JP2018158643A - Drive force distribution unit control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of difference in drive force distribution caused by the difference in hysteresis of left and right frictional clutch at transition to a straight travel after turning by applying a difference in left and right drive force distribution.SOLUTION: When an excitation current I of a pair of an electromagnetic coupling (a frictional clutch) is changed to an equal distribution excitation current Ic in order to transition from an unequal distribution state to an equal distribution state, the excitation current is returned to an equal distribution excitation current Ic after changed to a transitional excitation current Id for an electromagnetic coupling at a point A where increase-decrease directions of a controlling torque characteristic (solid line) and excitation current I are opposite, and thus a hysteresis is reduced a value around equal distribution target torque Tc. An electromagnetic coupling at a point B where the increase-decrease direction of the excitation current I is the same as the controlling torque characteristic is appropriately controlled at equal distribution target torque Tc by the equal distribution excitation current Ic. With this, the transmission torque of both electromagnetic couplings is controlled at or around the equal distribution target torque Tc, making left and right drive force distribution approximately equal, thus improving straight-travel performance.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a driving force distribution unit that adjusts the driving force distribution to the left and right wheels using a pair of friction clutches, and in particular, a control device that can appropriately control the driving force distribution regardless of the hysteresis of the transmission torque of the friction clutch. It is about.

  There is known a driving force distribution unit in which a friction clutch is provided between a driving force input unit and left and right wheels. The device described in Patent Document 1 is an example, and an electromagnetic friction clutch is used, and by controlling control signals (excitation currents) for controlling the transmission torque of the pair of friction clutches, The driving force distribution for the wheels is adjusted. Patent Document 1 describes a case in which a driving force distribution unit is provided on the side of a sub driving wheel to which a part of driving force is transmitted in a front and rear wheel driving vehicle. And a technique for improving the turning performance is described.

WO2012 / 005256 publication

  By the way, in such a conventional driving force distribution unit, torque characteristics when changing the transmission torque by increasing the control signal of the friction clutch, and torque characteristics when changing the transmission torque by decreasing the control signal, May cause hysteresis (torque difference). In this case, even if the target value of the control signal is the same, the transmission torque may vary due to hysteresis depending on the approach (increase or decrease) to the target value. That is, when the vehicle turns straight with a difference in the driving force distribution for the left and right wheels and turns straight, and when equalizing the driving force distribution for the left and right wheels, the control signal of the left and right friction clutches is reversed, the control signal Even if the target value is the same, the transmission torques of the left and right friction clutches are different due to hysteresis, and there is a possibility that the difference in the driving force distribution between the left and right wheels may cause the straightness of the vehicle to be impaired.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is to increase or decrease the control signal when shifting to straight running after turning with a difference in the driving force distribution for the left and right wheels. The difference in hysteresis between the left and right friction clutches is to prevent a difference in driving force distribution and to impair the straight running performance.

  In order to achieve this object, the first invention is provided in a driving force distribution unit in which a friction clutch is provided between the driving force input unit and each of the left and right wheels, and the transmission torque of the pair of friction clutches is obtained. In the control device of the driving force distribution unit that adjusts the driving force distribution to the left and right wheels by controlling the control signals to be controlled, respectively, (a) the pair of friction clutches are torques on the increase side of the control signal. (B) the control signal of the pair of friction clutches is one of the increase side torque characteristic and the decrease side torque characteristic. Based on a predetermined control torque characteristic composed of one of them, each is controlled to a signal value that provides a predetermined target torque, and (c) is applied to each of the left and right wheels. The control signals of the pair of friction clutches are equally distributed as the target torque in order to shift from an unequal distribution state with different driving force distribution to an equal distribution state in which the driving force distribution for the left and right wheels is equal to each other. When changing to the equally distributed signal value obtained based on the control torque characteristic so as to obtain the target torque, the friction clutch whose control signal increase / decrease direction is opposite to the control torque characteristic is An equal distribution shift control unit is provided that changes the control signal beyond the equal distribution signal value to a via signal value determined on the opposite side and then returns to the equal distribution signal value.

  A second aspect of the invention is a control device for a driving force distribution unit according to the first aspect of the present invention. (A) In the unequal distribution state, the control signal of the friction clutch on either the left or right wheel side is the equal distribution target torque. And a control signal for the friction clutch on the other wheel side is controlled by the equal distribution target so that a larger target torque is obtained. In a state where the small torque signal value determined based on the control torque characteristic is obtained so that a small target torque smaller than the torque can be obtained, (b) the equal distribution transition control unit is configured to control the one wheel. The control signal for the friction clutch on the side is changed from the large torque signal value to the equally distributed signal value, and the control signal for the friction clutch on the other wheel side is changed from the small torque signal value to the equally distributed signal value. For the friction clutch whose control signal increase / decrease direction is opposite to the control torque characteristic, the control signal is changed to the route signal value and then returned to the equally distributed signal value. To do.

  According to a third aspect of the present invention, in the control device for the driving force distribution unit according to the first or second aspect of the invention, the route signal value is opposite to the transmission torque of the friction clutch exceeding the equally distributed target torque regardless of the hysteresis. It is a signal value that can be changed up to.

  In such a driving force distribution unit control device, when changing the control signal of the pair of friction clutches to the equal distribution signal value in order to shift from the unequal distribution state to the equal distribution state, the control torque characteristics are For friction clutches where the direction of increase / decrease of the control signal is opposite, the control signal is changed over the equally distributed signal value to the via signal value determined on the opposite side and then returned to the equally distributed signal value. Hysteresis is reduced, and the transmission torque can be brought close to the equally distributed target torque. On the other hand, for a friction clutch whose control signal has the same direction of increase / decrease as the control torque characteristic, the transmission torque is controlled according to the control torque characteristic, so that it is appropriately controlled to the equally distributed target torque according to the equal distribution signal value. As a result, the transmission torque of each of the left and right friction clutches is equal to or near the equally distributed target torque regardless of the hysteresis, the driving force distribution to the left and right wheels is substantially equal, and the driving force distribution is different. The straightness of the rear vehicle is improved. Also, since the transmission torque is controlled based on the control torque characteristics on either the increase or decrease side of the control signal, the transmission torque is controlled using both the increase and decrease torque characteristics of the control signal. Control becomes easier compared to the case of doing so.

  In the second invention, the control signal of the friction clutch on one wheel side is increased or decreased from the large torque signal value to the equally distributed signal value, and the control signal of the friction clutch on the other wheel side is changed from the small torque signal value to the equally distributed signal value. For friction clutches whose control signal increase / decrease direction is opposite to that of the control torque characteristic when the control signal is changed to In spite of the fact that the direction of increase / decrease of the control signal of the friction clutch is opposite, the deviation of the transmission torque due to hysteresis is suppressed, and the driving force distribution to the left and right wheels is substantially equal, improving the straightness of the vehicle.

  In the third aspect of the invention, the route signal value is a signal value that can change the transmission torque of the friction clutch beyond the equally distributed target torque to the opposite side regardless of the hysteresis, and thereafter returns to the equally distributed signal value. As a result, the direction of change of the transmission torque of the friction clutch is reversed and changed in the same increase / decrease direction as the control torque characteristics so as to approach the equally distributed target torque, so that the hysteresis of the transmission torque can be appropriately reduced. .

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 a front engine front wheel drive to which the present invention is applied, and is a diagram illustrating a main part of a control system. It is a schematic sectional drawing explaining the specific example of the electromagnetic coupling with which the driving force distribution unit of FIG. 1 was equipped. FIG. 3 is a diagram illustrating an example of a torque characteristic that is a relationship between an excitation current and a transmission torque of the electromagnetic coupling of FIG. 2, and is a diagram illustrating hysteresis that occurs between an increase side and a decrease side of the excitation current. 2 is a flowchart for specifically explaining the operation of an equal distribution shift control unit functionally included in the electronic control device of FIG. 1. FIG. 5 is an example of a time chart for explaining a change in transmission torque of left and right electromagnetic couplings when equal distribution shift control is performed according to the flowchart of FIG. 4. It is a figure explaining the other Example of this invention, and is a flowchart corresponding to FIG. FIG. 7 is a diagram for explaining a control torque characteristic used in the embodiment of FIG. 6, which is the same torque characteristic as FIG. 3, except that a decreasing torque characteristic indicated by a solid line is used as a control torque characteristic. It is an example of the time chart explaining the change of the transmission torque of the left and right electromagnetic coupling when equal distribution shift control is performed according to the flowchart of FIG.

  The present invention is applied to, for example, a driving force distribution unit that is provided on the side of a sub driving wheel to which a part of driving force is transmitted in front and rear wheel driving vehicles and adjusts the left and right driving force distribution of the sub driving wheel. In the case where the driving force distribution unit is provided on the main driving wheel side to which the driving force is always transmitted in the front and rear wheel drive vehicle, the same applies. Even in a two-wheel drive vehicle such as a front wheel drive vehicle or a rear wheel drive vehicle, the present invention can be applied when a drive force distribution unit for adjusting the drive force distribution of the left and right wheels is provided. As the friction clutch, for example, an electromagnetic coupling in which a transmission torque is adjusted by engagement of a friction plate by controlling an excitation current as a control signal is preferably used, but a single plate type or a multi-plate type that is frictionally engaged by hydraulic pressure. It is also possible to use a hydraulic friction clutch or the like. It is also possible to use a magnetic powder type electromagnetic coupling. The hysteresis of the transmission torque of the friction clutch is caused by, for example, the residual magnetism of an electromagnetic solenoid, but when a fastening force is generated using a cam mechanism such as a ball cam, there is a possibility that the hysteresis is caused by the friction of the cam mechanism. .

  The friction clutch has hysteresis between the torque characteristic on the increase side (rise side) of the control signal and the torque characteristic on the decrease side (decrease side) of the control signal, and one of the torque characteristics is controlled by the torque for control. The driving force distribution is controlled using the characteristic. For example, the change characteristic of the transfer torque when increasing the control signal (increase side torque characteristic) is used as the control torque characteristic, but the change characteristic of the transfer torque when decreasing the control signal (decrease side torque characteristic) is used for control. It can also be used as a torque characteristic. This torque characteristic may be such that the transmission torque increases (rises) as the control signal increases, or the transmission torque decreases (decreases) as the control signal increases. The increase side torque characteristic and the decrease side torque characteristic are determined on the basis of increase / decrease in the control signal. It is desirable that the pair of friction clutches have the same torque characteristics with the same standard and can be controlled using a common control torque characteristic. However, friction clutches having different torque characteristics with different standards may be employed.

  When shifting from the unequal distribution state to the equal distribution state, a friction clutch whose control signal increases and decreases in the opposite direction from the control torque characteristic is, for example, not used when the increasing torque characteristic is used as the control torque characteristic. In this friction clutch, the control signal needs to be decreased in order to change the transmission torque in the equally distributed state from the equally distributed target torque. Further, when the decreasing torque characteristic is used as the control torque characteristic, the friction clutch needs to increase the control signal in order to change from the transmission torque in the unequal distribution state to the equal distribution target torque. In other words, it is a friction clutch in which the transmission torque cannot be appropriately controlled by hysteresis only by changing to an equally distributed signal value determined based on the control torque characteristic. The equally-distributed target torque is variably set according to, for example, the required driving force or the shared driving force on the auxiliary driving wheel side, but a constant value may be determined in advance.

  In the unequal distribution state, for example, the control signal of one of the friction clutches is controlled to a large torque signal value determined so as to obtain a larger target torque larger than the equal distribution target torque, and the other friction clutch The control signal is controlled to a small torque signal value determined so that a small target torque smaller than the equally distributed target torque can be obtained, and the present invention is suitably applied to the case of shifting from the unequal distribution state to the equal distribution state. Although applied, for example, the transmission torque of one of the friction clutches may be substantially equal to the equally distributed target torque in an unequal distribution state. The large-side target torque and the small-side target torque are variably set according to a predetermined distribution ratio based on, for example, the equally-distributed target torque, that is, the shared driving force on the auxiliary drive wheel side. If it is a constant value, a constant value can be determined for the large target torque and the small target torque. The small target torque may be 0 (transfer torque = 0).

  The via signal value controlled by the equal distribution transition control unit is preferably a signal value that can change the transmission torque of the friction clutch to the opposite side beyond the equal distribution target torque regardless of hysteresis, but at least equal If the signal value is on the opposite side beyond the distribution signal value, the deviation of the transmission torque due to hysteresis can be suppressed even on the near side of the equally distributed target torque. The route signal value is determined in advance by an experiment or the like so that the transmission torque becomes the substantially equal distribution target torque by changing the control signal to the route signal value and then returning to the equally distribution signal value. This route signal value is determined by, for example, a data map using the target torque in the unequal distribution state (starting torque at the time of transition to equal distribution) and the equal distribution target torque as parameters. It is also possible to calculate the via torque from the starting torque and the equally distributed target torque at the time of transition to the equal distribution, and obtain the via signal value of the control signal from the via torque based on the control torque characteristics.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified for explanation, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a skeleton diagram illustrating a configuration of a driving force transmission device 10 provided in a front and rear wheel drive vehicle based on a front engine front wheel drive (FF) to which the present invention is applied. It is the figure shown collectively. In this driving force transmission device 10, torque (driving force) generated by the engine 12 that is a driving force source is a torque converter 14, a transmission 16, a front wheel differential 18, and left and right front wheel axles 20 l, It is transmitted to the left and right front wheels 22l and 22r, which are main drive wheels, via 20r. Further, a part of the driving force transmitted to the front wheel differential unit 18 is transmitted from the transfer shaft 23 through the propeller shaft 24, which is the driving force transmission shaft, the driving force distribution unit 26, and the left and right rear wheel axles 30l and 30r. Then, it is transmitted to the left and right rear wheels 32l and 32r which are auxiliary driving wheels (also referred to as auxiliary driving wheels). The engine 12 is an internal combustion engine such as a gasoline engine or a diesel engine, and the transmission 16 is a stepped transmission such as a planetary gear type or a continuously variable transmission such as a belt type.

  The driving force distribution unit 26 is for distributing the driving force transmitted from the propeller shaft 24 to the left and right rear wheels 32l and 32r at a predetermined distribution ratio, and a pair of bevel gears (or a hypoid gear pair) 34, A rear wheel side input shaft 38 to which driving force is transmitted from the propeller shaft 24 via 36, and a pair of electromagnetic couplings 40l disposed between the rear wheel side input shaft 38 and the left and right axles 30l, 30r, 40r. The pair of electromagnetic couplings 40l and 40r (hereinafter simply referred to as the electromagnetic coupling 40 unless otherwise distinguished) are the same standard products and have the same torque characteristics, and the transmission torque T is controlled by the electronic control unit 50. By individually controlling the driving force distribution to the left and right rear wheels 32l and 32r, respectively, can be controlled continuously or stepwise. That is, it is possible to control the shared driving force on the rear wheel side by the transmission torque T of the pair of electromagnetic couplings 40, and the driving force transmission device 10 uses the torque generated by the engine 12 as the driving force source, It is an example of a drive system of an electronically controlled torque split type four-wheel drive vehicle that is distributed to front wheels 221 and 22r that are main drive wheels and rear wheels 321 and 32r that are auxiliary drive wheels according to a traveling state. The electromagnetic coupling 40 corresponds to a friction clutch, and the rear wheel side input shaft 38 corresponds to a driving force input unit.

  FIG. 2 is a schematic cross-sectional view specifically explaining an example of the electromagnetic coupling 40r on the right rear wheel 32r side, and an electromagnetic solenoid that generates a magnetic force in accordance with a control signal supplied from the electronic control unit 50, that is, an excitation current I. 70. The electromagnetic solenoid 70 is disposed on a differential carrier 72 attached to the vehicle body. On the other hand, a bottomed cylindrical case 74 is coaxially and integrally fixed to the rear wheel side input shaft 38, and a control clutch 76, a cam mechanism 78, and a main clutch 80 are arranged in the case 74. It is installed. The control clutch 76 is a friction engagement type clutch disposed between a cylindrical control cam 82 and a case 74 that are concentrically rotatable with the case 74, and is armature by the electromagnetic force of the electromagnetic solenoid 70. When 84 is attracted, it is frictionally engaged with a fastening force corresponding to the electromagnetic force, and torque is transmitted from the case 74 to the control cam 82 according to the fastening force. The cam mechanism 78 has a plurality of balls 88 interposed between the control cam 82 and the pressing plate 86, and the control cam 82 rotates relative to the pressing plate 86 according to the torque transmitted from the control clutch 76. As a result, the pressing plate 86 is pressed toward the main clutch 80 by the change in the depth of the cam groove in which the ball 88 is disposed. The control cam 82 is axially defined by a differential carrier 72 via a thrust bearing 90, while the pressing plate 86 is inserted into the right rear wheel axle 30r inserted into the control cam 82 so as to be relatively rotatable. It is spline-fitted so that it cannot rotate relative to the shaft and can move in the axial direction. The main clutch 80 is a friction engagement type clutch disposed between the case 74 and the right rear wheel axle 30r. The main clutch 80 is frictionally engaged with the pressing load of the pressing plate 86, that is, the fastening force corresponding to the electromagnetic force of the electromagnetic solenoid 70. The driving force is transmitted from the rear wheel side input shaft 38 to the right rear wheel axle 30r according to the fastening force. In other words, the driving force is transmitted from the rear wheel side input shaft 38 to the right rear wheel axle 30r with the transmission torque T corresponding to the excitation current I of the electromagnetic solenoid 70. The cam mechanism 78 functions as a booster mechanism that amplifies the pressing load of the pressing plate 86. Note that the electromagnetic coupling 40l on the left wheel 32l side is configured to be symmetrical to the electromagnetic coupling 40r, that is, is disposed in the opposite direction, and has substantially the same configuration and function. Yes.

  In the electromagnetic coupling 40 configured as described above, the transmission torque T is changed as shown in FIG. That is, as the excitation current I increases, the transmission torque T increases as shown by a solid line, while as the excitation current I decreases, the transmission torque T decreases as shown by a broken line, and the excitation current I decreases. The change characteristic (decrease torque characteristic) of the transmission torque T when (decrease) is larger than the change characteristic (increase torque characteristic) of the transfer torque T when the excitation current I is increased (increased). It has a hysteresis. Such hysteresis is caused by, for example, residual magnetism of the electromagnetic solenoid 70 or friction of the cam mechanism 78.

  The electronic control unit 50 functions as a controller for controlling the driving force distribution to the left and right rear wheels 32l and 32r via the driving force distribution unit 26. A microcomputer having a CPU, a ROM, a RAM, an input / output interface, etc. A predetermined signal processing relating to driving force distribution is executed according to a program stored in advance in the ROM while utilizing the temporary storage function of the RAM. The electronic control unit 50 can also perform output control of the engine 12, shift control of the transmission 16, and the like. The electronic control device 50 is connected to an accelerator operation amount sensor 60, a wheel speed sensor 62, a rudder angle sensor 64, a yaw sensor 66, a front / rear G sensor 68, and the like, and the accelerator operation amount θacc, which is the operation amount of the accelerator pedal, Various information necessary for control, such as front wheel 22l, 22r and rear wheel 32l, 32r wheel rotational speed ωi, steering wheel steering angle Φ, vehicle yaw angular velocity Y, vehicle longitudinal direction G (acceleration), etc. It has come to be. A vehicle speed V is calculated from the wheel rotation speed ωi.

  The electronic control device 50 functionally includes a driving force distribution control unit 52 and an equal distribution shift control unit 54 in connection with the control of the driving force distribution unit 26. The driving force distribution control unit 52 controls the driving force distribution of the front and rear wheels and the driving force distribution of the left and right rear wheels 32l and 32r, and the transmission torque T of the left and right electromagnetic couplings 40 so as to obtain a predetermined driving force distribution. To control. In controlling the transmission torque T, one of the increase side torque characteristic and the decrease side torque characteristic shown in FIG. 3 is set as the control torque characteristic, and a predetermined transmission torque T is obtained based on the control torque characteristic. Thus, the excitation current I of each electromagnetic coupling 40 is controlled. In this embodiment, the increasing torque characteristic indicated by the solid line in FIG. 3 is used as the control torque characteristic. The electronic control device 50 functions as a control device for the driving force distribution unit 26. The control torque characteristics may be set separately in consideration of individual differences between the electromagnetic couplings 40l and 40r.

  Regarding the driving force distribution of the front and rear wheels, for example, based on the accelerator operation amount θacc, each wheel rotation speed ωi, the steering angle Φ, the front and rear direction G, or a selected traveling mode such as a snowy road traveling mode, a predetermined sharing ratio The rear wheel side shared driving force is calculated from the above, and the transmission torque T of the pair of electromagnetic couplings 40 of the driving force distribution unit 26 so that the total driving force of the left and right rear wheels 32l and 32r becomes the rear wheel side shared driving force. To control. Regarding the driving force distribution of the left and right rear wheels 32l and 32r, for example, the driving force distribution to the left and right rear wheels 32l and 32r is equal to each other when traveling straight, on condition that the total driving force becomes the rear wheel side shared driving force. The transmission torque T of the pair of electromagnetic couplings 40 of the driving force distribution unit 26 is controlled to be equal to each other so that the distribution state is achieved. Specifically, the transmission torque T of the pair of electromagnetic couplings 40, that is, the equally distributed target torque Tc, is calculated so that an equally distributed driving force that is ½ of the rear wheel side shared driving force is obtained. The equally distributed excitation current Ic for obtaining the distributed target torque Tc is obtained based on the control torque characteristic shown by the solid line in FIG. 3, and the equally distributed excitation current Ic is output (applied) to each electromagnetic coupling 40. . This equally distributed excitation current Ic is an equally distributed signal value. FIG. 3 shows a case where the transmission torque T corresponding to the rear wheel side shared driving force is 100 Nm and the equally distributed target torque Tc = 50 Nm.

  On the other hand, at the time of turning, etc., on the condition that the total driving force becomes the rear wheel side shared driving force, the driving force distribution to the left and right rear wheels 32l and 32r is differently distributed. The transmission torque T of the pair of electromagnetic couplings 40 of the driving force distribution unit 26 is controlled to be different from each other. Specifically, the large side target torque Ta is calculated so that either one of the left and right rear wheels 32l and 32r has a large side driving force larger than the equally distributed driving force, and the large side target torque Ta is obtained. The large torque excitation current Ia is obtained based on the control torque characteristic indicated by the solid line in FIG. 3, and the large torque excitation current Ia is output to one of the pair of electromagnetic couplings 40. Also, a small target torque Tb is calculated, in which the other driving force of the left and right rear wheels 32l and 32r is a small driving force smaller than the equally distributed driving force, and the small torque exciting current Ib is obtained to obtain the small target torque Tb. Is obtained based on the control torque characteristic indicated by the solid line in FIG. 3, and the small torque excitation current Ib is output to the other of the pair of electromagnetic couplings 40. The large-side driving force and the small-side driving force are determined according to, for example, the distribution ratio with respect to the left and right rear wheels 32l and 32r. FIG. 3 shows the case where the distribution ratio is 1: 0 and the large-side target torque Ta = 100 Nm, small The side target torque Tb = 0 Nm. The distribution ratio may be a predetermined constant value, or may be variably set based on a traveling state such as the yaw angular velocity Y. The large torque excitation current Ia is a large torque signal value, and the small torque excitation current Ib is a small torque signal value.

  Here, when the driving force distribution for the left and right rear wheels 32l and 32r by the driving force distribution unit 26 shifts from the unequal distribution state to the equal distribution state, for example, when the vehicle travels from a turn to a straight travel, as shown in FIG. For the electromagnetic coupling 40 controlled to the large target torque Ta at the point A, the excitation current I is decreased from the large torque excitation current Ia to the equally distributed excitation current Ic in order to change the point C to the equally distributed target torque Tc. On the other hand, for the electromagnetic coupling 40 controlled to the small target torque Tb at the point B, the excitation current I is changed from the small torque excitation current Ib to the equally distributed excitation current in order to change to the point C of the equally distributed target torque Tc. It is necessary to increase to Ic. In this case, in this embodiment, since the increasing torque characteristic indicated by the solid line in FIG. 3 is used as the control torque characteristic, the electromagnetic coupling 40 for increasing the excitation current I from the point B to the point C, that is, the excitation current For the electromagnetic coupling 40 whose change in I is the same as the control torque characteristic, the transmission torque T becomes the equally distributed target torque Tc according to the control torque characteristic. However, for the electromagnetic coupling 40 that reduces the excitation current I from the point A to the point C, that is, the electromagnetic coupling 40 in which the change in the excitation current I is opposite to the control torque characteristic, the decreasing torque characteristic indicated by the broken line in FIG. Therefore, even if the control is performed with the equally distributed excitation current Ic, the C * point of the transmitted torque Tc * is larger than the equally distributed target torque Tc by the hysteresis. For this reason, the driving force distribution with respect to the left and right rear wheels 32l and 32r becomes unequal, which may impair the straight traveling performance of the vehicle.

  In the time chart of FIG. 5, the electromagnetic coupling 40r on the right rear wheel 32r side is the point A of the large target torque Ta, and the electromagnetic coupling 40l on the left rear wheel 32l side is the point B of the small target torque Tb. It is the figure which illustrated the change of the transmission torque T of each electromagnetic coupling 40r, 40l about the case (time t1-t3) when changing from the equally distributed state to the C point of both equally distributed states. With respect to the electromagnetic coupling 40l on the left rear wheel 32l side, the excitation current I is increased from the small torque excitation current Ib to the equally distributed excitation current Ic, so that from the small target torque Tb as shown by the solid line (thick line). It is changed to the equally distributed target torque Tc. On the other hand, for the electromagnetic coupling 40r on the right rear wheel 32r side, when the exciting current I is decreased and changed from the large torque exciting current Ia to the equally distributed exciting current Ic, as shown by the thin line, from the large target torque Ta. The transmission torque Tc * is larger than the equally distributed target torque Tc by the hysteresis.

  When the equal distribution shift control unit 54 shifts from the unequal distribution state to the equal distribution state, the driving force distribution to the left and right rear wheels 32l and 32r becomes unequal distribution due to the hysteresis of the electromagnetic coupling 40. In order to suppress this, equal distribution shift control is executed according to steps S1 to S5 (hereinafter simply referred to as S1 to S5) of the flowchart of FIG. In the description of the equal distribution transition control unit 54, in FIG. 3, the right electromagnetic coupling 40r is controlled at point A on the high torque side, and the left electromagnetic coupling 40l is controlled at point B on the low torque side. An example will be described in which the electromagnetic couplings 40l and 40r are shifted from the unequal distribution state to the equal distribution state in which both of the electromagnetic couplings 40l and 40r are at point C.

  The flowchart of FIG. 4 is a diagram illustrating signal processing for the electromagnetic couplings 40r and 40l on the right rear wheel 32r side and the left rear wheel 32l side, and the signal processing of S1 to S5 is performed separately. First, the control of the electromagnetic coupling 40r on the side of the right rear wheel 32r that reduces the excitation current I, which is opposite to the torque characteristic for control when the change in the excitation current I is shifted to the equally distributed state, is affected by the hysteresis. Will be described. In S1, whether or not the previous target torque (= Ta) of the electromagnetic coupling 40r on the right rear wheel 32r side (unequally distributed state) is larger than the target torque (= Tc) this time (equal distributed state). Judgment is made, and if Ta> Tc, S2 and subsequent steps are executed, but if NO (negative), that is, if Ta ≦ Tc, S5 is executed immediately. In this embodiment, since Ta> Tc, S2 and subsequent steps are executed. In S2, the previous target torque (= Ta) of the electromagnetic coupling 40r on the right rear wheel 32r side is larger than the previous target torque (= Tb) of the electromagnetic coupling 40l on the left rear wheel 32l side which is the opposite wheel. If Ta> Tb, S3 and subsequent steps are executed. If NO, that is, if Ta ≦ Tb, S5 is immediately executed. In this embodiment, since Ta> Tb, S3 and subsequent steps are executed.

  In S3, the current target torque (= Tc) of the electromagnetic coupling 40r on the right rear wheel 32r side is equal to the current target torque (= Tc) of the electromagnetic coupling 40l on the left rear wheel 32l side which is the opposite wheel. If NO, that is, if the current target torque is different between the left and right rear wheels 32r and 32l, S5 is immediately executed. In this embodiment, since all the target torques are equal to each other with the equally distributed target torque Tc, S4 is subsequently executed.

  In S4, as the current excitation current I of the electromagnetic coupling 40r on the right rear wheel 32r side, the via excitation current obtained by subtracting a predetermined correction value α from the equally distributed excitation current Ic corresponding to the equally distributed target torque Tc that is the target torque. Id (= Ic−α) is set. For example, the correction value α exceeds the equally distributed excitation current Ic, decreases to the via excitation current Id lower by the correction value α, and then returns to the equally distributed excitation current Ic, thereby reducing the hysteresis and the transmission torque T to the equal distribution target. For example, the large-side target torque Ta, which is the starting point torque, the equally-distributed target torque Tc, and the like are set in advance by experiments or the like so as to be near the torque Tc. The correction value α is determined so that the transmission torque Td * at that time is at least lower than the equally distributed target torque Tc regardless of hysteresis by being reduced to the via excitation current Id. Instead of the correction value α, the via excitation current Id itself can be set with the large target torque Ta and the equally distributed target torque Tc as parameters.

  In this way, when the exciting current I of the electromagnetic coupling 40r is reduced to the via excitation current Id, the electromagnetic coupling 40r is in a state near the D * point of the transmission torque Td * that is lower than the equally distributed target torque Tc. (See FIG. 3). The one-dot chain line in the time chart of FIG. 5 represents a change in the transmission torque T based on the control torque characteristic by the control of the excitation current I at this time, and the broken line represents a change in the actual transmission torque T including hysteresis. The time t2 in FIG. 5 is a time when the exciting current I of the electromagnetic coupling 40r is reduced to the passing exciting current Id and the actual transmission torque T becomes Td *. The via excitation current Id corresponds to the via signal value. The via torque Td is set by a data map or the like using the large target torque Ta and the equally distributed target torque Tc as the starting torque as parameters, and the via excitation current Id from which the via torque Td is obtained is represented by a control torque characteristic. You may make it ask | require based on.

  Returning to FIG. 4, in the next S5, as the current exciting current I of the electromagnetic coupling 40r on the right rear wheel 32r side, the equally distributed exciting current Ic corresponding to the equally distributed target torque Tc which is the target torque is set. That is, in S4, the current value is once decreased to the via excitation current Id lower than the equally distributed excitation current Ic by the correction value α, then increased by the correction value α and returned to the equally distributed excitation current Ic. Thereby, the transmission torque T of the electromagnetic coupling 40r is increased from the transmission torque Td *, and becomes a value in the vicinity of the equally distributed target torque Tc. By increasing the excitation current I and increasing the transmission torque T, the hysteresis generated when the excitation current I is reduced is reduced, and the transmission torque T is controlled with characteristics close to the control torque characteristics shown by the solid line in FIG. Become so. In FIG. 5, the transmission torque T of the electromagnetic coupling 40r is decreased to the transmission torque Td * at time t2, and then increased to the equally distributed target torque Tc at time t3. However, the transmission torque Td * is not necessarily obtained. There is no need to wait for the current to decrease, and the exciting current I may be changed separately from the actual change in the transmission torque T. That is, although there is a response delay in the change of the transmission torque T, the excitation current I may be continuously changed so that it can be increased to the equally distributed target torque Tc after at least lowering than the equally distributed target torque Tc. The change pattern of the excitation current I and the via excitation current Id are appropriately determined so that they finally become in the vicinity of the equally distributed target torque Tc and cause a sense of incongruity due to the torque change as much as possible.

  Next, control of the electromagnetic coupling 40l on the left rear wheel 32l side will be described. The parentheses in the flowchart of FIG. 4 relate to the signal processing of the electromagnetic coupling 40l on the left rear wheel 32l side, and are substantially the same as the control of the electromagnetic coupling 40r on the right rear wheel 32r side except for the left and right. It is. In this embodiment, the electromagnetic coupling 40l on the left rear wheel 32l side shifts from the unequal distribution state controlled to the low torque side point B to the C point equal distribution state. The previous target torque (unequally distributed state) of the coupling 40l is the small target torque Tb, which is smaller than the equally distributed target torque Tc, which is the current target torque (equal distributed state), and the determination of S1 is NO. S5 is immediately executed. In S5, as the current exciting current I of the electromagnetic coupling 40l on the left rear wheel 32l side, the equally distributed exciting current Ic corresponding to the equally distributed target torque Tc that is the target torque is set. In this case, the direction of change of the excitation current I is the same increasing direction as the control torque characteristic indicated by the solid line in FIG. 3, so that the transmission torque T of the electromagnetic coupling 40l reaches the equally distributed target torque Tc according to the control torque characteristic. Increased. A thick solid line in FIG. 5 shows a change in the transmission torque T of the electromagnetic coupling 40l, and is increased from the small target torque Tb to the equally distributed target torque Tc.

  As described above, in the driving force distribution unit 26 on the rear wheel side of the driving force transmission apparatus 10 of the present embodiment, the excitation currents of the pair of electromagnetic couplings 40r and 40l in order to shift from the unequal distribution state to the equal distribution state. When changing I to the equally distributed excitation current Ic, the control torque characteristic (solid line in FIG. 3) is opposite to the increase / decrease direction of the excitation current I, that is, for the electromagnetic coupling 40r on the side where the excitation current I is decreased. In order to reduce the excitation current I beyond the equally distributed excitation current Ic to the via excitation current Id determined on the decrease side and then return to the equally distributed excitation current Ic, the hysteresis of the electromagnetic coupling 40r is reduced and the transmission torque T Becomes a value near the equally distributed target torque Tc. On the other hand, for the electromagnetic coupling 40l on the side where the exciting current I increases or decreases in the same direction as the control torque characteristic, that is, on the side where the exciting current I is increased, the transmission torque T is controlled according to the control torque characteristic. The equally distributed target torque Tc is appropriately controlled by the equally distributed excitation current Ic determined according to the characteristic. As a result, the transmission torque T of the left and right electromagnetic couplings 40l and 40r is equal to or near the equally distributed target torque Tc regardless of hysteresis, and the driving force distribution to the left and right rear wheels 32l and 32r is substantially equal. Thus, the straightness of the vehicle after a turn or the like with different driving force distribution is improved.

  Further, since the transmission torque T of the pair of electromagnetic couplings 40l and 40r is controlled based on the control torque characteristic on either the increase side or decrease side of the excitation current I, the increase side and decrease side of the excitation current I are controlled. As compared with the case where the transmission torque T is controlled using both torque characteristics (that is, both torque characteristics shown by the solid line and the broken line in FIG. 3), the control becomes easier.

  Further, the excitation current I of one of the left and right electromagnetic couplings 40l and 40r, that is, the right electromagnetic coupling 40r is reduced from the large torque excitation current Ia to the equally distributed excitation current Ic, and the excitation current of the other electromagnetic coupling 40l. When increasing I from the small torque excitation current Ib to the equally distributed excitation current Ic, the control torque characteristic is opposite to the increase / decrease direction of the excitation current I, that is, the electromagnetic coupling 40r on the side where the excitation current I is decreased. Since the excitation current I is lowered to the via excitation current Id lower than the equally distributed excitation current Ic and then returned to the equally distributed excitation current Ic, the increasing and decreasing directions of the excitation currents I of the left and right electromagnetic couplings 40l and 40r are opposite. Nevertheless, the shift of the transmission torque T due to hysteresis is suppressed, and the driving force distribution to the left and right rear wheels 32l and 32r is substantially equal. Kuna' straight ahead of the vehicle is improved Te.

  Further, since the above-described via excitation current Id is an excitation current I that can reduce the transmission torque T of the electromagnetic coupling 40r beyond the equally distributed target torque Tc to the opposite side (decrease side) regardless of hysteresis. By returning to the equally distributed excitation current Ic, the change direction of the transmission torque T of the electromagnetic coupling 40 is reversed and increased, and changes in the same increase direction as the control torque characteristic to approach the equally distributed target torque Tc. Therefore, the hysteresis of the transmission torque T can be appropriately reduced.

  Next, another embodiment of the present invention will be described. In the following embodiments, parts that are substantially the same as those in the above embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 6 is a diagram for explaining another example of the equal distribution shift control executed by the equal distribution shift control unit 54, and is a flowchart corresponding to FIG. The electromagnetic couplings 40l and 40r have the same torque characteristics as in FIG. 3 as shown in FIG. 7, but in this embodiment, the decreasing torque characteristic shown by the solid line in FIG. 7 is used as the control torque characteristics. Is different. That is, on the basis of the decrease side torque characteristic used as the control torque characteristic, the opposite increase side torque characteristic becomes lower by the hysteresis. Further, from the unequal distribution state in which the right electromagnetic coupling 40r is controlled at the point A on the high torque side and the left electromagnetic coupling 40l is controlled at the point B on the low torque side, the electromagnetic couplings 40l, The point of shifting to an equally distributed state in which both 40r becomes point C is the same as in the previous embodiment.

  The flowchart of FIG. 6 is a diagram for explaining signal processing for the electromagnetic couplings 40r and 40l on the right rear wheel 32r side and the left rear wheel 32l side, and each of steps R1 to R5 (hereinafter simply referred to as R1 to R5). Signal processing is performed. First, the control of the electromagnetic coupling 40l on the side of the left rear wheel 32l that increases the excitation current I, which is opposite to the torque characteristic for control when the change in the excitation current I is shifted to the equidistributed state, is affected by the hysteresis. Will be described based on parentheses in the flowchart of FIG. In R1, it is determined whether or not the previous target torque (= Tb) of the electromagnetic coupling 40l on the left rear wheel 32l side is smaller than the target torque (= Tc) this time (equal distribution state). If Tb <Tc, R2 or less is executed, but if NO, that is, if Tb ≧ Tc, R5 is immediately executed. In this embodiment, since Tb <Tc, R2 and subsequent steps are executed. In R2, the previous target torque (= Tb) of the electromagnetic coupling 40l on the left rear wheel 32l side is smaller than the previous target torque (= Ta) of the electromagnetic coupling 40r on the right rear wheel 32r side which is the opposite wheel. If Tb <Ta, R3 or less is executed. If NO, that is, if Tb ≧ Ta, R5 is immediately executed. In this embodiment, since Tb <Ta, R <3 is executed.

  In R3, is the current target torque (= Tc) of the electromagnetic coupling 40l on the left rear wheel 32l side equal to the current target torque (= Tc) of the electromagnetic coupling 40r on the right rear wheel 32r side that is the opposite wheel? If it is determined that the target torque is different between the left and right rear wheels 32l and 32r, R5 is immediately executed. In this embodiment, since all the target torques are equal to each other with the equally distributed target torque Tc, R4 is subsequently executed.

  In R4, as the current excitation current I of the electromagnetic coupling 40l on the left rear wheel 32l side, the via excitation current obtained by adding a predetermined correction value β to the equally distributed excitation current Ic corresponding to the equally distributed target torque Tc that is the target torque. Ie (= Ic + β) is set. The correction value β exceeds, for example, the equally distributed excitation current Ic, increases to the via excitation current Ie that is higher by the correction value β, and then returns to the equally distributed excitation current Ic, whereby the hysteresis is reduced and the transmission torque T becomes the equal distribution target. For example, a small target torque Tb, which is a starting point torque, an equally distributed target torque Tc, and the like are set in advance through experiments or the like so as to be in the vicinity of the torque Tc. The correction value β is increased to the via excitation current Ie so that the transmission torque Te * increased according to the increase-side torque characteristic (broken line in FIG. 7) becomes at least higher than the equally distributed target torque Tc regardless of hysteresis. Determined. Instead of the correction value β, the via excitation current Ie itself can be set using the small target torque Tb and the equally distributed target torque Tc as parameters.

  In this way, when the exciting current I of the electromagnetic coupling 40l is increased to the via excitation current Ie, the electromagnetic coupling 40l is in a state near the E * point of the transmission torque Te * that is higher than the equally distributed target torque Tc. (See FIG. 7). A one-dot chain line in the time chart of FIG. 8 represents a change in the transmission torque T based on the control torque characteristic by the control of the excitation current I at this time, and a broken line represents a change in the actual transmission torque T including hysteresis. Time t2 in FIG. 8 is a time when the exciting current I of the electromagnetic coupling 40l is increased to the via exciting current Ie and the actual transmission torque T becomes Te *. The via excitation current Ie corresponds to the via signal value. The via torque Te is set by a data map or the like using the small target torque Tb and the equally distributed target torque Tc, which are starting torques, as parameters, and the via excitation current Ie from which the via torque Te is obtained is represented by a control torque characteristic. You may make it ask | require based on.

  Returning to FIG. 6, in the next R5, as the current exciting current I of the electromagnetic coupling 40l on the left rear wheel 32l side, the equally distributed exciting current Ic corresponding to the equally distributed target torque Tc which is the target torque is set. That is, in R4, the current is once increased to the via excitation current Ie that is higher than the equally distributed excitation current Ic by the correction value β, and then decreased by the correction value β and returned to the equally distributed excitation current Ic. As a result, the transmission torque T of the electromagnetic coupling 40l is decreased from the transmission torque Te * and becomes a value in the vicinity of the equally distributed target torque Tc. As the excitation current I decreases and the transmission torque T decreases, the hysteresis generated when the excitation current I increases is reduced, and the transmission torque T is controlled with characteristics close to the control torque characteristics shown by the solid line in FIG. Become so. In FIG. 8, the transmission torque T of the electromagnetic coupling 40l is increased to the transmission torque Te * at time t2, and then decreased to the equally distributed target torque Tc at time t3. However, the transmission torque Te * is not necessarily reduced. There is no need to wait until the current increases, and the exciting current I may be changed separately from the actual change in the transmission torque T. That is, although there is a response delay in the change of the transmission torque T, even if the excitation current I is continuously changed so that it can be lowered to the equally distributed target torque Tc after at least becoming higher than the equally distributed target torque Tc. The change pattern of the excitation current I and the via excitation current Ie are appropriately determined so that they finally become near the equally distributed target torque Tc and cause a sense of incongruity due to the torque change as much as possible. The thin line in FIG. 8 shows the case where the excitation current I of the electromagnetic coupling 40l is stopped at the equally distributed excitation current Ic without increasing it to the via excitation current Ie, and the transmission torque Tc * is smaller than the equally distributed target torque Tc by the hysteresis. Become.

  Next, control of the electromagnetic coupling 40r on the right rear wheel 32r side will be described. As for the control of the electromagnetic coupling 40r on the right rear wheel 32r side, substantially the same control as the electromagnetic coupling 40l on the left rear wheel 32l side is performed according to the flowchart of FIG. In this embodiment, since the electromagnetic coupling 40r on the right rear wheel 32r side is shifted from the unequal distribution state controlled to the point A on the high torque side to the C point equal distribution state, the electromagnetic on the right rear wheel 32r side is changed. The previous target torque (unequally distributed state) of the coupling 40r is the large target torque Ta, which is larger than the equally distributed target torque Tc that is the current target torque (equal distributed state), and the determination of R1 is NO. Immediately R5 is executed. In R5, the equally distributed exciting current Ic corresponding to the equally distributed target torque Tc that is the target torque is set as the exciting current I of the electromagnetic coupling 40r on the right rear wheel 32r side this time. In this case, the direction of change of the excitation current I is the same decreasing direction as the control torque characteristic indicated by the solid line in FIG. 7, so that the transmission torque T of the electromagnetic coupling 40r reaches the equally distributed target torque Tc according to the control torque characteristic. Reduced. A solid line (thick line) in FIG. 8 is a diagram showing a change in the transmission torque T of the electromagnetic coupling 40r, and is decreased from the large target torque Ta to the equally distributed target torque Tc.

  Also in this embodiment, when the excitation current I of the pair of electromagnetic couplings 40r and 40l is changed to the equally distributed excitation current Ic in order to shift from the unequal distribution state to the equal distribution state, the torque characteristic for control (FIG. 7). The direction of increase / decrease of the excitation current I is opposite to that of the solid line), that is, for the electromagnetic coupling 40l on the side where the excitation current I is increased, the excitation current I exceeds the equally distributed excitation current Ic and is set on the increase side. Since the excitation current Ie is changed to the equal distribution excitation current Ic after being changed, the hysteresis of the electromagnetic coupling 40l is reduced and the transmission torque T becomes a value near the equal distribution target torque Tc. Thereby, substantially the same effect as the above-described embodiment can be obtained.

  As mentioned above, although the Example of this invention was described in detail based on drawing, these are one Embodiment to the last, This invention is implemented in the aspect which added the various change and improvement based on the knowledge of those skilled in the art. be able to.

  26: driving force distribution unit 32l, 32r: rear wheel (wheel) 38: rear wheel side input shaft (driving force input unit) 40l, 40r: electromagnetic coupling (friction clutch) 50: electronic control device (control device) 54: Equal distribution transition control section I: Excitation current (control signal) Ia: Large torque excitation current (large torque signal value) Ib: Small torque excitation current (small torque signal value) Ic: Equal distribution excitation current (equal distribution signal value) Id , Ie: Via excitation current (via signal value) T: Transfer torque Ta: Large target torque Tb: Small target torque Tc: Equal distribution target torque

Claims (3)

The driving force distribution unit is provided with a friction clutch provided between the driving force input unit and the left and right wheels, respectively, and controls the control signals for controlling the transmission torque of the pair of friction clutches, thereby controlling the left and right In the control device of the driving force distribution unit for adjusting the driving force distribution to each wheel of
The pair of friction clutches have hysteresis between the torque characteristic on the increase side of the control signal and the torque characteristic on the decrease side of the control signal,
The control signals for the pair of friction clutches are signals for obtaining a predetermined target torque based on a predetermined control torque characteristic composed of any one of the increase side torque characteristic and the decrease side torque characteristic. Controlled by the value,
In order to shift from the unequal distribution state in which the driving force distribution to the left and right wheels is different to the equal distribution state in which the driving force distribution to the left and right wheels is equal to each other, the control signals of the pair of friction clutches are When changing to the equally distributed signal value determined based on the control torque characteristic so that the equally distributed target torque can be obtained as the target torque, the increasing / decreasing direction of the control signal is opposite to the control torque characteristic. The friction clutch includes an equal distribution transition control unit that changes the control signal beyond the equal distribution signal value to a via signal value determined on the opposite side and then returns to the equal distribution signal value. Control device for driving force distribution unit. The unequal distribution state is determined based on the control torque characteristics so that a control signal of the friction clutch on either the left or right wheel side can obtain a larger target torque larger than the equal distribution target torque. Based on the control torque characteristic so that a small target torque smaller than the equally distributed target torque can be obtained by the control signal of the friction clutch on the other wheel side. In a state controlled to a defined small torque signal value,
The equal distribution transition control unit changes the control signal of the friction clutch on the one wheel side from the large torque signal value to the equal distribution signal value, and the control signal of the friction clutch on the other wheel side is changed to the control signal. When changing from a small torque signal value to the equally distributed signal value, the control signal is changed to the via signal value for a friction clutch whose control signal is in the opposite direction of increase / decrease from the control torque characteristic. The control device for a driving force distribution unit according to claim 1, wherein the control unit returns to the equal distribution signal value later. The said route signal value is a signal value which can change the transmission torque of the said friction clutch to the opposite side exceeding the said equal distribution target torque irrespective of the said hysteresis. Control device for driving force distribution unit.

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