JP3753144B2 - Control device for vehicle torque distribution clutch - Google Patents

Description

  The present invention relates to an apparatus for controlling transmission torque of a torque distribution clutch in a vehicle including a torque distribution clutch provided in a power transmission path of the vehicle in order to adjust a ratio of torque transmitted from a prime mover to each of a plurality of wheels. It is about.

  Torque that is provided in series on a power transmission path from a prime mover to a plurality of wheels or that is provided in parallel with a differential gear device on the power transmission path and that is transmitted to each wheel Vehicles of the type in which the percentage of the vehicle is adjusted are known. For example, a four-wheel drive vehicle having a torque distribution clutch provided in series between an engine and a front wheel differential gear device or a rear wheel differential gear device, provided in parallel to the differential gear device for differential limitation. For example, a four-wheel drive vehicle having a differential limiting clutch. The purpose of the torque distribution clutch is to obtain traction according to the vehicle state during normal travel, start-up travel, etc., or to obtain wheel driving force according to the weight distribution of the vehicle that changes due to load movement. Used for torque distribution control.

  In such a vehicle, the front and rear wheel driving force distribution is based on the throttle opening and the front and rear wheel rotational speed differences so as to obtain the torque distribution clutch transmission torque corresponding to the engine output and the front and rear wheel rotational speed differences. Is controlled. For example, this is the driving force distribution control device described in Patent Document 1.

JP-A-3-37424

  However, according to the above conventional driving force distribution control device, torque is always transmitted via the torque distribution clutch in order to obtain the wheel driving force according to the weight distribution of the vehicle. Even in this state, driving torque is required due to running resistance (rolling resistance, air resistance, etc.) that increases according to the vehicle speed, and a certain amount of transmission torque is output to the torque distribution clutch. There was a disadvantage that the durability of the torque distribution clutch was lowered.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a control device for a vehicle torque distribution clutch that can improve the fuel consumption of the vehicle and the durability of the torque distribution clutch. .

  The present inventors have made various studies on the background of the above circumstances, that is, in the case of four-wheel drive vehicle traveling substantially straight and at constant speed, the driving is smaller than the size corresponding to the running resistance of the vehicle. When running with torque, there is no need to distribute the driving torque equivalent to weight distribution to improve the acceleration performance of the vehicle to the front and rear wheels, so torque distribution rather than to increase fuel efficiency and durability Found the fact that the clutch should be released. The present invention has been made based on such findings.

That is, the gist of the invention according to claim 1 for achieving the above object is to provide a predetermined torque distribution in a vehicle including a torque distribution clutch that adjusts a ratio of torque transmitted from a prime mover to each of a plurality of wheels. Is a control device for a vehicle torque distribution clutch that controls the transmission torque of the torque distribution clutch so as to obtain (a) a travel resistance related amount calculation that calculates a travel resistance related amount related to the travel resistance of the vehicle And (b) controlling the transmission torque of the torque distribution clutch so that the torque distribution basically corresponds to the weight distribution of the vehicle based on the driving resistance related quantity calculated by the driving resistance related quantity calculating means. Suruga, actual input torque to said torque distribution clutch is smaller than the value a is running straight and constant-speed running of the vehicle corresponding to the vehicle running resistance spot In that the torque distribution clutch control means for releasing the torque distribution clutch, including the.

  According to a second aspect of the present invention, the torque distribution clutch control means decreases the transmission torque of the torque distribution clutch toward zero as the input torque of the torque distribution clutch decreases. It is characterized by being.

According to the first aspect of the present invention, since the torque distribution clutch control means controls the transmission torque of the torque distribution clutch based on the travel resistance related quantity calculated by the travel resistance related quantity calculation means, The durability of the torque distribution clutch is increased. Further, when the vehicle is running straight and at a constant speed and the actual input torque to the torque distribution clutch is smaller than the value corresponding to the vehicle running resistance, the torque distribution clutch is released. The fuel consumption and the durability of the torque distribution clutch are preferably improved.

  According to the second aspect of the invention, the torque distribution clutch control means decreases the transmission torque of the torque distribution clutch toward zero as the input torque of the torque distribution clutch decreases, so the input torque is large. In some cases, a large torque is distributed through the torque distribution clutch to improve acceleration performance. On the other hand, when the input torque is small, the load on the torque distribution clutch is suppressed and the fuel consumption of the vehicle and the durability of the torque distribution clutch are reduced. Increased further.

  Here, it is preferable that the travel resistance-related amount calculating means of the first aspect of the present invention calculates a flat land constant speed travel driving torque necessary for traveling straight on a flat ground at a constant speed from an actual vehicle speed based on a previously stored relationship. The torque distribution clutch control means calculates torque distribution that is changed in relation to the motor output torque in torque distribution control during normal traveling selected during straight traveling when the rudder angle is a predetermined value or less. The transmission torque of the clutch is made so small that the actual output torque of the prime mover approaches the flat ground speed traveling drive torque, and zero when the torque is below the flat ground speed traveling drive torque. In this way, as the output torque of the prime mover becomes larger than the above-mentioned flat land constant speed traveling drive torque, that is, the greater the intention of acceleration, the transmission torque of the torque distribution clutch is increased and the acceleration performance is enhanced, while the output torque of the prime mover is increased. When the driving torque is lower than the above flat land constant speed traveling driving torque, the vehicle is decelerating or coasting without intention to accelerate, so that the torque distribution clutch is released, and the fuel efficiency of the vehicle and the durability of the torque distribution clutch are enhanced.

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

  FIG. 1 shows a power transmission device for a vehicle provided with a torque distribution clutch control device according to an embodiment of the present invention. In the figure, an engine 10 functioning as a prime mover is fastened with an automatic transmission 12 with a torque converter, a front differential gear unit 14, and a transaxle housing 18 that houses a transfer 16. Thereby, the output torque of the engine 10 is transmitted to the pair of left and right front wheels 24 and 26 via the automatic transmission 12 with torque converter, the front differential gear unit 14, and the pair of left and right axles 20 and 22. , The above-described automatic transmission 12 with torque converter, transfer 16, propeller shaft 28, electromagnetic clutch 30 functioning as a torque distribution clutch, rear differential gear device 32, and a pair of left and right axles 34, 36, and a pair of left and right rears. It is transmitted to the wheels 38 and 40.

The electromagnetic clutch 30 functions as a torque distribution clutch for adjusting the ratio of torque transmitted from the engine 10 to the front wheels 24, 26 and the rear wheels 38, 40, and is connected to the propeller shaft 28. An input side friction plate 42 that rotates with the input side friction plate 42, an output side friction plate 46 that is connected to the drive pinion 44 of the rear differential gear device 32 and rotates therewith, and the input side friction plate 42 and the output side friction plate 46. And electromagnetic solenoids 48 that are frictionally engaged with each other by being pressed according to electromagnetic force, and configured to generate a transmission torque having a magnitude corresponding to a command value t _ref from an electronic control device 110 described later. Has been. When the electromagnetic clutch 30 is released, 100% of the torque output from the engine 10 is transmitted to the front wheels 24 and 26. However, when the electromagnetic clutch 30 is fully engaged, the output from the engine 10 is transmitted. Since 50% of the torque to be transmitted is transmitted to the front wheels 24 and 26 and the remaining 50% is transmitted to the rear wheels 38 and 40, in this embodiment, the torque distribution adjustment range by the electromagnetic clutch 30 is the front and rear wheels. When the weight distribution ratio with the wheel is 0.5: 0.5, the torque distribution ratio range is between 1: 0 and 0.5: 0.5. Generally, when the electromagnetic clutch 30 is completely engaged, the torque of the front and rear wheels is distributed corresponding to the weight distribution of the front and rear wheels. In this embodiment, the torque of the front and rear wheels can be adjusted by the electromagnetic clutch 30 from the front wheel drive state to the direct connection 4WD.

  As shown in detail in FIG. 2, the electromagnetic clutch 30 has a universal joint 50 and a clutch drum 52 coupled to the propeller shaft 28 at both shaft ends, and is rotatably supported by a clutch housing 54 via a bearing 56. An input shaft 58 and an output shaft 62 rotatably supported by a clutch housing 54 via a bearing 60 in a state of being concentric with the input shaft 58 and a shaft end face of the input shaft 58 are fitted so as to be relatively rotatable. In this state, the clutch rotor 64 connected to the input shaft 58 is engaged with the projection 65 of the clutch housing 54 that is a non-rotating member so as not to rotate. And an annular magnetic member 68 that is attracted by the magnetic force of the electromagnetic solenoid 48. A control clutch (pilot clutch) 70 provided between the inner peripheral surface of the latch drum 52 and the outer peripheral surface of the clutch rotor 64 and generating a relatively small friction torque by the magnetic force of the electromagnetic solenoid 48, and the control clutch 70 A cam ring 72 to which friction torque from the cam ring 72 is transmitted and a ball cam 74 in contact with the cam ring 72, and a relatively small rotational force transmitted through the control clutch 70 is used as a force in the thrust direction (axial direction). A pressing device 78 that converts and boosts and transmits the pressure to the annular pressing member 76 and is movable in the axial direction with respect to the inner peripheral surface of the clutch drum 52 and the outer peripheral surface of the clutch rotor 64 in a state of being overlapped with each other in the axial direction. Further, the thrust from the annular pressing member 76 is provided so as not to rotate relative to the axis. The input side friction plate 42 and the output side friction plate 46 pressed by a direction force are provided, and a transmission torque having a magnitude corresponding to the drive current supplied to the electromagnetic solenoid 48 is generated in accordance with, for example, the characteristics shown in FIG. Let

Returning to FIG. 1, the vehicle has a four-wheel drive selection switch 80 that is operated when the four-wheel drive mode is selected, a wheel speed sensor 82 that detects the rotation speed of the left front wheel 24, and the rotation speed of the right front wheel 26. a wheel speed sensor 84 for detecting the wheel speed sensor 86 for detecting the rotational speed of the left rear wheel 38, wheel speed sensor 88 detects the rotational speed of the right rear wheel 40, the acceleration G _X of the longitudinal acceleration G ie the running direction of the vehicle A longitudinal G sensor 90 for detecting, a lateral G sensor 92 for detecting lateral acceleration G of the vehicle, that is, lateral acceleration G _Y , a steering angle sensor 94 for detecting the steering angle of the vehicle operated by the steering wheel 93, and an operation by an accelerator pedal The throttle sensor 96 for detecting the throttle opening, the engine speed sensor 98 for detecting the rotational speed of the engine 10, and the actual state of the automatic transmission 12 The shift position sensor 100 for detecting the gear position, that is, the shift position, the brake sensor 104 for detecting that the brake pedal 102 is operated, the PB brake sensor 108 for detecting that the parking brake lever 106 is operated, and the center of gravity of the vehicle body A yaw rate sensor 116 for detecting a yaw rate r that is a rotational angular velocity (yaw angular velocity) around a vertical line passing therethrough is provided, and a signal S4WD indicating that the four-wheel drive mode has been selected from those switches or sensors, respectively. A signal SN _FL indicating the rotational speed N _FL of the left front wheel 24, a signal SN _FR indicating the rotational speed N _FR of the right front wheel 26, a signal SN _RL indicating the rotational speed N _RL of the left rear wheel 38, and the rotational speed of the right rear wheel 40 signal SN _RR indicating the N _RR, the signal SG _X indicating the longitudinal acceleration G _X, signal SG _Y indicating the lateral acceleration G _Y, the vehicle Signal indicating the angular [delta] Esuderuta, signals indicating a throttle opening theta _th S.theta, signal SN _E indicating the rotational speed N _E of the engine 10, a signal SSP indicating the shift position SP, signal SBK indicating the operation of the brake pedal 102, the parking brake A signal SPB indicating the operation of the lever 106 and a signal Sr indicating the yaw rate r are supplied to the electronic controller 110 for torque distribution control.

  The front / rear G sensor 90 and the left / right G sensor 92 are each a piezoelectric type including a member having a relatively large mass and a piezoelectric element that detects a force acting on the member, that is, an acceleration, or a member having a relatively large mass. And a servo type that detects the acceleration based on the drive current of the electromagnetic coil, and an electromagnetic coil that generates an equilibrium force by electromagnetic force so as to keep the displacement due to the acceleration applied to the member at the original position. ing. The yaw rate sensor 116 is well known as a rate gyro, and is constituted by a gas type, a vibration type, a laser type, or the like.

The electronic control device 110 is a so-called microcomputer including a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU executes the program stored in the ROM in advance while using the storage function of the RAM. The input signal is processed, a control signal is output to the electromagnetic clutch 30, and an operation indicator lamp 112 indicating that the electromagnetic clutch 30 is in operation and an abnormality indicator lamp 114 indicating an abnormality of the electromagnetic clutch 30 are displayed. FIG. 4 shows an example of the configuration of the electronic control unit 110 in detail. From the electronic controller 115 for engine control and shift control, a throttle opening θ _th , a gear indicating the automatic transmission 12, a signal indicating a failure of the engine system, and an engine pulse signal having a frequency corresponding to the rotational speed of the engine 10 are electronically transmitted. It is supplied to the control device 110. The electronic control device 110 includes an ABS control device 116 and a 4WD control device 117, and a drive circuit 118 that outputs a control current to the electromagnetic clutch 30 in response to a command signal representing the command value _tref .

5 and 6 are functional block diagrams illustrating the main part of the control function of the electronic control device 110. FIG. First, in FIG. 5, the torque distribution clutch control means 120 is a plurality of types of controls that control the torque distribution of the front and rear wheels of the vehicle, such as start control, turning control, normal travel control, and braking control. Any one of the modes should be selected alternatively based on the vehicle state, and the transmission torque of the electromagnetic clutch 30 or the electromagnetic clutch 30 should be supplied in accordance with a control formula preset in the selected control mode. A control signal SC representing a command value t _ref having a magnitude corresponding to the drive current is output and the operation indicator lamp 112 is turned on. In other words, when the four-wheel drive mode is selected by the four-wheel drive selection switch 80, the torque distribution clutch control means 120 selects the brake control when the brake sensor 104 detects the operation of the main brake. Further, for example, starting control (1) in FIG. 7) and turning control (2) in FIG. 7 based on the running state indicated by the vehicle speed V and the vehicle steering angle δ from the region shown in the relationship of FIG. , Torque distribution control selection means 252 for selecting one of normal running time control (3 in FIG. 7), and braking time control that is selected by this torque distribution control selection means 252 and performs torque distribution control operation Means 254, start time control means 256, turning travel time control means 258, and normal travel time control means 260 are included.

The vehicle speed calculation means 178 is based on the rotation speed of the output shaft of the automatic transmission 12 from any one of the front wheel rotation speeds N _FL and N _FR , the rear wheel rotation speeds N _RL and N _RR , or by a vehicle speed sensor (not shown). A vehicle speed, that is, a vehicle body speed V is calculated from the detected vehicle speed signal.

In the area storage means 262, as shown in FIG. 7, a determination criterion for performing area determination in two-dimensional coordinates of a vehicle speed axis (horizontal axis) indicating the vehicle speed V and a steering angle axis (vertical axis) indicating the steering angle. The vehicle speed V _s and the judgment reference angle M _delta (V) are stored. The determination reference vehicle speed V _s is set, for example, within a range of 20 to 30 km / h, preferably about 25 km / h. The determination reference angle M _delta (V) is a function of the vehicle speed V. As the vehicle speed V increases, the determination reference angle M _delta (V) is a first value corresponding to the determination reference vehicle speed V _s , for example, about 45 ° to 60 Km / h. It is set so as to change toward a second value corresponding to the vehicle speed, for example, 25 °, and to be constant thereafter. When the braking operation is detected by the brake sensor 104, the torque distribution control selection unit 252 determines the braking control, but it is substantially that the torque distribution control selection unit 252 has entered one of the regions in FIG. 7 stored in the region storage unit 262. Is determined based on the vehicle speed V and the steering angle δ which is the turning operation amount of the vehicle, and a plurality of types such as start control, turning control, and normal control 3 are determined. Regarding torque distribution control determining means 264 that determines (selects) the control satisfying the selection condition from the types of torque distribution control, and switching from turning control to other control such as starting control or normal driving control, When the other control different from the turning control by the torque distribution control determining means 264 is determined, for example, 0.5 to several seconds from the determination. It includes a torque distribution control selection delay means 266 for selecting formally other control based on the predetermined delay time of the time has elapsed.

Further, the torque distribution clutch control means 120 has a yaw rate deviation e [= (r ° −r) sign (r) between the target yaw rate r ° based on the steering angle δ that is the turning operation amount and the actual yaw rate r. ], A turning state detecting means 270 for detecting parameters indicating the actual turning state of the vehicle, such as the rate of change de / dt of the yaw rate deviation e, and the actual turning state of the vehicle detected by the turning state detecting means 270 For example, when the yaw rate deviation e and its rate of change de / dt are _{equal to} or greater than _preset judgment reference values K _MAPE and K _MAPB , the torque distribution control determining means 264 performs control during turning based on the turning operation amount. And a turning time control command means 272 for giving a command for starting the turning time control even when the torque distribution control is not determined. 264, that when receiving the command by the turning time control command means 272, a time control turning determined preferentially initiate it. The determination reference values K _MAPE and K _MAPB are set in advance to determine a relatively large and rapidly increasing understeer.

  In the start time control by the start time control means 256, in order to obtain the maximum traction according to the vehicle state, the torque distribution according to the weight distribution between the front wheels 24, 26 and the rear wheels 38, 40, which changes due to the load movement, The electromagnetic clutch 30 is controlled so as to be, or the electromagnetic clutch 30 is controlled so as to limit the transmission torque to the rear wheels 38 and 40 according to the steering angle δ. Further, in the turning time control by the turning time control means 258, in order to improve the handling stability during turning on a snowy road or a frozen road having a particularly small road surface friction coefficient, for example, an intermediate neutral between understeer and oversteer The electromagnetic clutch 30 is controlled so that the actual yaw rate r follows the target yaw rate r ° (turning angular velocity around the vertical line passing through the center of gravity) determined to be steered. The normal travel time control by the normal travel time control means 260 is performed during the straight travel when the rudder angle δ is within a predetermined range. In this case, basically, torque distribution corresponding to weight distribution and Thus, when the rotational speed difference between the input side and the output side of the electromagnetic clutch 30 is generated, the transmission torque is increased. However, it is possible to increase the fuel consumption when the four-wheel drive such as the straight traveling is unnecessary. Thus, the electromagnetic clutch 30 is controlled so as to reduce the fastening force. In the braking control by the braking control means 254, the electromagnetic clutch 30 is directly released when the brake pedal 102 is operated in order to avoid control interference with the ABS control or the VSC control. Or, until the ABS control is started, the electromagnetic clutch 30 is engaged and the engine braking force is distributed to the four wheels. When the ABS control is started, the engagement force is reduced, and when the VSC control is started, the release is released. Thus, the electromagnetic clutch 30 is controlled.

FIG. 6 is a diagram for explaining the function of the normal running control means 260 in more detail. The input torque calculation means 122 calculates the output torque around the propeller shaft 28 of the engine 10 (vehicle drive torque), that is, the input torque t _in (N · m) of the electromagnetic clutch 30 from, for example, the previously stored relationship shown in FIG. It is sequentially calculated based on the actual engine speed N _E (rpm) and the throttle opening θ _th (%) or the intake air amount Q. This input torque calculating means 122 is preferably obtained in a moving section that has a preset time width and is moved with the passage of time when it is determined that the vehicle is traveling straight, at a constant speed, or on flat ground. and calculates an average value or moving average value t _iNAV of a plurality of input torque t _in the input torque t _in. Here, the input torque t _in the the wheel driving torque i.e. transmission torque t _r after being distributed to the rear wheels 38 and 40 side from the front wheel drive torque t _f and the electromagnetic clutch 30 to be distributed to the front wheels 24 and 26 side It is defined as the sum (t _in = t _f + t _r ). Torque t _r which is distributed to the rear wheel 38 and 40 side is the transmission torque of the electromagnetic clutch 30, in the steady state corresponds to the command value t _ref to the electromagnetic clutch 30.

The rotational speed difference calculating means 124 calculates the rotational speed N _f of the input shaft 58 of the electromagnetic clutch 30 based on the average value of the front wheel rotational speeds N _FL and N _FR and the gear ratio of the front differential gear unit 14. , calculated on the basis of the average value and the gear ratio of the rear differential gear device 32 of the rotational speed N _r of the rear wheels rotating a few degrees N _RL and N _RR of the output shaft 62 of the electromagnetic clutch 30, the rotational speed of the input shaft 58 by the N _f subtracting the rotational speed N _r of the output shaft 62, the input shaft 58 and the rotational speed difference .DELTA.N (rpm) i.e. of the electromagnetic clutch 30 differential (slip) between the output shaft 62 rotational speed .DELTA.N (= N _f - _Nr ) is calculated. This rotational speed difference calculating means 124 is also preferably obtained within a moving section that has a preset time width and is moved with the passage of time in a state in which straight traveling, constant speed, and flat road traveling are determined. The differential rotational speed ΔN _av is calculated as an average value of the plurality of differential rotational speeds ΔN, that is, a moving average value.

For example, the diameter difference determining means 242 determines whether the vehicle travels linearly when the steering angle δ or the rotational speed difference between the left and right wheels [(N _FL + N _RL ) / 2] − [(N _FR + N _RR ) / 2] is a predetermined criterion. Is determined based on whether the vehicle is traveling at a constant speed, for example, the vehicle speed change rate ΔV is less than or equal to a predetermined criterion value, and the vehicle is traveling at a low slip rate, for example, an electromagnetic clutch. when the input torque t _in the 30 transmission torque t _r that command torque t _ref of it and the electromagnetic clutch 30 is less than a predetermined value is determined on the basis of not more than the predetermined value, for example, pre-stored as shown in equation 1 From the calculated formula, the rotational speed N _f of the input shaft 58 of the electromagnetic clutch 30, the rotational speed N _r of the output shaft 62 during such straight traveling, constant speed traveling, and low slip ratio traveling, the actual speed of the electromagnetic clutch 30. Input torque t _{i n} and transmission (output) based on the torque t _r, the diameter difference parameters related to the diameter difference between the front and rear wheels, for example, the rotational speed ratio or diameter difference correction coefficient kik, calculated. The above predetermined value is, for example, between the slip ratio [(vehicle speed−wheel speed) / vehicle speed] shown in FIG. 9 and the longitudinal force coefficient (value corresponding to the driving force of the wheel, which is a function of the road surface friction coefficient μ). In order to determine that the region A is in the substantially linear region A, it is obtained experimentally in advance. This formula 1 is the addition of the second term on the right side in consideration of the effect of wheel slip in order to accurately determine the diameter difference regardless of the road surface condition. From the rotational motion equation in the dynamic model of the front and rear wheels, It is theoretically derived. If slip does not matter so much, the diameter difference determining means 242 uses the input / output rotational speed ratio (= N _r / N _f ) of the electromagnetic clutch 30 during straight running as the diameter difference correction coefficient kik. Also good.

_{kik = (N r / N f} ) + K kik · (t in -2t r) ··· (1)

  The rotational speed difference correcting unit 132 removes an error caused by the diameter difference between the front wheels and the rear wheels from the rotational speed difference ΔN calculated by the rotational speed difference calculating unit 124, for example, from the correction formula shown in Formula 2 above. The rotational speed difference ΔN is corrected based on the diameter difference correction coefficient kik obtained by the diameter difference determining means 242, and the corrected rotational speed difference ΔN ′ is transferred to the normal travel time control means 260 in the torque distribution clutch control means 120. Supply.

ΔN ′ = ΔN− (1-kik) N _f (2)

The travel resistance related amount calculation means 276 stores in advance a travel resistance related amount related to the travel resistance of the vehicle, for example, a drive torque necessary for straight traveling at a constant flat speed, that is, a map value M _tindf (V), for example as shown in FIG. Based on the relationship thus calculated, the vehicle speed V is calculated and supplied to the normal travel time control means 260 in the torque distribution clutch control means 120.

The normal travel time control means 260 calculates the driving torque calculated by the travel resistance related amount calculation means 276, that is, the map value M _tindf (V) and the input torque t calculated by the input torque calculation means 122, from Equation 3 to be described later. Based on _in , the transmission torque of the electromagnetic clutch 30, that is, the torque command value t _ref is calculated and output. As shown in Equation 3, the torque command value t _ref for instructing the differential limiting torque (transmission torque) for the electromagnetic clutch 30 is a reference calculated from Equation 4, for example, so as to have a magnitude corresponding to the weight distribution. It is an addition value of the torque command value t _df and the torque command value t _dn calculated from, for example, Equation 5 so as to have a magnitude corresponding to the differential rotation speed. The reference torque command value t _df is a value for obtaining torque distribution of the front and rear wheels corresponding to the weight distribution of the front and rear wheels, and the torque command value t _dn improves acceleration response in consideration of correction of the diameter difference between the front and rear wheels. It is a value to do.

In Equation 4 to determine the reference torque command value _{t df,} M tindf (V) is a map value determined based on the vehicle speed V from a pre-stored relationship shown in FIG. 10 for example, L _F is a vehicle body The distance from the center of gravity to the front wheel axis, L is the wheelbase, H _CG is the height of the center of gravity of the vehicle body, and G _X is the acceleration in the longitudinal direction of the vehicle. It is better to actively limit the differential with the electromagnetic clutch 30 in a state where there is an intention to accelerate. However, there is no benefit of the differential limitation in a steady traveling state such as a straight traveling at a constant speed. 10 causes a disadvantage that the durability of the vehicle 30 is lowered. Therefore, the relationship shown in FIG. 10 indicates that the driving torque (the output torque of the engine 10) for steady running determined by the air resistance and rolling resistance of the vehicle is equal to the vehicle speed V. is indicated by a solid line as a function, when the input torque t _in the output torque i.e. the electromagnetic clutch 30 of the actual engine 10 is below the drive torque for the steady-state running, and negative reference torque command value t _df from equation 4 However, from the condition that the reference torque command value t _df takes a positive value of 0 or more (t _df ≧ 0), in such a case, the reference torque command value t _df is set to zero and The magnetic clutch 30 is released. Thus, the normal running time control unit 260 controls so that the input torque t _in the electromagnetic clutch 30 is reduced toward zero transmission torque of the electromagnetic clutch 30 as decreases.

Further, in Formula 5 for _obtaining the torque command value t _dn that causes the transmission torque, that is, the torque command value t _ref to have a magnitude corresponding to the differential rotational speed ΔN of the electromagnetic clutch 30, the map value M _thnA (ΔN ′ ) Or M _thnA (ΔN) is a map value determined based on, for example, the rotational speed difference ΔN ′ after correction by the radial difference correction coefficient kik or the rotational speed difference ΔN before correction from the relationship stored in advance shown in FIG. _Yes , M _thnB (ΔN) or M _thnB (ΔN ′) is a map value determined based on, for example, the rotational speed difference ΔN before correction or the rotational speed difference ΔN ′ after correction based on a previously stored relationship shown in FIG. It is. In the vehicle, as shown in FIG. 13, the lateral force of the wheels (tires) has a property of decreasing with an increase in the absolute value of the slip ratio, so that the rear wheels 38 and 40 are increased with an increase in the transmission torque of the electromagnetic clutch 30. There is a tendency that the slip ratio increases and the lateral force decreases, and the straight running stability is impaired. Therefore, the rotational speed N _r is high i.e. the rotational speed difference ΔN is negative state of the rear wheels 38 and 40 as compared to the front wheels 24, 26 when the vehicle driving, the differential limiting torque of the electromagnetic clutch 30 as a zero It would be desirable to release it and prevent a reduction in lateral force due to diameter differences. Further, even at a rotational speed N _r is low i.e. the rotational speed difference ΔN is positive state of the rear wheels 38 and 40 as compared to the front wheels 24, 26 during vehicle braking, it differential limiting torque of the electromagnetic clutch 30 as a zero It is desirable to prevent the decrease in lateral force due to the difference in diameter. Therefore, when the rotational speed N _r of the rear wheels 38 and 40 is higher than that of the front wheels 24 and 26 due to the diameter difference (kik> 1), the equation (5-2) is used. When the rotational speed N _r of the rear wheels 38 and 40 is lower than that of the front wheels 24 and 26 due to the diameter difference (kik ≦ 1), the expression (5-1) is used, In order to improve the straight running stability, the two types of rotational speed differences ΔN and ΔN ′ and the map values M _thnA and M _thnB are selectively used, and the section between the point where ΔN becomes zero and the point where ΔN ′ becomes zero That is, the torque value t _dn is set to zero in the section that is turned from the road surface due to the diameter difference. Therefore, the normal travel time control means 260 increases from the point where the rotational speed difference ΔN becomes zero with an increase in the rotational speed difference ΔN, and from the point where the corrected ΔN ′ becomes zero, the corrected ΔN ′. Thus, the torque value t _dn is determined so as to increase with the decrease.

  That is, for example, when the average diameter of the front wheels 24 and 26 is larger than the average diameter of the rear wheels 38 and 40, the electromagnetic clutch 30 is increased so as to increase with an increase in the rotational speed difference ΔN before correction during acceleration traveling. The differential limiting torque is determined, and the differential limiting torque of the electromagnetic clutch 30 is determined so as to increase with an increase in the corrected rotational speed difference ΔN ′ in the deceleration traveling, and the average diameter of the front wheels 24 and 26 is determined by the rear wheels. When the average diameter is smaller than 38 and 40, the differential limiting torque of the electromagnetic clutch 30 is determined so as to increase in accordance with the increase in the corrected rotational speed difference ΔN ′ during acceleration traveling and is corrected during deceleration traveling. The differential limiting torque of the electromagnetic clutch 30 is determined so as to increase as the previous rotational speed difference ΔN increases. This eliminates the fact that the torque distribution clutch acts in the reverse direction due to an error related to the diameter difference between the front and rear wheels in relation to increasing the traction of the vehicle.

t _ref = t _df + t _dn (3)

t _df = (1/2) [t _in −M _tindf (V)].
[(L _F / L) + (H _CG / L · G _X )] (4)
However, t _df ≧ 0

When the diameter difference correction coefficient kik ≦ 1.0, t _dn = M _thnA (ΔN ′) + M _thnB (ΔN) (5-1)
When the diameter difference correction coefficient kik> 1.0, t _dn = M _thnA (ΔN) + M _thnB (ΔN ′) (5-2)

Since the electromagnetic clutch 30 only limits the differential between the front wheel and the rear wheel as in this embodiment, torque is transmitted from the wheel with the higher rotational speed to the wheel with the lower speed. In some cases, the direction of the driving torque is reversed between 24 and 26 and the rear wheels 38 and 40. For example, braking torque may be generated in the rear wheels 38, 40 when the vehicle has a tire diameter of the front wheels 24, 26 larger than the tire diameter of the rear wheels 38, 40, and the vehicle is running at a slow acceleration. , 26 and the rear wheels 38, 40 are increased in slip rate to reduce their lateral force, thereby impairing the straight running stability of the vehicle. When this is considered in the front and rear wheel two-wheel model, it is as shown in Formula 6. Here, I _r is the moment of inertia of the output side rotating body of the electromagnetic clutch 30 converted around the output shaft 62, and _If is the moment of inertia of the input side rotating body of the electromagnetic clutch 30 as the drive pinion 44 (input shaft). 58) Converted around. Ω _f and ω _r are rotational angular velocities of the input shaft 58 and the output shaft 62, μ (sf) and μ (sr) are longitudinal force coefficients of the front wheels 24, 26 and the rear wheels 38, 40, and W _f and W _r. Is the ground load of the front wheels 24, 26 and the rear wheels 38, 40, sf and sr are slip ratios of the front wheels 24, 26 and the rear wheels 38, 40 [= (R _f ω _f −V) / R _f ω _f , and (R _r ω _r −V) / R _r ω _r ], R _f and R _r are dynamic load radii of the front wheels 24 and 26 and the rear wheels 38 and 40.

_{I f · dω f / dt =} t in + t r -μ (sf) · W f · R f ··· (6-1)
I _r · dω _r / dt = −t _r −μ (sr) · W _r · R _r (6-2)

In the above equation 6, since it can be considered that dω _f / dt = 0 and dω _r / dt = 0 in steady running, equation 7 is obtained. As shown in FIG. 9, the front / rear force coefficient of the front wheels 24, 26 or the rear wheels 38, 40 (coefficient corresponding to the driving force generated on the wheels) is within the range A where the wheel slip ratio is relatively small. Since it is linear with respect to the slip ratio, it is proportional to the slip ratio sf of the front wheels 24 and 26 and the slip ratio sr of the rear wheels 38 and 40 as shown in Equation 8, while the dynamic load radius R _{f of the} front wheels 24 and 26 is Since the dynamic load radii R _r of the rear wheels 38 and 40 have the same value R, the above Equation 7 is rewritten as shown in Equation 9.

t _in −t _r −μ (sf) · W _f · R _f = 0 (7-1)
_{t r -μ (sr) · W} r · R r = 0 ··· (7-2)

μ (sf) = K · sf (8-1)
μ (sr) = K · sr (8-2)

t _in −t _r = K · sf · W _f · R _f (9-1)
t _r = −K · sr · W _r · R _r (9-2)

When the torque distribution is controlled between the front wheel drive and the four wheel drive as in the present embodiment, the above-described equations (9-1) and (9-2) 9 can be expressed as sf = (t _in −t _r ) / (K · W _f · R _f ) and sr = (− t _r ) / (K · W _r · R _r ). Therefore, when the input torque t _in is positive, as the transmission torque t _r of the electromagnetic clutch 30 is increased, the absolute value of the front wheel slip ratio | sf | and the rear wheel slip ratio absolute value | sr | is increased by Thus, as shown in FIG. 13, the lateral force of the wheels is reduced, and the straight running stability is impaired. Therefore, when the rear wheels 38 and 40 rotate faster than the front wheels 24 and 26 due to the difference in diameter, the slip ratio of the rear wheels 38 and 40 during driving (acceleration) is lowered to improve the straight running stability. Even when the differential limiting clutch by the electromagnetic clutch 30 is set to zero and the front wheels 24 and 26 rotate faster than the rear wheels 38 and 40 due to the opposite diameter difference, the slip ratio of the rear wheels 38 and 40 during braking is reduced. In order to improve the straight running stability by lowering it, it is desirable to make the differential limiting clutch by the electromagnetic clutch 30 zero. Therefore, the relationship between FIGS. 11 and 12 is selectively used according to the diameter difference.

As shown in FIG. 6, the normal travel time control means 260 has a map value (travel resistance related amount) obtained based on the vehicle speed V from the input torque tin and the previously stored relationship shown _in FIG. ) Based on M _tindf (V), reference torque calculation means 278 for obtaining a reference torque command value t _df , and corresponding to the rotation speed difference based on the rotation speed difference ΔN and the corrected rotation speed difference ΔN ′ from Equation 5 above. Rotational speed difference corresponding torque command value calculating means 280 for obtaining a torque command value t _dn having a magnitude to be determined, the reference torque command value t _df obtained by the reference torque calculating means 278 and the rotational speed difference corresponding torque command value calculating means 280 Torque command value calculating means 282 for calculating the torque command value t _ref from the torque command value t _dn obtained by the above and outputting it to the electromagnetic clutch 30 is included.

The torque command value t _ref output from the torque command value calculation means 282 is supplied to the electromagnetic clutch 30 via the torque command value processing means 284. The torque command value processing means 284 includes a torque command value t _ref in order to avoid inconvenience due to the execution of ABS control even if the braking time control means 254 is not started due to some trouble such as the brake sensor 104. Torque command value limiting means 286 for limiting the torque and smoothing processing means 288 for smoothing the torque command value t _ref that is sequentially output using well-known low-pass processing, moving average processing, smoothing processing, or the like. It is. In the torque command value limiting means 286, the torque command value t _ref is limited between a preset maximum value T _max and minimum value T _pre (≈0). Usually, since the ABS control is performed is when operating the brake, since the input torque t _in the accelerator pedal operation amount is a substantially zero is very small value, the maximum value T _max is It is set to a relatively small and equal to or less than the input torque t _in value. Further, since the necessary torque does not become larger than t _in even during normal acceleration, there is no problem in other control even if such a restriction is provided.

FIGS. 14 to 16 are flowcharts for explaining the main part of the control operation of the electronic control unit 110. FIG. 14 is a control mode determination routine, FIG. 15 is a torque distribution control routine during normal running, and FIG. 16 shows a torque command value t _dn calculation routine derived from the differential rotation speed of FIG.

FIG. 14 corresponds to a part of the torque distribution clutch control means 120. In the figure, after the vehicle speed V, the steering angle δ, the output signal of the brake sensor 104, etc. are read in a step (not shown), in step (hereinafter step is omitted) S1, it is determined whether or not the brake pedal 102 has been operated. This is determined based on a signal from the sensor 104. If the determination in S1 is affirmative, this routine is terminated after the braking control is selected and executed in S2 corresponding to the braking control means 254. However, if the determination in S1 is negative, it is determined in S3 whether or not the vehicle speed V is equal to or lower than a preset determination reference vehicle speed V _S. This determination reference vehicle speed V _S is a value for determining the pre-stored area 1) shown in FIG. If the determination in S3 is negative, it is determined in S4 whether or not the absolute value of the steering angle δ is greater than or equal to a predetermined determination reference angle M _delta (V). This determination reference angle M _delta (V) is a function value for determining a pre-stored area 3) shown in FIG. 7, that is, a turning control area, for example, 40 to 50 when the vehicle speed V is V _S. Within the range of °, preferably about 45 °, and when the vehicle speed V is within the range of 55 to 65 km / h, preferably 60 km / h, it is within the range of 15 to 25 °, preferably 20 °. However, when the vehicle speed V exceeds 60 Km / h, the value is saved. If the determination in S4 is negative, the yaw rate deviation e [= (r ° −r) sign (r)] and its change in S5 corresponding to the turning state detection means 270 and the turning travel time control command means 272. The rate de / dt is detected as a turning state, and whether or not the turning state is within a predetermined rule, for example, a yaw rate deviation e [= (r ° −r) sign (r)] is set in advance. whether been is a criterion value K _MAPE or more and change rate de / dt of the yaw rate deviation e is preset criterion value K _MAPB more is determined.

The determination reference values K _MAPE and K _MAPB are values set to determine that a relatively large understeer has occurred in the early _stage of the turning operation. Further, the target yaw rate r ° is set to the actual target stability factor K _h , the vehicle speed V, the steering angle δ, the steering wheel, etc. It is calculated based on the gear ratio R _st between the wheel 93 and the front wheels 24 and 26 and the wheel base L. The target stability factor K _h is a function [K _{h of the} longitudinal acceleration G _X and the combined acceleration G _XY [= √ (G _X ² + G _Y ² ]) experimentally obtained in advance to show an ideal steering. = F (G _X , G _XY )], which indicates an understeer characteristic when it is positive (K _h > 0) and a neutral steer characteristic when it is zero (K _h = 0) , It exhibits oversteer characteristics when it is negative (K _h <0).

r ° = V · δ / (K _h · V ² +1) R _st · L (10)

If any of the determinations in S4 and S5 is affirmed, the turning time control is executed in S6 corresponding to the turning time control means 258. However, if the determination in S4 and S5 are both negative, step S7 corresponding to the torque distribution control selection delay means 266, whether the determination of a predetermined number N _D of the time control turning, in other words if, whether normal running control has passed a delay of a predetermined number N _D min after being determined during the execution of the time control turning is determined. If the determination at S7 is negative, the control at the time of turning traveling at S6 is continued, but if the determination is affirmative, the control at normal driving is executed at S8 corresponding to the control means 260 at normal driving.

If the determination in S3 is affirmative, at S9 corresponding to the torque distribution control selection delay means 266, whether the determination of a predetermined number N _S from time turning control, in other words, when turning whether the delay time from the start time of control during the control executed is determined corresponding to the execution time of a predetermined number N _S content of the control cycle has elapsed. When the determination at S9 is negative, the control at the time of turning traveling at S6 is continued, but when the determination is affirmative, the control at start is executed at S10 corresponding to the start time control means 256. That is, when switching from control during turning to other control, the left and right turning travel is continuously repeated by actually switching after a predetermined delay time has elapsed since the determination of other control. In a winding road or the like, it is suitably suppressed that the turning control and the normal driving control or the starting control are frequently repeated within a short time.

In the normal running control routine of FIG. 15, in SQ1 corresponding to the reference torque calculating means 278, based on the actual input torque t _in and the map value M _tindf (V) which is a function of the vehicle speed from the equation (4), A reference torque command value t _df for obtaining torque distribution of the front and rear wheels corresponding to the weight distribution of the front and rear wheels by load movement is calculated. Next, in SQ2 corresponding to the rotational speed difference corresponding torque command value calculating means 280, a calculation routine for the torque command value t _dn shown in FIG. 16 is executed, and the actual diameter difference correction coefficient kik and rotational speed difference are calculated from Equation 5. Based on the map value M _thnA (ΔN) or M _thnB (ΔN) which is a function of ΔN, and the map value M _thnA (ΔN ′) or M _thnB (ΔN ′) which is a function of the corrected rotational speed difference ΔN ′, A torque command value t _dn for obtaining a differential limiting force having a magnitude corresponding to the differential rotational speed ΔN is calculated.

In FIG. 16, in SR1, whether or not the front wheel diameter that is the average diameter of the front wheels 24 and 26 of the vehicle is larger than the rear wheel diameter that is the average diameter of the rear wheels 38 and 40 is, for example, the diameter difference correction coefficient kik. Judgment is made based on whether it is greater than “1” (kik> 1). If the determination of SR1 is affirmative, in SR2, a torque command value corresponding to the rotational speed difference is obtained based on the actual rotational speed difference ΔN and the corrected rotational speed difference ΔN ′ from the previous equation (5-2). t _dn is calculated. On the other hand, if the determination of SR1 is negative, it is in a state where kik ≦ 1, so in SR3, the actual rotational speed difference ΔN and the corrected rotational speed difference ΔN ′ from the previous equation (5-1). Based on the torque command value t _dn corresponding to the rotational speed difference.

Returning to FIG. 15, in SQ 3 corresponding to the torque command value calculation means 282, the torque command value t _ref during torque distribution control during normal running is calculated from the above-described reference torque command value t _df and torque command value t Calculated based on _dn . Next, in SQ4 corresponding to the torque command value limiting means 286, when the calculated torque command value t _ref is greater than or equal to a preset upper limit value T _max (t _ref ≧ T _max ), When the torque command value t _ref is not larger than the preset lower limit value T _PRE (t _ref ≦ T _PRE ), the lower limit value is limited to the upper limit value T _max (t _ref = T _max ). By limiting to T _PRE (t _ref = T _PRE ), the range of change is limited. Further, when the torque command value t _ref exceeds a value (| t _ref | + T _dup ) obtained by adding a predetermined increase amount T _dup to the input torque | t _ref | Limited. Thereby, even when the differential limiting torque cannot be reduced to zero due to some failure during the ABS control operation, the deterioration of the ABS control performance and the heat generation of the differential limiting device are suitably prevented. Normal setting, the ABS control is actuated effected even if you are working with a brake since no will depress the accelerator pedal, the input torque t _in is substantially zero, the upper limit value T _max is a very small value Is done. Further, since the required torque even in such as during normal acceleration not the input torque t _in above, all no problem be previously provided with the restriction in the case.

Next, in SQ5 corresponding to the smoothing processing means 288, in order to avoid a sudden change in the torque command value t _ref due to switching of the control mode or the like, low-pass filter processing, moving average processing, or the like is performed on the torque command value t _ref . The smoothing process or the smoothing process is executed. In particular, when the normal travel time control is selected from the start time control, the torque command value t _ref is suddenly reduced and the occurrence of drive system vibration is expected. However, the torque command value t _ref is obtained by the annealing process of SQ5. The generation of vibration is suppressed by being gradually changed. In SQ6, the torque command value t _ref subjected to the annealing process is output for torque distribution control.

FIG. 17 shows a torque distribution control routine for turning travel corresponding to the turning time control means 258, and shows control for distributing torque so that the actual yaw rate r follows the target yaw rate r °. In this SH4, since the target yaw rate r ° is determined so as to decrease as the longitudinal acceleration G _X increases and increases as the combined acceleration G _XY increases, the road surface friction coefficient μ is not necessarily detected directly. Therefore, the target yaw rate r ° can be determined using the horizontal acceleration that can be detected relatively easily, and natural turning behavior of the vehicle is realized.

In SH1 in Fig. 17, the engine torque (input torque) t _in, input and output rotational speed difference of the electromagnetic clutch 30 by the differential rotational speed .DELTA.N (rotational speed of the propeller shaft 28 - rotational speed of the drive pinion 44), the steering angle [delta], The corrected longitudinal acceleration G _X and lateral acceleration G _Y , their combined acceleration G _XY , yaw rate r, front wheel side slip angle β _f , rear wheel side slip angle β _r , and road surface friction coefficient μ are read or calculated. Then, the SH2 corresponding to the target stability factor calculating means, target stability factor K _h on the basis of the longitudinal acceleration G _X and the lateral acceleration G _Y a predetermined stored relationship is determined. Also, subsequent to this, the SH3 corresponding to the target stability factor smoothing processing means, a low-pass filtering performed as smoothing processing to slowly varying sequentially the obtained target stability factor K _h in the SH2 Is done. Thus, variation in the target stability factor K _h be unstable behavior not keep up control even when intense than the torque responsiveness is suitably prevented. The time constant of the low-pass filter processing is a value of about 0.2 to 0.3 seconds, and is a value that is orders of magnitude larger than the time constant of the low-pass filter processing for removing noise from the input signal. Has been.

The target yaw rate determining means corresponding to SH4, actual target stability factor K _h from Equation 10 that has been previously stored, the vehicle speed V, the steering angle [delta], the gear ratio between the steering wheel 93 and front wheel 24, 26 R _st, A target yaw rate r ° is calculated based on the wheel base L. Subsequently, in SH5 corresponding to the yaw rate deviation calculating means, the deviation e [= (r ° −r) sign (r) between the target yaw rate r ° and the actual yaw rate (rotational angular velocity around the vertical line passing through the center of gravity of the vehicle body) r. ] Is calculated. Next, in SH6 corresponding to the control gain determining means, the control gains G _O , G _tin , G _P , G _I , G _D , and G _S of the control equation for turning torque distribution control stored in advance are determined. . Since these control gains G _O , G _tin , G _P , G _I , G _D , and G _S may be constant values, in such a case, values stored in advance are read out, but more preferably a predetermined definition is used. Calculated from the formula. In SH7, the deviation e and the gains G _O , G _tin , G _P , and the like are _calculated from the torque distribution control equation during turning for making the actual yaw rate r follow the target yaw rate r °, that is, for eliminating the yaw rate deviation e. Based on G _I , G _D , and G _S , a control value for the electromagnetic clutch 30, that is, a command value t _ref for instructing transmission torque to the electromagnetic clutch 30 is sequentially calculated.

Next, in SH8 corresponding to the control amount correcting means, when the condition (sign (r) = sign (δ) = sign (dδ / dt)) at the time of the cutting operation of the steering wheel 93 is satisfied, the steering wheel 93 is returned. when satisfying the operating time of a is condition [sign (r) ≠ sign (dδ / dt) ], the correction amount t _s based on the input torque t _in and the steering angle δ is determined and controlled amount calculated in SH7 i.e. The command value t _ref (= t _ref + t _s ) is corrected by adding the correction amount t _s to the torque command value t _ref . Subsequently, in SH9 corresponding to the limit value determining means and the control amount limiting means, the maximum torque t _max and the minimum torque t _min for limiting excessive torque transmission and excessive slip by limiting the range of the command value t _ref. limited but is calculated based on the in advance from stored relationship of input torque t _in and the electromagnetic clutch 30 a rotational speed difference .DELTA.N, the command value t _ref obtained in SH7 is its maximum torque t _max and minimum torque t _min Is done. Then, in SH11 corresponding to the current value conversion means, for example, the command value t _ref is converted into a signal indicating the drive current of the electromagnetic clutch 30 from the previously stored relationship shown in FIG. 3, and then the signal is driven in SH12. It is output to the circuit 118.

As described above, according to the present embodiment, the map value M _tindf (V), which is the travel resistance-related amount calculated by the travel resistance-related amount calculation unit 276, is obtained by the torque distribution clutch control unit 120 (SQ1, SQ3). Based on this, the transmission torque _tr (= t _ref ) of the electromagnetic clutch 30 is controlled, so that the fuel efficiency of the vehicle and the durability of the torque distribution clutch are enhanced. That is, since the torque distribution clutch control means 120 may be one which decreases toward the transmission torque t _r (= t _ref) the zero of the electromagnetic clutch 30 as the input torque t _in the electromagnetic clutch 30 is reduced, the input torque t _in the while if the map value _M tindf (V) is greater than acceleration performance is distributed large torque through the electromagnetic clutch 30 is increased, when the input torque t _in the map value _M tindf (V) is smaller than Thus, the engagement load in the electromagnetic clutch 30 is suppressed, and the fuel consumption of the vehicle and the durability of the torque distribution clutch are further enhanced.

Further, according to this embodiment, the torque distribution clutch control means 120 (SQ2, SQ3) corrects the actual rotation speed difference ΔN calculated by the rotation speed difference calculation means 124 and the rotation speed difference correction means 132. Since the transmission torque _tr (= t _ref ) of the electromagnetic clutch 30 is controlled based on the subsequent rotational speed difference ΔN ′, the actual rotational speed difference ΔN between the input side rotating body and the output side rotating body of the electromagnetic clutch 30 is controlled. Of the transmission torque control corresponding to the rotational speed difference due to the difference between the rotational speed difference and the rotational speed difference ΔN ′ corrected by the rotational speed difference correcting means 132 is preferably eliminated, and the torque distribution control accuracy is further enhanced. It is done.

Further, according to this embodiment, the torque command value limiting unit 286 (SQ4), T _max and the maximum value of the torque command value t _ref for controlling the transmission torque t _r of the electromagnetic clutch 30 is set in advance input since restricted so as not to over torque t _in, if not the torque distribution control at the time of braking in connection with not successful for some reason the detection of a braking operation, such as failure of the switch or circuit is performed However, during braking, the torque distribution clutch transmission torque does not become excessive in relation to the ABS control, and the deterioration of the ABS performance and the heat generation of the torque distribution clutch are avoided.

  Further, according to the present embodiment, the torque distribution control selection delay means 266 (S7, S9) is used, and the torque distribution control determination means 264 (S3, S4, S5) is used to determine the control from turning time to other torque distribution control. Since the other torque distribution control is selected based on the elapse of a predetermined time from the determination, for example, in the winding or slalom traveling where the left and right cornering are repeatedly performed, the torque distribution during the cornering is performed. The state in which the turning traveling control for executing the control and the normal traveling control or the starting control for executing the torque distribution control during the straight traveling are repeatedly selected within a short time, that is, frequent switching of the control mode is preferably eliminated. The

Further, according to the present embodiment, the actual turning state of the vehicle detected by the turning state detecting means 270 (S5) by the turning time control selection means 272 (S5), for example, the yaw rate deviation e or its change rate de / dt. _{Exceeds the} predetermined judgment reference values K _MAPE and K _MAPB , a command for switching to the turning control is issued even when the turning control based on the vehicle turning operation amount, that is, the steering angle δ is not determined. Since the output is output and the torque distribution control selection means 252 (S6) preferentially selects the turning time control, the turning response of the vehicle at the start of the turning operation is enhanced by the quick start of the turning time control.

  Further, according to the present embodiment, the torque distribution control selection means 252 (S4, S5, S7) causes any one of the plurality of types of areas stored in the area storage means 262 to include the vehicle speed detection device (vehicle speed calculation means 178) and Based on whether the vehicle indicated by the vehicle speed V and the steering angle δ detected by the steering angle detection device (steering angle sensor 94) belongs, one torque distribution control is automatically selected from the plurality of types of torque distribution controls. Therefore, torque distribution control adapted to various driving conditions of the vehicle is automatically obtained.

FIG. 18 is a flowchart for explaining another control operation of the electronic control unit 110, and shows a two-wheel / four-wheel drive switching control routine. In the figure, at ST1, it is determined based on a signal from the four-wheel drive selection switch 80 whether or not a four-wheel drive control state in which torque distribution control is performed is selected. If the determination in ST1 is negative, the operation indicator lamp 112 indicating the four-wheel drive control operation state is turned off in ST2. However, if ST1 positive judgment is made, in ST3, whether or not the rotational speed difference .DELTA.N is an input-output differential speed of the electromagnetic clutch 30 is equal to or less than a preset determination reference value .DELTA.N _sw is determined The Further, determination of ST3 is if it is affirmative, in ST4, whether throttle opening theta _th is equal to or less than a preset determination reference value theta _sw is determined. The determination reference values ΔN _sw and θ _sw are required to protect the friction plates 42 and 46 of the electromagnetic clutch 30 from damage when the 2 (front) wheel drive state is switched to the 4 wheel drive control state. a value corresponding to the rotational speed difference ΔN and the input torque t _in, those obtained experimentally in advance.

  If any of the determinations in ST3 and ST4 is negative, the friction plates 42 and 46 of the electromagnetic clutch 30 may be damaged if the four-wheel drive control state is immediately set, so that such damage is prevented. For this reason, the 2 (front) wheel drive state is maintained in ST5, and the operation indicator lamp 112 is blinked in ST6, so that the four-wheel drive selection switch 80 is operated for the driver. It shows that it is still in the 2 (front) wheel drive state. However, if both the determinations of ST3 and ST4 are affirmed, there is no risk of damaging the friction plates 42 and 46 of the electromagnetic clutch 30 even if the four-wheel drive control state is set immediately. The state is changed to the four-wheel drive control state, and in ST8, the operation indicator lamp 112 is continuously turned on to indicate to the driver that the vehicle is in the four-wheel drive control state.

FIG. 19 is a flowchart for explaining another control operation of the electronic control unit 110, and shows a start time torque distribution control routine corresponding to the start time control means 256. In SU1, when the shift position is not in the reverse range, the value H _CX0 for excluding the error range is subtracted from the longitudinal acceleration G _X0 detected by the longitudinal G sensor 90, so that When the acceleration G _X1 is determined and the shift position is in the reverse range, it is a reverse climb, so the value H _CX0 for excluding the error range is subtracted from the longitudinal acceleration −G _X0 detected by the longitudinal G sensor 90. Thus, the longitudinal acceleration G _X1 when the vehicle stops corresponding to the uphill road surface gradient is determined. In the subsequent SU2, a pre-torque t _st0 to be added according to the inclination is calculated based on the longitudinal acceleration G _X1 from the equation (11). In Equation 11, M _V is the vehicle weight, L _F is the distance from the center of gravity of the vehicle to the front wheel axis, L is the wheel base of the vehicle, R _W tire radial, I _DR is the gear ratio of the rear differential gear device 32, G _Z is the gravitational acceleration.

_{t st0 = M V · G X1} · (L F / L) · (R W / I DR) · G Z ··· (11)

In SU3, based on the rotational speed difference ΔN ′ after the diameter difference correction and the absolute value | δ | of the steering angle from the map stored in advance, the differential rotational speed feedback coefficient k _sn corresponding to the torque generated by the differential rotation. [= M _ksn (ΔN ′, | δ |)] is calculated. The above map is mainly for the transmission torque having a magnitude corresponding to the rotational speed difference ΔN, but the steering angle | δ | is added to avoid the influence of the tight corner. In subsequent SU4, based from Equation 12 above differential speed feedback coefficient k _sn, the input torque t _in, starting at the reference torque t _st for obtaining a torque distribution corresponding to the weight distribution is calculated. In Equation 12, _HCG is the height of the center of gravity of the vehicle. The value in parentheses on the right side of Equation 12 is a coefficient value for performing torque distribution equivalent to weight distribution, and is a value that does not exceed 1.

t _st = k _sn · t _in · (L _F / L + H _CG / L · G _X ) (12)

In SU5, a torque command value t _ref (= t _st + t _st0 ) which is a control torque at the time of start is calculated. When the shift position is the parking range or the neutral range, the torque command value t _ref is set to zero, is limited between the preset minimum value T _PRE and the maximum value T _MAX , and the input torque t _in It is limited not to exceed. In subsequent SU6, is smoothed by the variation of the torque command value t _ref is limited. Thus, at the time of starting, a basic torque distribution corresponding to the weight distribution between the front and rear wheels, since the transmission torque t _r corresponding to the increase in the rotational speed difference ΔN is obtained, traction performance of the vehicle can be secured and the electromagnetic clutch 30 It is possible to prevent a wasteful current from being applied to.

Next, at SU7, an N → D shift abnormality determination routine shown in FIG. 20 is executed to determine whether or not the torque command value t _ref is equal to or greater than a torque value equivalent to weight distribution (equivalent to direct connection). . In SV1 of FIG. 20, it is determined whether an N → D shift has been performed. If this SV1 positive judgment is made, the SV2, whether the engine rotational speed N _E is preset determination reference value N _EJO more is determined. It is determined whether or not the determination reference value N _EJO is a high rotational speed that may damage the torque converter of the automatic transmission 12. If any of the determinations of SV1 and SV2 is negative, the N → D shift is assumed to be normal in SV3. However, if both of the determinations of SV1 and SV2 are positive, an N → D shift is performed. since the engine rotational speed N _E is in a state which is abnormally high engine speed as there is a risk that damage of the torque converter occurs when the, it is determined that the N → D shift anomaly.

If the determination of SU7 is negative, SU9 is directly executed. If the determination is positive, SU9 is executed after the torque command value t _ref is limited to a torque corresponding to weight distribution in SU8. Further, in SU9, N → D operation when the engine rotational speed N _E of the shift lever is whether higher N → D shift anomaly than a predetermined value is determined. When the determination of SU9 is negative, SU11 is directly executed and the torque command value t _ref is output. However, when the determination is positive, SU11 is executed after the torque command value t _ref is set to zero in SU10. Is done. Thereby, when it is determined that the N → D shift is abnormal, the torque command value t _ref is set to zero and the electromagnetic clutch 30 is released, so the impact is mitigated by the slip of the front wheels 24, 26, Damage to the torque converter of the automatic transmission 12 due to a sudden increase in rotation due to the N → D shift is prevented and protected.

  FIG. 21 is a flowchart for explaining another control operation of the electronic control unit 110, and a sensor fail processing routine for continuing the torque distribution control regardless of the failure of the sensor related to the torque distribution control. It is. The sensors related to the torque distribution control are, for example, the front / rear G sensor 90, the left / right G sensor 92, the rudder angle sensor 94, the throttle sensor 96, the engine rotation speed sensor 98, and the like. , Generally indicated as sensor C. In SW1 in the figure, it is determined whether or not the sensor A is abnormal. If the determination at SW1 is negative, it is determined at SW3 whether sensor B is abnormal. If the determination at SW3 is negative, it is determined at SW5 whether sensor C is abnormal. If the determination of SW5 is negative, this routine is terminated. However, if the determination of SW1, SW3, or SW5 is affirmed, it is necessary for SW2, SW4, or SW6 to drive the vehicle with the default value of sensor A, sensor B, or sensor C, that is, the four-wheel drive state. A provisional value that can be safely set is set. For example, when the rudder angle sensor 94 is abnormal, the rudder angle δ is set to zero. As a result, even if the sensor fails on, for example, a frozen road or a snowy road, the performance decreases, but the four-wheel drive state is continued to ensure the traction performance. Incidentally, in the conventional four-wheel drive control device, since the two-wheel drive state is set by the sensor failure, there is a risk that it may be difficult to travel on an icy road or a snowy road.

FIG. 22 is a flowchart for explaining another control operation of the electronic control unit 110, and shows a torque distribution clutch failure determination routine. In the figure, at SX1, the rotational speed difference ΔN (= N _f −N _r ) on the input / output side of the electromagnetic clutch 30 is calculated in the same manner as the rotational speed difference calculating means 124 described above. In subsequent SX2, the diameter difference correction of the rotation speed difference ΔN is performed in the same manner as the rotation speed difference correction means 132 described above, and the corrected rotation speed difference ΔN ′ is calculated. Next, in SX3, the ideal wheel rotation speed N _f around the propeller shaft 28 (input shaft 58), the rear wheel rotation speed N _r around the output shaft 62, the steering angle δ, and the steering gear ratio I _STR are calculated based on Equation 13. A rotational speed difference (differential rotational speed) ΔN _{g in a} state where there is no wheel slip is calculated. This expression 13 represents the rotational speed difference ΔN _g during turning in an ideal state where the wheels rotate together with the road surface, and ΔN = ΔN _g unless there is a failure such as the friction plate of the electromagnetic clutch 30 being stuck. .

ΔN _g = N _f · (1-cos (δ / I _STR )) (13)

In subsequent SX4, the actual rotational speed difference .DELTA.N is or less than the rotational speed difference .DELTA.N _g of the ideal state is determined. If the determination in SX4 is negative, the routine is terminated because the electromagnetic clutch 30 is not in an abnormal state, but if the determination is positive, mechanical causes such as frictional plate adhering, cam mechanism abnormality, etc., current For example, it is considered that there is a sticking abnormality as shown by a solid line in FIG. 23 due to an electrical cause such as a sensor or solenoid abnormality. Therefore, in SX5, a failure signal indicating a sticking abnormality of the electromagnetic clutch 30 is output, and the abnormality The indicator lamp 114 is turned on.

  As mentioned above, although one Example of this invention was described based on drawing, this invention is applied also in another aspect.

For example, the travel resistance-related amount calculating means 276 described above calculates the driving torque at the time of flat land constant speed straight traveling based on the vehicle speed V from the relationship shown in FIG. Other amounts such as the throttle opening θ _th at the time, the fuel injection amount, and the intake / intake amount of the engine 10 may be used. In short, any amount related to running resistance may be used.

Further, although in the foregoing embodiments, the torque distribution clutch control means 120, the input torque t _in was intended to zero the torque command value t _ref when falls below the driving torque at the flat land constant speed straight running , Not necessarily zero. In short, if the torque command value t _ref is decreased in accordance with the decrease _in the input torque tin, a temporary effect can be obtained.

Further, although in the foregoing embodiments, the torque distribution control selection delay means 266, until after it is determined other control in the turning time control state for a predetermined N _D times or N _S times the determination is continuously performed Although it was delayed, it may be delayed by a timer. Further, the predetermined number of times N _D or N _{S serving} as the determination criterion may be a function such as the vehicle speed V.

Further, in the above-described embodiment, the turning time control command means 272 has the yaw rate deviation e _{equal to} or greater than the predetermined determination reference value K _MAPE and the yaw rate deviation change rate de / dt _{equal to} or greater than the predetermined determination reference value K _MAPB . Even if the judgment based on the rudder angle δ has not yet determined the turning time control when the two conditions are satisfied, the turning time control is preferentially commanded. Is intended to increase reliability, so only one of them can be used.

Further, the turning state detection means 270 of the above-described embodiment detects the yaw rate deviation e and the yaw rate deviation change rate de / dt as values indicating the actual turning state of the vehicle, but the yaw rate change rate dr / dt and the like are It may be detected. In short, it is only necessary to detect the steering state of the vehicle.

In the illustrated embodiment, in place of the throttle opening theta _th used in such when calculating the input torque t _in the output torque i.e. the electromagnetic clutch 30 of the engine 10, an accelerator pedal operation amount, the fuel injection amount of the engine 10 Or a required output quantity such as intake air quantity may be used.

  The electromagnetic clutch 30 of the above-described embodiment is provided between the propeller shaft 28 and the rear differential gear device 32, but is provided in parallel to limit the so-called center differential. Among the three shafts of the differential limiting clutch, the clutch provided between the transfer and the front differential gear unit, the propeller shaft 28 and a pair of axles on the output side of the differential gear unit connected thereto. It may be a clutch provided between any two shafts. In short, an electromagnetic or hydraulic torque distribution clutch that adjusts the ratio of torque transmitted from the prime mover to each of the plurality of wheels may be used.

  Although not illustrated one by one, the present invention can be implemented in variously modified and improved modes based on the knowledge of those skilled in the art.

It is a figure explaining with the power transmission path | route of the four-wheel drive vehicle provided with the torque distribution clutch control apparatus of one Example of this invention. FIG. 2 is a cross-sectional view illustrating a configuration of an electromagnetic clutch provided in a power transmission path of FIG. 1 in order to perform torque distribution of front wheels and rear wheels. It is a characteristic view explaining the clutch characteristic of the electromagnetic clutch of FIG. It is a figure explaining the structural example of the electronic controller of FIG. 1 in detail. It is a functional block diagram explaining the principal part of the control function of the electronic controller of FIG. 1, Comprising: It is a figure explaining the structure of a torque distribution clutch control means. FIG. 6 is a functional block diagram illustrating a main part of a control function of the electronic control device of FIG. 1, and is a diagram illustrating a configuration of a normal travel time control unit of FIG. 5. It is a figure which shows the relationship memorize | stored beforehand in order to switch several types of control modes in the torque distribution clutch control means of FIG. It is a figure which shows the relationship used in order to determine the input torque of a torque distribution clutch in the input torque calculation means of FIG. It is a figure which shows the relationship between the slip ratio of a wheel, and the longitudinal force coefficient of the wheel. FIG. 7 is a diagram showing a relationship used for _obtaining a map value M _tindf (V) having a magnitude corresponding to a running resistance in the reference torque calculation means of FIG. 6. 6 is a relation used to determine a torque command corresponding to the rotational speed difference of the torque distribution clutch in the rotational speed difference corresponding torque command value calculating means in FIG. 6 and is selected when the front wheel diameter is larger than the rear wheel diameter. FIG. 6 is a relationship used for determining a torque command corresponding to the rotational speed difference of the torque distribution clutch in the rotational speed difference corresponding torque command value calculating means in FIG. 6 and is selected when the front wheel diameter is smaller than the rear wheel diameter. FIG. It is a figure which shows the relationship between the slip ratio of a wheel, and the lateral force of the wheel. FIG. 5 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. 4 and showing a control mode determination routine. FIG. 5 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. 4, and is a diagram showing a normal running torque distribution control routine. FIG. 16 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. 4, and shows a command value t _dn calculation routine of FIG. 15. FIG. 5 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. FIG. 5 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. 4, and shows a two-wheel / four-wheel drive switching control routine. FIG. 5 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. 4, and shows a starting torque distribution control routine. FIG. 5 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. 4, and shows an N → D shift abnormality determination routine. FIG. 5 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. 4, and shows a sensor fail control routine. FIG. 5 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. 4 and showing a torque distribution clutch failure determination routine. It is a figure which shows the characteristic at the time of failure of the electromagnetic clutch of FIG.

Explanation of symbols

10: Engine (motor)
24, 26: Front wheels (wheels)
30: Electromagnetic clutch (torque distribution clutch)
38, 40: Rear wheels (wheels)
120: Torque distribution clutch control means 124: Rotational speed difference calculation means 132: Rotational speed difference correction means 252: Torque distribution control selection means 264: Torque distribution control determination means 266: Torque distribution control selection delay means 270: Turning state detection means 272 : Control command means 276 during turning traveling: travel resistance related quantity calculating means 278: reference torque calculating means 280: torque command value calculating means 286 corresponding to rotational speed difference: torque command value limiting means

Claims (2)

Control of a vehicle torque distribution clutch for controlling a transmission torque of a torque distribution clutch in a vehicle having a torque distribution clutch for adjusting a ratio of torque transmitted from a prime mover to each of a plurality of wheels so as to obtain a predetermined torque distribution A device,
A travel resistance related amount calculating means for calculating a travel resistance related amount related to the travel resistance of the vehicle;
The transmission torque of the torque distribution clutch is basically controlled based on the travel resistance related amount calculated by the travel resistance related amount calculation means so that the torque distribution corresponds to the weight distribution of the vehicle. Torque distribution clutch control means for releasing the torque distribution clutch when the actual input torque to the torque distribution clutch is smaller than the value corresponding to the vehicle running resistance during traveling and constant speed driving. A control device for a vehicle torque distribution clutch. 2. The control device for a torque distribution clutch for a vehicle according to claim 1, wherein the torque distribution clutch control means decreases the transmission torque of the torque distribution clutch toward zero as the input torque of the torque distribution clutch decreases.

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