JPH01111535A - Torque split controller for four-wheel-drive car - Google Patents

Abstract

PURPOSE:To enable a car to be safely parked in a torque split device provided to bypass a center differential gear by locking one of front and rear wheels to P range of an automatic transmission end locking the other of front and rear wheels with the split clutch. 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 signal of sensors 40-46 for detecting various information controls the clutch torque and the torque distribution to front and rear wheels. When the clutch controlling signal is then not generated due to failures of 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 differentitial gear 20. Thus, the safety, smooth turning property or the like are ensured.

Description

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

The present invention relates to a torque split control device that actively controls torque distribution between front and rear wheels depending on driving conditions in a full-time four-wheel drive vehicle equipped with a center differential device, and specifically relates to parking lock control.

[Conventional technology]

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 cornering, ensuring smooth cornering performance with 4ti+ 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. In other words, when driving straight ahead, accelerating, or decelerating, if torque split control is performed according to the vehicle's weight distribution between the front and rear wheels, the driving force distribution between the front and rear wheels will be optimally adapted to the vehicle's weight distribution. Therefore, the effect of traction control can be obtained. When turning, if you control the torque split depending on the situation, the Flocito engine front drive (FF
) While suppressing the understeer tendency of cars and the oversteer tendency of front engine rear drive (PR) cars, it is possible to obtain optimal turning performance in consideration of stability and maneuverability. 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-wheel drive vehicle that can actively and variably control such a torque split, there is still room for the development of other systems. Additionally, an optimal electronic control system for achieving torque splitting is being developed. 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]

By the way, in the conventional prior art described above, since there is only a center differential device, only one torque distribution ratio is determined by it. Further, the control system is a 2.4-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.
An object of the present invention is to provide a torque split control device for a four-wheel drive vehicle with a center differential, which electronically controls torque split control in an i&appropriate manner and further ensures parking lock.

[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 information on M, and a control unit that inputs and processes the signal of the sensor, and uses a clutch control signal of the control unit to control the torque of the split clutch. In addition, the circuit is configured to control torque distribution to the front and rear wheels, and a parking lock means is attached to the output side of one of the front and rear wheels from the center differential device, and the control unit is configured to increase the pressure of the split clutch in the parking range. It has a correction section and is configured to lock the front and rear wheel drive shafts in a parking range while the engine is operating.

[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. Then, while the engine is running, the automatic transmission enters parking (
When shifted to the P) range, the parking lock means locks one of the front and rear wheels, and the split clutch also locks the center differential device and the other of the front and rear wheels. Thus, in the present invention, it is possible to improve performance during driving through active torque split control and ensure safety when parking with a center differential.

【Example】

Embodiments of the present invention will be described below based on the drawings. Referring to FIG. 1, an outline of the torque split control device of the present invention will be described. First, let's talk about a drive system for a four-wheel drive vehicle with a center differential and torque split control that is 1 ay1 with a front engine and equipped with an automatic transmission with a torque converter.
A torque converter 2° and an automatic transmission 3 are arranged in the longitudinal direction of the vehicle and are coupled 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. A pinion 23 that meshes with the 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. It is further connected to a front drive shaft 7 parallel to the output shaft 4 via a reduction gear 6, and this front drive shaft 7 connects to left and right front wheels 10L, I via a front differential device 8° axle 9.
Transmission configured to OH. 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 above reduction gear 5.6
is also a component in this case, and its gear ratio is set to, for example, “1”.
'', and the gear ratio of the gear 28□29 is set slightly smaller than that. Also, 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, the input 1-lux of the center differential device 20 is Ti, and the center differential device 20
If the front side distribution ratio is γ, then the transmitted torque of the front drive shaft 7 is γ・Ti, and the transmission torque of the rear drive shaft 11 is γ・Ti.
The torque of is distributed to (1-γ)·Ti. 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・T
i −Tc TR=(1−γ)·Ti +KTc. In this way, as the clutch torque Tc changes, the distribution ratio of the front torque TF changes continuously below the distribution ratio in the center differential device 20, and the rear torque TR
The distribution ratio changes continuously to be higher than the distribution ratio in the center differential device 20, and a torque split effect is exerted. In addition, as a wheel lock for P range of automatic transmission A3,
For example, parking gear 1 is attached to front drive shaft 7 on the front wheel side.
5a and a ball 15b are provided to mechanically lock the front wheels. Next, regarding the electronic control system of the torque split, there are rotational speed sensors 40L for the left and right front wheels and the rear wheels. 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. do. 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 produces a constant pilot pressure in the oil passage 33 while maintaining 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 Figure 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 changes. The clutch pressure also increases as the clutch pressure increases.The broken line in Fig. 2 is the characteristic of duty pressure.In Fig. 3, the control unit 50 will be described.First, the left and right front wheel rotation speed N of the rotation speed sensors 40L and 40R will be described.
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 unit 51. Rear wheel speed calculation unit 52
The front and rear wheel speeds NF and NR of are input to the wheel speed calculation unit 53,
The four-wheel average wheel speed N is calculated by N=(NF-1-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 vehicle speed ■ of the vehicle speed calculation unit 54 are 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 torque distribution ratio of the rear wheels is determined by the vehicle speed V 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 steering angle is relatively large at medium speeds, the rear wheel torque distribution ratio S is
R is set large, and in the region of high speed and small steering angle, the rear wheel torque distribution ratio SR is set small to emphasize vehicle stability, and 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. SR correction is not performed. Furthermore, during acceleration that generates acceleration G, 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
The wheel speed N of No. 3, the engine rotation speed Ne, and the gear position Gr of the gear position sensor 46 are determined by the torque converter rotation ratio calculation unit 5.
8, and calculate backwards using the number N and gear G to find the turbine rotation speed Nt which is the output side of the torque converter 2, and calculate the rotation ratio Rw with the engine rotation speed Ne which is the input side of the torque converter 2. This rotation ratio 1'l, which is calculated by Rw=Nt/Ne, is input to the torque converter torque ratio calculation section 59, and the torque ratio R[ is calculated from the characteristics shown in FIG. 4(C).Then, the engine torque Te,
) Torque ratio Rt of the torque converter. 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 follows: SR=TR/(TF +TR). Therefore, the above-mentioned front side distribution ratio γ. Substituting the equations for input torque Ti, clutch torque Tc, and gear ratio into the above equation results in Tc = f(SR, Ti), and clutch torque Tc changes as the rear wheel torque distribution ratio SR and input torque Ti increase. The value increases. Also,
The relationship between clutch torque Tc and clutch pressure PC has specific characteristics depending on parameters such as the number of clutch plates constituting the hydraulic clutch 27 and the friction coefficient, and as shown in FIG. 4 ((1), Pc = g (Tc) Then, this clutch pressure pc is input to the manipulated variable setting section 62, and using the characteristics shown in FIG. Furthermore, a parking lock control means is added to the torque split control system. That is, in a drive system with a center differential, a mechanical parking lock means 15 is provided on the front wheel side as already mentioned. Even if the center differential device 20 is provided, the center differential device 20 is in a -free state.Therefore, when the engine is operated in the P range, the automatic transmission 3 rotates the output shaft 4 even a little with the flexible bonds of each part, even though the planetary gear is in a free state. This is input to the center differential device 20 and further transmitted to the rear wheels.For this reason, normally the rear wheels 14L,
The above rotation is locked due to the ground resistance of 14R, but
For example, if the rear wheels 14L and 14R are jacked up, there will be no load and a phenomenon will occur where they spin. Therefore, a correction section 63 is added to the output side of the clutch pressure calculation section 61, and corrects the clutch pressure to a high oil pressure by the ON signal of the P range switch 64, and adjusts the hydraulic clutch 27 and gear 2.
8.29 connects the rear drive shaft 11 from the center differential device 20 to the rear wheel side to the front drive shaft 7 locked by the parking lock means 15, thereby making the center differential device 20 lockable. 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 3 via the torque converter 2, and the shifting power is output. is transmitted to the carrier 24 of the center differential device 20. And ring gear 22 and sun gear 21
Accordingly, the torque is distributed to the front and rear wheels at a ratio of 60:40, for example, in accordance with the static load distribution to the wheels of the vehicle. The power beam from the ring gear 22 is the reduction gear 5
, 6° front drive shaft 7. The power from the sun gear 21 is transmitted to the front wheels 10L and IQR via the front differential device 8 and the like to the rear drive shaft 11. The information is transmitted to the rear 114L and 14R via the rear differential device 12 and the like, resulting in full-time 4mK'A shift driving with a center differential. At this time, the hydraulic clutch 27 of the torque split device 25
rotates with a difference in rotation caused by the gear ratio between the reduction gears 5, 6 and the gears 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 Gr. Furthermore, engine speed Ne, wheel 3! ! The center differential input torque Ti is calculated using JN, the rotation ratios R and W of the torque converter 2 based on the speed change lGr, and the torque ratio Rt. Therefore, during normal driving, the target torque distribution ratio determination unit 5
5, the rear wheel torque distribution ratio SR is set to 4th depending on the steering angle λ and the vehicle speed V.
Various determinations are made based on the pattern 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 V and the steering angle λ decrease, the rear wheel torque distribution also decreases accordingly, and thus the rear wheel torque distribution is variably torque split controlled according to the turning state. For this reason, when turning with four-wheel drive, the slip of the front and rear tires always maintains a large traction coefficient with the road surface, promoting reliable turning along the target turning radius. In the pattern shown in 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, and sportier driving becomes possible. Further, especially in steady driving where the vehicle body acceleration G is approximately zero when traveling straight, the target rear wheel torque distribution ratio SR is held at 40% of the torque distribution ratio by the center differential device 20. Therefore, since the rear wheel moving torque amount is zero in the clutch pressure calculation unit 61, the clutch pressure pc=0. Therefore, a signal indicating a duty ratio of 0% is output from the operation amount setting section 62 to the hydraulic unit 3.
0 to the solenoid valve 34, the duty pressure is maximized, and the hydraulic clutch 27 is drained by the clutch control valve 36, whereby the oil pressure and torque of the hydraulic clutch 27 become zero. In this manner, under such 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. Due to this, the clutch pressure Pc becomes a value larger than that 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 way, 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 reducing traction improvement. 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, when shifting to the P range while the engine is running, the parking lock means 15 operates to mechanically lock the front wheels together with the front drive shaft 7. In addition, the correction section 6
By inputting the ON signal of the P range switch 64 into the hydraulic unit 3 and correcting it to increase the clutch pressure, the hydraulic unit 3
0, the hydraulic pressure of the hydraulic clutch 27 temporarily reaches a substantially maximum value, and this clutch pressure connects the front drive shaft 7 and the rear drive shaft 11, and also connects the center differential device 20.
lock. Therefore, the locking action of the parking lock means 15 extends to the rear wheels as well. On the other hand, when the vehicle is shifted to the D range of the driving range, the actions of the parking lock means 15 and the correction section 63 are automatically released. Although one embodiment of the present invention has been described above, the parking lock means 15 may be provided on the rear wheel side, or may be provided at any location on the two output sides of the center differential device 20.

【Effect of the invention】

As described above, according to the present invention, in a four-wheel drive vehicle with a center differential, lux split control is applied to active 1 under steady, acceleration, and turning driving conditions, so 4fil
Optimum power performance that maximizes the performance of the iii drive can be obtained. In the P range, both the front and rear wheels are locked, so even if the output side of the automatic transmission rotates due to friction when the engine is running, the wheels are prevented from rotating during jack-up, ensuring safety. The parking lock means can only be used on one of the front and rear wheels, and the front and rear wheels are locked by clutch torque control.
The structure is simplified.

[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. 15... Parking lock means, 20... Center differential device, 25... Torque split device, 27...
・Hydraulic clutch, 30...Hydraulic unit, 50...
Control unit, 55...Target torque distribution ratio determination section, 6
3... Correction section, 64... P range switch patent applicant Fuji Heavy Industries Co., Ltd. agent Patent attorney Makoto Kobashi Ukiyo Patent attorney Susumu Murai (b) (C) (d) Shoes lubba H ball qan −

Claims (1)

[Scope of Claims] 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 a torque split device having a split clutch with variable clutch torque is connected to the center differential device by bypassing the center differential device. A four-wheel drive vehicle has a sensor that detects various information, a control unit that inputs and processes the signals of the sensor, and uses a clutch control signal from the control unit to control the torque of the split clutch as well as the torque to the front and rear wheels. The circuit is configured to control the distribution, and a parking lock means is attached to the output side of one of the front and rear wheels from the center differential device, and the control unit has a correction section that increases the pressure of the split clutch in the parking range, A torque split control device for a four-wheel drive vehicle, characterized in that the front and rear wheel drive shafts are locked in a parking range while the engine is running.