JPS62275839A - Controlling method for four-wheel drive device - Google Patents

Abstract

PURPOSE:To lessen the wear of tires while prevent the deterioration of fuel consumption by reducing the engaging force of a differential control clutch for directly and selectively connecting the differential action of a center differential device when a vehicle speed is above a defined value while an engine output is below a defined value. CONSTITUTION:A four-wheel drive transfer device 3 which is connected to the rear part of an automatic transmission 2 has a planetary gear type center differential device 10 for full-time four-wheel driving. It also has a hydraulic differential type differential control clutch 21 for selectively connecting the sun gear 13 to the ring gear 14 of the device 10, and the clutch 21 is differentially controlled by means of a hydraulic control device 22. In this case, a control device 45 makes the hydraulic control device 22 control so as to reduce the engaging force of the differentials control clutch 21, when judged to be in an operating condition that a vehicle speed detected by a vehicle speed sensor 46 is above a defined value and that an engine output detected from the output of a throttle opening sensor 47 is below a defined value.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention Industrial Field of Application The present invention is directed to a four-wheel drive device used in vehicles such as automobiles. The present invention relates to a method, and particularly to a method of controlling a four-wheel drive device having a center differential device and a differential control clutch.

Conventional Technology One of the four-wheel drive devices used in vehicles such as automatic Φ is a center differential device that performs differential operation between the rear wheels and front wheels, and a center differential device that selectively operates the differential operation of the center differential device. A four-wheel drive system having a differential control clutch that selectively directly connects the rear wheels and front wheels by stopping the front wheels has already been proposed. , Japanese Patent Publication No. 55-72420
This is shown in each publication of the issue.

In a vehicle equipped with a four-wheel drive system as described above, when the differential control clutch is disengaged, the center differential system can operate differentially, thereby avoiding the occurrence of tight corner braking and making cornering possible. On the other hand, when the differential control clutch is engaged, the center differential device is prohibited from performing differential operation, resulting in a four-wheel drive state in which the front and rear wheels are directly connected, improving drive performance. In particular, the drive performance during high output driving such as when driving uphill is improved, and excellent driving performance can be obtained.

Problems to be Solved by the Invention By the way, the difference in rotational speed between the front and rear wheels of a vehicle is determined by the effective radius of each of the front and rear tires and the turning radius of the vehicle. changes depending on the air pressure and wear l of each tire and the shared load.Therefore, a difference in rotational speed occurs between the front and rear wheels not only when turning but also when driving straight, and this rotational speed difference becomes louder when driving at high speed. Therefore, when driving in a straight line at high speed, if the front wheels and rear wheels are completely directly connected by engagement of the differential control clutch, the rotational speed difference between the front wheels and the rear wheels is not absorbed by the center differential device, and the rear wheels are Circulating torque (twisting torque) is generated in the power transmission system for the wheels and the front wheel, and this becomes absorbed by the slippage of the tires on the road surface, so that relatively I! ! When driving on a normal road surface with a high coefficient of friction, there is a risk that the tires will wear significantly and fuel efficiency will deteriorate.

The present invention achieves both the ability to obtain excellent drive performance when driving at high output, and the ability to avoid the generation of circulating torque in the power transmission system due to the difference in rotational speed between the front and rear wheels during other high-speed driving. The purpose of the present invention is to provide an improved four-wheel drive control method.

Means for Solving the Problems - According to the present invention, the above-mentioned object is achieved by providing a rent-a-diff7 rental device that performs differential operation between rear wheels and front wheels;
In a method for controlling a four-wheel drive device, the method includes a differential control clutch that selectively stops differential operation of the center differential device to selectively directly connect rear wheels and front wheels,
A four-wheel layer characterized in that the engagement force of the differential control clutch is reduced when the vehicle speed is above a predetermined value and the engine output is below a predetermined value! This is achieved by the control method of the II device.

Effects and Effects of the Invention According to the method for controlling a four-wheel drive device according to the present invention, the engagement force of the differential control clutch is reduced when the vehicle speed is above a predetermined value and the engine output is below a predetermined value, that is, during steady high-speed driving. The differential control clutch becomes in a state where it can slip, and as a result, during this driving state, the front wheels and rear wheels are not completely directly connected, and the center differential device is set in a state where it can perform differential operation. Even when driving straight, if there is a difference in rotational speed between the front and rear wheels due to the difference in the effective radius of the front and rear tires, this will be absorbed by the differential operation of the center differential S device, and the power transmission system Circulating torque is not generated, and the tires do not slip on the road surface due to the difference in rotational speed between the front wheels and the rear wheels, thereby avoiding severe wear of the tires and deterioration of fuel efficiency. Even when driving at high speeds, the differential control clutch can be engaged when the engine output is large, that is, when driving at high power, and this allows a four-wheel drive state in which the front and rear wheels are directly connected, making it possible to improve the performance of the vehicle. Vehicles will now be driven 1@ under performance.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail by way of embodiments with reference to the accompanying drawings.

FIG. 1 is a skeleton diagram showing a four-wheel layer VJ device used to implement the control method according to the present invention. In the figure, 1 indicates an internal combustion engine, and the internal combustion engine is located at the front of the vehicle! The vehicle automatic transmission R is located at the rear of the internal combustion engine.
2 and a four-wheel drive transfer device 3 are connected in this order.

The automatic transmission 2 for a vehicle includes a hydraulic torque converter 5 of a general structure provided in a converter case 4 and a gear type transmission device 7 provided in a transmission case 6.
The input member 8 of the hydraulic torque converter 5 is drivingly connected to the output shaft (crankshaft, not shown) of the internal combustion engine 1, and the rotational power of the internal combustion engine 1 is transferred to the transmission via the hydraulic torque converter 5. It is designed to be given to 7. The transmission 7 is a well-known transmission comprised of a planetary gear mechanism or the like, and is configured to shift between a plurality of gear stages, and its gear change is controlled by a hydraulic control device 9.

The four-wheel drive transfer device 3 is a planetary gear type pinter differential device 10 for full-time 4WD.
The center differential device 10 includes a carrier 11 as an input member to which rotational power is applied from the transmission 7, a planetary pinion 12 supported by the carrier, a number gear 13 meshed with the planetary pinion 12, and a The ring gear 14 has a ring gear 14.
4 is connected to a rear wheel drive shaft 15, and the sun gear 13 is connected to a sleeve-shaped front wheel drive intermediate shaft 16 which is in contact with the rear wheel drive shaft 15. The four-wheel drive transfer device 3 is provided with a front wheel drive shaft 17 parallel to the front wheel drive intermediate shaft 16, and the front wheel drive intermediate shaft 16 and the front wheel drive shaft 17 each have a sprocket attached thereto. The driving connection is made by an endless chain 20 meshing with 18 and 19.

The four-wheel drive transfer device t3 is provided with a hydraulically operated differential control clutch 21 that selectively connects the number gear 13 and the ring gear 14, and the operation of the differential control clutch is controlled by the four-wheel drive transfer device. This is performed by a hydraulic control device 22 provided at 3.

One end of a rear propeller shaft 24 is drivingly connected to the rear wheel drive shaft 15 through a universal joint 23 .

One end of a front propeller shaft 26 is connected to the front wheel drive shaft 17 via a universal joint 25 . The front propeller shaft 26 extends approximately parallel to the axis on one side of the vehicle automatic transmission R2, and is connected to the front differential by a universal joint 27 at the other end. It is connected to one end of a drive pinion shaft 31, which is an input shaft of the Renschal Bf130. The drive pinion shaft 31 is a cast iron oil pan 2 of the internal combustion engine 1.
It is rotatably supported by a differential case 32 integrally molded with the differential case 9.

A drive pinion 33 made of a bevel gear is provided at the end of the drive pinion shaft 31, and the drive pinion meshes with a ring gear 34 of a front differential gear [30].

The hydraulic control devices 9 and 22 are operated based on control signals from the electric control WJ device 45 to control the gear shift of the transmission 7 and the engagement/disengagement control of the initial arrival control clutch 21. ing. The handle device 45 includes a microcomputer with a general structure, and receives information regarding the vehicle speed from the vehicle speed sensor 46, information regarding the throttle opening of the internal combustion engine 1 from the throttle opening sensor 47, and information regarding the manual shift range from the manual shift position sensor 48. The four manual selector switches provide information on whether or not the center differential lock mode is in effect, and basically follow a predetermined shift pattern depending on the manual shift range, vehicle speed, and throttle opening. A control signal for controlling the gear change of the transmission 7 is output to the hydraulic control device 9, and when in the center differential lock mode, in a specific driving state determined by the vehicle speed and the throttle opening representing the engine output, In other words, a control signal that causes the differential control clutch 21 to engage during operation other than high-speed steady operation is provided, and a control signal that prohibits engagement of the initial arrival control clutch 21 at other times, that is, a control that releases the differential control clutch 21. The signal is output to a hydraulic control (IIl device 22).This differential control clutch 21
The engagement and release control is specifically performed according to a flowchart as shown in FIG. 2, for example.

Differential control clutch 2 according to the flowchart as described above.
As shown in FIG. 3, when the vehicle speed is above a predetermined value (forced release vehicle speed) V2 and below a larger predetermined value (forced release vehicle speed) V4, the throttle opening is θ is a predetermined value (r between forced release throttles)
! 1) If θ1 or less, the differential control clutch 21 is released even in the center differential lock mode, and it is avoided that circulating torque is generated in the power transmission system due to the difference in rotational speed between the front wheels and the rear wheels. . Also, the vehicle speed V is a predetermined value v
4 or more, the differential control clutch 21 is released even in the differential lock mode, and the front wheels are Circulating torque is prevented from being generated in the power transmission system due to the difference in rotational speed between the front wheels and the rear wheels.

Even when traveling at high speed, that is, even when the vehicle speed V is equal to or higher than the predetermined value V2, when the throttle opening is large, the differential control clutch 21 is not forcibly released, and the differential control clutch 21
Through this engagement, a four-wheel drive state in which the front and rear wheels are directly connected is obtained, resulting in excellent drive performance.

In this embodiment, the high vehicle speed range is divided into two, with the higher vehicle speed region being a forced release region for the throttle opening of the differential control clutch 21.

In other words, the engagement prohibited area has been expanded.

Note that when the vehicle speed V is below the predetermined value V2, the differential control clutch 21 can be engaged even when the throttle opening is low.

In order to prevent a hunting phenomenon from occurring in the engagement and disengagement of the differential control clutch 21 due to repeated changes in throttle opening or vehicle speed, the set vehicle speed from release to engagement of the differential clutch 21 is V+ and v3 are the forced release vehicle speeds, respectively. v
2 and v3, respectively, and the forced release release throttle openings θ2 and θ4 are the forced release throttle openings θ.
! and θ3 to provide so-called hysteresis.

The engagement prohibited region of the differential control clutch 21 relative to the throttle opening may be increased proportionally as the vehicle speed increases, and the control characteristics in this case are shown by the dashed line in FIG.

The control device that controls the differential control clutch 21 as described above and the control 'tA position that controls the speed change of the transmission 7 may be the same, and the vehicle speed sensor 46 for controlling the differential control clutch 21 may be used in common. As for the throttle opening sensor 47, one provided for speed change control may be used.
A dedicated sensor is not required for controlling the differential control clutch 21, and there is no need to provide a new sensor, and the circuit configuration of the control device itself is simplified by making these sensors common. Become.

In the above-described embodiment, the differential control clutch 21 is controlled in an on-off manner, but the present invention is not limited to this, and the differential control clutch 21 controls the engagement force. The engagement force may be quantitatively and variably controlled so that when the vehicle speed is above a predetermined value and the engine output is below a predetermined value, the engagement force may be reduced so that slippage may occur, that is, an incomplete engagement state may occur.

The engine output may be detected by the accelerator pedal depression amount, fuel injection amount, shaft output torque, etc. in addition to the throttle opening.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited thereto.
It will be apparent to those skilled in the art that numerous embodiments are possible within the scope of the invention.

[Brief explanation of the drawing]

FIG. 1 is a skeleton diagram showing an example of a four-wheel drive device used to implement the control method according to the present invention, FIG. It is a graph showing the control characteristics in the control method of the four-wheel drive device according to the present invention. 1... Internal combustion engine, 2... Vehicle automatic transmission, 3...
- Four-wheel drive transfer device, 4... converter case, 5... hydraulic torque converter, 6... transmission case, 7... transmission device, 8... input member. 9...Hydraulic control I! ! i position, 10... center differential device, 11... carrier, 12...
Planetary Binion, 13... Sun Gear, 14...
ring gear. 15... Rear wheel drive shaft, 16... Front wheel drive intermediate shaft,
17... Front wheel drive shaft, 18. One... Sprocket, 20... Endless chain, 21... Differential control clutch, 22... Hydraulic control device, 23... Universal joint, 2
4...Rear propeller shaft, 25...Universal joint, 26.
...Front propeller shaft, 27...Universal joint, 29.
··Oil pan. 30...Front differential device, 31...
- Drive pinion shaft, 32... Differential case, 33... Drive pinion, 34... Ring gear, 45... Control device, 46... Vehicle speed sensor,
47...Throttle opening sensor, 48...Manual shift position sensor, 4...Manual changeover switch

Claims (1)

[Claims] A center differential device that performs a differential operation between rear wheels and front wheels; and a differential control clutch that selectively stops the differential operation of the center differential device and selectively directly connects the rear wheels and the front wheels. A method for controlling a four-wheel drive system having a four-wheel drive system, wherein the engaging force of the differential control clutch is reduced when the vehicle speed is above a predetermined value and the engine output is below a predetermined value. Control method.