JP2004352129A - Driving power distribution controlling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving power distribution controlling device capable of applying torque to a follower wheel till an upper limit, and improving traveling performance without controlling delay. <P>SOLUTION: When slip occurs, till engaging force of a torque distributing clutch is improved to an upper limit value (S12:No), the driving power distribution controlling device corresponds by improving the engaging force (S18). On the other hand, while the engaging force is improved to the upper limit value (S12:Yes), when a rotation difference between a front wheel and a rear wheel exceeds a specified value (S14:Yes), a request signal for lowering engine torque is sent to an engine controlling device (S22). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a driving force distribution control device for a four-wheel drive vehicle, and in particular, transmits driving force generated by an engine and a motor directly to a front wheel or a rear wheel, and transmits the driving force to the other wheel via a torque distribution clutch. The present invention relates to a driving force distribution control device that transmits a driving force to a front wheel and a rear wheel by transmitting the driving force to a front wheel and a rear wheel by transmitting the driving force to a front wheel and a rear wheel according to a traveling state of a vehicle and controlling an engagement force of a torque distribution clutch.
[0002]
[Prior art]
At present, a four-wheel drive vehicle always has a four-wheel drive system in which four wheels are constantly driven, and a front wheel or one of the rear wheels (main driving wheel) is always driven, and the other wheel (only when a slip occurs) is performed. Non-constant four-wheel drive system in which the power is transmitted to the driven wheels). Generally, the always-on four-wheel drive system is assumed to be used under heavy loads such as rough roads and ultra-high speed running, whereas the non-always-on four-wheel drive system is used on snowy roads in winter. Temporary four-wheel drive under light load such as to suppress slip is assumed, and two-wheel drive is usually assumed.
[0003]
Such a non-constant four-wheel drive system is based on a front-wheel drive vehicle, and a torque distribution clutch, a rear-wheel defensive, and a rear-wheel drive shaft are provided so that a driving force can be transmitted to a rear wheel when a slip occurs. And so on. Alternatively, based on a rear wheel drive vehicle, a torque distribution clutch, a front wheel defensive, a front wheel drive shaft, and the like are added so that the driving force can be transmitted to the front wheels. For example, when a front-wheel drive vehicle is used as a base, slip on the front wheels is detected based on the rotation difference between the front wheels and the rear wheels, and when a slip occurs, the engagement force of the torque distribution clutch is variably controlled. Slip is suppressed by starting torque distribution to the rear wheel side. Patent Document 1 discloses a driving force distribution control device using the torque distribution clutch.
[0004]
As described above, the driving force distribution control device changes the torque distribution between the front wheels and the rear wheels based on the rotation difference between the front wheels and the rear wheels. On the other hand, the engine control device detects the slip based on the rotation difference between the front wheel and the rear wheel separately from the driving force distribution control device, and performs control to reduce the engine output when the slip increases. Such an engine control is disclosed in Patent Document 2. Further, Patent Document 3 discloses a brake control that applies a brake to a slipping wheel to reduce slip, separately from the driving force distribution control device and the engine control device.
[0005]
In the above-described non-constant four-wheel drive four-wheel drive vehicle, when the maximum output of the engine is generated, it is not assumed that the vehicle is driven by four wheels. By limiting the applied torque, a reduction in weight and a resulting reduction in fuel consumption are realized. That is, in the above-described method of variably controlling the engagement force of the torque distribution clutch, the upper limit torque value that can be applied to the driven wheel is set in advance, and the torque is applied to the driven wheel within the range of the upper limit torque value, thereby reducing the weight. In this way, no obstacles occur in the defender and shaft on the driven wheel side.
[Patent Document 1]
JP-A-6-16731
[Patent Document 2]
JP-A-7-149169
[Patent Document 3]
JP-A-9-226407
[0006]
[Problems to be solved by the invention]
As described above, the slip is prevented by the torque distribution to the driven wheels based on the detection of the front and rear wheel rotation difference in the driving force distribution control device, and the slip is prevented by reducing the engine output based on the detection of the front and rear wheel rotation difference by the engine control device. Was done separately. For this reason, even in a state where the slip can be reduced by increasing the torque distribution to the driven wheels, the engine control device may reduce the engine output based on the detection of the front-rear wheel rotation difference. For example, on a snowy uphill road, when the driver steps on the throttle pedal and slips on the front wheels, the engine control works even in a state where the running can be stabilized by increasing the torque distribution to the rear wheels, and the driver's will On the contrary, a phenomenon such as a decrease in engine output has occurred.
[0007]
In order to prevent the above phenomenon, a method in which the prevention of slip by the engine output reduction by the engine control device is operated later than the prevention of slip by torque distribution by the driving force distribution control device may be considered. Specifically, the difference between the front and rear wheels at which the engine control device starts reducing the engine output is made larger than the difference between the front and rear wheels at which the driving force distribution control device performs the torque distribution. However, in this method, the engine output starts to be reduced after the slip increases, and the control delay cannot be denied. In particular, when the torque value that can be applied to the driven wheels is limited as described above, and the driver has further applied the accelerator pedal while the upper limit torque value has already been applied to the driven wheels by the driving force distribution control device. When the vehicle is depressed, the torque distribution to the driven wheels cannot be increased, so only the torque to the main wheels is increased. Only the torque is actually increased, and control for suppressing the engine torque is started after the slip amount further increases.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a driving force distribution control device capable of applying torque to an upper limit of a driven wheel to increase running performance without control delay. Is to do.
[0009]
Means for Solving the Problems and Actions and Effects of the Invention
In order to achieve the above object, the invention according to claim 1 directly transmits a driving force generated by an engine or a motor to a front wheel or a rear wheel, and transmits the driving force to the other wheel via a torque distribution clutch. A driving force distribution control device for a four-wheel drive vehicle that transmits and controls the engagement force of the torque distribution clutch in a range up to a preset upper limit value in accordance with a running state of the vehicle;
In a state where the engagement force of the torque distribution clutch is increased to the upper limit, a slip suppression request signal is transmitted when a rotation difference between a front wheel and a rear wheel exceeds a predetermined value. And
[0010]
In the driving force distribution control device according to the first aspect, when the slip occurs, the engagement force is increased without transmitting the slip suppression request signal until the engagement force of the torque distribution clutch is increased to the upper limit value. To respond. For this reason, the trunk performance can be ensured, and the running performance can be enhanced. On the other hand, when the rotational difference between the front wheel and the rear wheel exceeds a predetermined value in a state where the engagement force of the torque distribution clutch is increased to the upper limit value, a request signal for slip suppression is transmitted. This makes it possible to secure the traction performance without delay while applying torque up to the upper limit at which no obstacle occurs in the light-weight driven wheel-side defensive shaft.
[0011]
According to the second aspect of the present invention, the driving force generated by the engine or the motor is directly transmitted to the front wheel or the rear wheel, and the driving force is transmitted to the other wheel via the torque distribution clutch, so that the driving state of the vehicle is improved. A driving force distribution control device for a four-wheel drive vehicle that controls the engagement force of the torque distribution clutch in a range up to a preset upper limit value in response to
In a state where the engagement force of the torque distribution clutch is increased to the upper limit value, when the speed of increase of the rotation difference between the front wheel and the rear wheel exceeds a predetermined value, transmitting a slip suppression request signal. Technical features.
[0012]
In the driving force distribution control device according to the second aspect, when the slip occurs, the engagement force is increased without transmitting the slip suppression request signal until the engagement force of the torque distribution clutch is increased to the upper limit value. To respond. For this reason, the trunk performance can be ensured, and the running performance can be enhanced. On the other hand, when the increasing speed of the rotational difference between the front wheels and the rear wheels exceeds a predetermined value in a state where the engagement force of the torque distribution clutch is increased to the upper limit value, a slip suppression request signal is transmitted. As a result, it is possible to apply torque up to the upper limit at which no obstacle occurs in the light-weight driven wheel-side defensive shaft and shaft, thereby ensuring the traction performance without control delay.
[0013]
According to the third aspect, when a slip occurs, the engagement force is increased without transmitting a request signal to reduce the engine torque to the engine control device until the engagement force of the torque distribution clutch is increased to the upper limit value. Corresponding. For this reason, the trunk performance can be ensured, and the running performance can be enhanced. On the other hand, when the rotation difference between the front wheel and the rear wheel exceeds a predetermined value while the engagement force of the torque distribution clutch is increased to the upper limit value, or when the speed of increase of the rotation difference between the front wheel and the rear wheel becomes a predetermined value. When the value exceeds the value, a request signal to reduce the engine torque is transmitted to the engine control device. This reduces the weight of the driven wheel side defensive and torque up to the upper limit where there is no failure in the shaft, ensuring the traction performance and preventing the increase in slip due to the increase in engine power before it actually occurs It becomes possible to do.
[0014]
According to a fourth aspect, when a slip occurs, the engagement force is increased without transmitting a signal requesting a brake operation to the brake control device until the engagement force of the torque distribution clutch is increased to an upper limit value. Corresponding. For this reason, the trunk performance can be ensured, and the running performance can be enhanced. On the other hand, when the rotation difference between the front wheel and the rear wheel exceeds a predetermined value while the engagement force of the torque distribution clutch is increased to the upper limit value, or when the speed of increase of the rotation difference between the front wheel and the rear wheel becomes a predetermined value. Is transmitted, a request signal for requesting a brake operation to the brake control device is transmitted. This reduces the weight of the driven wheel side defensive and torque up to the upper limit where there is no failure in the shaft, ensuring the traction performance and preventing the increase in slip due to the increase in engine power before it actually occurs It becomes possible to do.
[0015]
In claim 5, the driving force generated by the engine is directly transmitted to the front wheel or the rear wheel, and the driving force of the motor is transmitted to the other wheel, and the output of the motor is previously determined according to the running state of the vehicle. In a driving force distribution control device for a four-wheel drive vehicle that controls the vehicle within a range up to a set upper limit value,
A technical feature is that a slip suppression request signal is transmitted when the rotation difference between the front wheels and the rear wheels exceeds a predetermined value while the output of the motor is increased to the upper limit value.
[0016]
In the driving force distribution control device according to the fifth aspect, when a slip occurs, a request signal for slip suppression is not transmitted until the output of the motor is increased to the upper limit value, and the engagement force is increased. . For this reason, the trunk performance can be ensured, and the running performance can be enhanced. On the other hand, when the rotation difference between the front wheels and the rear wheels exceeds a predetermined value while the output of the motor is increased to the upper limit, a request signal for slip suppression is transmitted. As a result, it is possible to ensure the traction performance without control delay while applying torque to the driven wheels to the upper limit with a motor having a limited output.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a driving force distribution device according to a first embodiment of the present invention will be described with reference to the drawings. In the first embodiment, an example will be described in which the driving force distribution device 20 and the driving force distribution control device 30 for controlling the driving force distribution device 20 are mounted on a four-wheel drive vehicle.
[0018]
As shown in FIG. 1, the vehicle V is based on a so-called FF vehicle in which an engine EG is mounted in front of the vehicle and drives front wheels FR and FL. At the time of driving the vehicle V, the driving force generated from the engine EG is transmitted to the front drive shaft FDS by the front differential FD to drive the front wheels FR and FL via the transmission TM, and the transmission TM and the transfer TF are transmitted. The driving force transmitted to the second propeller shaft PSb via the driving force distribution device 20 and the rear differential RD is transmitted to the rear drive shaft RDS for driving the rear wheels RR and RL.
[0019]
Here, the driving force distribution device 20 has a function of outputting the driving force input from the second propeller shaft PSb to the rear differential RD at an arbitrary ratio by employing a configuration described later.
[0020]
As shown in FIG. 1, the front wheels FR, FL and the rear wheels RR, RL are provided with wheel speed sensors WSa, WSb, WSc, WSd, respectively, capable of detecting the rotation speed of the wheels, and the engine A throttle valve (not shown) provided in the middle of the intake path of the EG is provided with a throttle opening sensor SV capable of detecting its opening. The wheel speed signal (WSa-d) and the throttle opening signal (SV) output from each of these sensors are sent to the driving force distribution control device 30 and the engine control device 40 for controlling the engine EG as sensor information. Will be entered.
[0021]
On the other hand, the wheel speed signals (WSa-d) from the wheel speed sensors WSa, WSb, WSc, WSd are also input to the vehicle stability control device 50. The vehicle stability control device 50, based on a wheel speed signal (WSa-d) and signals from a G sensor and a yaw rate sensor (not shown), applies a brake BKa of the front wheel FR, a brake BKb of the front wheel FL, a brake BKc of the rear wheel RR, The brakes BKc of the rear wheels RL are individually operated to secure the stability of the turning direction of the vehicle.
[0022]
Here, the configuration of the driving force distribution device 20 will be described based on FIG. FIG. 2A is a partial cross-sectional view showing the configuration of the driving force distribution device 20 according to the present embodiment. Since the driving force distribution device 20 has a substantially symmetric configuration with respect to the rotation axis L, FIG. In addition, a substantially half portion of the driving force distribution device 20 is shown, and the other approximately half portion is omitted.
[0023]
As shown in FIG. 2A, the driving force distribution device 20 mainly includes an outer case 20a, an inner shaft 20b, a main clutch mechanism 20c, a pilot clutch mechanism 20d, a cam mechanism 20e, and the like.
[0024]
The outer case 20a is formed by a bottomed cylindrical housing 21a and a rear cover 21b fitted and screwed into a rear end opening of the housing 21a to cover the opening. The front end of the housing 21a constituting the outer case 20a is connected to the end of the second propeller shaft PSb shown in FIG. 1 so as to transmit torque.
[0025]
The inner shaft 20b is coaxially inserted into the outer case 20a through the center of the rear cover 21b in a liquid-tight manner, and is rotatably supported by the housing 21a and the rear cover 21b in a state where the axial direction is restricted. Have been. A rear differential RD shown in FIG. 1 is connected to the inner shaft 20b so as to be able to transmit torque.
[0026]
The main clutch mechanism 20c is a wet-type multi-plate type friction clutch, includes a plurality of clutch plates including an inner clutch plate 22a and an outer clutch plate 22b, and is disposed in the housing 21a. Each inner clutch plate 22a is spline-fitted to the outer periphery of the inner shaft 20b, and is assembled so as to be movable in the axial direction. Each outer clutch plate 22b is spline-fitted to the inner periphery of the housing 21a and is mounted so as to be movable in the axial direction. The inner clutch plates 22a and the outer clutch plates 22b are alternately arranged, abut against each other and frictionally engage, and are separated from each other to be in a free state.
[0027]
The pilot clutch mechanism 20d is an electromagnetic clutch, and includes an electromagnet 23, a friction clutch 24, an armature 25, and a yoke 26.
The annular electromagnet 23 includes an electromagnetic coil 23a wound around the rotation axis L, and is fitted to the annular gallery 21d of the rear cover 21b via a predetermined gap while being fitted to the yoke 26. The yoke 26 is fixed to the vehicle body while being rotatably supported on the outer periphery of the rear end of the rear cover 21b.
[0028]
The rear cover 21b includes an inner cylindrical portion made of a magnetic material having a substantially L-shaped cross section in a radial direction, an outer cylindrical portion made of a substantially annular magnetic material provided on the outer periphery of the inner cylindrical portion, and an inner cylindrical portion thereof. And a blocking member 21c made of a substantially annular non-magnetic material and fixed between the outer cylindrical portion.
[0029]
The friction clutch 24 is a wet-type multi-plate friction clutch including a plurality of clutch plates including an outer clutch plate 24a and an inner clutch plate 24b. Each outer clutch plate 24a is spline-fitted to the inner periphery of the housing 21a and is mounted so as to be movable in the axial direction. Further, each inner clutch plate 24b is spline-fitted to the outer periphery of the first cam member 27a constituting the cam mechanism 20e, and is assembled so as to be movable in the axial direction.
[0030]
The annular armature 25 is spline-fitted to the inner periphery of the housing 21a and is assembled so as to be movable in the axial direction. The annular armature 25 is arranged on the front side of the friction clutch 24 and faces the friction clutch 24. As a result, an exciting current that excites the electromagnet 23 is supplied to the electromagnetic coil 23a, so that a magnetic flux circulating in the path of the yoke 26 → the rear cover 21b → the friction clutch 24 → the armature 25 passes from the electromagnet 23 as a base point. A path is formed.
[0031]
The cam mechanism 20e includes a first cam member 27a, a second cam member 27b, and a cam follower 27c. The first cam member 27a is rotatably fitted to the outer periphery of the inner shaft 20b and rotatably supported by the rear cover 21b, and the inner clutch plate 24b of the friction clutch 24 is spline-fitted to the outer periphery. I have. The second cam member 27b is spline-fitted to the outer periphery of the inner shaft 20b and is assembled so as to be integrally rotatable. The second cam member 27b is arranged to face the rear side of the inner clutch plate 22a of the main clutch mechanism 20c. A ball-shaped cam follower 27c is fitted in the opposing cam grooves of the first cam member 27a and the second cam member 27b.
[0032]
In the driving force distribution device 20 configured as described above, the exciting current flowing through the electromagnetic coil 23a of the electromagnet 23 is controlled to a predetermined current value set by the duty control in the driving force distribution control device 30. Accordingly, when the electromagnetic coil 23a of the electromagnet 23 constituting the pilot clutch mechanism 20d is in a non-energized state, that is, when no exciting current is supplied, no magnetic path is formed, and the friction clutch 24 is in an unengaged state. , The pilot clutch mechanism 20d enters the non-operating state. Then, the first cam member 27a constituting the cam mechanism 20e can rotate integrally with the second cam member 27b via the cam follower 27c, and the main clutch mechanism 20c is in a non-operating state. The drive mode is set.
[0033]
On the other hand, when an exciting current is applied to the electromagnetic coil 23a of the electromagnet 23, a loop-shaped circulating magnetic path starting from the electromagnet 23 is formed in the pilot clutch mechanism 20d, and a magnetic force is generated. Suction. Therefore, the armature 25 presses the friction clutch 24 and frictionally engages to generate torque, connects the first cam member 27a of the cam mechanism 20e to the outer case 20a side, and relatively moves between the first cam member 27a and the second cam member 27b. Cause rotation. Then, in the cam mechanism 20e, a thrust force that causes the cam follower 27c to move the two cam members 27a, 27b in a direction to separate from each other is generated.
[0034]
As a result, the second cam member 27b is pushed toward the main clutch mechanism 20c, and presses the main clutch mechanism 20c between the inner wall portion of the housing 21a and the second cam member 27b, and responds to the frictional engagement force of the friction clutch 24. As a result, the main clutch mechanism 20c is frictionally engaged, so that torque is transmitted between the outer case 20a and the inner shaft 20b, and the vehicle V is switched between a state where the second propeller shaft PSb and the rear differential RD are not connected and a state where the rear differential RD is locked. Between the four-wheel drive mode. In the four-wheel drive mode, the driving force distribution ratio between the front wheels FR, FL and the rear wheels RR, RL can be controlled in a range from 100: 0 (two-wheel drive state) to the locked state according to the running state of the vehicle. it can.
[0035]
Here, a configuration of the driving force distribution control device 30 that performs the duty control of the exciting current and an example of the driving force distribution control will be described with reference to FIGS.
As shown in FIG. 2B, the driving force distribution control device 30 includes a peripheral LSI such as an A / D converter, an MPU (Micro Processor Unit) having a memory and the like, an input / output interface I / F, and the like. Various sensor information and the like can be input via the input / output interface I / F. The driving force distribution control device 30 is connected to an electromagnetic clutch driving circuit 35 that can drive the electromagnet 23 of the driving force distribution device 20. Thus, the driving force distribution device 20 can be controlled according to a predetermined control program stored in the memory.
[0036]
For example, in the driving force distribution control device 30 of the present embodiment, the driving force distribution control as shown in FIG.
That is, when a wheel speed signal output from the wheel speed sensors WSa, WSb, WSc, WSd is input, the ΔN calculation unit 30a calculates a wheel speed difference ΔN (= front wheel) between the front wheels FR, FL and the rear wheels RR, RL. A process of calculating (wheel speed−rear wheel speed) is performed, and the calculation result is output to the ΔN torque calculation unit 30d. Further, when the wheel speed signal is input to the vehicle speed calculation unit 30c, the vehicle speed calculation unit 30c calculates the traveling speed of the vehicle V, that is, the vehicle speed, and outputs the vehicle speed information to the ΔN torque calculation unit 30d. .
[0037]
Further, by inputting the throttle opening signal output from the throttle opening sensor SV to the ΔN torque calculating section 30d, the ΔN torque calculating section 30d converts the front and rear wheel speed difference ΔN, the vehicle speed information and the throttle opening signal into Based on the calculation, a calculation process for obtaining the ΔN torque from a predetermined calculation expression or a predetermined reference map is performed. Therefore, the ΔN torque thus obtained is added to the output of the pre-torque calculating section 30e and output to the command current calculating section 30f.
[0038]
On the other hand, the throttle opening signal output from the throttle opening sensor SV and the vehicle speed information calculated by the vehicle speed calculating unit 30c are also input to the pre-torque calculating unit 30e, and the predetermined calculation formula or the predetermined Calculation processing for obtaining the pre-torque from the reference map is performed. This pre-torque is added to the output of the ΔN torque calculator 30d and output to the command current calculator 30f.
[0039]
As a result, in the command current calculation unit 30f, a process of converting the command torque obtained by adding the ΔN torque and the pre-torque by the adding unit to a torque current is performed, and a current command value for generating the target torque is generated. Therefore, a difference between the current command value and the current detection signal detected by the current detection circuit 37 is calculated by an adder, and the difference is input to the PI controller 30g.
[0040]
By performing such a proportional-integral control, the exciting current to be given to the electromagnet 23 of the driving force distribution device 20 can be calculated. By applying the width modulation, the duty control of the driving force distribution device 20 by the driving circuit 35 becomes possible. The excitation current flowing through the electromagnet 23 by such duty control is detected by the current detection circuit 37, and the difference between the excitation current and the current command value is calculated by the above-described addition unit, so that a current feedback loop is formed.
[0041]
When the front and rear wheel speed difference ΔN changes based on the behavior of the vehicle V by the driving force distribution control device 30, the command torque, that is, the front wheels FR and FL and the rear wheels RR by the driving force distribution device 20 are changed. , RL is determined and the behavior of the vehicle V changes, thereby forming a feedback loop in which a new command torque is determined. Therefore, the ΔN torque calculated by the ΔN torque calculation unit 30d may be referred to as feedback torque. On the other hand, since the pre-torque calculated by the pre-torque calculating unit 30e is obtained based on information known in advance such as a throttle opening signal and vehicle speed information which fluctuate according to the amount of depression of the accelerator pedal by the driver, the feed-forward is used. Sometimes referred to as torque.
[0042]
Note that an upper limit torque value that can be applied to the rear wheels RR and RL is set in the command current calculation unit 30f, and the command torque is adjusted within this range. The vehicle V achieves light weight and low fuel consumption by limiting the torque applied to the rear wheels RR, RL side defensive RD and rear drive shaft RDS.
[0043]
For this reason, when the torque generated by the engine EG further increases while the command torque has reached the upper limit, all of the additional torque is added to the front wheel side. That is, by slipping on the front wheel side, the rotation difference between the front wheel and the rear wheel increases, and when the torque applied to the rear wheel is increased to an allowable maximum and the torque generated by the engine EG increases, By adding the additional amount of torque to the front wheel side, the slip is further increased.
[0044]
In order to prevent such a situation, the flag output unit 30i of the driving force distribution control device 30 receives the front and rear wheel speed difference ΔN from the ΔN calculation unit 30a and the vehicle speed information from the vehicle speed calculation unit 30c, and sets the command torque to the upper limit. In this state, when the rotation difference between the front wheels and the rear wheels (the front-rear wheel speed difference ΔN) further increases, and the front-rear wheel speed difference ΔN further increases in a short time, the engine control device 40 and the vehicle stability control A slip suppression command for causing the device 50 to perform control for suppressing the occurrence of slip is output. That is, by preventing the engine output from being increased by the engine control device 40, an increase in slip at the front wheels FR and FL is prevented beforehand. Similarly, the brake BKa of the front wheels FR is similarly controlled by the vehicle stability control device 50. The brake BKb of the front wheel FL is operated to prevent an increase in slip at the front wheels FR and FL.
[0045]
Next, control of the driving force distribution device 20 by the driving force distribution control device 30 of the vehicle V will be described based on the flowchart of FIG.
First, it is determined whether the command torque is the upper limit torque value (the maximum value that can be applied to the rear wheels) (S12). Here, until the command torque reaches the upper limit torque (S12: No), normal normal control for increasing the torque applied to the rear wheels according to the front-rear wheel speed difference ΔN described above with reference to FIG. 3 is performed (S18). . When the command torque reaches the upper limit torque (S12: Yes), whether the front and rear wheel speed difference ΔN is equal to or greater than a preset threshold value and whether the increasing speed of the front and rear wheel speed difference ΔN is equal to or greater than a preset threshold value or not. Is determined (S14). Here, the increasing speed of the front-rear wheel speed difference ΔN can be obtained from the difference between the speed at the previous determination and the current speed.
[0046]
If the front and rear wheel speed difference ΔN is equal to or greater than a preset threshold value and the increasing speed of the front and rear wheel speed difference ΔN is not equal to or greater than a preset threshold value (S14: No), a slip suppression command to be described later is issued. After the determination as to whether or not the slip is being suppressed (S20: No), the above-described normal control is performed (S18).
[0047]
Here, when the front and rear wheel speed difference ΔN is equal to or greater than a preset threshold value and the increasing speed of the front and rear wheel speed difference ΔN is equal to or greater than a preset threshold value (S14: Yes), the engine control device 40 and the vehicle starter The slip control device 50 outputs a slip suppression command for causing the control device 50 to perform control for suppressing the occurrence of slip (S22). After that, when the output of the engine EG is reduced or the operation of the brakes BKa and BKb, the front-rear wheel speed difference ΔN is equal to or less than a preset threshold or the increase speed is equal to or less than a preset threshold (S14: No), the determination as to whether the slip is being suppressed in S16 is Yes, and a return process to the normal control is performed (S20). That is, the process is gradually switched from the above-described process during the slip suppression to the normal control so as not to impair the stability of the vehicle.
[0048]
In the driving force distribution control device 30 of the first embodiment, when a slip occurs, a request signal for reducing the engine torque is transmitted to the engine control device 40 until the engagement force of the driving force distribution device 20 is increased to the upper limit value. This is done by increasing the engagement force without transmitting a signal requesting a braking operation to the vehicle stability control device 50 without increasing the engagement force. For this reason, the trunk performance can be ensured, and the running performance can be enhanced. On the other hand, if the rotational difference between the front wheels and the rear wheels exceeds a predetermined value and the increasing speed exceeds a predetermined value while the engagement force of the driving force distribution device 20 is increased to the upper limit, the engine A request signal for lowering the engine torque is transmitted to control device 40. Further, a request signal for requesting the vehicle stability control device 50 to perform a braking operation is transmitted. As a result, the torque is increased to the upper limit where the rear rear RD and the rear drive shaft RDS, which are reduced in weight, do not cause any trouble in the rear drive shaft RDS, and the traction is secured. Before it occurs.
[0049]
In the above-described first embodiment, the slip suppression command is output when the front and rear wheel speed difference ΔN is equal to or greater than a preset threshold and the increase speed is equal to or greater than a preset threshold. Thus, a slip suppression command can be output. Further, although the slip suppression command is output to both the engine control device 40 and the vehicle stability control device 50, it may be output to only one of them.
[0050]
Subsequently, a vehicle according to a first modification of the first embodiment will be described with reference to FIG. In the first embodiment described above with reference to FIG. 1, non-constant four-wheel drive is realized based on a front-wheel drive vehicle. On the other hand, in the first modified example of the first embodiment, non-constant four-wheel drive is realized based on a rear-wheel drive vehicle. That is, the output from the engine EG is transmitted to the rear differential RD that drives the rear wheels RR and RL via the transmission TM and the driving force distribution control device 20, while the driving force distribution control device 20 and the transfer TF are transmitted. Through the front rear differential FD that drives the front wheels FR and FL. The outline of the driving force distribution control device 20 according to the first modification of the first embodiment is the same as that of the above-described first embodiment, and thus the description thereof is omitted. The control of the clutch can be applied not only to the above-described electromagnetic clutch, but also to a method of controlling the pressing force by hydraulic pressure, or a method of changing the motor rotational force to a pressing force via a cam mechanism and controlling it.
[0051]
Next, a vehicle according to a second modification of the first embodiment will be described with reference to FIG. In the first embodiment described above with reference to FIG. 1, the vehicle is driven only by the engine. On the other hand, in the second modification of the first embodiment, the hybrid vehicle HV including the engine EG and the electric motor M is configured. Power from the battery is applied to the motor M via an inverter controlled by the inverter control device 70. At the time of regeneration, the power generated by the motor M is stored in the battery via the inverter. When the hybrid vehicle HV is driven, a driving force generated from at least one of the engine EG and the electric motor M is transmitted to the first propeller shaft PSa and the second propeller shaft PSb via the transmission TM and the transfer TF. The driving force transmitted to the first propeller shaft PSa is transmitted to the front drive shaft FDS via the front differential FD to drive the front wheels FR and FL, and is transmitted to the second propeller shaft PSb. The force is transmitted to the rear drive shaft RDS via the driving force distribution device 20 and the rear differential RD to drive the rear wheels RR, RL.
[0052]
On the other hand, at the time of braking of the hybrid vehicle HV, when the driver depresses a brake pedal (not shown), the brake mechanisms BKa, BKb, BKc, and BKd operate, and the front wheels FR, FL and the rear wheels RR, The RLs are respectively braked. At the same time, at the time of braking, the electric motor M operates as a generator via the first propeller shaft PSa, the transfer TF, and the transmission TM due to the rotation of the front wheels FR, FL. FR and FL are braked. The outline of the driving force distribution control device 20 according to the second modified example of the first embodiment is the same as that of the above-described first embodiment, and thus the description is omitted.
[0053]
Subsequently, a vehicle according to the second embodiment will be described with reference to FIG. In the first embodiment described above, the driving force of the engine or the motor is directly transmitted to the main driving wheel, and also transmitted to the driven wheel via the driving force distribution control device. On the other hand, in the second embodiment, the front wheels FR and FL are directly driven by the engine EG, and the rear wheels RR and RL are driven by the motor M controlled by the motor control device 130. That is, when a slip occurs in the front wheels and the rotation difference ΔN between the front wheels and the rear wheels increases, the rear wheels RR and RL are driven by the motor M, and four-wheel drive is performed. The motor M is driven by electric power generated in the engine EG.
[0054]
In the second embodiment, the output of the motor M is set to a fraction of the output of the engine EG. For this reason, the motor control device 130 responds by increasing the engagement force without transmitting the slip suppression request signal until the output of the motor M is increased to the upper limit value when the slip occurs. For this reason, the trunk performance can be ensured, and the running performance can be enhanced. On the other hand, if the rotation difference between the front wheels and the rear wheels exceeds a predetermined value while the output of the motor M is increased to the upper limit, a request signal for slip suppression is transmitted. As a result, it is possible to secure the traction performance without control delay while applying torque to the rear wheel to the upper limit by the motor M whose output is limited.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a schematic configuration of a four-wheel drive vehicle equipped with a driving force distribution control device according to a first embodiment of the present invention.
FIG. 2A is a partial cross-sectional view illustrating a configuration of the driving force distribution device shown in FIG. 1, and FIG. 2B is a block diagram illustrating control of the driving force distribution device.
FIG. 3 is a block diagram illustrating a driving force distribution control device according to the first embodiment.
FIG. 4 is a flowchart illustrating a flow of a process performed by the driving force distribution control device according to the first embodiment.
FIG. 5 is an explanatory diagram illustrating a schematic configuration of a four-wheel drive vehicle equipped with a driving force distribution control device according to a first modification of the first embodiment.
FIG. 6 is an explanatory diagram illustrating a schematic configuration of a four-wheel drive vehicle equipped with a driving force distribution control device according to a second modification of the first embodiment.
FIG. 7 is an explanatory diagram illustrating a schematic configuration of a four-wheel drive vehicle equipped with a driving force distribution control device according to a second embodiment.
[Explanation of symbols]
20 Driving force distribution device
20a Outer case
20b Inner shaft
20c Main clutch mechanism (torque distribution clutch)
20d pilot clutch mechanism
20e cam mechanism
30 Driving force distribution control device
40 Engine control device
50 Vehicle stability control device (brake control device)
130 Motor control device (drive power distribution device)
EG engine
M motor
FR, FL Front wheel
RR, RL front wheel
WSa, WSb, WSc, WSd Wheel speed sensor

Claims (5)

The driving force generated by the engine or the motor is directly transmitted to the front wheels or the rear wheels, and the driving force is transmitted to the other wheel via a torque distribution clutch. In a driving force distribution control device for a four-wheel drive vehicle that controls the engaging force of a clutch for use in a range up to a preset upper limit value.
When the rotational difference between the front wheel and the rear wheel exceeds a predetermined value in a state where the engaging force of the torque distribution clutch is increased to the upper limit value, a request signal for slip suppression is transmitted. Driving force distribution control device. The driving force generated by the engine or the motor is directly transmitted to the front wheels or the rear wheels, and the driving force is transmitted to the other wheel via a torque distribution clutch. In a driving force distribution control device for a four-wheel drive vehicle that controls the engaging force of a clutch for use in a range up to a preset upper limit value.
In a state where the engagement force of the torque distribution clutch is increased to the upper limit value, when the speed of increase of the rotation difference between the front wheel and the rear wheel exceeds a predetermined value, transmitting a slip suppression request signal. Characteristic drive power distribution control device. The driving force distribution control device according to claim 1 or 2, wherein the slip suppression request signal is a request signal to the engine control device to reduce the engine torque. The claim signal according to claim 1, wherein the slip suppression request signal is a request signal to a brake control device that requests a brake operation on a front wheel or a rear wheel side to which driving force is directly transmitted. Item 2. The driving force distribution control device according to Item 2. The driving force generated by the engine is directly transmitted to the front wheel or the rear wheel, and the driving force of the motor is transmitted to the other wheel, and the output of the motor is set to a predetermined upper limit value in accordance with the running state of the vehicle. In a driving force distribution control device for a four-wheel drive vehicle that controls in the range up to
When the output of the motor is increased to the upper limit and a rotation difference between a front wheel and a rear wheel exceeds a predetermined value, a request signal for slip suppression is transmitted, wherein a driving force distribution control is performed. apparatus.

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