JP2527936B2 - Torque distribution control device for four-wheel drive vehicle - Google Patents

Description

Torque distribution control device for driving vehicle.

Detailed Description of the Invention [Industrial applications]

The present invention relates to a full-time four-wheel drive vehicle with a center differential device, which controls the drive torque distribution between the front and rear wheels to enable control or stability-oriented traveling. The present invention relates to a torque distribution control device, and more particularly, to a device that uses a driving force distribution function of a center differential device.

[Prior art]

Regarding the front and rear wheel drive torque distribution of a full-time four-wheel drive vehicle, a hydraulic clutch is provided in the middle of the drive system for the front and rear wheels, as shown in Japanese Patent Laid-Open No. 56-43031, for example. There was one that controlled the clutch torque. Further, as shown in, for example, Japanese Patent Laid-Open No. 55-72420, there has been a center differential device provided with a hydraulic clutch for limiting the differential. By the way, since the former of the above-mentioned prior art is a structure which controls a larger transmission torque to the hydraulic clutch directly interposed in the drive system, the clutch capacity increases and durability such as wear is required to allow slip. The latter is the former,
It works when one of the rear wheels slips and a rotation difference occurs. All of these reduce the torque of the rear wheels to avoid the tight corner braking phenomenon at the time of direct connection 4WD,
Or it was a diff lock for emergency escape with a center diff. Therefore, a torque distribution device is provided to bypass the center differential device, and based on the information from the vehicle speed sensor, the front wheel drive torque distribution is emphasized more at high speeds and stability is emphasized. The drive torque distribution is similar to that of rear-wheel drive, with an emphasis on turning performance. Further, there is also proposed a method in which the steering angle of the steering wheel is detected and the front-rear drive torque distribution is changed according to the detected steering angle to ensure the turning ability when turning.

[Problems to be Solved by the Invention]

By the way, in the configuration of the prior art, in order to perform the torque distribution as described above, the drive torque from the transmission is distributed to the front and rear wheels, and the torque distribution can be controlled arbitrarily. There is a need. In this case, the torque distribution is desired to prevent power loss. Further, since the driving torque distribution is controlled by the traveling state based on the information from the vehicle speed sensor and the steering angle sensor,
The front-to-rear torque distribution of a four-wheel drive vehicle during normal driving is constant regardless of road conditions such as climbing and descending roads and loading load. For example, the torque distribution is always 50:50 for those with a built-in bevel gear type center differential. It was However, when road conditions such as uphill and downhill conditions or when a lot of luggage is loaded in the trunk, the weight distribution of the vehicle becomes backward, and with a torque distribution of 50:50, sufficient driving force cannot be obtained and good climbing performance is achieved. There is a problem that you can not exert it. The present invention has been made in view of the above point, and automatically controls the drive torque distribution of the front and rear wheels in accordance with the climbing and descending angle and the loading state to improve climbing performance, maneuverability, and stability. It is an object of the present invention to provide a torque distribution control device for a four-wheel drive vehicle designed to achieve the above.

[Means for solving problems]

In order to achieve the above object, the present invention provides a torque distribution device in which a transmission output shaft is transmitted to front and rear wheels via a center differential device, and the center differential device is bypassed. A first gear shift stage provided on one side gear side and a second gear shift stage having a gear ratio larger than the first gear stage provided on the other side gear side,
A third shift gear having a smaller gear ratio than the second shift gear, and a second or third shift gear provided on the driven side of the second and third shift gears and a selection signal. In the four-wheel drive system, the four-wheel drive system includes a switching clutch that is connected to the first shift gear and a hydraulic clutch that connects the switching clutch to the switching clutch in a variable transmission torque. A torque distribution control device for automatically controlling drive torque distribution between front and rear wheels by controlling a clutch torque, wherein an output torque sensor for detecting a drive torque of a transmission output shaft, a vehicle speed sensor, and an air suspension air pressure are detected. A front and rear wheel load sensor or a vehicle body angle sensor for detecting the uphill / downhill angle is provided to map the optimum driving force distribution value corresponding to the vehicle speed and the uphill / downhill angle or the loading condition. Storage means, uphill / downhill angle / loading state calculating means for obtaining the uphill / downhill angle and loading state based on signals from the front / rear wheel load sensors or vehicle body angle sensors, vehicle speed signal from the vehicle speed sensor and the above calculation A power distribution deciding means for obtaining a driving force distribution value by performing a map search from the storage means by using the climbing and descending angle or the loading state obtained by the means as an address signal, and switching from the driving force distribution value obtained by the power distribution deciding means. The clutch torque of the hydraulic clutch is determined from the switching clutch switching designation generating means that determines the selection of the shift gear stage by the clutch, the drive torque detected by the output torque sensor, and the driving force distribution value obtained by the power distribution determining means. And a clutch torque calculating means for calculating

[Action]

Based on the above-mentioned configuration, the torque distribution control device including a microcomputer includes an air suspension air pressure signal detected by a wheel load sensor provided on each of front and rear wheels or a vehicle body angle (pitch angle) signal detected by a vehicle body angle sensor. The uphill and downhill angle of the vehicle and the loading state are determined by and the optimal driving force distribution value stored in the storage device in advance in the form of a map is determined by using the determination state signal and the vehicle speed signal detected by the vehicle speed sensor as an address signal. Read. If the drive force distribution value is closer to the rear wheel drive, the switching clutch is engaged with the second shift gear, and the hydraulic pressure corresponding to the drive force distribution value is applied to the hydraulic clutch to generate the corresponding clutch torque. The clutch torque is added to the rear-wheel drive torque distributed by the center differential device substantially equally, and is subtracted from the front-wheel drive torque so as to be closer to the rear-wheel drive, thereby improving the turning ability and the climbing ability. On the other hand, if the driving force distribution value is higher than that of the front wheel drive, the switching clutch is engaged with the 32nd speed change gear, the hydraulic pressure corresponding to the driving force distribution value is applied to the hydraulic clutch, and the reverse operation is performed. The torque distribution will be closer to the front-wheel drive to improve running stability and engine braking effect when going downhill.

【Example】

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a skeleton diagram showing the structure of a transmission system of a four-wheel drive vehicle with a center differential, in which reference numeral 1 is an engine,
Reference numeral 2 is a transmission, 3 is a front wheel, 4 is a rear wheel, 5 is a front diff, 6 is a rear diff, and 7 is a center diff composed of a combination of bevel gears. The drive shaft 7b is connected to the rear differential 6. Reference numeral 8 is a first gear fixed to the output shaft 2a of the transmission 2, and 9 is a second gear provided in the differential case of the center differential 7, which meshes with the first gear 8. 10 is a torque distribution device provided by bypassing the center differential 7, 11 is a hydraulic clutch provided on the bypass shaft 10a of the torque distribution device 10, and 12 is a first clutch fixed to the front wheel side drive shaft 7a of the center differential 7. 3 gears, 13 is a fourth fixed to one end of the bypass shaft 10a
The gear meshes with the third gear 12 to form a first gear stage. Reference numeral 14 is a large-diameter fifth gear that is loosely fitted to the drum side hollow shaft of the hydraulic clutch 11, and 15 is a rear wheel side drive shaft of the center differential 7.
The sixth gear having a small diameter fixed to 7b meshes with the fifth gear 14 to form a second speed change gear. 16 is a small-diameter seventh gear that is loosely fitted to one end of the drum-side hollow shaft of the hydraulic clutch 11, 17
Is a large-diameter eighth gear fixed to the rear wheel side drive shaft 7b.
It meshes with the gear 16 to form a third gear stage. A switching clutch 18 is movably arranged between the fifth gear 14 and the seventh gear 16, and is engaged with the fifth gear 14 or the seventh gear 16 and is shown in FIGS. 3 and 4. As described above, the connection between the hydraulic clutch 11 and the hollow shaft 11c protruding from the drum 11b is turned on / off. Reference numeral 19 is an actuator for switching the switching clutch 18, 20 is a hydraulic unit, and a predetermined hydraulic pressure Pc is applied to the hydraulic clutch.
Clutch hub 1 applied to 11 and fixed to bypass shaft 10a
Clutch torque Tc is generated by the contact pressure between 1a and drum 11b. Reference numeral 21 denotes an output torque sensor attached to the transmission output shaft 2a, which detects the drive torque T. twenty two
Is, for example, a vehicle speed sensor arranged on the front wheel 3 or the like, 23 _F , 23 _R
Is a wheel load sensor that detects the air pressure in the air suspension 24 as shown in FIG. 5 to determine changes in the wheel load during loading and during running. Reference numeral 30 is a torque distribution control device including a microcomputer. In FIG. 2 showing the configuration of the torque distribution control device 30, the reference numeral 31 denotes a storage device, which is an optimum driving force distribution value corresponding to the vehicle speed V and the uphill / downhill angle α or the loading state, that is, the front wheel driving force distribution value R _F. , Are stored in advance in the form of a map or the like. Reference numeral 32 denotes an uphill / downhill angle / loading state calculation means, which obtains the uphill / downhill angle α based on signals from the wheel load sensors 23 _F and 23 _R , and further determines the loading state, that is, the weight distribution of the vehicle. Reference numeral 33 denotes a driving force distribution determining means, which uses the vehicle speed signal V from the vehicle speed sensor 22 and the ascending / descending angle α obtained by the calculating means 32 as an address signal to perform a map search to obtain a front wheel driving force distribution value R _F. Reference numeral 35 denotes a switching clutch switching command generating means which, for example, outputs an OFF signal to the switching clutch 18 so as to engage with the second speed change gears 14 and 15 when the distribution value R _F is smaller than 0.5, thereby distributing the distribution value R _F. Is 0.
When it is larger than 5, an ON signal is output so as to engage with the third transmission gear stage 16,17. Reference numeral 34 denotes a clutch torque calculation means, which calculates a clutch torque Tc to be generated in the hydraulic clutch 11 based on the distribution value R _F and the drive torque T detected by the output torque sensor 21, and outputs a hydraulic pressure command corresponding to the calculated clutch torque Tc. Give to 20. Next, the operation of the torque distribution device 10 will be described with reference to FIGS. The drive torque T of the transmission output shaft 2a is the first
It is transmitted to the center differential 7 via the gear 8 and the second gear 9,
Here, it is distributed in approximately equal parts and transmitted to the front wheel side drive shaft 7 and the rear wheel side drive shaft 7b. At this time, if the hydraulic pressure Pc applied to the hydraulic clutch 11 is zero and is off, the torque distribution device 10 does not operate at all and the front wheel 3 and the rear wheel 4 are respectively (T /
It is driven by the driving torque T _F , T _R of 2). This hydraulic clutch
When the switching clutch 18 is engaged with the fifth gear 14 and the sixth gear 15 which are the second gear stage (Fig. 3), the hub 11a is the first gear stage. There is a third gear 12, a fourth
It rotates through the gear 13 and the bypass shaft 10a, and the drum 11b.
Is decelerating and rotating via the reduction ratio K between the small diameter sixth gear 15 and the large diameter fifth gear 14, the switching clutch 18, and the hollow shaft 11c, so when the hydraulic pressure Pc is gradually added from the hydraulic unit 20, A clutch torque Tc corresponding to the oil pressure Pc is generated due to the rotation difference, and the clutch torque Tc is added to the low speed rotation side drum 11b, and the driving torque T _R to the rear wheel side drive shaft 7b is T _R = (T / 2) + K · Tc. On the other hand, the drive torque T _F applied to the front wheel side drive shaft 7a is T _F = (T / 2) −Tc, which is closer to the rear wheel drive depending on the hydraulic pressure Pc applied to the hydraulic clutch 11. In addition, the switching clutch 18 is the third shift gear, the seventh shift gear.
When engaged with the gear 16 and the eighth gear 17, the drum 11b of the hydraulic clutch 11 includes the large diameter eighth gear 17 and the small diameter seventh gear 17.
Since the rotation speed is increased through the reduction ratio K ′ with the gear 16, the switching clutch 18, and the hollow shaft 11c, the clutch torque Tc generated according to the hydraulic pressure Pc from the hydraulic unit 20 is applied to the hub 11a on the low speed rotation side. In addition, contrary to the above, the drive torque T _F to the front wheel side drive shaft 7a is T _F = (T / 2) + Tc. On the other hand, the driving torque T _R applied to the rear wheel side drive shaft 7b becomes T _R = (T / 2) −K ′ · Tc, which is closer to the front wheel drive. This torque distribution control is conventionally performed based on the information from the vehicle speed sensor 22 and the steering angle sensor, and the road conditions such as climbing and the loading state have not been taken into consideration. The maneuverability and stability were not obtained. Therefore, the torque distribution control device 30 according to the present invention is
Wheel load sensor provided on the rear wheel air suspension 24
Input wheel load information from 23 _F , 23 _R , or vehicle body angle (pitch) information from a vehicle body angle sensor (not shown),
Uphill / Downhill Angle / Uphill / Downhill Angle α
And the weight distribution of the vehicle are calculated, and the driving force distribution determination means 33
Is the uphill / downhill angle α and the vehicle speed signal V from the vehicle speed sensor 22.
Based on the above, using this as an address signal, the optimum front wheel driving force distribution values R _F , R _F = T _F / (T _F + T _R ) stored in advance in the form of a map in the storage device 31 are obtained. Now, for example, when entering an uphill road from a running state near the front wheel drive, the front wheel drive force distribution value R _F read from the map of the storage device 31 exceeds 50:50 and becomes smaller than 0.5. The generating means 35 outputs an OFF signal to the actuator 19 instead of the ON signal so far, and the engagement of the switching clutch 18 is changed to the second gear from the seventh gear 16 and the eighth gear 17 which are the third gear stage. The fifth gear and the sixth gear, which are the speed change gear stages, are switched. Further, the clutch torque calculation means 34 uses the read front wheel drive force distribution value R _F and the drive torque T of the transmission output shaft 2a detected by the output torque sensor 21 to obtain R _F = 1 / [1 + {(T / 2) + K · Tc} ÷ {(T / 2) -Tc}) is calculated, and the clutch torque Tc of the hydraulic clutch 11 is calculated, and a hydraulic pressure command corresponding to this clutch torque Tc is given to the hydraulic unit 20. Equivalent hydraulic pressure Pc to hydraulic clutch 11
To drive four wheels closer to the rear wheel drive to enhance the climbing ability. On the other hand, in the case of a downhill, since the front wheel drive force distribution value R _F closer to the front wheel drive is read from the map of the storage device 31, an ON signal is output from the switching clutch switching command generation means 35 to the actuator 19, and switching is performed. The clutch 18 is engaged with the seventh gear 16 and the eighth gear 17, which are the third gear stage, and the clutch torque calculation means 34 determines that R _F = 1 / [1 + {(T / 2) + K '· Tc}. ÷ {(T / 2) + Tc}) is calculated, and the clutch torque Tc of the hydraulic clutch 11 is calculated, and a hydraulic pressure command corresponding to this clutch torque Tc is given as
It is applied from the hydraulic unit 20 to the hydraulic clutch 11 so that it is closer to the front wheel drive. When the loading state changes, similar control is performed to improve maneuverability and ensure stability.

【The invention's effect】

As is clear from the above description, according to the present invention, the vehicle body angle sensor or the wheel load sensor is used to determine the uphill / downhill angle of the traveling road surface and the loading state, and the driving force distribution of the front and rear wheels is determined according to this state. Since the automatic control is performed, the climbing ability can be enhanced, and the maneuverability and stability on the uphill and downhill roads, the climbing ability and startability in various loading states, and the maneuverability and stability can be improved.

[Brief description of drawings]

FIG. 1 is a skeleton diagram showing the configuration of a four-wheel drive vehicle with a center differential device of the present invention, FIG. 2 is a block diagram showing the configuration of the torque distribution control device of the present invention, and a torque distribution diagram of the torque distribution device, third. 4 and 5 are views showing torque distribution of the torque distribution device according to the present invention, and FIG. 5 is a sectional view of an air suspension to which a wheel load sensor is attached. 2 ... transmission, 3 ... front wheel, 4 ... rear wheel,
7 ... Center differential, 8, 9, 12 to 17 ... Gear, 10 ... Torque distribution device, 11 ... Hydraulic clutch, 18 ... Switching clutch, 19 ... Actuator, 20 ... Hydraulic unit, 21 ...
… Output torque sensor, 22 …… Vehicle speed sensor, 23 _F , 23 _R ……
Wheel load sensor, 30 ... Torque distribution control device.

Claims (1)

(57) [Claims] 1. A torque distribution device, wherein a transmission output shaft is transmitted to front and rear wheels via a center differential device, and which is provided by bypassing the center differential device, is provided on one side gear side of the center differential device. A first speed change gear, a second speed change gear having a larger gear ratio than the first speed change gear provided on the other side gear, and a third speed change gear having a lower gear ratio than the second speed change gear. And a switching clutch that is provided on the driven side of the second and third speed change gears and serves as a selection sign for the second or third speed change gear, and the driven side of the first speed change gear and the above-mentioned changeover. In a four-wheel drive system including a clutch and a hydraulic clutch for variable transmission torque coupling, the selection of the switching clutch and the clutch torque of the hydraulic clutch are controlled to automatically control the drive torque distribution between the front and rear wheels. Torque distribution The control device is provided with an output torque sensor for detecting the drive torque of the transmission output shaft, a vehicle speed sensor, and front and rear wheel load sensors for detecting the air suspension air pressure or a vehicle body angle sensor for detecting the up / down slope angle. , Storage means for storing an optimal driving force distribution value corresponding to the vehicle speed and the uphill / downhill angle or the loading state in a map, and the uphill / downhill angle and loading based on the signals from the front and rear wheel load sensors or the vehicle body angle sensor. An uphill / downhill angle / loading state calculating means for obtaining the state, a vehicle speed signal from the vehicle speed sensor, and the uphill / downhill angle or the loading state obtained by the above calculating means are used as address signals in a map search from the storage means to obtain a driving force distribution value. The power distribution determining means to be obtained and the transmission gear by the switching clutch based on the driving force distribution value obtained by the power distribution determining means. The clutch torque for calculating the clutch torque of the hydraulic clutch from the switching clutch switching designation generating means for determining the selection of the above, the driving torque detected by the output torque sensor and the driving force distribution value obtained by the power distribution determining means. Four wheels characterized by comprising a calculation means