JPH01111534A - Torque split controller for four-wheel-drive car - Google Patents

Abstract

PURPOSE:To avoid differential locking due to a clutch in a torque split device provided to bypass a center differential gear by bringing the torque of a split clutch to nil when the clutch controlling signal is not generated. CONSTITUTION:A torque split device 25 having a variable clutch torque split clutch 27 is disposed to bypass a center differential gear 20 connected to the output shaft 4 of an automatic transmission 3. A control unit 50 receiving the output signals of sensors 40-46 for detecting various information controls the clutch torque and the torque distribution to front and rear wheels. Then, when the clutch control signal is not generated by failures of the control unit 50 or the like, the clutch torque of split clutch 27 is brought to nil and the torque distribution to front and rear wheels is brought to the initial distribution condition by the center differential gear 20. Thus, the safety, smooth turning property and the like are ensured.

Description

[Detailed description of the invention] [Industrial application field]

In a full-time 4Va drive vehicle equipped with a center differential device, the present invention adjusts the torque distribution between the front and rear wheels depending on driving conditions.
A torque split control device that controls I[f,
For more information, please see Clutch i! This relates to split clutch control using the %J control signal.

[Prior Art] A four-wheel drive vehicle with a center differential has the advantage of being able to absorb the difference in rotation between the front and rear wheels when turning, ensuring smooth turning performance in four-wheel drive. Therefore, a torque split control that provides such performance and further varies the torque distribution between the front and rear wheels depending on the driving conditions is considered. That is, when driving straight ahead or driving in 4th gear, f! of the vehicle applied to the front and rear wheels. If torque split control is performed according to weight distribution, the driving force distribution between the front and rear wheels will be optimized according to the weight distribution of the vehicle, and the effect of traction control can be obtained. When turning, if you perform torque split control depending on the situation, the front engine/front drive (FF
) It is possible to obtain optimal turning performance in consideration of stability and turning performance while suppressing the understeer tendency of cars and the oversteer tendency of front engine rear drive (PR) cars. Furthermore, by controlling the torque split by taking into account factors such as the coefficient of road friction μ and wheel spin, driving safety can be improved, and the system has a function that is equal to or better than the differential lock function of the center differential, making it possible to always ensure driving performance. It becomes possible. As described above in the examples above, it is expected that the torque split control of a four-wheel drive vehicle will maximize its performance and produce great effects. Therefore, although the applicant has already proposed a drive system for a four-brass drive wheel that can actively and variably control the torque split, there is still room for the development of other systems. Furthermore, f&appropriate electronic control systems are being developed to achieve torque splitting. Conventionally, regarding four-wheel drive vehicles with a center differential, there is a prior art, for example, in Japanese Patent Application Laid-Open No. 55-83617, in which the output side of a transmission is input to a center differential device, and the two output sides from this center differential device are Transmission is configured to the front and rear wheels. Further, it is shown that a clutch, a brake, and a selective clutch device are added to the center differential device for control. [Problems to be Solved by the Invention] Incidentally, in the conventional prior art described above, although there is only a center differential device, only one torque distribution ratio is determined by it. Further, the control system is a two-wheel drive, four-wheel drive, and differential lock switching control, and does not perform torque split control. In view of these points, the present invention provides a four-wheel drive system with a center differential and capable of variable control of torque split.
Torque split control is optimally controlled electronically, and torque control using clutch control signals is also optimized4.
An object of the present invention is to provide a torque split control device for a wheel drive vehicle.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a center differential device distributing power to the front and rear wheels in a predetermined torque distribution in the middle of the drive system, and a torque split device having a split clutch with variable clutch torque in the center differential device. A four-wheel drive vehicle that is connected in a bypass manner has a sensor that detects various information, a control unit that inputs and processes the signal of the sensor, and uses the clutch control signal of the control unit to control the torque of the split clutch as well as the sensor that detects various information. The circuit is configured to control torque distribution to the front and rear wheels, and the torque of the split clutch is set to zero when the clutch control signal is not output, and the clutch torque is controlled to be increased in accordance with an increase in the output of the clutch control signal. It is configured as follows.

[For production]

Based on the above configuration, a four-wheel drive vehicle equipped with a center differential device and a torque split device uses a clutch control signal from the control unit to generate a split clutch torque of the torque split device, so that part of the torque of the front and rear wheels is transferred from one side to the other. The torque split is actively and variably controlled by moving to the other side. If the split clutch is not controlled by the clutch control signal but the clutch control signal is not output due to a failure of the control unit or the like, the clutch torque is zero and the torque distribution to the front and rear wheels is the initial distribution state by the center differential device. Thus, in the present invention, in the case of failure of the control unit in active torque split control, it is possible to ensure safety, smooth turning performance, etc. by initial distribution.

【Example】

Embodiments of the present invention will be described below based on the drawings. Referring to FIG. 1, an outline of the Torx Gerritt control device of the present invention will be described. First, let's talk about the drive system of a four-wheel drive vehicle with a center differential and torque split control, which has a front engine in LA and is equipped with an automatic transmission with a torque converter. A torque converter 2° and an automatic transmission I13 are arranged in the longitudinal direction of the vehicle and connected to enable power transmission. The output shaft 4 of the automatic transmission 3 is input to a center differential device 20, and a torque split device 25 is provided to bypass the center differential device 20. The center differential device 20 is of a planetary gear type, and includes a sun gear 21. Ring gear 22. Binion 23 meshing with sun gear 21 and ring gear 22. and a carrier 24, to which the transmission output shaft 4 is coaxially connected. In addition, the two output side sun gear 21° ring gear 2
2, the large-diameter ring gear 22 is rotatably provided on the transmission output shaft, and the reduction gear 5. Furthermore, it is connected to a front drive shaft 7 parallel to the output shaft 4 via a reduction gear 6, and this front drive shaft 7 is connected to the left and right front @ 101.1 via a front differential device 8 and axle 9.
Transmission is configured to OR. On the other hand, the small diameter sun gear 21 is connected to the rear drive shaft 11, and the rear drive shaft 11 is connected to the rear drive shaft 11.
is the rear differential device12. Left and right rear wheels 1 via axle 13 etc.
The transmission is configured in 4L and 14R. In this way, the center differential device 20 transmits the transmission output to the front and rear wheels with a predetermined torque distribution, and absorbs the rotation difference between the front and rear wheels. Here, since the static load is larger at the front of the vehicle body than at the rear due to the drive system, the torque transmitted from the ring gear 22 to the front wheels is larger than the torque transmitted from the sun gear 21 to the rear wheels. There is. The torque split device 25 includes a bypass shaft 26. which is coaxial with the front drive shaft 7. For example, a hydraulic clutch 27 is provided as a latch that allows for variable torque control, and the bypass shaft 26
is attached to the hub 27a of the hydraulic clutch 27, and its drum 27b
is configured to be transmitted to the rear drive shaft 11 via a pair of gears 28 and 29. Here, the reduction gears 5, 6
is also a component in this case, and its gear ratio is, for example, “I
N, and the gear ratios of gears 28 and 29 are set slightly smaller than that. Further, the hydraulic clutch 27 is connected to the hydraulic unit 3
Clutch torque can be generated by supplying hydraulic oil from zero. In this way, in the hydraulic clutch 27, a rotation difference is generated in which the drum 27b has a slightly lower speed than the hub 27a. Therefore, when clutch pressure is applied to the hydraulic clutch 27 to generate clutch torque, the front wheel side of the hub 27a is moved from the front wheel side of the hub 27a to the rear of the drum 27b. Torque is transferred to the wheels according to the clutch pressure to vary the torque distribution between the front and rear wheels. That is, if the input torque of the center differential device 20 is Ti, and the front 1 to side distribution ratio by the center differential device 20 is γ, then the transmitted torque of the front drive shaft 7 is γ・Ti, and the torque transmitted to the rear drive shaft 11 is γ・Ti.
The torque of is distributed to (1-γ)·T1. Therefore, if the clutch torque is Tc and the gear ratio of gear 28.29 is K, the front drive shaft 7. The torques TF and TR of the rear drive shaft 11 are TF=γ・Ti
-Tc TR=(1-γ) ・Ti +KTC. In this way, due to changes in clutch torque Tc, the distribution ratio of front side torque TF continuously changes below the distribution ratio in the center differential device 20, and the distribution ratio of rear side torque TR continuously changes above the distribution ratio in the center differential device 20. It changes to act as a torque split. Next, the electronic control system of the torque split will be described. 40R, 41L, 41R, steering angle sensor 42. Engine speed sensor 43. Throttle opening sensor 44. Vehicle acceleration sensor 45. It has a gear position sensor 46 on the automatic transmission side, and these sensor signals are input to a control unit 50. The control unit 50 determines the torque distribution ratio between the front and rear wheels based on the slip state of the front and rear wheels in driving condition 1, determines the clutch pressure according to this torque distribution ratio, and outputs this clutch pressure control signal to the hydraulic unit 30. 6 In FIG. 2(a), the hydraulic unit 30 will be described. Reference numeral 31 is an oil passage to which line pressure for controlling an automatic transmission is supplied, for example, and this line pressure is guided to a pressure regulating valve 32. The pressure regulating valve 32 always generates a constant pilot pressure in the oil passage 33 while disconnecting communication between the oil passage 31 and the oil passage 33 that supply line pressure, and this oil passage 33 communicates with the duty solenoid valve 34. . The duty solenoid valve 34 generates duty pressure in the oil passage 35 by performing exhaust pressure control in response to a duty signal from the control unit 50. Duty pressure acts on the clutch control valve 36, and the line pressure oil passage 31 and the oil passage 37 of the hydraulic clutch 27 are in communication with each other, and the duty pressure supplies and drains oil to the hydraulic clutch 27 to generate clutch pressure. Generates clutch torque according to the Here, for example, the clutch pressure has a characteristic as shown in Fig. 2 (b) with respect to the duty ratio of the duty signal, and when the duty ratio is approximately zero, the clutch pressure becomes zero, and from this state, the duty ratio increases. Clutch pressure also increases accordingly. Note that the broken line in FIG. 2 is the characteristic of duty pressure. In this way, if the duty signal is not output due to a control unit failure, harness breakage, etc., the hydraulic clutch 27 is released as a clutch zero, and the center differential device 20 distributes torque to the front and rear wheels.
Hold the initial safe side distribution state. In FIG. 3, the control unit 50 will be described. First, the left and right front wheel rotation speed N of rotation speed sensors 40L and 40R.
The front wheel speed calculation unit 51 inputs FL and NFR, and the left and right rear wheel rotation speeds NRL and NR of the rotation speed sensors 41L and 41R.
It has a rear wheel speed calculation section 52 into which R inputs, and a front wheel speed calculation section 5
1° The rear wheel speed calculation unit 52 calculates the front and rear wheel speeds NF and NR.
Calculated by = (NFL+NFR) /2 NR= (NRL+NRR) /2. Front wheel speed calculation section 5144 wheel speed calculation section 52
The front and rear wheel speeds NF and NR of are input to the wheel speed calculation unit 53,
The average wheel speed N of the four wheels is calculated by N=(NF +NR)/2. This wheel speed N is input to the vehicle speed calculating section 54, and the vehicle speed ■ is calculated by taking into account the tire diameter. The steering angle λ of the steering angle sensor 42 and the car 31! Vehicle speed V of calculation unit 54
is input to the target torque distribution ratio determination unit 55, and the steering angle λ is inputted to the target torque distribution ratio determination unit 55. The rear wheel torque distribution ratio is determined by the vehicle speed parameter. Here, for example, the rear wheel torque distribution ratio SR is set as shown in FIG. 4(a). In other words, in a region where the medium-speed steering angle is relatively large, the rear wheel torque distribution ratio S is
R is set large, and in the high-speed small steering angle region, the rear wheel torque distribution ratio SR is set small to emphasize vehicle stability.In other regions, the rear wheel torque distribution ratio SR is set to an intermediate value. It has been designed with an emphasis on turning ability and stability. The rear wheel torque distribution ratio SR of the target torque distribution ratio determining section 55 and the acceleration G of the acceleration sensor 45 are input to the acceleration correction section 56, and if the acceleration G is approximately zero, it is assumed that the vehicle is running in a steady state and the rear wheel torque distribution ratio is changed. When SR is not corrected and acceleration G is generated during acceleration, the rear wheel torque distribution ratio SR is corrected to correspond to changes in vehicle weight distribution. The engine speed Ne of the engine speed sensor 43 and the throttle opening θ of the throttle opening sensor 44 are input to the engine torque calculating section 57, and the engine torque Te is determined based on the torque characteristics shown in FIG. 4(b). Wheel speed calculation unit 5
3 of the vehicle @ speed N, engine rotation speed Ne, and gear position Gr of the gear position sensor 46 are determined by the torque converter rotation ratio calculation unit 5
8, calculate backwards using the wheel speed N and gear G to find the turbine rotation speed Nt which is the output side of the torque converter 2, and find the rotation ratio Rw with the engine rotation speed Ne which is the input side of the torque converter 2. , Rv=Nt/Ne This rotation ratio R1 is input to the torque converter torque ratio calculation section 59, and the torque ratio Rt is determined according to the characteristics shown in FIG. 4(C).Then, the engine torque Te, )
torque converter torque ratio Rt. The gear position Gr is input to the center differential input torque calculation section 60, and the center differential input torque Ti is calculated as follows. Ti = Te -Rt -Gr Above rear wheel torque distribution ratio SR and center differential input torque T
i is input to the clutch pressure calculating section 61 to calculate the clutch pressure pc together with the clutch torque Tc. As already mentioned here, set the front torque to TF. When the rear torque is TR, the rear wheel torque distribution ratio SR is expressed as sR=TR/(TF+TR). Therefore, the above-mentioned front side distribution ratio γ. Substituting the equations for the input torque Ti, clutch torque Tc, and gear ratio into the above equation results in Tc = f(S R, Ti), and the clutch torque increases as the rear wheel torque distribution ratio SR and input torque Ti increase. The value of Tc increases. Also,
The relationship between clutch torque Tc and clutch pressure PC has unique characteristics depending on parameters such as the number of clutch plates constituting the hydraulic clutch 27 and the coefficient of friction, and is expressed as Pc = g (Tc) as shown in Fig. 4(d). It will be done. This clutch pressure Pc is input to the operation amount setting section 62, and using the characteristics shown in FIG. 2(b), it is converted into a signal of a duty ratio corresponding to the clutch pressure Pc and output. Next, the operation of the torque split control device configured as described above will be described. First, when the automatic transmission 3 is shifted to a driving range such as drive (D) while the vehicle is running, the power from the engine 1 is input to the automatic transmission I13 via the torque converter 2, and the transmission power is output. It is transmitted to the carrier 24 of the center differential device 20. And ring gear 22 and sun gear 2
1, corresponding to the static load distribution on the wheels of the vehicle,
The torque is distributed to the front and rear wheels at a ratio of 60:40, for example. Power beam from ring gear 22 Dacsigon gear 5, 6° Front drive shaft 7. The power from the sun gear 21 is transmitted to the front wheels IOT and IOR via the front differential device 8 and the like, and the power from the sun gear 21 is transmitted to the rear drive shaft 11. The power is transmitted to the rear wheels 14L and 14R via the rear differential equipment GT12, etc., and in this way, the full time 41! It will be driven. At this time, the hydraulic clutch 27 of the torque split device 25
rotates with a difference in rotation due to the gear ratio between reduction gear 5.6 and gear 28.29, allowing torque to be transferred to the rear wheels. On the other hand, various information is detected by each sensor of the electronic control system,
This is input to control unit 50. Then, the target torque distribution ratio determination unit 55 and the acceleration correction unit 56 determine the steering angle λ, the vehicle speed ■,
The driving conditions are determined based on the vehicle acceleration G and the vehicle body acceleration G, and the rear wheel torque distribution ratio SR is determined based on this. Furthermore, in the center differential input torque calculation section 60, the engine torque T
e. Gear stage Or. Furthermore, engine speed Ne, wheel speed N, and gear shift 1, I
The center differential input torque Ti is calculated using the rotation ratio Rw and torque ratio Rt of the torque converter 2 based on Gr. Therefore, during normal driving, the target torque distribution ratio determination unit 5
At 5, the rear wheel torque distribution ratio SR becomes the 4th due to the steering angle λ and vehicle speed ■.
Various determinations are made based on the pattern shown in Figure (a). That is,
When the center differential input torque is sufficiently large, for example, the steering angle at medium speed is relatively large, the rear wheel torque distribution ratio SR is set to a large value, and a duty signal corresponding to this is output, thereby increasing the duty pressure of the hydraulic unit 30. The hydraulic pressure of the hydraulic clutch 27 is further increased, and accordingly, the moving torque from the front wheel side to the rear wheel side is increased.
A large amount of torque is transferred to the rear wheels, resulting in an extremely large rear wheel torque distribution. On the other hand, as the vehicle speed ■ and the steering angle λ decrease, the rear wheel torque distribution also decreases accordingly, and in this way, the rear wheel torque distribution is variably torque split controlled according to the turning state. For this reason, 4 wheels 1
When turning with 5g dynamics, the front and rear tires slip,
It always maintains a large number of scratches (with the road surface) and encourages reliable turning along the target turning radius. In addition, Fig. 4 (a
), by setting a larger torque distribution ratio to the rear wheels, it is also possible to actively improve the vehicle's verbal performance, making sportier driving possible. In addition, especially when driving in a steady state when the vehicle body acceleration G is approximately zero when driving straight, the target rear wheel torque distribution ratio SR is adjusted to the center differential equipped W! 20
The torque distribution ratio is held at 40%. Since the rear wheel moving torque amount is zero in this flat clutch pressure calculation unit 61, the clutch pressure pc=0. Therefore, a signal indicating the duty ratio 0% is inputted from the operation amount setting section 62 to the solenoid valve 34 of the hydraulic unit 30, and the duty pressure is maximized and the hydraulic clutch 27 is drained by the clutch control valve 36. The oil pressure and torque of the clutch 27 become zero. Under these driving conditions,
The hydraulic clutch 27 is inactive, and only the torque distribution by the center differential device 20 provides initial torque split control corresponding to the vehicle body load distribution. On the other hand, when the vehicle is running at an accelerated speed outputted by the acceleration G, the rear wheel torque distribution ratio SR is corrected to be increased by the acceleration correction unit 56 in accordance with the acceleration G, that is, the backward movement of the vehicle body load when the vehicle is going straight or turning. Therefore, the clutch pressure Pc becomes a larger value than during normal driving when the acceleration G is zero, and a corresponding duty signal is input to the solenoid valve 34, and the clutch control valve 36 supplies oil to the hydraulic clutch 27 to increase the clutch pressure. arise. Therefore, part of the torque to the front drive shaft 7 is transferred to the rear drive shaft 1 by the hydraulic clutch 27.
1 and is added to increase the torque on the rear wheel side. In this manner, under these driving conditions, torque split control is performed to increase rear wheel torque distribution in accordance with the rearward movement of the vehicle body load, thereby promoting improved traction. Furthermore, when the center differential input torque Ti is approximately zero, it goes without saying that the clutch pressure is zero no matter what the rear wheel torque distribution ratio SR is, and thereby the tight corner braking phenomenon is avoided. The torque split control patterns described above are summarized in the table below. Furthermore, if the duty signal for clutch control is no longer output due to a failure of the control unit 50 or the like, the duty ratio on the input side of the solenoid valve 34 in the hydraulic unit 30 becomes 0%. Therefore, the duty pressure acting on the clutch control valve 36 reaches its maximum value, and the hydraulic pressure supplied to the hydraulic clutch 27 drains through the clutch control valve 36, causing the hydraulic clutch 27 to no longer generate torque. The wheels return to the initial torque distribution state by the center differential device 20 in which the amount of torque movement is zero. Therefore, as in the case of steady running, it becomes possible to free the center differential device 20 and smoothly turn the vehicle. Although one embodiment of the present invention has been described above, it can be applied to other than hydraulic clutches, and if the characteristics of the solenoid valve are opposite to those of the embodiment, the supply and discharge of the clutch control valve may be reversed.

【Effect of the invention】

As described above, according to the present invention, in a four-wheel drive vehicle with a center differential, active torque split control is performed under steady, acceleration, and cornering driving conditions, so that the optimal Power performance can be obtained. Since the clutch torque of a split clutch that moves torque becomes zero in the event of a failure of the control unit, etc., differential lock caused by the clutch is avoided, and the initial torque distribution by the center differential device ensures reliable driving performance with safe and smooth turning. Ru. Further, it is possible to prevent club clutch heat generation, deterioration of running performance, etc. due to excessive torque of the clutch.

[Brief explanation of the drawing]

Fig. 1 is a block diagram schematically showing an embodiment of the torque split control device of the present invention, Fig. 2 (a) is a circuit diagram of the hydraulic unit, (b) is a hydraulic characteristic diagram of the same, and Fig. 3 is a diagram of the control unit. The block diagram and Figure 4 are various characteristic diagrams. 2... Torque converter, 20... Center differential device, 25... Torque split device, 27... Hydraulic clutch, 30... Hydraulic unit, 34... Duty solenoid valve, 36... Clutch control valve, 50・
... Control unit, 62... Manipulated variable setting section Patent applicant: Fuji Heavy Industries Co., Ltd. Agent: Patent attorney: Makoto Kobashi Ukiyo Patent attorney: Susumu Murai No. 4 (b) Engineering: Jjiji 14*f:, So Ne Diagram (C) (d) Kutsugu H ball

Claims (2)

[Claims] (1) A center differential device is provided in the middle of the drive system to distribute power to the front and rear wheels with a predetermined torque distribution, and the center differential device has a split clutch with variable clutch torque.The four wheels are connected to each other by bypassing the torque split device. The drive vehicle has a sensor that detects various information and a control unit that inputs and processes the signals of the sensor, and the clutch control signal of the control unit controls the torque of the split clutch and the torque distribution to the front and rear wheels. The four-wheel drive is characterized in that the circuit is configured such that the torque of the split clutch is zero when the clutch control signal is not output, and the clutch torque is increased in response to an increase in the output of the clutch control signal. Car torque split control device. (2) A patent claim characterized in that the split clutch is a hydraulic clutch equipped with a hydraulic unit, and when the clutch control signal from the control unit is not output, the hydraulic pressure supplied to the hydraulic clutch is drained by the hydraulic unit. range 1
Torque split control device for a four-wheel drive vehicle as described in 2.