JPH02290733A - Driving power control device of four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To improve running performance and travel durability by installing the second hydraulic clutch of a differential limit control device next to the differential device of a rear differential device used in the four-wheel drive vehicle of RR base, and the first hydraulic clutch of a power distribution device on a transfer device near the rear differential device. CONSTITUTION:In a four-wheel drive vehicle of RR base in which an engine 1 and a manual transmission 10 are arranged laterally at the rear of the vehicle body, a rear differential device 20 and a transfer device 30 are arranged ahead of the manual transmission 10 to make the drive gear 15 of the manual transmission 10 engage with the ring gear 21 of the rear differential device 20. Power is transmitted to right and left axles 6R, 6L from a differential device 22 installed on the ring gear 21. Moreover, power is transmitted to a front drive shaft 36 through the gear 32, the transfer shaft 31 and so on of the transfer device 30 engaging with the ring gear 21, whereas a differential limit control device 50 is installed next to the differential device 22, and a power distribution device 40 is installed near the transfer device 30 to control them by a hydraulic control device 62.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a front and rear wheel power distribution device installed in the drive system of a rear engine/rear drive (RR) based four-wheel drive vehicle, and a power distribution device for the left and right wheels. The present invention relates to a driving force control device using a differential limiting device, and specifically relates to one that variably controls driving force distribution torque and differential limiting torque in accordance with each driving condition and the like.

[Conventional technology]

In general, 4-wheel drive vehicles are equipped with a center differential, which always distributes torque between the front and rear wheels at a constant ratio (50:50), whereas hydraulic clutches, etc., adjust the torque distribution between the front and rear wheels depending on driving conditions and road surface conditions. Optimization through variable control is being considered. In addition, a hydraulic clutch for differential limiting control is installed in the differential limiting device installed between the left and right wheels to variably control the differential limiting torque depending on various conditions, improving driving performance, etc. That is what is being considered.

Variable control of the front and rear wheel torque and left and right wheel differential limit torque described above requires at least two sets of hydraulic clutches for each control, as well as a hydraulic control system such as an oil pump and valve means. How you place it is important. Here, when considering compact assembly of the hydraulic clutch, it is conceivable to arrange it inside the case of the transmission or differential device, but the following points need to be taken into consideration. In other words, the oil in hypoid gears such as final reduction gears or direction change gears is
Gear oil is generally operated under extremely high load and sliding speed conditions, so a gear oil with good load-bearing performance is used. However, this gear oil has a high viscosity and changes significantly with temperature, so It is unsuitable as a working fluid for pumps, and hydraulic control by duty solenoid valves may become impossible at low temperatures. In addition, hydraulic clutches under this oil condition generally have a low coefficient of friction, and the coefficient of friction is highly dependent on temperature, and if an appropriate friction coefficient modifier is not added, vibrations and stick-slip will occur when relative slip is applied. It is difficult to stably exhibit friction characteristics (μ-V characteristics) with respect to sliding speed over a long period of time. For this reason, when a hydraulic clutch is incorporated into a case of a final reduction gear, a direction change device, etc., it is necessary to separate the hydraulic clutch side and use a different oil from the high void gear oil. It is also important to arrange the hydraulic chamber of the hydraulic clutch on the stationary side rather than on the general rotating drum side to prevent the influence of centrifugal oil pressure and improve control accuracy.

On the other hand, the control system for front and rear wheel torque and differential limiting torque is controlled to maximize the performance of a four-wheel drive vehicle and to improve running performance, turning performance, etc. by limiting the differential between left and right driven wheels. It is hoped that

Conventionally, regarding this type of power control, there is a prior art disclosed in, for example, Japanese Patent Laid-Open No. 155027/1983. Here, two hydraulic clutches are provided in the case of the transfer device on the transmission output side, one for front wheel drive and one for rear wheel drive.
It has been shown that power distribution between the front and rear wheels is controlled by hydraulic control of two hydraulic clutches. Also, JP-A-62-10322
In the prior art of Publication No. 7, a multi-disc friction clutch is provided between the differential case of the differential gear and the side gear, and a hydraulic piston presses the clutch via the rod, slider, bearing, and reaction plate to generate differential limiting torque. arise. It is also shown that the differential limiting torque is variably controlled in accordance with the difference in rotational speed between the left and right wheels.

[Problem to be solved by the invention]

By the way, the above-mentioned prior art controls only one of the torque distribution between the front and rear wheels and the differential limiting torque between the left and right drive wheels, but does not control both at the same time. Further, since all of the prior art systems use gear oil as the lubricating oil for the hydraulic clutch, there are problems such as stick-slip as described above.

The present invention has been made in view of these points, and its purpose is to connect two sets of hydraulic clutches, one for front and rear wheel torque distribution and one for differential limiting torque, to the transaxle in an RR-based four-wheel drive system. It is compact and operates independently using an inner carrier side differential device, etc., and is properly arranged so as not to generate centrifugal hydraulic pressure. In addition, torque distribution by each hydraulic clutch and differential limiting torque are used to improve driving performance. An object of the present invention is to provide a driving force control device for a four-wheel drive vehicle that can perform control to improve turning performance, steering stability, starting performance, etc.

[Means to solve the problem]

In order to achieve the above object, the driving force control device of the present invention includes:
An RR-based model that transmits power from the engine, clutch, and transmission mounted at the rear of the vehicle body directly to the rear wheels via a rear differential system, and also to the front wheels via a power distribution device, etc. In a four-wheel drive vehicle, a second hydraulic clutch of a differential limiting control device is installed adjacent to the differential device of the rear differential device, and a power distribution device is installed in the transfer device near the rear differential device. A first hydraulic clutch is installed, and power distribution between the front and rear wheels is controlled by the transmission torque of the first hydraulic clutch,
The transmission torque of the second hydraulic clutch is used to control the differential differential between the left and right drive wheels.

[For production]

Based on the above configuration, the shifting power from the transmission is always transmitted to the rear wheels via the rear differential device, and at the same time is also transmitted to the front wheels according to the transmitted torque of the first hydraulic clutch of the power distribution device, resulting in full-time operation. Runs in 4-wheel drive. The transmission torque of the first hydraulic clutch of the power distribution device is changed according to the slip and driving conditions, and the power distribution control between the front and rear wheels is performed to prevent slips between the front and rear wheels, improving running performance, running stability, and starting performance. Improving sex, etc. In addition, the differential of the differential device is limited by the second hydraulic clutch of the differential limiting control device, and this differential limiting torque is variably controlled depending on the slip and driving conditions to prevent slip between the left and right drive wheels. This will help improve running performance, turning performance, etc.

〔Example〕

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

In FIG. 1, an overall outline of a RR-based four-wheel drive vehicle to which the present invention is applied, such as a transverse transaxle type vehicle with a manual transmission, will be described. code 1
is the engine, 2 is the clutch, 10 is the manual transmission,
These are arranged laterally in the left-right direction at the rear of the vehicle body, and a rear differential device 20 and a transfer device 30 are arranged in front of the manual transmission 10. A rear differential device 2 is installed inside the clutch housing 3 of the clutch 2 and the transmission case 4 of the manual transmission IO.
0 is housed to form a transaxle type, and similarly, the transfer device 30 is also housed inside the clutch housing 3, transmission case 4, and extension case 5.

The manual transmission 10 is provided with a plurality of sets of speed change gears 13 and a synchronizing mechanism 14 between an input shaft 11 and an output shaft 12,
It is configured to shift into multiple gears. The drive gear 15 of the output shaft 12 meshes with the ring gear 21 of the rear differential device 20, and the differential gear 22 attached to the ring gear 21 directly transmits power to the left and right rear wheels 7L and 7R via the left and right axles 6L and OR. configured. Therefore, a differential limiting control device 50 is provided adjacent to the differential device 22.

The transfer device 30 includes a gear 32 of a transfer shaft 3l arranged parallel to the rear differential device 20.
meshes with the ring gear 21, and the transfer shaft 3l further engages a pair of direction changing gears 33. 34, it is connected to a gear shaft 35 in the longitudinal direction at the center of the vehicle body. The gear shaft 35 is connected to a front drive shaft 36 via a power distribution device 40 inside the extension case 5, and the front drive shaft 36 extends to the front side via a joint 16 and a propeller link 17, and is connected to a front differential. device 18, axle 8
, 8 to the left and right front wheels 9, 9.

As a control system, an oil bomb 6■ equipped with a motor 60 is attached to the transmission case 4 or clutch housing 3 near the rear differential device 20, and the discharge pressure from the oil pump 6l is controlled by the hydraulic control device 6.
2, the power distribution device 40 and the differential limiting control device 50 are configured to be electrically controlled by a duty signal from a control unit 70.

In FIG. 2, the rear differential device 20 side will be described in detail.

First, the power distribution device 40 is connected to the extension case 5.
A gear shaft 35 and a drive shaft 3 coaxially arranged inside the
A first hydraulic clutch 45 is provided between the first hydraulic clutch 45 and the first hydraulic clutch 45.

In the first hydraulic clutch 45, a drum 45a is integrally connected to a drive shaft 36 supported by a bearing 41, and a gear shaft 3
A hub 45b is spline-coupled to 5, and a plurality of plates 45C and disks 45d are arranged alternately. Furthermore, a hydraulic chamber 45e and a piston 45f are attached to the extension case 5 on the fixed side, so that centrifugal oil pressure is not generated. It's starting to happen.

The differential device 22 of the rear differential device 20 includes a differential case 23 that is integrated with the ring gear 21.
A pinion 25 is provided in the inner part by a pinion support 24, and left and right side gears 26L and 26R are attached to the pinion 25.
mesh with each other, distributing the power equally to the left and right rear wheels, 7L,
7R and absorbs the difference in rotation.

In the differential limiting control device 50, a second hydraulic clutch 55 is provided between the differential case 23 and one axle 6R inside the clutch nozzle 1 housing 3 and the case 51 attached thereto. In this second hydraulic clutch 55, plates 55c and disks 55d are arranged alternately between a drum 55a of the axle 6R and a hub 55b of the differential case shaft portion 23a. is supported via a thrust bearing 54. Also, as described above, the side case 51 on the fixed side
A hydraulic chamber 55C, a piston 55f, and a return spring 55g are attached to the piston 55, and the piston 55r comes into pressure contact with the plate 55C via the thrust bearing 54 to generate a differential limiting torque.

Here, the first and second hydraulic clutches 45. The portion 55 is housed in a chamber separated from the lubrication wells for the rear differential device 20 and the transfer device 30 by an oil seal 56, and is filled with a predetermined amount of hydraulic clutch oil (for example, ATF) having desired friction characteristics. Since the plate 45C, disk 45d, etc. are lubricated by the rotation of each part, vibration and stick-slip caused by relative slip between the clutch disk and the plate are prevented from occurring.

In FIG. 3, first, the hydraulic control system will be described. The discharge pressure of an oil pump 61 driven by a motor 60 is regulated by a regulator valve 63 to produce predetermined working oil pressure and lubricating oil pressure. The hydraulic pressure oil passage 64 is connected to the clutch control well 6
5a and 65b, and the first and second hydraulic clutches 45.5 through oil passages 86a and 68b. It communicates with the hydraulic chamber side of 55. The oil passage 64 also includes a pilot valve 67 and an oil passage 68.
a and 68b communicate with the control side of duty solenoid valves 69a and 69b and clutch control wells 65a and 85b. The duty signal of the control unit 70 is output to the duty solenoid valves 89a, 89b to generate duty pressure, and by operating the clutch control valves 85a, 65b with this duty pressure, the first
, the clutch oil pressure of the second hydraulic clutch 45.55 is controlled to a desired value.

Next, the electrical control system of the control unit 70 will be described.

First, human power signals include a front wheel rotation speed sensor 71, a rear wheel rotation speed sensor 72, a left wheel rotation speed sensor 73, a right wheel rotation speed sensor 74, a throttle opening sensor 76, a gear position sensor 77, and so on. It has a steering angle sensor 78 and an acceleration sensor 79. The power distribution control system has a rotational speed difference detection unit 80a to which the front wheel rotational speed NF of the front wheel rotational speed sensor 71 and the rear wheel rotational speed NR of the rear wheel rotational speed sensor 72 are input. Calculated by NP-NR. If the rotation speed difference ΔNa is greater than or equal to the set value, the slip determination section 81
Slip is determined in step a, and a high clutch oil pressure Pa is determined by searching a map in the clutch oil pressure setting section 82a. This clutch oil pressure Pa is corrected to decrease according to the steering angle θ of the steering angle sensor 78, thereby avoiding a tight corner braking phenomenon.
The signal of the clutch oil pressure Pa is changed to a duty signal by the duty converter 83a, and the signal is converted to a duty signal by the duty converter 83a.
It is output to 9a. When the rotational speed difference ΔNa is less than or equal to the set value, the normal running determining section 84a determines that the running is normal, and the clutch oil pressure setting section 85a sets the clutch oil pressure Pa in this case.
is searched on the map. Here, using a map based on the vehicle speed V of the rear wheel rotation speed sensor 72 and the throttle opening α of the throttle opening sensor 76, the clutch oil pressure Pa is controlled so that the torque transmitted to the front wheels corresponds to the front and rear weight distribution. In addition, the gear position e of the gear position sensor 77 is corrected to increase on the low gear side, corrected to decrease with the steering angle θ of the steering angle sensor 78, and corrected to increase with the acceleration g of the acceleration sensor 79, and is optimized according to each driving condition. Clutch oil pressure Pa is set, and this clutch oil pressure Pa is also output after converting the duty.

The differential limiting control system also includes a rotation speed difference detection unit 80b to which the left wheel rotation speed N1 of the left wheel rotation speed sensor 73 and the right wheel rotation speed NR of the right rotation speed sensor 74 are input, and the rotation speed difference Δ
Nb is calculated by ΔNb-NL-NR. In this case as well, as described above, it includes a slip determination section 8lb, a normal running determination section 84b, clutch oil pressure setting sections 8.2b and 85b, and a duty conversion section 113b. In the case of slippage and normal running, the clutch oil pressure pb is set by a map search substantially similar to that described above.

Next, the operation of the driving force control device for a four-wheel drive vehicle having such a configuration will be described.

First, the power of the engine 1 is input to the manual transmission 10 via the clutch 2, and the shifted power is input to the rear differential device 20 from the output shaft l2, and is equally distributed to the left and right drive wheels by the differential device 22. Vehicle 8L, 61
? It is constantly transmitted to the rear wheels 7L and 7R via the

Further, the shifting power is inputted to the first hydraulic clutch 45 of the power distribution device 40 via the transfer device 30 consisting of the ring gear 21. Here, when the vehicle is running, signals such as front and rear wheel rotational speeds NP and NR are manually processed by the control unit 70, and the flowchart shown in FIG. 4(a) is executed. Therefore, during steady driving on a dry road surface, NF #NR is determined to be normal driving, and the clutch oil pressure Pa changes continuously so that the distribution ratio corresponds to the weight distribution between the front and rear wheels, and the corresponding duty signal changes to the duty signal. Output to solenoid valve 69a.

On the other hand, in the hydraulic control system, the oil pump 6l is constantly driven by the motor 60, and the hydraulic pressure is guided by the regulator valve 63 to the duty solenoid valves 89a, 89b and the clutch control valves 65a, 65b.

For this reason, the duty solenoid valve 69a controls the discharge of the pilot pressure regulated by the pilot valve 67 using the duty signal and changes the control pressure of the clutch control valve 65a. The working oil pressure is introduced, and the above-mentioned clutch oil pressure Pa is generated. Therefore, the piston 45r includes the plate 45c and the disk 4.
Clutch torque is generated by pressing 5d according to the clutch oil pressure, and the power according to this clutch torque is
Furthermore, power is transmitted from the front drive shaft 36 to the front differential device [8] via the blower shaft 17, etc., and is also transmitted to the front wheels 9, 9 via the axles 8, 8. It becomes a run.

At this time, the signals of the left and right wheel rotational speeds NL and NR are also input to the control unit 70, and the flowchart of FIG. 4(b) is executed. Therefore, in such normal driving, the clutch oil pressure pb is set to approximately zero, and the clutch oil pressure pb of the second hydraulic clutch 55 of the differential limiting control device 50 is approximately zero due to the duty solenoid valve 69b. Therefore, each part of the rear differential device 20 becomes free, and freely performs differential operation during turning to absorb rotational differences.

Next, when starting and accelerating, the clutch oil pressure P is adjusted according to the load.
a is set large, and accordingly, the first hydraulic clutch 4
5 transmission torque increases, power distribution to the rear wheels increases, and four-wheel drive performance improves. At this time, the clutch pressure pb also increases, so that in the second hydraulic clutch 55, the piston 551' is moved between the plate 55c and the disk 55.
By pressing d, a differential limiting torque is generated between the differential case 23 and one side gear 26R. For this reason, the left and right rear wheels 7L, 7R are differentially limited to a degree of differential lock, improving driving stability, and effectively transmitting power to the rear wheels 7L, 7R to promote starting acceleration.

Also, when turning, clutch oil pressures Pa and P are adjusted depending on the steering angle θ.
b is reduced, the rear wheel power distribution is reduced, and the differential limiting torque is also reduced, allowing the vehicle to turn smoothly without tight corner braking.

Here, if NL > NR, NL - NR - ΔN l) is less than the set value, and when the above-mentioned differential limit 1 · torque Tc occurs with the torque of the ring gear 21 as TI, the differential case 22 becomes ΔNb higher than NR. /2, the power is bypassed and transmitted from the differential case 22 to the right wheel 6R via the hydraulic clutch 5a, and the left wheel torque - (TI-TO)/
2, right wheel torque - (TI + TC)/2, resulting in unequal distribution of torque with right wheel bias. Also, NL <NR,
Even if NR - NL - ΔNb is less than the set value, the differential case 22 is N when differential limiting torque is generated.
Since it rotates slower than R by ΔN b/2, power flows from the hydraulic clutch 50 to the differential case 22 side, and the left wheel torque - (T t + T c) / 2 and the right wheel torque - (TI - TC) / 2. , resulting in unequal distribution of torque with a bias toward the left wheel.

This makes it possible to actively control any state between the normal differential operating state and the differential lock state by changing the differential limiting torque Tc.

On the other hand, if the rear wheel slips when driving on a rough road, it is determined that the rear wheel is slipping based on the rotational speed difference ΔNa, and the clutch oil pressure P
a becomes maximum. Therefore, the front and rear wheels are directly connected by the first hydraulic clutch 45, and the power is distributed approximately equally between the front and rear wheels, preventing slippage and maximizing all-terrain performance. Additionally, even if one of the left and right rear wheels 7L, 7R slips, it is determined to be a slip based on the rotational speed difference ΔNb.
Clutch oil pressure pb becomes maximum. Therefore, the second hydraulic clutch 55 locks the differential so that the rear differential device 20 is integrated with the vehicle, making it possible to escape from the rough road. The control of these slips is
Either one can be done separately or both can be done simultaneously.

Although one embodiment of the present invention has been described above, it is not limited thereto. In particular, the first hydraulic clutch 45 of the power distribution device 40 may be provided midway along the transfer shaft 31. In addition, in the case of a vehicle equipped with an anti-skid brake system (ABS), when the ABS is activated, the first and second hydraulic clutches 45. By controlling the torque of one or both of 55, the drive system can be maintained in the most effective coupling state.

〔Effect of the invention〕

As described above, according to the present invention, an RR-based four-wheel drive vehicle is provided with a power distribution device with a hydraulic clutch and a differential restriction control device with a hydraulic clutch, and is capable of controlling both power distribution and differential restriction. In addition to preventing slippage between the front and rear wheels and the left and right wheels, it also improves driving performance according to each driving condition and road surface condition.
It can improve running performance, handling stability, starting performance, turning performance, etc.

In particular, the combination of power distribution and differential limiting torque
The performance of a four-wheel drive vehicle can be maximized.

Furthermore, since the power distribution device and the differential limiting control device are mounted on the differential device side of the transaxle, the structure is compact and the control system is also simplified.

Furthermore, since the power distribution and differential restriction are controlled by the first and second hydraulic clutches, the electronic and hydraulic control systems are shared, and the electronic control system is also simplified.

Furthermore, since both hydraulic clutches are used with dedicated lubricating oil having desired friction characteristics, stick-slip and the like do not occur. Furthermore, the hydraulic chamber and piston are provided on the fixed side, so there is no influence of centrifugal hydraulic pressure.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram showing an embodiment of the driving force control device for a four-wheel drive vehicle of the present invention, Fig. 2 is a horizontal sectional view of the main parts, Fig. 3 is a diagram showing the hydraulic and electric control system, Figure 4 (a
) is a flowchart of the operation of power distribution control, and (b) is a flowchart of the operation of differential limiting control. ■...Engine, 2...Clutch, 7L, 7R・
... Rear wheel, 9... Front wheel, 20... Rear differential device, 22... Differential device, 40... Power distribution device, 45... First hydraulic clutch, 50... Difference motion limit control device, 55... second hydraulic clutch, 62...
...Hydraulic control device, 70...Control unit

Claims (2)

[Claims] (1) Rear engine/rear in which the power from the engine, clutch, and transmission mounted at the rear of the vehicle body is transmitted directly to the rear wheels via a rear differential device, and also to the front wheels via a power distribution device, etc. In a drive-based four-wheel drive vehicle, a second hydraulic clutch of a differential limiting control device is installed adjacent to the differential device of the rear differential device, and a power distribution device is installed in the transfer device near the rear differential device. A first hydraulic clutch is installed, the transmission torque of the first hydraulic clutch controls the power distribution between the front and rear wheels, and the transmission torque of the second hydraulic clutch controls differential limiting between the left and right drive wheels. A driving force control device for a four-wheel drive vehicle. (2) The first hydraulic clutch is provided on the shaft of the transfer device, the second hydraulic clutch is provided between the differential case of the differential device and one side gear, and the first and second hydraulic clutches are provided between the differential case of the differential device and one side gear. The driving force control device for a four-wheel drive vehicle according to claim 1, wherein the hydraulic chamber and the piston are attached to a case side that is a fixed member.