JP2646820B2 - Driving force distribution control device for four-wheel drive vehicle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a driving force distribution control device for a four-wheel drive vehicle in which the front and rear wheel driving force distribution can be changed, and more particularly, to a countermeasure for mounting front and rear wheels having different diameters.

2. Description of the Related Art Conventionally, as a driving force distribution control device for a four-wheel drive vehicle, for example, as disclosed in Japanese Patent Application Laid-Open No. 63-13331, the rotational speed difference from front and rear wheel rotational speed difference detecting means is known. There is known a device that increases / decreases a clutch engagement force based on a detected value and makes a distribution of front and rear wheels of an engine driving force variable, and suppresses a driving wheel slip while taking advantage of maneuverability which is an advantage of a rear wheel drive vehicle. In order to improve performance, the relationship between the front and rear wheel rotational speed difference (rear wheel-front wheel) and the clutch engagement force (front wheel drive torque) is determined. When the front and rear wheel rotational speed difference is small, the front wheel drive torque is reduced, and the front and rear wheel rotational speed difference is reduced. The setting is such that the characteristic that the front wheel drive torque increases as the value increases, and the control is such that the front and rear wheel rotational speed difference always converges to zero.

(Problems to be Solved by the Invention) However, in such a conventional driving force distribution control device, the detected value of the front and rear wheel rotational speed difference is regarded as the front and rear wheel speed difference due to the drive wheel slip, and based on this detected value. This is a device that controls the clutch engagement force of the torque distribution clutch, and does not take into account the effect of the rotational speed difference due to the tire diameter difference between the front and rear wheels. Power is applied.

That is, as shown in FIG. 7, the front and rear wheel rotational speed difference detector value ΔV _W is equal to the front and rear wheel rotational speed ΔV due to the drive wheel slip.
The _S (reduced by the clutch engagement tends), is output by the value obtained by adding the rotational speed difference [Delta] V _T due to tire diameter difference between the front and rear wheels becomes larger in accordance with the independent increase of the vehicle speed and the clutch engagement, rises according to the vehicle speed A clutch engagement force T _M ′ is provided.

As a result, unpleasant vertical vibrations (bulble vibrations) occur especially during high-speed running, and clutch slippage (= ΔV _S
+ ΔV _T ) intense heat generation raises the oil temperature of the transfer and differential, causing problems such as a decrease in durability and deterioration of fuel efficiency.

Causes of the tires of the front and rear wheels having different diameters include, for example, when a tempered tire is mounted, uneven wear, when the tire pressure is different, and when the wheel load changes due to an increase or decrease in the number of occupants. When it is seen, the diameter is larger or smaller.

Further, the unpleasant vibration at the time of high-speed running was confirmed by an experiment, and although the cause is not clear, at least not the fluctuation of the clutch fastening force, but the variation of the tire diameter of the front and rear wheels as shown in FIG. It is considered that some resonance phenomenon occurs in the drive system when the front and rear wheels with a large difference in rotation are forcibly slid and fastened by the addition of the difference in rotation speed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problem, and is directed to a torque split type four-wheel transmission system in which engine driving force is directly transmitted to one of front and rear wheels and transmitted to the other via a torque distribution clutch. It is an object of the present invention to improve the durability of a transfer and a differential, prevent vibrations from occurring, and prevent fuel consumption from lowering without losing the function of controlling the difference between front and rear wheel rotational speeds when detecting the mounting of different diameter tires in a wheel drive vehicle.

(Means for Solving the Problems) In order to solve the above problems, in the driving force distribution control device for a four-wheel drive vehicle according to the present invention, as shown in the claim correspondence diagram of FIG. 1, the engine is directly connected to one of the front and rear wheels. A clutch a for torque distribution, which is provided in the middle of the drive system to the other of the front and rear wheels to enable the transmitted engine drive force to be changed by external engagement control, and detects a rotational speed difference between the front and rear wheels. Front and rear wheel rotational speed difference detecting means b, vehicle speed detecting means c for detecting a vehicle speed, and a clutch torque average value equal to or greater than a set torque is continuously applied for a set time or more during high-speed running when the vehicle average value exceeds a set value. A different-diameter tire mounting detecting means d for detecting the mounting of a different-diameter tire, and a tire-diameter difference calculating means for calculating a tire-diameter difference based on an average value of a vehicle speed and an average value of a clutch torque when detecting the mounting of a different-diameter tire. When a different-diameter tire is not detected, a fastening force command that increases as the front and rear wheel rotational speed difference detection value increases is output to the torque distribution clutch a. When a different-diameter tire is detected, the tire diameter difference and the vehicle speed are detected. The engagement force of the torque distribution clutch a is controlled based on the front and rear wheel rotation speed difference correction value obtained by removing the front and rear wheel rotation speed difference of the tire diameter difference obtained from the tire diameter difference from the front and rear wheel rotation speed difference detection value, as in the case of non-detection. And a driving force distribution control means f.

(Operation) During high-speed running in which the average vehicle speed exceeds the set value, the different-diameter tire mounting detecting means d detects the different-diameter tire because the clutch torque average of the set torque or more is continuously applied for the set time or more. When it is detected that the tires with different diameters are attached, the tire diameter difference calculating means e calculates the tire diameter difference based on the average vehicle speed and the average clutch torque.

Then, at the time of detection of mounting of different diameter tires, the driving force distribution control means f outputs to the torque distributing clutch a a fastening force command that increases as the front and rear wheel rotational speed difference detection value increases, and detects the front and rear wheel rotational speed difference. The value is used as the drive wheel slip information, and the larger the detected value of the front and rear wheel rotational speed difference is, the more the drive force is distributed on the four-wheel drive side, so that the drive wheel slip is suppressed.

On the other hand, at the time of detecting the installation of different diameter tires, the driving force distribution control means f removes the front and rear wheel rotation speed difference from the front and rear wheel rotation speed difference of the tire diameter difference obtained from the tire diameter difference and the vehicle speed. The engaging force of the torque distribution clutch a is controlled based on the difference correction value in the same manner as in the non-detection state.

Therefore, the front and rear wheel rotation speed difference correction value is a value in which the influence of the front and rear wheel rotation speed difference effect by the different diameter tire included in the front and rear wheel rotation speed difference detection value has been removed, and is the same as when non-detection of different diameter tire mounting is not performed. The larger the front and rear wheel rotational speed difference correction value,
The driving force is distributed on the wheel drive side, and the driving wheel slip is suppressed.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 is an overall system diagram including a drive system to which a torque split control system (driving force distribution control device) of a four-wheel drive vehicle is applied. First, the configuration will be described.

The vehicle to which the torque split control system of the embodiment is applied is a rear-wheel-based four-wheel drive vehicle, which includes an engine 1, a transmission 2, a transfer input shaft 3, a rear propeller shaft 4, a rear differential 5, and a rear differential 5. Wheel 6,
It has a transfer output shaft 7, a front propeller shaft 8, a front differential 9, and a front wheel 10, and a rear wheel 6
The engine driving force passing through the transmission 2 is directly transmitted to the front wheel 10, and the front wheel 10 is provided with a transfer 11 provided between the transfer input / output shafts 3 and 7, which is a front wheel drive system.
Is transmitted via

The torque split control system that optimally controls the distribution of the driving force between the front and rear wheels while achieving both the driving performance and the steering performance is based on the above-described truss 11 having a built-in wet multi-plate friction clutch 11a. 63-325379), a control oil pressure generator 20 for generating a control oil pressure Pc serving as a clutch engagement force, and various input sensors to a solenoid valve 28 provided in the control oil pressure generator 20.
And a torque split controller 40 that outputs a predetermined dither current i ^* based on the information from 30.

The hydraulic control device 20 includes a motor 22 that is driven or stopped by a relief switch 21, a hydraulic pump 24 that is operated by the motor 22 and draws up from a reservoir tank 23, and a pump discharge pressure (primary pressure) from the hydraulic pump 24. An accumulator 26 stored via a check valve 25, and a solenoid valve 28 for adjusting a line pressure (secondary pressure) from the accumulator 26 to a predetermined control oil pressure Pc by a solenoid driven dither current i ^* from a torque split control unit 40. The hydraulic oil of the control oil pressure Pc passes through the control oil pressure pipe 29 and is supplied to the clutch port.

As the various input sensors 30, as shown in the block diagram of the system electronic control system of FIG.
30a, a front right wheel rotation sensor 30b, a rear left wheel rotation sensor 30c, a rear right wheel rotation sensor 30d, a first lateral acceleration sensor 30e, and a second lateral acceleration sensor 30f.

As shown in the block diagram of the system electronic control system of FIG. 3, the torque split control unit 40 includes a left front wheel speed calculation circuit 40a, a right front wheel calculation circuit 40b, a left rear wheel speed calculation circuit 40c, and a right rear wheel speed calculation circuit. Circuit 40d, front wheel speed calculation circuit 40e, rear wheel speed calculation circuit 40f,
Rotational speed difference calculation circuit 40g, fastening force calculation circuit 40h, Ti conversion circuit 40i, dither current output circuit 40j, lateral acceleration calculation circuit 40
l, gain calculation circuit 40m, different diameter tire mounting detection circuit 40n, tire diameter difference calculation circuit 40p, front and rear wheel rotational speed difference dead zone setting circuit 40
q, which has a fail-safe circuit 40r.

In the figure, A / D is an A / D converter, and D / A is a D / A converter.

Further, an alarm lamp 50 is connected to the fail-safe circuit 40r.

 Next, the operation will be described.

FIG. 4 is a flowchart showing the flow of the front and rear wheel driving force distribution control operation performed by the torque split controller 40. Each step will be described below in order.

In step 80, the left front wheel speed V _WFL , the right front wheel speed V _WFR , the left rear wheel speed V _WRL , the right rear wheel speed V _WRR , the first lateral acceleration Y _G1 , and the second lateral acceleration Y _G2 are input.

In step 81, as the input processing, the left front wheel speed V _WFL
The front wheel speed V _WF is calculated from the average value of the front right wheel speed V _WFR and the right front wheel speed V _WFR, and the rear wheel speed V _WR is calculated from the average value of the left rear wheel speed V _WRL and the right rear wheel speed V _WRR. Acceleration Y _G1 and second lateral acceleration
The lateral acceleration Y _G is calculated from the average value of Y _G2 and the front wheel speed V _WF
There is as it is set as the vehicle speed V _i.

In step 82, the front wheel speed V _WF and the rear wheel speed V _WR front and rear and a wheel rotation speed difference detected value ΔV (= V _WR -V _WF; however, [Delta] V ≧ 0)
Is calculated.

In step 83, by the following equation based on the reciprocal of the control gain K _n is the lateral acceleration detected value Y _G of the clutch torque output value TiderutaV _OUT for the front and rear wheel rotational speed difference detected value [Delta] V or the front and rear wheel rotational speed difference correction value [Delta] V ' Is calculated.

_{K n = a n / Y G} ( where, K _n ≦ _{β n)} For example, the beta _n = 10 in alpha _n = 1.

In step 84, the clutch torque TΔV is calculated by the above control gain K _n and the front and rear wheel rotational speed difference detected value [Delta] V.

In step 85, it is determined whether the different-diameter tire attachment detection flag FS3 is FS3 = 1 indicating that the different-diameter tire is attached, or FS3 = 0 indicating that the different-diameter tire is not attached.

Then, when FS3 = 0, Step 86 to Step 90
In, a process of detecting the attachment of a different-diameter tire is performed.

That is, in step 86, the clutch torque average value ▲
▼ and the average vehicle speed value ▲ ▼ are calculated by the average of the period of 5 sec.
It is determined whether ▼ exceeds the set value x and the vehicle speed average ▲ ▼ exceeds the set value _VHT . If YES in step 87, the high clutch torque determination flag HTFLG is set to 1 in step 88, and in step 89, it is determined whether or not HTFLG = 1 continues for 5 minutes. In other words, when the condition that simultaneously satisfies the high clutch torque condition and the high vehicle speed condition occurs continuously for 5 minutes or more, which is a time period that cannot be achieved in normal acceleration running, it is detected that the tires of different diameters are being mounted. Then, the different-diameter tire attachment detection flag FS3 is rewritten to FS3 = 1 indicating the attachment of the different-diameter tire.

On the other hand, when the condition of step 87 is not satisfied, the high clutch torque discrimination flag HTFLG is set to HTFLG = 0 in step 91, and the different diameter tire attachment detection flag FS3 is set to FS3 in step 92.
= 0, and when the continuous condition in step 89 is not satisfied, in step 92, the different-diameter tire attachment detection flag FS3 is set to F
S3 = 0 is set.

Then, at the time of non-detection of the attachment of the different diameter tire, in step 93, the clutch torque TΔV obtained in step 84 is obtained.
Is set as a clutch torque output value TΔV _OUT , and in step 94, the clutch torque output value TΔV _OUT is converted into a solenoid drive current i which can be obtained based on a predetermined Ti characteristic table. For 28, the dither current i ^* (for example, i ±
0.1A 100Hz) is output.

At the time of detecting the attachment of the different diameter tire, the flow from Step 90 to Step 96 is performed.

At step 96, upon receiving the detection of the mounting of the different-diameter tire in step 90, the alarm lamp 50 is turned on and off to notify the driver that the different-diameter tire is being mounted.

In step 97, it is determined whether the front and rear wheel rotation speed difference detection value ΔV is positive or negative. If ΔV <0 and the front and rear wheel rotation speed difference has occurred without causing a drive wheel slip, the process proceeds to step 97.
The deceleration-side normal control after 93 is performed.

In step 98, the tire diameter difference Δr is set to the fifth based on the vehicle speed average ▲ ▼ and the clutch torque average ▲ ▼.
The search is performed using the map shown in the figure.

In this map, the average vehicle speed ▲ ▼ is small,
The tire diameter difference Δr is large when the clutch torque average value ▼▼ is large, and the tire diameter difference Δr is small when the clutch torque average value ▼▼ is large.

In steps 99 and 100, the set gain K _{OFF of} the front and rear wheel rotational speed difference dead zone ΔV _OFF is calculated by the following equation based on the lateral acceleration detection value Y _G and the tire diameter difference Δr.

K _a = α _i / Y _G (However, when Y _G = 0, K _a = β _i ) K _OFF = K _a · Δr That is, the set gain K _OFF decreases as the lateral acceleration detection value Y _G increases. The larger the tire diameter difference Δr is, the larger the value is set.

In step 101, the front and rear wheel rotational speed difference dead zone ΔV
_OFF is calculated by the following equation by setting the gain K _OFF and the vehicle speed V _i.

In ΔV _OFF = K _OFF · V _i step 102, is calculated by the following formula by the front and rear wheel rotational speed difference correction value [Delta] V 'and the front and rear wheel rotation speed difference detected value [Delta] V front and rear wheel rotational speed difference deadband [Delta] V _OFF.

ΔV ′ = ΔV−ΔV _OFF (where ΔV ′ ≧ 0) In step 103, the unit protection torque TΔV ′ is calculated by the following equation based on the front and rear wheel rotational speed difference correction value ΔV ′.

In TΔV '= K _n · ΔV' step 104, if F1 = 1 or showing a torque transition flag F1 migration completion indicating the transition to unit protection torque TiderutaV clutch torque TiderutaV 'after the different-diameter tires detection is determined .

When F1 = 0, the routine proceeds to step 105, where the clutch torque output value TΔV _OUT is changed to the unit protection torque TΔV ′.
Hereinafter whether it is determined set, while a TΔV _OUT> TΔV ', the process proceeds to step 106, a value obtained by subtracting the set torque T _O from current clutch torque output value TiderutaV _OUT is the next clutch torque output value TiderutaV _OUT Is done.

That is, the clutch torque TΔV is equal to the set torque for each control cycle.
T _O at a time gradually lowered.

When the clutch torque output value TΔV _OUT becomes equal to or less than the unit protection torque TΔV ′ by repeating the torque lowering process of step 106, steps 105 to 107 are performed.
The process proceeds to step 108 where F1 = 0 is rewritten to F1 =
, The unit protection torque TΔV ′ is directly used as the clutch torque output value TΔV _OUT .

Then, the vehicle speed average value describing the driving force distribution acting during running ▲ ▼ When setting value high speed in excess of V _HT, in the different-diameter tires detection processing in step 86 to step 89, set torque x more clutch Whether the different-diameter tire is mounted or not is detected based on whether the torque average value ▼ is continuously applied for 5 minutes or more.

At the time of non-detection of the different-diameter tires, the clutch torque TiderutaV corresponding to the front and rear wheel rotational speed difference detection value ΔV calculated in step 84, is a clutch torque output value TiderutaV _OUT in step 93, depending on the TiderutaV _OUT The wet-type multi-plate clutch 11a is engaged by the applied engaging force (characteristics of FIG. 6 when non-diameter tires are not mounted).

Accordingly, an engine driving force corresponding to the front and rear wheel rotational speed difference detection value ΔV, which is drive wheel slip information, is distributed to the front wheels 10.

On the other hand, at the time of detecting the attachment of the tire having the different diameter, the tire diameter difference Δr is calculated in step 98, and the dead zone ΔV _OFF of the front and rear wheel rotational speed difference is set in step 101.
In 102, a value obtained by subtracting the front and rear wheel rotation speed difference dead zone ΔV _OFF from the front and rear wheel rotation speed difference detection value ΔV is set as a front and rear wheel rotation speed correction value ΔV ′. In Step 103, based on the front and rear wheel rotation speed difference correction value ΔV ′, Unit protection torque TΔ
V 'is determined, and in step 108, this unit protection torque TΔV' is used as the clutch torque output value TΔV _OUT, and the wet multi-plate clutch 11a is engaged with an engagement force corresponding to this TΔV _OUT (the different diameter in FIG. 6). Characteristics when tire attachment is detected).

Therefore, the influence of the difference in front and rear wheel rotation speed due to the different diameter tires on the front wheel 10 side is removed, and the front and rear wheel rotation speed difference correction value ΔV ′ that matches the drive wheel slip information is removed, as in the case where the different diameter tire is not detected. The engine driving force is distributed accordingly.

In the clutch torque transition process of steps 104 to 108, when the unit protection torque TΔV ′ is set, a command for gradually shifting from the clutch torque TΔV before the dead zone setting to the unit protection torque TΔV ′ after the dead zone setting is output. Is done.

As described above, in the driving force distribution control device for a four-wheel drive vehicle of the embodiment, the following effects are exhibited.

During the different-diameter tires detected, driven by the tire diameter difference Δr and the vehicle speed V rear wheel rotational speed difference by subtracting the rear wheel rotational speed difference deadband [Delta] V _OFF corresponding to _i correction value [Delta] V 'from the front and rear wheel rotational speed difference detected value [Delta] V Because it is a device that performs power distribution control,
It is possible to improve the durability of the transfer 11, the differentials 5, 9 and prevent the generation of vibrations and the reduction of fuel consumption without losing the function of the front and rear wheel rotational speed difference control function when detecting the mounting of different diameter tires.

Clutch torque TΔV before and after detecting the attachment of different diameter tires
Is suppressed from suddenly dropping to the unit protection torque TΔV ′, so that it is possible to prevent a sudden change in vehicle listing before and after the detection of the attachment of the different-diameter tire.

Although the embodiment has been described with reference to the drawings, the specific configuration and control contents are not limited to this embodiment.

For example, in the present embodiment, an example of application to a driving force distribution control device of a rear wheel-based four-wheel drive vehicle in which the rear wheel side is directly connected to the engine drive has been described. The present invention can also be applied to a driving force distribution control device for a wheel drive vehicle.

(Effects of the Invention) As described above, according to the first aspect of the present invention, the engine driving force is directly transmitted to one of the front and rear wheels, and the other is transmitted through the torque distribution clutch. In a torque split type four-wheel drive vehicle, when running at high speed where the average vehicle speed exceeds the set value, the abnormal application of different diameter tires is detected due to the continuous application of the clutch torque average exceeding the set torque for the set time. Diameter tire mounting detecting means, when detecting the mounting of different diameter tires, tire diameter difference calculating means for calculating the tire diameter difference based on the average value of the vehicle body speed and the average value of the clutch torque, at the time of non-detection of the mounting of different diameter tires, Outputs to the torque distribution clutch a fastening force command that increases as the front and rear wheel rotation speed difference detection value increases, and when the installation of different diameter tires is detected, the tire diameter difference calculated from the tire diameter difference and the vehicle speed Driving force distribution control means for controlling the engaging force of the torque distribution clutch based on the front and rear wheel rotation speed difference correction value obtained by removing the front and rear wheel rotation speed difference from the front and rear wheel rotation speed difference detection value as in the case of non-detection. The front and rear wheel speed driving force gradually changes the front and rear wheel driving force distribution ratio from the two-wheel drive distribution ratio to the complete four-wheel drive distribution ratio with a higher clutch engagement force as the front and rear wheel rotational speed difference increases. A two-wheel drive-based four-wheel drive vehicle that performs distribution control, which causes a problem when driving at high speed with different-diameter tires while maintaining the drive wheel slip suppression function by the front and rear wheel speed rotation speed difference control. It is possible to prevent the durability from being lowered due to the vertical vibration and the clutch slip and the fuel consumption from being reduced due to unnecessary drive transmission loss.

[Brief description of the drawings]

FIG. 1 is a claim correspondence diagram showing a driving force distribution control device for a four-wheel drive vehicle of the present invention, and FIG. 2 is a diagram of a four-wheel drive vehicle to which the torque split control device (drive force distribution control device) of the embodiment is applied. FIG. 3 is a block diagram showing an electronic control system used in the apparatus of the embodiment, FIG. 4 is a flowchart showing a front and rear wheel driving force distribution control operation, and FIG. 5 is a tire. FIG. 6 is a diagram showing a clutch torque characteristic in the torque split control device of the embodiment, FIG. 7 is a diagram showing a clutch engagement force and a rotational speed difference characteristic with respect to a vehicle speed, and FIG. 8 is a torque split type four-wheel drive. It is a figure showing the running state by car. a: Torque distribution clutch b: Front and rear wheel rotational speed difference detecting means c: Vehicle speed detecting means d: Different diameter tire mounting detecting means e: Tire diameter difference calculating means f: Driving force distribution controlling means

Claims (2)

(57) [Claims] 1. A torque distribution system which is provided in the drive system to the other of the front and rear wheels to the drive system to the other of the front and rear wheels so that the transmitted engine drive force can be changed by external engagement control. And a front and rear wheel rotational speed difference detecting means for detecting a rotational speed difference between front and rear wheels, a vehicle speed detecting means for detecting a vehicle speed, and a clutch torque which is equal to or greater than a set torque when the vehicle is running at a high speed where a vehicle speed average exceeds a set value. Different-diameter tire mounting detecting means for detecting mounting of different-diameter tires by continuously applying the average value for a set time or longer, and detecting tire mounting based on the average vehicle speed and the average clutch torque when detecting the mounting of different-diameter tires. A tire diameter difference calculating means for calculating a diameter difference, and outputting a fastening force command to the torque distribution clutch, which becomes higher as the detected value of the front and rear wheel rotational speed difference becomes larger, when non-detection of a different diameter tire is not detected. At the time of detection of the different-diameter tires,
The torque distribution clutch is used in the same manner as in the non-detection state based on the front and rear wheel rotation speed difference correction value obtained by removing the front and rear wheel rotation speed difference of the tire diameter difference obtained from the tire diameter difference and the vehicle speed from the front and rear wheel rotation speed difference detection value. A driving force distribution control device for a four-wheel drive vehicle, comprising: driving force distribution control means for controlling a fastening force. 2. The driving force distribution control means sets a front and rear wheel rotational speed difference dead zone as the tire diameter difference is large and the vehicle speed is large when detecting the installation of different diameter tires. The driving force distribution control device for a four-wheel drive vehicle according to claim 1, wherein a value obtained by subtracting the dead zone is used as a correction value.