JP2010228689A - Controller of hybrid four-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of a hybrid four-wheel drive vehicle capable of enhancing the steerability and the safety of the vehicle. <P>SOLUTION: The time difference is set between the power increasing timing of a front wheel 5 to be driven by an engine 2 and the power increasing timing of a rear wheel 9 to be driven by a motor generator 6 during the accelerated turn of a hybrid four-wheel drive vehicle 1. In other words, by providing the time difference in the power increasing timing of both wheels, the yaw rate is increased when the accelerated turn of the vehicle is started, and the turning property is enhanced, and as a result, the steerability and the safety of the hybrid four-wheel drive vehicle 1 during the accelerated turn can be enhanced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technology related to a control device for a hybrid four-wheel drive vehicle, typically to a control technology for improving the maneuverability and stability of a vehicle.

  Background art related to a hybrid four-wheel drive vehicle is disclosed in, for example, Patent Documents 1 and 2. Patent Document 1 discloses a technique for improving the operability by adjusting the regenerative braking force of a second drive wheel driven by an electric motor. Patent Document 2 discloses a technique for switching a pattern for allocating a driving force according to a vehicle speed and an accelerator operation amount according to a state of charge of a storage battery.

Japanese Patent Laying-Open No. 2005-304182 JP-A-9-284911

  In recent years, hybrid four-wheel drive vehicles in which one of the front and rear wheels is driven by an engine that is an internal combustion engine and the other of the front and rear wheels is driven by an electric motor have become widespread. A hybrid four-wheel drive vehicle can improve fuel efficiency and reduce exhaust gas, and has better vehicle handling and stability than a two-wheel drive vehicle. Recently, it has been desired to provide a hybrid four-wheel drive vehicle with better vehicle maneuverability and stability than the background art. One possible solution to this demand is to improve the controllability and stability of the vehicle during accelerated turning by appropriately controlling the front and rear drive force distribution.

  In the technique disclosed in Patent Document 1, only deceleration turning is considered, and is not considered until acceleration turning. In addition, as in the technique disclosed in Patent Document 2, when the driving state of the front and rear wheels is switched based on the information on the state of charge of the storage battery, the control and stability of the vehicle not intended by the driver is obtained. It is possible to give an uncomfortable feeling.

  One representative aspect of the present invention provides a control device for a hybrid four-wheel drive vehicle that can improve the maneuverability and stability of the vehicle.

  Here, one of the representative aspects of the present invention is that the power increase timing of the first driving wheel driven by the first power source and the second driving wheel driven by the second power source during acceleration turning of the vehicle. A time difference is provided between the power increase timing and the power increase timing.

  If a time difference is provided in the power increase timings of both wheels as in a representative aspect of the present invention, the yaw rate at the start of acceleration turning of the vehicle is increased and the turning performance is improved.

  As a result, according to one of the representative aspects of the present invention, the maneuverability and stability of the vehicle can be improved.

The top view which shows the structure of the drive system of the hybrid four-wheel drive vehicle which is 1st Example of this invention. The block diagram which shows the input-output relationship of the signal with the engine control apparatus, motor control apparatus, each sensor, etc. which are mounted in the hybrid four-wheel drive vehicle of FIG. The model figure (refer (a)) which shows the two-wheel model of the front-and-rear wheel of a vehicle, and the steering characteristic figure which shows the relationship between the driving force of a front-and-rear wheel and a steer. The flowchart which shows the arithmetic processing of the control apparatus mounted in the hybrid four-wheel drive vehicle of FIG. The flowchart which shows the arithmetic processing of the control apparatus mounted in the hybrid four-wheel drive vehicle of FIG. The time chart which shows the operation | movement of the hybrid four-wheel drive vehicle of FIG. FIG. 5 is a diagram for explaining an effect obtained by executing the control of the first embodiment, and is a vehicle locus diagram showing an operating state of the hybrid four-wheel drive vehicle of FIG. 1. The flowchart which shows the arithmetic processing of the control apparatus of the hybrid four-wheel drive vehicle which is 2nd Example of this invention. FIG. 10 is a diagram illustrating an effect of executing the control of the second embodiment, and is a vehicle locus diagram illustrating an operating state of the hybrid four-wheel drive vehicle. FIG. 10 is a diagram illustrating an effect of executing the control of the second embodiment, and is a vehicle locus diagram illustrating an operating state of the hybrid four-wheel drive vehicle.

  Embodiments of the present invention will be described below with reference to the drawings.

  A first embodiment of the present invention will be described with reference to FIGS.

  First, the configuration of the drive system of the hybrid four-wheel drive vehicle will be described with reference to FIG.

  As shown in FIG. 1, a hybrid four-wheel drive vehicle 1 includes an engine 2 and a transaxle 3 (an integrated device of a transmission and a differential gear (differential gear)) disposed on the front side of a vehicle body. A rear wheel differential (differential gear) 7 is disposed on the rear side of the vehicle.

  The rotational power of the engine 2 is transmitted to the front wheels 5 via the transaxle 3 and the front wheel drive shaft 4. Thereby, the front wheel 5 is always driven.

  In this embodiment, a case where a gasoline engine is used as the engine 2 will be described as an example. As the engine 2, another engine such as a diesel engine, a hydrogen engine, a gas engine, or a biofuel engine may be used.

  The rotational power of the motor generator 6 is transmitted to the rear wheel 9 via the rear wheel speed reducer 18, the rear wheel differential 7 and the rear wheel drive shaft 8. As a result, the rear wheel 9 is driven as necessary, that is, when assisting the front wheel 5 or during EV travel. A clutch 12 is disposed between the motor generator 6 and the rear wheel speed reducer 18. Although the clutch 12 is normally engaged, the power transmission between the motor generator 6 and the rear wheel differential device 7 can be cut off by opening.

  In the present embodiment, a configuration in which the clutch 12 and the rear wheel speed reducer 18 are disposed between the motor generator 6 and the rear wheel differential 7 will be described as an example. The configuration for transmitting the rotational power of the motor generator 6 may be a configuration in which the rotational power of the motor generator 6 is directly input to the rear wheel differential device 7 via the clutch 12 without the reduction gear 18. The motor generator 6 and the speed reducer 18 may be directly connected without the clutch 12.

  In the present embodiment, the motor generator 6 is a three-phase AC synchronous machine, for example, a permanent magnet field type three-phase AC synchronous machine constituted by a field provided with an armature that generates a rotating magnetic field and a permanent magnet. The case where it is used will be described as an example. As the motor generator 6, a three-phase AC induction machine or a DC machine may be used. In addition, as the three-phase AC synchronous machine, a wound field type three-phase AC synchronous machine constituted by an armature that generates a rotating magnetic field and a field provided with a field winding may be used.

  A power storage device 11 is electrically connected to the winding wound around the armature of the motor generator 6 via the inverter device 10. The power storage device 11 is a DC power source for driving the motor generator 6, and has a higher voltage than a battery for in-vehicle auxiliary equipment (nominal output voltage 12 volts) that is a DC power source for driving in-vehicle electrical components (lights, radios, etc.) The nominal output voltage is 36 volts or more, for example, 300 to 400 volts), for example, a lithium ion battery or a nickel metal hydride battery.

  In the present embodiment, a case where the power storage device 11 is configured by a high voltage battery having a nominal output voltage of 36 volts or more will be described as an example. As the power storage device 11, a large capacity capacitor or a capacitor may be used.

  The inverter device 10 includes a power conversion circuit, and performs power conversion from DC power to three-phase AC power and power conversion from three-phase AC power to DC power between the armature of the motor generator 6 and the power storage device 11. It is a power converter. In the power conversion circuit, a series circuit for one phase in which two switching semiconductor elements are electrically connected in series is electrically connected in parallel to the DC positive and negative electrodes of the power storage device 11 for three phases. It is configured. A winding of a corresponding phase of the armature of the motor generator 6 is electrically connected to the middle point of each series circuit.

  In the present embodiment, an example in which an insulated gate bipolar transistor (IGBT) is used as the six switching semiconductor elements for power conversion will be described. As the switching semiconductor element, a metal oxide semiconductor field effect transistor (MOSFET) may be used.

  The operation of the engine 2 is controlled by an engine control device (not shown). The engine control device outputs a command signal to an engine component device (such as an air throttle valve, an intake / exhaust valve, or a fuel injection valve) to control driving of the engine component device. As a result, the amount of air, fuel, etc. supplied to the engine 2 are controlled, and the rotational power output from the engine 2 is controlled.

  The operation of the motor generator 6 is controlled by a motor control device 12. The motor control device 12 outputs a drive command signal to the inverter device 10 to control driving of the inverter device 10 (switching (on / off operation) of the switching semiconductor element). As a result, the electric power between the armature of motor generator 6 and power storage device 11 is controlled, the rotational power output from motor generator 6 is controlled, and the power generation by motor generator 6 is controlled.

  When the DC power supplied from the power storage device 11 is converted into three-phase AC power by the inverter device 10 and supplied to the armature of the motor generator 6, the motor generator 6 operates as a power running operation, that is, as an electric motor, and rotates power. appear. The generated rotational power is transmitted to the rear wheel 9 through the power transmission path described above. As a result, driving assist for the front wheels 5 driven by the engine 2 and driving of the vehicle by the power of only the motor generator 6 are possible.

  On the other hand, when the motor generator 6 is driven by power from the rear wheel 9, the motor generator 6 operates as a regenerative (power generation) operation, that is, as a generator, and generates three-phase AC power. The generated three-phase AC power is converted into DC power by the inverter device 10 and supplied to the power storage device 11. Thereby, the electrical storage of the electrical storage apparatus 11 and regenerative braking are possible.

  Next, the configuration of the motor control device 12 will be described with reference to FIG.

  As shown in FIG. 2, the motor control device 12 receives a plurality of signals corresponding to a plurality of input information necessary for controlling the motor generator 6. The plurality of input information includes, for example, an output signal of the accelerator pedal sensor 20 (which may be the opening of the air throttle valve of the engine 2), an output signal of the handle angle sensor 21, and an output signal of the brake pedal switch 22 (even the brake pedal depression amount) Good), wheel speed sensor 23 (for all four wheels), longitudinal acceleration sensor 24, lateral acceleration sensor 25, yaw rate sensor 26, shift lever position sensor 27, parking brake switch 28, battery output from battery controller of power storage device 11 State information 29 (for example, charge state (SOC) information, allowable charge / discharge amount information, deterioration state (SOH) information, etc.), current sensor 30 (detects a three-phase alternating current flowing between the motor generator 6 and the inverter device 10) , Motor rotation position sensor 31 (detects the rotation position of the motor generator 6, for example Magnetic pole position of such a resolver sensor), and the like.

  The motor control device 12 is electrically connected to other control devices including the engine control device 32 through a communication network, and can transmit / receive information to / from other control devices by signal transmission. A plurality of pieces of input information input to the motor control device 12 are directly input from each sensor, or are signal-transmitted via a communication network.

  The motor control device 12 is configured by mounting a plurality of electronic components including a microcomputer as a semiconductor device and a storage device on an electronic circuit board and electrically connecting them. The microcomputer is an arithmetic processing unit that operates according to a predetermined program, and includes a motor generator control unit configured by software.

  The motor generator control unit outputs a drive command signal for turning on and off the switching semiconductor element of the inverter device 10 to the inverter device 10 to control power conversion by the inverter device 10, thereby controlling the operation of the motor generator 6. Based on a plurality of input information including a torque command value for the motor generator 6, a magnetic pole position of the motor generator 6, and a three-phase AC current value between the inverter device 10 and the motor generator 6. A drive command value for turning on / off the switching semiconductor element is calculated, the drive command value is used as output information, and a signal (for example, PWM (pulse width modulation) signal) corresponding to the drive command value is input to the drive circuit of the inverter device 10. Output. The drive circuit of the inverter device 10 outputs the received drive command signal to the gate electrode of the switching semiconductor element as a drive signal input to the gate electrode of the switching semiconductor element. Thereby, ON / OFF of the six switching semiconductor elements is individually controlled, and power conversion is performed.

  Next, the drive control operation of the vehicle will be described.

  First, with reference to FIG. 3, a description will be given of the two-wheel model of the front and rear wheels of the vehicle (see (a)) and the relationship between the driving force of the front and rear wheels and the steering characteristics (see (b)).

  In FIG. 3 (a), W is the vehicle weight, Wf is the front wheel load, Wr is the rear wheel load, L is the wheelbase, Lf is the distance from the center of gravity to the front wheel axis, and Lr is from the center of gravity. Distance between rear axles, Hg is height of center of gravity, Fxf is front wheel drive force, Fxr is rear wheel drive force, Fyf is front wheel saturation lateral force, Fyr is rear wheel saturation lateral force, Mz is turning direction The moments around the center of gravity when each is positive are shown.

  The vector sum of the driving force and lateral force becomes the tire generating force at each wheel. When a certain driving force is generated, the maximum lateral force when the so-called friction circle is used to the maximum is a saturated lateral force.

  The moment around the center of gravity is obtained from equation (1).

    Mz = Fyf × Lf−Fyr × Lr (1)

  If the moment Mz around the center of gravity is 0, there is no rotation of the vehicle, so it is neutral steer. If Mz is a negative value, the motor rotates in the direction opposite to the turning direction, and therefore understeer. If Mz is a positive value, the vehicle rotates in the turning direction, and thus oversteer.

  For example, consider a vehicle with W = 15000 [N], L = 2500 [mm], Lf = 1000 [mm], Lr = 1500 [mm], and Hg = 450 [mm].

  Static longitudinal load distribution is obtained from the balance equation (2) of moments before and after the center of gravity.

Wf × Lf / L = Wr × Lr / L (2)
Wf × 1000/2500 = Wr × 1500/2500
Wf × 0.4 = Wr × 0.6
Wf: Wr = 0.6: 0.4
Wf: Wr = 15000 × 0.6: 15000 × 0.4
Wf: Wr = 9000 [N]: 6000 [N]

  That is, the static longitudinal load distribution is 9000 [N]: 6000 [N] of 60:40.

  Here, when the vehicle makes an acceleration turn with a longitudinal acceleration Gx = 0.25 [G], the moving load ΔW before and after acceleration can be obtained from Equation (3).

ΔW = W × Gx × Hg / L (3)
ΔW = 15000 × 0.25 × 450/2500
= 675 [N]

  The front wheel load Wf (0.25) and the rear wheel load Wr (0.25) at this time are obtained from the equations (4) and (5).

Wf (0.25) = Wf−ΔW (4)
= 9000-675
= 8325 [N]
Wr (0.25) = Wr + ΔW (5)
= 6000 + 675
= 6675 [N]

  That is, assuming that the driving force at the longitudinal acceleration Gx = 1 [G] is 100, the maximum value of the vector sum of the longitudinal force and the lateral force when the longitudinal acceleration Gx = 0.25 [G], that is, the size of the friction circle. Here's what it looks like:

Wf (0.25) = 8325/15000 × 100
= 55.5 (6)
Wr (0.25) = 6675/15000 × 100
= 44.5 (7)

  Since the driving force when the longitudinal acceleration Gx is 0.25 [G] is 25 [%] of the driving force when the longitudinal acceleration Gx is 1 [G], the following relationship is associated with the longitudinal driving forces Fxf and Fxr. There is.

Fxf + Fxr = acceleration × 100
= 0.25 x 100
Fxf = 25−Fxr (8)
Fxr = 25−Fxf (9)

  Here, the neutral steering, that is, the driving forces Fx and Fxr before and after Mz = 0 are obtained from the equation (1) as follows.

Mz = Fyf × Lf−Fyr × Lr
0 = Fyf × 1000−Fyr × 1500
0 = 1000Fyf-1500Fyr
Fyf = 1.5 Fyr
Fyf: Fyr = 3: 2
Fyf ² : Fyr ² = 9: 4 (10)

  From the above results, the front and rear saturated lateral forces Fyf and Fyr are obtained. Here, since the vector sum of the longitudinal force and the saturation lateral force is the maximum tire generation force, the following results are obtained from (6) and (7).

Wf (0.25) ² = Fxf ² + Fyf ²
55.5 = Fxf ² + Fyf ²
Fyf ² = 55.5 ² -Fxf ² (11)
Wr (0.25) ² = Fxr ² + Fyr ²
44.5 = Fxr ² + Fyr ²
Fyr ² = 44.5 ² -Fxr ² (12)

  The following results are obtained from (9), (10), (11), and (12).

55.5 ² -Fxf ² : 44.5 ² -Fxr ² = 9: 4
4 (55.5 ² -Fxf ² ) = 9 (44.5 ² -Fxr ² )
4 × 55.5 ² −4Fxf ² = 9 × 44.5 ² −9Fxr ²
−4Fxf ² + 9Fxr ² −5501.25 = 0
−4Fxf ² +9 (25−Fxf) ² −5501.25 = 0
−4Fxf ² +9 (625-50Fxf + Fxf ² ) −5501.25 = 0
5Fxf ² -450Fxf + 123.756 = 0
Fxf = (450 ± √ {450 ² -4 × 5 × 123.75}) / (2 × 5)
Fxf = (450 ± √ {200025}) / 10
Fxf = 45 ± 44.724
Fxf ≒ 0.3
From Equation (8), Fxf ≦ 25
Fyr = 25−Fxf
= 24.7
Fxf: Fyr = 0.3: 24.7
≒ 1: 99

  From the above, it can be seen that in the acceleration turning with the longitudinal acceleration Gx = 0.25 [G], the vehicle is almost neutral with the rear wheel drive.

  A result obtained by performing the above-described calculation while changing the longitudinal acceleration is a neutral steer line shown in FIG. Neutral steer is on the neutral steer line. In the range below the neutral steer line, Mz becomes a negative value, resulting in an understeer state. In a range above the neutral steer line, Mz becomes a positive value, resulting in an oversteer state.

  Neutral steer is achieved by driving the front and rear wheels with the front / rear driving force distribution on the neutral steer line. However, the rear wheel 9 is driven by the motor generator 6. For this reason, the driving force of the rear wheel 9 is limited by the maximum output of the motor generator 6. That is, if neutral steering is to be realized in all traveling states, a motor generator 6 with a high output is required, which is not realistic.

  Thus, in this embodiment, the rear wheel driving force prevails in the early stage of acceleration turning, and the front wheel driving force gradually prevails, thereby gradually shifting from neutral steer to understeer and improving maneuverability and stability. .

  Next, calculation processing of the motor control device 12 will be described with reference to FIG.

  First, in step 100, the required driving force is calculated. The required driving force can be calculated, for example, by multiplying the accelerator depression amount by a coefficient. Thereafter, the process proceeds to step 101.

  In step 101, it is determined whether or not the charge amount of the power storage device is in a good state. For example, it is determined whether or not the charge amount is equal to or greater than a preset threshold value. If it is determined that the amount of charge is less than the threshold value, that is, it is not in a good state, the stored energy is insufficient, and the process proceeds to step 106. If it is determined that the amount of charge is equal to or greater than the threshold value, that is, in a good state, the stored energy is sufficient, and the process proceeds to step 102.

  In step 102, it is determined whether or not the vehicle is in a starting state. For example, the determination is made based on whether the vehicle speed is equal to or higher than a preset threshold value. If it is determined that the vehicle is in the starting state, the process proceeds to step 103. If it is determined that the vehicle is not running but running, the process proceeds to step 104.

  In step 104, the driving force of the rear wheel with respect to the required driving force is calculated. The calculation method in step 104 will be described later. Thereafter, the process proceeds to Step 107.

  In Step 107, the front wheel driving force is obtained by subtracting the rear wheel driving force calculated or set in the previous step from the required driving force. Thereafter, the process proceeds to step 108.

  In step 108, the rear wheel driving force calculated or set in the previous step is multiplied by the tire radius, and this is divided by the rear wheel total reduction ratio to obtain the driving torque of the motor generator 6. Thereafter, the process proceeds to step 109.

  In step 109, the front wheel driving force is multiplied by the tire radius, and this is divided by the front wheel total reduction ratio to obtain the engine torque torque.

  In step 106, the rear wheel driving force is set to zero. Thereafter, the process proceeds to Step 107.

  In step 103, it is determined whether or not the vehicle is in a turning state. For example, it is determined whether or not the value of the steering wheel angle is greater than or equal to a preset threshold value. If it is determined that the vehicle is not turning, the process proceeds to step 104. If it is determined that the vehicle is turning, the process proceeds to step 105.

  In step 105, the rear wheel driving force is calculated. Thereafter, the process proceeds to Step 107.

  Here, if the driving force of the rear wheels is large when turning at a place where the friction coefficient of the road surface is small, for example, at a crossing point of a snowy road, a spin tendency occurs and the vehicle becomes unstable. That is, in the turning start state, it can be said that it is better to suppress the rear wheel driving force than at the straight start. Accordingly, if it is determined in step 103 that the vehicle is in a turning state, the vehicle is in a turning start state, so the calculated value of the rear wheel driving force in step 105 is set lower than the calculated value of the rear wheel driving force in step 104. .

  Next, the rear wheel driving force setting method in step 107 will be described with reference to FIG.

  First, in step 200, the maximum rear wheel driving force is calculated. For example, a rear wheel total reduction ratio is added to the motor generator full load torque obtained by referring to a three-dimensional map (a data table indicating the relationship between the motor torque, the motor rotation speed, and the motor generator full load torque) indicating the motor generator full load torque. Calculate by multiplication. Thereafter, the process proceeds to Step 210.

  Here, the motor generator full load torque map is preferably set so as to change every moment according to various conditions (for example, electric energy that can be supplied by power storage device 11, temperature of inverter 10, temperature of motor generator 6, etc.). . In this way, even if the maximum torque and the maximum output are limited due to various conditions, there is no deficiency in the calculation.

  In step 201, a required rear wheel driving force with respect to the required driving force is calculated. For example, it is obtained with reference to a two-dimensional map (data table) showing the relationship between the requested driving force and the requested rear wheel driving force. Thereafter, the process proceeds to step 202.

  In step 202, a coefficient for subtracting the rear wheel driving force is set as time passes. Thereafter, the process proceeds to step 203.

  By setting the coefficient in step 202, the rear wheel driving force can be gradually reduced. The coefficient is set with reference to, for example, a two-dimensional map (data table) indicating the relationship between the timer time and the coefficient. The coefficient initially shows a maximum value. This maximum value continues for a predetermined time. After the maximum value continues for a predetermined time, the coefficient gradually decreases as time elapses.

  As shown in FIG. 5, the timer is reset every processing cycle. Actually, once set, the timer is not newly set unless it is cleared after a lapse of time.

  In step 203, the requested rear wheel driving force obtained in step 201 is compared with the maximum rear wheel driving force obtained in step 200. If it is determined that the requested rear wheel driving force is smaller than the maximum rear wheel driving force, the routine proceeds to step 204. If it is determined that the maximum rear wheel driving force is smaller than the required rear wheel driving force, the routine proceeds to step 205.

  In step 204, the requested rear wheel driving force is set to the rear wheel driving force. Thereafter, the process proceeds to step 206.

  In step 205, the maximum rear wheel driving force is set to the rear wheel driving force. Then, the process proceeds to step 206.

  In step 206, it is determined whether or not oversteer. For example, the actual yaw rate detected by the yaw rate sensor is compared with the target yaw rate calculated based on the steering wheel angle and the vehicle speed, and when the actual yaw rate is larger than the target yaw rate, it is determined that the vehicle is oversteered. If it is determined in step 206 that the vehicle is oversteered, the process proceeds to step 207. If it is determined in step 206 that it is not oversteer, the routine proceeds to step 208.

  In step 207, based on the coefficient obtained in step 202, the rear wheel driving force set in step 204 or step 205 is reduced. As described above, when it is determined that the vehicle is oversteering and the rear wheel driving force Fxr is decreased, the rear wheel saturation lateral force Fyr is increased, and Mz in Expression (1) is decreased, and the oversteer tendency is alleviated. . Thereafter, the process proceeds to Step 208.

  In step 208, for example, the turning direction is determined based on the steering wheel angle, and the wheel speeds of the left and right rear wheels are compared with a preset wheel speed threshold value. If it is determined in step 208 that the wheel speed of the turning outer wheel is higher than the wheel speed threshold, the process proceeds to step 209. If it is determined in step 208 that the wheel speed of the outer turning wheel is smaller than or equal to the wheel speed threshold, the rear wheel driving force setting process is terminated.

  In step 209, based on the coefficient obtained in step 202, the rear wheel driving force set in step 204, step 205, or step 207 is reduced. That is, the fact that the turning inner wheel of the rear wheel is significantly larger than the turning outer wheel can be determined that the turning inner wheel is on a low μ road and the yaw rate in the turning direction is increased. In such a case, when the rear wheel driving force Fxr is decreased, the rear wheel saturation lateral force Fyr is increased, and Mz in Expression (1) is decreased. As a result, a rapid increase in yaw rate is suppressed and maneuverability is improved.

  Next, the effect of the front and rear wheel drive control according to the present embodiment described above will be described based on a comparison with a conventional example with reference to FIGS.

  FIG. 6 shows respective changes over time of the steering angle, accelerator opening, rear wheel driving force, front wheel driving force, yaw rate, and longitudinal acceleration in order from the top.

  FIG. 6 shows an example in which steering is started from the time point (1) and acceleration is performed by stepping on the accelerator deeply at the same timing.

  In the conventional example, when the accelerator is stepped on, the front wheel driving force and the rear wheel driving force increase almost simultaneously, so the tendency to understeer from the start of the accelerator step is large, and the change in yaw rate is small. On the other hand, in the present embodiment, the rear wheel driving force first increases in accordance with the depression of the accelerator, and gradually decreases after a predetermined time (from around (2)). The front wheel driving force is small at the initial turning, and gradually increases according to the rear wheel driving force after a predetermined time (from around (2)). As a result, the understeer tendency is small at the beginning of the accelerator pedal, and the yaw rate changes greatly. As a result, in this embodiment, as shown in FIG. 7, the yaw rate at the initial stage of rotation is increased, and the trajectory on the inner side of the conventional example can be passed.

  A second embodiment of the present invention will be described with reference to FIGS.

  This embodiment is an improvement of the first embodiment, and is a speed difference sensitive type that generates a differential limiting force due to the speed difference between the left and right wheels of the rear wheel with respect to the rear wheel differential device 7 of the first embodiment. The difference from the first embodiment is that a differential limiting function is provided.

  Other configurations are the same as those of the first embodiment. The same components as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and the description thereof is omitted.

  First, consider a case where the turning inner wheel is a low μ road. As shown in FIG. 9, when the turning inner wheel becomes a low μ road, the speed of the rear turning inner wheel becomes significantly higher than the vehicle body speed. In the case of a comparative example equipped with a rear wheel actuating device having no differential limiting function, most of the rotational power of the motor generator flows to the low μ road side, and the driving force of the rear wheel becomes almost “0”, which tends to be understeered. . On the other hand, in the case of the present embodiment equipped with a rear wheel actuating device having a differential limiting function, the power on the low μ road side of the turning inner ring flows to the high μ road side of the turning outer ring and the driving force is exerted, and the driving force of the turning outer wheel is reduced. It becomes larger than the turning inner ring, and the understeer tendency is negated.

  Next, consider a case where the turning outer wheel is a low μ road. As shown in FIG. 10, when the turning outer wheel becomes a low μ road, the speed of the rear turning outer wheel becomes significantly larger than the vehicle body speed. In the case of a comparative example equipped with a rear wheel actuator that does not have a differential limiting function, most of the rotational power of the motor generator flows to the low μ road side, the driving force of the rear wheel becomes almost “0”, and the tendency to understeer become. On the other hand, in the case of the present embodiment in which the rear wheel actuating device having the differential limiting function is mounted, the power on the turning outer wheel low μ road side flows to the turning inner wheel high μ road side and the driving force is exhibited. However, in this case, since the driving force of the turning inner wheel is larger than that of the turning outer wheel, an understeer tendency becomes more prominent.

  For this reason, in this embodiment, when it is determined that the turning outer wheel is a low μ road, the rear wheel driving force is controlled to be reduced.

  Next, rear wheel driving force reduction control when it is determined that the turning outer wheel is a low μ road will be described with reference to FIG.

  In the present embodiment, step 210 for determining whether or not the turning outer wheel is a low μ road between steps 204 and 205 and step 206 of the flowchart shown in FIG. 5 of the first embodiment, and step If it is determined at 210 that the turning outer wheel is a low μ road, step 211 for reducing the rear wheel driving force set at step 204 or step 205 based on the coefficient set at step 202 is added. is doing. Whether or not the turning outer wheel is a low μ road is determined by, for example, determining the turning direction based on the steering wheel angle, comparing the wheel speeds of the left and right wheels of the rear wheel, and turning if the wheel speed difference is greater than a preset threshold value. The outer ring can be judged as a low μ road.

  According to the embodiment described above, when the turning outer wheel is determined to be a low μ road, the rear wheel driving force is reduced to reduce the driving force of the rear wheel in the turning, so the turning direction around the center of gravity The moment opposite to that becomes smaller and the understeer tendency is relieved.

Claims (3)

The first drive wheel on one side of the front and rear wheels is driven by the power output from the first power source, and the second drive wheel on the other side of the front and rear wheels is driven by the power output from the second power source. A control device mounted on a driving hybrid four-wheel drive vehicle,
A time difference is provided between an increase timing of power supplied to the first drive wheel and an increase timing of power supplied to the second drive wheel during acceleration turning of the vehicle;
A control device for a hybrid four-wheel drive vehicle. The control device for a hybrid four-wheel drive vehicle according to claim 1,
The hybrid four-wheel drive vehicle includes a differential device that distributes the power output from the second power source to the left and right wheels between the left and right wheels of the second drive wheel,
The differential device is a differential device with a speed difference-sensitive differential limiting function that generates a differential limiting force due to a speed difference between the left and right wheels.
A control device for a hybrid four-wheel drive vehicle. In the control device for a hybrid four-wheel drive vehicle according to claim 1 or 2,
When the yaw stability of the vehicle is detected and determined to be unstable, the power supplied to the second drive wheel is adjusted.
A control device for a hybrid four-wheel drive vehicle.

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