when the "strong regenerative mode" is selected and the clutch engagement condition is satisfied (clutch capacity estimated value ≥ predetermined value), in the flowchart of Fig. 13, step S31 → step S32 → step S33 → end Go to. In step S33, negative driving force limit control is performed to suppress the decrease in the regeneration amount to the limit value.

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

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

(8) The disengagement control of the friction clutch (electronically controlled coupling 42) is performed while calculating the clutch capacity estimated value of the friction clutch (electronically controlled coupling 42). At the time of deceleration request in which the release control of the friction clutch (electronically-controlled coupling 42) and the driving force reduction control overlap, a negative driving force by the driving force reduction control is limited while the clutch capacity estimated value is a predetermined value or more (FIG. 13). ..
Therefore, when a deceleration request in which the disengagement control of the friction clutch (electronically controlled coupling 42) and the driving force reduction control overlap, a negative driving force is reduced before the actual clutch capacity of the frictional clutch (electronically controlled coupling 42) is removed. It is possible to prevent a shock from being generated.

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

In the first to third embodiments, as the deceleration request, the example of the pedal operation by the driver which is the accelerator release operation or the stepping operation from the accelerator release to the brake depression is shown. However, the deceleration request also includes the case of a vehicle equipped with a cruise control system, an autonomous driving vehicle, or the like that outputs a deceleration request equivalent 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 hybrid control module (HCM) and the vehicle behavior controller (VDC) are provided with the functions shown in the concept block diagram of FIG. That is, FIG. 14 shows required functions for the hybrid control module (HCM) and the vehicle behavior controller (VDC) to realize cooperative control of clutch release control and driving force reduction control. In addition, in FIG. 14, "ACEP" shows a "strong regeneration mode" and "Norma" shows a "weak regeneration mode."

In Examples 1 to 3, the ball clutch 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 a ball cam type electronically controlled coupling, and if the friction clutch controls front and rear wheel driving force distribution by an external command, a multi-disc clutch or the like operated by control hydraulic pressure can be used. Good as an example.

In Examples 1 to 3, an example in which the control device of the present disclosure is applied to an FF-based four-wheel drive hybrid vehicle has been shown. However, the control device of the present disclosure can be applied not only to the FF-based four-wheel drive hybrid vehicle but also to the FR-based four-wheel drive hybrid vehicle. Further, 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 that has a motor/generator as a drive source and has a friction clutch that controls front and rear wheel drive force distribution in the drive force transmission path from the drive source to the auxiliary drive wheels by an external command Can be applied.

Claims (8)

A drive source has a motor/generator, and one of the left and right front wheels and the left and right rear wheels is the 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 the auxiliary drive wheel,
A method for controlling a four-wheel drive electric vehicle, which outputs a release command to the friction clutch when deceleration is requested in a four-wheel drive state by engaging the friction clutch,
When a deceleration request is made, the driving force generated in the driving force transmission system is reduced to a negative driving force range that includes the amount of regeneration by the motor/generator, and the driving force reduction control is performed.
When a deceleration request in which the friction clutch disengagement control and the driving force reduction control overlap is requested, the negative driving force by the driving force reduction control is limited until the actual clutch capacity of the friction clutch is exhausted. Electric vehicle control method. The method for controlling a 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 increase in the regeneration amount is maintained so as to maintain the predetermined limit value. A method for controlling a four-wheel drive electric vehicle, comprising: The method for controlling a four-wheel drive electric vehicle according to claim 2,
The friction clutch is a ball cam type electronically controlled coupling,
The method for controlling a four-wheel drive electric vehicle, wherein the limit value of the regeneration amount is set to a negative driving force value with which the vehicle front-rear G change rate due to the increase in the regeneration amount becomes equal to or less than a predetermined change rate. The method for controlling a four-wheel drive electric vehicle according to claim 3,
When the tire diameters of the front and rear wheels are different, 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, depending on the difference in the different diameters of the tires. And a method for controlling a four-wheel drive electric vehicle. A control method for a 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 engaging the friction clutch, four-wheel drive control is performed to output a release command to the friction clutch when the accelerator opening becomes equal to or less than a threshold value.
At the time of accelerator release operation, the regenerative control is performed by 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 release control of the friction clutch and the regenerative control in the strong regeneration mode overlap, the predetermined time set based on the release response time of the friction clutch elapses after the accelerator opening becomes equal to or less than the threshold value. The method for controlling a four-wheel drive electric vehicle is characterized in that the negative driving force is limited by suppressing an increase in the regeneration amount. A control method for a four-wheel drive electric vehicle according to any one of claims 1 to 4,
The release control of the friction clutch is performed according to the target driving force set based on the accelerator opening and the vehicle speed,
At the time of deceleration request in which the release control of the friction clutch and the driving force reduction control overlap, until the set time set based on the release response time of the friction clutch elapses after the target drive force becomes equal to or less than a predetermined value. A method for controlling a four-wheel drive electric vehicle, comprising: limiting a negative driving force by the driving force reduction control. A control method for a four-wheel drive electric vehicle according to any one of claims 1 to 4,
The release control of the friction clutch is performed while calculating the clutch capacity estimated value of the friction clutch,
When the deceleration request in which the friction clutch disengagement control and the driving force reduction control overlap is requested, the negative driving force by the driving force reduction control is limited while the clutch capacity estimated value is equal to or more than a predetermined value. Driving electric vehicle control method. A drive source has a motor/generator, one of the left and right front wheels and one of 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 including:
An accelerator opening detection device that detects or estimates the accelerator opening,
A vehicle speed detection device that detects or estimates the vehicle speed,
A 4WD controller that outputs a release command to the friction clutch when the accelerator pedal is released in a four-wheel drive state by engaging the friction clutch.
When the accelerator pedal is released, the motor/generator is provided with a drive force controller that generates a negative drive force set according to the vehicle speed.
The driving force controller limits the negative driving force to a predetermined value or less for a predetermined time when the accelerator pedal is released in the four-wheel drive state in which the friction clutch is engaged and the release state is set. A control device for a four-wheel drive electric vehicle.

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