JP2010023734A - Driving power distribution control device of front and rear-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving power distribution control device of a front and rear-wheel drive vehicle for achieving preferable turning corresponding to operation of a driver. <P>SOLUTION: The driving power distribution control device includes: a turning determination means 80 for determining turning traveling of a vehicle 8; a posture determination means 82 for determining over-steer or under-steer when the turning determination means 80 determines the turning traveling of the vehicle 8; and a driving force distribution controlling means 86 for controlling output to the rear wheel 32 side in a coupling 26 based on the comparison result between an actual yaw direction and a steering direction, and an accelerator operation state using the predetermined relation, when the posture determination means 82 determines the over-steer or under-steer of the vehicle 8. Output to an auxiliary driving wheel side is controlled by determining intention of the driver based on the comparison result between the actual yaw direction and the steering direction, and the accelerator operation state, thus attaining control of the vehicle posture finely reflecting the intention of the driver. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a driving force distribution control device for front and rear wheel drive vehicles, and more particularly to an improvement for realizing a suitable turn according to a driver's operation.

  For example, it is arranged in series with the propeller shaft in order to select the four-wheel drive state and the two-wheel drive state, or to control the power distribution ratio between the front wheels and the rear wheels in the four-wheel drive state. 2. Description of the Related Art A front and rear wheel drive vehicle including a driving force distribution device that can control distribution of a driving force generated by a driving force source to main driving wheels and auxiliary driving wheels, such as an electromagnetic clutch device is known. In such a vehicle, with respect to the control of the driving force distribution device, the amount of driving force distribution to each wheel is controlled based on information detected by various sensors provided in the vehicle. For example, in Patent Document 1, regarding a driving force distribution control device for a vehicle, a differential value of a steering operation amount of a driver is detected at the time of steering turning, and the driving force transmitted to the auxiliary driving wheel as the differential value increases. A technique for increasing the distribution ratio is disclosed.

JP 2007-55476 A JP 2006-256456 A JP 2004-114794 A

  However, in the control based on the conventional technology as described above, when oversteer or understeer occurs during turning of the vehicle, the vehicle posture that the driver wants to establish by the driving operation and the target in the control are set. As a result, there is a possibility that drivability is lowered due to inconsistency with the vehicle posture. Further, under traveling conditions in which the yaw fluctuation of the vehicle is relatively large, there is a risk that a vehicle behavior that repeats oversteer and understeer near the neutral steer due to the drive force distribution control to the sub drive wheels by the drive force distribution device may occur. was there. For this reason, there has been a demand for the development of a driving force distribution control device for front and rear wheel drive vehicles that realizes a suitable turn according to the operation of the driver.

  The present invention has been made in the background of the above circumstances, and an object of the present invention is to provide a driving force distribution control device for front and rear wheel drive vehicles that realizes a suitable turn in accordance with a driver's operation. There is.

  In order to achieve such an object, the gist of the present invention is that a front / rear equipped with a driving force distribution device capable of controlling the distribution of the driving force generated by the driving force source to the main driving wheel and the sub driving wheel. A driving force distribution control device for a wheel drive vehicle, wherein a turning determination unit that determines turning traveling of the vehicle and a vehicle oversteer or understeering when the turning determination unit determines turning traveling of the vehicle. In the case where the vehicle oversteer or understeer is determined by the attitude determination means and the attitude determination means, based on the comparison result between the actual yaw direction and the steering direction and the accelerator operation state based on a predetermined relationship, The driving force distribution device includes driving force distribution control means for controlling the output to the auxiliary driving wheel side.

  According to this configuration, the turn determination unit that determines the turning travel of the vehicle, the posture determination unit that determines the oversteer or understeer of the vehicle when the turning determination unit determines the turning travel of the vehicle, and the posture thereof. When the determination unit determines that the vehicle is oversteered or understeered, the sub-drive in the driving force distribution device is determined based on the comparison result between the actual yaw direction and the steering direction and the accelerator operation state based on a predetermined relationship. Since it is equipped with a driving force distribution control means that controls the output to the wheel side, the driver's intention is judged from the comparison result of the actual yaw direction and the steering direction and the accelerator operation state, and the secondary drive By controlling the output to the wheel side, it is possible to control the vehicle attitude that precisely reflects the driver's intention. That is, it is possible to provide a driving force distribution control device for front and rear wheel drive vehicles that realizes a suitable turn according to the driver's operation.

  Here, preferably, when the vehicle oversteer is determined by the posture determination unit, the driving force distribution control unit is different from an actual yaw direction and a steering direction and an accelerator depression operation is performed. In this case, the output to the auxiliary drive wheel side in the driving force distribution device is controlled so that the change gradient at the time of output reduction becomes gentler than the change gradient at the time of output increase to the auxiliary drive wheel side. is there. In this way, it is possible to maintain the vehicle posture by suppressing the yaw change in the direction in which the vehicle is understeered, and it is possible to realize a suitable turning travel.

  Preferably, the driving force distribution control unit is configured such that when the vehicle oversteer is determined by the posture determination unit, the actual yaw direction is different from the steering direction and the accelerator depressing operation is not performed. In the driving force distribution device, the output to the auxiliary driving wheel side is increased and then the output is gradually reduced to zero with a gentle change gradient compared to the change gradient when the output is increased. It controls the output to the wheel side. In this way, it is possible to maintain the vehicle posture by suppressing the yaw change in the direction in which the vehicle is understeered, and it is possible to realize a suitable turning travel.

  Preferably, the driving force distribution control unit is configured to distribute the driving force when the actual yaw direction and the steering direction are the same when the vehicle oversteer is determined by the attitude determination unit. The output to the auxiliary drive wheel side in the apparatus is set to zero. In this way, it is possible to realize suitable spin traveling or vehicle stop reflecting the driver's intention.

  Preferably, the vehicle includes a load determination unit that determines a magnitude relationship between loads applied to the main driving wheel and the sub driving wheel, and the driving force distribution control unit determines whether the vehicle understeer is determined by the attitude determination unit. In the case where the actual yaw direction and the steering direction are the same and the accelerator depressing operation is performed, the main drive wheel and the sub drive determined by the load determination means from a predetermined relationship. Based on the magnitude relationship of the load applied to each wheel, the output to the auxiliary driving wheel side in the driving force distribution device is controlled. In this way, when it is determined that the grip of the main drive wheel is insufficient, the distribution of the drive force to the sub drive wheel is suppressed to ensure the turning force by the main drive wheel, If the main drive wheel has sufficient gripping force, the load distribution amount of the main drive wheel and the sub drive wheel can be adjusted so that a more suitable turning is realized by distributing the drive force to the sub drive wheel. Accordingly, a suitable vehicle posture correction can be realized.

  Preferably, the driving force distribution control unit is configured to reduce the output to the sub driving wheel side as the load applied to the main driving wheel determined by the load determining unit decreases. This controls the output to the auxiliary drive wheel side. In this way, when it is determined that the grip of the main drive wheel is insufficient, the distribution of the drive force to the sub drive wheel is suppressed to ensure the turning force by the main drive wheel, If the main drive wheel has sufficient gripping force, the load distribution amount of the main drive wheel and the sub drive wheel can be adjusted so that a more suitable turning is realized by distributing the drive force to the sub drive wheel. Accordingly, a suitable vehicle posture correction can be realized.

  Preferably, the driving force distribution control means has an actual yaw direction and a steering direction that are the same and an accelerator depression operation is not performed when the vehicle understeer is determined by the attitude determination means. In this case, the output to the auxiliary driving wheel side in the driving force distribution device is set to zero. In this way, it is possible to realize suitable travel or vehicle stop reflecting the driver's intention.

  Preferably, the driving force distribution control means is configured such that when the attitude determining means determines that the vehicle is understeered and the actual yaw direction is different from the steering direction, the driving force distribution control means The output to the drive wheel side is zero. In this way, it is possible to suppress unnecessary execution of control in the driving force distribution device.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 illustrates a configuration of a driving force transmission device 10 provided in a front and rear wheel drive vehicle 8 (hereinafter simply referred to as a vehicle 8) based on a front engine front wheel drive (FF) to which the present invention is preferably applied. FIG. As shown in FIG. 1, in such a driving force transmission device 10, torque generated by the engine 12 that is a driving force source is a torque converter 14, a transmission 16, a front wheel differential device 18, and left and right 1. While being transmitted to a pair of left and right front wheels 22 via a pair of front wheel axles 20, a propeller shaft 24 that is a driving force transmission shaft and an electronically controlled coupling 26 that is a front and rear wheel driving force distribution device (hereinafter simply referred to as coupling 26). ) Is transmitted to the left and right pair of rear wheels 32 via the rear wheel differential device 28 and the left and right pair of rear wheel axles 30. Further, an electronic control unit 34 for controlling the coupling 26 is provided. That is, the driving force transmission device 10 shown in FIG. 1 distributes the torque generated by the engine 12 as a driving force source to the front wheels 22 as the main driving wheels and the rear wheels 32 as the auxiliary driving wheels according to the traveling state. 1 is an example of a drive system of an electronically controlled torque split four-wheel drive vehicle.

  The engine 12 is, for example, an internal combustion engine such as a gasoline engine or a diesel engine that generates driving force by combustion of fuel injected in a cylinder. The torque converter 14 includes, for example, a pump impeller coupled to the crankshaft of the engine 12, a turbine impeller coupled to the input shaft of the transmission 16, and a transmission case via a one-way clutch. And a stator impeller fixed to the hydrodynamic power transmission device that transmits power through the fluid between the pump impeller and the turbine impeller. The transmission 16 includes, for example, a plurality of friction engagement elements, and selectively establishes a plurality of transmission ratios according to a combination of engagement or release of the friction engagement elements, and inputs from the input shaft. This is an automatic transmission that shifts and outputs the generated driving force.

  The electronic control unit 34 is a so-called microcomputer that includes a CPU, a ROM, a RAM, an input / output interface, and the like, and executes signal processing according to a program stored in advance in the ROM while using a temporary storage function of the RAM. Yes, for example, transmission torque control of the coupling 26 by controlling the command value of the current supplied to the electromagnetic solenoid 62 provided in the coupling 26, that is, front and rear wheel driving by the driving force transmission device 10 Perform various controls. In order to execute such control, the power transmission device 10 detects a steering speed of a wheel speed sensor 36 that detects actual rotational speeds of the pair of left and right front wheels 22 and rear wheels 32 and a steering wheel (not shown). A rudder angle sensor 38, an accelerator opening sensor 40 that detects an accelerator opening corresponding to a depression amount of an accelerator pedal (not shown), and a yaw sensor 42 that detects an actual lateral direction G (acceleration) of the front and rear wheel drive vehicle 8; And various sensors such as a front / rear G sensor 44 for detecting an actual front / rear direction G (acceleration) of the front / rear wheel drive vehicle 8 are provided. Signals indicating the rotational speeds of the wheels 22 and 32 from each sensor, steering A signal indicating the steering angle, a signal indicating the accelerator opening, a signal indicating the lateral G of the vehicle, a signal indicating the front and rear G of the vehicle, and the like are supplied to the electronic control unit 34. It is adapted to be.

  FIG. 2 is a schematic cross-sectional view illustrating a configuration example of the coupling 26. As shown in FIG. 2, the coupling 26 includes a first housing 60 which is a cover member formed coaxially and integrally with the propeller shaft 24, and an electromagnetic solenoid 62. A second housing 64 fixed to the circumferential side, an output shaft 66 serving as a central axis or a rear wheel side rotational axis disposed coaxially with the first housing 60 and relatively rotatable about its axis, and A control cam 68 arranged coaxially with the output shaft 66 so as to be relatively rotatable about its axis, and a control clutch 70 for preventing or slipping relative rotation between the first housing 60 and the control cam 68. And the second housing 64, the clutch plate constituting the control clutch 70 is clamped to be coaxial with the output shaft 66. An armature 72, which is an annular iron piece disposed in a relatively movable manner, a main clutch 74 for preventing or slipping relative rotation between the first housing 60 and the output shaft 66, and the first housing 60. And a main cam 76 disposed coaxially with the output shaft 66 so as not to be rotatable about its axis and to be relatively movable in the axial direction in order to clamp the clutch plate constituting the main clutch 74 therebetween. , And is configured. A plurality of recesses corresponding to the respective cam surfaces are formed on opposite sides of the control cam 68 and the main cam 76, and the control cam 68 and the main cam 76 are inserted into the recesses. A plurality of balls 78 are disposed on the surface.

  In the coupling 26 configured as described above, when the electromagnetic solenoid 62 is in a non-excited state, both the control clutch 70 and the main clutch 74 are in a non-engaged state. However, when the electromagnetic solenoid 62 is in an excited state, a magnetic flux is generated around the electromagnetic solenoid 62, so that the armature 72 is attracted to the second housing 64 side. Then, the control clutch 70 is engaged or slipped according to the control current to the electromagnetic solenoid 62. After the control clutch 70 is engaged, when a rotational speed difference occurs between the control cam 68 and the main cam 76, the ball 78 is pressed against the inclined surface of the recess in the control cam 68 and pressed toward the main cam 76 side. As a result, the main cam 76 is pressed toward the propeller shaft 24 to engage the main clutch 74, and the driving force of the propeller shaft 24 is transmitted to the output shaft 66.

  The transmission torque transmitted by the coupling 26 is proportionally determined by a control current supplied to the electromagnetic solenoid 62, for example, as shown in FIG. That is, when the current supplied to the electromagnetic solenoid 62 is relatively small, the force with which the armature 72 is attracted to the second housing 64 is relatively weak, and the engagement force of the control clutch 70 is relatively small. The rotational speed difference between the control cam 68 and the main cam 76 becomes small, and the force with which the main cam 76 is pressed against the propeller shaft 24 becomes relatively weak and the transmission torque becomes relatively small. When the current supplied to the electromagnetic solenoid 62 is relatively large, the force with which the armature 72 is attracted to the second housing 64 is relatively strong and the engagement force of the control clutch 70 is relatively large. The rotational speed difference between the cam 68 and the main cam 76 becomes large, so that the main cam 76 is Transmission torque is relatively strong force pressed against the shaft 24 side is relatively large. When the current supplied to the electromagnetic solenoid 62 exceeds a predetermined value, the driving force is transmitted to the front and rear wheels in a state close to a directly connected four-wheel drive vehicle. With the above configuration, the ratio of the driving force transmitted to the rear wheel 32 with respect to the total driving force output from the transmission 16 is continuously controlled within a range of zero to 0.5.

  FIG. 4 is a functional block diagram for explaining the main part of the control function provided in the electronic control unit 34. The electronic control device 34 is provided with a storage device 88 that stores relationships used in various controls described below, and includes a turning determination unit 80, a posture determination unit 82, a load determination unit 84, and the like shown in FIG. For example, the driving force distribution control means 86 executes the following control using various relationships stored in advance in the storage device 88.

  The turning determination unit 80 determines whether the vehicle 8 is turning. For example, from a predetermined relationship, the rotational speeds of the wheels detected by the wheel speed sensor 36, that is, the front wheels 22 and the rear wheels 32, the steering angle of the steering wheel detected by the steering angle sensor 38, and the Based on the lateral direction G of the vehicle 8 detected by the yaw sensor 42, it is determined whether or not the vehicle 8 is turning. More simply, when the steering angle of the steering wheel detected by the steering angle sensor 38 or the angle with respect to the straight traveling direction such as the output signal of the power steering corresponding to the steering angle is equal to or greater than a predetermined value, the vehicle 8 It is also possible to determine whether the vehicle is turning. The vehicle 8 may be determined to turn when the lateral direction G of the vehicle 8 detected by the yaw sensor 42 is equal to or greater than a predetermined value.

  When the turning determination unit 80 determines that the vehicle 8 is turning, the posture determination unit 82 determines a vehicle posture of the vehicle 8, that is, oversteer or understeer. For example, from a predetermined relationship, the steering angle of the steering wheel detected by the steering angle sensor 38, the lateral direction G of the vehicle 8 detected by the yaw sensor 42, and the vehicle speed detected by a vehicle speed sensor (not shown) The target yaw rate of the vehicle 8 is calculated on the basis of the rotation speed of each wheel detected by the wheel speed sensor 36, and the target yaw rate and the yaw sensor 42 detect the target yaw rate. A deviation from the actual yaw rate is calculated, and oversteer or understeer of the vehicle 8 is determined according to the deviation. When the deviation between the target yaw rate of the vehicle 8 calculated as described above and the actual yaw rate detected by the yaw sensor 42 is within a range of zero to error, the vehicle posture of the vehicle 8 is Neutral steer is determined.

  The load determination means 84 determines the magnitude relationship between the loads applied to the front wheel 22 as the main driving wheel and the rear wheel 32 as the auxiliary driving wheel. For example, from a predetermined relationship, based on the initial load distribution which is a set value and the front-rear direction G of the vehicle 8 detected by the front-rear G sensor 44, the load distribution amount (the front wheel 22 and the rear wheel 32) ( Distribution ratio). The load determination means 84 may calculate the load distribution ratio of the front wheels 22 and the rear wheels 32 as a specific numerical value, and any one of a plurality of steps determined in advance with respect to the magnitude relationship thereof. It may be what determines whether it is included in. Furthermore, the magnitude may be simply compared, such as determining whether or not the load on the front wheel 22 is greater than the load on the rear wheel 32.

  The driving force distribution control means 86 controls the distribution of the driving force output by the engine 12 to the front wheels 22 as main driving wheels and the rear wheels 32 as auxiliary driving wheels via the coupling 26. To do. That is, by controlling the control current to the electromagnetic solenoid 62 provided in the coupling 26, the output of the driving force output by the engine 12 to the rear wheel 32 side is controlled. Further, when the vehicle 8 is turning, that is, when the turning determination unit 80 determines that the vehicle 8 is turning, yaw control of the vehicle 8 is realized by performing such driving force distribution control. Hereinafter, front and rear wheel driving force distribution control by the driving force distribution control means 86 when the vehicle 8 is turning will be described in detail with reference to FIGS.

  FIG. 5 is a diagram for explaining a state where the running posture of the vehicle 8 is not determined to be neutral steer. As shown in FIG. 5, when the vehicle posture is once disturbed during the turning of the vehicle 8, there is a case where a mismatch between the vehicle posture intended by the driver and the target vehicle posture is caused by the control. is there. For example, in the example shown in FIG. 5, the vehicle posture (direction) corresponding to the neutral steer in turning of the vehicle 8 is indicated by a broken line, but the vehicle posture that was neutral steer at time t0 is Understeer (in a state where it bulges outward with respect to the turning trajectory), oversteering at a time t2 (in a state where it wraps inward with respect to the turning trajectory), and again understeering at time t3, oversteering near the neutral steer. And vehicle behavior that repeats understeer. This is because, in a conventional driving force distribution control device for front and rear wheel drive vehicles, when feedback control (PID control) is performed according to the deviation between the target yaw rate and the actual yaw rate, the driving force distribution control device has a relatively large yaw change. This can be generated by driving force control, and the 4WD output (output to the auxiliary drive wheel side) direction is constant with the yaw change, so if there is a relatively sudden change in the output, the reverse direction It is considered that the vehicle behavior is such that oversteer and understeer are repeated as described above.

  In the conventional technique, for example, as shown in FIG. 6, when a deviation occurs between the target yaw value and the measured yaw value, the sub-stitch is canceled as shown in FIG. Driving force distribution control to the driving wheel side, that is, the rear wheel 32 side is performed. That is, regardless of whether the vehicle 8 is oversteered or understeered, a four-wheel drive state is established by increasing the amount of driving force distribution to the rear wheel 32 side, and the turning performance of the vehicle 8 is improved. Then, control is performed such that the amount of driving force distribution to the rear wheel 32 side is reduced to shift to neutral steer. At this time, there is no difference in the change gradient between when the driving force distribution amount to the rear wheel 32 increases and when it decreases, and the driving force distribution amount to the rear wheel side 32 changes relatively abruptly especially when the amount decreases. There are times when it is made to be. Here, for example, if a sudden change (abrupt decrease) in output to the rear wheel 32 occurs when the vehicle posture returns from oversteer to neutral steer, it is possible that yaw in the reverse direction occurs and understeer occurs. is there.

  The driving force distribution control means 86 determines the result of comparison between the actual yaw direction and the steering direction and the accelerator from a predetermined relationship when the attitude determination means 82 determines oversteer or understeer of the vehicle 8. Based on the operation state, the output to the rear wheel 32 side in the coupling 26 is controlled. The steering direction serving as a reference for this determination is preferably the actual steering (rotation) direction of the steering wheel detected by the steering angle sensor 38. The change direction of the target yaw rate calculated as described above may be used as a criterion for determination. For example, as shown in FIGS. 8 and 9, the driving force distribution control unit 86 is configured to detect the actual yaw direction detected by the yaw sensor 42 and the steering angle sensor 38 for each of the oversteer and understeer of the vehicle 8. Depending on whether or not the actual steering direction detected by the vehicle is the same, and whether or not an accelerator depression operation (accelerator on) is detected by the accelerator opening sensor 40, in each individual control mode. Driving force distribution control in the ring 26 is executed. Hereinafter, these controls will be described.

  As shown in FIG. 8, the driving force distribution control unit 86 determines the actual yaw direction detected by the yaw sensor 42 and the rudder when the oversteer of the vehicle 8 is determined by the attitude determination unit 82. If the actual steering direction detected by the angle sensor 38 is different and an accelerator pedal depression operation (accelerator on) (not shown) is detected by the accelerator opening sensor 40, predetermined vehicle posture holding control is executed. . In this vehicle attitude holding control, the actual yaw rate detected by the yaw sensor 42 and the like is feedback-controlled using the target yaw rate calculated as described above as a target value, and also to the rear wheel 32 side, which is the auxiliary driving wheel. The output to the rear wheel 32 side of the coupling 26 is controlled so that the change gradient (change rate) at the time of output reduction becomes gentler than the change gradient (change rate) at the time of output increase. In other words, the vehicle posture holding control is performed with a change gradient when the actual yaw rate detected by the yaw sensor 42 or the like changes in a direction away from the target yaw rate when the vehicle 8 is oversteered. In comparison, the output to the rear wheel 32 side of the coupling 26 is controlled so that the gradient of change when changing in the approaching direction becomes gradual.

  FIG. 10 is a diagram for explaining yaw rate feedback control (PID control) according to the prior art, and FIG. 11 is a diagram for explaining yaw rate feedback control by the driving force distribution control means 86 of this embodiment. As shown in FIG. 10, in the conventional yaw rate feedback control, there is no difference in the change gradient between the increase and decrease of the driving force distribution amount to the auxiliary drive wheel, that is, the rear wheel 32 side, and the target yaw rate is adjusted. A general feedback control with the target value is executed. However, as described above, when a sudden change (abrupt decrease) in output to the rear wheel 32 occurs when the vehicle posture returns from oversteer to neutral steer, yaw in the reverse direction occurs as shown in FIG. Understeer may occur, which may result in vehicle behavior in which oversteer and understeer occur alternately. On the other hand, in the yaw rate feedback control by the driving force distribution control means 86 of the present embodiment, the change gradient at the time of output reduction becomes gentler than the change gradient at the time of output increase to the rear wheel 32 side which is the auxiliary drive wheel. Thus, the feedback control subjected to the filter processing is executed. This filtering process is performed, for example, with respect to the output value to the coupling 26 (electromagnetic solenoid 62) calculated by normal feedback control based on the actually detected yaw rate when the output to the rear wheel 32 increases. The change gradient at the time of output reduction is subjected to a smoothing process (delay process) at a predetermined rate (a fixed rate or a rate that changes according to the gradient). Alternatively, a smoothing process is performed on the actually detected yaw rate (actual yaw value) that is input for the feedback process (with respect to the change gradient when the output increases, the change gradient when the output decreases) The same control may be realized. By such vehicle attitude maintenance control, when returning from oversteer to neutral steer, the occurrence of yaw in the reverse direction is suppressed and understeer is suppressed.

  Further, as shown in FIG. 8, the driving force distribution control unit 86 is configured to detect the actual yaw direction detected by the yaw sensor 42 and the like when the vehicle attitude determination unit 82 determines that the vehicle 8 is oversteered. When the actual steering direction detected by the rudder angle sensor 38 is different and the depression operation of an accelerator pedal (not shown) is not detected by the accelerator opening sensor 40 (accelerator off), a predetermined output filter process is executed. . In this output filtering process, the output to the rear wheel 32, which is the auxiliary drive wheel, is once increased, and then the output is gradually reduced to zero with a gentle change gradient compared to the change gradient when the output is increased. The output to the rear wheel 32 side in the coupling 26 is controlled. The change gradient at the time of output reduction in the output filter processing is preferably a predetermined ratio (fixed ratio or gradient) with respect to the output value to the coupling 26 (electromagnetic solenoid 62), similarly to the processing at the time of accelerator on described above. The rate of the annealing is changed at a rate that changes according to By such output filter processing, when returning from oversteer to neutral steer or stopping, the occurrence of yaw in the reverse direction is suppressed and understeer is suppressed.

  Further, as shown in FIG. 8, the driving force distribution control unit 86 is configured to detect the actual yaw direction detected by the yaw sensor 42 and the like when the vehicle attitude determination unit 82 determines that the vehicle 8 is oversteered. When the actual steering direction detected by the rudder angle sensor 38 is the same, the 4WD output control in the coupling 26 is turned off, that is, the output to the rear wheel 32 that is the auxiliary drive wheel (drive force distribution). (Quantity) is zero. When oversteer of the vehicle 8 is determined by the attitude determination unit 82, if the actual yaw direction and the actual steering direction detected by the rudder angle sensor 38 coincide with each other, the driver enters a turning track. On the other hand, it is considered that the vehicle 8 is intended to drive the vehicle 8 further inward or to stop the vehicle as a result of the spin drive. In such a case, a suitable spin traveling can be realized by setting the output to the rear wheel 32 side to zero.

  In addition, as shown in FIG. 9, the driving force distribution control unit 86 is configured to detect the actual yaw direction detected by the yaw sensor 42 and the like when the understeer of the vehicle 8 is determined by the attitude determination unit 82. When the actual steering direction detected by the rudder angle sensor 38 is the same and the accelerator pedal position sensor 40 detects that the accelerator pedal (not shown) is depressed (accelerator on), predetermined vehicle attitude correction control is performed. Execute. The vehicle posture correction control is performed based on the magnitude relationship between the loads applied to the front wheel 22 and the rear wheel 32 determined by the load determination means 84 based on a predetermined relationship, and the rear wheel 32 in the coupling 26. The output to the side is controlled.

  FIG. 12 is a diagram showing an example of the relationship between the yaw deviation used for the yaw control according to the prior art and the output (driving force distribution amount) to the rear wheel 32 side. In the conventional control, as shown in FIG. 12, the control is performed such that the output to the rear wheel 32, which is the auxiliary drive wheel, increases as the yaw deviation, that is, the difference between the measured yaw rate and the target yaw rate increases. On the other hand, FIG. 13 is a diagram showing an example of the relationship between the magnitude relationship between the front and rear wheel loads used for the yaw control by the driving force distribution control means 86 of this embodiment and the output correction gain. This relationship preferably defines an output correction gain for correcting the output to the rear wheel 32 to be smaller as the load applied to the front wheel 22 is smaller. For example, the relationship is stored in advance in the storage device 88. is there. From the relationship shown in FIG. 13, the driving force distribution control means 86 is based on the magnitude relationship between the loads applied to the front wheel 22 and the rear wheel 32 determined by the load determination means 84. The output correction gain related to the output control to is calculated. That is, the output (driving force distribution value) to the rear wheel 32 calculated based on the yaw deviation from the relationship shown in FIG. 12 is based on the front and rear wheel load magnitude relationship from the relationship shown in FIG. By multiplying the calculated output correction gain, a control command value to the coupling 26 (control current to the electromagnetic solenoid 62) is determined. When the load of the front wheel 22 is relatively small, it is considered that the grip of the front wheel 22 is insufficient. In such a case, if the output to the rear wheel 32 side is increased, the turning force is reduced. Thus, it is conceivable that suitable turning cannot be realized (pushing under). In the control of this embodiment, when it is determined that the load applied to the front wheel 22 is relatively small and the grip is insufficient, the distribution of the driving force to the rear wheel 32 side is suppressed to While ensuring the turning force by the front wheel 22, when the load applied to the front wheel 22 is relatively large and has a sufficient grip force, a more suitable turning is realized by distributing the driving force to the rear wheel 32 side. As described above, a suitable vehicle posture correction can be realized in accordance with the front and rear wheel load distribution amount.

  In addition, as shown in FIG. 9, the driving force distribution control unit 86 is configured to detect the actual yaw direction detected by the yaw sensor 42 and the like when the understeer of the vehicle 8 is determined by the attitude determination unit 82. If the actual steering direction detected by the rudder angle sensor 38 is the same and the accelerator pedal depression operation of an accelerator pedal (not shown) is not detected by the accelerator opening sensor 40 (accelerator off), the 4WD output in the coupling 26 The control is turned off, that is, the output (driving force distribution amount) to the rear wheel 32 which is the auxiliary driving wheel is set to zero. Further, when understeer of the vehicle 8 is determined by the attitude determination means 82, the actual yaw direction detected by the yaw sensor 42 and the actual steering direction detected by the rudder angle sensor 38 are different. Similarly, the output to the rear wheel 32 side in the coupling 26 is set to zero (no care).

  FIG. 14 is a flowchart for explaining a main part of the front / rear wheel driving force distribution control through the coupling 26 by the electronic control unit 34, which is repeatedly executed at a predetermined cycle.

  First, in a step (hereinafter, step is omitted) S1 corresponding to the operation of the turning determination means 80, the rotation of each of the front wheel 22 and the rear wheel 32 detected by the wheel speed sensor 36 from a predetermined relationship. Based on the speed, the steering angle of the steering wheel detected by the steering angle sensor 38, and the lateral direction G of the vehicle 8 detected by the yaw sensor 42, it is determined whether or not the vehicle 8 is turning. To be judged. If the determination in S1 is negative, the routine is terminated after the driving force distribution control is performed in normal time, that is, during non-turning, but the determination in S1 is positive. Is based on the steering angle detected by the steering angle sensor 38, the lateral direction G of the vehicle 8 detected by the yaw sensor 42, the vehicle speed detected by the vehicle speed sensor, and the like in S3. Thus, the target yaw rate of the vehicle 8 is calculated, and the deviation between the target yaw rate and the actual yaw rate detected by the yaw sensor 42 is calculated. Next, in S4, based on the deviation calculated in S3, it is determined whether or not the state of the vehicle 8 is oversteer. If the determination in S4 is negative, the processing from S10 is executed, but if the determination in S4 is affirmative, in S5, the actual yaw direction detected by the yaw sensor 42 and the like and the It is determined whether or not the actual steering direction detected by the steering angle sensor 38 is the same. If the determination in S5 is affirmative, the routine is terminated after the engagement state of the coupling 26 is controlled so that the output to the rear wheel 32 becomes zero in S6. If the determination in S5 is negative, it is determined in S7 whether or not an accelerator depression operation is detected by the accelerator opening sensor 40. If the determination at S7 is affirmative, the routine is terminated after the above-described vehicle attitude maintenance control (yaw rate feedback control) is executed at S8, but if the determination at S7 is negative, In S9, after the output filter processing control described above is executed, this routine is terminated.

  In S10, it is determined whether the state of the vehicle 8 is understeer based on the deviation calculated in S3. If the determination in S10 is negative, the routine is terminated after the normal control is executed in S11 assuming that the state of the vehicle 8 is neutral steer, but the determination in S10 is affirmed. In S12, it is determined whether or not the actual yaw direction detected by the yaw sensor 42 and the like and the actual steering direction detected by the steering angle sensor 38 are the same. If the determination in S12 is negative, the routine is terminated after the engagement state of the coupling 26 is controlled so that the output to the rear wheel 32 becomes zero in S13. If the determination in S12 is affirmative, in S14, it is determined whether or not an accelerator depression operation is detected by the accelerator opening sensor 40. If the determination in S14 is negative, the processing from S13 is executed, but if the determination in S14 is affirmative, it is predetermined in S15 corresponding to the operation of the load determination means 84. From the relationship, the load distribution amount (distribution ratio) for the front wheels 22 and the rear wheels 32 is calculated based on the initial load distribution which is a set value and the front-rear direction G of the vehicle 8 detected by the front-rear G sensor 44. The Next, in S16, the above-described vehicle attitude correction control (yaw rate feedback control) is executed based on the front and rear wheel load distribution calculated in S15, and then this routine is terminated. In the above control, S3, S4, and S10 correspond to the operation of the posture determination means 82, and S5 to S9 and S12 to S16 correspond to the operation of the driving force distribution control means 86, respectively.

  Thus, according to the present embodiment, when the turning determination unit 80 (S1) for determining turning of the vehicle 8 and the turning determination unit 80 determines turning of the vehicle 8, the vehicle When the oversteer or understeer of the vehicle 8 is determined by the posture determination means 82 (S3, S4, and S10) for determining whether the vehicle 8 is oversteered or understeered, from a predetermined relationship. Based on the comparison result between the actual yaw direction and the steering direction and the accelerator operation state, driving force distribution control means 86 (S5 to S9, S12 to S16) for controlling the output of the coupling 26 to the rear wheel 32 side. Therefore, the driver's intention is determined based on the comparison result between the actual yaw direction and the steering direction and the accelerator operation state. Determined to be to control the output to the auxiliary drive wheel side can be realized to control the vehicle attitude to finely reflect the intention of the driver. That is, it is possible to provide a driving force distribution control device for the front and rear wheel drive vehicle 8 that realizes a suitable turn according to the driver's operation.

  Further, the driving force distribution control means 86, when the oversteer of the vehicle 8 is determined by the attitude determination means 82, the actual yaw direction and the steering direction are different and the accelerator depression operation is being performed. This controls the output of the coupling 26 to the rear wheel 32 side so that the change gradient at the time of output reduction becomes gentler than the change gradient at the time of output increase to the rear wheel 32 side. Therefore, the vehicle posture can be maintained by suppressing the yaw change in the direction in which the vehicle 8 is understeered, and a suitable turning travel can be realized.

  Further, the driving force distribution control means 86, when the oversteer of the vehicle 8 is determined by the attitude determination means 82, the actual yaw direction and the steering direction are different and the accelerator depression operation is not performed. In this case, after the output to the rear wheel 32 is increased, the rear wheel in the coupling 26 is gradually decreased to zero with a gentle change gradient compared to the change gradient when the output is increased. Since the output to the side 32 is controlled, the vehicle posture can be maintained by suppressing the yaw change in the direction in which the vehicle 8 is understeered, and a suitable turning travel can be realized.

  In addition, the driving force distribution control unit 86 determines that the coupling 26 is in the case where the actual yaw direction and the steering direction are the same when the attitude determination unit 82 determines the oversteer of the vehicle 8. Since the output to the rear wheel 32 is zero, it is possible to realize a suitable spin traveling or vehicle stop reflecting the driver's intention.

  In addition, load determining means 84 (S15) for determining the magnitude relationship between the loads applied to the front wheels 22 and the rear wheels 32 is provided, and the driving force distribution control means 86 is configured to detect understeer of the vehicle 8 by the attitude determining means 82. When the determination is made, if the actual yaw direction and the steering direction are the same and the accelerator depressing operation is being performed, the front wheel 22 determined by the load determination means 84 from a predetermined relationship. Since the output to the rear wheel 32 side of the coupling 26 is controlled based on the magnitude relationship between the loads applied to the rear wheel 32 and the rear wheel 32, it is determined that the grip of the front wheel 22 is insufficient. In this case, the distribution of the driving force to the rear wheel 32 side is suppressed to ensure the turning force by the front wheel 22, while the front wheel 22 has a sufficient grip force. In such a case, a suitable vehicle posture correction is realized according to the load distribution amount of the front wheel 22 and the rear wheel 32, such that a more suitable turning is realized by distributing the driving force to the rear wheel 32 side. be able to.

  In addition, the driving force distribution control unit 86 is configured to reduce the output to the rear wheel 32 side as the load applied to the front wheel 22 determined by the load determination unit 84 decreases. Since the output to the side is controlled, when it is determined that the grip of the front wheel 22 is insufficient, the distribution of the driving force to the rear wheel 32 side is suppressed and the turning force by the front wheel 22 is controlled. On the other hand, when the front wheel 22 has a sufficient gripping force, the driving force is distributed to the rear wheel 32 side to realize a more suitable turning, so that the front wheel 22 and the rear wheel 32 can be turned. A suitable vehicle posture correction can be realized in accordance with the load distribution amount.

  In addition, the driving force distribution control means 86 has the same yaw direction and steering direction as those in the case where the understeer of the vehicle 8 is determined by the attitude determination means 82 and the accelerator depression operation is not performed. In this case, since the output to the rear wheel 32 side in the coupling 26 is zero, it is possible to realize a suitable running or vehicle stop reflecting the driver's intention.

  In addition, the driving force distribution control unit 86 determines that the rear side of the coupling 26 is different when the actual yaw direction and the steering direction are different when the posture determination unit 82 determines that the vehicle 8 is understeered. Since the output to the wheel 32 side is zero, it is possible to suppress the execution of unnecessary control in the coupling 26.

  The preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and may be implemented in other modes.

  For example, a coupling 26 as a driving force distribution device provided in the front and rear wheel drive vehicle 8 of the above-described embodiment is provided in series with the propeller shaft 24 and is connected to the rear wheel differential device 28 from the propeller shaft 24. Although the driving force distributed to the input shaft is controlled, the driving force distributed to the input shaft of the front wheel differential device provided in parallel to the propeller shaft 24 is controlled. Of course, the present invention may be applied to a vehicle including the front and rear wheel driving force distribution device. Furthermore, it goes without saying that the present invention is also suitably applied to front and rear wheel drive vehicles having the rear wheels as main drive wheels and the front wheels as auxiliary drive wheels.

  Further, the coupling 26 as a driving force distribution device provided in the front and rear wheel drive vehicle 8 of the above-described embodiment is an electromagnetic clutch whose engagement state is controlled according to a control current supplied to the electromagnetic solenoid 62. However, the present invention is also suitably applied to a vehicle in which another type of engagement device such as a hydraulic clutch or a magnetic powder clutch is provided as a driving force distribution device.

  In addition, although not illustrated one by one, the present invention is implemented with various modifications within a range not departing from the gist thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a skeleton diagram illustrating a configuration of a driving force transmission device provided in a front and rear wheel drive vehicle based on front engine front wheel drive to which the present invention is preferably applied. It is a schematic sectional drawing explaining the structural example of the electronically controlled coupling with which the driving force transmission apparatus of FIG. 1 was equipped. It is a graph which shows the relationship between the control current supplied to the coil with which the electronic control coupling of FIG. 2 was provided, and transmission torque. It is a functional block diagram explaining the principal part of the control function with which the electronic control apparatus for controlling the electronic control coupling of FIG. 2 was equipped. It is a figure explaining the state where the running posture of a vehicle is not determined to neutral steer. It is a figure explaining a mode that a measurement yaw value fluctuates when deviation arises between a target yaw value and a measurement yaw value in conventional control. In conventional control, when deviation arises between a target yaw value and an actual measurement yaw value, it is a figure explaining driving force distribution control for canceling the deviation and making it shift to neutral steer. In the control of the present embodiment, when the vehicle is in an oversteer state, it is a diagram illustrating a control mode that is individually determined based on a comparison result between an actual yaw direction and a steering direction and an accelerator operation state. In the control of this embodiment, when the vehicle is in an understeer state, it is a diagram illustrating a control mode that is individually determined based on a comparison result between an actual yaw direction and a steering direction and an accelerator operation state. It is a figure explaining the feedback control (PID control) of the yaw rate by a prior art. It is a figure explaining the feedback control of the yaw rate by control of a present Example. It is a figure which shows an example of the relationship between the yaw deviation used for the yaw control by a prior art, and the output to the sub drive wheel side. It is a figure which shows an example of the relationship between the magnitude relationship of the front-and-rear wheel load used for yaw control of a present Example, and an output correction gain. It is a flowchart explaining the principal part of the front-and-rear wheel driving force distribution control via the electronic control coupling by the electronic control apparatus of FIG.

Explanation of symbols

8: Front and rear wheel drive vehicle 12: Engine (drive power source)
22: Front wheel (main drive wheel)
26: Electronically controlled coupling (driving force distribution device)
32: Rear wheel (sub-drive wheel)
80: Turning determination means 82: Attitude determination means 84: Load determination means 86: Driving force distribution control means

Claims (8)

A driving force distribution control device for front and rear wheel drive vehicles provided with a driving force distribution device capable of controlling the distribution of the driving force generated by the driving force source to the main driving wheel and the sub driving wheel,
Turning determination means for determining turning traveling of the vehicle;
Posture determination means for determining oversteer or understeer of the vehicle when the turning determination means determines that the vehicle is turning; and
In the case where oversteering or understeering of the vehicle is determined by the posture determination means, based on a predetermined relationship, based on a comparison result between an actual yaw direction and a steering direction and an accelerator operation state, A driving force distribution control device for front and rear wheel drive vehicles, comprising: a driving force distribution control means for controlling output to the auxiliary driving wheel side.   The driving force distribution control unit is configured to perform the sub-driving when the actual yaw direction is different from the steering direction and the accelerator depressing operation is performed when the vehicle oversteer is determined by the attitude determination unit. The output to the auxiliary drive wheel side in the driving force distribution device is controlled so that the change gradient at the time of output reduction becomes gentler than the change gradient at the time of output increase to the wheel side. Driving force distribution control device for front and rear wheel vehicles.   The driving force distribution control means determines that the auxiliary driving is performed when the actual yaw direction is different from the steering direction and the accelerator depressing operation is not performed when the vehicle oversteer is determined by the attitude determination means. After increasing the output to the wheel side, the output to the sub-drive wheel side in the driving force distribution device is such that the output is gradually reduced to zero with a gentle change gradient compared to the change gradient when the output is increased. The driving force distribution control device for a front and rear wheel vehicle according to claim 1 or 2, which is to be controlled.   The driving force distribution control means, when the oversteer of the vehicle is determined by the attitude determination means, and when the actual yaw direction and the steering direction are the same, The driving force distribution control device for a front and rear wheel vehicle according to any one of claims 1 to 3, wherein the output to the vehicle is zero. Load determining means for determining a magnitude relationship of loads applied to the main drive wheel and the sub drive wheel,
The driving force distribution control means is predetermined when the actual yaw direction and the steering direction are the same and the accelerator depression operation is performed when the vehicle understeer is determined by the attitude determination means. From the determined relationship, the output to the sub driving wheel side in the driving force distribution device is controlled based on the magnitude relationship of the load applied to each of the main driving wheel and the sub driving wheel determined by the load determining means. The driving force distribution control device for a front and rear wheel vehicle according to any one of claims 1 to 4.   The driving force distribution control means moves to the auxiliary driving wheel side in the driving force distribution device so that the smaller the load applied to the main driving wheel determined by the load determining means, the smaller the output to the auxiliary driving wheel side. The driving force distribution control device for a front and rear wheel vehicle according to claim 5, which controls the output of the vehicle.   The driving force distribution control means determines that the driving force distribution control means determines that when the understeer of the vehicle is determined by the attitude determination means, the actual yaw direction and the steering direction are the same and the accelerator depressing operation is not performed. The driving force distribution control device for a front and rear wheel vehicle according to any one of claims 1 to 6, wherein an output to the auxiliary driving wheel side in the force distribution device is zero.   The driving force distribution control means outputs an output to the auxiliary driving wheel side in the driving force distribution device when the actual yaw direction and the steering direction are different in the case where understeer of the vehicle is determined by the attitude determination means. The driving force distribution control device for a front and rear wheel vehicle according to any one of claims 1 to 7, wherein is set to zero.

Images