JP2507608B2 - Driving force distribution control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is applied to a front / rear wheel drive force distribution control device for a four-wheel drive vehicle, a drive force distribution control device applied to left / right wheels, front / rear wheel differential limitation control devices, and the like. Regarding the control device.

(Prior Art) Conventionally, as a front-rear wheel driving force distribution control device for a four-wheel drive vehicle, for example, a device described in JP-A-61-275028 is known.

In this conventional source, the rear wheels are engine direct drive wheels,
The front wheel is a clutch engagement drive wheel that transmits the engine drive force via the transfer clutch, and the tire diameter is different in the front and rear wheel drive force distribution control device that increases the drive force distribution to the front wheel side as the difference in front and rear wheel rotation speed increases. When there is a difference between the front and rear wheel rotation speeds due to this, in order to suppress power loss due to oil temperature rise in the power transmission path and internal circulation torque, the front and rear wheel rotation speed difference when the coasting of the vehicle is detected is corrected. A technique for obtaining a control front-rear wheel rotation speed difference is disclosed as.

(Problems to be Solved by the Invention) However, in such a conventional front and rear wheel drive force distribution control device for a four-wheel drive vehicle, the coasting detection of the vehicle is used as the correction condition for the front and rear wheel rotation speed difference. However, there remains a problem that there are very few opportunities to accurately obtain correction values for tires of different diameters.

That is, in the conventional device, coasting of the vehicle is detected by the transmission being in the neutral position, the brake not being operated, and the vehicle being in the straight traveling state.However, in the vehicle equipped with the automatic transmission, it is not possible to set the neutral position during traveling. Even in a vehicle equipped with a manual transmission, it is rare that the straight coasting traveling state continues for a long time during traveling.

The present invention has been made in view of the above problems, and in a drive force distribution control device capable of externally controlling the drive force distribution of the front and rear wheels or the left and right wheels, when a tire with a different diameter is mounted, it can be surely early and reliably. It is an object to suppress power loss due to oil temperature rise and internal circulation torque in the power transmission path section.

(Means for Solving the Problems) In order to solve the above problems, in the driving force distribution control device of the present invention, in order to increase the chances of accurately obtaining a correction value for tires of different diameters, it is during straight running and rotation. The means for correcting the actual rotation speed difference detection value when the speed difference differential value is detected to be small.

That is, as shown in the claim correspondence diagram of FIG. 1, the variable driving force distribution means a capable of controlling the front and rear wheel driving force distribution or the left and right wheel driving force distribution of the engine driving force, and the front and rear wheels or The actual rotational speed difference detecting means b for detecting the actual rotational speed difference between the left and right wheels, the straight traveling detecting means c, and the rotational speed difference differential value detecting means d are in straight traveling and the rotational speed difference differential value is small. The dead band rotational speed difference setting means e for setting the detected value of the actual rotational speed difference when it is detected as the dead band rotational speed difference, and the value obtained by subtracting the dead band rotational speed difference from the actual rotational speed difference are controlled to rotate. It is characterized in that it is provided with a control rotational speed difference calculation means f for determining a speed difference and a driving force distribution control means g for controlling the variable driving force distribution means a based on the control rotational speed difference.

(Operation) When the vehicle is traveling, in the dead zone rotation speed difference setting means e, the straight traveling detection means c and the rotation speed difference differential value detection means d
Thus, the detected value of the actual rotation speed difference when the vehicle is traveling straight and the rotation speed difference differential value is detected to be small is set as the dead zone rotation speed difference, and in the control rotation speed difference calculation means f, A value obtained by subtracting the dead zone rotational speed difference from the actual rotational speed difference detected by the actual rotational speed difference detecting means b for detecting the actual rotational speed difference between the front and rear wheels or the left and right wheels is defined as the control rotational speed difference, and the driving force distribution control means g , A control command is output to the variable driving force distribution means a based on the control rotational speed difference.

Therefore, when traveling with different-diameter tires, when the vehicle is traveling straight ahead and the condition that the differential value of the rotational speed difference is small is satisfied, the dead zone rotational speed difference is immediately obtained, and the elliptic curve is achieved. Compared to the case where the condition is set, the chance of accurately obtaining the correction value for the tires with different diameters is significantly increased.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 2 is an overall system diagram in which the driving force distribution control device of the present invention is applied to a front and rear wheel driving force distribution control device for a four-wheel drive vehicle based on rear wheel drive.

Explaining the configuration, the engine drive system of a four-wheel drive vehicle is
The engine 1, the transmission 2, the rear propeller shaft 3, the rear differential 4, the rear drive shaft 5, the rear wheel 6, the transfer clutch 7, the front propeller shaft 8, the front differential 9, the front drive shaft 10, and the front wheel 11 are provided.

That is, the rear wheels 6 are drive wheels directly coupled to the engine, and the front wheels 11 are clutch engagement drive wheels that transmit the engine drive force via the transfer clutch 7.

The transfer clutch 7 is a clutch having a wet multi-plate friction clutch structure capable of changing the transmission torque (driving force distribution) to the front wheels 11 side by the clutch engagement pressure P _C applied from the outside.

The transfer clutch 7 is provided with, as external devices, a hydraulic control device 20 that produces a clutch engagement pressure P _C and an electronic control device 30 that outputs a command to obtain the clutch engagement portion P _C , and P _C = 0. Is configured so that the driving force distribution to the front wheels 11 is zero and the driving force distribution can be controlled from the rear wheel driving state to the rigid four-wheel driving state in which the driving force distributions of the front and rear wheels 6, 11 are almost equal at P _C = P _MAX. ing.

The hydraulic control device 20 supplies the hydraulic pressure by the pump pressure from the hydraulic pump 21 to the clutch engagement pressure according to the command current value I _C.
A hydraulic control solenoid valve 22 for adjusting the pressure to P _C is provided.

The electronic control unit 30 includes a torque split control unit 31 having an internal circuit such as a microcomputer and a drive circuit, and input information means 32 for obtaining input information necessary for control calculation in the control unit 31. The input information means 32 includes a front wheel speed sensor 33 that detects a front wheel speed Nf, a rear wheel speed sensor 34 that detects a rear wheel speed Nr, a lateral acceleration sensor 35 that detects a lateral acceleration Yg, and a steering wheel that detects a steering angle θ. An angle sensor 36 and the like are provided.

And the torque split control unit
Reference numeral 31 denotes an actual front / rear wheel rotation speed difference calculation unit that calculates an actual front / rear wheel rotation speed difference ΔNreal based on the front wheel speed Nf and the rear wheel speed Mr.
A straight running determination unit that determines whether it is straight running based on the lateral acceleration Yg or the steering angle θ, and a rotation speed difference differential value calculation unit that calculates a rotation speed difference differential value Δ by time differentiation of the actual front and rear wheel rotation speed difference ΔNreal, The dead zone rotational speed difference ΔN ₁ is the actual front / rear wheel rotational speed difference ΔN real when the vehicle is traveling straight ahead and the rotational speed difference differential value Δ is small enough to be regarded as constant speed traveling.
The dead band rotational speed difference setting unit, the control rotational speed difference calculation unit that sets the control front and rear wheel rotational speed difference ΔN to a value obtained by subtracting the dead band rotational speed difference ΔN ₁ from the actual front and rear wheel rotational speed difference ΔNreal, and the control front and rear wheel And a clutch control unit for outputting to the hydraulic control solenoid valve 22 a command current value I _C for obtaining the optimum front wheel side transmission torque T _f based on the rotational speed difference ΔN and the control constant Kt.

 Next, the operation will be described.

FIG. 3 is a flowchart showing the flow of front and rear wheel driving force distribution control operation in the embodiment, and each step will be described below.

In step 40, the dead zone rotational speed difference ΔN ₁ is set to ΔN ₁ = 0 as an initial value.

In step 41, the front wheel speed Nf, the rear wheel speed Nr, the lateral acceleration Yg, and the steering angle θ are read from the sensors 33 to 36.

In step 42, the actual front-rear wheel rotation speed difference ΔNreal is calculated from the front wheel speed Nf and the rear wheel speed Nr by the following formula.

ΔNreal = Nr−Nf At step 43, the rotational speed difference differential value Δ is calculated by the following equation by the time differential of the actual front / rear wheel rotational speed difference ΔNreal.

In step 44, it is determined whether the vehicle is traveling straight ahead.

As a specific example, Yg ≦ Yg ₀ (Yg ₀ is a small threshold value),
In addition, it is determined based on θ ≦ θ ₀ (θ ₀ is a small threshold value) or only one of these conditions.

In step 45, it is determined whether the rotational speed difference differential value Δ is small enough to be regarded as constant speed traveling.

Specifically, it is determined whether or not | Δ | ≦ B (B is a constant having a very small value) is satisfied.

In step 46, it is judged whether or not the control front-rear wheel rotation speed difference ΔN is zero. That is, when .DELTA.N.noteq.0, it means that the rotational speed difference correction by the different-diameter tires is not yet performed, and at this time, the routine proceeds to step 47 and step 48. Further, when ΔN = 0, the rotational speed difference due to the different diameter tires has been corrected, and at this time, the process proceeds to step 49 and the subsequent steps.

In step 47, when the rotational speed difference is corrected by the different diameter tires for the first time, the command current value I _C = 0 for releasing the engagement of the transfer clutch 7 is output in order to prevent the internal circulation torque from being generated quickly.

In step 48, when the conditions in steps 45 to 46 are satisfied, the actual front / rear wheel rotational speed difference ΔNreal is set as the dead zone rotational speed difference ΔN ₁ .

In step 49, the control constant Kt of the driving force distribution with respect to the change in the rotation speed difference is calculated based on the lateral acceleration Yg.

The calculation formula is Kt = f (Yg), and specifically, Kt =
It is calculated by the formula of A / Yg (A; constant).

In step 50, the actual front-rear wheel rotation speed difference ΔNreal obtained in step 42 and the dead rotation speed difference ΔN _{1 set}
The control front / rear wheel rotation speed difference ΔN is calculated from the difference between

In step 51, the front / rear wheel transmission torque T _f is calculated by the following equation based on the control front / rear wheel rotation speed difference ΔN and the control constant Kf, and the front wheel side transmission torque T _f is obtained.
I _C is output to the hydraulic control solenoid valve 22.

T _f = KtΔN, which is represented by the characteristic lines in the characteristic lines of FIGS. 4 and 5.

By performing the front-rear wheel driving force distribution control as described above, the following traveling performance is exhibited.

Different diameter tires with different tire diameters on the front and rear wheels 6, 11 (for example,
When a temper tire is attached to one side or a tire with different air pressure is attached), the vehicle is traveling straight ahead and the rotation speed difference differential value Δ is small, immediately after satisfying the condition. When the transfer clutch 11 is released and the dead zone rotational speed difference ΔN ₁ is set, in the subsequent traveling, the control front / rear wheel rotational speed difference Δ due to the difference between the actual front / rear wheel rotational speed difference ΔNreal and the dead zone rotational speed difference ΔN _1.
Front and rear wheel drive force distribution control is performed based on N.

That is, the front and rear wheel rotation speed difference component caused by the difference in tire diameter is removed from the actual front and rear wheel rotation speed difference ΔNreal,
Control is performed based on the front-rear wheel rotation speed difference caused only by drive wheel slip, and when traveling with tires of different diameters, early suppression of power loss due to oil temperature rise in the power transmission path and internal circulation torque Moreover, it is surely prevented.

In addition, when the front and rear wheel driving force distribution control is performed based on the actual front and rear wheel rotation speed difference ΔNreal when running with different diameter tires, the clutch is always broken due to the difference in rotation speed caused by the different diameter tire. Because the fastening state is maintained,
Internal circulation torque is generated, fuel consumption is reduced due to power loss, and large drive torque or braking torque is generated in the power train system even at constant speed running, as if the acceleration state or strong engine braking state is present for a long time. As a result, the oil temperature in the transfer case or the oil temperature in the rear final drive rises, leading to deterioration of the hydraulic oil and deterioration of the seal.

As described above, the front and rear wheel drive force distribution control device according to the embodiment also has the features listed below.

When the correction condition for the front and rear wheel rotation speed difference is set to the condition that the vehicle is traveling straight and the rotation speed difference differential value ΔN is small, the inertial detection of the vehicle is used as the correction condition for the front and rear wheel rotation speed difference. Compared with the above, the chances of accurately obtaining correction values for different diameter tires are greatly increased, and when installing different diameter tires, it is possible to suppress power loss due to oil temperature rise in the power transmission path section and internal circulation torque early and reliably. it can.

When the condition for correcting the front-rear wheel rotational speed difference is first satisfied, and the correction for the different-diameter tires is not yet performed, the transfer clutch 11 is immediately released, and then the control front-rear wheel rotational speed difference ΔN by the correction. Since the control based on (1) is entered, the generation of the internal circulation torque due to the mounting of the different-diameter tires is performed at an extremely early time immediately after the start of traveling, and the power loss can be effectively suppressed by the internal circulation torque.

The embodiments of the present invention have been described above with reference to the drawings.
The specific configuration and control contents are not limited to this embodiment.

For example, in the embodiment, the example in which the rotational speed difference correction when the tire diameters of the front and rear wheels are different is applied to the front and rear wheel driving force distribution control, but the left and right wheel driving force distribution control is performed when the left and right tire diameters are different. Of course, the same can be applied to.

〔The invention's effect〕

As described above, in the present invention, in the driving force distribution control device capable of externally controlling the driving force distribution of the front and rear wheels or the left and right wheels, in order to increase the chances of accurately obtaining the correction value for the different diameter tires. Since the means for correcting the actual rotational speed difference detection value when the vehicle is traveling straight ahead and the rotational speed difference differential value is detected to be small, power can be transmitted early and reliably when different-diameter tires are installed. It is possible to obtain an effect that it is possible to suppress power loss due to an increase in oil temperature in the path portion and internal circulation torque.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims showing a driving force distribution control device of the present invention, FIG. 2 is an overall system diagram showing a front and rear wheel driving force distribution control device of a four-wheel drive vehicle of an embodiment, and FIG. 3 is an embodiment device. 4 is a flowchart showing the flow of front and rear wheel driving force distribution control operation performed by the torque split control unit in FIG. 4, FIG. 4 is a front wheel side transfer torque characteristic diagram with respect to control front and rear wheel rotation speed difference, and FIG. FIG. 5 is a front wheel side transmission torque characteristic diagram for FIG. a: Variable driving force distribution means b: Actual rotation speed difference detection means c: Straight running detection means d: Rotation speed difference differential value detection means e: Dead zone rotation speed difference setting means f: Control rotation speed difference Computation means g ...... Driving force distribution control means

Claims (1)

(57) [Claims] 1. A variable drive force distribution means capable of controlling front and rear wheel drive force distribution or left and right wheel drive force distribution of engine drive force by an external drive command, and detecting an actual rotational speed difference between the front and rear wheels or left and right wheels. By the actual rotation speed difference detection means, the straight traveling detection means and the rotation speed difference differential value detection means,
Dead zone rotational speed difference setting means for setting the detected value of the actual rotational speed difference when it is detected that the rotational speed difference differential value is small when traveling straight ahead, and the actual rotational speed A control rotation speed difference calculation means for setting a value obtained by subtracting the dead zone rotation speed difference from the difference as a control rotation speed difference, and a driving force distribution control means for controlling the variable driving force distribution means based on the control rotation speed difference. A driving force distribution control device characterized by being provided.