JP2016165942A - Power transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power transmission device capable of performing more proper regenerative power generation.SOLUTION: A power transmission device is mounted in a four-wheel drive vehicle. An ECU of the power transmission device stops power feeding to a motor (S105) in a travel state in which four-wheel driving is not required (S104:NO) when lowering of residual quantity of a storage battery is detected (S102:YES). After that, the ECU sets transmission torque of an electronic control coupling (S107, S109, S111) according to the travel state of the vehicle (S106, S108, S110). Rotation power of rear wheels is transmitted to the motor according to the transmission torque of the electronic control coupling. The motor generates power by rotating according to the transmission torque of the electronic control coupling and the generated power is regenerated in the storage battery. The ECU finishes power generation by the motor (S103) by setting the transmission torque of the electronic control coupling to 0% when the residual quantity recovery of the storage battery is detected (S102:NO).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a power transmission device.

  For example, as described in Patent Document 1, conventionally, there is a vehicle in which front wheels are driven by an engine and rear wheels are driven by a motor. The vehicle control device controls the motor in accordance with the running state of the vehicle and the like, thereby applying the torque of the motor that is required from time to time to the rear wheels. Further, the motor functions as a generator under circumstances such as when the vehicle is decelerated. The rotational resistance during power generation in this motor is used as a braking force. Moreover, the electric power as the regenerative energy generated is supplied to the storage battery of the vehicle and used for charging.

JP 2014-69657 A

  However, there are concerns about the following in vehicles that perform regenerative power generation using a motor that is one of the power sources for traveling, including the vehicle described in Patent Document 1. For example, when the vehicle decelerates, the motor rotates in conjunction with the rear wheels, so it is difficult to control the amount of power generated by the motor. Since the capacity of the storage battery is limited, it may soon reach a fully charged state. And after this, when the electric power generated by the motor is supplied to the storage battery, the storage battery may be overcharged and its deterioration may be promoted.

  An object of the present invention is to provide a power transmission device capable of performing more appropriate regenerative power generation.

  The power transmission device capable of achieving the above object includes the sub drive of a four-wheel drive vehicle having left and right main drive wheels to which power is always transmitted and left and right sub drive wheels to which power is transmitted according to a traveling state. It transmits power to the wheels.

  The power transmission device consumes electric power supplied from the on-vehicle storage battery and rotates to generate power transmitted to the sub drive wheel, while power supply is stopped to the sub drive wheel. The power transmission rate between the motor and the auxiliary drive wheel is continuously changed between 0% and 100% through electronic control and a motor that generates electric power regenerated in the storage battery by rotating in conjunction. And a control device for controlling the motor and the coupling, respectively.

  The control device stops power supply to the motor and sets the power transmission rate to a value larger than 0% when the remaining amount of the storage battery falls below a predetermined threshold value while the vehicle is running. While power generation by the motor is started by setting, when the remaining amount of the storage battery recovers beyond a predetermined threshold value, power generation by the motor is terminated by setting the power transmission rate to 0% To do.

  According to this configuration, power generation by the motor is started when the remaining amount of the storage battery falls below a predetermined threshold during traveling of the vehicle. When the power supply to the motor is stopped, the rotational force of the auxiliary drive wheel is transmitted to the motor in accordance with the power transmission rate of the coupling. The motor generates electricity by rotating in accordance with the transmitted rotational force. On the other hand, when the remaining amount of the storage battery recovers beyond a predetermined threshold, power generation by the motor is terminated. As described above, more appropriate regenerative power generation is performed in accordance with the remaining amount of the storage battery, thereby suppressing the generation of surplus power by the motor and thus the overcharge of the storage battery.

In the above power transmission device, it is preferable that the power transmission rate set when power generation by the motor is started is set to a different value depending on a traveling state of the vehicle.
Here, the power generation amount of the motor increases as the rotational force transmitted to the motor through the coupling increases. At this time, not only the power generation amount but also the regenerative braking force by the motor increases. For this reason, depending on the running state of the vehicle, the driver may feel a slight impact due to the regenerative braking force by the motor. In this regard, as in the above-described configuration, the value of the coupling power transmission rate that is set when starting regenerative power generation by the motor varies depending on the traveling state of the vehicle. More appropriate regenerative power generation is performed. Further, since it is possible to generate a more appropriate regenerative braking force according to the traveling state of the vehicle, the riding comfort of the vehicle is also ensured.

  In the power transmission device, when the power transmission rate is set when the power generation by the motor is started, the control device gradually changes the power transmission rate before the setting to the power transmission rate after the setting. It is preferable.

  In this way, it is possible to reduce the impact associated with a sudden change in the power transmission rate of the coupling. The larger the difference between the power transmission rate of the coupling before the change and the target power transmission rate, the more effective.

  In the above power transmission device, the control device is configured to detect the motor when a running state that requires four-wheel drive is detected, even when the remaining amount of the storage battery has dropped below a predetermined threshold value. It is preferable to drive the left and right auxiliary drive wheels through the control.

Thus, by giving priority to the traveling of the four-wheel drive to the charging of the storage battery, the traveling stability of the vehicle can be ensured continuously.
In the above power transmission device, the control device may detect a traveling state in which four-wheel drive is required based on at least one of a difference between front and rear wheel speeds and a difference between left and right wheel speeds.

  It is possible to detect the slip of the front wheel or the rear wheel based on the wheel speed difference between the front and rear. Further, it is possible to detect the vehicle's curve traveling based on the difference between the left and right wheel speeds. From the viewpoint of ensuring traveling stability, when slip occurs or when traveling on a curved road, traveling by four-wheel drive is preferable.

  The power transmission device may include a differential mechanism that distributes the power of the motor to the left and right auxiliary drive wheels. In this case, it is preferable that the coupling is provided between the motor and the differential mechanism. Only one coupling may be provided.

  In the power transmission device, the motor may include first and second motors. In this case, it is preferable that the first and second motors are connected to the left and right auxiliary driving wheels via the couplings, respectively.

  According to this configuration, the left and right auxiliary drive wheels are independently driven by the two motors. In this case, by providing couplings between the two motors and the left and right auxiliary drive wheels, the power transmission rate between the two motors and the left and right auxiliary drive wheels can be freely changed. Become.

  In the power transmission device described above, the traveling state of the vehicle is at least one of a first traveling state traveling at a constant speed, a second traveling state traveling inertially on a downhill, and a third traveling state decelerating by a brake. May be included. In this case, the control device determines the first travel state based on the vehicle speed, the second travel state based on the vehicle speed and the accelerator operation state, and the third travel state based on the vehicle speed and the brake operation state. Each may be determined.

  By changing the power transmission rate of the coupling according to at least one of the first to third traveling states, it is possible to ensure the riding comfort of the vehicle in the first to third traveling states. This is because the preferable magnitude of the regenerative braking force varies depending on the traveling state of the vehicle. For example, when the vehicle is traveling steadily, it is preferable to suppress the coupling power transmission rate because it is desired to suppress the impact accompanying the change in the coupling power transmission rate as much as possible. On the other hand, when the vehicle decelerates due to a brake operation, the driver's intention to decelerate is clear, so the power transmission rate of the coupling and thus the regenerative braking force may be increased.

  According to the power transmission device of the present invention, more appropriate regenerative power generation can be performed.

The block diagram which shows schematic structure of the vehicle by which the power transmission device in 1st Embodiment is mounted. The flowchart which shows the control procedure of the coupling in 1st Embodiment. The flowchart which shows the control procedure of the coupling in 2nd Embodiment. The block diagram which shows an example of the power transmission device in 3rd Embodiment.

<First Embodiment>
Hereinafter, a first embodiment in which the power transmission device is embodied in a four-wheel drive vehicle will be described.
As shown in FIG. 1, the vehicle 11 includes an internal combustion engine (engine) 12 that is a main drive source for traveling. The driving force of the internal combustion engine 12 is transmitted to the left and right front wheels 16 and 16 via the transmission 13, the front differential gear 14, and the left and right front drive shafts 15 and 15, respectively. When the vehicle 11 travels (forwards and reverses), the driving force generated by the internal combustion engine 12 is always transmitted to the left and right front wheels 16 and 16.

  The vehicle 11 includes a storage battery (BAT) 21 and a power transmission device 22. The power transmission device 22 includes a motor 23 as an auxiliary drive source for traveling, an electronic control coupling 24, a rear differential gear 25, and an ECU (electronic control device) 26.

  The driving force (torque) of the motor 23 is transmitted to the left and right rear wheels 28 and 28 via the output shaft 23s, the electronic control coupling 24, the rear differential gear 25, and the left and right rear drive shafts 27 and 27, respectively. .

  As the motor 23, for example, a shunt DC machine is employed. A shunt DC machine is one in which an armature winding and a field winding are connected in parallel to each other. The motor 23 functions as a generator (separately-excited generator) when the vehicle 11 travels at a reduced speed or inertia. The separately-excited generator refers to a device that uses another power source instead of its own electromotive force as a power source for a field winding that generates a magnetic field. Here, the field current supplied to the motor 23 is kept constant.

  The electronic control coupling 24 transmits the driving force of the motor 23 to the rear differential gear 25. The electronic control coupling 24 is changed steplessly between 0% and 100% of its transmission torque (power transmission rate) through electronic control by the ECU 26. Although illustration is omitted, the electronic control coupling 24 includes a main clutch (multi-plate friction clutch), a pilot clutch (electromagnetic multi-plate clutch), a cam mechanism, and an electromagnet. The pilot clutch is engaged by the electromagnetic force of the electromagnet, and the engagement force (friction torque) is transmitted to the main clutch via the cam mechanism, whereby the main clutch is engaged. By controlling the current supplied to the electromagnet, the transmission torque of the electronic control coupling 24 can be controlled.

  The storage battery 21 is an operation power source for various electric components including the motor 23, the electronic control coupling 24, and various computer devices including the ECU 26. The storage battery 21 stores electric power generated by a motor 23 that functions as a generator.

  The ECU 26 acquires the detection results of various sensors provided in the vehicle 11 as vehicle information indicating the traveling state of the vehicle 11 or the driver's request, and the motor 23 and the electronic control coupling 24 according to the acquired vehicle information. To control each. The sensors include a wheel speed sensor 31, a vehicle speed sensor 32, an accelerator pedal sensor 33, and a brake pedal sensor 34 provided on each wheel. Through these sensors, the ECU 26 detects the rotational speed (wheel speed) Vw of each wheel, the vehicle speed V that is the traveling speed of the vehicle 11, the accelerator pedal depression amount Pa, and the brake pedal depression amount Pb as vehicle information.

  The ECU 26 maintains the transmission torque of the electronic control coupling 24 at 100% when the vehicle 11 is in a normal traveling state (forward, reverse). The ECU 26 controls the driving force transmitted to the rear wheels 28 and 28 by controlling the rotation of the motor 23 according to the traveling state of the vehicle 11 (normal four-wheel drive control). Unlike the internal combustion engine 12, when the vehicle 11 travels (forwards and reverses), the driving force generated by the motor 23 is transmitted to the left and right rear wheels 28 and 28 in an auxiliary manner.

  The ECU 26 constantly monitors the voltage of the storage battery 21 through the voltage sensor 35 provided in the storage battery 21 and detects the charge amount (remaining amount) of the storage battery 21 based on the voltage. The ECU 26 stops power supply to the motor 23 as control for performing regenerative power generation by the motor 23 when the charge amount of the storage battery 21 decreases. At this time, the ECU 26 sets the transmission torque of the electronic control coupling 24 in accordance with the traveling state of the vehicle 11 at that time. Through the control of the transmission torque, it is possible to control the amount of power generated by the motor 23 and thus the regenerative braking force.

<Power transmission control procedure>
Next, a power transmission control process procedure for the rear wheels will be described. The process is executed by the ECU 26. Note that the vehicle 11 is running, and the ECU 26 performs normal four-wheel drive control.

As shown in the flowchart of FIG. 2, the ECU 26 takes in the voltage of the storage battery 21 through the voltage sensor 35 (step S101).
Next, the ECU 26 determines based on the voltage of the storage battery 21 whether the remaining capacity of the storage battery 21 is reduced, that is, whether the storage battery 21 needs to be charged (step S102).

Specifically, the ECU 26 determines whether or not the following condition (A) is satisfied.
-Charge amount (remaining amount) of the storage battery 21> threshold value X (%) (A)
Since there is a correlation between the voltage of the storage battery 21 and the charge amount, the charge amount can be estimated based on the voltage. The threshold value X for determining the charge amount is set, for example, based on the charge amount of the storage battery 21 when fully charged. Note that the necessity of charging may be determined through a comparison between the voltage of the storage battery 21 and a threshold value.

  When it is determined that charging of the storage battery 21 is not necessary, that is, when it is determined that the charge amount of the storage battery 21 exceeds the threshold value X (NO in step S102), the ECU 26 executes four-wheel drive control. (Step S103), and the process ends.

  When it is determined that the storage battery 21 needs to be charged, that is, when it is determined that the charge amount of the storage battery 21 does not exceed the threshold value X (YES in step S102), the ECU 26 proceeds to step S104. Transition.

  In step S104, the ECU 26 determines whether it is necessary to drive the four wheels. Specifically, the ECU 26 determines whether at least one of the following two conditions (B1) and (B2) is satisfied.

-Wheel speed difference before and after> threshold value Vw1 (B1)
・ Right wheel speed difference> threshold value Vw2 (B2)
Condition (B1) is for judging slip. When the difference between the front and rear wheel speeds is larger than the threshold value Vw1, it is determined that the vehicle 11 is slipping. The condition (B2) is for determining curve running. When the difference between the left and right wheel speeds is greater than the threshold value Vw2, it is determined that the vehicle 11 is traveling on a curved road.

  When it is determined that the four wheels need to be driven, specifically, when it is determined that at least one of the two conditions (B1) and (B2) is satisfied (YES in step S104), the ECU 26 first The process proceeds to step S103 to execute or continue the four-wheel drive control.

  In other words, even when the charge amount (voltage) of the storage battery 21 has dropped below the threshold value X, four-wheel drive performance such as when slipping or traveling on a curved road is required. In such a situation, priority is given to charging the storage battery 21 to ensure the running stability of the vehicle 11.

  When it is determined that it is not necessary to drive the four wheels, specifically, when it is determined that neither of the two conditional expressions (B1) and (B2) is satisfied (NO in step S104), the ECU 26 The wheel drive control is stopped (step S105). That is, the ECU 26 stops power supply to the motor 23 in order to charge the storage battery 21. When the motor 23 is stopped, the vehicle 11 enters the front wheel drive state.

  Thereafter, the ECU 26 controls the transmission torque of the electronic control coupling 24 in accordance with the traveling state of the vehicle 11. This is because regenerative power generation (charging of the storage battery 21) according to the traveling state of the vehicle 11 is performed. Specifically, the ECU 26 controls the transmission torque of the electronic control coupling 24 as follows.

  That is, after stopping the four-wheel drive control in the previous step S105, the ECU 26 determines whether or not the current traveling state of the vehicle 11 is a steady traveling state (first traveling state) (step S106). The steady running state refers to a state where the vehicle is running at a constant vehicle speed on an expressway or the like. Specifically, the ECU 26 determines whether or not the following condition (C) is satisfied.

・ Change amount of vehicle speed per unit time (speed change) <threshold value ΔV (C)
The ECU 26 determines that the vehicle 11 is in a steady running state when the amount of change in vehicle speed per unit time is smaller than the threshold value ΔV.

  When the ECU 26 determines that the traveling state of the vehicle 11 is the first traveling state, specifically, when it is determined that the condition (C) is satisfied (YES in step S106), the electronic control coupling 24 is activated. Is set to the set value α1 (step S107), and the process is terminated.

  The set value α1 is set to a small value of about 5% to 10%, for example. This is based on the viewpoint of reducing the impact caused by the rotational force of the rear wheels 28 and 28 being transmitted to the motor 23 when power generation is started in the steady running state. By setting the transmission torque of the electronically controlled coupling 24 to a smaller value, an impact when the rear wheel rotational force starts to be transmitted to the motor 23 via the electronically controlled coupling 24 (braking force generated with regenerative power generation) The occurrence of a sudden braking phenomenon caused by the Thereby, the riding comfort of the vehicle 11 is also ensured.

  When it is determined that the traveling state of the vehicle 11 is not the first traveling state, specifically, when it is determined that the condition (C) is not satisfied (NO in step S106), the ECU 26 proceeds to step S108. To do.

  In step S108, the ECU 26 determines whether or not the current traveling state of the vehicle 11 is traveling on a downhill (second traveling state). Specifically, the ECU 26 determines whether or not the following two conditions (D1) and (D2) are satisfied.

-Depressing the accelerator pedal (accelerator off) ... (D1)
・ Vehicle speed> threshold value Vh1 ………………………………………………… (D2)
When the vehicle speed is maintained at a certain speed in the accelerator-off state, the vehicle 11 is considered to be down some slope.

  When it is determined that the traveling state of the vehicle 11 is the second traveling state, the ECU 26 specifically determines that both of the two conditions (D1) and (D2) are satisfied (in step S108). YES), the transmission torque of the electronic control coupling 24 is set to the set value α2 (step S109), and the process is terminated.

  The set value α2 is set to a value of about 30% to 50%, for example. However, when traveling on a long downhill, the set value α2 may be set to 100%. This is because it is preferable to generate a larger regenerative braking force as the downhill is longer.

  When it is determined that the traveling state of the vehicle 11 is not the second traveling state, the ECU 26 specifically determines that at least one of the two conditions (D1) and (D2) is not satisfied (in step S108). NO), the process proceeds to step S110.

  In step S110, the ECU 26 determines whether or not the current traveling state of the vehicle 11 is a decelerating traveling state (third traveling state) according to the driver's intention. Specifically, the ECU 26 determines whether or not the following two conditions (E1) and (E2) are satisfied.

・ The brake pedal is depressed (brake on) ... (E1)
・ Vehicle speed> threshold Vh2 …………………………………………… (E2)
However, threshold value Vh2 is set to a value smaller than threshold value Vh2 in the previous condition (D2), for example, 0 km / h.

  When it is determined that the traveling state of the vehicle 11 is the third traveling state, the ECU 26 specifically determines that both of the two conditions (E1) and (E2) are satisfied (in step S110). YES), the transmission torque of the electronic control coupling 24 is set to the set value α3 (step S111), and the process is terminated.

  The set value α3 is set to a value of about 50% to 100%, for example. When the amount of depression of the brake pedal is large, the set value α3 may be set to 100% because the driver's intention to stop is strong.

  However, it is preferable that the transmission torque of the electronic control coupling 24 is gradually increased instead of increasing rapidly from the current value to the set value α3. This is to reduce an impact caused by a sudden change in the rotational force (torque) of the rear wheels 28 and 28 transmitted to the motor 23. The same applies when the transmission torque is changed from the current value to the set values α1 and α2 in the previous steps 107 and S109.

  When it is determined that the traveling state of the vehicle 11 is not the third traveling state, the ECU 26 specifically determines that at least one of the two conditions (E1) and (E2) is not satisfied (in step S110). NO), the process is terminated.

  When the electric power generated by the motor 23 is supplied to the storage battery 21, the storage battery 21 is charged. Eventually, when the charge amount of the storage battery 21 recovers to an extent that exceeds the threshold value X (YES in step S102), the ECU 26 executes four-wheel drive control. This four-wheel drive control includes the following processing.

  That is, the ECU 26 first sets the transmission torque of the electronic control coupling 24 to 0%. Thereby, when the regenerative power generation by the motor 23 is performed before the execution of the four-wheel drive control, the regenerative power generation is stopped. Next, when the depression of the accelerator pedal (accelerator on) is detected, the ECU 26 sets the transmission torque of the electronic control coupling 24 to 100%. Thereafter, the ECU 26 controls the driving force transmitted to the rear wheels 28, 28 by controlling the rotation of the motor 23.

<Effect of Embodiment>
Therefore, according to the present embodiment, the following effects can be obtained.
(1) When the amount of charge of the storage battery 21 decreases below the threshold value X during traveling of the vehicle and when the vehicle is in a traveling state where the four-wheel drive performance is not necessarily required, power generation by the motor 23 is started. When the charge amount of the storage battery 21 is recovered, the power generation by the motor 23 is terminated. By performing more appropriate regenerative power generation according to the charge amount of the storage battery 21, it is possible to suppress generation of useless surplus power by the motor 23. Moreover, since the excessive charge of the storage battery 21 is also suppressed, the maintenance life improvement of the product life of the storage battery 21 is achieved.

  (2) Here, as the rotational force transmitted to the motor 23 increases, the amount of power generated by the motor 23 increases. At this time, not only the power generation amount but also the regenerative braking force by the motor 23 increases. For this reason, depending on the traveling state of the vehicle 11, the driver may feel a slight impact due to the regenerative braking force by the motor 23. Therefore, as in this example, when power generation by the motor 23 is started, if the transmission torque of the electronic control coupling 24 is set to a different value (α1, α2, α3) according to the traveling state of the vehicle 11, More appropriate regenerative power generation is performed according to the running state. Further, since it is possible to generate a more appropriate regenerative braking force according to the traveling state of the vehicle, the riding comfort of the vehicle is also ensured.

  (3) When the ECU 26 starts power generation by the motor 23, when setting the transmission torque of the electronic control coupling 24, the ECU 26 gradually changes from the transmission torque before the setting to a specific set value (α1, α2, α3). Let In this way, it is possible to reduce an impact caused by a sudden change in the transmission torque of the electronic control coupling 24. The greater the difference between the transmission torque before setting and the target setting values (α1, α2, α3), the more effective.

  (4) Even when a decrease in the remaining amount of the storage battery 21 is detected, when the vehicle is in a traveling state where four-wheel drive is required, the four-wheel drive traveling is prioritized over the charging of the storage battery. Thereby, the running stability of the vehicle 11 can be continuously secured.

  (5) By controlling the transmission torque of the electronic control coupling 24, the torque transmitted from the motor 23 to the rear wheels 28, 28 can be controlled. For this reason, a highly accurate motor is unnecessary.

  (6) A shunt DC machine is employed as the motor 23. During power generation (regeneration), for example, it is possible to control the power generation amount of the motor 23 by controlling the field current. In this case, however, it is necessary to provide a configuration such as a circuit for controlling the field current. . In this regard, in this example, the power generation amount of the motor 23 can be controlled through adjustment of the transmission torque of the electronic control coupling 24. Since it is not necessary to control the field current applied to the motor 23, a configuration such as a circuit for controlling the field current is unnecessary.

<Second Embodiment>
Next, a second embodiment of the power transmission device will be described. The power transmission device of this example basically has the same configuration as the power transmission device shown in FIG. 1, and is the first embodiment in terms of the processing procedure of power transmission control by the ECU. And different.

  The processing procedure of the power transmission control of this example is as shown in the flowchart of FIG. Since each process of step S101 to step S103 in the flowchart is the same as that of the first embodiment, a detailed description thereof will be omitted.

  Now, as shown in the flowchart of FIG. 3, the ECU 26 determines that charging of the storage battery 21 is necessary, that is, determines that the charge amount of the storage battery 21 does not exceed the threshold value X ( If YES in step S102, the four-wheel drive control is stopped (step S201). Thereafter, the ECU 26 controls the transmission torque of the electronic control coupling 24 in accordance with the traveling state of the vehicle 11 (step S202).

However, the processing content of step S202 may include at least one of the following three processing groups with “·” at the beginning of the sentence.
A series of processes for determining the first traveling state (steady traveling) and controlling the transmission torque of the electronically controlled coupling 24 in accordance with the determined traveling state (FIG. 2: S106, S107).

A series of processes for determining the second traveling state (downhill traveling) and controlling the transmission torque of the electronic control coupling 24 in accordance with the determined traveling state (FIG. 2: S108, S109).
A series of processes for determining the third traveling state (decelerated traveling) and controlling the transmission torque of the electronically controlled coupling 24 according to the determined traveling state (FIG. 2: S110, S111).

Therefore, according to the present embodiment, the same effects as (1) to (3), (5), and (6) in the first embodiment can be obtained.
(7) Moreover, in this example, when the charge amount of the storage battery 21 does not reach the threshold value X, the storage battery 21 is always charged according to the traveling state of the vehicle 11 regardless of whether the four-wheel drive is necessary. For this reason, it is suitable when it is desired to prioritize charging of the storage battery 21 over four-wheel drive.

<Third Embodiment>
Next, a third embodiment of the power transmission device will be described. This example is different from the first embodiment in that the left and right rear wheels are driven by two independent motors.

  As shown in FIG. 4, the power transmission device 22 has two motors 23a and 23b, two electronic control couplings 24a and 24b, and an ECU 26, which are auxiliary driving sources for traveling. The two motors 23a and 23b are connected to the left and right rear wheels 28 and 28 via electronic control couplings 24a and 24b, respectively. The driving forces of the two motors 23a and 23b are transmitted to the two rear wheels 28 and 28 via the electronic control couplings 24a and 24 corresponding to the motors 23a and 23b, respectively.

  The ECU 26 controls the two motors 23a and 23b and the two electronic control couplings 24a and 24, respectively. The ECU 26 basically executes power transmission control for the two rear wheels 28 and 28 in the same procedure as that shown in the flowchart of FIG. 2 or FIG. When the charge amount of the storage battery 21 does not reach the threshold value X, the ECU 26 stops the motor 23 and controls the transmission torque of the electronic control coupling 24 according to the traveling state of the vehicle 11. Thereby, regenerative charging of the storage battery 21 is performed according to the running state of the vehicle 11. Further, a regenerative braking force according to the traveling state of the vehicle is exhibited.

Therefore, according to the present embodiment, it is possible to obtain the same effects as (1) to (6) of the first embodiment or the same effects as (7) of the second embodiment.
<Other embodiments>
Each embodiment may be modified as follows.

  In the second embodiment, during regenerative charging, the transmission torque of the electronic control coupling 24 is set according to at least one of the first to third traveling states. The same applies to the first and third embodiments.

  In the first to third embodiments, when regenerative power generation is performed by the motor 23 (FIG. 2: S107, S109, S110, FIG. 3: S202), the transmission torque of the electronically controlled coupling 24 is based only on the vehicle speed V. You may make it set. Since the rotational force of the rear wheels 28 and 28 changes depending on the vehicle speed, even if the transmission torque is set based only on the vehicle speed, depending on the driving state of the vehicle 11 at that time (for example, low speed driving, medium speed driving, high speed driving). Thus, a more appropriate regenerative braking force can be generated.

  In the first or second embodiment, the single electronic control coupling 24 is provided between the motor 23 and the rear differential gear 25. However, the following may be used. For example, electronic control couplings 24 are provided between the rear differential gear 25 and one rear wheel 28, and between the rear differential gear 25 and the other rear wheel 28, respectively. Even in this case, regenerative power generation according to the traveling state of the vehicle 11 can be performed through control of the transmission torque of the electronic control coupling 24. Further, a more appropriate regenerative braking force according to the traveling state of the vehicle 11 is exhibited.

  In the first to third embodiments, the vehicle 11 having the internal combustion engine 12 is illustrated as a drive source for the front wheels 16 and 16 that are the main drive wheels, but an electric motor (motor) is mounted instead of the internal combustion engine 12. It may be a vehicle.

  In the first to third embodiments, the vehicle 11 is illustrated in which the front wheels 16 and 16 are main drive wheels and the rear wheels 28 and 28 are auxiliary drive wheels. However, the rear wheels 28 and 28 are main drive wheels and front wheels. A vehicle having 16 and 16 as auxiliary drive wheels may be used.

  DESCRIPTION OF SYMBOLS 11 ... Vehicle (four-wheel drive vehicle), 16 ... Front wheel (main drive wheel), 21 ... Storage battery, 22 ... Power transmission device, 23 ... Motor, 23a ... Motor (first motor), 23b ... Motor (second motor) Motor), 24 ... electronically controlled coupling, 24a ... electronically controlled coupling (first coupling), 24b ... electronically controlled coupling (second coupling), 25 ... rear differential gear (differential mechanism), 26 ... ECU (control device), 28 ... Rear wheels (sub-drive wheels).

Claims (8)

In a power transmission device for transmitting power to the auxiliary drive wheels of a four-wheel drive vehicle having left and right main drive wheels to which power is always transmitted and left and right auxiliary drive wheels to which power is transmitted according to a traveling state,
The power transmitted from the in-vehicle storage battery is consumed and rotated to generate the power transmitted to the auxiliary drive wheel, while the power supply is stopped while rotating in conjunction with the auxiliary drive wheel A motor for generating electric power regenerated by the storage battery;
A coupling for continuously changing a power transmission rate between the motor and the auxiliary drive wheel between 0% and 100% through electronic control;
A controller for controlling the motor and the coupling, respectively,
The control device stops power supply to the motor and sets the power transmission rate to a value larger than 0% when the remaining amount of the storage battery falls below a predetermined threshold value while the vehicle is running. While power generation by the motor is started by setting, when the remaining amount of the storage battery recovers beyond a predetermined threshold value, power generation by the motor is terminated by setting the power transmission rate to 0% Power transmission device. The power transmission device according to claim 1,
The power transmission device, which is set when the power generation by the motor is started, is set to a different value according to the traveling state of the vehicle. In the power transmission device according to claim 1 or 2,
When the power transmission rate is set when starting the power generation by the motor, the control device gradually changes the power transmission rate before the setting to the power transmission rate after the setting. In the power transmission device according to any one of claims 1 to 3,
Even when the remaining amount of the storage battery has fallen below a predetermined threshold value, the control device detects the left and right subordinates through the control of the motor when a running state that requires four-wheel drive is detected. A power transmission device that drives drive wheels. The power transmission device according to claim 4,
The said control apparatus is a power transmission device which detects the driving | running | working state in which four-wheel drive is required based on at least one of the wheel speed difference before and behind, and the wheel speed difference between right and left. In the power transmission device according to any one of claims 1 to 5,
A differential mechanism that distributes the power of the motor to the left and right auxiliary drive wheels;
The coupling is a power transmission device provided between the motor and the differential mechanism. In the power transmission device according to any one of claims 1 to 5,
The motor includes first and second motors, and the first and second motors are coupled to the left and right auxiliary drive wheels via the couplings, respectively. In the power transmission device according to any one of claims 2 to 7,
The traveling state of the vehicle includes at least one of a first traveling state traveling at a constant speed, a second traveling state traveling inertial on a downhill, and a third traveling state decelerating by a brake,
The control device determines the first traveling state based on the vehicle speed, the second traveling state based on the vehicle speed and the operating state of the accelerator, and the power for determining the third traveling state based on the vehicle speed and the operating state of the brake. Transmission device.