JP4973222B2 - Driving force control device for four-wheel drive vehicle - Google Patents

Description

  In the present invention, the driving force output from the internal combustion engine is transmitted to one of the front wheels or the rear wheels, and to the other wheel via the driving force transmission device capable of changing the transmission capacity. The present invention relates to a driving force control device for a four-wheel drive vehicle to which driving force is transmitted.

  In general, in a four-wheel drive vehicle, when the transmission capacity is increased, not only the friction force generated between the one wheel and the road surface but also the friction force generated between all the wheels and the road surface can be used. Therefore, more driving force transmitted from the internal combustion engine can be applied to the road surface, and a quicker start is possible. Therefore, it is usual to increase the transmission capacity when the vehicle starts.

  However, in general, in a four-wheel drive vehicle, the driving force transmission path to one wheel on the side closer to the internal combustion engine of the front wheels or the rear wheels has higher torsional rigidity than the driving force transmission path to the other wheel. The distribution of the driving force from the internal combustion engine when the vehicle starts is transiently larger for the one wheel than for the other wheel. Therefore, when the driving force from the internal combustion engine increases when the vehicle starts, on the road surface where the frictional force generated between the wheels and the road surface is small (hereinafter referred to as “low μ road”), the one wheel is first connected to the road surface. Slip beyond the maximum static friction force between the two, and the other wheel may slip after that. Also, on such a low μ road, the dynamic friction force between the wheels and the road surface decreases as the relative speed between them increases, so that the one wheel and the other wheel slip alternately under certain conditions. In addition, a so-called self-excited vibration is generated in which the driving torque, which is the driving force transmitted to the other wheel belonging to the driving force transmission path on the lower torsional rigidity, vibrates and the amplitude tends to increase for a certain period of time.

  As a countermeasure against this self-excited vibration, it is conceivable to use a control device that prohibits the driving force transmission device from transmitting a driving force when the self-excited vibration of the other wheel is detected. For example, this is the control device disclosed in Patent Document 1.

As another countermeasure, for example, as in the third embodiment disclosed in Patent Document 2, when the self-excited vibration is detected, the ignition timing of the internal combustion engine is retarded to suppress the output of the internal combustion engine. It is conceivable to use a control device.
JP 2002-293150 A Japanese Patent Application Laid-Open No. 10-159872

  When the control device shown in Patent Document 1 or Patent Document 2 is used, the effect of suppressing the self-excited vibration of the other wheel can surely be obtained. However, when the control device of Patent Document 1 is used, the power transmission path to the other wheel is temporarily cut off and the two-wheel drive state is entered. If it is not obtained, and once it is in the cut-off state, the responsiveness of the driving force transmission device to the increase in the transmission capacity is reduced due to a gap between the engagement elements in the driving force transmission device. However, there are cases in which the quick start of the vehicle is impaired. Further, even when the control device disclosed in Patent Document 2 is used, the output of the internal combustion engine is suppressed, so that the quick start of the vehicle may be impaired.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is to drive a four-wheel drive vehicle capable of suppressing the self-excited vibration of the other wheel without impairing the rapid startability of the vehicle. It is to provide a force control device.

  In order to achieve this object, the invention according to claim 1 includes: (a) a first transmission path through which the driving force output from the internal combustion engine is transmitted to either the front wheel or the rear wheel; A driving force control device for a four-wheel drive vehicle comprising a second transmission path that is transmitted to the other wheel of the front wheel or the rear wheel via a variable driving force transmission device, and (b) the rotational speed of the front wheel And the front-rear wheel rotational speed difference, which is the absolute value of the difference between the rotational speeds of the rear wheels, is greater than or equal to a predetermined rotational speed difference determination value, the transmission capacity of the driving force transmission device is reduced, Executes transmission capacity control to increase the transmission capacity as the input / output rotational speed difference, which is a value related to the absolute value of the difference between the input rotational speed of the driving force transmission apparatus and the output rotational speed of the driving force transmission apparatus, increases. Including a transmission capacity control means.

  The invention according to claim 2 is characterized in that the transmission capacity control means executes the transmission capacity control when the vehicle speed of the four-wheel drive vehicle is equal to or lower than a predetermined vehicle speed determination value.

  The invention according to claim 3 is characterized in that the transmission capacity control means increases the rate of increase of the transmission capacity with respect to the increase amount of the input / output rotational speed difference as the number of pulsations of the front and rear wheel rotational speed difference increases. The transmission capacity control is executed.

  The invention according to claim 4 includes (a) driving force estimation means for estimating the driving force output from the internal combustion engine, and (b) the transmission capacity of the driving force transmission device based on the estimated driving force. It is determined.

  The invention according to claim 5 is characterized in that the vehicle speed determination value is variable.

  According to a sixth aspect of the present invention, in the case where the transmission capacity control means executes the transmission capacity control of the driving force transmission device, the driving force transmission device is not in a shut-off state where the driving force is not transmitted to the other wheel. It is characterized by that.

  In the four-wheel drive vehicle, the driving force from the internal combustion engine is branched into the first transmission path and the second transmission path, and the driving force is input to the driving force transmission device in the second transmission path. Since the output is transmitted to the other wheel, the input rotational speed of the driving force transmission device corresponds to the rotational speed of the one wheel, and the output rotational speed of the driving force transmission device is the other wheel. It can be said that the input / output rotational speed difference of the driving force transmission device corresponds to the front / rear wheel rotational speed difference. The larger the input / output rotational speed difference is, the larger the transmission capacity of the driving force transmission device is. For example, when the driving force transmission device includes an engagement element, the input / output rotational speed difference is large. In other words, the engagement force of the engagement element is increased.In other words, as the input / output rotational speed difference increases, the driving force transmission device functions like a damper that increases the rotational resistance to suppress it. The function is to reduce the front-rear wheel rotational speed difference corresponding to the input / output rotational speed difference. According to the first aspect of the present invention, when the front-rear wheel rotational speed difference is greater than or equal to the predetermined rotational speed difference determination value, that is, when it is determined that self-excited vibration of the other wheel has occurred. After the transmission capacity of the driving force transmission device is reduced, transmission capacity control is executed to increase the transmission capacity as the input / output rotational speed difference increases. In this case, the transmission capacity is temporarily reduced. As a result, the excessive driving force to the other wheel is suppressed to suppress the self-excited vibration, and the driving force transmission device reduces the input / output rotational speed difference as the input / output rotational speed difference increases. The self-excited vibration can be led to convergence at an early stage.

  Experiments have revealed that the self-excited vibration can occur when the vehicle starts, that is, when the vehicle speed is low. According to the invention according to claim 2, the vehicle speed of the four-wheel drive vehicle is a predetermined vehicle speed determination value. When the self-excited vibration is generated, the self-excited vibration is suppressed by the execution of the transfer capacity control, and the self-excited vibration is not generated. Can transmit a sufficient driving force to the other wheel without reducing the transmission capacity.

  According to a third aspect of the present invention, when the transmission capacity control means executes the transmission capacity control, the amount of increase in the input / output rotational speed difference increases as the number of pulsations of the front / rear wheel rotational speed difference increases. Since the increase rate of the transmission capacity is increased, the driving force is set so as to reduce the input / output rotational speed difference earlier with respect to the increase amount of the input / output rotational speed difference as the number of pulsations increases. The transmission device operates, and the self-excited vibration can be led to convergence at an early stage.

  According to the fourth aspect of the present invention, the driving force estimating means for estimating the driving force output from the internal combustion engine is included, and the transmission capacity of the driving force transmission device is determined based on the estimated driving force. The transmission capacity is not reduced more than necessary, and the vehicle can be started quickly.

  According to the fifth aspect of the present invention, since the vehicle speed determination value is variable, the vehicle speed determination value is changed to a low value when it is determined that an early vehicle start is requested by the accelerator opening or the like. Thus, execution of the transmission capacity control for once reducing the transmission capacity can be suppressed, and the vehicle can be started at an early stage.

  Once the driving force transmission device is in a cut-off state, the response of the driving force transmission device to a request for increase in transmission capacity is reduced, but according to the invention according to claim 6, when performing the transmission capacity control, Since the transmission capacity control means does not shut off the driving force transmission device, the responsiveness of the driving force control device when increasing the transmission capacity can be maintained high, and the driving force is also applied to the other wheel. Is transmitted and the vehicle can be started immediately.

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

  FIG. 1 is a diagram for explaining a four-wheel drive vehicle 10 according to the first embodiment and a main part of a control system that controls an electronic control coupling 12. The four-wheel drive vehicle 10 is a vehicle based on an FF (front engine / front drive) vehicle that can be selectively switched to a four-wheel drive mode or a two-wheel drive mode by an electronic control coupling 12. In FIG. 1, the driving force (torque) from the engine 14 that is a driving force source includes a clutch 16 having a torsional damper (not shown), a constant meshing transmission 18, a front wheel differential gear device 20, and a pair of left and right gears. While being transmitted to a pair of left and right front wheels 24l and 24r (hereinafter simply referred to as front wheels 24 unless otherwise distinguished) via front wheel axles 22l and 22r, the constant mesh transmission 18, transfer 26, propeller shaft 28, electronic A pair of left and right rear wheels 34l and 34r (hereinafter simply referred to as rear wheels 34 unless otherwise specified) via the control coupling 12, the rear wheel differential gear device 30, and a pair of left and right rear wheel axles 32l and 32r. Is transmitted to. The four-wheel drive vehicle 10 is provided with an electronic control device 36 for controlling the electronic control coupling 12. The path for transmitting the driving force from the engine 14 to the front wheels 24 corresponds to the first transmission path of the present invention, and the path for transmitting the driving force from the engine 14 to the rear wheels 34 is the first of the present invention. Since the rear wheel 34 is farther from the engine 14 than the front wheel 24, the torsional rigidity of the second transmission path is lower than that of the first transmission path. Therefore, the wheel in which self-excited vibration can occur in the four-wheel drive vehicle 10 is the rear wheel 34 belonging to the second transmission path.

  The engine 14 corresponding to the internal combustion engine of the present invention is, for example, an internal combustion engine such as a gasoline engine or a diesel engine that generates a driving force by combustion of fuel injected in a cylinder. The constant mesh transmission 18 includes an input shaft 38 to which the driving force of the engine 14 is directly transmitted via the clutch 16 and a counter shaft 40 disposed in parallel to the input shaft. A plurality of input gears 42 are provided on the input shaft 38 so as to be integrally or relatively rotatable. Further, the counter shaft 40 is provided with a plurality of counter gears 44 so as to be integrally or relatively rotatable, and is always meshed with the input gear 42. Thus, a plurality of transmission gear pairs 46 for establishing a plurality of shift speeds are formed by the pair of input gears 42 and the counter gear 44 that mesh with each other. Here, for example, when a certain shift speed is selected by the shift lever 72, a predetermined meshing clutch with a synchronizer is engaged, so that power is transmitted to the shift gear pair 46 corresponding to the shift speed.

  Specifically, for example, when the corresponding transmission gear pair 46 is rotatable relative to the counter shaft 40 on the counter gear 44 side and rotated integrally with the input shaft 38 on the input gear 42 side, The counter gear 44 and the counter shaft 40 are rotated integrally by a not-shown meshing clutch with a synchronizer provided on the shaft 40, and power is transmitted to the transmission gear pair 46. On the other hand, if the corresponding transmission gear pair 46 is rotatable relative to the input shaft 38 on the input gear 42 side, and is rotated integrally with the counter shaft 40 on the counter gear 44 side, it is provided on the input shaft 38. The input gear 42 and the input shaft 38 are rotated in synchronism with each other by a not-shown meshing clutch with a synchronizer, and a driving force is transmitted to the transmission gear pair 46. Then, the driving force is transmitted to the front wheel differential gear device 20 from an output gear 48 provided integrally with the counter shaft 40.

  The electronically controlled coupling 12 is disposed between the propeller shaft 28 and the rear wheel operating gear device 30 in the second transmission path that transmits driving force to the rear wheel 34 that is a wheel farther from the engine 14 than the front wheel 24. Is a driving force transmission device with variable transmission capacity provided in series. The electronic control coupling 12 controls the command value of the current supplied to the electromagnetic solenoid provided in the electronic control coupling 12 on the basis of the instruction voltage E from the electronic control device 36, thereby supplying the rear wheel 34. The driving force transmission capacity can be changed, and the driving force distributed to the front wheels 24 and the rear wheels 34 can be suitably controlled. Further, when the electronic control coupling 12 is engaged, the driving force is transmitted to the rear wheel 34 side to be in a four-wheel drive mode, which is a four-wheel drive running state, and the electronic control coupling 12 is in a driving force transmission cut-off state. In this case, the driving force is not transmitted to the rear wheel 34 side, and the two-wheel drive mode is set in the two-wheel drive running state. The electronic control coupling 12 of this embodiment is configured such that the transmission capacity of the driving force to the rear wheel 34 increases as the command voltage E increases and the amount of current supplied to the electromagnetic solenoid increases. The transmission capacity and the instruction voltage E have a one-to-one relationship.

  The electronic control device 36, which is a driving force control device of the four-wheel drive vehicle 10, includes a so-called microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like, and uses a temporary storage function of the RAM. However, by performing signal processing in accordance with a program stored in advance in the ROM, output control of the engine 14 and transmission capacity control of the electronic control coupling 12 are executed. It is configured separately for control purposes.

In FIG. 1, the operation amount Acc of the accelerator pedal 50 is detected by an accelerator operation amount sensor 52, and a signal representing the accelerator operation amount (accelerator opening) Acc is supplied to the electronic control device 36. . Further, a signal representing the depression amount θ _SC of the operation of the brake pedal 54 of the foot brake which is a service brake is supplied to the electronic control device 36.

Further, an intake air amount sensor 60 for detecting an intake air quantity Q of the engine rotational speed sensor 58, the engine 14 for detecting the rotational speed N _E of the engine 14, the intake for detecting the temperature T _A of intake air The air temperature sensor 62, the fully closed state (idle state) of the electronic throttle valve 63 of the engine 14 and the throttle valve opening sensor 64 with an idle switch for detecting the opening _θTH, and the rotational speed N _OUT of the counter shaft 40 are determined. counter shaft rotation speed sensor 66 for detecting the coolant temperature T coolant temperature sensor 68 _{for W} detecting a brake sensor 70 for the presence or absence of operation or is to detect the depression amount theta _SC of the brake pedal 54 of the engine 14, a lever position sensor 74 for detecting the lever position of the shift lever 72 (operating position) P _SH, the rotation speed of the input shaft 38 Input shaft rotational speed sensor 75 for detecting the N _IN, four-wheel respective wheel rotational speeds _{V fr, V fl, V rr} , wheels for detecting the V _rl rotational speed sensor 76, 78, 80, 82, propeller A propeller shaft rotational speed sensor 84 and the like for detecting the rotational speed NO of the shaft 28 are provided. From these sensors and switches, the engine rotational speed N _E , the intake air amount Q, the intake air temperature T _A , the throttle Valve opening θ _TH , counter shaft rotation speed N _OUT , engine coolant temperature T _W , presence or absence of brake operation or stepping amount θ _SC , lever position P _SH of shift lever 72, input shaft rotation speed N _IN , wheel rotation speed V Signals representing _fr , V _fl , V _rr , V _rl , the rotational speed NO of the propeller shaft 28 and the like are supplied to the electronic control unit 36.

Based on the input signals from these various sensors, the electronic control unit 36 controls the electronic control coupling 12 so as to perform suitable front and rear wheel torque distribution. For example, the engine driving torque is calculated from signals such as accelerator operation amount (accelerator opening) Acc, engine speed N _E , and shift lever position P _SH during start running, low μ road running, and rough road running. The driving force transmitted to the rear wheels 34 is controlled so as to ensure maximum acceleration or running performance. Further, when it is determined from the accelerator opening degree Acc and the wheel rotation speeds V _fr , V _fl , V _rr , V _rl, etc. that the driver's operation status and the vehicle are stable, the driving force applied to the rear wheel 34 By reducing the transmission capacity, the fuel consumption rate is lowered.

FIG. 2 is a functional block diagram for explaining the main part of the control function of the electronic control coupling 12 by the electronic control device 36 according to the first embodiment. In FIG. 2, the vehicle state determination means 100 determines whether or not the vehicle state is such that the self-excited vibration of the rear wheel 34 can occur, so that the wheel rotation speed V obtained from the wheel rotation speed sensors 76, 78, 80, and 82 is obtained. _The vehicle speed V is acquired based on _{fr 1} , V _fl , V _rr , V _rl, and the presence / absence of accelerator operation is acquired based on the accelerator opening Acc obtained from the accelerator operation amount sensor 52. Here, the vehicle speed V can be obtained by multiplying the wheel rotational speed by a predetermined proportional constant. For example, the vehicle speed V can be obtained by multiplying the average value of the wheel rotational speeds V _fr , V _fl , V _rr , V _rl by the proportional constant. V may be acquired, or the vehicle speed V may be acquired by multiplying the minimum value among the wheel rotation speeds V _fr , V _fl , V _rr , V _rl by the proportional constant.

The vehicle state determination means 100 has a condition that (a) the vehicle speed V is less than a vehicle speed determination value V _MAX set in advance in the vehicle state determination means 100, and (b) a self-excited vibration occurrence condition that an accelerator operation is present. If both are determined to be affirmative, a message to that effect is output to the self-excited vibration detection means 102 described later. On the other hand, if it is determined to deny any of the above conditions for the occurrence of self-excited vibration, a message to that effect is output to the transmission capacity setting means 104 described later. The vehicle speed determination value V _MAX is a threshold value obtained through experiments and the like, and the self-excited vibration of the rear wheel 34 can be generated when the accelerator operation is performed at the start of the vehicle. _MAX is set to 20 km / h, for example, but may be a variable value based on the accelerator opening Acc or the like.

The self-excited vibration detecting means 102 is a threshold for determining whether or not self-excited vibration of the rear wheel 34 has occurred, and a rotational speed difference determination value V _tMAX obtained through experiments or the like is set in advance. . When the self-excited vibration detection unit 102 obtains a determination result that both the self-excited vibration generation possible conditions are affirmed from the vehicle state determination unit 100, the average of the front wheels 24 is obtained by the following equation (1). A front-rear wheel rotational speed difference V _t , which is a difference between the rotational speed and the average rotational speed of the rear wheel 34, is obtained, and it is determined whether the front-rear wheel rotational speed difference V _t exceeds a rotational speed difference determination value V _tMAX. Whether the determination is affirmative or negative is output to a transmission capacity setting means 104 described later. In addition, since the front-rear wheel rotational speed difference V _{t in the following} formula (1) is an absolute value, the value is always 0 (zero) or more.
V _t = ┃ (V _fr + V _fl −V _rr −V _rl ) / 2┃ (1)

FIG. 3 is a graph showing the relationship between the upper limit voltage e, which is also an instruction voltage of the electronic control coupling 12 during normal running, and the vehicle speed V. As shown in the graph of FIG. 3, the transmission capacity setting means 104 is preset with the relationship between the upper limit voltage e, which is the upper limit value of the command voltage E, and the vehicle speed V. The upper limit voltage e is set from the vehicle speed V according to the graph. When the transmission capacity setting means 104 obtains a determination result from the self-excited vibration detection means 102 that affirms that the front and rear wheel rotation speed difference V _t exceeds the rotation speed difference determination value V _tMAX , Since it is determined that the self-excited vibration of the rear wheel 34 has occurred, the rotational speed on the propeller shaft 28 side which is the input rotational speed of the electronic control coupling 12 and the output of the electronic control coupling 12 are expressed by the following equation (2). An input / output rotational speed difference V _C that is a difference from the rotational speed on the rear wheel operating gear device 30 side, which is the rotational speed, is obtained. The transmission capacity setting means 104 obtains an instruction voltage E corresponding to the transmission capacity of the electronic control coupling 12 by the following equation (3), and the instruction voltage E obtained by the equation (3) is not less than the upper limit voltage e. Is set as the instruction voltage E, and when the instruction voltage E obtained by the equation (3) is less than the upper limit voltage e, the instruction voltage E is set as shown in the equation (3). Set. Therefore, as shown in the graph of FIG. 4, as long as the instruction voltage E does not exceed the upper limit voltage e, a linear function having an input / output rotational speed difference V _C having a preset inclination α ₁ and intercept e / β ₁ is obtained. Become. Here, d in the equation (2) is a reduction ratio of the rear wheel operating gear device 30. Further, the rotational speed NO of the propeller shaft 28 which is the first term on the right side of the formula (2) corresponds to the average rotational speed of the front wheel 24, and “d × (V _rr + V _rl ) which is the second term on the right side of the formula (2). ) / 2 ”corresponds to the average rotational speed of the rear wheel 34, and thus the input / output rotational speed difference V _C corresponds to the front and rear wheel rotational speed difference V _t . In addition, since the input / output rotational speed difference V _{C in the following} formula (2) is an absolute value, the value is always 0 (zero) or more. With the engagement force of the electronic control coupling 12 corresponding to the command voltage E set by the transmission capacity setting means 104 based on the input / output rotational speed difference V _C when the self-excited vibration detection means 102 makes a positive determination result, The following equation is used so that the control coupling 12 is not in a fully coupled state or a disconnected state but is in a semi-engaged (sliding) state, that is, the input / output rotational speed difference V _C has a positive value instead of 0 (zero). Α ₁ and β _{1 in} (3) are arbitrarily set.
V _C = ┃NO−d × (V _rr + V _rl ) / 2┃ (2)
E = α ₁ × V _C + e / β ₁ (3)

Also, when obtaining the determination result to the effect that deny either from the vehicle state determination unit 100 of the self-excited vibration occurs enabling condition, or self-excited vibration detecting means 102 from the front and rear wheel rotational speed difference V _t is the rotational speed difference If a determination result indicating that the determination value V _tMAX is exceeded is obtained, it is determined that the self-excited vibration of the rear wheel 34 has not occurred. Is set as the upper limit voltage e. Then, the transfer capacity setting means 104 outputs the instruction voltage E to the transfer capacity control means 106 described later.

  The transmission capacity control means 106 controls the electronic control by controlling the command value of the current supplied to the electromagnetic solenoid provided in the electronic control coupling 12 based on the instruction voltage E set by the transmission capacity setting means 104. The transmission capacity of the coupling 12 is changed. However, the transmission capacity control means 106 stores the lower limit value of the instruction voltage E obtained by experiments or the like when the self-excited vibration detection means 102 makes a positive determination. When the instruction voltage E is set lower than the lower limit value, the electronic control coupling 12 controls the transmission capacity corresponding to the lower limit value instead of the instruction voltage E set by the transmission capacity setting means 104. Thus, the transmission capacity control means 106 prevents the electronic control coupling 12 from being shut off when suppressing the self-excited vibration of the rear wheel 34.

FIG. 5 is a flowchart for explaining a main part of the control operation of the electronic control unit 36, that is, a control operation for detecting the self-excited vibration of the rear wheel 34 and setting the instruction voltage E of the electronic control coupling 12. First, step SA1 (hereinafter, omitted step) in is determined whether the vehicle speed V is less than the vehicle speed determination value V _MAX is, if the determination is affirmative proceeds to SA2, denial determination If so, go to SA9. In SA2, it is determined whether or not the accelerator operation is performed based on the accelerator opening Acc detected by the accelerator operation amount sensor 52. If the determination is affirmative, the process proceeds to SA3 and the determination is made. If negative, the process proceeds to SA9. SA <b> 1 and SA <b> 2 correspond to a step of determining whether or not the vehicle state in which the self-excited vibration of the rear wheel 34 can occur, and corresponds to the vehicle state determination unit 100.

In SA3, by the formula (1), the front and rear wheel rotational speed difference V _t is calculated, the process proceeds to SA4. In the subsequent SA4, the front and rear wheel rotational speed difference V _t whether exceeds the rotational speed difference determination value V _tMAX is determined. If the determination is affirmative, the process proceeds to SA5, and if the determination is negative, the process proceeds to SA9. SA3 and SA4 correspond to steps for determining whether or not the self-excited vibration of the rear wheel 34 has occurred, and corresponds to the self-excited vibration detecting means 102.

In SA5, the input / output rotational speed difference V _C is calculated by the equation (2), and the process proceeds to SA6. In the subsequent SA6, the instruction voltage E is set by the equation (3), and the process proceeds to SA7. In subsequent SA7, it is determined whether or not the instruction voltage E is less than the upper limit voltage e set based on the vehicle speed V according to the graph of FIG. If the determination is affirmative, the control operation shown in FIG. 5 ends while maintaining the setting of the instruction voltage E set by the expression (3), and if the determination is negative. In SA8, the command voltage E is reset to the upper limit voltage e, and then the control operation shown in FIG. 5 ends.

  SA9 is a step executed when a negative determination result is obtained in any step of SA1, SA2 or SA4, that is, when it is not determined that the self-excited vibration of the rear wheel 34 has occurred, In SA9, the upper limit voltage e is set as the instruction voltage E, and then the control operation shown in FIG. SA5 to SA9 correspond to steps in which the instruction voltage E output to the transmission capacity control means 106 is set, and correspond to the transmission capacity setting means 104.

The electronic control device 36 of this embodiment has the following effects (1) to (4). (1) When the front-rear wheel rotational speed difference V _t exceeds the rotational speed difference determination value V _tMAX and the self-excited vibration detection means 102 determines that the self-excited vibration of the rear wheel 34 has occurred, as shown in FIG. , transmission capacity control as indicated voltage E output rotational speed difference V _C increases and is set so as to increase toward the voltage lower than the upper limit voltage e to the upper limit voltage e is executed. Further, with the engagement force of the electronic control coupling 12 based on the instruction voltage E at that time, the electronic control coupling 12 is in a half-engaged (sliding) state, that is, the input / output rotational speed difference V _C is not 0 (zero) but positive. It will be in the state which has the value of. Accordingly, when the self-excited vibration is generated, the instruction voltage E lower than the upper limit voltage e is once set, so that excessive driving force transmitted to the rear wheel 34 is suppressed and the self-excited vibration is suppressed. . Further, when the self-excited vibration is generated, the electronic control coupling 12 maintains the half-engaged state, and the input / output rotational speed difference V _C corresponding to the front and rear wheel rotational speed difference V _t increases based on the indicated voltage. since enhance the engaging force, be derived work electronically controlled coupling 12 as damper larger the front and rear wheel rotation speed difference V _t suppressing rotational resistance thereof is increased, the self-excited vibration in the early convergence it can. FIG. 6 is a diagram showing CAE results for comparing and explaining torque fluctuations of the rear wheels 34 when the transmission capacity control is executed and when it is not executed. From FIG. 6, it can be confirmed that the self-excited vibration of the rear wheel 34 converges earlier when the transmission capacity control is executed.

(2) Since the transmission capacity control is executed when the vehicle state determination means 100 determines that the vehicle speed V is less than the vehicle speed determination value V _MAX , the self-excited vibration occurs. By executing the transmission capacity control, the self-excited vibration is suppressed, and when the self-excited vibration does not occur, a sufficient driving force can be transmitted to the rear wheel 34 without reducing the transmission capacity.

(3) Since the vehicle speed determination value V _MAX can be a variable value based on the accelerator opening Acc or the like, if it is determined from the accelerator opening Acc or the like that an early vehicle start is required, the vehicle speed determination By changing the value V _MAX to a low value, it is possible to suppress the execution of the transmission capacity control that temporarily decreases the transmission capacity, and to start the four-wheel drive vehicle 10 at an early stage.

  (4) Once the electronic control coupling 12 is in the cut-off state, the response of the electronic control coupling 12 to the request to increase the transmission capacity is reduced due to the gap of the engagement element, but self-excited vibration detection means When the determination of 102 is affirmative and the transmission capacity control is executed, the transmission capacity control means 106 controls the electronic control coupling so that the transmission capacity of the electronic control coupling 12 does not become less than a predetermined lower limit value. 12 is not in the shut-off state, the responsiveness of the electronically controlled coupling 12 when increasing the transmission capacity can be maintained high, and the driving force is transmitted to the rear wheels 34 so that the four-wheel drive vehicle 10 Can be started.

  Next, another embodiment of the present invention will be described. In the following description, parts common to the embodiments are denoted by the same reference numerals and description thereof is omitted.

  The second embodiment is obtained by replacing the electronic control device 36 of FIG. 1 with an electronic control device 88, and FIG. 7 shows a main part of the control function of the electronic control coupling 12 by the electronic control device 88 according to the second embodiment. It is a functional block diagram explaining these. FIG. 7 shows another embodiment corresponding to FIG. 2. The vehicle state determination means 100, the self-excited vibration detection means 102 and the transmission capacity control means 106 are common, but other means are different. Hereinafter, the difference will be mainly described.

When the self-excited vibration of the rear wheel 34 occurs, the front-rear wheel rotational speed difference V _t pulsates, but the self-excited vibration occurrence recording means 110 indicates that the front-rear wheel rotational speed difference V _t is the rotational speed difference determination value V. _{When the} self-excited vibration detection unit 102 obtains a determination result indicating that _tMAX is exceeded, the current time t is set to the self-excitation frequency so that the transfer capacity setting unit 112 described later calculates the number of pulsations. The excitation vibration occurrence time t ₁ is recorded and output to the transmission capacity setting means 112. In addition, since the expression applied by the transfer capacity setting unit 112 (described later) for calculating the instruction voltage E is different between the first period and the second and subsequent periods of the self-excited vibration, the self-excited vibration occurrence recording unit 110. Also outputs to the transmission capacity setting means 112 information on whether the self-excited vibration is in the first period or after the second period. When the vehicle state determination unit 100 denies one of the two conditions for generating self-excited vibration, the self-excited vibration occurrence recording unit 110 returns the generation time t ₁ to an initial value, that is, zero.

The transmission capacity setting means 112 sets the upper limit voltage e from the vehicle speed V according to the graph of FIG. 3 and sets the instruction voltage E and outputs the instruction voltage E to the transmission capacity control means 106. Although common to the transfer capacity setting means 104 of the first embodiment, the method of calculating the instruction voltage E is different from that of the transfer capacity setting means 104. When the self-excited vibration occurrence recording unit 110 obtains that the self-excited vibration is in the first period from the self-excited vibration occurrence recording unit 110, the transfer capacity setting unit 112 obtains the instruction voltage E by the following equation (4), When it is obtained from the vibration occurrence recording means 110 that the self-excited vibration is after the second period, the instruction voltage E is obtained by the following equation (5), and the equation (4) or (5) Is set as the instruction voltage E, and the instruction voltage E obtained by the equation (4) or (5) is less than the upper limit voltage e. In this case, the instruction voltage E is set as determined by the equation (4) or the equation (5). Accordingly, dt in the equation (5) is a period of the self-excited vibration obtained and set in advance by experiment, and “(t−t ₁ ) / dt” in the equation (5) is “ 8, the relationship between the input / output rotational speed difference V _C and the command voltage E is as shown in the graph of FIG. 8. As long as the command voltage E does not exceed the upper limit voltage e, α It becomes a function of the input / output rotational speed difference V _C whose intercept is e / β ₂ , starting from ₂ and having a slope that increases as the number of pulsations increases. The engagement force of the electronically controlled coupling 12 corresponding to the command voltage E set by the transmission capacity setting unit 112 based on the input / output rotational speed difference V _C when the self-excited vibration detection unit 102 makes a positive determination result. Α ₂ , β _2, and k are arbitrarily set so that the electronic control coupling 12 is in a semi-engaged (sliding) state instead of a fully coupled state or a disconnected state. Further, “(t−t ₁ ) / dt” corresponding to “the number of pulsations minus one” of the self-excited vibration can take a real value instead of an integer value.
E = α ₂ × V _C + e / β ₂ (4)
E = (1 + k × (t−t ₁ ) / dt) × α ₂ × V _C + e / β ₂ (5)

Also, when obtaining the determination result to the effect that deny either from the vehicle state determination unit 100 of the self-excited vibration occurs enabling condition, or self-excited vibration detecting means 102 from the front and rear wheel rotational speed difference V _t is the rotational speed difference When a determination result indicating that the determination value V _tMAX is exceeded is obtained, the transfer capacity setting unit 112 sets the instruction voltage E to the upper limit voltage e. Then, the transmission capacity setting means 112 outputs the instruction voltage E to the transmission capacity control means 106.

  FIG. 9 is a flowchart for explaining a main part of the control operation of the electronic control unit 88, that is, a control operation for detecting the self-excited vibration of the rear wheel 34 and setting the instruction voltage E of the electronic control coupling 12. FIG. 9 shows another embodiment corresponding to FIG. 5. SB1 to SB5, SB9 to SB11, and SB15 in FIG. 9 are steps corresponding to SA1 to SA5, SA6 to SA8, and SA9 in FIG. It is. Hereinafter, differences from FIG. 5 in FIG. 9 will be mainly described.

If the determination in SB4 is affirmative, the input / output rotational speed difference V _C is calculated in SB5, and then the process proceeds to SB6. In SB6, the occurrence time t ₁ of the self-excited vibration is its initial value. It is determined whether or not the value exceeds. And moves to SB12 if the determination is affirmative, then control goes to SB7 in which case the determination is negative, is set as a generation time t ₁ the current time t is self-excited vibration in SB7, to SB9 Move. Therefore, the fact that the determination of SB4 is positive is that the self-excited vibration of the rear wheels 34 occurs, the occurrence time t ₁ of the self-excited vibration of a positive value such after SB7 is executed, When the determination of SB6 is negative, it is the first period of the self-excited vibration, and when the determination is affirmative, it can be said that it is after the second period.

If SB1 or any determination of SB2 is negative, in SB8, the occurrence time t ₁ is returned to the initial value or 0, it goes to SB15. Note that SB6 to SB8 correspond to the self-excited vibration occurrence recording unit 110.

  In SB12, the instruction voltage E is set by the equation (5), and the process proceeds to SB13. In subsequent SB13, it is determined whether or not the command voltage E is less than the upper limit voltage e set based on the vehicle speed V according to the graph of FIG. If the determination is affirmative, the control operation shown in FIG. 9 ends while maintaining the setting of the instruction voltage E set by the equation (5), and if the determination is negative. In SB14, the command voltage E is reset to the upper limit voltage e, and then the control operation shown in FIG. Note that SB5 and SB9 to SB15 correspond to steps in which the instruction voltage E output to the transmission capacity control means 106 is set, and correspond to the transmission capacity setting means 112.

According to the present embodiment, as shown in FIG. 8, as the number of pulsations of the self-excited vibration of the rear wheel 34 increases, the coefficient “(1 + k × (t−t) of the input / output rotational speed difference V _C in Expression (5)”. ₁ ) / dt) × α ₂ ”, the increase rate of the instruction voltage E with respect to the increase amount of the input / output rotational speed difference V _C becomes large. Therefore, when the self-excited vibration occurs, the input / output rotational speed difference V _C increases. The change rate that strengthens the engagement force based on the command voltage E increases as the number of pulsations increases, making the pulsation of the input / output rotational speed difference V _C converge faster and converge the self-excited vibrations earlier. Can lead to. The electronic control device 88 of the present embodiment is obtained by adding the function of changing the increase rate to the electronic control device 36 of the first embodiment, and therefore the effects (1) to (4) of the first embodiment. ).

  The third embodiment is obtained by replacing the electronic control device 36 of FIG. 1 with an electronic control device 90, and FIG. 10 shows a main part of the control function of the electronic control coupling 12 by the electronic control device 90 according to the third embodiment. It is a functional block diagram explaining these. FIG. 10 shows another embodiment corresponding to FIG. 2. The vehicle state determination means 100, the self-excited vibration detection means 102 and the transmission capacity control means 106 are common, but other means are different. Hereinafter, the difference will be mainly described.

When the transmission capacity change region changing unit 116 obtains a determination result from the self-excited vibration detection unit 102 that affirms that the front and rear wheel rotation speed difference V _t exceeds the rotation speed difference determination value V _tMAX , The intercept change amount L having an initial value of 0 used in the later-described equation (6) is output to the later-described transmission capacity setting means 118. Further, the intercept change interval L ₁ is set in advance in the transfer capacity changing region changing means 116, and the instruction voltage E obtained by the transfer capacity setting means 118 described later using the equation (6) is less than the upper limit voltage e. If the determination is made to deny, the transmission capacity change region changing means 116 adds the intercept change amount L by the intercept change interval L ₁ and resets it. Accordingly, in the first output to the transmission capacity setting means 118 described later, the intercept change amount L is output as 0, and the intercept change amount added by the intercept change interval L ₁ each time the determination to deny is made. L is output. When the vehicle state determination unit 100 denies one of the two conditions for generating self-excited vibration, the transmission capacity change region change unit 116 returns the intercept change amount L to the initial value, that is, zero.

The transmission capacity setting means 118 sets the upper limit voltage e from the vehicle speed V according to the graph of FIG. 3 and sets the instruction voltage E and outputs the instruction voltage E to the transmission capacity control means 106. Although common to the transfer capacity setting means 104 of the first embodiment, the method of calculating the instruction voltage E is different from that of the transfer capacity setting means 104. The transmission capacity setting means 118 acquires the intercept change amount L from the transmission capacity change region changing means 116, obtains the instruction voltage E by the following equation (6), and the instruction voltage E obtained by the equation (6) is the upper limit voltage. If it is equal to or greater than e, the fact is output to the transmission capacity change region changing means 116, and the upper limit voltage e is set as the instruction voltage E. On the other hand, the instruction voltage E obtained by the equation (6) is less than the upper limit voltage e. In the case of, the instruction voltage E is set as shown in the equation (6). Therefore, the relationship between the input / output rotational speed difference V _C and the instruction voltage E is as shown in the graph of FIG. 11, and every time the instruction voltage E obtained by the equation (6) exceeds the upper limit voltage e, the instruction voltage E There area in FIG. 11, which varies as a function of the input and output rotational speed difference V _C is, so that the shift in the positive direction of the input and output rotational speed difference V _C. The graph of FIG. 11 is an example, and corresponds to the instruction voltage E set by the transfer capacity setting unit 118 based on the input / output rotational speed difference V _C when the self-excited vibration detection unit 102 makes a positive determination result. Α ₃ , β _3, and L ₁ are arbitrarily set so that the electronic control coupling 12 is in a semi-engaged (sliding) state rather than a fully coupled state or a disconnected state, with the engagement force of the electronic control coupling 12. Has been.
E = α ₃ × V _C + e / β ₃ −L (6)

Also, when obtaining the determination result to the effect that deny either from the vehicle state determination unit 100 of the self-excited vibration occurs enabling condition, or self-excited vibration detecting means 102 from the front and rear wheel rotational speed difference V _t is the rotational speed difference When a determination result indicating that the determination value V _tMAX is exceeded is obtained, the transfer capacity setting means 118 sets the instruction voltage E to the upper limit voltage e. Then, the transmission capacity setting means 118 outputs the instruction voltage E to the transmission capacity control means 106.

  FIG. 12 is a flowchart for explaining a main part of the control operation of the electronic control unit 90, that is, a control operation for detecting the self-excited vibration of the rear wheel 34 and setting the instruction voltage E of the electronic control coupling 12. FIG. 12 shows another embodiment corresponding to FIG. 5. SC1 to SC5, SC7 to SC8, and SC11 in FIG. 12 are steps corresponding to SA1 to SA5, SA7 to SA8, and SA9 in FIG. It is. Hereinafter, differences from FIG. 5 in FIG. 12 will be mainly described.

If the determination in SC4 is affirmative, the input / output rotational speed difference V _C is calculated in SC5, and then the process proceeds to SC6. In SC6, the instruction voltage E is set by the above equation (6), and the process proceeds to SC7. . SC5 to SC8 and SC11 correspond to steps in which the instruction voltage E output to the transmission capacity control means 106 is set, and correspond to the transmission capacity setting means 118.

When the result of the determination SC7 is negative is transferred to SC9 through SC8, in SC9, as in the following equation (7), sections change amount L is reconfigured by adding only sections change interval L _1, then, The control operation shown in FIG. 12 ends.
L = L + L ₁ (7)

  If the determination of either SC1 or SC2 is negative, the intercept change amount L is returned to the initial value, that is, 0 in SC10, and the process proceeds to SC11. SC9 to SC10 correspond to the transmission capacity change region changing unit 116.

Wherein upon occurrence of self-excited vibration is 11, where it is necessary to command voltage E is so output rotational speed difference V _C falls within the area that varies as a function of the input and output rotational speed difference V _C, present According to the example, each time the command voltage E obtained by the equation (6) becomes equal to or higher than the upper limit voltage e, the region shifts in the positive direction of the input / output rotational speed difference V _C. The input / output rotational speed difference V _C when the occurrence of the occurrence of the above can be adjusted so as to fall within the above-mentioned region. Compared with the case where the above-mentioned region does not shift, this embodiment has a wider input / output rotational speed difference V _C. Can respond to changes. Since the electronic control unit 90 of the present embodiment is provided with a function for changing the above-described area with respect to the electronic control unit 36 of the first embodiment, the effects (1) to (4) of the first embodiment. Also have.

In this embodiment, the coefficient α ₃ of the input / output rotational speed difference V _C in equation (6) is constant, but as shown in FIG. 13, the coefficient α ₃ is increased every time the determination is denied in SC7. You can also. In this way, the effect of the second embodiment in which the coefficient of the input / output rotational speed difference V _C in equation (4) or equation (5) is increased as the number of pulsations of the self-excited vibration increases. Can do.

  The fourth embodiment is obtained by replacing the electronic control device 36 of FIG. 1 with an electronic control device 92, and FIG. 14 shows the main part of the control function of the electronic control coupling 12 by the electronic control device 92 according to the fourth embodiment. It is a functional block diagram explaining these. FIG. 14 shows another embodiment corresponding to FIG. 2. The vehicle state determination means 100, the self-excited vibration detection means 102 and the transmission capacity control means 106 are common, but other means are different. Hereinafter, the difference will be mainly described.

If the driving force estimation unit 124 obtains a determination result from the self-excited vibration detection unit 102 that affirms that the front-rear wheel rotational speed difference V _t exceeds the rotational speed difference determination value V _tMAX , And the intercept b of the following equation (8) is calculated using the following equation (9) obtained by modifying the equation (8) based on the estimation. To the transmission capacity setting means 126. Specifically, it was obtained by an experiment or the like in advance, the relationship such as the opening theta _TH and the engine rotational speed N _E of the electronic throttle valve and the engine drive torque is set to the driving force estimation unit 124, the self-excited vibration upon obtaining a positive determination result of the detecting means 102, and the like opening theta _TH and the engine rotational speed N _E of the electronic throttle valve at that time, the driving force estimating means an engine driving torque 124 estimates. Then, the shift lever position _PSH at that time is acquired, the reduction ratio from the input shaft 38 to the propeller shaft 28 is calculated, and the input torque of the electronic control coupling 12 is calculated based on the reduction ratio and the engine drive torque. . When the input torque is input to the electronically controlled coupling 12, the transmission capacity is as high as possible so that the electronically controlled coupling 12 is not fully coupled or disconnected but is semi-engaged (slid). A corresponding command voltage E is obtained, and the command voltage E and the input / output rotational speed difference V _C at the time of estimation of the engine drive torque are substituted into equation (9). Output to.
E = α ₄ × V _C + b (8)
b = E−α ₄ × V _C (9)

The transmission capacity setting means 126 sets the upper limit voltage e from the vehicle speed V according to the graph of FIG. 3 and sets the instruction voltage E and outputs the instruction voltage E to the transmission capacity control means 106. Although common to the transfer capacity setting means 104 of the first embodiment, the method of calculating the instruction voltage E is different from that of the transfer capacity setting means 104. The transmission capacity setting unit 126 obtains the intercept b from the engine torque estimation unit 124, obtains the instruction voltage E by the above equation (8), and the instruction voltage E obtained by the equation (8) is equal to or higher than the upper limit voltage e. The upper limit voltage e is set as the instruction voltage E, and when the instruction voltage E obtained by the equation (8) is less than the upper limit voltage e, the instruction voltage E is set as in the equation (8). Therefore, the relationship between the input / output rotational speed difference V _C and the command voltage E is as shown in the graph of FIG. 15, and every time the self-excited vibration detection means 102 makes a positive determination, the intercept used in the equation (8). The region in FIG. 15 where b is changed and the command voltage E changes as a function of the input / output rotational speed difference V _C will be shifted. Note that the slope α ₄ in the equation (8) is a constant set arbitrarily as in the case of α ₁ in the equation (3) in the first embodiment.

Also, when obtaining the determination result to the effect that deny either from the vehicle state determination unit 100 of the self-excited vibration occurs enabling condition, or self-excited vibration detecting means 102 from the front and rear wheel rotational speed difference V _t is the rotational speed difference When a determination result indicating that the determination value V _tMAX is exceeded is obtained, the transfer capacity setting unit 126 sets the instruction voltage E to the upper limit voltage e. Then, the transmission capacity setting unit 126 outputs the instruction voltage E to the transmission capacity control unit 106.

  FIG. 16 is a flowchart for explaining a main part of the control operation of the electronic control unit 92, that is, a control operation for detecting the self-excited vibration of the rear wheel 34 and setting the instruction voltage E of the electronic control coupling 12. FIG. 16 shows another embodiment corresponding to FIG. 5. SD1 to SD4, SD6, SD8 to SD9, and SD10 in FIG. 16 are SA1 to SA4, SA5, SA7 to SA8, and SA9 in FIG. This is a step corresponding to. Hereinafter, differences from FIG. 5 in FIG. 16 will be mainly described.

If the determination of SD4 is affirmative, the engine driving torque at that time is estimated in SD5 corresponding to the driving force estimating means 124, and the intercept b used in the equation (8) is set based on the estimation. The Specifically, based on such angle theta _TH and the engine rotational speed N _E of the electronic throttle valve, which is acquired in advance by experiments and the relationship between the engine drive torque, when a positive determination is made at SD4 The engine drive torque is estimated. Then, the shift lever position _PSH at that time is acquired, the reduction ratio from the input shaft 38 to the propeller shaft 28 is calculated, and the input torque of the electronic control coupling 12 is calculated based on the reduction ratio and the engine drive torque. . When the input torque is input to the electronically controlled coupling 12, the transmission capacity is as high as possible so that the electronically controlled coupling 12 is not fully coupled or disconnected but is semi-engaged (slid). It obtains the corresponding instruction voltage E, substituting its command voltage E and output rotational speed difference V _C at the time of estimation of the engine drive torque to the formula (9), whereby the intercept b is set. Thereafter, the process proceeds to SD6.

After the input / output rotational speed difference V _C is calculated in SD6, the process proceeds to SD7. In SD7, the instruction voltage E is set by the above equation (8), and the process proceeds to SD8. SD6 to SD10 correspond to steps in which the instruction voltage E output to the transfer capacity control means 106 is set, and correspond to the transfer capacity setting means 126.

  According to this embodiment, the driving force estimating means 124 estimates the engine driving torque when the positive determination result of the self-excited vibration detecting means 102 is obtained, and the input torque of the electronic control coupling 12 at that time is calculated. Then, the intercept b of the equation (8) is set so that the electronic control coupling 12 is in the half-engaged state and the command voltage E is set as high as possible at the input torque. The transmission capacity of the driving force based on the four-wheel drive vehicle 10 can be promptly started without being reduced more than necessary. Since the electronic control device 92 of the present embodiment is obtained by adding a driving force estimating means 124 for estimating the engine drive torque to the electronic control device 36 of the first embodiment, the effects of the first embodiment ( It also has 1) to (4).

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention is implemented in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

  For example, the four-wheel drive vehicle 10 of the first to fourth embodiments is based on an FF vehicle, but this is an example. In the two-wheel drive mode, RR (rear engine / rear drive) that drives the rear wheels 34 is used. It may be a four-wheel drive vehicle based on other types. When the four-wheel drive vehicle 10 is based on the RR type, the wheel that can generate the self-excited vibration is the front wheel 24 that is a wheel far from the engine 14.

Further, according to the equations (3), (4), (5), (6), and (8), the command voltage E is calculated as a linear function of the input / output rotational speed difference V _C. This is merely an example, and it is sufficient that the command voltage E increases as the input / output rotational speed difference V _C increases. For example, the command voltage E is calculated as a quadratic function of the input / output rotational speed difference V _C. Also good.

Further, according to the equations (3), (4), (5), (6), and (8), the command voltage E is calculated as a function of the input / output rotational speed difference V _C. it may be calculated as a function of the front and rear wheel rotation speed difference V _t associated with the input and output rotational speed difference V _C.

  The electronic control coupling 12 is a driving force transmission device that changes its transmission capacity by adjusting the engagement force of the engagement element incorporated in the electronic control coupling 12, but other structures such as a magnetic powder electromagnetic clutch can be used. The driving force transmission device may be used to change the transmission capacity.

  In addition, the first to fourth embodiments can be implemented in combination with each other, for example, by setting priorities.

It is a figure for demonstrating the principal part of the control system which controls the four-wheel drive vehicle to which this invention was applied, and an electronic control coupling. It is a functional block diagram for demonstrating the principal part of the control function of the electronic control coupling by the electronic control apparatus of FIG. 2 is a graph showing an example of a relationship between an upper limit voltage e and a vehicle speed V of electronic control coupling in FIG. 1. When the electronic control device of FIG. 2 detects the self-excited vibration of the rear wheel, the input / output is the difference between the rotational speed of the electronically controlled coupling on the propeller shaft 28 side and the rotational speed of the rear wheel operating gear device 30 side. 4 is a graph for explaining a relationship between a rotational speed difference V _C and an instruction voltage E. 3 is a flowchart for explaining a main part of a control operation of the electronic control device of FIG. 2, that is, a control operation for detecting a self-excited vibration of a rear wheel and setting an instruction voltage E for electronic control coupling. It is a figure for demonstrating the effect at the time of performing the control action of FIG. FIG. 6 is a functional block diagram for explaining a main part of a control function of electronic control coupling by the electronic control device of FIG. 1 in the second embodiment which is another embodiment of the present invention, corresponding to FIG. It is. 7 is a graph for explaining the relationship between the input / output rotational speed difference V _C and the command voltage E when the electronic control unit of FIG. 7 detects the self-excited vibration of the rear wheel, and is a graph corresponding to FIG. is there. 7 is a flowchart for explaining a main part of the control operation of the electronic control device of FIG. 7, that is, a control operation for detecting the self-excited vibration of the rear wheel and setting the instruction voltage E for electronic control coupling, corresponding to FIG. It is a flowchart to do. FIG. 6 is a functional block diagram for explaining a main part of a control function of electronic control coupling by the electronic control device of FIG. 1 in the third embodiment which is another embodiment of the present invention, corresponding to FIG. It is. FIG. 11 is a graph for explaining the relationship between the input / output rotational speed difference V _C and the command voltage E when the electronic control device of FIG. 10 detects the self-excited vibration of the rear wheels; is there. 10 is a flowchart for explaining a main part of the control operation of the electronic control device of FIG. 10, that is, a control operation for detecting a self-excited vibration of the rear wheel and setting an instruction voltage E for electronic control coupling, corresponding to FIG. It is a flowchart to do. 10 is a graph for explaining the relationship between the input / output rotational speed difference V _C and the command voltage E when the inclination α ₃ is changed when the electronic control unit of FIG. 10 detects the self-excited vibration of the rear wheel. FIG. 5 is a graph corresponding to FIG. FIG. 6 is a functional block diagram for explaining the main part of the control function of the electronic control coupling by the electronic control device of FIG. 1 in the fourth embodiment which is another embodiment of the present invention, corresponding to FIG. It is. FIG. 15 is a graph for explaining the relationship between the input / output rotational speed difference V _C and the command voltage E when the electronic control device of FIG. 14 detects the self-excited vibration of the rear wheels, and is a graph corresponding to FIG. is there. 14 is a flowchart for explaining a main part of the control operation of the electronic control device of FIG. 14, that is, a control operation for detecting a self-excited vibration of the rear wheel and setting an instruction voltage E for electronic control coupling, corresponding to FIG. It is a flowchart to do.

Explanation of symbols

10: Four-wheel drive vehicle 12: Electronically controlled coupling (drive force transmission device)
14: Engine (internal combustion engine) 24l, 24r: Front wheels 34l, 34r: Rear wheels 36, 88, 90, 92: Electronic control device (driving force control device)
106: Transmission capacity control means 124: Driving force estimation means

Claims (6)

A driving force output from the internal combustion engine is transmitted to either the front wheel or the rear wheel, and to the other wheel of the front wheel or the rear wheel via a driving force transmission device having a variable transmission capacity. A driving force control device for a four-wheel drive vehicle comprising a second transmission path to be transmitted,
When the front and rear wheel rotational speed difference, which is the absolute value of the difference between the front wheel rotational speed and the rear wheel rotational speed, is greater than or equal to a predetermined rotational speed difference determination value, the transmission capacity of the driving force transmission device is reduced. After that, the transmission capacity is increased as the input / output rotational speed difference, which is a value related to the absolute value of the difference between the input rotational speed of the driving force transmission device and the output rotational speed of the driving force transmission device, increases. A driving force control device for a four-wheel drive vehicle, comprising transmission capacity control means for executing transmission capacity control. The drive of a four-wheel drive vehicle according to claim 1, wherein the transmission capacity control means executes the transmission capacity control when a vehicle speed of the four-wheel drive vehicle is equal to or less than a predetermined vehicle speed determination value. Force control device. The transmission capacity control means executes the transmission capacity control so that the rate of increase of the transmission capacity with respect to the increase amount of the input / output rotational speed difference increases as the number of pulsations of the front and rear wheel rotational speed difference increases. The driving force control apparatus for a four-wheel drive vehicle according to claim 1 or 2, characterized in that A driving force estimating means for estimating a driving force output from the internal combustion engine;
The driving force control device for a four-wheel drive vehicle according to claim 1 or 2, wherein a transmission capacity of the driving force transmission device is determined based on the estimated driving force.   The driving force control apparatus for a four-wheel drive vehicle according to claim 2, wherein the vehicle speed determination value is variable. The transmission capacity control means, when executing the transmission capacity control of the driving force transmission device, does not place the driving force transmission device in a shut-off state in which the driving force is not transmitted to the other wheel. The driving force control apparatus for a four-wheel drive vehicle according to any one of claims 1 to 5.

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