JPH0814294B2 - Driving force distribution control device for four-wheel drive vehicle - Google Patents

Description

The present invention relates to a drive force distribution control device for a four-wheel drive vehicle,
In particular, the present invention relates to an improvement of a drive force distribution control device for a four-wheel drive vehicle that controls the drive force distribution ratio to the front / rear wheels by changing the engagement force of a hydraulic clutch.

(Prior Art) As a conventional driving force distribution control device for a four-wheel drive vehicle, for example, one disclosed in Japanese Patent Application Laid-Open No. 61-275028 is known.

This conventional device is capable of constantly transmitting the driving force from the engine to one wheel (for example, the rear wheel) and also transmitting the driving force to the other wheel via a hydraulic clutch capable of changing the fastening force. When the vehicle is in the elliptical state, the rotation speed N ₂ of the other wheel is corrected by the correction coefficient A which is determined so that the rotation speed difference ΔN between the front and rear wheels becomes zero, and the corrected rotation speed (A・ N ₂ ) and the rotation speed of one wheel
From N ₁ , the rotational speed difference between the front and rear wheels ΔN (ΔN = N ₁ −A ・
N ₂ ) is calculated and the engagement force of the hydraulic clutch is controlled according to the magnitude of ΔN. According to such a configuration, when a tire having different specifications (particularly, a tire diameter related to the number of revolutions) such as a tempered tire is mounted, the front / rear wheel rotational speed difference ΔN caused by the different diameter tires. Can be canceled by calculation, and the engagement force of the hydraulic clutch can be accurately controlled by accurately distinguishing the magnitude of the drive slip and ΔN.

(Problems to be Solved by the Invention) By the way, in the above-described conventional device, the rotational speed difference (ΔN) between the front and rear wheels in the straight elliptic state is set to zero,
Although it is possible to cancel the rotational speed difference due to the different-diameter tires in the calculation, it is excellent in that the driving force distribution control is accurately performed by giving the clutch engagement force according to only the rotational speed difference corresponding to the drive slip. Since the clutch engagement control is performed even when traveling straight at high speed where a difference in rotation speed due to mounting of different-diameter tires is relatively large, heat generation of the hydraulic clutch cannot be ignored, and durability of the hydraulic clutch is improved. There was room for improvement.

Here, the heat generation amount Q of the clutch is calculated by the following equation.

Q = k ・ T ・ ΔN _C ……, where k: clutch control constant T: clutch engagement torque ΔN _C : clutch input / output rotational speed difference ΔNc is ΔN _C = ΔN _C1 + ΔN _C2 ……, where ΔN _C1 : Value generated by slip of driving wheels ΔN _C2 : Value generated by tires with different diameters.

That is, even if the difference in the rotational speed due to the different-diameter tires is canceled as in the conventional device, it merely reduces the command value of T in the formula accompanying the main calculation, and the difference between the friction members of the clutch is , The above ΔN _C2 is always added. Therefore, the heat generation amount Q of the clutch expressed by the above equation
Inevitably, the value of ΔN _C2 is large and the value of Q is large during high-speed running, which is continuously generated, which is not preferable in terms of clutch durability.

Therefore, according to the present invention, if T in the above equation is set to (≈0),
Even if ΔN _C2 occurs due to the different diameter tires, Q (
It is possible to reduce the clutch engagement force to zero or a value close to zero by detecting the mounting of different-diameter tires and reducing the clutch engagement force to zero or a value close to zero during high-speed straight running where heat generation is a problem. The purpose is to suppress heat generation and improve durability.

(Means for Solving the Problems) In order to achieve the above-mentioned object, a drive force distribution control device for a four-wheel drive vehicle according to the present invention has a basic conceptual diagram as shown in FIG. A driving force transmission means capable of transmitting to one wheel and also to the other wheel via a hydraulic clutch, and a control means for controlling the engagement force of the hydraulic clutch are provided, and a different diameter is provided. Different diameter tire detecting means for detecting tire mounting, vehicle speed detecting means for detecting vehicle speed, and straight traveling state detecting means for detecting that the vehicle is in a straight traveling state are provided, and the control means has a different diameter. When the mounting of tires is detected, the vehicle speed is higher than a predetermined value, and the vehicle is traveling straight ahead, the engagement force of the hydraulic clutch is controlled to decrease or become zero.

(Operation) According to the present invention, when the vehicle speed is higher than the predetermined value during traveling with tires having different diameters and the vehicle is in the straight traveling state, the clutch engagement force is controlled to be reduced or zero.
Therefore, even if the difference in rotational speed between the front and rear wheels (ΔN _{C2 in the} previous equation) due to the mounting of different-diameter tires is applied between the friction members of the clutch, the clutch is in the weakly engaged state or in the released state. The amount Q of heat generated can be reduced, and the durability of the clutch can be improved.

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

2 to 5 are diagrams showing a first embodiment of a drive force distribution control device for a four-wheel drive vehicle according to the present invention, and an example applied to a four-wheel drive vehicle based on a front engine rear wheel drive vehicle. Is.

First, the configuration will be described. In FIG. 2, 1 is an engine, 2 is a transmission assembled integrally with the engine 1, and an output shaft 2a of the transmission 2 is
It is connected to a rear wheel propeller shaft 4 and a front wheel propeller shaft 5 via a transfer (driving force transmission means) 3 capable of changing the driving force distribution between the front and rear wheels. The rear wheel propeller shaft 4 is connected to the left and right rear wheels 8a and 8b through the rear wheel differential device 6 and the left and right axles 7a and 7b. Similarly, the front wheel propeller shaft 5 is connected to the front wheel differential. The left and right front wheels 11a, 1 via the device 9 and the left and right axles 10a, 10b
It is linked to 1b.

The transfer 3 has an input shaft connected to the output shaft 2a of the transmission 2 as shown in FIG.
3a and the input shaft 3a, the rear wheel side output shaft 3b connected to the rear wheel propeller shaft 4, the input shaft 3a and the rear wheel side output shaft 3b, and the input shaft 3a and the rear wheel side output. A drum 3c that rotates with the shaft 3b, a plurality of drive plates 3d attached to the inner peripheral surface of the drum 3c, a hollow shaft 3e provided around the input shaft 3a, and a plurality of hollow shafts 3e attached to the outer peripheral surface of the shaft 3e. Driven plate 3f, a drive gear 3g fixed to the hollow shaft 3e, a driven gear 3i that meshes with the drive gear 3g via a counter gear 3h, and a front wheel side output shaft 3j connected to the front wheel propeller shaft 5. Equipped with the drum 3c, drive plate 3d and driven plate
3f constitutes a hydraulic clutch C.

The hydraulic clutch C frictionally engages between the drive plate 3d and the driven plate 3f by supplying the hydraulic pressure P, and transmits the driving force from the engine 1 input to the input shaft 3a to the front wheels 11a and 11b from the front wheel side output shaft 3j. That is, engine 1
The driving force T ₀ from the rear wheel side output shaft 3b is transmitted to the rear wheels 8a and 8b and also to the front wheels 11a and 11b. By changing the hydraulic pressure P, the front wheel side 11a, It is possible to change the amount of driving force transmitted to 11b.
The driving force distribution ratio of the rear wheels can be changed.

In FIG. 2 again, reference numeral 20 denotes a sensor group, and sensor group 20
Is a front wheel rotation sensor 20a that detects the rotation speed Nf on the front wheel side from the rotation speed of the front wheel propeller shaft 5 and the rotation speeds of the front wheels 11a and 11b, and the rotation speed of the rear wheel propeller shaft 4 and the rear wheels 8a and 8a.
The rear wheel rotation sensor 20b that detects the rotation speed Nr on the rear wheel side from the rotation speed of b, the acceleration sensor 20c that detects the lateral acceleration G that acts on the vehicle body, and the steering amount of the steered wheels (for example, the front wheels 11a and 11b). The steering sensor 20d that detects θ and the vehicle speed V (pseudo vehicle speed May be V), a vehicle speed sensor 20e for detecting a throttle opening TH, an opening sensor 20f for detecting a throttle opening TH, and a differential device 9
A front wheel oil temperature sensor 20g for detecting the working oil temperature T _F, wheel side oil temperature sensor 20h after detecting the working oil temperature T _R of the differential 6
And

30 is a control unit as a control unit including the hydraulic pressure supply device 30a, the control unit 30 is configured by, for example, a microcomputer, etc., reads various signals from the sensor group 20,
A predetermined program is executed according to these signals to calculate a control value for determining the amount of the hydraulic pressure P supplied to the transfer 3. The main part of the predetermined program is shown in the flowchart of FIG. In this flowchart,
P ₁ is the step of reading various signals from the sensor group 20, P ₂
Different diameter is the operation state amount of depression of the throttle pedal is not so large compared with the TH and a predetermined value, i.e., the step of determining the operating condition is not a rapid acceleration request, when P ₃ is not abrupt acceleration demand, according to the following equation Tire installation discrimination index value a
(If this a is large, there is a high possibility that a tire with a different diameter is mounted). Here, the different diameter tire is
Temper tires, tires with changed air pressure, tires with different outer diameters, etc., and when some of the four wheels are these tires, other tires with the same specifications, Some of the tires are called different diameter tires.

However, ΔN: Rotational speed difference between front and rear wheels (Nf-Nr) P ₄ compares a obtained by the above equation with a predetermined value a _0, and a> a ₀
When it is, the step of determining that the vehicle is in a traveling state with different diameter tires attached, P ₅ is a step of determining the straight traveling state when G or θ is smaller than a predetermined value, and P ₆ is a step where V is greater than a predetermined value. Is also large, the step of determining high speed running,
P ₇ is a step of determining traveling on a road surface which is not a low μ road when the absolute value of ΔN (| Nf−Nr |) is smaller than a predetermined value, P ₈
If the determination result of the P _2, P ₄ ~P ₇ are all YES instruction,
A step of setting the amount of hydraulic pressure P supplied to the transfer 3 to zero or a slight amount close to zero and calculating a control value for reducing or reducing the amount of torque transmitted to the front wheels, P ₉ is the above P ₂ , P _If any one of the discrimination results of _{4 to} P _{7 is} a NO command, a step of performing the following one.

i) The hydraulic pressure P to the transfer 3 is set so that the amount of torque transmitted to the front wheels according to the rotational speed difference ΔN between the front and rear wheels can be obtained.
Calculating a control value for setting the amount of
Ii) Or, the target value ΔT ₁ (ΔT ₁ = f ₁ (TH)) of the transmission torque to the front wheels according to the throttle opening TH, and the rotation of the front and rear wheels. The sum of the target value ΔT ₂ (ΔT ₂ = f ₂ (ΔN)) of the transmission torque to the front wheels according to the speed difference ΔN (ΔT ₁ + ΔT ₂ ) or the larger value MAX (ΔT ₁ , ΔT ₂ ),
A control value for setting the amount of the hydraulic pressure P to the transfer 3 is calculated according to the obtained value, for example, the control described in Japanese Patent Laid-Open No. 61-183220 is performed. It should be noted that FIG. 5 shows a principle configuration diagram for obtaining the sum (ΔT ₁ + ΔT ₂ ), and FIG. 6 shows MAX (ΔT ₁ ,
A principle configuration diagram for obtaining ΔT ₂ ) is shown.

 Next, the operation will be described.

In this embodiment, when the traveling state of the vehicle corresponds to any one of the following, any one of the normal control (i) and (ii) is performed. That is, when a sudden acceleration is requested, when different-diameter tires are not mounted, when turning, when traveling on low / medium speed, or traveling on a low μ road, the front wheels are in accordance with the rotational speed difference ΔN between the front and rear wheels. The torque transmitted to the side is controlled to be large.

On the other hand, when all of the above conditions (1) to (4) are reversed, that is, when the sudden acceleration is not requested, the different diameter tire is mounted. If all the conditions of straight running, high speed running, and low μ road running are met, the transfer 3
The amount of hydraulic pressure P to zero is set to zero or a small amount close to zero. Therefore, the drive plate 3d of the transfer 3
The frictional coupling force between the driven plate and the driven plate 3f is weakened or released, which occurs due to the mounting of different diameter tires.
Friction heat generation between the drive plate 3d and the driven plate 3f due to the difference in rotation speed of the rear wheels can be suppressed.

As described above, in the present embodiment, the fastening force (T in the previous equation) of the transfer 3 is reduced or zero during high-speed straight running where the amount of heat generated by the hydraulic clutch C poses a problem. Rotation speed difference due to (ΔN in the previous equation
_{Even if C2} ) is generated, the generated heat quantity Q can be set to (≈0), and the effect of improving the durability of the hydraulic clutch C and improving the fuel consumption can be obtained. Further, when the vehicle is traveling in which the generated heat quantity Q does not matter, for example, the steps of the flowchart of FIG.
When any one of P _2, P ₄ ~P ₇ is NO instruction rotational speed difference Δ
Normal control is performed according to N (although there is some noise due to ΔN _C2 ) to ensure starting acceleration and turning stability.

FIG. 6 is a flow chart of a program showing a second embodiment of the driving force distribution control device for a four-wheel drive vehicle according to the present invention.

In FIG. 6, P ₁₁ is a step for determining high speed running when the vehicle speed V is higher than a set value, and P ₁₂ is the hydraulic oil temperature T _F of the front wheel side differential device 9 or the rear wheel side differential device. Step 6 of comparing the hydraulic oil temperature T _{R of} 6 with the set value, and if T _F or T _R is greater than the set value
₁₃ is a step of issuing an alarm to warn the driver when both steps P ₁₁ and P ₁₂ are YES commands, and P ₁₄ is the amount of the hydraulic pressure P supplied to the transfer 3 as in step P ₈ of the first embodiment. Is set to zero or a slight amount close to zero to reduce or reduce the amount of torque transmitted to the front wheels, P ₁₅
Is a step for performing normal control as in step P ₉ of the first embodiment.

With such a configuration, when the hydraulic oil temperatures T _F and T _R of the front wheel-side or rear wheel-side differentials 6 and 9 rise during high-speed traveling, step P ₁₄ is executed and the hydraulic pressure P to the transfer 3 is increased. Is reduced to zero or reduced.

That is, when the hydraulic oil temperatures T _F and T _{R of} the differential devices 6 and 9 rise, especially when the load of the power train system becomes large, for example, tires with different diameters are attached to the front and rear wheels. If the tire pressure is not uniform or the tires wear differently on each wheel, the difference in tire diameter causes a difference in rotational speed (ΔN) between the front and rear wheels. As shown in FIG. 7, the driving torque is applied to one tire (the rear wheel in FIG. 7) having the larger diameter, and the braking torque is applied to the other tire (the front wheel in FIG. 7). Then, in order to maintain the vehicle speed, it is necessary to give an extra drive torque for canceling the braking torque of the other tire, so that the load on the power train system increases correspondingly, and as a result, the differential device 6 , 9
The operating oil temperatures T _F and T _{R of the above} will increase. Therefore,
By monitoring the hydraulic oil temperatures T _F and T _R , it is possible to detect the mounting of the tires of different diameters. At this time, if the fastening force of the transfer 3 is reduced to zero or reduced, the hydraulic clutch C when the tires of different diameters are mounted is detected. Heat generation can be suppressed.

(Effect) According to the present invention, the mounting of the different-diameter tire is detected, and the fastening force of the hydraulic clutch is controlled to zero or a value close to zero when traveling straight at high speed. It is possible to suppress heat generation of the hydraulic clutch due to the difference in front / rear wheel rotation speed due to, and to improve durability.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 6 are diagrams showing a first embodiment of a driving force distribution control device for a four-wheel drive vehicle according to the present invention, and FIG. 2 is a configuration diagram thereof. FIG. 3 is a block diagram of the transfer, FIG. 4 is a flow chart of the control program, and FIGS. 5 and 6 are for obtaining the sum (ΔT ₁ + ΔT ₂ ) of normal control and for obtaining MAX (ΔT ₁ , ΔT ₂ ). FIG. 3 is a principle configuration diagram of each case. 7 and 8 are views showing a second embodiment of the driving force distribution control device for a four-wheel drive vehicle according to the present invention. FIG. 7 is a flow chart of the control program, and FIG. Rear tire diameter <Front tire diameter)
6 is a graph showing driving (braking) torques of front wheels and rear wheels when mounted. C ... Hydraulic clutch, 1 ... Engine, 20e ... Vehicle speed sensor (vehicle speed detecting means), 30 ... Control section (control means, different diameter tire detecting means, straight running state detecting means).

Claims (4)

[Claims] 1. A drive force transmitting means capable of transmitting a drive force of an engine to one of front and rear wheels and also to the other wheel via a hydraulic clutch, and a fastening force of the hydraulic clutch. A vehicle having a different diameter tire detecting means for detecting the mounting of a different diameter tire, a vehicle speed detecting means for detecting a vehicle speed, and a straight running state detection for detecting that the vehicle is in a straight running state. Means, the control means detects the mounting of tires of different diameter, and the vehicle speed is higher than a predetermined value, and if the vehicle is in a straight traveling state,
A drive force distribution control device for a four-wheel drive vehicle, which controls the engagement force of the hydraulic clutch so as to decrease or become zero. 2. The different-diameter tire detecting means includes an oil temperature sensor for detecting a hydraulic oil temperature of a differential device on the front wheel side or the rear wheel side, and the different-diameter tire is detected when the oil temperature is higher than a predetermined value. The driving force distribution control device for a four-wheel drive vehicle according to claim 1, wherein mounting of the vehicle is detected. 3. The different-diameter tire detection means includes an opening sensor for detecting a throttle opening, a front wheel rotation sensor for detecting a front wheel rotation speed (Nf), and a rear wheel for detecting a rear wheel rotation speed (Nr). Including the rotation sensor, the vehicle speed is When the value (a) indicating the ratio of the rotational speed difference between the front and rear wheels (ΔN = Nf−Nr) is larger than a predetermined value (a ₀ ), the mounting of the different diameter tire is detected. 1) A driving force distribution control device for a four-wheel drive vehicle as described above. 4. The driving force distribution control for a four-wheel drive vehicle according to claim 1, wherein an alarm is issued at the same time when the clutch engagement force is controlled to be reduced or reduced to zero. apparatus.