JPH01113668A - Detecting apparatus of slip - Google Patents

Abstract

PURPOSE:To enable the highly precise detection of a four-wheel slip and four- wheel grip of a four-wheel drive vehicle, by a method wherein the judgement of the four-wheel slip is made when a difference between a wheel acceleration and a vehicle body acceleration is a set value or above while the judgement of the four-wheel grip is made when said difference is below a set value, in the condition other than that of a two-wheel slip. CONSTITUTION:The speeds NF and NR of front and rear wheels are inputted as the average wheel speed V of four wheels to a wheel acceleration calculator 59 and thereby a wheel acceleration GV corresponding to the state of movement of a vehicle body is calculated. The wheel acceleration GV and a vehicle body acceleration G of a vehicle body acceleration sensor 42 are inputted to a four- wheel slip detector 60. An acceleration difference DELTAG between the two accelerations is determined from the relationship of GV>G in the condition other than that of a two-wheel slip, and when this difference is a set value for a slip or above, a four-wheel slip is detected. A four-wheel grip detector 61 makes the judgement of a four-wheel grip when the difference between the wheel acceleration GV and the vehicle body acceleration G turns to be below a set value for a grip in the state of the four-wheel grip.

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.

[Conventional technology]

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 wheels. 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 2M slip, it has been considered to perform torque split control so as to increase the torque distribution to the grip side wheels. In such torque split control, two-wheel slip is avoided by distributing torque between the front and rear wheels, so the turning performance of the center differential is not lost, driving force is secured, and traction is effective. Further, 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 performed when the two wheels are in the slip escape state. Here, when torque split control is performed for the above-mentioned two-wheel slip, the torque is distributed to the limit that does not cause two-wheel slip, so if slip occurs, it will be a four-wheel slip state, and the accuracy of torque split control will be reduced. The better the condition, the less likely two-wheel slip will occur and the better the limit performance will be, but it will be difficult to control when all four wheels slip at the same time, and this four-wheel slip cannot be resolved by torque splitting, so the engine output will be reduced, etc. The only option is to rely on traction control, which reduces power. In this way, since the torque split of a four-wheel drive vehicle and traction control that reduces power are performed in relation to wheel slip, slip detection is necessary. here,
Since the four wheels of a four-wheel drive vehicle are the driving wheels and there is a possibility of slippage, detecting slippage on the second or fourth wheel using only this wheel speed will result in a large error. It is necessary to devise ways to Conventionally, regarding the slip detection of a four-wheel drive vehicle, there is a prior art technique disclosed in, for example, Japanese Utility Model Application Publication 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, if the vehicle speed sensor of the prior art is attached to the output side of the transmission and calculates the vehicle speed based on its rotation, the value will be significantly different from the actual moving speed of the vehicle body when the drive wheels slip. Furthermore, four-wheel slip cannot be detected. In view of these points, an object of the present invention is to provide a slip detection device that can detect four-wheel slip and grip of a four-wheel drive vehicle with high accuracy.

[Means to solve the problem]

In order to achieve the above object, the present invention provides that the movement of the vehicle body is determined from the detected value by the vehicle body acceleration sensor, and that it is 41 MI slip or grip under conditions other than 2 wheel slip conditions, and 4 MI slip or grip.
In the case of wheel slipping, there is a large difference in acceleration between the vehicle body and the wheels, and we are focusing on the fact that when this difference becomes smaller, four-wheel grip becomes possible. Therefore, in the slip detection of a four-wheel drive vehicle, at least the front and rear wheel speed calculating section 1 calculates the wheel acceleration by differentiating the wheel speed that is the average of the front and rear wheel speeds. Means for detecting vehicle body acceleration 1 Determine 4-wheel slip when the difference between the wheel acceleration and vehicle body acceleration is equal to or greater than a slip setting value under conditions other than 2-wheel slip on one of the front and rear wheels 4
The vehicle includes a wheel slip detection section, and is configured to determine four-wheel grip when the difference between wheel acceleration and vehicle body acceleration becomes equal to or less than a grip setting value in a four-wheel slip state.

[For production]

Based on the above configuration, under four wheel slip or grip conditions excluding two wheel slip conditions on one of the front and rear wheels,
When the wheel acceleration becomes higher than the slip setting value relative to the vehicle body acceleration, four-wheel slip is determined, and when the wheel acceleration becomes below the grip setting value in the four-wheel slip state, four-wheel grip is determined. Thus, in the present invention, it is possible to accurately detect four-wheel slip and grip using the vehicle body speed based on vehicle body acceleration under conditions excluding 219+slip.

【Example】

Embodiments of the present invention will be described below based on the drawings. In FIG. 1, the drive system of a four-wheel drive vehicle with a center differential and capable of torque split and traction control, to which the present invention is applied, is a front engine, vertically mounted, and equipped with an automatic transmission with a torque converter. Specifically, 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 I13 is input to a center differential device 20, and a torque split device 25 is provided in a bypass manner to the center differential device 20. Center differential equipped! 20 is 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 gears 21 . of 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 a front drive shaft 7 parallel to the output shaft 4 via a reduction gear 5.6, and this front drive shaft 7 Front differential device 8° Left and right front wheels 10L, 1 via axle 9
The transmission is configured to 0R. 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.
41.148 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 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 set to, for example, “1”.
'', and the gear ratio of gears 28 and 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 clutch pressure, etc., 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 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 of the rear drive shaft 11 is (1−γ )・Allocated to 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, as the clutch torque Tc changes, the distribution ratio of the front torque T[ is continuously changed within the range below the distribution ratio in the center differential device 20, and the distribution ratio of the rear torque TR is the distribution ratio in the center differential device [20]. Torque splitting is effected by changing continuously within the above range. 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, rotation speed sensors 40 for left and right front wheels and rear wheels
L, 40R, 41L, 41R, vehicle acceleration sensor 42.
Accelerator opening sensor 43. It has a throttle opening sensor 44° and a steering angle sensor 45, and these sensor signals are input to a control unit 50. The control unit 50 processes the sensor signal to determine a slip state, and outputs a clutch pressure control signal to the hydraulic unit 30 and a throttle control signal 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 unit 51 includes rotation speed sensors 40L and 401.
It has a front wheel speed calculation unit 54 into which the left and right front wheel rotational speeds NFL and NFR of the left and right front wheels are input, and a rear wheel speed calculation unit 55 into which the left and right rear wheel rotational speeds NRL and NRR of the rotational speed sensor 4 and 41R are input. Calculation unit 54. The rear wheel speed calculation unit 55 calculates the front and rear wheel speeds NF and NR as follows: NF = (NFL thousand NFR)/2 NR = (NRL + NRR) /2 The above front and rear wheel speeds NF and NR are front wheel slip detection. NF
-NR>ΔNs If + is 1, front wheel slip is detected. Further, the front and rear wheel speeds NF and NR are input to the rear wheel slip detection section 57, and rear wheel slip is detected when NF-NR<ΔNs- is 2. Here, K1. 2 is the dead zone width determined by the accuracy of the rotation speed sensor. These two-wheel slip signals are input to the torque split control unit 52, and in the case of front wheel slip, the clutch pressure of the hydraulic clutch 27 and the amount of torque transferred from the front wheel side to the rear wheel side are increased to distribute torque closer to the rear wheels. , in the case of rear wheel slip, the clutch pressure is reduced to control torque distribution closer to the front wheels, and this clutch pressure control signal is output to the hydraulic unit 30 that supplies clutch pressure to the hydraulic clutch 27. On the other hand, the front and rear wheel speeds NF and NR are input to the wheel speed calculating section 58, and the wheel speed V corresponding to the vehicle speed on the average of the four wheels is calculated as follows. V=(NF+NR)/2 This wheel speed V is input to the wheel acceleration calculating section 59, and the wheel speed V is differentiated as follows to calculate the wheel acceleration GV corresponding to the moving state of the vehicle body. Gv = dV/dt The wheel acceleration Gy and the vehicle body acceleration G from the vehicle body acceleration sensor 42 are input to the four-wheel slip detection section 60, which includes the front wheel slip detection section 56. Rear wheel slip detection section 57
A two-wheel slip signal is input, and the following judgment is made only under four-wheel slip or grip conditions other than the two-wheel slip condition. That is, from the relationship Gy>G, the acceleration difference ΔG between the two is determined by ΔG=GV−G, and using a predetermined split setting value ΔOs (>O), ΔG>ΔG
s, four-wheel slip is detected. This four-wheel slip signal is input to a traction control section 53 that reduces the power, and when four wheels slip, a corrected throttle control signal is output so as to reduce the throttle opening and limit the engine output. Further, in contrast to the 41M slip detection section 60, a 4-grip detection section 61 is provided, and the output of the 4-wheel slip detection section 60 is input together with the vehicle body acceleration G and wheel acceleration Gv. The 4-wheel grip detection unit 61 has a set value ΔGS'(<O) for grip at a level lower than the vehicle body acceleration G, and detects 4-wheel grip when ΔG becomes ΔGS' after detecting 4-wheel slip; The traction control section 53 that reduces the power is restored to control the throttle opening to follow the accelerator opening. 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 of the engine 1 is input to the automatic transmission l13 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 the ring gear 22. Duction gear 5, 6°. Front drive shaft 7. The power from the sun gear 21 is transmitted to the front wheels 10L, 10H via the front differential device 8 and the like to the rear drive shaft 11. It is transmitted to the rear wheels 14L and 14R via the rear differential equipment FI12, etc.
This results in full-time four-wheel drive 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 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. And 2￥Al
A or four-wheel slip is detected and various controls are performed, which will be described with reference to the flowchart of FIG. First, the slip flag is cleared and initialized, and the front wheel speed calculating section 54 and the rear wheel speed calculating section 55 of the slip detecting section 51 calculate front and rear $1i1 speeds NF and NR, which are sent to the front wheel slip detecting section 56. Input it to the rear wheel slip detection section 57 and calculate the difference between the two before and after the target lI! i Compare the speed difference ΔNS and the unfavorable zone width with 1 and 2. And ΔNs −
2 <NF -NR<ΔN5-)-If the condition 1 is not satisfied, slip of the front or rear wheels is detected, and this slip signal is input to the torque split control section 52, which controls the clutch according to the slip state. A pressure control signal is input to the hydraulic unit 30 to control the clutch pressure of the hydraulic clutch 27. Therefore, in the case of front wheel slip, torque split control is performed to distribute torque closer to the rear wheel by increasing clutch pressure, and in the case of rear wheel slip, torque is distributed closer to the front wheel by decreasing clutch pressure.This ensures driving force and prevents slip. Transition. In addition, if two-wheel slip does not occur, torque split control is performed using other factors depending on the driving conditions. On the other hand, the four-wheel slip detection unit 60 becomes capable of detection under conditions other than the two-wheel slip conditions described above, and the difference ΔG between the wheel acceleration Gv, which is obtained by differentiating the wheel speed V, and the vehicle body acceleration G is determined. Here, if the slip flag is clear, it is compared with the slip setting value ΔGS. If the difference ΔG is less than ゛ seconds from the slip setting value. That is, when the vehicle body acceleration G increases substantially along the wheel acceleration Gy, it is determined that the vehicle is running stably, and a throttle control signal corresponding to the accelerator opening is input to the actuator 16 from the traction control section 53 that reduces the power. By opening and closing the throttle valve 15, the throttle opening degree is controlled to correspond to the accelerator opening degree. On the other hand, as shown in FIG. 4, when only the wheel acceleration Gy suddenly increases and exceeds the slip film constant value ΔGs, at this point t
1, four-wheel slip is detected, a slip flag is set, and the throttle opening is reduced by the traction control section 53 which reduces the power. Therefore, the output of the engine 1 decreases, and accordingly, the increase in wheel acceleration GV is suppressed and decreases. At this time, in order to make the difference ΔG substantially zero, the wheel acceleration GV is reduced to below the vehicle body acceleration G, and after this four-wheel slip detection, the grip detection section 61 becomes able to detect the difference between the wheel acceleration Gv and the vehicle body acceleration G. When the difference becomes less than the grip setting value ΔGs, four-wheel grip is detected at this point t2, and the slip flag is cleared.Then, the throttle opening returns to its original value, and the wheel speed V increases along with the engine output. Such control is repeated once or several times to avoid four-wheel slip, and the wheel acceleration Gy becomes approximately in line with the vehicle body acceleration G. An embodiment of the present invention has been described above. Front and rear transport speed NF
, NR may be directly detected by the drive system. The torque split control of the 21fiii slip and drop on one of the front and rear wheels is not limited to the above. The set values ΔGs and ΔGS' for slip and grip can be selected from various values, and may be varied using other factors. Furthermore, in this embodiment, the traction control unit that reduces the power is configured to adjust the throttle opening.
The configuration is not limited to this, and the power may be reduced by brake control, ignition timing control, or the like.

【Effect of the invention】

As described above, according to the present invention, four-wheel slip can be accurately detected in a four-wheel drive vehicle using the wheel acceleration and vehicle body acceleration determined from the wheel speed. Since detection of four-wheel slip is performed under conditions of slip or grip of four wheels other than the condition of two-wheel slip of one of the front and rear wheels, confusion between the two can be prevented. Since slip is determined based on the acceleration obtained by differentiating the wheel speed, there is little error. Detection of 4-wheel grip after 4-wheel slip detection is performed using different setting values from 4-wheel slip detection.
Both wheel slip and grip can be optimally detected. Since the grip setting value is set to a level lower than the vehicle body acceleration and sufficiently reduces the wheel acceleration, it is possible to reliably eliminate the rotational difference due to four-wheel slip. Throttle control can be performed most effectively by detecting the four-wheel slip and grip, and four-wheel slip can be accurately prevented.

[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 the slip detection device and the control system, Fig. 3 is a flowchart of the operation, and Fig. 4 FIG. 2 is a time chart showing a state in which four-wheel slip is prevented. 42... Vehicle body acceleration sensor, 51... Slip detection section, 54... Front wheel speed calculation section, 55... Rear wheel speed calculation section, 58... Wheel speed calculation section, 59... Wheel acceleration Calculation unit, 60... 4-wheel slip detection unit, 61... 4-wheel grip detection unit Patent applicant Fuji Heavy Industries Co., Ltd. Agent Patent attorney Makoto Kobashi Ukiyo Patent attorney Shinbue Murai Figure 4

Claims (1)

[Scope of Claims] In the slip detection of a four-wheel drive vehicle, at least a calculating section for front and rear wheel speeds, a calculating section for calculating wheel acceleration by differentiating the wheel speed obtained by averaging the front and rear wheel speeds, a means for detecting vehicle body acceleration, and a means for detecting the front and rear wheels. It has a 4-wheel slip detection unit that determines 4-wheel slip when the difference between the wheel acceleration and the vehicle body acceleration is equal to or greater than a slip setting value under conditions other than 2-wheel slip on one of the wheels. A slip detection device characterized in that four-wheel grip is determined when the difference between and vehicle acceleration becomes less than or equal to a set value for grip.