JP3646632B2 - Vehicle travel control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention provides a wheel slip during braking (deceleration).ButEstimatedWhenDecreasing braking force (braking force)ByThe present invention relates to a vehicle travel control device that suppresses slipping of wheels.
[0002]
[Prior art]
  Conventionally, examples of the vehicle running control device of the above-described example include those described in JP-A-8-98313, JP-A-8-98314, and JP-A-2000-108873.
[0003]
  JP-A-8-98313 and JP-A-8-98314 described above are braking devices for an electric vehicle that drives the vehicle with electric energy, and are front wheels (drive wheels) that are driven by an electric motor. And a rear wheel as a driven wheel, and each wheel is provided with a wheel cylinder for hydraulic braking, and when shifting from regenerative braking of the electric motor to hydraulic ABS (anti-skid brake system) control. The regenerative braking is gradually weakened, and when the regenerative braking force becomes zero or a value close to zero, switching to hydraulic braking is performed to prevent sudden changes in vehicle speed due to this switching. .
[0004]
  Japanese Patent Application Laid-Open No. 2000-108873 discloses a hybrid vehicle that drives a front wheel by using a motor that generates driving force by battery power and an engine as an internal combustion engine, and is used during braking. When the slip ratio of the wheel exceeds a predetermined value, the battery is charged by recovering electrical energy via the above-described motor during the deceleration and the slip suppression means for reducing the braking pressure of the wheel to suppress the lock of the wheel. Energy recovery means, and increases the regenerative braking force of the motor during ABS operation by the slip suppression means.
[0005]
  However, none of the above-described prior arts disclose a technical concept relating to regeneration on the rear wheel side and front wheel braking.
  By the way, when a 4WD vehicle that drives a rear wheel of a vehicle by a motor is configured and the rear wheel is regeneratively braked and the regenerative energy is recovered by the motor having high response to a hydraulic brake at the time of deceleration, Although the regenerative braking at the time of deceleration gives a negative torque (reverse torque) to the rear wheels, the braking brake becomes large even though it is desired to sufficiently recover the regenerative energy at the time of deceleration. In such a case, the rear wheel is likely to slip, and if the rear wheel slips, there is a problem that the rear part of the vehicle swings to the left and right, resulting in poor travel safety.
[0006]
[Problems to be solved by the invention]
  The present invention comprises regenerative braking means for performing regenerative braking of the rear wheels by the rear wheel motor during deceleration, and when the rear wheel slip is estimated (including prediction or determination), the regenerative control means By reducing the degree of regenerative braking of the rear wheels from that at the time of non-estimation, at the time of normal deceleration when slip does not occur, the recovery of regenerative energy by the rear wheel motor is maximized, and when slip occurs or When the possibility of slip occurrence is large, it is possible to suppress the rear wheel slip, which has a greater influence on the vehicle behavior than the front wheel slip,Another object of the present invention is to provide a vehicle travel control device that can maintain the braking performance of the vehicle during deceleration by increasing the degree of braking of the front wheels at the time of slip estimation and can prevent longitudinal vibration of the vehicle. To do.
[0007]
[Means for Solving the Problems]
  The vehicle travel control apparatus according to the present invention includes a rear wheel drive unit that motor-drives a rear wheel of the vehicle, a regenerative braking unit that regeneratively brakes the rear wheel by the motor during deceleration, and a braking force applied to the front wheel of the vehicle during deceleration. A vehicle travel control device comprising front wheel braking means for applying, when the rear wheel slip state is estimated by the estimating means for estimating the slip state of the rear wheel, and when the estimating means estimates the rear wheel slip, Braking control means for reducing the regenerative braking degree of the wheel compared to when it is not estimatedThe braking control means increases the degree of braking of the front wheels by the front wheel braking means when the slip state is estimated, and controls the longitudinal vibration of the vehicle according to the increase or decrease of the slip when the rear wheel slip is detected by the estimation means. Therefore, the control timing for increasing / decreasing the degree of braking by the regenerative braking means and the braking by the front wheel braking means so that the direction of torque change between the control torque of the regenerative braking means and the control torque of the front wheel braking means are opposite to each other. The degree increase / decrease control time is configured to differ by a predetermined time.
[0008]
  The front wheel braking means configured as described above can be constituted by engine brake or front wheel motor regeneration or hydraulic brake, and the estimation means for estimating the slip condition of the rear wheel is a means for predicting or detecting a low μ road or an actual slip ratio. Means for detecting.
[0009]
  In the above configurationAccording toDuring normal deceleration as slip non-estimation (non-prediction or non-judgment), the regenerative braking means performs regenerative braking by the motor that drives the rear wheels, so the recovery of regenerative energy by the rear wheel motor is maximized. Can be increased as much as possible.
[0010]
  Also,When the estimation means estimates (predicts or determines) the slip state of the rear wheels driven by the motor, the braking control means described above reduces the degree of regenerative braking of the rear wheels by the regenerative braking means relative to the non-estimated time. During estimation, slipping of the rear wheels can be suppressed to ensure driving stability.The
[0011]
  further,The braking control means increases the degree of braking of the front wheels by the front wheel braking means when the slip state is estimated.So decreaseWhen the slip state of the rear wheels is estimated (predicted or determined) by the above-described estimating means at the time of speed, the braking control means increases the degree of braking of the front wheels by the front wheel braking means that applies braking force to the front wheels of the vehicle. .
  As a result, the degree of regenerative braking on the rear wheel side is reduced at the time of slip estimation. In this case, braking on the front wheel can be performed, and the braking performance of the vehicle during deceleration can be maintained.The
[0012]
  Moreover,When detecting slip of the rear wheel by the estimating means, in order to suppress the longitudinal vibration of the vehicle according to the increase or decrease of the slip,The direction of torque change of the control torque of the regenerative braking means and the control torque of the front wheel braking means is opposite to each other.The braking degree increase / decrease control time by the regenerative braking means and the braking degree increase / decrease control time by the front wheel braking means are configured to differ by a predetermined time.SoWhen the fixing means detects the slip of the rear wheel, the brake control is executed such that the braking degree increase / decrease control time by the rear wheel side regenerative braking means differs from the braking degree increase / decrease control time by the front wheel side braking means for a predetermined time. Is done.
  As a result, the longitudinal vibration of the vehicle due to the slip suppression control can be suppressed by the braking control of the front wheels and the rear wheels.
[0013]
【Example】
  An embodiment of the present invention will be described in detail with reference to the drawings.
  The drawings show a vehicle travel control device. In this embodiment, since the vehicle travel control device is applied to a hybrid vehicle, the mechanical configuration of the hybrid vehicle will be described first with reference to FIG.
[0014]
  [Mechanical configuration of hybrid vehicle]
  The hybrid vehicle includes a rear wheel motor 2 driven by electric power supplied from a battery 1 (hereinafter simply referred to as a rear wheel motor) and an engine 3 driven by the explosive force of fuel such as gasoline. In accordance with the traveling state of the vehicle, which will be described later, traveling using only the rear wheel motor 2, traveling using only the engine 3, or traveling using both 2 and 3 is realized.
[0015]
  The engine 3 transmits a driving force to a continuously variable transmission 6 (so-called CVT) by engaging a clutch 5 as a switching means via a torque converter 4. The continuously variable transmission 6 converts the driving force input from the engine 3 into a predetermined torque and rotational speed according to the running state (or by the operation of the driver), and passes through the gear train 7 and the front differential 8. It is transmitted to the front wheels 9,9. The engine 3 drives a generator 10 (front wheel motor) to charge the battery 1.
  Here, it goes without saying that an automatic transmission (so-called AT) may be used instead of the continuously variable transmission.
[0016]
  The rear wheel motor 2 is driven by electric power supplied from the battery 1 and transmits driving force to the rear wheels 13 and 13 via the gear 11 and the rear differential 12.
  The engine 3 is equipped with a direct-injection gasoline engine or a high heat cost type that delays the opening timing of the intake valve, and the rear wheel motor 2 uses, for example, an IPM synchronous motor (AC motor) with a maximum output of 20 KW to generate power. For example, the machine 10 having a maximum output of 10 KW is used, and the battery 1asFor example, a maximum of 30KW nickel metal hydride battery is installed.
[0017]
  In the normal case, the generator 10 is supplied with electric power from the battery 1 when the engine is started, and cranks the engine 3. If this generator 10 with a maximum output of 10 kW is used, unlike the conventional alternator (maximum output of about 5 kW), the engine 3 is started at an early stage after idling stop for the purpose of exhaust gas regulation and fuel efficiency improvement. The number of revolutions can be raised quickly.
[0018]
  In this embodiment, when only the rear wheel motor 2 is driven, the rear wheels 13 and 13 are drive wheels, and the front wheels 9 and 9 are driven wheels, whereas when only the engine 3 is driven, the front wheels 9 and 9 are driven. Becomes driving wheels, and the rear wheels 13 and 13 become driven wheels.
[0019]
  On the other hand, an overall control ECU 20 (hereinafter simply referred to as ECU) as a control means includes a CPU, ROM 14, RAM 15 (see FIG. 2), an interface circuit, an inverter circuit, and the like. In addition to controlling the injection amount and the like, the output torque of the rear wheel motor 2 and the rotational speed Nm are controlled so as to absorb the torque fluctuation of the engine 3 and the shift shock of the continuously variable transmission 6. Further, the ECU 20 controls the battery 1 to charge the electricity generated by the generator 10 when the engine 3 is operated, or to drive the rear wheel motor 2 with the battery 1.
[0020]
  The hybrid vehicle of this embodiment is equipped with an ABS (anti-skid brake system). The ABS supplies brake hydraulic pressure to the wheel cylinders disposed on the front wheels 9 and 9 and the rear wheels 13 and 13, thereby performing a hydraulic brake operation, and brake devices 16, 17, 18, and 19, respectively. Brake control CPU 30 for controlling the brake fluid pressure to the brake devices 16-19(See Figure 2)Is provided.
[0021]
  The brake control CPU 30 detects whether or not the wheel is likely to lock from the slip rate of each wheel when the ECU 20 performs a brake operation (deceleration), and when this state is detected, the braking force (braking force) of the wheel is detected. To control the target value while suppressing the wheel lock.
[0022]
  [Electric configuration of hybrid vehicle]
  FIG. 2 is a block diagram showing the electrical configuration of the hybrid vehicle of this embodiment.
  As shown in FIG. 2, the ECU 20 detects a signal from the vehicle speed sensor 21 that detects the vehicle speed, a signal from the engine speed sensor 22 that detects the rotational speed Ne of the engine 3, and a voltage supplied to the engine 3. A signal from the voltage sensor 23, a signal from the throttle sensor 24 that detects the opening of the throttle valve of the engine 3, a so-called TVO, a signal from the gasoline remaining amount sensor 25, and a remaining charge amount sensor 26 that detects the remaining charged amount of the battery 1. , A signal from the shift range sensor 27 for detecting the shift range by the select lever, a signal from the accelerator stroke sensor 28 for detecting the depression amount of the accelerator pedal by the driver, a signal from the start switch 29, etc. Control of throttle opening TVO, ignition timing and fuel injection amount for engine 3 Performs, performs control of electric power supplied to the rear wheel motor 2. Further, the ECU 20 is composed of the LCD and the like from the above various sensor signals, the data concerning the driving state of the vehicle, the vehicle speed, the engine speed Ne, the voltage, the gasoline remaining amount, the remaining battery charge amount, the shift range, the power supply system, etc. It is displayed via the display unit 31.
[0023]
  The brake control CPU 30 has a ROM 32 as a program storage means and a RAM 33 as a data storage means. The CPU 30 is connected to the ECU 20 so as to be capable of two-way communication. The slip amount (rate) of each wheel is calculated from the vehicle speed VB estimated from the wheel speed and the current wheel speed, and whether the drive wheel is likely to slip from the wheel speed change (rate) of the drive wheel and the driven wheel. If this state is detected, the output torque of the engine 3 or the rear wheel motor 2 is reduced, or the braking pressure is controlled so as to converge to the target slip ratio, and the slip at the time of acceleration / deceleration of the drive wheel is controlled. Suppress.
[0024]
  When the attitude control device is mounted, the yaw rate sensor 35, the lateral acceleration sensor 36, the steeringRudderYou may comprise so that each signal may be input from the angle sensor 37. FIG.
[0025]
  [Basic operation mode]
  The ECU 20 (control means) described above sets the following various basic operation modes based on the vehicle speed V, the accelerator opening degree α, the battery charge amount BC, and the like.
[0026]
  [When starting]
  At the start of the vehicle, the electric power of the battery 1 is supplied to the rear wheel motor 2 and the rear wheel motor 2 is driven to run the rear wheels 13 and 13.
[0027]
  [When required torque is low or vehicle speed is low]
  When the required torque is low or the vehicle speed is low, the power of the battery 1 is supplied to the rear wheel motor 2 and the rear wheel motor 2 is driven to run the rear wheels 13 and 13.
[0028]
  [When required torque is high or vehicle speed is high]
  When the required torque is high or the vehicle speed is high, first, the electric power of the battery 1 is supplied to the generator 10, and the generator 10 is driven by a motor so that power transmission means such as a pulley and a belt or a sprocket and a chain shown in FIG. The engine 3 is started (cranking) through the engine 38, and after the engine 3 is started (after the complete explosion), the front wheels 9, 9 are driven at the engine output.
[0029]
  In this case, even if power is supplied from the battery 1 to the rear wheel motor 2, the rear wheel motor 2 is driven with a relatively small torque, and the rear wheels 13 and 13 are driven by the output of the rear wheel motor 2. Good. That is, it is desirable not to drag the rear wheels 13, 13 when the front wheels 9, 9 are traveling.
[0030]
  [When decelerating and the vehicle speed is high]
  When the vehicle is decelerating and the vehicle speed is high (for example, the vehicle speed is determined based on 40 km / h as a threshold value), the rear wheel motor 2 is regeneratively driven by wheel input from the rear wheels 13 and 13, and this regenerative energy is In consideration of the characteristics of the motor that the negative torque is small during high rotation, the engine brake is applied, the generator 10 is regeneratively driven, and this regenerative energy is supplied to the battery 1.
[0031]
  [When decelerating and vehicle speed is medium or low]
  When the vehicle is decelerating and the vehicle speed is below a threshold value (for example, 40 km / h), the rear wheel motor 2 is regeneratively driven by wheel input from the rear wheels 13 and 13, and this regenerative energy is supplied to the battery 1.
[0032]
  [When the battery is low and the engine is running]
  When the charge amount of the battery 1 is small and the engine is in operation, the generator 10 is regeneratively driven via the power transmission means 38 and this regenerative energy is supplied to the battery 1.
[0033]
  [When the battery charge is low and the engine is stopped]
  When the charge amount of the battery 1 is small and the engine is stopped (when the vehicle is stopped), electric power is supplied from the battery 1 to the generator 10 under the OFF condition of the clutch 5, and the generator 10 is driven by a motor so that the engine 3 is cranked, and after the engine 3 is started, the generator 10 is regeneratively driven by the output of the engine 3 via the power transmission means 38, and this regenerative energy is supplied to the battery 1.
  The above is the description of the basic operation mode set by the ECU 20.
[0034]
  In addition, the ECU 20 described above performs regenerative braking means for performing regenerative braking of the rear wheels by the rear wheel motor 2 during deceleration (see step S4 in the flowchart shown in FIG. 3 and YES determination in step S7),
Front wheel braking means for applying braking force to the front wheels 9, 9 of the vehicle during deceleration (see step S16 in the flowchart shown in FIG. 3);
Estimating means (see steps S9 and S10 in the flowchart shown in FIG. 3) for estimating (predicting or determining) the slip state of the rear wheels 13 and 13;
When the slip of the rear wheels 13 and 13 is estimated (predicted or judged) by the estimating means, the regenerative braking degree of the rear wheels 13 and 13 by the regenerative braking means is reduced from that in the non-estimated time, that is, braking that weakens the braking force. Control means (see step S11 of the flowchart shown in FIG. 3);
Doubles as
[0035]
  The braking control means described above increases the degree of braking of the front wheels by the front wheel braking means when the slip state is estimated (GT in the time chart shown in FIG. 7)._basereference).
  Further, when the slip state is not estimated, the above-mentioned braking control means includes the front wheels 9 by the clutch 5 as the switching means during at least a predetermined period during deceleration (the predetermined period means an initial deceleration where the deceleration request is relatively high). While the engagement with the engine 3 is cut off (see the clutch OFF portion showing the actual clutch ON / OFF state in the time chart in FIG. 7), at the time of estimation of the slip state, the front wheel 9 by the clutch 5 is at least in the predetermined period. Engagement with the engine 3 is executed (see the clutch ON and engine brake ON portions shown in the time chart in FIG. 7).
[0036]
  In addition, when the slip of the rear wheel 13 is detected by the above-described estimating means (see steps S9 and S10), the degree of braking by the regenerative braking means (feedback in FIG. 7) to suppress the longitudinal vibration of the vehicle according to the increase or decrease of the slip. The increase / decrease control timing of the control MT) and the increase / decrease control timing of the degree of braking by the front wheel braking means (see GT during feedback control in FIG. 7) are configured to differ by a predetermined time.
[0037]
  That is, in the time chart shown in FIG. 7, the state of change in the wavy waveform portion of the motor control torque MT and the state of change in the wavy waveform portion of the generator control torque GT in FIG. When the control shifts from the feedforward control to the feedback control, the control torque MT of the motor and the control torque GT of the generator during the feedback control are contradictory to each other. The increase / decrease control time is different from the GT increase / decrease control time by a predetermined time (see step S36 in the flowchart shown in FIG. 4).
[0038]
  The operation of the travel control apparatus for a hybrid vehicle configured as described above will be described in detail below with reference to a series of flowcharts shown in FIGS.
  In addition, the content of the code | symbol used for the following description is as follows.
[0039]
  α: accelerator opening
  Ne ... engine speed
  Nm ... motor speed
  SL ... Slip rate
  SLO: Control start threshold
  ΔSL: Rate of change of slip rate
  ΔSLO: Threshold of change rate of slip ratio
  SL_st... Initial slip rate
  ΔSL_st... Change rate of slip ratio at the beginning of slip
  ΔSL_sto... threshold
  SLα: Correction value
  SLA ... Target feedback value (Target slip ratio)
  SLD: Difference between the slip rate SL and the target feedback value SLA
  SLmax ... Maximum slip value
  SLmin ... Minimum slip value
  V ... Vehicle speed
  VB ... Vehicle speed
  MT: Control torque of rear wheel motor
  MT1, MT2 ... Required torque (However, MT1> MT2)
  MTb: Control torque base value of rear wheel motor
  MTα: Correction value
  T1 ... Counter that measures the time from the start of control
  T0: Control end value
  GT: Generator control torque
  GT_base... Control torque base value of generator
  PM2, IM2, DM2 ...
      The feedback gain of the rear wheel motor
      PM2 is proportional gain, IM2 is integral gain, DM2 is differential gain
  GT_{F / B}... Generator control torque feedback value
  PG, IG, FG ...
      Generator feedback gain, PG is proportional gain, IG is integral gain,
      DG is differential gain
      However, PG <PM2, IG <IM2, DG <DM2
[0040]
  In this embodiment, in order to converge the slip when the slip occurs, feedforward control is executed at the initial stage of the slip, and feedback control is executed at the latter stage of the slip.
[0041]
  [Feed-forward control at the initial stage of slip]
  In step S1 of the flowchart shown in FIG. 3, the ECU 20 waits for the start switch 29 to be turned on by the occupant, and proceeds to the next step S2 only when the start switch 29 is turned on.
[0042]
  In step S2, the ECU 20 inputs various necessary data from each sensor shown in FIG. Next, in step S3, the ECU 20 sets the basic operation mode described above based on the vehicle speed V, the accelerator opening degree α, the battery charge amount BC, and the like.
[0043]
  Next, in step S4, the ECU 20 calculates the basic control torque MT (specifically, the control torque base value MTb shown in FIG. 7) of the rear wheel motor 2. In the next step S5, the ECU 20 calculates the basic control torque ET of the engine 3. Is calculated.
[0044]
  As shown in FIG. 5, the basic control torque ET of the engine 3 is set from the vehicle speed V and the accelerator opening α, and as shown in FIG. 6, the basic control torque MT of the rear wheel motor 2 is for rotating at the motor rotational speed Nm. It is set from the electric energy.
[0045]
  Next, in step S6, the ECU 20 determines whether or not the vehicle is decelerating. When YES is determined (when decelerating), the process proceeds to the next step S7, whereas when NO is determined, the process skips to step S22.
[0046]
  In step S7, the ECU 20 determines whether or not the control torque MT of the rear wheel motor 2 is negative. When YES is determined (during regeneration of the rear wheel motor 2), the process proceeds to the next step S8, while when NO is determined. Skip to step S22.
[0047]
  The rear wheel motor 2 described above is driven by a three-phase AC power source obtained by converting the DC power source of the battery 1 using a chopper circuit and an inverter circuit, and the magnitude, frequency (that is, rotational speed) or phase of the current supplied to the rear wheel motor 2.TheInverter control is performed to adjust the control torque MT to obtain negative torque and regenerative energy.
[0048]
  In step S8 described above, the ECU 20 calculates the slip ratio (amount) SL of each wheel from the vehicle body speed VB estimated from each wheel speed and the current wheel speed of the drive wheels, that is, the rear wheels 13, 13, and this slip. A slip rate change rate ΔSL obtained by differentiating the rate SL is calculated.
[0049]
  Next, in step S9, the ECU 20 executes a low μ road determination. In this case, the ECU 20 changes the initial change rate ΔSL when the slip starts._st(However, the slip is a predetermined value SL shown in FIG._stChange rate at the initial stage of slip) and a threshold value ΔSL of a preset change rate_stoAnd the above change rate ΔSL_stTo determine whether the road is a low μ road or a high μ road.
[0050]
  That is, ΔSL_st≦ ΔSL_stoIs determined to be low μ,
          ΔSL_st> ΔSL_stoIs determined to be high μ.
  Note that instead of such low μ road determination, it may be determined whether or not it is raining by a sensor, and whether or not the vehicle is traveling on a slippery road may be predicted by a navigation device.
[0051]
  Next, in step S10, the ECU 20 determines whether or not the road is a low μ road based on the determination result of the previous step S9. When YES is determined, the process proceeds to the next step S11. When NO is determined, the process proceeds to another step S12. To do.
[0052]
  In step S11 described above, the ECU 20 corrects the control torque MT in response to the estimated slip state of the rear wheel during deceleration and regeneration of the rear wheel motor 2.
[0053]
  That is, the control torque base value MTb (negative value) is compensated.Positive valueA corrected control torque (MT = MTb + Mα) is obtained by adding Mα (see FIGS. 6 and 7) to weaken the braking force.
  This correction is executed by controlling the magnitude, frequency or phase of the current for the rear wheel motor 2.
[0054]
  Next, in step S13, the ECU 20 changes the threshold value for starting the ABS based on the low μ road determination (however, ABS in this case means slip control by the motor, unlike ABS by the conventional hydraulic brake). . That is, the corrected start threshold value (SLO = SLO + SLα) is obtained by adding the correction value SLα (see FIG. 8) to the preset control start threshold value SLO. This is effective for detecting slip early and improving running stability.
[0055]
  On the other hand, in step S12 described above, a preset control start threshold SLO is set to be used as it is.
  In step S10 described above, the low μ road determination is executed and the control torque MT of the rear wheel motor 2 is corrected (see step S11) when the determination is YES. Instead, a high μ road high speed is determined. However, in this case, it is desirable not to correct the ABS control start threshold value SLO in order to improve running stability.
[0056]
  Next, in step S14, the ECU 20 determines whether or not the clutch 5 is ON. When the determination is NO (when the clutch is OFF), the ECU 20 proceeds to the next step S15, and in this step S15, the ECU 20 turns on the clutch 5. On the other hand, when YES is determined in step S14 described above (when the clutch is ON), the process proceeds to another step S16, and in this step S16, the ECU 20 sets the front wheel motor regeneration mode to increase the braking force of the front wheels 9. In other words, generator control torque base value GT_base(Negative value, see time chart in FIG. 7).
[0057]
  Next, in step S17, the ECU 20 determines whether or not the slip ratio SL has fallen below a predetermined threshold value SLO (see FIG. 7). If YES is determined in step S17 that the slip ratio SL has fallen below the predetermined threshold value SLO, the process proceeds to the next step S18, and if NO determination (SL> SLO is determined), another step S23 (FIG. 4). Go to Reference).
[0058]
  In step S18, it is determined whether or not the rate of change ΔSL of the slip rate SL has fallen below a predetermined threshold value ΔSLO. If it is determined in step S18 that the rate of change ΔSL has fallen below the predetermined threshold value ΔSLO, the process proceeds to the next step S19. As shown in FIG. 7, the rate of change ΔSL of the slip rate SL represents the degree of change (slope) of the slip rate SL at the initial stage when the slip rate SL falls below the predetermined threshold value SLO. If it falls below the threshold value ΔSLO, it is determined that the slip ratio SL has changed suddenly. When it is determined in step S18 that the change rate ΔSL is not less than the predetermined threshold value ΔSLO, the deviation of the slip rate SL is small, so that the process proceeds to another step S20.
[0059]
  In step S19, the ECU 20 determines that the slip has a large deviation between the slip ratio SL and the predetermined threshold value SLO, and requests the control torque MT of the rear wheel motor 2 to turn the rear wheel 13 by weakening the braking force. The torque MT1 (positive value) is set (see FIG. 7).
[0060]
  On the other hand, since the deviation of the slip ratio SL is small in step S20, the ECU 20 sets the control torque MT of the rear wheel motor 2 to the required torque MT2 (however, MT2 <MT1 and a negative value in this embodiment). (See FIG. 7).
  Next, in step S21, the ECU 20 increments (counts up) the counter T1, and measures the time from the ABS control start time.
[0061]
  Next, in step S22, the ECU 20 adjusts the throttle opening in order to realize the control torque ET of the engine 3, and the air-fuel ratio A / F = 14.7 (theoretical air-fuel ratio) with respect to the detected intake air amount. ) Is set, and is supplied to each cylinder from the intake stroke to the compression stroke, and ignited by a spark plug in the vicinity of the compression top dead center TDC. Further, in order to realize the control torque MT of the rear wheel motor 2, the current value and frequency supplied from the inverter to the rear wheel motor 2 are adjusted. Further, the continuously variable transmission 6 and the generator 10 are driven.
[0062]
  [Feedback control of slip late stage]
  In step S23 of the flowchart shown in FIG. 4, the ECU 20 determines whether or not the counter T1 is zero. When the counter T1 is counting (NO determination), the ECU 20 proceeds to the next step S24, and the counter T1 is not counting. When T1 = 0 (YES determination), the process proceeds to another step S26.
[0063]
  In step S24 described above, the ECU 20 determines whether or not the counter T1 exceeds a predetermined value T0 (corresponding to the ABS control end time). When it is determined in step S24 that the counter T1 has exceeded the predetermined value T0, the control is terminated and the process proceeds to step S26.
[0064]
  When the counter T1 does not exceed the predetermined value T0 (NO determination), the control is being performed, so the process proceeds to step S25, and in this step S25, the ECU 20 determines whether braking is being performed.
[0065]
  If YES is determined in step S25 that the brake is being performed, the process proceeds to the next step S27, and if it is determined that the brake is not being performed (NO determination), the process proceeds to step S26 described above.
[0066]
  In step S26, the counter T1 is reset to zero in response to the counter T1 being zero, the counter T1 having passed the predetermined value T0 or being not braked, and then the process proceeds to step S22 in FIG.
[0067]
  On the other hand, in step S27, the ECU 20 sets a target slip ratio SLA (see FIG. 7) in order to converge the slip ratio SL.
  Next, in step S28, the ECU 20 calculates a difference SLD between the slip ratio SL and the target value SLA (SLD = SL-SLA).
[0068]
  Next, in step S29, the ECU 20 determines whether or not the maximum slip value SLmax (see FIG. 7). If YES is determined in step S29 that the maximum slip value SLmax is reached, the process proceeds to step S30. In step S30, the ECU 20 stores the latest maximum slip value SLmax in a predetermined area of the RAM 15. If it is determined in step S29 that the slip value is not the maximum slip value SLmax (NO determination), the process proceeds to step S31. In step S31, the ECU 20 determines whether or not the slip value is a minimum slip value SLmin (see FIG. 7). To do.
[0069]
  If YES is determined in step S31 that the slip value SLmin is the minimum slip value, the process proceeds to step S32. In step S32, the ECU 20 stores the latest minimum slip value SLmin in a predetermined area of the RAM 15. If it is determined in step S31 that the slip value is not the minimum slip value SLmin (NO determination), the process proceeds to step S33, and the feedback control value (torque) used for PID feedback control to the target slip ratio SLA of the rear wheel motor 2 is determined. A proportional gain PM2, an integral gain IM2, and a differential gain DM2 for calculating MT are set.
[0070]
  In step S34, the ECU 20 sets a feedback control value (torque) MT of the rear wheel motor 2 used for PID feedback control for converging the slip ratio SL to the target value SLA according to the difference SLD between the slip ratio SL and the target value SLA. Calculate. The feedback control value MT is calculated by the following [Equation 1] by setting the proportional gain PM2, the integral gain IM2, and the differential gain DM2 set in the previous step S33.
[0071]
  [Equation 1]
  MT = PM2 · SLD + IM2 · ∫ SLD + DM2 · d / dt · SLD
[0072]
  Next, in step S35, the ECU 20 determines whether or not the setting of the front wheel motor regeneration mode (see step S16) has been completed and the clutch 5 is ON. If YES, the process proceeds to the next step S36. If NO is determined, the process proceeds to another step S37.
[0073]
  In step S37 described above, the ECU 20 turns on the clutch 5, while in step S36 described above, the ECU 20 acts as a front wheel motor based on the feedback control value (torque) MT of the rear wheel motor 2 obtained in step S34. The control torque GT of the generator 10 is set.
[0074]
  This control torque GT is such that when the control torque MT of the rear wheel motor 2 is at a maximum value, the torque GT has a minimum value, and when the control torque MT of the rear wheel motor 2 is at a minimum value, the torque GT has a maximum value. Is set to be
  Therefore, first, based on the following [Equation 2], the control torque feedback value GT of the generator 10_{F / B}Ask for.
[0075]
  [Equation 2]
  GT_{F / B}= PG · (−SLD) + IG∫ (−SLD) + DG · d /_dt・ (-SLD)
    Where PG is proportional gain
          IG is the integral gain
          DG is differential gain
          SLD is the difference between slip ratio SL and target value SLA
    In addition, in order to moderate the braking change of the front wheels and improve the running stability,
    PG <PM2, IG <IM2, and DG <DM2.
[0076]
  Next, the control torque feedback value GT described above_{F / B}GT_baseTo obtain the control torque GT of the generator 10. That is, GT = GT_base+ GT_{F / B}
  Here, instead of the above-described configuration in which the feedback gain is set to PG <PM2, IG <IM2, and DG <DM2, the feedback gain is set to be the same as PG = PM2, IG = IM2, and DG = DM2. However, since the maximum output 10KW of the generator 10 is smaller than the maximum output 20KW of the rear wheel motor 2, the control torque GT itself is inevitably small.
[0077]
  Thus, when the control torque GT of the generator 10 is obtained in step S36, the control torque MT of the rear wheel motor 2 and the control torque GT of the generator 10 during feedback are obtained as shown in the time chart of FIG. Since the directions of torque change are opposite to each other, the longitudinal vibration of the vehicle by the slip suppression control can be suppressed by the braking control of the front wheels 9 by the torque GT and the braking control of the rear wheels 13 by the torque MT. After the processing in steps S36 and S37 in FIG. 4, the process proceeds to step S21 in FIG.
[0078]
  The overview of the travel control described with reference to the flowcharts of FIGS. 3 and 4 will be described with reference to the time chart shown in FIG. 7. At the time t1, deceleration starts, and at the time of deceleration, the clutch 5 is turned off and the rear wheels are turned off. A control torque base value MTb (negative value) of the motor 2 is set, and energy is recovered by regenerative driving of the motor 2.
[0079]
  When the low μ road is estimated at time t2, the braking force (regenerative braking force) of the rear wheel motor 2 is weakened by an amount corresponding to the correction value Mα, and the clutch 5 is detected at time t3 after a predetermined time lag by the clutch ON signal. Is actually connected, and while the clutch 5 is ON, the braking force of the front wheels 9 is increased by the engine brake, and the control torque GT of the generator 10 is set to the base value GT._baseAnd the regenerative energy generated by the regenerative drive of the generator 10 acting as a front wheel motor is recovered by this negative torque.
[0080]
  Further, in the feedforward control, the slip is converged by the required torques MT1 and MT2, while in the feedback control from the time point t4 to the time point t5, the control torque MT of the rear wheel motor 2 and the control torque GT of the generator 10 are set to these torques. Control is performed so that the directions of changes are opposite to each other, thereby suppressing longitudinal vibration of the vehicle. In other words, the time point of the maximum value of the torque MT and the time point of the maximum value of the torque GT during the feedback are different from each other by a predetermined time, and the time point of the minimum value of the torque MT and the time point of the minimum value of the torque GT are different from each other by a predetermined time. To control.
  In the time chart of FIG. 7, the values of torques MT and GT when no slip occurs are as indicated by imaginary lines x and y in FIG.
[0081]
  In step S36, the engine 10 is controlled so that the direction of the control torque GT of the generator 10 is opposite to the direction of the control torque MT of the rear wheel motor 2 during engine braking so as to suppress the longitudinal vibration of the vehicle. Instead of this configuration, even if the degree of the pumping loss of the engine is controlled by controlling the throttle valve or the external EGR valve (the pumping loss is reduced when the EGR valve is opened and the pumping loss is increased when the EGR is closed). Alternatively, the control torque for the front wheels 9 may be controlled by controlling the shift of the continuously variable transmission 6.
[0082]
  In short, the vehicle travel control apparatus of the above-described embodiment performs regenerative braking of the rear wheels 13 by the rear wheel driving means (see the rear wheel motor 2) for driving the rear wheels 13 of the vehicle and the motor 2 during deceleration. A vehicle travel control device comprising regenerative braking means (see steps S4 and S7) and front wheel braking means (see step S16) for applying braking force to the front wheels 9 of the vehicle when decelerating. When a slip of the rear wheel 13 is estimated by the estimating means (see steps S9 and S10) for estimating the state and the estimating means S9 and S10, the regenerative braking degree of the rear wheel 13 by the regenerative braking means S4 and S7 is not set. Braking control means (refer to step S11) for decreasing from the estimation time;The braking control means S11 increases the degree of braking of the front wheels 9 by the front wheel braking means S16 when the slip state is estimated, and also by the estimation means S9, S10. When the slip of the rear wheel 13 is detected, the control torque of the regenerative braking means S4 and S7 (see the torque MT during feedback control in FIG. 7) and the front wheel braking means in order to suppress the longitudinal vibration of the vehicle according to the increase or decrease of the slip. The increase / decrease control timing of the braking degree (see MT) by the regenerative braking means S4, S7 so that the direction of torque change of the control torque in S16 (see torque GT during feedback control in FIG. 7) is opposite to each other; The front wheel braking means is configured to vary the increase / decrease control timing of the braking degree (see GT) by S16 for a predetermined time.
[0083]
  With the above configuration, during normal deceleration as slip non-estimation (non-prediction or non-determination), the regenerative braking means S4 and S7 perform regenerative braking by the motor 2 that drives the rear wheels 13. The recovery of regenerative energy by the wheel motor 2 can be maximized.
[0084]
  Also,When the estimating means S9 and S10 estimate (predict or determine) the slip state of the rear wheel 13 driven by the motor, the braking control means S11 described above determines the degree of regenerative braking of the rear wheel 13 by the regenerative braking means S4 and S7. Since it is reduced compared to the estimated time (because the braking force is weakened), the slip stability of the rear wheel 13 can be suppressed and the running stability can be ensured when the slip is estimated.The
[0085]
  Further, the braking control meansS11Increases the degree of braking of the front wheels 9 by the front wheel braking means (see step S16) when the slip state is estimated (the torque GT shown in FIG. 7)._baseSetting and engine brake by clutch ON)From, decreaseWhen the slip state of the rear wheel 13 is estimated (predicted or determined) by the above-described estimating means S9 and S10 at the time of speed, the braking control meansS11Increases the degree of braking of the front wheels 9 by the front wheel braking means S16 that applies a braking force to the front wheels 9 of the vehicle.
  As a result, the degree of regenerative braking on the rear wheel 13 side is reduced at the time of slip estimation, but in this case, braking on the front wheels 9 can be performed and the braking performance of the vehicle during deceleration can be maintained.The
[0086]
  Moreover,When the slip of the rear wheel 13 is detected by the estimation means S9, S10, the degree of braking by the regenerative braking means S4, S7 (torque MT during feedback control in FIG. The reference increase / decrease control time is different from the increase / decrease control time of the braking degree by the front wheel braking means S16 (see torque GT during feedback control in FIG. 7) for a predetermined time. In other words, the directions of the torques MT and GT are opposite to each other.FromWhen the estimating means S9 and S10 detect the slip of the rear wheel 13, the regenerative braking means on the rear wheel 13 sideS4, S7Increase / decrease control time of braking degree byWhen,front wheel9Side braking meansS16The brake control is executed such that the braking degree increase / decrease control timing by the time differs by a predetermined time.
  As a result, the longitudinal vibration of the vehicle by the slip suppression control is caused between the front wheel 9 and the rear wheel 13.brakingIt can be suppressed by control.
[0087]
  FIG. 9 shows another embodiment of the vehicle travel control apparatus. In the embodiment shown in FIG. 9, the generator 10 and the power transmission means 38 in FIG. 1 are omitted, and a starter directly connected to the flywheel of the engine 3 is shown. A motor 39 is provided, and the starter motor 39 is set as a front wheel motor.The
[0088]
  Even in this configuration, the rear wheel driving means (see the rear wheel motor 2) for driving the rear wheel 13 of the vehicle and the main part of the flowcharts shown in FIGS. A vehicle equipped with regenerative braking means S4, S7 for regenerative braking of the rear wheel 13 by the motor 2 and front wheel braking means for applying a braking force to the front wheel 9 of the vehicle at the time of deceleration (see engine brakes or brake devices 16, 17). In the traveling control device, when the slip of the rear wheel 13 is estimated by the estimating means S9 and S10 for estimating the slip state of the rear wheel 13 and the estimating means S9 and S10, the rear wheel by the regenerative braking means S4 and S7. It is possible to configure a vehicle travel control device including the braking control means S11 that reduces the 13 regenerative braking degrees from the non-estimated time.
[0089]
  As a result, during normal deceleration as slip non-estimation (non-prediction or non-determination), the regenerative braking means S4 and S7 perform regenerative braking by the motor 2 that drives the rear wheels 13. The recovery of regenerative energy by the motor 2 can be maximized.
[0090]
  Also,When the estimating means S9 and S10 estimate (predict or determine) the slip state of the rear wheel 13 driven by the motor, the braking control means S11 described above determines the degree of regenerative braking of the rear wheel 13 by the regenerative braking means S4 and S7. Since it is decreased with respect to the estimation time, slip stability of the rear wheel 13 can be suppressed during slip estimation, and traveling stability can be ensured.Since other operations and effects are substantially the same as in the previous embodiment, the same reference numerals are given to the same parts in FIG.
[0091]
  In the correspondence between the configuration of the present invention and the above-described embodiment,
  The rear wheel drive means of this invention,Corresponding to the rear wheel motor 2 of the embodiment,
  Similarly,
  The regenerative braking means corresponds to steps S4 and S7 controlled by the ECU 20,
  The front wheel braking means corresponds to step S16,
  The estimation means corresponds to steps S9 and S10,
  The braking control means corresponds to step S11,
  Front wheel motor corresponds to generator 10 or starter motor 39Yes,
  The present invention is not limited to the configuration of the above-described embodiment.
[0092]
  For example, in the above embodiment, a hybrid vehicle having a 4WD configuration provided with the engine 3 and the rear wheel motor 2 is illustrated. However, since this has no internal combustion engine, the vehicle is driven by the front wheel motor and the rear wheel motor. Of course, the present invention may be applied to an electric vehicle so-called EV.
[0093]
【The invention's effect】
  According to the present invention, when the rear wheel slip is estimated (including prediction or determination) in the regenerative braking unit that performs the regenerative braking of the rear wheel by the rear wheel motor during deceleration, the regenerative control unit By reducing the degree of regenerative braking of the rear wheels from that at the time of non-estimation, the recovery of regenerative energy by the rear wheel motor is maximized at the time of normal deceleration when slip does not occur, and at the time of occurrence of slip or slip When the possibility of occurrence is large, the effect of suppressing the slip of the rear wheel isIn addition, when the slip of the rear wheel is detected by the estimating means, the direction of torque change between the control torque of the regenerative braking means and the control torque of the front wheel braking means is opposite to each other in order to control the longitudinal vibration of the vehicle according to the increase or decrease of the slip. Since the braking degree increase / decrease control time by the regenerative braking means and the braking degree increase / decrease control time by the front wheel braking means are different by a predetermined time so as to be in the direction, it is possible to suppress the longitudinal vibration of the vehicle by the slip suppression control. There is an effect that can be done.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a mechanical configuration of a hybrid vehicle provided with a travel control device of the present invention.
FIG. 2 is a block diagram showing the electrical configuration.
FIG. 3 is a flowchart showing slip suppression control by an ECU.
FIG. 4 is a flowchart continued from FIG. 3;
FIG. 5 is a diagram showing engine basic control torque corresponding to vehicle speed and accelerator opening.
FIG. 6 is a diagram showing the relationship between the motor rotation speed and the basic control torque of the motor.
FIG. 7 is a time chart showing slip suppression control.
FIG. 8 is a partially enlarged view of FIG.
FIG. 9 is a block diagram showing another embodiment of a hybrid vehicle equipped with the travel control device of the present invention.
[Explanation of symbols]
  2 ... Rear wheel modeT
  9…front wheel
  10 ... Generator (front wheel motor)
  13 ... Rear wheel
  39 ... Starter motor (front wheel motor)
  S4, S7 ... Regenerative braking means
  S9, S10 ... estimation means
  S11: Braking control means
  S16: Front wheel braking means

Claims (1)

Rear wheel drive means for motor driving the rear wheels of the vehicle;
Regenerative braking means for performing regenerative braking of the rear wheels by the motor during deceleration;
A vehicle travel control device comprising front wheel braking means for applying braking force to the front wheels of the vehicle during deceleration,
Estimating means for estimating the slip state of the rear wheel;
Braking control means for reducing the degree of regenerative braking of the rear wheels by the regenerative braking means when it is estimated by the estimating means from the non-estimated time ,
The braking control means increases the degree of braking of the front wheels by the front wheel braking means when the slip state is estimated,
When the rear wheel slip is detected by the estimating means, the direction of torque change between the control torque of the regenerative braking means and the control torque of the front wheel braking means is opposite to each other in order to suppress the longitudinal vibration of the vehicle according to the increase or decrease of the slip. The vehicle travel control device is configured so that the braking degree increase / decrease control time by the regenerative braking means is different from the braking degree increase / decrease control time by the front wheel braking means by a predetermined time .

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