JPH04113222U - Torque distribution control device for 4-wheel drive vehicles - Google Patents

Abstract

(57) [Summary] [Purpose] In torque distribution control, which controls torque distribution between front and rear wheels using differential limiting torque,
To provide a torque distribution control device for a four-wheel drive vehicle capable of optimally controlling differential limiting torque by determining turning on a road and a low μ road. [Configuration] Center differential device 20 and a differential limiting device 27 that limits the differential between the center differential device 20 and controls torque distribution between the front and rear wheels.
In a four-wheel drive vehicle with a center differential device, a control unit 50 that has various sensors and a lateral acceleration sensor 45 that detects the lateral acceleration Gs of the vehicle, and that controls the differential limiting device 27 is configured to detect at least the lateral acceleration Gs. Gs
A turning state determination means 57 determines whether the turning state is on a high μ road or a low μ road based on the differential limiting torque Tc in the case of turning on a high μ road.
A correction means 58 is provided for correcting the differential limiting torque Tc so as to reduce the differential torque Tc and increase the differential limiting torque Tc when turning on a low μ road.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is equipped with a center differential device and uses differential limiting torque to In 4-wheel drive vehicles that control torque distribution between the rear wheels, the differential when turning is determined by lateral acceleration. The present invention relates to a torque distribution control device that corrects limited torque.

0002

[Conventional technology]

In full-time four-wheel drive vehicles equipped with a center differential, A wet multi-disc hydraulic clutch is installed in the center differential device, and this clutch Differential limiting torque is generated by the pressure. Then, throttle opening, vehicle speed, gear position The differential limiting torque is controlled according to the driving force determined from Furthermore, when accelerating on a low μ road If the rotation difference between the front and rear wheels increases and the front or rear wheels slip, the differential limiting torque will increase. A method has been proposed in which wheel spin is prevented by increasing control of the wheel speed.

0003 In torque distribution control between the front and rear wheels using such differential limiting torque, When making a sharp turn, the differential limiting torque causes tight corner braking, which Setting the differential limiting torque low to prevent this will improve acceleration and steering stability on low μ roads. Sexuality will deteriorate. In addition, in order to improve turning performance on high μ roads, the torque of the rear wheels is increased. In a rear wheel bias system with a large distribution, if the differential limiting torque is controlled to a large extent, When turning, internal circulation torque reduces rear wheel torque and worsens turning performance. Therefore, the same Even when turning, there are cases where tight corner braking occurs easily on high μ roads and slippage on low μ roads. It is desirable to determine the cases where a drop is likely to occur and to control each case optimally.

0004 Therefore, conventionally, regarding torque distribution control using the above-mentioned differential limiting torque, for example, There is a prior art disclosed in JP-A-61-70250. Here, the differential between the left and right wheels is In the Renshal device, a friction clutch is installed between the differential case and the side gear. Ru. If the lateral acceleration acting on the vehicle exceeds the set value, the friction clutch This reduces the locking force and suddenly changes the tendency from understeer to oversteer when turning. It has been shown to prevent changes.

[0005]

[Problem that the idea aims to solve]

By the way, in the prior art mentioned above, the torque distribution of the left and right wheels is affected by lateral acceleration. Therefore, it is also possible to control the torque distribution between the front and rear wheels as in the present invention. It cannot be adapted to. Further, the differential limiting torque is controlled only in the decreasing direction.

[0006] The present invention was devised in view of this point, and its purpose is to In torque distribution control, which controls the torque distribution between the front and rear wheels using a limited torque, lateral It determines turning on high μ roads and low μ roads based on speed, and optimally sets differential limiting torque for each. An object of the present invention is to provide a torque distribution control device for a four-wheel drive vehicle that can be controlled.

[0007]

[Means to solve the problem]

In order to achieve the above object, the torque distribution control device for a four-wheel drive vehicle of the present invention is Limits the differential between the tar differential device and center differential device In addition, the center disk has a differential limiting device that controls torque distribution between the front and rear wheels. In 4-wheel drive vehicles with differential devices, various sensors and lateral acceleration of the vehicle are used. The control unit, which has a lateral acceleration sensor that detects the At least a turning state determination means for determining whether the turning state is on a high μ road or a low μ road based on lateral acceleration. , when turning on a high μ road, reduce the differential limiting torque, and when turning on a low μ road, reduce the differential limiting torque. A correction means is provided for correcting the limit torque to increase it.

[0008]

[Effect]

Based on the above configuration, when the vehicle is running in four-wheel drive, the control unit at least Turning conditions are determined based on lateral acceleration, and sharp turns on high μ roads with large lateral acceleration In this case, the differential limiting torque is corrected to decrease and the tight corner braking phenomenon is avoided. In addition, when turning on a low μ road with small lateral acceleration, the differential limiting torque is increased and added. This will improve speed, etc.

[0009]

【Example】

Hereinafter, embodiments of the present invention will be described based on the drawings. In Figure 2, the center Overview of the drive system of a full-time 4-wheel drive vehicle equipped with a differential device In other words, 1 is the engine, 2 is the clutch, 3 is the transmission, and the transmission output shaft 4 is input to the center differential device 20. center defale A front drive shaft 5 is output from the mechanical device 20 to the front, and a rear drive shaft 6 is output to the rear. , the front drive shaft 5 is connected to the left and right through the front differential device 7 and the axle 8. The rear drive shaft 6 has a propeller shaft 10 and a rear differential device 11. , are connected to the left and right rear wheels 13 via an axle 12 to form a transmission structure.

0010 The center differential device 20 is a compound planetary gear type, and is a variable A first sun gear 21 integrated with the speed gear output shaft 4, and a second sun gear 2 integrated with the rear drive shaft 6. 2, and a plurality of pinions 23 arranged around these sun gears 21 and 22. The first pinion gear 23a of the pinion 23 is connected to the first sun gear 21, and the second pinion gear 23a of the pinion 23 is connected to the first sun gear 21. The on-gear 23b meshes with the second sun gear 22, respectively. In addition, the transmission output A reduction drive gear 25 is rotatably provided on the shaft 4, and this drive A pinion 23 is pivotally supported on a carrier 24 that is integrated with a gear 25, and the drive gear 25 is It is configured to mesh with a driven gear 26 that is integrated with the front drive shaft 5.

[0011] On the other hand, the center differential device 20 is equipped with oil as a differential limiting device. A pressure clutch 27 is attached. This hydraulic clutch 27 includes, for example, a center disk. Immediately behind the differential device 20, the drum 27a is placed on the carrier 24, and the hub 27 is placed on the carrier 24. b are respectively coupled to the rear drive shaft 6 and arranged coaxially.

0012 Due to the configuration of this center differential device 20, the first sun gear 21 The input shift power is applied to the carrier 24 and the second sun gear 22 at a predetermined reference torque. Communicate through allocation. In addition, the difference in rotation between the front and rear wheels during turning is determined by the planetary rotation of the pinion 23. It absorbs more. Here, the standard torque distribution is between the two sun gears 21 and 22. and the two pinion gears 23a, 23b, and the four gear engagement pitch circles are free. will be set to . Therefore, the standard torque for front wheel torque TF and rear wheel torque TR is For example, it is possible to set the brake distribution eTs to be sufficiently biased toward the rear wheels, as shown below. Ru. eTs=TF:TR=34:66

[0013] In addition, if the vehicle is equipped with a front engine, the front wheel weight WF and rear wheel weight WR of the vehicle are For example, the static weight distribution ew is as follows. ew=WF:WR=62:38 Therefore, in the case of direct connection due to differential restriction of the hydraulic clutch 27, depending on this weight distribution, Torque is distributed unevenly to the front wheels. As a result of the above, the differential limiting torque of the hydraulic clutch 27 By controlling the torque distribution between the front and rear wheels, the standard torque distribution eTs with a biased weight on the rear wheels, This makes it possible to control the weight distribution ew of the front wheel bias over a wide range.

[0014] Next, the hydraulic control system of the hydraulic clutch 27 will be described. First, the transmission changes automatically. In the case of a high-speed engine, the hydraulic pressure of the oil pump 30 of the hydraulic control system is controlled by the regulator valve 31. It is configured using line pressure regulated by Therefore, the line pressure oil passage 32 is cracked. It communicates with the hydraulic clutch 27 via a control valve 33 and an oil passage 34. Also line pressure oil The passage 32 is connected to the solenoid by an oil passage 37 having a pilot valve 35 and an orifice 36. The duty pressure from the solenoid valve 38 is communicated with the idle valve 38 through the oil passage 39. It acts on the control side of the clutch control valve 33.

[0015] The solenoid valve 38 has a duty according to each running condition from the control unit 50. When a signal is input, it drains hydraulic pressure and generates duty pressure. The clutch control valve 33 is operated according to this duty pressure, and the hydraulic clutch 27 is operated. The differential limiting torque is variably controlled.

[0016] In FIG. 1, the unequal torque distribution control device of the present invention is applied to the above-mentioned four-wheel drive vehicle. The electronic control system of this embodiment will be described below. First, as input information, the rotation speed NF of the front wheel A front wheel rotation speed sensor 40 detects the rotation speed NR of the rear wheels, and a rear wheel rotation speed sensor 40 detects the rotation speed NR of the rear wheels. throttle opening sensor 41, throttle opening sensor 42 that detects throttle opening θ, transmission shifter A shift position sensor 43 detects the shift position and an engine speed sensor 43 detects the engine rotation speed Ne. It has a rotation sensor 44 and the like.

[0017] The control unit 50 is a vehicle speed detection section into which the front wheel rotation speed NF and the rear wheel rotation speed NR are input. 51, it has a front and rear wheel rotation ratio calculation section 52. In addition, the vehicle speed detection section 51 detects engine rotation. When the number Ne is above the set value, for example, the average value of the front wheel rotation speed NF and the rear wheel rotation speed NR The vehicle speed V is calculated by

[0018] The front and rear wheel rotation ratio calculation unit 52 calculates slip, steering, and other important matters in this control. Considering that running conditions and conditions such as slipping can be determined and detected based on the rotation ratio. This will be established with consideration given to this. Therefore, depending on the front wheel rotation speed NF and the rear wheel rotation speed NR, The rotation ratio eN is set as follows. eN=NF/NR

[0019] The control unit 50 also controls the vehicle speed V, the front and rear wheel rotation ratio eN, and the throttle opening. A normal mode determination unit 53 and a start mode determination unit 5 into which the θ and shift position signals are input. 4. It has a slip mode determination section 55.

[0020] The normal mode determination unit 53 determines the shift position of 1st to 4th forward speed or reverse speed, and The normal driving condition is determined by θ and V, and this mode determination signal is used to determine whether the differential A differential limit torque Tc is determined in a limit torque setting section 56. Torque in this case is set as an increasing function for θ and a decreasing function for V. That is, In the region where θ is small, torque Tc is reduced to prevent tight corner braking during large steering turns. In this case, the lower V is, the more torque Tc is increased to improve running performance. ing.

[0021] The start mode determination unit 54 determines that the rotation ratio eN is If it is determined that the vehicle is going straight ahead when the value is higher than a set value (for example, 1 to 1.1), the start run is determined. do. Then, based on this mode determination signal, the differential limit torque setting section 56 In this case, the torque Tc increases at a high level with respect to θ. It is set in a function.

[0022] The slip mode determination unit 55 determines whether the front wheels slip when the rotation ratio eN is equal to or higher than a set value. Rear wheel slip is determined when the value is less than a set value. And this slip judgment signal Then, the differential limiting torque setting section 56 calculates the torque using a map using θ and V as parameters. Determine the torque Tc. In this case, when the rear wheels slip, torque Tc is increased, but the front wheels In the case of slip, the torque Tc is set to decrease.

[0023] Furthermore, the lateral acceleration Gs of the lateral acceleration sensor 45 attached to the vehicle body and the rotation ratio eN are It has a turning state determination section 57 to which a signal is input. And the value of lateral acceleration Gs is large If this is not the case, judge the sharp turn on the high μ road and reduce the correction coefficient k using the map in Figure 3. If the value of lateral acceleration Gs is small in . This correction coefficient k is determined by a correction section 58 on the output side of the differential limit torque setting section 56. It is corrected by multiplying the value of Tc. The differential limiting torque Tc set in this way is It is input to the duty ratio converter 59 and converted using a conversion map for torque Tc. The signal of this duty ratio D is sent to the solenoid via the drive unit 60. It is configured to be output to the noid valve 38.

[0024] Next, the operation of this embodiment will be explained. First, when the vehicle is running, the power of engine 1 is is input to the transmission 3 via the clutch 2, and the shifting power is sent to the center differential input to the first sun gear 21 of the control device 20. Here, the center differential The reference torque distribution is set to be biased toward the rear wheels depending on the specifications of each gear of the gear mechanism 20. With this torque distribution, the power is distributed to the carrier 24 and the second sun gear 22 and the power is output. be done.

[0025] On the other hand, at this time, the control unit 50 of the electronic control system includes the front wheel rotation speed NF, the rear wheel rotation speed, The signals of rotation number NR, shift position, throttle opening θ, and lateral acceleration Gs are input, and the vehicle The speed V and the front and rear wheel rotation ratio eN are calculated. These signals are then sent to each mode determining section 5. 3 to 55 are input to the turning state determination section 57 to determine each driving condition of normal, start, and slip. , the turning state is determined.

[0026] Therefore, when starting on a high μ road, the mode determination unit 54 makes a determination, and in this case, The high torque Tc is set according to the map, and this duty signal is applied to the solenoid valve 38. Enter. Then, high duty pressure PD is applied from the solenoid valve 38 of the hydraulic control system. Acts on the clutch control valve 33, and accordingly increases the amount of oil supplied to the hydraulic clutch 27, causing the clutch to shut down. The latch pressure Pc increases and a predetermined high differential limiting torque Tc is generated. this Therefore, the differential is limited in the center differential device 20, and the differential limiting torque is Power is bypassed and transmitted from the second sun gear 22 to the carrier 24 side according to the torque Tc. Then, the torque distribution changes from being biased to the rear wheels to being biased to the front wheels. And from carrier 24 Power is transmitted to the front wheel side and from the second sun gear 22 to the rear wheel side, respectively, and the power is transmitted to the point P2 in FIG. The vehicle runs in four-wheel drive with unequal torque distribution, and the front and rear wheels provide better start-up acceleration. I will do it.

[0027] After starting, the rotation speeds NF and NR of the front and rear wheels become approximately equal, and the rotation ratio eN falls below the set value. Then, the determination unit 53 determines the normal mode. At this time, 1st gear or reverse speed In low gear, a relatively low torque Tc is set based on the map, and hydraulic control is applied based on this. As a result, the differential limiting torque Tc of the hydraulic clutch 27 is controlled to be low. For this reason The torque of the front and rear wheels is determined by the biased weight of the rear wheels near point P1 in Fig. 4, approximately according to the standard torque distribution. Torque distribution makes it FR-like even though it is a 4-wheel drive, and has good turning and maneuverability. become. In this case, especially when turning in a region where the throttle opening θ is small, The interdifferential device 20 becomes almost free and absorbs the rotational difference ΔN between the front and rear wheels. It is possible to turn freely while stowing away.

[0028] In addition, when starting or driving in the normal mode mentioned above, the throttle opening θ is large and the load is high. Under load conditions, the differential limiting torque Tc is controlled to increase, so the front and rear wheels tend to be directly connected. This fully demonstrates its running performance. On the other hand, especially when steering under such driving conditions, Then, the larger the steering is due to the rotation ratio eN, etc., the more the differential limiting torque Tc temporarily decreases and compensates. Therefore, it is possible to turn without tight corner braking. It becomes possible to

[0029] Next, when driving on a low μ road, a slip mode determination unit 55 determines whether or not there is a slip. When a normal slip occurs, the rear wheels are always distributed unevenly with the weight being biased towards the rear wheels. The vehicle will skid first, and the four wheels will be prevented from slipping. When this rear wheel slips, The differential limiting torque Tc is controlled to a high level by the The differential movement of the mechanical device 20 is limited, and the torque of the front wheel is unbalanced as shown at point P3 in FIG. This will lead to a shift to bulk allocation. Conversely, if it is determined that the front wheels are slipping, differential braking will be applied. By reducing the limit torque Tc, the torque distribution is controlled to be biased toward the rear wheels. The wheel drive force on the non-slip side is controlled to constantly increase to prevent slipping. It will be done.

[0030] Furthermore, when turning, in addition to the rotation ratio eN mentioned above, the lateral acceleration Gs changes the road surface, vehicle speed, etc. The turning state is determined based on the relationship. Therefore, if a large lateral acceleration Gs is generated, The differential limiting torque is determined based on the correction coefficient k of the turning state determination unit 57 by determining a sharp turn on a high μ road. The torque Tc is corrected to decrease. For this reason, the torque Tc during turning decreases and the tight corner This reduces the nabraking phenomenon, making it possible to turn smoothly. Torque distribution reduces understeer tendency and improves turning performance.

[0031] On the other hand, if the lateral acceleration Gs is smaller than normal, differential braking is performed by determining turning on a low μ road. The limit torque Tc is corrected to increase. Therefore, the torque distribution is almost directly connected, resulting in improved acceleration. , maneuvering stability, etc. will be fully demonstrated. The above is a description of the embodiments of the present invention. However, it is not limited to this.

[0032]

[Effect of the idea]

As explained above, according to the present invention, the center differential device is provided. Control that controls the torque distribution between the front and rear wheels using the differential limiting torque in a four-wheel drive vehicle In the system, the turning conditions of high μ road and low μ road are judged based on lateral acceleration and controlled separately for each. Therefore, the differential limiting torque during these turns can be optimally controlled. A sharp turn on a high μ road Since the differential limiting torque is corrected to decrease in the rotation, the tight corner braking phenomenon is ensured. can be avoided. When turning on a low μ road, the differential limiting torque is corrected to increase, so acceleration is improved. etc. can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an electronic control system of an embodiment of a torque distribution control device for a four-wheel drive vehicle according to the present invention.

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

FIG. 3 is a diagram showing correction coefficients for lateral acceleration.

FIG. 4 is a diagram showing a control state of unequal torque distribution.

[Explanation of symbols]

1 engine 9 Front wheel 13 Rear wheel 20 Center differential device 27 Hydraulic clutch for differential limiting 33 Clutch control valve 38 Solenoid valve 45 Lateral acceleration sensor 50 Control unit 56 Differential limit torque setting section 57 Turning state determination section 58 Correction section

Claims (1)

[Scope of utility model registration request] Claim 1: A four-wheel drive vehicle with a center differential device that includes a center differential device and a differential limiting device that limits the differential of the center differential device and controls torque distribution between the front and rear wheels. , a control unit that has a lateral acceleration sensor that detects the lateral acceleration of the vehicle and that controls the differential limiting device includes a turning state determination means that determines the turning state of a high μ road and a low μ road based on at least the lateral acceleration; Torque distribution control for a four-wheel drive vehicle, characterized by comprising a correction means for reducing the differential limiting torque when turning on a road and increasing the differential limiting torque when turning on a low μ road. Device.