JPH01190537A - Driving force distribution control device for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To improve control accuracy by continuously distributing driving force according to a rotating speed difference between front and rear wheels and lateral acceleration of a vehicle at the time of turning running and increasing or decreasing the initial connecting force of a clutch according to a car velocity when the rotating speed difference at the time of rectilinear running is small. CONSTITUTION:A transfer A for distributing engine driving force to front and rear wheels includes a clutch B for connecting front and rear wheel sides, and the connecting force of the clutch is controlled according to the running status of a vehicle. In this case, the lateral acceleration of a vehicle detected by means C is compared with a reference value for judging the rectilinear running of the vehicle or the turning running thereof by means D. When the lateral acceleration is above the reference value, the connecting force of the clutch is changed according to a rotating speed difference between front and rear wheels, detected by means E and the lateral acceleration by means F. On the contrary, when the lateral acceleration is under the reference value, for example, when the rotating speed difference is small, within a designated range, the initial connecting force increased or decreased according to the car velocity detected by means G is generated in the clutch by means H.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a driving force distribution control device for a four-wheel drive vehicle equipped with a transfer capable of controlling the driving force distribution ratio between front and rear wheels.

[Conventional technology]

Conventionally, as a driving force distribution control device for a four-wheel drive vehicle, the one described in, for example, Japanese Patent Laid-Open No. 57-80926 is known.

This device includes a detection means for individually detecting the rotation speed of the front wheels and rear wheels, and a detection means for detecting the rotation speed of the front wheels.

Comparing means for comparing the detected rotational speed values of the rear wheels, and instruction means capable of instructing switching from two-wheel drive to four-wheel drive based on the comparison result of the comparison means, and the rotational speed difference between the front wheels and the rear wheels is When the value exceeds a predetermined value, an instruction is given to switch to four-wheel drive.

However, with this type of control method, the switching from two-wheel drive to four-wheel drive is carried out in steps, so the steering characteristics change suddenly when turning, for example, and the control is rough and does not always provide the optimal control depending on the driving situation. Drive force distribution could not be obtained.

Therefore, in Japanese Patent Application No. 61-109868, the present applicant has made a proposal aimed at solving the above-mentioned problems and further ensuring straight running stability. In other words,
The device according to this proposal includes a rotational speed difference detection means for detecting the rotational speed difference between the front and rear wheels, and generates a predetermined initial engagement force in the clutch in a predetermined region where the rotational speed difference is small, and The clutch control means continuously increases the engagement force of the clutch in accordance with an increase in the rotational speed difference when the rotational speed difference is outside a predetermined range.

Therefore, according to the device according to this prior application, when driving straight at high speed on a high friction coefficient road with a small difference in rotational speed, the initial engagement force of the clutch increases the distribution of driving force to the front wheels (or rear wheels). It was close to wheel drive, which ensured straight-line stability.

[Problem to be solved by the invention]

However, in this previous device, the clutch always generated a constant value of initial engagement force while driving in a specified region where the rotational speed difference between the front and rear wheels was small, so the initial engagement force was high. In this case, for example, when turning on a road with a high friction coefficient such as a dry asphalt road, the driving torque corresponding to the initial engagement force is transmitted via the clutch, so the torque distribution on the engaged side becomes too large, which causes the steering characteristics to deteriorate. There were unresolved issues such as a tendency for the system to drift out.

On the other hand, in this case, it is easily assumed that the initial fastening force is set low in advance.

However, in this case, when turning on a high-μ road, the control characteristics based on the rotational speed difference ΔN and the clutch transmission torque ΔT make it possible to adjust the steering characteristics by controlling the vehicle's yaw; There was a contradictory problem: a lack of stability when driving.

This invention was made in view of these unresolved problems, and provides a four-wheel vehicle that can accurately balance stability during high-speed straight running and improved steering characteristics when turning with high lateral acceleration. The object of the present invention is to provide a driving force distribution control device for a driving vehicle.

[Means to solve the problem]

In order to achieve the above object, the present invention is provided with a transfer that distributes the engine driving force to the front and rear wheels as shown in FIG. In a drive force distribution control device for a four-wheel drive vehicle, the drive force distribution control device has a clutch that engages the front and rear wheels, and commands the engagement force according to the vehicle running conditions. a speed difference detection means, a lateral acceleration detection means for detecting lateral acceleration generated in the lateral direction of the vehicle, a heavy speed detection means for detecting the vehicle speed, and a speed difference detection means for detecting the lateral acceleration generated in the lateral direction of the vehicle; a comparison means for comparing with a reference value set to be able to discriminate whether the vehicle is running; and when the comparison means determines that the lateral acceleration is greater than or equal to the reference value, the comparison means is configured to perform a comparison according to the rotational speed difference and the lateral acceleration; When the first clutch control means for changing the engagement force of the clutch and the comparison means compare and determine that the lateral acceleration is less than a reference value, when the rotational speed difference is within a small predetermined range, the vehicle speed is a second clutch control means that causes the clutch to generate an initial engagement force that increases or decreases depending on the rotational speed difference, and that changes the engagement force of the clutch in accordance with the rotational speed difference when the rotational speed difference is outside the predetermined range; It is equipped with

[Effect]

In this invention, the rotational speed difference between the front and rear wheels is detected by the front and rear wheel rotational speed difference detection means, the lateral acceleration is detected by the lateral acceleration detection means, and the vehicle speed is detected by the vehicle speed detection means. Then, the comparison means compares and determines whether or not the detected lateral acceleration is equal to or greater than a reference value, thereby determining whether the vehicle is traveling straight ahead, traveling close to it, or turning. Therefore, the first
The clutch control means changes the engagement force of the clutch according to the rotational speed difference and the lateral acceleration when the comparison means determines that the lateral acceleration is equal to or higher than a reference value corresponding to cornering. Control steering characteristics. moreover,
When the detected lateral acceleration is compared and determined to be a value less than a reference value corresponding to straight-ahead traveling or nearly straight-ahead traveling, the second clutch control means is configured to control the second clutch control means when the rotational speed difference is within a predetermined range where the rotational speed difference is small. The clutch generates an initial engagement force that increases or decreases depending on the detected vehicle speed value, and when the rotational speed difference is outside a predetermined range, the clutch engagement force is changed according to the rotational speed difference. ensure good straight-line stability.

〔Example〕

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

FIG. 2 to FIG. 8 are diagrams showing an embodiment of the present invention. This embodiment shows a case in which the FR (front engine, rear drive) system is applied to a part-time four-wheel drive vehicle.

In Fig. 2, ■ is the engine, 2FL to 2RR are the front to rear right wheels, 3 is a drive power transmission system that can change the driving force distribution ratio to the wheels 2FL to 2RR, and 4 is the drive by the drive power transmission system 3. A driving force distribution control device that controls force distribution is shown.

Of these, the driving force transmission system 3 includes a clutch 10 that connects and disconnects the driving force from the engine 1, a transmission I2 that changes the output of this clutch 10 at a selected gear ratio, and this transmission I2.
Drive force from 2 to the front wheels 2PL.

2PR side and rear wheels (permanently driven) 2RL, 211
It has a transfer 14 that divides into the R side. In the driving force transmission system 3, the front wheel driving force divided by the transfer 14 is transferred to the front wheel output shaft 16, the front differential gear 18, and the front wheel drive shirt L-.
Front wheel 2FL, 2FI through 20? On the other hand, the rear wheel driving force is transmitted to the propeller shaft (rear wheel output shaft).
22, is transmitted to the rear wheels 2RL and 2RR via the rear differential gear 24 and the rear wheel side drive shaft 26.

The transfer 14 is constructed as shown in FIGS. 3 and 4. That is, in FIG. 3, 28 indicates a transfer case, and an input shaft 30 connected to the output side of the transmission 12 is inserted into the transfer case 28, and this input shaft 30 is rotatably supported by a bearing 31 or the like. It is pivoted. Further, the right end side of the input shaft 30 in FIG. 3 is connected to an output shaft 33 which is connected to the propeller shaft 22 and rotatably supported by a bearing 32. Here, 30A is an oil passage, 34 is a joint flange spline-coupled to the output shaft 33, 35 is an oil seal, and 36 is a speedometer pinion.

On the other hand, at the center of the input shaft 30, as shown in the figure, a wet multi-disc clutch 37 is provided which can change the torque distribution ratio between the front and rear wheels. This clutch 37 is connected to the input shaft 3
A clutch drum 37a spline-coupled to 0, a friction plate 37b rotationally engaged with the clutch drum 37a, and a clutch hub rotatably supported on the outer periphery of the input shaft 30 by a needle hair ring 38. 37c, a friction disk 37d that is rotationally engaged with the clutch hub 37c, a clutch piston 37e disposed on the right side of the clutch 37 in FIG. 3, and a friction disk 37e formed between the clutch piston 37e and the clutch drum 37a. and a cylinder chamber 37f. Moreover, in this clutch 37, 37g
is a dish plate, and 37h is a return spring for the clutch piston 37e.

The clutch 37 is also connected to the front wheels via a gear train mounted on the left end side of FIG. 3 as shown. That is, the clutch hub 37c
0A and 40B are spline-coupled to a rotatable first gear 41A, and this first gear 41A is meshed with a rotatable second gear 41B by a bearing 42.43, and this second gear 41B is It is connected to the aforementioned front wheel side output shaft 16 via a third gear 41C (see FIG. 4).

Furthermore, an input port 46 is provided at a predetermined position on the side surface of the transfer case 28 to which hydraulic pressure (command force) is supplied from a hydraulic pressure supply mechanism to be described later. The input port 46 communicates with the cylinder chamber 37f via an oil passage 47 formed inside the transfer case 28 and the clutch drum 37a as shown.

Therefore, when no oil is supplied to the input port 46, the pressure in the cylinder chamber 37f of the clutch 37 is zero, so the spring force of the return spring 37h causes the friction plate 37b and the friction disc 37 to
d are spaced apart.

Therefore, in this state, all of the input torque transmitted to the input shaft 30 is transferred to the output shaft 33. The power is transmitted to the rear wheels via the propeller shaft 22, resulting in a two-wheel drive state. On the other hand, when oil is supplied to the input port 46, the clutch piston 3
7e is generated, and in response, a fastening force due to frictional force is generated between the friction plate 37b and the friction disk 37d, and as a result, part of the total drive torque is transferred through the output shaft 16. It is also transmitted to the front wheels. The relationship between the torque ΔT transmitted to the front wheels and the oil pressure P is as follows: ΔT=P-8·2n·μ·ro. Here, S is the pressure acting area of the piston 37e,
n is the number of friction disks, μ is the friction coefficient of the clutch plate, and r is the effective torque transmission radius of the friction disk.

In other words, the transmission torque ΔT is proportional to the oil pressure P (see FIG. 6), and as a result, the driving torque is distributed and transmitted to the rear wheels and the front wheels according to the fastening force. The torque distribution ratio between the front and rear wheels can be continuously changed from rO: 100 J to r50: 50 J depending on the pressure P of the hydraulic oil supplied to the input port 46.

On the other hand, returning to FIG. 2, the driving force distribution control device 4 includes the transfer 14, a hydraulic pressure supply mechanism 50 that supplies hydraulic oil to the input boat 46 of the friction clutch 37 of the transfer 14, and a vehicle speed sensor 52. Front wheel rotation sensor 54, rear wheel rotation sensor 56, and lateral acceleration sensor 57
and a controller 58.

As shown in FIG. 4, the oil pressure supply mechanism 50 uses the engine 1 as a rotational drive source, and sucks oil in a tank 62.
It has an oil pump 64 that pressurizes and supplies hydraulic pressure at a predetermined line pressure to the manual port 46, and an electromagnetic proportional control type relief valve 66 installed between the discharge side of the oil pump 64 and the tank 62. ing. Therefore, the set pressure of the relief valve 66 is determined according to the value of the command current i supplied to the proportional solenoid 66A of the relief valve 66, and the amount of oil returned to the tank 62 is adjusted according to this set pressure.
The hydraulic pressure P supplied by the hydraulic pressure supply mechanism 50 changes in proportion to the command current i, as shown in FIG.

The vehicle speed sensor 52 detects the rotational speed of the speedometer pinion 36 of the transfer 14 and outputs a vehicle speed signal V in the form of a pulse signal to the controller 58 in accordance with this. Further, the front wheel rotation sensor 54 and the rear wheel rotation sensor 56 are individually installed at predetermined positions of the front wheel output shaft 16 and the rear wheel propeller shaft 22, and detect the rotation speed of each shaft and respond accordingly. The rotation signal nf+nr based on the pulse signal is individually output to the controller 58. The lateral acceleration sensor 57 is installed at a predetermined position on the vehicle, and is configured to detect the lateral acceleration (corresponding to centripetal acceleration) of the vehicle and output a lateral acceleration signal gv, which is an analog voltage, to the controller 58. It is formed.

The controller 58, as shown in FIG.
/D converter 73, a D/A converter 76 that converts the control signal from the microcomputer 70 into D/A, and this D/A converter 73;
The command current i according to the output of the A converter 76 is applied to the relief valve 6.
6.

The microcomputer 70 includes an interface circuit 80. Arithmetic processing unit 82. It is configured to include at least a storage device 84 such as ROM and RAM. Arithmetic processing unit 82
reads each detection signal via the interface circuit 80, and performs arithmetic and control processing (see FIG. 8) for driving force distribution control in accordance with a predetermined program stored in advance. Further, the storage device 84 stores in advance programs, fixed data, etc. necessary for execution of processing by the arithmetic processing unit 82, and can temporarily store the processing results. Among these, fixed data is
It includes storage tables corresponding to each control characteristic shown in FIGS. 5 to 7.

To explain this in detail, first, FIG. 5 shows the control characteristics of the torque 8T transmitted to the front wheels with respect to the front and rear wheel rotational speed difference ΔN using the lateral acceleration G7 or the vehicle speed ■ as a parameter. In this control characteristic, the lateral acceleration G7 is its reference value c
Depending on whether or not it is greater than or equal to y+, the control mode is divided into a high lateral acceleration control mode corresponding to turning driving, and a low lateral acceleration control mode including straight driving or a state close to straight driving. In the case of the high lateral acceleration control mode, the lateral acceleration G7 is used as a parameter, and the lateral acceleration G7 is made up of a plurality of straight lines that change with a thick (indeed, low proportional gain)
However, in both cases, the minimum transmission torque is 8T1), and these are stored as map rBJ. On the other hand, in the case of the low lateral acceleration control mode, the rotational speed difference ΔN is the predetermined value Δ
N□~ΔN.

Region I where the rotational speed difference ΔN is positive (varies depending on the vehicle speed V) and the region near zero and its positive and negative directions, that is, −ΔN, (~-
ΔNc) ~ΔN, (~ΔN.

) and a region (2) in which the rotational speed difference ΔN is on the negative side and a tight corner braking phenomenon occurs. Among these, in region ■, vehicle speed ■ is the parameter, and vehicle speed V is ■.

(For example, 5 km/h: All vehicle speeds below this are ■.

As the transmission torque ΔT corresponding to the initial engagement force of the clutch 37 (initial rtJ4) changes from ΔT1 (for example, 1100 k/h: all vehicle speeds exceeding this are assumed to be For example, front and rear wheel distribution ratio is 5:9.
(a value corresponding to 5) to Δr, (if 'Jl, a value corresponding to a front and rear wheel distribution ratio of 30 near 0). Then, when entering the region (3), the transmitted torque ΔT increases with a proportional gain that does not depend on the vehicle speed V and the lateral acceleration G7 (however, it is larger than in the high lateral acceleration control mode). Also, area ■
When the vehicle is in a two-wheel drive state, the transmission torque ΔT is gradually reduced to zero by a predetermined proportional gain, and a two-wheel drive state is established. The above areas■
~■ are stored in the memory table as map rAJ.

In addition, FIG. 6 shows the value of the transmission torque ΔT to the front wheels that changes linearly according to changes in the supply pressure P of the hydraulic pressure supply mechanism 50, and FIG. Pressure P
The values of each are shown.

Therefore, when the transmission torque ΔT is determined by referring to the memory table corresponding to FIG. 5, the controller 58 must output it by sequentially referring to the memory tables corresponding to FIGS. 6 and 7. The value of the command current i can be calculated backwards.

Next, the operation of the above embodiment will be explained.

When the gear switch is turned on, the power is turned on and control by the controller 58 is started. The controller 58 executes a predetermined main program and executes fastening force variable control shown in FIG. 8 by timer interrupt processing every predetermined time (for example, 20 m 5ec).

On the other hand, when the engine is rotated, the oil pump 64 starts operating, and the hydraulic pressure supply mechanism 50 becomes able to supply the hydraulic pressure P according to the command current i.

First, the timer interrupt process shown in FIG. 8 will be explained.

In step (3) in the figure, the arithmetic processing unit 82 calculates the vehicle speed signal V detected by the vehicle speed sensor 52.

The rotation signals n and n detected by the front wheel rotation sensor 54 and the rear wheel rotation sensor 56, and the lateral acceleration signal g7 detected by the lateral acceleration sensor 57 are sequentially read at predetermined time intervals. Next, in step (2), the vehicle speed V, front wheel rotation speed N, and rear wheel rotation speed Nr are calculated by calculating the number of pulses per unit time or the pulse interval from the detection signal in step (2), and are stored in a memory table (not shown). Calculate the lateral acceleration G9 by referring to
The results are temporarily stored.

Next, the process proceeds to step (2), in order to recognize the slip situation, the rotational speed difference ΔN between the front and rear wheels is calculated using ΔN=N, -NfO2, and the result is temporarily stored, and the process proceeds to step (2).

In step (2), it is determined whether the lateral acceleration G7 calculated in step (2) is greater than or equal to a predetermined reference value Gvt (see FIG. 5). This determination is made to distinguish whether the vehicle is in a straight running state, a state close to it, or a turning state, and the reference value G71 is a value that can be discriminated by a driving test or the like. Therefore, this judgment is GV<
In the case of GvI, it is assumed that the vehicle is in a straight-ahead running state or a near-straight running state, and the process moves to step (2).

Then, in step (2), the torque ΔT to be transmitted to the front wheels is determined by referring to the map rAJ in the memory table corresponding to FIG. 5 described above. Specifically, the region I-region is selected according to the values of the vehicle speed ■ and the rotational speed difference ΔN. In other words, if we assume that the vehicle speed V=V, the rotational speed difference ΔN is very small, and -ΔNd≦
When ΔN≦ΔN1, it is assumed that the vehicle is traveling straight on a high μ road such as dry asphalt, and the vehicle speed is V in region ■.
=V, initial transmission torque ΔT=ΔT is set. The value of this initial torque ΔT is set to be larger as the speed increases (~ΔT). Furthermore, even if the vehicle speed is V=V, when the rotational speed difference ΔN>ΔN3, the vehicle is running straight or nearly straight, but when starting or accelerating,
When braking.

Assuming that a relatively large drive wheel slip occurs due to driving on a low-μ road, etc., the transmission torque ΔT corresponding to the rotational difference ΔN is set in region I. Further, when ΔN<-8N, it is assumed that a low vehicle speed tight corner braking phenomenon is occurring, and ΔT is set to gradually decrease to zero.

Next, the process moves to step (2), and the arithmetic processing unit 82 calculates the value of the command current i according to the torque 8T to be transmitted to the front wheels determined in step (2) as shown in FIG.

Setting is made by referring to the memory table corresponding to FIG. 7 and calculating backwards, for example, ΔT1 to P+-i+ in each figure, and then the process proceeds to step (2).

In step (2), a control signal corresponding to the value of the command current i determined in step (2) is output to the D/A converter 76, and the process returns to the main program.

As a result, the D/A converter 76 converts the input control B signal into an analog signal and outputs it to the drive circuit 78.
supplies the command 'fWfflj of the value set as described above to the proportional solenoid 66A of the relief valve 66. Therefore, the hydraulic pressure supply mechanism 50 supplies a hydraulic pressure P (see FIG. 7) according to the command current i to the clutch 37, and the engagement force of the clutch 37, that is, the transmission torque 8T is a value corresponding to the hydraulic pressure P (see FIG. 6). reference).

Meanwhile, while repeating the timer interrupt processing, the step
If G7≧GVI, it is recognized that the vehicle is turning at a relatively high speed, and the process moves to step (2).

Then, in step (2), the torque 8T to be transmitted to the front wheels is determined by referring to the map rBJ in the memory table corresponding to FIG. 5 described above. Specifically, first, a curve is selected according to the lateral acceleration GVO value, and the value of the transmission torque ΔT corresponding to the rotational speed difference ΔN in the curve is determined. Thereby, the transmission torque ΔT (clamping force) is determined to be proportional to the rotational speed difference ΔN, and the larger the lateral acceleration G7 is, the smaller the rate of increase in the transmission torque ΔT is. Further, in this embodiment, regardless of the lateral acceleration Gv, the transmission torque 8T is set to be equal to or greater than the minimum initial value ΔT1 in consideration of the responsiveness of the clutch 37 and the like.

Thereafter, the processes of steps (1) and (2) are repeated in the same manner, and the process returns to the main program.

Therefore, according to this embodiment, by repeating the above-mentioned process, in an area where the rotational speed difference ΔN is small, such as when driving straight or close to it on a dry asphalt road,
The clutch 37 generates an initial transmission torque T according to the vehicle speed V, and a four-wheel drive state is established in which torque is also distributed to the front wheels. At this time, as the vehicle speed increases, the amount of torque distribution is controlled to increase in the four-wheel drive direction, thereby improving straight-line stability at high speeds. Furthermore, even when driving straight, for example, when starting, accelerating/decelerating, braking, or driving on a road with a low friction coefficient, the rotational speed difference ΔN between the front and rear wheels increases due to slipping. , front wheel side transmission torque Δ
T is continuously controlled in the four-wheel drive direction in proportion to the rotational speed difference ΔN, and a good driving condition can be obtained without any sudden changes in the vehicle.

Furthermore, if a tight corner braking phenomenon occurs during a turn at speed i, the rotational speed difference ΔN becomes a negative value, contrary to the case of drive wheel slip. However, in this case, the generation of the fastening force is released (ΔT-0), the rear wheels are completely driven, and the tight corner braking phenomenon does not occur.

On the other hand, if, for example, the vehicle turns at a relatively high speed and a lateral acceleration larger than the reference value occurs, a four-wheel drive state is set according to the lateral acceleration G7 and the rotational speed difference ΔN, and good driving performance is obtained. In addition, in this case, it is possible to calculate an appropriate transmission torque ΔT, thereby controlling the moment of the vehicle in one direction when turning, and making it possible to give the steering characteristics a tendency such as weak oversteer or weak understeer. .

In this embodiment, the lateral acceleration detection means is formed by the lateral acceleration sensor 57, the A/D converter 73, and the processing of steps (2) and (2) in FIG.

Rear wheel side rotation sensors 54, 56 and steps ■~ in Fig. 8
Through the process of (3), a front and rear wheel rotational speed difference detection means is formed.
A vehicle speed detection means is formed by the vehicle speed sensor 52 and the processing of steps (2) and (2) in FIG. 8, a comparison means is formed by the processing of step (2) in FIG. A converter 76, drive circuit 78. A second clutch control means is formed by the hydraulic pressure supply structure 50, and an eighth
Processing of steps ■, ■, ■ in the figure and D/A converter 76,
Drive circuit 7th, hydraulic supply @Ig50 forms the first clutch control means.

Note that the vehicle speed detecting means in the above embodiment is not limited to using a vehicle speed sensor, and the front wheel rotation sensor may also serve as the rear wheel rotation sensor. Further, the front and rear wheel rotational speed difference detecting means in the present invention may directly detect the rotational speeds of the front wheels and the rear wheels.

Further, in the embodiment described above, a hydraulically driven wet friction clutch is used as the clutch, but an electromagnetic clutch, for example, may be used as long as it is a clutch that can continuously distribute driving force.

Furthermore, the present invention is not limited to four-wheel drive vehicles based on rear-wheel drive vehicles, but may be applied to a transfer clutch mounted on a four-wheel drive vehicle based on front-wheel drive vehicles. , in that case, the rotational speed difference Δ
N may be calculated as Nf-N.

Furthermore, in the above-mentioned region (2) of the low lateral acceleration control mode, the map may be configured such that the transmitted torque ΔT changes depending on the value of the lateral acceleration GY even if the rotational speed difference ΔN is the same.

Furthermore, in the present invention, the controller 58 is a counter instead of a microcomputer.

It may be configured by an electronic circuit such as a comparator.

C Effects of the Invention] As explained above, the invention distinguishes whether the vehicle is traveling straight, nearly straight or in a turning state according to the lateral acceleration, and when driving in a corner, the difference in rotational speed between the front and rear wheels and the lateral In addition to continuously distributing the driving force according to the acceleration, when the rotational speed difference is large in straight-line or near-straight driving conditions, the clutch engagement force is continuously changed according to the rotational speed difference. Since the initial engagement force of the clutch is kept constant when the clutch is small, and the engagement force is increased according to the vehicle speed, it is possible to ensure stability during high-speed straight running with small rotational speed difference and lateral acceleration. It is also possible to control the yaw of the vehicle when turning, which generates acceleration, and this makes it possible to improve steering characteristics such as neutralization, thereby achieving both good drive force distribution when going straight at high speed and when turning with high lateral acceleration. be able to.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of this invention in correspondence with the scope of the claims, FIG. 2 is a configuration diagram showing an outline of an embodiment of this invention,
3 is a schematic sectional view showing the transfer in the embodiment of FIG. 2, FIG. 4 is a block diagram centering on the controller in the embodiment of FIG. 2, and FIGS. 5 to 7 correspond to the memory table. 5 is a graph showing the relationship between rotational speed difference ΔN and transmission torque ΔT to the front wheels using lateral acceleration G7 or vehicle speed ■ as a parameter, and FIG. 6 is a graph showing the relationship between rotational speed difference ΔN and transmission torque ΔT, and FIG. 7 is a graph showing the relationship between the command current i and the supply pressure P, and FIG. 8 is a schematic flowchart showing the processing procedure executed in the controller. In the figure, 1 is an engine, 4 is a driving force distribution control device, 14 is a transfer, 37 is a clutch, 50 is a hydraulic pressure supply mechanism, 52 is a vehicle speed sensor, 54 is a front wheel rotation sensor, 56 is a rear wheel rotation sensor, 57 is a lateral acceleration sensor, and 58 is a controller.

Claims (1)

[Claims] (1) A transfer is provided that distributes engine driving force to the front and rear wheels. A driving force distribution control device for a four-wheel drive vehicle that issues commands according to driving conditions includes a front and rear wheel rotational speed difference detection means that detects a rotational speed difference between the front and rear wheels, and a lateral acceleration that occurs in the lateral direction of the vehicle. lateral acceleration detection means for detecting, vehicle speed detection means for detecting vehicle speed, and comparison means for comparing the lateral acceleration with a reference value set to be able to distinguish whether the vehicle is traveling straight, close to it, or turning. , a first clutch control means for changing the engagement force of the clutch according to the rotational speed difference and the lateral acceleration when the comparison means determines that the lateral acceleration is equal to or higher than a reference value; If the comparison means determines that the lateral acceleration is less than the reference value,
When the rotational speed difference is within a small predetermined range, the clutch generates an initial engagement force that increases or decreases depending on the vehicle speed value, and when the rotational speed difference is outside the predetermined range, the clutch generates an initial engagement force that increases or decreases depending on the vehicle speed value. A driving force distribution control device for a four-wheel drive vehicle, comprising: second clutch control means for changing the engagement force of the clutch.