JP2009214805A - Driving force control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively utilize the driving force of front and rear wheels when a vehicle starts. <P>SOLUTION: The driving force control device of a vehicle detects roll back of a vehicle (step S502), and when detecting a start operation (step S504), restricts the increase of the driving forces of front wheels and rear wheels (step S505). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle driving force control apparatus that drives a generator with an internal combustion engine (engine) that drives a main drive shaft, and drives a motor with the generator to realize a four-wheel drive state.

Patent Document 1 discloses a conventional front and rear wheel in which a road surface gradient is detected by a road surface gradient detection device, and a rear wheel is driven by a motor to assist (assist) driving before a front wheel driven by an engine slips when starting. A drive vehicle control device is disclosed.
JP 2000-79828 A

However, in the prior art, there is a problem that the front wheels actually slip because the assist driving of the rear wheels is intervened in order to facilitate starting. That is, there is a problem that the driving force of the front and rear wheels at the time of starting is not effectively utilized such that the front wheels slip while the rear wheels are assisted.
The subject of this invention is enabling it to utilize the driving force of the front-and-rear wheel at the time of start effectively.

  In order to solve the above-described problems, the present invention limits the increase in the driving force of the main drive wheel according to the accelerator operation state when the vehicle rollback is detected and the vehicle start operation is detected. As assist control of the main drive wheel by the drive wheel, control is performed so that the output torque of the motor becomes the target motor torque command value.

  According to the present invention, by limiting the increase in the driving force of the main drive wheel according to the accelerator operation state, the main drive wheel slips during the assist control of the drive of the main drive wheel by the slave drive wheel. Can be prevented. Thus, according to the present invention, the driving force of the front and rear wheels when starting can be effectively utilized.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.
(Constitution)
The present embodiment is a vehicle to which the present invention is applied.
FIG. 1 is a diagram illustrating a system configuration of a vehicle according to the present embodiment.
As shown in FIG. 1, in the vehicle of the present embodiment, left and right front wheels 1L and 1R are main drive wheels driven by an engine 2 that is an internal combustion engine, and left and right rear wheels 3L and 3R can be driven by a motor 4. Is a secondary driven wheel. The output torque Te of the engine 2 is transmitted to the left and right front wheels 1L and 1R through the transmission 30 and the difference gear 31.

The transmission 30 includes shift position detection means 32 that detects the current shift range. The shift position detector 32 outputs the detected shift position signal to the 4WD controller 8.
The transmission 30 performs a shift operation based on a shift command from a shift control unit (not shown). For example, the shift control unit has a shift shift schedule based on the vehicle speed and the accelerator opening as information such as a table, and if it determines that the shift point is passed based on the current vehicle speed and the accelerator opening, a shift command is sent to the transmission 30. Output.

  A main throttle valve 15 and a sub-throttle valve 16 are provided in an intake pipe line 14 (for example, an intake manifold) of the engine 2. The throttle opening degree of the main throttle valve 15 is adjusted and controlled according to the depression amount of the accelerator pedal 17 which is an accelerator opening degree instruction device (acceleration instruction operation unit). The engine controller 18 is mechanically interlocked with the amount of depression of the accelerator pedal 17, or the engine controller 18 electrically adjusts and controls the amount of depression of the accelerator sensor 40 that detects the amount of depression of the accelerator pedal 17. Adjust the throttle opening. The accelerator sensor 40 also outputs a depression amount detection value to the 4WD controller 8.

  Further, the step motor 19 is an actuator, and the opening degree of the sub-throttle valve 16 is adjusted and controlled by the rotation angle corresponding to the number of steps. The rotation angle of the step motor 19 is adjusted and controlled by a drive signal from the motor controller 20. The sub throttle valve 16 includes a throttle sensor. Based on the detected value of the throttle opening detected by the throttle sensor, the number of steps of the step motor 19 is feedback controlled.

Here, by adjusting the throttle opening of the sub-throttle valve 16 to be less than or equal to the opening of the main throttle valve 15, the output torque of the engine 2 can be controlled independently of the driver's operation of the accelerator pedal.
An engine speed detection sensor 21 that detects the speed of the engine 2 is also provided. The engine speed detection sensor 21 outputs the detected signal to the engine controller 18 and the 4WD controller 8. Reference numeral 34 denotes a brake pedal, and the brake stroke sensor 35 detects the stroke amount of the brake pedal 34. The brake stroke sensor 35 outputs the detected brake stroke amount to the braking controller 36 and the 4WD controller 8.

The braking controller 36 controls the braking force acting on the vehicle through the braking devices 37FL, 37FR, 37RL, 37RR such as disc brakes equipped on the wheels 1L, 2R, 3L, 3R according to the input brake stroke amount. . Reference numeral 39 denotes a drive mode switch that outputs a switching command between 2WD and 4WD.
A part of the rotational torque Te of the engine 2 is transmitted to the generator 7 via the endless belt 6. The generator 7 rotates at a rotation speed Nh obtained by multiplying the rotation speed Ne of the engine 2 by the pulley ratio.

  As shown in FIGS. 2 and 3, a voltage regulator 22 (regulator) for adjusting the output voltage V is provided, and the generator control command value c1 (duty ratio) from the generator control unit 8E of the 4WD controller 8 is set. By adjusting to the corresponding field current Ifh, the power generation load of the generator 7 on the engine 2 and the voltage V to be generated are controlled. That is, the voltage regulator 22 receives the generator control command c1 (duty ratio) from the generator control unit 8E, and adjusts the field current Ifh of the generator 7 to the duty ratio according to the generator control command c1. At the same time, the output voltage V of the generator 7 is detected and output to the 4WD controller 8. The rotational speed Nh of the generator 7 can be calculated from the rotational speed Ne of the engine 2 based on the pulley ratio.

The electric power generated by the generator 7 can be supplied to the motor 4 via the electric wire 9. A junction box 10 is provided in the middle of the electric wire 9. The drive shaft of the motor 4 (electric motor) can be connected to the rear wheels 3L and 3R via the speed reducer 11 and the clutch 12. Reference numeral 13 represents a differential.
In addition, a current sensor 23 is provided in the junction box 10. The current sensor 23 detects the armature current value Iat of the power supplied from the generator 7 to the motor 4 and outputs a signal of the detected armature current Iat to the 4WD controller 8. Further, the 4WD controller 8 detects the voltage value flowing through the electric wire 9 (voltage of the motor 4). Reference numeral 24 denotes a relay, and the cutoff and connection of the voltage (current) supplied to the motor 4 is controlled by a command from the 4WD controller 8.

Further, the field current Ifm of the motor 4 is controlled by a command from the 4WD controller 8, and the drive torque is adjusted to a target motor torque Tm that is a target torque command value by adjusting the field current Ifm. Reference numeral 25 denotes a thermistor that measures the temperature of the motor 4.
A motor rotation speed sensor 26 that detects the rotation speed Nm of the drive shaft of the motor 4 is provided. The motor rotation speed sensor 26 outputs the detected rotation speed signal of the motor 4 to the 4WD controller 8.
Each wheel 1L, 1R, 3L, 3R includes a wheel speed sensor 27FL, 27FR, 27RL, 27RR. Each wheel speed sensor 27FL, 27FR, 27RL, 27RR outputs a pulse signal corresponding to the rotational speed of the corresponding wheel 1L, 1R, 3L, 3R to the 4WD controller 8 as a wheel speed detection value.

FIG. 3 shows the configuration of the 4WD controller 8.
As shown in FIG. 3, the 4WD controller 8 includes a target motor torque calculation unit 8A, a motor control unit 8B, a relay control unit 8C, a clutch control unit 8D, a generator control unit 8E, and rollback determination as rollback detection means. A portion 8F is provided. The 4WD controller 8 operates when the drive mode switch 39 is in the 4WD state.
The relay control unit 8C controls the cutoff / connection of the power supply from the generator 7 to the motor 4, and keeps the relay 24 in the connected state while in the four-wheel drive state.

The clutch control unit 8D controls the state of the clutch 12, and controls the clutch 12 to be in a connected state while determining that it is in the four-wheel drive state.
The target motor torque calculation unit 8A includes a surplus torque calculation unit 8Aa, an acceleration assist torque calculation unit 8Ab, and a motor torque determination unit 8Ac.
The surplus torque calculator 8Aa is a means for calculating surplus engine torque corresponding to the acceleration slip of the front wheels. The surplus torque calculation unit 8Aa performs a predetermined process based on each input signal every predetermined sampling time.

FIG. 4 shows a processing procedure of the surplus torque calculator 8Aa.
As shown in FIG. 4, first, in step S10, the rear wheels 3L, 3R (subordinates) are calculated from the wheel speeds of the front wheels 1L, 1R (main drive wheels) calculated based on the signals from the wheel speed sensors 27FL, 27FR, 27RL, 27RR. By subtracting the wheel speed of the driving wheel), the slip speed ΔVF which is the acceleration slip amount of the front wheels 1L and 1R is obtained.

For example, the slip speed ΔVF is calculated as follows.
An average front wheel speed VWf that is an average value of the left and right wheel speeds at the front wheels 1L and 1R and an average rear wheel speed VWr that is an average value of the left and right wheel speeds at the rear wheels 3L and 3R are calculated.
Next, from the deviation between the average front wheel speed VWf and the average rear wheel speed VWr, a slip speed (acceleration slip amount) ΔVF indicating the degree of acceleration slip of the front wheels 1L and 1R as the main drive wheels is calculated by the following equation (1). To do.
ΔVF = VWf−VWr (1)

Subsequently, in step S20, it is determined whether or not the slip speed ΔVF calculated in step S10 is greater than a predetermined value, for example, zero. Here, when it is determined that the slip speed ΔVF is equal to or less than 0, it is estimated that the front wheels 1L and 1R have not accelerated slip. Therefore, the process proceeds to step S30, and when it is determined that the slip speed ΔVF is greater than 0, the front wheels 1L and 1L Since it is estimated that 1R is accelerating slip, the process proceeds to step S40.
In step S30, zero is substituted for Tm1. Then, the process returns (the process of FIG. 4 ends).

In step S40, based on the slip speed ΔVF obtained in step S10, an absorption torque TΔVF required to suppress the acceleration slip of the front wheels 1L, 1R is calculated by the following equation (2).
TΔVF = K1 × ΔVF (2)
According to the equation (2), the absorption torque TΔVF is an amount proportional to the acceleration slip amount (slip speed ΔVF).
Subsequently, in step S50, the current load torque TG of the generator 7 is calculated by the following equation (3).
TG = K2 · (V × Ia) / (K3 × Nh) (3)
Here, V is the voltage of the generator 7, Ia is the armature current of the generator 7, Nh is the rotational speed of the generator 7, K3 is efficiency, and K2 is a coefficient.

Subsequently, in step S60, based on the absorption torque TΔVF calculated in step S40 and the load torque TG calculated in step S50, the surplus torque, that is, the power generation load torque Th to be loaded by the generator 7 is expressed by the following (4). Calculate by the formula.
Th = TG + TΔVF (4)
According to the equation (4), the power generation load torque Th increases as the absorption torque TΔVF and the load torque TG increase.
Subsequently, in step S70, it is determined whether or not the power generation load torque Th is larger than the maximum load capacity HQ of the generator 7 determined from the specifications and the like. When it is determined that the power generation load torque Th is equal to or less than the maximum load capacity HQ of the generator 7 (Th ≦ HQ), the process proceeds to step S90, where the target power generation load torque Th exceeds the maximum load capacity HQ of the generator 7. If there is (Th> HQ), the process proceeds to step S80.

In step S80, the power generation load torque Th is limited to the maximum load capacity HQ (Th = HQ). Then, the process proceeds to step S90.
In step S90, a first target motor torque Tm1 corresponding to the generator load torque Th is calculated. Then, the process ends (the process of FIG. 4 ends). The first target motor torque Tm1 is a target motor torque corresponding to the acceleration slip amount of the front wheels.
In the above process, the first target motor torque Tm1 is calculated after obtaining the load torque at the generator once. However, the first target motor torque Tm1 is directly multiplied by a predetermined gain to the acceleration slip amount of the front wheels. May be calculated.

Next, processing of the acceleration assist torque calculation unit 8Ab will be described.
The acceleration assist torque calculator 8Ab calculates a second target motor torque Tm2 corresponding to the vehicle speed and the accelerator opening θ (acceleration instruction amount by the driver) based on the map shown in FIG. The second target motor torque Tm2 is set to be larger as the accelerator opening θ is larger and smaller as the vehicle speed is smaller, and to be zero at a predetermined vehicle speed or higher. The predetermined vehicle speed is, for example, a low-speed vehicle speed estimated that the vehicle has left the start state.

This characteristic value is set so that the maximum value of the second target motor torque Tm2 (CONST portion in FIG. 5) becomes a motor torque that is considered to be able to start on the road surface that is normally assumed.
Next, the motor torque determination unit 8Ac performs select high for the first and second target motor torques Tm1 and Tm2 calculated by the surplus torque calculation unit 8Aa and the acceleration assist torque calculation unit 8Ab, and sets the larger value to the target motor torque. Determined as Tm. That is, the larger value of the first target motor torque Tm1 corresponding to the absorption torque TΔVF determined by the acceleration slip amount and the second target motor torque Tm2 corresponding to the accelerator opening θ is set to the target motor torque. Set to Tm. Then, the target motor torque Tm is output to the motor control unit 8B.

Next, the process of the motor control unit 8B will be described with reference to FIG.
The motor control unit 8B operates at a predetermined sampling time. First, in step S200, it is determined whether or not the target motor torque Tm is greater than “0”. If it is determined that Tm> 0, since the front wheels 1L and 1R are in the four-wheel drive state (motor drive request state) such as acceleration slipping, the process proceeds to step S210. If it is determined that Tm ≦ 0, the vehicle is not in the four-wheel drive state (motor drive request state), and the process proceeds to step S270.

In step S270, various signals in the two-wheel drive state such as a power generation stop (target power generation torque V = 0) signal are output. Then, the process returns (the process of FIG. 6 ends).
In step S210, it is determined whether or not it is a transition from the four-wheel drive state to the two-wheel drive state. If it is determined that the transition is to the two-wheel drive state, the process proceeds to step S270, and if it is the four-wheel drive state, step S215 is performed. Proceed to For example, if it is determined that the motor rotation speed has approached the allowable limit rotation speed, or if the range of the transmission 30 is in the non-drive range (parking or neutral), it is determined that the shift to the two-wheel drive state has occurred.

In the process of step S270 that proceeds from step S210, a four-wheel drive end process such as outputting a clutch-off command to the clutch control unit 8D and stopping power generation (target power generation torque V = 0) is performed. Then, the process returns (the process in FIG. 6 ends).
In step S215, a clutch-on command is output to the clutch control unit 8D. Then, the process proceeds to step S220.
In step S220, the rotational speed Nm of the motor 4 detected by the motor rotational speed sensor 21 is input, a target motor field current Ifm corresponding to the rotational speed Nm of the motor 4 is calculated, and the target motor field current Ifm is calculated. Is the target value of the motor field current. Feedback control is performed based on the deviation of the field current value detected by the sensor from the target motor field current Ifm.

  Here, the target motor field current Ifm with respect to the rotational speed Nm of the motor 4 is a constant predetermined current value when the rotational speed Nm is equal to or lower than the predetermined rotational speed, and when the motor 4 exceeds the predetermined rotational speed. Reduces the field current Ifm of the motor 4 by a known field weakening control method. That is, when the motor 4 is rotated at a high speed, the motor torque decreases due to the increase of the motor induced voltage E. Therefore, as described above, when the rotational speed Nm of the motor 4 exceeds a predetermined value, the field current Ifm of the motor 4 is By reducing the induced voltage E and reducing the induced voltage E, the current flowing through the motor 4 is increased to obtain the required motor torque. As a result, even if the motor 4 rotates at high speed, the increase in the motor induced voltage E is suppressed and the decrease in the motor torque is suppressed, so that the required motor torque can be obtained. In addition, by controlling the motor field current Ifm in two stages of less than a predetermined rotation speed and more than a predetermined rotation speed, the control electronic circuit can be made cheaper than continuous field current control.

  It is also possible to provide motor torque correction means for continuously correcting the motor torque by adjusting the field current Ifm according to the rotational speed Nm of the motor 4 with respect to the required motor torque. That is, for the two-stage switching, the field current Ifm of the motor 4 is preferably adjusted according to the motor rotation speed Nm. As a result, even if the motor 4 rotates at high speed, the increase in the induced voltage E of the motor 4 is suppressed and the decrease in the motor torque is suppressed, so that the required motor torque can be obtained. In addition, since smooth motor torque characteristics can be achieved, the vehicle can be driven more stably than in the two-stage control, and the motor drive efficiency can always be improved.

Subsequently, in step S250, the corresponding target armature current Ia is obtained based on a map or the like using the target motor torque Tm and the target motor field current Ifm as variables.
Subsequently, in step S260, based on the target armature current Ia obtained in step S250, the target generated voltage V (= Ia × R + E: E is the induced voltage of the motor, and R is the generator and motor. The resistance between and is calculated and output. Then, the process ends (the process of FIG. 6 ends).
The generator control unit 8E calculates a generator control command value to be the target generated voltage V while inputting the current generated voltage, and responds to the generator control command c1 via the voltage regulator 22. The output voltage of the generator is controlled by adjusting the field current Ifh of the generator 7 to the above value.

Next, processing of the rollback determination unit 8F will be described.
The rollback determination unit 8F determines whether or not the vehicle is rolling back, and outputs a rollback determination flag Fr to the motor control unit 8B. In the rollback determination, first, it is determined whether or not the shift of the transmission 30 is in the forward drive range. Thereafter, when it is determined that the shift is in the forward drive range, the induced voltage Er of the motor is a predetermined rollback determination threshold Er. _This is performed by determining whether or not it is smaller than _TH (for example, 0.6 V).

Based on the motor voltage Vm, the motor armature current Ia, and the motor resistance R, the induced voltage Er of the motor is calculated based on the following equation (5).
Er = Vm−Ia × R (5)
Then, when this way the induced voltage Er which is calculated is smaller than the rollback determination threshold Er _TH, the vehicle is a rollback determination flag Fr is judged to be rolled back and set to "1", Er When ≧ Er _TH, it is determined that the rollback is not performed, and the rollback determination flag Fr is reset to “0”.

Here, whether the induced voltage Er is smaller than a predetermined rollback determination threshold value Er _TH or not can determine whether or not the rollback state is present. For example, the motor rotates when the vehicle moves forward. If the setting is made so that the induced voltage Er is outputted in the positive direction when the motor rotates in the same direction as the direction, the induced voltage Er becomes a negative value when the motor rotates in the reverse direction. In the calculation, when the induced voltage Er is a negative value, if the process of “0” is performed, the induced voltage Er is equal to the wheel speed being higher than the predetermined value (the wheel is rotating). Since it is “0”, the rollback state can be detected on the assumption that it is smaller than the rollback determination threshold value Er _TH and that the motor is rotating in the reverse direction to the case of rotating in the forward direction.

  Further, the rollback determination is described as a state in which the shift is reverse when the transmission shift is in the forward drive range, but the present invention is not limited to this, and the shift shift is in the reverse drive range. The state where the vehicle moves forward can also be determined as the rollback state. In this case, it is determined whether or not the shift of the transmission is in the reverse drive range, and the rollback is performed when it is determined that the shift of the transmission is in the reverse drive range and the motor is rotating in the vehicle forward direction. It can be determined that it is in a state.

Next, processing of the engine controller 18 will be described.
In the engine controller 18, processing as shown in FIG. 7 is performed based on each input signal for every predetermined sampling time.
As shown in FIG. 7, first, in step S300, the acceleration slip amount ΔV of the front wheels 1L and 1R as the main drive wheels is calculated.
Subsequently, in step S310, it is determined whether or not the acceleration slip amount ΔV calculated in step S300 exceeds the target slip amount T _slip . If the acceleration slip amount ΔV exceeds the target slip amount T _slip (ΔV> T _slip ), the process proceeds to step S400, and if the acceleration slip amount ΔV is equal to or less than the target slip amount T _slip (ΔV ≦ T _Tslip ), the process proceeds to step S320. The target slip amount T _slip is set to, for example, about 10% in terms of slip ratio.

In step S320, a target output torque TeN requested by the driver is calculated based on a detection signal from the accelerator sensor 40 and the like.
In step S330, the current output torque Te is calculated based on the throttle opening, the engine speed Ne, and the like.
Subsequently, in step S340, the deviation ΔTe of the target output torque TeN calculated in step S320 with respect to the current output torque Te calculated in step S330 is output based on the following equation (6). Then, the process proceeds to step S350.
ΔTe = TeN−Te (6)

On the other hand, in step S400, so-called engine TCS control is performed, and a predetermined TCS torque change is substituted into the deviation ΔTe calculated in step S340. Then, the process proceeds to step S350.
In step S350, a change Δα of the throttle opening α corresponding to the deviation ΔTe is calculated, and an opening signal corresponding to the change Δα of the opening is output to the step motor 19 and returned (see FIG. 7).
In the above description, the opening degree signal Δα corresponding to the deviation ΔTe is output for the sake of easy understanding, but in practice, every time the engine is started in order to smooth the change in torque or the like. The torque is changed by a predetermined torque increase or torque decrease.

FIG. 8 shows a processing procedure of front and rear wheel drive cooperative control at the time of rollback start.
As shown in FIG. 8, first, in step S501, the brake release is determined. For example, it is determined whether or not the brake pedal is in an ON state based on a detection signal of a brake detection sensor that detects an operation state of the brake pedal. If the brake pedal is changed from the ON state to the OFF state, the process proceeds to the next step S502.

Subsequently, in step S502, it is determined whether or not rollback has been detected (processing of the rollback determination unit 8F). If rollback is detected, the process proceeds to step S503. If rollback cannot be detected, the process proceeds to step S509.
In step S503, motor regeneration torque control during rollback is performed. As motor regeneration torque control, control is performed so that the motor does not regenerate. For example, the motor is prevented from regenerating by causing a large loss current to flow through the motor. By doing in this way, generation | occurrence | production of a high voltage failure can be suppressed and 4WD performance can be ensured, for example.

  In step S504, it is determined whether or not the accelerator is ON. For example, based on the detection signal of the accelerator sensor 40, it is determined whether or not the accelerator is in an ON state (operation state). If the accelerator is on, the process proceeds to step S505. If the accelerator is off, the process of step S503 is performed again. That is, the motor regeneration torque control during the rollback is performed while the accelerator OFF state is maintained.

In step S505, engine torque suppression control and motor torque suppression control are performed. Engine TCS control is performed as engine torque suppression control. That is, normally, engine TCS control that operates when the acceleration slip amount ΔV exceeds the target slip amount T _slip is satisfied, even if such a condition is not satisfied, the engine TCS control is performed in step S505. Operate. By this engine TCS control, the output of the engine is reduced (the target output torque TeN or the deviation ΔTe is suppressed). Further, as motor torque suppression control, control for suppressing (limiting) the motor torque is performed. Specifically, the target motor torque Tm is limited (increase is limited).

  Subsequently, in step S, it is determined whether or not the rollback has ended (whether or not the rollback has changed to the original traveling direction). If the rollback is completed, the process proceeds to step S507. If the rollback is not completed, the processes from step S503 are performed. That is, while detecting rollback, engine torque suppression control and motor torque suppression control are performed based on the accelerator operation state.

In step S507, the engine torque suppression control and the motor torque suppression control are terminated, and the engine torque and the motor torque are restored (gradually increased).
Subsequently, in step S508, it is determined whether or not the engine torque has completely returned, that is, whether or not the control has returned to the control based on the target output torque TeN requested by the driver. If the engine torque has been completely restored, the process proceeds to step S509. If the engine torque has not been restored, the process of step S507 is performed again.

By the processing of step S507 and step S508, the engine torque suppression control is finished, and the engine torque is returned so that the target output torque TeN requested by the driver is obtained based on the detection signal from the accelerator sensor 40 and the like. . Further, the motor torque suppression control is terminated and the motor torque is returned. That is, the restriction on the target motor torque Tm is released, and the process proceeds to motor power running torque control. At this time, the target motor torque Tm is gradually increased to the original value.
In step S509, normal control is performed. That is, normal engine torque control and normal motor power running torque control when starting or running at low speed, and normal TCS control are performed as necessary.

(Operation)
The operation is as follows. It is assumed that the drive mode switch 39 is operated to the 4WD state.
At the time of starting, before the acceleration slip occurs on the front wheels, the motor and the generator are controlled based on the target motor torque corresponding to the accelerator opening. Furthermore, if the road surface μ is small or if the driver depresses the accelerator pedal 17 and the front wheels 1L and 1R, which are the main drive wheels 1L and 1R, are accelerated and slipped, the target motor torque corresponding to the accelerated slip is calculated. The target motor torque and the target motor torque corresponding to the accelerator opening are selected high, and the motor and the generator are controlled based on the larger target motor torque. Thereby, the acceleration performance of the vehicle at the time of start is improved.

Now, when the vehicle stops on the uphill road with the vehicle shifted to the D range and the driver tries to step on the accelerator pedal by taking off the brake pedal at the start, the vehicle will use the creep torque of the automatic transmission. It is assumed that the vehicle cannot be maintained and has been rolled back. At this time, the induced voltage Er of the motor is smaller than the rollback determination threshold Er _TH, vehicle rollback determination unit 8F is set to "1" rollback determination flag Fr is judged to be rolled back .

  FIG. 9 is a diagram showing time charts of various values when the driver depresses the accelerator pedal in a state where the vehicle is rolled back. (A) shows the brake operation state, (b) shows the accelerator operation state, (c) shows the vehicle speed, (d) shows the wheel speed, (e) ) Shows the front wheel driving force, FIG. 5 (f) shows the rear wheel driving force, FIG. 4 (g) shows the road surface transmission force of the front wheel, and FIG. 5 (h) shows the road surface transmission force of the rear wheel.

  When the brake is turned off, the vehicle body speed in the direction opposite to the traveling direction is indicated (values (a) and (c) in the figure between time t1 and t2). At this time, rollback is detected, and motor regeneration torque control during rollback is started. Then, at the timing when accelerator ON is detected, the driving torque is generated on the front wheels while the engine torque is reduced by the engine torque suppression control. As a result, the driving force of the front wheels is suppressed more than the driving force at the time of starting normally (on a flat ground or the like, the conventional example) (value in FIG. 5E immediately after time t2). At the same time, as assist control for the front wheels, driving force is generated on the rear wheels while the motor torque is reduced by motor torque suppression control. As a result, the driving force of the rear wheels is suppressed more than the driving force at the time of normal starting (a conventional example such as a flat ground) (value in FIG. 8F immediately after time t2).

  Thereafter, when there is no rollback, the engine torque suppression control and the motor torque suppression control are terminated, and the engine torque and the motor torque are returned. As a result, the driving force of the front wheels and the driving force of the rear wheels gradually increase so as to become values corresponding to the accelerator operation (values (e) and (f) in the figure immediately after time t3).

  As described above, when the rollback starts, the driving force for the rear wheels is generated in addition to the driving force for the front wheels, but the driving force for the front wheels and the rear wheels is suppressed compared to the normal case (time t2). (Values of (e) and (f) in FIG. 5) and t3). Thereby, the fall of the road surface transmission force of the driving force of a front wheel and a rear wheel can be controlled (the value of the figure (g) and (h) between time t2 and t3). It can be said that the road surface transmission force improvement of the driving force of the front wheel and the road surface transmission force improvement of the driving force of the rear wheel combined with each other, and it was possible to suppress the road surface transmission force of both the front and rear wheels. As a result, it is possible to prevent slippage in both the front and rear wheels, and to obtain a wheel speed that is substantially close to the vehicle body speed (value in FIG. 4D between times t2 and t3).

  In the description of the embodiment, the engine 2 realizes an internal combustion engine that drives the main drive wheels. Moreover, the generator 7 implement | achieves the generator driven with the internal combustion engine. The motor 4 realizes a motor that is driven by the electric power of the generator and drives the driven wheels. Further, the target motor torque calculation unit 8A and the motor control unit 8B realize motor output torque control means for controlling the output torque of the motor to a target motor torque command value for assisting the main drive wheels. Further, the engine controller 18 realizes main driving wheel driving force control means for controlling the output torque of the internal combustion engine according to the accelerator operation state and controlling the driving force of the main driving wheels. Further, the rollback determination unit 8F realizes a vehicle travel direction means for detecting the travel direction of the vehicle. Further, the accelerator sensor 40 realizes a start operation detecting means for detecting the start operation of the vehicle. Thereby, in the embodiment, when the vehicle traveling direction detection unit detects a rollback of the vehicle and the start operation detection unit detects a start operation, the main driving wheel driving force control unit The motor output torque control means is configured to control the output torque of the motor to be the target motor torque command value while limiting an increase in wheel driving force.

Moreover, the said embodiment can also be implement | achieved by the following structures.
In the above-described embodiment, when the rollback of the vehicle is detected and the start operation is detected, the increase in the driving force of the front wheels and the rear wheels is limited. On the other hand, a detection means for detecting a low μ road is provided, and the increase in the driving force of the front wheels and the rear wheels can be limited on condition that the low μ road is detected.

(Function and effect)
(1) When a rollback of the vehicle is detected and a start operation is detected, a driving force is generated on the rear wheel, which is a driven wheel, by the motor as an assist control for driving the front wheel, which is the main drive wheel, while an accelerator operation is performed. The increase of the driving force of the main driving wheel according to the state is limited. Thus, by limiting the increase in the driving force of the main drive wheel according to the accelerator operation state, it is possible to prevent the main drive wheel from slipping during assist control of the drive of the main drive wheel by the slave drive wheel. Thereby, the driving force of the front wheel at the time of start can be used effectively. As a result, for example, the convergence of the rollback of the vehicle can be improved and the vehicle can be started easily.

(2) In addition to limiting the driving force of the front wheels, the increase of the driving force of the rear wheels is limited. As a result, the rear wheels can be prevented from slipping, and the driving force of the rear wheels when starting can be effectively utilized.
(3) When the rollback is completed (after the rollback has converged), the restriction on the driving force of the front wheels and the rear wheels is released, and the driving force of the front wheels and the rear wheels is gradually returned to the normal value. Thereby, even if it is a low micro road, start performance can be improved.

(4) The presence / absence of rollback is determined based on the rotation state of the motor. As a result, the rollback can be reliably detected without requiring a road surface gradient detecting means.
(5) By limiting the increase in the driving force of the front and rear wheels under the condition of detecting a low μ road, the increase in the driving force of the front and rear wheels is limited until the front and rear wheels do not slip. Can be prevented. In other words, it is possible to prevent an unnecessary increase in the driving force of the front wheels and the rear wheels.

It is a schematic structure figure showing an embodiment of the present invention. It is a system configuration figure showing an embodiment of the present invention. It is a block diagram which shows the 4WD controller in FIG. It is a flowchart which shows the process performed with a surplus torque calculating part. It is a figure which shows the relationship between an accelerator opening and a 2nd target motor torque. It is a flowchart which shows the process performed with a motor control part. It is a flowchart which shows the process performed with an engine controller. It is a flowchart which shows the process sequence of front-and-rear wheel drive cooperative control at the time of rollback start. It is a time chart explaining operation | movement.

Explanation of symbols

  1L, 1R front wheel, 2 engine, 3L, 3R rear wheel, 4 motor, 6 belt, 7 generator, 8 4WD controller, 8A target motor torque calculator, 8Aa surplus torque calculator, 8Ab acceleration assist torque calculator, 8Ac motor Torque determination unit, 8B motor control unit, 8C relay control unit, 8D clutch control unit, 8E generator control unit, 8F rollback judgment unit, 9 wires, 10 junction box, 11 speed reducer, 12 clutch, 14 intake pipe, 15 Main throttle valve, 16 Sub throttle valve, 18 Engine controller, 19 step motor, 20 Motor controller, 21 Engine speed sensor, 22 Voltage regulator, 23 Current sensor, 26 Motor speed sensor, 27FL, 27FR, 27RL, 27RR wheel speed sensor, 30 shifts Machine, 31 differential gear, 32 shift position detecting means, 34 brake pedal, 35 brake stroke sensor, 36 brake controller, 37FL, 37FR, 37RL, 37RR brake device, 39 drive mode switch, 40 accelerator sensor

Claims (5)

In a vehicle driving force control apparatus comprising: an internal combustion engine that drives main drive wheels; a generator that is driven by the internal combustion engine; and a motor that is driven by the power of the generator to drive the driven wheels.
Motor output torque control means for controlling the output torque of the motor to a target motor torque command value for assisting the main drive wheel;
Main driving wheel driving force control means for controlling the output torque of the internal combustion engine according to the accelerator operation state and controlling the driving force of the main driving wheel;
Vehicle traveling direction means for detecting the traveling direction of the vehicle;
Start operation detecting means for detecting the start operation of the vehicle;
When the vehicle travel direction detection means detects a rollback of the vehicle and the start operation detection means detects a start operation, the main drive wheel drive force control means limits an increase in drive force of the main drive wheel. In addition, the motor output torque control means controls the output torque of the motor to be the target motor torque command value.   When the rollback detection means detects a rollback of the vehicle and the start operation detection means detects a start operation, the motor output torque control means limits the target motor torque command value. The vehicle driving force control apparatus according to claim 1.   When the vehicle traveling direction detecting means detects that the vehicle has changed from the rollback to the original traveling direction, the main driving wheel driving force control means releases the restriction on the increase in driving force of the main driving wheel, and the accelerator The driving force of the main driving wheel is gradually returned to a value according to the operation state, and the motor output torque control means releases the restriction of the target motor torque command value, and the output torque of the motor is changed to the target motor torque. The vehicle driving force control device according to claim 2, wherein the vehicle driving force control device gradually returns to a command value.   The vehicle driving force according to any one of claims 1 to 3, wherein the vehicle traveling direction detection means determines whether or not the vehicle is rolled back based on a rotation state of the motor. Control device.   In the case of a low road surface μ, the main driving wheel driving force control means detects the main driving wheel driving force control means in addition to the vehicle traveling direction detection means detecting vehicle rollback and the start operation detection means detecting start operation. The motor output torque control means controls the output torque of the motor to be the target motor torque command value while limiting an increase in driving force of the driving wheel. The vehicle driving force control apparatus according to claim 1.

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