JPH01113667A - Detecting apparatus of slip - Google Patents

Abstract

PURPOSE:To enable the highly precise detection of a two-wheel slip of front or rear wheels, by a method wherein rotational accelerations of front and rear wheels are determined by differentiating the speeds of the front and rear wheels and compared with a common vehicle body acceleration in a four-wheel drive vehicle. CONSTITUTION:A front-wheel speed NF and a rear-wheel speed NR are calculated in calculators 54 and 55 on the basis of the number of rotations respectively and inputted to acceleration calculators 56 and 57. In the calculators 56 and 57 of the accelerations of front and rear wheels, accelerations GF and GR are determined by differentiating the front-wheel and rear-wheel speeds NF and NR. The accelerations GF and GR of the front and rear wheels are inputted, together with a vehicle body acceleration G, to slip detectors 58 and 59 of the front and rear wheels. In the front-wheel slip detector 58 an acceleration difference DELTAGF between the front wheels and a vehicle body and a set value DELTAGS are compared with each other, and when the front-wheel acceleration GF exceeds the vehicle body acceleration G by the set value DELTAGS or above in rotation, it is determined as the front-wheel slip. The rear-wheel slip is detected likewise in the rear-wheel slip detector 59 separately.

Description

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

The present invention relates to a slip detection device used for traction control and the like to prevent wheel slip in a full-time four-wheel drive vehicle equipped with a center differential device. τConventional Technique vIi1 Regarding slips in four-wheel drive vehicles with a center differential, there are two-wheel slips on one of the front and rear wheels and four-wheel slips on both. Here, in the case of two-wheel slip, the slip can be eliminated by differentially locking the center differential, but since the differential limit is uniquely determined, turning performance deteriorates significantly. Furthermore, when the differential is locked, it becomes impossible to determine the slip state of the wheels, and it is impossible to automatically control the release of this flat differential lock. Therefore, such a differential lock is generally operated manually during an emergency escape or when driving on a special low μ road such as a snowy road. Therefore, in recent years, with regard to the above-mentioned two-wheel slip, it has been considered to perform torque split control so as to increase the torque distribution to the grip side wheel. Since such torque split control avoids 2VR slip by distributing torque between the front and rear wheels, the turning performance of the center differential is not lost, driving force is secured, and traction is effective. Also,
In this case, since the rotation difference between the front and rear wheels is always feedback-controlled to the target value, normal control is immediately activated when the two wheels are in a state of slipping out. , :Here, when the above-mentioned torque split control for two-wheel slip is performed, the torque is distributed as much as possible without causing two-wheel slip, and if slip occurs, then 4
The more accurate the torque split control is, the less two-wheel slip will occur and the marginal performance will be improved, but it will be difficult to control when all four wheels slip at the same time. This cannot be resolved, and the only option is to rely on traction control, which reduces the power by lowering the engine output. In this way, the torque split and traction control of a four-wheel drive vehicle is performed in relation to wheel slip.
Slip detection is required. Here, since the four wheels of a 4@drive vehicle are drive wheels and there is a possibility of slipping,
This car! F! Detecting the slip of one of the front and rear wheels, 4@, based only on the speed will result in a large error, so it is necessary to devise ways to improve the detection accuracy. Conventionally, regarding slip detection of a 4W drive vehicle, there is a prior art, for example, disclosed in Japanese Utility Model Application Laid-Open No. 59-99827. Here, it is shown that the vehicle includes a vehicle speed sensor that detects the speed of the vehicle and a tire rotation sensor that detects the rotation of the tires, and that tire slippage is detected based on these vehicle speeds and tire rotations.

[Problems to be solved by the invention]

By the way, the vehicle speed sensor of the above-mentioned prior art is, for example,
If it is attached to the machine output side and the vehicle speed is calculated from its rotation, the value will deviate greatly from the actual moving speed of the vehicle body when the drive wheels slip. SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a slip detection device capable of detecting two-wheel slip on one of the front and rear wheels of a four-wheel drive vehicle with high accuracy.

[Means to solve the problem]

In order to achieve the above object, the present invention focuses on the fact that front and rear wheel slip can be absolutely detected based on the rotational acceleration state of the front wheels and rear wheels with respect to a common vehicle body acceleration. Therefore, in the slip detection of a 4VA drive vehicle, there is provided a front and rear wheel acceleration calculation section that differentiates the front and rear transport speeds, and a means for detecting vehicle body acceleration. 2' of one of the front and rear wheels
The device is configured to detect M slips.

[For production]

Based on the above configuration, the rotational acceleration of the front and rear wheels relative to the vehicle body acceleration is detected separately, and when the difference between the vehicle body acceleration and the rotational acceleration of the front M or rear wheel becomes large, the front wheel or
& Wheel slip can be detected independently. Thus, according to the present invention, it is possible to accurately detect the slip of the front and rear wheels in absolute terms.

【Example】

Embodiments of the present invention will be described below based on the drawings. In Fig. 1, a 4Va with a center differential and capable of torque split and traction control to which the present invention is applied is shown.
The drive system for the driving vehicle is a front engine, vertically mounted, and equipped with an automatic transmission with a torque converter.The drive system includes an engine 1, a torque converter 2. An automatic transmission 3 is arranged in the longitudinal direction of the vehicle and connected to enable power transmission. The output shaft 4 of the automatic transmission a3 is input to the center differential device fi20, and the center differential device 20 is provided with a torque split device F25 by bypass. The center differential device 20 is of a grain 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. Furthermore, two sun gears 21 on the output side from the center differential device 20. The ring gear 22 is rotatably provided from the large-diameter ring gear 22 to the transmission output shaft, or is connected to the front drive shaft 7 parallel to the output shaft 4 via the reduction gears 5 and 6. Front differential device8. Left and right front wheels 10L via the axle 9,
Transmission is configured to IOH. On the other hand, the small diameter sun gear 21 is connected to the rear drive shaft 11, and this rear drive shaft 1
1 is the rear differential device 12. Left and right rear wheels 14L via the axle 13 and the like. 14R transmission configuration. 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 connected to the rear drive shaft 11 via a pair of gears 28 and 29.
It will be communicated to you. Here, the reduction gear 5,
6 is also a component in this case, and its gear ratio is, for example, “
1", and the gear ratio of gears 28 and 29 is set slightly smaller than that. Furthermore, the hydraulic clutch 27 is configured to be able to generate clutch torque by supplying hydraulic oil from the hydraulic unit 30. 27, the drum 27b has a slightly lower rotational speed difference than the hub 27a. Therefore, when clutch pressure is applied to the hydraulic clutch 27 to generate clutch torque, the rotational speed is shifted from the front wheel side of the hub 27a to the rear wheel side of the drum 27b. The torque distribution between the front wheels and the rear wheels is varied by shifting the torque according to the clutch pressure, etc. That is, the input torque of the center differential device fi 20 is set to 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)·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
-'rc TR=(1-7)-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. Further, an actuator 16 such as a motor is attached to the throttle valve 15 of the engine 1, and this actuator 1
6 enables electronic control of the throttle valve opening. As an electronic control system, a front wheel rotation speed sensor 40L is attached to the left and right front wheels 10L and 10R to detect their rotation speed,
40R, rear wheel rotation speed sensors 411, 41R similarly attached to the left and right rear wheels 141.14H, and a vehicle body acceleration sensor 42.42 attached near the center of gravity of the vehicle body to detect acceleration in the longitudinal direction of the vehicle. Furthermore, it has an accelerator opening sensor 43 and a throttle opening sensor 44, and these sensor signals are input to a control unit 50. The control unit 50 processes the sensor signal to determine the slip state, outputs a clutch pressure control signal for torque splitting to the hydraulic unit 30,
A throttle control signal for traction is output to the actuator 16. In FIG. 2, the control unit 50 will be described. The control unit 50 includes a slip detection section 51. It has a torque split control section 52 and a traction control section 53 that reduces power. The slip detection section 51 includes rotation speed sensors 40L and 40R.
It has a front wheel speed calculating section 54 to which the left and right front wheel rotational speeds NFL and NFR are input, and a rear wheel speed calculating section 55 to which the left and right rear wheel rotational speeds NRL and NRR of the rotational speed sensors 411 and 41R are input. and front wheel speed calculation section 54. The rear wheel speed calculation unit 55 calculates the front and rear wheels 3.
1[NF, NR are calculated as follows. NF = (NFL+NFR) /2 NR = (NRL+-NRR) /2 The above front and rear wheel speeds NF and NR are input to the front wheel acceleration calculation unit 56° and the rear wheel acceleration calculation unit 57, and the front and rear wheel speeds NF and NR are differentiated. Acceleration GF and OR are calculated as follows. CF = dNF/dt, GR = dNR/dt, and these front and rear wheel accelerations GF and GR are detected by the front wheel slip detection unit 5 along with the vehicle body acceleration G of the vehicle body acceleration sensor 42.
8. The signal is input to the rear wheel slip detection section 59. The front wheel slip detection unit 58 calculates the difference ΔGF between the front wheel acceleration GF and the vehicle body acceleration G by ΔGF = GF - G,
If this acceleration difference ΔGF is the set value ΔGS, ΔOF>Δ
Slip is detected in the case of GS. Similarly, the rear wheel slip detection unit 59 calculates the acceleration difference ΔGR by ΔGR=GR−G, and detects a slip when ΔGR>ΔGs. These slip signals are input to the torque split control W section 52, and in the case of front wheel slip, they are input to the front INaIII together with the clutch pressure of the hydraulic clutch 27.
The amount of torque transferred between the rear wheels is increased to distribute the torque closer to the rear wheels, and in the case of rear wheel slip, the clutch pressure is lowered to control the torque distribution closer to the front wheels.This clutch pressure control signal is sent to the hydraulic clutch. The clutch pressure is output to a hydraulic unit 30 which supplies clutch pressure to the clutch pressure 27. Further, since the above-mentioned front and rear wheel slips are detected individually, the four-wheel slip detection section 60 detects that they occur simultaneously and detects the four-wheel slip. This 4
A wheel slip or grip signal is input to the traffic control section 53, which reduces the throttle opening when slipping and controls the throttle opening to follow the accelerator opening when gripping, and outputs this throttle control signal. Next, the operation of the four-wheel drive vehicle configured in this manner 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 blood transfusions at a torque distribution ratio of, for example, 60:40, corresponding to 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 IOH via the front differential device 8 and the like, and to the rear drive shaft 11. The power is transmitted to the rear wheels 14L and 14R via the rear differential device 12 and the like, resulting in full-time 4Ml drive driving with a center differential. 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 applied 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, two or four wheel slips are detected and various controls are carried out, which will be described with reference to the flowchart of FIG. First, the front wheel speed calculation section 54 of the slip detection section 51. The rear wheel speed calculation section 55 calculates the front and rear speeds NF and NR, which are then calculated by the front wheel acceleration calculation section 56. The rear wheel acceleration calculator 57 differentiates and converts the front and rear wheel accelerations OF and GR, which are sent together with the vehicle body acceleration G to the front wheel slip detector 58. The signal is input to the rear wheel slip detection section 59. The front wheel slip detection section 58 compares the acceleration difference ΔGF between the front wheels and the vehicle body with a set value ΔGs, and when the front wheel acceleration CF accelerates and rotates at a rate greater than the set value ΔGs relative to the vehicle body acceleration G, front wheel slip is detected. The rear wheel slip detection section 59 also detects rear wheel slip separately. This slip signal is input to the torque split control section 52, and a clutch pressure control signal corresponding to the slip state is input to the hydraulic unit 30 to control the clutch pressure of the hydraulic clutch 27. Therefore, in the case of front wheel slipping, the torque is distributed closer to the front wheel by increasing the clutch pressure, and in the case of rear wheel slipping, the torque is distributed closer to the front wheel by decreasing the clutch pressure.This ensures driving force.
Move in a direction to avoid slipping. Furthermore, if one of the front and rear wheels does not slip, torque split control is performed depending on the driving conditions using other factors. The above slip occurrence state is detected by the 4W slip detection section 60, and if no slip occurs, the 4W slip detection section 60 detects the slip occurrence state.
1Ha grip is detected. Therefore, a throttle control signal corresponding to the accelerator opening is input from the traction control unit 53 to the actuator 16 to open and close the throttle valve 15, thereby controlling the throttle opening to correspond to the accelerator opening. On the other hand, if front and rear slips occur simultaneously, the four-wheel slip detection section 60 detects the four-wheel slip, and the traction control section 53 narrows down the throttle opening. As a result of this, the output of the engine 1 decreases, and the increase in one or both of the front and rear wheel accelerations GF and GR is suppressed and decreased. Avoided. Although one embodiment of the present invention has been described above, the set values for the front and rear wheel slips may be different values or may be varied by various factors. In addition, in this embodiment, the traction control unit that reduces the power is configured to adjust the throttle opening degree.
The configuration is not limited to this, and the power may be reduced by brake control or ignition timing control.

【Effect of the invention】

As described above, according to the present invention, it is possible to absolutely detect the slip of the front and rear wheels in a 49JA driven vehicle based on the acceleration of the vehicle body and the front and rear wheels, and the detection accuracy is improved without causing errors due to mutual influence between the front and rear wheels. expensive. Furthermore, it is easy to detect slip or grip of the four wheels.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an outline of a four-wheel drive vehicle to which the present invention is applied, FIG. 2 is a block diagram of an embodiment of a slip detection device and a control system, and FIG. 3 is a flowchart of the operation. 42... Vehicle body acceleration sensor, 51... Slip detection section, 54... Front wheel speed calculation section, 55... Rear wheel speed calculation section, 56... Front wheel acceleration calculation section, 57... Rear wheel Acceleration calculation unit, 58...Front wheel slip detection unit, 59...Rear wheel slip detection unit Patent applicant Fuji Heavy Industries Co., Ltd. Agent Patent attorney Nobu Kobashi Ukiyo Patent attorney Susumu Murai

Claims (1)

[Scope of Claims] In the slip detection of a four-wheel drive vehicle, the present invention comprises a front and rear wheel speed calculation unit, a front and rear wheel rotational acceleration calculation unit that differentiates the front and rear wheel speeds, and means for detecting vehicle body acceleration, A slip detection device that detects slippage of one of the front and rear wheels based on the acceleration of the front wheel or the rear wheel.