JPH0596970A - Control device for rear wheel differential limit device - Google Patents

Abstract

PURPOSE:To control torque distribution to right and left rear wheels so as to improve turning property, acceleration, and stability, by providing a means to set differential limit torque increasing-function-likely in the middle speed range and the high speed range and a means to set the torque according to throttle opening and opening/closing speed. CONSTITUTION:Signals from wheel speed sensors 41L, 41R and a longitudinal G sensor are input to the vehicle speed computing part 51 of a control unit 50 for torque distribution to right and left rear wheels so as to compute vehicle speed V, and differential limit torque Td is increasing-function-likely set by a differential limit torque I setting part 52 based on a map. Further, signals of a throttle opening sensor 43 and a throttle opening/closing speed computing part 54 are input to a differential limit torque II setting part 55 so as to decide differential limit torque Td1, Td2, and the differential limit torque Td, the signals of a slip judging part 56 and ABS control 60 are together input to a duty ratio conversion part 53, and the duty signal is input to a solenoid valve 40'. Consequently, vehicle stability, running durability, accelerator controllability, and braking property in the middle speed range can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling a differential limiting torque of a rear wheel differential limiting device mounted on a rear differential of a vehicle according to each driving condition.

[0002]

2. Description of the Related Art Generally, it is known that a vehicle has different peculiar motion performance depending on the drive system. For example, 2 wheel drive FF and FR vehicles have 4 wheel drive 4WD
Compared to a car, it is more likely to slip on rough roads. Also, in FF vehicles, when the accelerator pedal is depressed during acceleration to accelerate, the lateral force on the front wheels decreases and drifts, resulting in an understeer tendency. When the accelerator pedal is released and decelerated, engine braking is applied to the front wheels and cornering force increases. As a result, a tuck-in phenomenon occurs. In an FR vehicle, if the throttle is turned on during turning, the lateral force on the rear wheels decreases and side slippage occurs, resulting in an oversteering tendency. On the other hand, four-wheel drive four
In a WD vehicle, slip and skid are avoided by driving four wheels, and the limit performance during driving, braking, and turning is improved. In addition, the influence of throttle on / off acts on the front and rear wheels at the same time, so the tendency of understeer and oversteer becomes weaker, and the characteristics become intermediate between the two. In terms of vehicles, 4WD vehicles have become very popular.

By the way, in the above-mentioned 4WD vehicle, the torque distribution of the front and rear wheels and the left and right rear wheels further affects the turning performance and the vehicle behavior change, and by optimizing these torque distributions, the dynamic performance and the dynamic performance can be improved. The stability can be further improved. In other words, the response is good at the beginning of turning and when changing lanes, the maneuvering performance is improved so that the tight corner braking phenomenon does not occur during low-speed turning, and the directional stability is maintained to maintain the vehicle attitude when turning on and off when turning. It is expected that such performances as improving the vehicle stability, improving the straight running stability against a disturbance such as cross wind, and effectively acting the ABS control during braking. Therefore, in order to satisfy such exercise performance, it has been proposed to variably control the torque distribution of the front and rear wheels and the left and right rear wheels, which have a large influence, by using various parameters.

Conventionally, the above-mentioned control device for torque distribution between the left and right rear wheels is constructed so that a differential limiting device is mounted on the rear differential and a differential limiting torque is applied as required. As the differential limiting device in this case, the torque-sensitive mechanical type can effectively transmit the driving force by generating the differential limiting torque according to the accelerator operation, and can improve the stability of straight traveling, but When the throttle is turned on or off, it directly affects the steering feel and impairs maneuverability. Rotation difference sensitive viscous coupling type is throttle on during turning,
Since it is not affected by turning off, good maneuverability can be secured and, at the same time, slip of one wheel can be prevented, but the differential limiting torque cannot be variably controlled. In this respect, in the multi-disc clutch type, it is possible to arbitrarily variably control the differential limiting torque and improve the performance other than the maneuverability and the running performance.

In view of this, there are the following prior arts for electronically controlling a rear wheel differential limiting device using a multi-plate clutch. Japanese Unexamined Patent Publication No. 62-178434 discloses that the differential limiting torque is increased during high-speed straight traveling when the vehicle speed is equal to or higher than a predetermined value and the steering angle is equal to or lower than the predetermined value, and traveling stability is improved. In Japanese Patent Laid-Open No. 61-102321, the acceleration state is detected by the accelerator depression amount, and the differential limiting torque is controlled in an increasing function according to the accelerator depression amount to improve the acceleration performance during acceleration. To improve the turning performance of. Further, it is shown that the response of the operation of the differential limiting device is improved by obtaining and controlling the differential value of the accelerator depression amount.

[0006]

By the way, in the former case of the above-mentioned prior art, since the differential limiting torque is controlled to be turned on and off at the time of high speed, the torque distribution particularly in the medium speed range. The effect of control cannot be obtained. In the latter case, the acceleration state is detected and controlled by the accelerator depression amount, but the driver's will also needs to consider the depression speed and the opening speed during deceleration. Is enough.

The present invention has been made in view of this point, and in the torque distribution control of the left and right rear wheels using the multiple disc clutch in the rear wheel differential limiting device, the differential limiting torque is controlled with respect to the vehicle speed and the accelerator operation. Is optimized to improve turning performance, acceleration performance, stability, and the like.

[0008]

In order to achieve the above object, the present invention is provided with a differential limiting device of a multi-disc clutch on the rear differentials of the left and right rear wheels, and the differential limiting torque of this differential limiting device is electronically controlled. In a control system for controlling dynamically, a first differential limiting torque setting means for setting the differential limiting torque in an increasing function in a medium speed range or a high speed range of the vehicle speed, and separately according to the throttle opening and the throttle opening / closing speed. A second differential limiting torque setting means for adding the set values to calculate the differential limiting torque, and a converting means for outputting a signal according to the differential limiting torque are provided.

[0009]

According to the above construction, the differential limiting torque of the differential limiting device for the rear differential is variably controlled in the high speed region of the vehicle speed while the vehicle is running, and understeer is appropriately added and stabilized in this region. Improve the sex. Also,
The parameters of throttle opening and throttle opening / closing speed are used to properly judge whether the vehicle is accelerating, decelerating, or accelerating, and the differential limiting torque is optimally controlled under these driving conditions to improve acceleration, braking, etc. become.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 2, a drive system of a full-time four-wheel drive vehicle having a center differential will be schematically described. Reference numeral 1 is an engine, 2 is a clutch, 3 is a transmission, and the transmission output shaft 4 is a center differential 20. Are typing in. Center differential 2
0 to the front drive shaft 5 in the front and rear drive shaft 6 in the rear
The front drive shaft 5 is output to the left and right front wheels 9L and 9R via the front differential 7 and the axle 8, and the rear drive shaft 6 is the propeller shaft 10 and the rear differential 1.
1, via left and right rear wheels 13L and 13R via the axle 12, respectively.

The rear differential 11 is a bevel gear type, and a hydraulic multi-plate type rear clutch 28 is attached as a differential limiting device between the differential case 11a and one side gear 11b of the rear differential 11 so as to bypass. When the differential limiting torque Td of the rear clutch 28 is zero, the left and right rear wheels 13L, 13R
When a predetermined differential limiting torque Td is generated, the torque is moved from the high speed wheel to the low speed wheel by the torque differential Td, and when the differential limiting torque Td is the largest, the left and right rear wheels 13L and 13R are locked. The torque is distributed according to the product W · μ of the vehicle weight W and the road surface friction coefficient μ.

The center differential 20 is a compound planetary gear type, and has a first sun gear 21 integrated with the transmission output shaft 4, a second sun gear 22 integrated with the rear drive shaft 6,
And a plurality of pinions 23 arranged around the sun gears 21 and 22, and the first pinion gear 23a of the pinion 23 is provided to the first sun gear 21 and the second pinion gear 2
3b meshes with the second sun gear 22, respectively. Further, the transmission output shaft 4 has a reduction drive gear 2
5 is rotatably provided, a pinion 23 is pivotally supported by a carrier 24 that is integral with the drive gear 25, and the drive gear 25 is configured to mesh with a driven gear 26 that is integral with the front drive shaft 5. On the other hand, the center differential 20 is provided with a hydraulic multi-plate center clutch 27 as a differential limiting device. The center clutch 27 is coaxially arranged, for example, by connecting the drum 27a to the carrier 24 and the hub 27b to the rear drive shaft 6 immediately after the center differential 20, respectively.

With the structure of the center differential 20, the speed change power input to the first sun gear 21 is dividedly transmitted to the carrier 24 and the second sun gear 22 with a predetermined reference torque distribution. Further, the rotation difference between the front and rear wheels during turning is absorbed by the planetary rotation of the pinion 23. Here, the reference torque distribution is two sun gears 21 and 2.
It is freely set by the four gear meshing pitch circle radii of the two and the two pinion gears 23a and 23b. Therefore, the reference torque distribution et of the front wheel torque TF and the rear wheel torque TR is, for example,

[Equation 1] As described above, it is possible to set the rear wheel with a heavy weight.

Further, the above center differential 2
Immediately after 0, a hydraulic multi-plate center clutch 27 is coaxially arranged by connecting the drum 27a to the carrier 24 and the hub 27b to the rear drive shaft 6 integrated with the second sun gear 22. The differential limiting torque Tc of the multi-plate clutch 27 limits the differential of the center differential 20, and the torque can be moved from the rear wheel side to the front wheel side. Here, when the front engine is installed, the static weight distribution ew of the front wheel weight WF and the rear wheel weight WR of the vehicle is, for example,

[Equation 2] In the case of direct connection by the multi-plate clutch 27, if the road surface friction coefficients μ of the front and rear wheels are equal, this weight distribution ew
Torque is distributed more heavily to the front wheels. Therefore, it becomes possible to control the torque distribution of the front and rear wheels by the differential limiting torque Tc of the multi-plate clutch 27 in a wide range between the reference torque distribution et of the rear wheel bias and the weight distribution ew of the front wheel bias. ..

Next, the hydraulic control system for the center clutch 27 and the rear clutch 28 will be described. First, when the transmission is an automatic transmission, the oil pump 3 of its hydraulic control system is used.
It is configured by using the line pressure obtained by adjusting the hydraulic pressure of 0 with the regulator valve 31. Therefore, the center clutch hydraulic pressure control means 32 has a clutch control valve 34 that communicates with the line pressure oil passage 33, and this clutch control valve 34 communicates with the center clutch 27 via an oil passage 35. Further, the line pressure oil passage 33 communicates with the solenoid valve 40 through an oil passage 38 having a pilot valve 36 and an orifice 37, and the duty pressure by the solenoid valve 40 acts on the control side of the clutch control valve 34 through the oil passage 39. To do. When a duty signal corresponding to each traveling condition from the control unit 50 is input to the solenoid valve 40, the hydraulic pressure is drained to generate a duty pressure Pd. The duty pressure Pd
The clutch control valve 34 is operated in accordance with the above, and the differential limiting torque Tc of the center clutch 27 is variably controlled. Further, the rear clutch hydraulic pressure control means 32 ′ is also similar to the oil passages 33, 38.
Clutch control valve 34 'and solenoid valve 40' in communication with
The differential limiting torque Td of the rear clutch 28 is variably controlled by the duty pressure Pd of the solenoid valve 40 '.

Referring to FIG. 1, an electronic control system for left and right rear wheel torque distribution will be described. First, as input information,
Wheel speed sensors 41L and 41R that detect the wheel speeds NL and NR of the left and right rear wheels 13L and 13R, and the front and rear G of the vehicle body longitudinal acceleration.
A front / rear G sensor 42 for detecting the throttle opening, and a throttle opening sensor 4 for detecting the throttle opening θ according to the accelerator depression amount.
Have three.

The control unit 50 has a vehicle speed calculator 51 for inputting the wheel speeds NL, NR and the front and rear G, and the wheel speeds NL, NL,
The vehicle speed V of the 4WD vehicle is always accurately calculated by determining the grip and slip of the wheel based on the speed obtained by integrating the NR and the longitudinal G. This vehicle speed signal is input to the differential limiting torque setting unit I52, and the differential limiting torque T is set based on the map of FIG.
Set d. In this map, the understeer is reduced in the low speed range, the differential limiting torque Td is set to zero in order to prevent the braking phenomenon during turning, and the differential limiting torque Td is constant and high in order to improve the stability in the high speed range. Determined by the value. Further, in the medium speed range, the differential limiting torque Td depends on the vehicle speed.
Is defined as an increasing function, and understeer is appropriately added to improve stability for steering and running. This torque signal is input to the duty ratio conversion unit 53 and converted into a predetermined duty ratio D, and this duty signal is output to the solenoid valve 40 '.

Further, in order to accurately detect the acceleration / deceleration state with respect to the accelerator work intended by the driver, there is provided a throttle opening / closing speed calculator 54 for inputting the throttle opening θ. The throttle opening / closing speed calculation unit 54 determines the throttle opening θ
Of the throttle opening speed dθ / dt and closing speed-
dθ / dt is calculated, and the throttle opening θ and the throttle opening / closing speed ± dθ / dt are input to the differential limiting torque setting unit II55, and the map of FIG. , Throttle opening / closing speed ± dθ / d
The differential limiting torques Td1 and Td2 are set for t based on the map of FIG. Here, it is desired to secure turning performance in a region where the throttle opening θ is small and to improve stability of vehicle behavior in a large region. In this respect, the map of (b) is different from the throttle opening θ. The dynamic limit torque Td1 is set to gradually increase from zero and rapidly increase in a large region. In addition, the map of (c) improves performance during sudden accelerator work,
The differential limiting torque Td2 for both the opening speed dθ / dt and the closing speed −dθ / dt is set as an increasing function after the predetermined opening and closing speeds, and is closed to prevent tire lock during deceleration. The torque change of the speed −dθ / dt is determined to be larger. Then, the torque Td1 determined by the throttle opening θ and the torque Td2 determined by the throttle opening / closing speed ± dθ / dt are added to calculate the total differential limiting torque Td of both, and this torque signal is used as the duty ratio conversion unit 5.
Enter in 3. Further, it has a slip determination unit 56 to which the wheel speeds NL and NR of the left and right rear wheels 13L and 13R are input. When the difference ΔN between the wheel speeds NL and NR is equal to or greater than a set value, slip determination is performed, and the duty ratio conversion unit 53 is used. The duty ratio D is forcibly set to, for example, 0% of the maximum differential limiting torque Td.

Next, the operation of this embodiment will be described. First, when the vehicle is traveling, the power of the engine 1 is input to the transmission 3 via the clutch 2, and the power of the shift is input to the first sun gear 21 of the center differential 20. Here, since the reference torque distribution is set to be biased to the rear wheels by the gear specifications of the center differential 20, the torque is distributed to the carrier 24 and the second sun gear 22 to output power. At this time, if the center clutch 27 is released, power is further transmitted to the front and rear wheels by the above-mentioned reference torque distribution, and FR is achieved even though it is a four-wheel drive, and turning performance and maneuverability are improved. The differential 20 becomes free, and it becomes possible to freely turn while absorbing the rotation difference between the front and rear wheels. Further, the differential limiting torque T is applied to the center clutch 27 by the hydraulic control means 32.
When c occurs, the torque is further bypassed between the second sun gear 22 and the carrier 24 according to the differential limiting torque Tc, and the torque is moved from the rear wheel heavy load to the front wheel heavy load torque distribution according to the vehicle weight distribution at the direct connection. It is variably controlled to prevent front wheels or rear wheels from slipping, and the center differential 2
With 0 differential limitation, power is transmitted effectively and escape, running performance and stability are improved.

The power distributed by the center differential 20 and the center clutch 27 and transmitted to the rear wheels is input to the rear differential 11, and the rear differential 11 and the rear clutch 28 further distribute the torque to the left and right rear wheels 13L, 13R. Controlled and transmitted. That is, when the rear clutch 28 is disengaged, the rear differential 11 becomes free, and due to the specifications of the gears, equal torque is distributed as shown by point P1 in FIG. In addition, the hydraulic control means 32 'causes the rear clutch 28 to operate as shown in FIG.
When the differential limiting torque Td is generated as described above, the power is effectively transmitted to the grip wheels due to the differential limiting of the rear differential 11, and the torque is moved from the high speed wheel to the low speed wheel according to the differential limiting torque Td, so that the differential lock At the time of direct connection, unequal torque is distributed according to the vehicle weight distribution of the left and right rear wheels 13L and 13R as indicated by point P2 in FIG.

On the other hand, when the vehicle is driven by four-wheel drive under the variable torque distribution control as described above, the control unit 50 accurately calculates the vehicle speed V from the wheel speeds NL and NR and the longitudinal G, and the throttle opening θ and the throttle. Opening / closing speed ± dθ / dt
Thus, the acceleration / deceleration state according to the driver's accelerator operation is accurately determined. Therefore, the case where the vehicle speed V changes will be described. In the low speed range, the differential limiting torque Td is set to zero according to the map of FIG. 3A, and a duty signal corresponding to this is output to the solenoid valve 40 'for control. As a result, the rear differential 11 is in a free state, and good turning performance and the like are ensured, and the braking phenomenon at the time of large turning is prevented. Further, when the vehicle speed V increases, the stability of the vehicle tends to decrease accordingly.
In the high speed range, the differential limiting torque Td is controlled to be increased as the vehicle speed V increases, and thus the understeer gradually increases, and the firm feeling of steering, the responsiveness, and the vehicle behavior at the time of changing lanes are well settled. Become. Further, the stability is improved when the vehicle is subjected to disturbances such as high-speed running and cross winds, and the differential limiting torque Td effectively transmits power to the left and right rear wheels 13L and 13R to secure a large driving force and improve running performance. To do.

Next, the case where the accelerator operation changes will be described. The differential limiting torque Td is variably controlled by the throttle opening θ and the throttle opening / closing speed ± dθ / dt depending on the slow, sudden acceleration or deceleration state. .. That is, as shown in FIG.
The differential limiting torque Td is controlled to zero at a low load according to the map of (c), and turning performance and the like are secured as in the case of the vehicle speed V. On the other hand, at the time of gentle acceleration, the differential limiting torque Td1 is controlled only by the throttle opening θ, and is increased and controlled particularly near full opening to ensure stability and a large wheel driving force. In this acceleration state, during the rapid acceleration with a large throttle opening speed dθ / dt, the differential limiting torque Td2 in this case is further increased.
Is added and controlled, so that wheel slip is prevented, traction is improved, and acceleration is improved by increasing wheel driving force. Throttle closing speed during deceleration-dθ / dt
In the case where the torque is large and sudden braking occurs, the differential limiting torque Td2 is immediately increased and controlled. For this reason, tire locking is less likely to occur, and the engine braking is effectively applied to the left and right rear wheels 13L and 13R to improve the braking performance. Further, the left and right rear wheels 1 are determined by the rotation difference between the left and right wheel speeds NL, NR
When it is determined that one of the 3L and 13R slips, the minimum duty ratio signal is output to the solenoid valve 40 ', and the differential limiting torque Td of the rear clutch 28 is forcibly controlled to the maximum and the differential lock is performed. This makes it possible to easily escape from a bad road.

Although the embodiments of the present invention have been described above, the present invention can also be applied to FR vehicles. The differential limiting torque setting map is not limited to the example.

[0024]

As described above, according to the present invention,
In the torque distribution control of the left and right rear wheels using the multi-plate clutch in the rear wheel differential limiting device, since the differential limiting torque is variably controlled even in the medium speed range with respect to the vehicle speed, vehicle stability in this medium speed range, The running performance can be improved. Since the throttle opening and the throttle opening / closing speed are used as parameters for the accelerator operation, it is possible to accurately judge the slow, sudden acceleration or deceleration state according to the intention of the driver. Since the differential limiting torque is controlled by adding the torques respectively determined by the throttle opening and the throttle opening / closing speed, optimal control can be performed at the time of gentle, sudden acceleration and deceleration, and accelerator controllability is improved. Since the differential limiting torque is largely controlled with respect to the throttle closing speed, braking performance can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electronic control system of an embodiment of a control device for a rear wheel differential limiting device of the invention.

FIG. 2 is a configuration diagram showing a configuration of a drive system and a hydraulic control system of a four-wheel drive vehicle to which the present invention is applied.

FIG. 3 is a diagram showing a map of differential limiting torque with respect to vehicle speed, throttle opening, and throttle opening / closing speed.

FIG. 4 is a diagram showing a control state of torque distribution of the left and right rear wheels.

[Explanation of symbols]

 11 Rear Differential 13L, 13R Rear Wheel 28 Rear Clutch 32 'Rear Clutch Hydraulic Control Unit 50 Control Unit 52, 55 Differential Limiting Torque Setting Unit 53 Duty Ratio Converting Unit 54 Throttle Open / Close Speed Calculation Unit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kiminaga Shirakawa 3-9-6 Osawa, Mitaka City, Tokyo Subaru Research Institute, Inc.

Claims (2)

[Claims] 1. A control system in which rear differentials for the left and right rear wheels are provided with a differential limiting device of a multi-disc clutch, and a differential limiting torque of the differential limiting device is electronically controlled, in a medium speed range or a high speed range of a vehicle speed. A first differential limiting torque setting means for setting the differential limiting torque in an increasing range in an increasing function, and a differential limiting torque setting means separately set according to the throttle opening and the throttle opening / closing speed are added to calculate the differential limiting torque. 2. A control device for a rear wheel differential limiting device, comprising: 2 differential limiting torque setting means; and converting means for outputting a signal according to the differential limiting torque. 2. The rear wheel according to claim 1, wherein the differential limiting torque according to the throttle opening / closing speed is set for each of the opening speed and the closing speed, and the torque change at the closing speed is set to be large. Control device for the differential limiting device.