JPH04103433A - Driving force distribution control device for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To improve durability of a transfer and the like and prevent generation of vibration without losing control function against rotating speed difference of front/ rear wheels by correcting a detected value of rotating speed difference of front/rear wheels according to diameter difference of tires and vehicle speed, at detecting mount of different diameter tires, and controlling driving force distribution based on the corrected value. CONSTITUTION:Rotating speed difference of front/rear wheels is detected by a means (b), vehicle speed is detected by a means (c), and mount of different diameter tires is detected by a means (d). At detecting mount of different diameter tires, tire diameter difference is computed by a means (e). At no detecting of mount of different diameter tires, a coupling force command according to the detected value of front/rear wheel rotating speed difference is output to a torque distributing clutch (a), and at detecting mount of different diameter tires, the coupling force of the clutch (a) is controlled by a means (f) due to corrected speed difference according to the tire diameter difference and the vehicle speed. Hence at detecting mount of different diameter tires, without losing the control function against rotating speed difference, improving durability of a transfer or differential, preventing vibration, and preventing deterioration of fuel consumption is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a drive force distribution control device for a four-wheel drive vehicle in which drive force distribution between the front and rear wheels can be changed, and particularly to a measure for installing different diameter tires on the front and rear wheels.

(Prior Art) Conventionally, as a driving force distribution control device for a four-wheel drive vehicle, for example, as described in Japanese Patent Laid-Open No. 133-1981, There is a known device that increases or decreases the clutch engagement force based on the detected speed difference value and changes the distribution of the engine driving force between the front and rear wheels.This device suppresses drive wheel slip while taking advantage of the maneuverability that is the hallmark of rear-wheel drive vehicles. In order to improve drive performance, the relationship between front and rear wheel rotational speed difference (rear wheel - front wheel) and clutch engagement force (front wheel drive torque) is determined. The setting is such that the front wheel drive torque increases as the speed difference increases, and the control is such that the difference in rotational speed between the front and rear wheels is always reduced to zero.

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

That is, as shown in FIG. 7, the detected value of the rotational speed difference between the front and rear wheels is
vw is the difference in rotational speed between the front and rear wheels due to drive wheel slip △v5
(tends to decrease due to clutch engagement) is output as the sum of the rotational speed difference △vT due to different tire diameters between the front and rear wheels, which increases as the vehicle speed increases regardless of clutch engagement, and the clutch increases in accordance with vehicle speed. Fastening forces T and J□ are applied.

As a result, unpleasant vertical vibrations (
(pulling vibration) or clutch slippage (=△V5
+ΔV, ) causes problems such as increased oil temperature in the transfer and differential due to intense heat generation, resulting in decreased durability and worsened fuel efficiency.

In addition, the causes of the front and rear tires having different diameters include when tempered tires are installed, when they wear unevenly, when the tire air pressure is different, and when the wheel load changes due to an increase or decrease in the number of passengers.
If you look at the tire diameters when driving, they are more or less different diameters.

In addition, the unpleasant vibrations during high-speed driving were confirmed through experiments, and although the cause is not clear, at least it is not due to fluctuations in clutch engagement force, but rather due to different tire diameters between the front and rear wheels, as shown in Figure 8. If the front and rear wheels, which have a large rotational speed difference and are forced to slip and run together due to the rotational speed difference, are considered to cause some sort of resonance phenomenon in the drive system.

The present invention was made with attention to the above-mentioned problems, and the present invention directly transmits engine driving force to one of the front and rear wheels.
On the other hand, in four-wheel drive vehicles with a torque split system that transmits torque through a torque distribution clutch, it is possible to improve the durability of transfers and differentials without losing the ability to control the difference in rotational speed between the front and rear wheels when different diameter tires are detected. The goal is to prevent vibrations and reduce fuel consumption.

(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 of the present invention, when detecting the installation of tires with different diameters, the tire diameter is The device performs driving force distribution control based on the difference in rotational speed between the front and rear wheels, which is corrected according to the difference and vehicle speed.

In other words, as shown in the complaint response diagram in Figure 1, a drive system that connects the engine directly to one of the front and rear wheels is installed midway through the drive system to the other of the front and rear wheels, and the engine driving force to be transmitted is transferred from the outside. A torque distribution clutch a that can be changed by fastening force control, front and rear wheel rotation speed difference detection means for detecting the rotation speed difference between the front and rear wheels, and vehicle speed detection means C for detecting the vehicle speed.
A different diameter tire attachment detection means d detects the attachment of a different diameter tire, a tire diameter difference calculation means e calculates a tire diameter difference when the attachment of a different diameter tire is detected, and a front and rear wheel rotation speed when the attachment of a different diameter tire is not detected. A fastening force command corresponding to the detected difference value is output to the torque distribution clutch a, and when installation of tires with different diameters is detected, the torque distribution is performed based on the tire diameter difference and the front and rear wheel rotational speed difference corrected according to the vehicle speed. The driving force distribution control means f controls the engagement force of the clutch a.

(Function) When driving at high speed, the different diameter tire mounting detection means d
For example, whether a different diameter tire is installed or not is detected based on whether a clutch torque of a predetermined value or more is continuously applied for a predetermined time or more.

When installation of a different diameter tire is not detected, the driving force distribution control means 9
At this time, a fastening force command corresponding to the front and rear wheel rotational speed difference detection value detected by the front and rear wheel rotational speed difference detection means is output, and the torque distribution clutch a is engaged.

Therefore, the engine driving force is distributed to the clutch-engaged drive wheel side in accordance with the detected value of the front and rear wheel rotational speed difference, which is the drive wheel slip information.

On the other hand, when detecting the installation of a different diameter tire, the tire diameter difference calculation means e calculates the tire diameter difference, and the vehicle speed detection means C detects the vehicle speed.

Then, in the driving force distribution control means f, the front and rear wheel rotational speed difference detection value detected by the front and rear wheel rotational speed difference detection means is corrected according to the tire diameter difference and the vehicle speed, and the front and rear wheel rotational speed difference detection value is corrected according to the tire diameter difference and the vehicle speed. A corresponding fastening force command is output, and the torque distribution clutch a is fastened.

Therefore, the detection value of the front and rear wheel rotation speed difference due to the different diameter tires is removed from the clutch engagement drive wheel side, and the front and rear wheel rotation speed difference correction value matches the drive wheel slip information, as in the case of non-detection of the installation of the different diameter tires. Engine driving force is distributed accordingly.

(Example) Embodiments of the present invention will be described below based on the drawings.

Figure 2 shows the torque split control system of a four-wheel drive vehicle (
1 is an overall system diagram including a drive system in which a driving force distribution control device (driving force distribution control device) is used; first, the configuration will be explained.

The vehicle to which the torque split control system of the embodiment is applied is a rear-wheel-based four-wheel drive vehicle, and its drive system includes an engine 1. Transmission 2゜Transfer input shaft 3
．． Rear propeller shaft 4, rear differential 5
．． Rear wheel 6. Transfer output shaft7. Front propeller shaft 8° Front differential 9. The engine driving force that has passed through the transmission 2 is directly transmitted to the rear wheels 6, and the front wheels 10 are provided with a transfer 11 provided between the transfer input and output shafts 3 and 7 of the front wheel drive system. transmitted via.

The torque split control system that optimally controls the distribution of driving force between the front and rear wheels while achieving both driving performance and steering performance is based on the transfer 11 (for example, Showa 63-32
(see the specification and drawings of No. 5379) and a control hydraulic pressure generating device 20 that generates a control hydraulic pressure Pc that becomes a clutch engagement force.
and a torque split controller 40 that outputs a predetermined dither current of 1° to the solenoid valve 28 provided in the control oil pressure generator 20 based on information from various human power sensors 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 to draw water from a reservoir tank 23, and a pump discharge pressure (-sinking pressure) from the hydraulic pump 24. an accumulator 26 for accumulating oil via a check valve 25, and a solenoid for adjusting the line pressure (secondary pressure) from the accumulator 26 to a predetermined control oil pressure Pc from a solenoid-driven dither current i from a torque split control section 40. The hydraulic fluid of the control hydraulic pressure Pc is supplied to the clutch port via a control hydraulic vibrator 29.

As shown in the block diagram of the system electronic control system in FIG. 3, the various input sensors 30 include a left front wheel rotation sensor 30a, a right front wheel rotation sensor 30b, and a left rear wheel rotation sensor 3.
0C1 right rear wheel rotation sensor 30d, first lateral acceleration sensor 3
0e, and a second lateral acceleration sensor 30f.

As shown in the system electronic control system block diagram of FIG. Arithmetic circuit 40d, front wheel speed computing circuit 40
e, rear wheel speed calculation circuit 40f, rotational speed difference calculation circuit 409
．． Fastening force calculation circuit 40h, T-i conversion circuit 401. dither current output circuit 40j, lateral acceleration calculation circuit 402. Gain calculation circuit 40m, different diameter tire mounting detection circuit 40n,
It has a tire diameter difference calculation circuit 40p1, a front and rear wheel rotational speed difference dead zone setting circuit 40q, and a failsafe circuit 40r.

In addition, in the figure, A/D is an A/D converter, D/Al; ltD/
It is an A converter.

Further, a warning lamp 50 is connected to the failsafe circuit 40r.

Next, the effect will be explained.

FIG. 4 is a flowchart showing the flow of the front and rear wheel drive force distribution control operation performed by the torque split controller 40, and each step will be explained in turn below.

In step 80, the left front wheel speed is changed to the right front wheel speed VWFRI.
Left rear wheel speed vW RL + right rear wheel speed VW RR + first lateral acceleration Y67. Second lateral acceleration YG2 is input.

In step 81, as input processing, the left front wheel speed VW
Front wheel speed VW is determined by the average value of FL and right front wheel speed VWFFI.
F is calculated, and the above left rear wheel speed VWRL and right rear wheel speed VWR are calculated.
The rear wheel speed VWR is calculated from the average value of the first lateral acceleration Y61 and the second lateral acceleration YG2, and the lateral acceleration Y is calculated from the average value of the first lateral acceleration Y61 and the second lateral acceleration YG2. is calculated, and the front wheel speed VWF becomes the vehicle speed V
, is set as .

In step 82, a detected value Δv(−vwR−vWF) of the front and rear wheel rotation speed difference is calculated from the front wheel speed VWF and the rear wheel speed VWR.
ΔV≧O) is calculated.

In step 83, the clutch torque output value TAV is determined with respect to the detected value ΔV of the rotational speed difference between the front and rear wheels or the correction value ΔV° of the rotational speed difference between the front and rear wheels. The control gain of the U-engine is calculated by the following formula based on the reciprocal of the detected lateral acceleration value Y6.

Kh=ah/Ya (however, g≦βh) For example, let O□=1 and B=1o.

In step 84, the clutch torque TΔV is calculated based on the control gain and the detected value ΔV of the rotational speed difference between the front and rear wheels.

In step 85, it is determined whether the different diameter tire mounting detection flag FS3 is FS3=1, which indicates that the mounting of a different diameter tire is detected, or FS3.0, which indicates that the mounting of a different diameter tire is not detected.

If FS3=O, then in steps 86 to 90, detection processing for mounting a different diameter tire is performed.

That is, in step 86, the clutch torque average value TΔV
and vehicle body speed average value V are calculated by a periodic average of 5 seconds, and in step 87, clutch torque average value TΔV
exceeds the set value ×, and the vehicle body speed average value V1 exceeds the set value V
It is determined whether the HT is exceeded. If YES in step 87, the high clutch torque determination flag (ITFLG) is set to 1 in step 88, and it is determined in step 89 whether HTFLG=1 continues for 5 minutes. In other words, if a state in which both the high clutch torque condition and the high vehicle speed condition are satisfied at the same time occurs continuously for more than 5 minutes, which is impossible during normal acceleration driving, it is detected that a different diameter tire is installed, and step 90 is performed. The different diameter tire attachment detection flag FS3 is rewritten to FS3=1 indicating that different diameter tire attachment has been detected.

On the other hand, if the condition in step 8a is not satisfied, the high clutch torque determination flag HTFLG is set to HT in step 91.
FLG=O, and in step 92 the different diameter tire installation detection flag FS3 is set as FS3=O, and in step 89
Even when the continuity condition is not satisfied, the different diameter tire mounting lateral ratio flag FS3 is set to FS3=0 in step 92.

Then, if installation of a different diameter tire is not detected, step 93
, the clutch torque T determined in step 84
AV is set as the clutch torque output value TΔVOLI, and in step 94, the clutch torque output value T6V is set based on the Ti characteristic table given in advance. u
l is converted into the obtained solenoid drive current l, and in step 95, a dither is applied to the solenoid valve 28.
A current (for example, l±O, IA +0OHz) is applied.

When it is detected that a tire with a different diameter is attached, the flow is from step 90 to step 96 and subsequent steps.

In step 96, in response to the lateral ratio of the different diameter tire installed in step 90, the warning lamp 50 is blinked to inform the driver that the different diameter tire is being installed.

In step 97, it is determined whether the detected value △V of the difference in rotational speed between the front and rear wheels is positive or negative. If △V<0 and the difference in rotational speed between the front and rear wheels is not caused by drive wheel slip, step 93 The subsequent deceleration-side normal control is performed.

In step 98, the tire diameter difference Δr is searched from the map shown in FIG. 5 based on the vehicle speed average value v1 and the clutch torque average value TΔV.

Note that this map shows that when the average vehicle speed value V is small and the average clutch torque value T△V is large, the tire diameter difference △r
is large, and in the opposite case, the tire diameter difference Δr is small, so it is set by calculation or experiment.

In step 99 and step 100, the gain is set for the dead zone ΔVOFF for the rotational speed difference between the front and rear axes. FF is calculated by the following formula based on the detected lateral acceleration value Y6 and the tire diameter difference Δr.

s=a+/ya (however, when Ya=O, 8-81)
To. 2. = to 1・Δr, that is, to the set gain. 1. is set to a smaller value as the detected lateral acceleration value Y6 is larger, and is set to a larger value as the tire diameter difference Δr is larger.

In step 101, the front and rear axle rotational speed difference dead zone 8 VOF
F is the setting gain. It is calculated using the following formula using the FF and the vehicle speed V.

8VOFF''OFF' Vi In step 10, the front and rear wheel rotational speed difference correction value ΔV' is calculated by the following formula using the front and rear wheel rotational speed difference detected value ΔV and the front and rear wheel rotational speed difference dead zone ΔVOFF.

△V = △V - F to 8 VO (However, △V゛≧0) In step 103, the unit protection torque TΔV′ is calculated based on the front and rear wheel rotational speed difference correction value △V′ using the following formula.

TΔv′2.・△V゛In step j04, after the attachment of a different diameter tire is detected, the unit protection torque TΔV of the clutch torque IIV is applied.

It is determined whether the torque transfer flag F1 indicating the transition to is E1=1 indicating the completion of the transition.

Then, when F1=0, the process advances to step 105, and the clutch torque output value TΔVOUT is set to the unit protection torque T.
It is determined whether TΔVo−v > TΔ
V", the process proceeds to step 106, and the value obtained by subtracting the set torque To from the current clutch torque output value TΔVOLIT is the next clutch torque output value TΔVOU□
is set.

That is, the clutch torque TΔV is the set torque ■ for each control cycle. gradually lowered.

When the clutch torque output value TΔVOLI7 becomes equal to or less than the unit protection torque TΔV'' by repeating the torque reduction process in step 106, the process proceeds from step 105 to step 107, where F1=O is rewritten to F1=1, and in step 108, Unit protection torque TΔV
° remains below the clutch torque output value V. It is said to be a U-engineer.

Next, the driving force distribution effect during running will be explained.

During high-speed driving where the vehicle body speed average value V exceeds the set value Vl-IT, in the different diameter tire mounting detection processing in steps 86 to 89, is the clutch torque average value TΔV greater than or equal to the set torque X continuously applied for 5 minutes or more? The pressure is measured depending on whether a different diameter tire is installed or not.

Then, if installation of a different diameter tire is not detected, step 84
The clutch torque TΔV corresponding to the front and rear rotational speed difference detection value ΔV obtained in step 93 is set as the clutch torque output value TΔVOLIT, and the wet multi-disc clutch 11a is engaged with the engagement force according to this TΔVOUT ( (Characteristics when different diameter tires are not detected in Figure 6).

Therefore, engine driving force is distributed to the front wheels 10 according to the detected value ΔV of the front and rear wheel rotational speed difference, which is drive wheel slip information.

On the other hand, when detecting the installation of tires with different diameters, the tire diameter difference Δr is calculated in step 98, the front and rear wheel rotation speed difference dead zone ΔVOFF is set in step 101, and the front and rear wheels are The value obtained by subtracting the rotational speed difference dead zone AVoFF is set as the front and rear wheel rotational speed difference correction value △V. In step 103, the unit protection torque TΔV' is determined based on the front and rear wheel rotational speed difference correction value △V°, and in step 108 This unit protection torque T△V° is set as the clutch torque output value T△Vou□, and the wet multi-disc clutch 1+a is engaged with the engagement force according to this T△Vo and JT (6th
Characteristics when detecting installation of different diameter tires (see figure).

Therefore, on the front wheel 10 side, the detected value of the difference in rotational speed between the front and rear wheels due to the different diameter tires is removed, and the correction value △V of the difference in rotational speed between the front and rear wheels matches the driving wheel slip information, as in the case when the different diameter tires are not detected. The carrot driving force is distributed accordingly.

Note that in the clutch torque transition process from step 104 to step 108, when the unit protection torque TΔV is set, a command is issued to gradually shift from the clutch torque TΔV before the dead zone is set to the unit protection torque TΔV' after the dead zone is set. Output.

As explained above, the driving force distribution control device for a four-wheel drive vehicle according to the embodiment exhibits the effects listed below.

■ When detecting the installation of different diameter tires, a front and rear wheel rotational speed difference correction value △V is obtained by subtracting the front and rear wheel rotational speed difference detection means VOFF according to the tire diameter difference Δr and the vehicle speed V from the front and rear wheel rotational speed difference detection value △V. ', the device controls the drive force distribution, without losing the function of controlling the rotation speed difference between the front and rear wheels when detecting the installation of different diameter tires, improving the durability of the transfer 11 and differential 5°9, preventing vibration generation, and improving fuel efficiency. It is possible to prevent the decrease.

■ Clutch torque T△ before and after detecting installation of different diameter tires
Since the sudden drop in the unit protection torque TΔV' is suppressed, it is possible to prevent sudden changes in vehicle behavior before and after the installation of a different diameter tire is detected.

Although the embodiment has been described above based on the drawings, the specific configuration and control contents are not limited to this embodiment.

For example, in the embodiment, an example of application to a driving force distribution control system for a rear-wheel-based four-wheel drive vehicle in which the rear wheels are directly connected to the engine drive was shown, but a front-wheel-based four-wheel drive vehicle in which the front wheels are directly connected to the engine drive was shown. It can also be applied to drive force distribution control devices for wheel drive vehicles.

(Effects of the Invention) As explained above, in the present invention according to claim 1, engine driving force is directly transmitted to one of the front and rear wheels, and transmitted to the other through a torque distribution clutch. In a torque split type four-wheel drive vehicle, when different diameter tires are detected, the detected value of the difference in rotational speed between the front and rear wheels is corrected according to the tire diameter difference and the vehicle speed, and this correction value is used to control the drive force distribution. Therefore, it is possible to improve the durability of the transfer and differential, prevent the generation of vibration, and prevent a decrease in fuel efficiency without losing the function of controlling the front and rear wheel rotational speed differences when pressure testing is carried out when tires with different diameters are installed.

[Brief explanation of drawings]

FIG. 1 is a complaint diagram showing a driving force distribution control device for a four-wheel drive vehicle according to the present invention, and FIG. 2 is a diagram showing a drive force distribution control device for a four-wheel drive vehicle according to an embodiment of the present invention. Fig. 3 is a block diagram showing the electronic control system used in the embodiment device, Fig. 4 is a flowchart showing the front and rear wheel drive force distribution control operation, and Fig. 5 is a diagram showing the tire diameter. Difference map diagram, Figure 6 is a clutch torque characteristic diagram in the torque split control device of the embodiment, Figure 7 is a clutch engagement force and rotational speed difference characteristic diagram with respect to vehicle speed, and Figure 8 is a torque split type four-wheel drive vehicle. FIG. a... Torque distribution clutch b... Front and rear wheel rotational speed difference detection means C... Vehicle speed detection means d... Different diameter tire installation detection means e... Tire diameter difference calculation means f... Drive Force distribution control means Fig. 5 (Different tire arrangement @ + surplus) Front and rear wheel rotational speed difference correction 1 - ΔV Fig. 7 Fig. 8 Braking force drive blade

Claims (1)

[Scope of Claims] 1) A drive system that is directly connected to the engine to one of the front and rear wheels is provided in the middle of the drive system to the other of the front and rear wheels, and the transmitted engine drive force can be changed by external fastening force control. a torque distribution clutch, a front and rear wheel rotational speed difference detection means for detecting a rotational speed difference between the front and rear wheels, a vehicle speed detection means for detecting vehicle speed, a different diameter tire attachment detection means for detecting attachment of a different diameter tire, tire diameter difference calculating means for calculating a tire diameter difference when mounting of a different diameter tire is detected, and outputting a fastening force command according to the difference in rotational speed of the front and rear wheels to the torque distribution clutch when mounting of a different diameter tire is not detected; A driving force distribution control means for controlling the engagement force of the torque distribution clutch based on the difference in rotational speed between the front and rear wheels corrected according to the difference in tire diameter and the vehicle speed when detecting the installation of a different diameter tire. A driving force distribution control device for four-wheel drive vehicles. 2) When detecting the installation of tires with different diameters, the driving force distribution control means sets a larger dead zone for the front and rear wheel rotational speed difference as the tire diameter difference is larger and the vehicle speed is higher, and determines the dead zone from the detected value of the front and rear wheel rotational speed difference. The driving force distribution control device for a four-wheel drive vehicle according to claim 1, wherein the subtracted value is used as the correction value.