JPS5826636A - Full-time four-wheel drive car - Google Patents

Abstract

PURPOSE:To provide a full-time four-wheel drive car without any abatement in drivability by mounting a spring to a transfer clutch so as to be half clutched in normal condition and engaging it according to the state of slippage between axles. CONSTITUTION:A transfer clutch 22 is a multiple disc clutch and is fit with a hydraulic piston 32 and a diaphragm spring 31. Normally, the clutch is kept in half-clutched by the effect of the diaphragm spring 31. A control circuit 42 opens a solenoid valve 38 to supply oil pressure to the clutch on the basis of a difference between revolution speeds of front and rear axles. The clutch is thereby engaged to drive four wheels without any difference in speeds of the axles.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a full-time four-wheel drive vehicle that always drives the front and rear wheels in four-wheel drive, and particularly relates to a system in which the transmission systems of the front and rear wheels are mechanically directly connected by a transfer clutch. .

In such four-wheel drive vehicles, a central differential is attached to the transmission system between the front and rear wheels, and the front differential is attached to the transmission system between the front and rear wheels.

For example, Japanese Patent Application Laid-Open No. 55-72420 has proposed a system that absorbs the rotational speed difference caused by the difference in the turning radius of the rear wheels, but this system also requires a differential lock mechanism for the central differential. required, and the structure and control become very complex.

Therefore, in order to eliminate such problems, usually the previous
Although it is a part-time type in which the drive is two-wheel drive by one of the rear wheels and four-wheel drive is possible when necessary, the applicant has already installed a direct connection type in which a transfer clutch is installed in the transmission system between the front and rear wheels. have been proposed. By the way, with this system, when turning in four-wheel drive, the front and rear wheels are directly connected and cannot absorb the difference in rotational speed between them, so torsional torque is generated between the front and rear drive shafts. This results in a large internal circulating torque, resulting in the so-called tight corner braking phenomenon, which is the same as braking. This results in deterioration in driving performance, such as a heavy steering wheel, and progression of tire wear due to the torque being forcibly released due to slippage between the tires and the road surface.

In view of these circumstances, the present invention is a direct connection system in which a transfer clutch is installed in the transmission system between the front and rear wheels, and the internal circulation torque of the drive system that occurs when turning during normal four-wheel drive driving is reduced. To provide a full-time four-wheel drive vehicle which can absorb the slippage easily by the elements of a clutch and can fully exhibit the functions of a four-wheel drive vehicle when slip occurs between the front and rear wheels. The purpose is to

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. First, a transmission system with an automatic transmission will be described as an example of a four-wheel drive vehicle to which the present invention is applied in FIG. It is connected to the turbine shaft 3 through the turbine shaft 3, and transmission is further configured from the turbine shaft 3 to the automatic transmission 4. The automatic transmission 4 is, for example, a three-speed one, in which the power from the Ravigneaux-type planetary gear 5 and the turbine shaft 3 is input to the gear 5! Clutch with selective input 6.7
, and a one-way clutch 8, a brake 9, and a brake band 10 for selectively locking each element of the gear 5, and the power shifted from the automatic transmission 4 is taken out forward by an output shaft 11. It is transmitted to a pair of glue duction drives and driven gears 12.13.

Further, a front wheel final reduction device 14 is disposed at the lower part between the torque converter 2 and the automatic transmission @ 4, and a drive pinion formed on one side of the shaft 1G of the reduction driven gear 13 is attached to the crown gear 15 of this device 14. 17 are engaged with each other for direct driving.

The transfer drive shaft 1 is connected to the other shaft 16 of the gear 13.
8 are connected and extend rearward, and are connected to a transfer drive and driven gear 20, 21 of a transfer device 19 mounted at the rear of the automatic transmission 4. and,
This transfer driven gear 21 is connected to a rear drive shaft 23 by a hydraulic clutch type transfer clutch 22, and the rear drive shaft 23 is further configured to transmit power to a rear wheel final reduction device 25 via a propeller shaft 24, and the clutch 22 is engaged. Due to the combination, power is also transmitted to the rear wheels for four-wheel drive driving.

In FIG. 2, the hydraulic clutch type transfer clutch 22 will be described in detail.
Clutch plates 21 of the hub 26 integrally attached to the rear drive shaft 23 and clutch plates 29 of the drum 28 integrally attached to the rear drive shaft 23 are arranged alternately, and pressure is applied to one side of these clutch plates 27 and 29. A plate 30 is provided to press and engage the two. The pressure plate 30 has a piston contact portion 30a near the center and a spring locking portion 30 slightly outside of the piston contact portion 30a.
By locking the diaphragm spring 31 between the locking portion 30b and the drum side, the clutch plates 27 and 29 are always engaged in a slidable half-clutch state. Further, a piston 32 is assembled inside the drum 28, and this piston 32 is attached to a piston chamber 33.
The clutch plate 2129 is moved against the return spring 34 by the hydraulic pressure supplied to the clutch plate 30, thereby hitting the contact portion 30a of the pressure plate 30 and pressing it, thereby completely engaging the clutch plate 2129 as one unit.

The piston chamber 33 contains the piston 32. An oil passage 35 in the rear drive shaft 23 communicates with an oil pump 36 assembled to the automatic transmission 4, and a switching valve 38 is connected to the oil passage 35 depending on whether or not the solenoid 37 is energized. It is provided to shut off and drain the piston chamber 33. Further, as shown in FIG. 1, a front wheel rotation sensor 39 is installed near the transfer device 19 on the front wheel side, for example, around the transfer driven gear 21, and a sensing gear 40 is installed on the rear drive shaft 23 on the rear wheel side. A rear wheel rotation sensor 41 is installed, and these sensors 39 and 41 are connected to the switching valve 3 via a control circuit 42.
It is electrically connected to the solenoid 31 of No. 8.

By the way, in the clutch 22, the drive side hub 26
In contrast to the clutch plate 2γ, even if the clutch plate 29 of the driven side drum 28 is in a released state, it is rotated by the road surface during normal driving, so that it rotates in the same direction at a constant speed. Therefore, although the power transmission force to the rear wheel side is reduced even when the clutch is always in the half-half state, problems such as heating due to slippage do not occur.In this case, the clutch plate 27.
The half-clutch engagement force of 9 is set so as to temporarily slip and easily absorb the internal circulation torque when the vehicle turns.

Also, to explain the contents of the control circuit 42, it is configured to estimate and obtain the slip rate based on the rotational speeds of the front wheels and rear wheels from the rotation sensors 39 and 41. When the gripping force of the front wheels decreases and the slip ratio exceeds a set value when the vehicle is traveling in a place, the solenoid 31 of the switching pulp 38 is energized, and this is canceled by, for example, a timer.

Next, the operation of the four-wheel drive vehicle according to the present invention described above will be explained.During normal driving, the slip ratio is very small, so the solenoid 37 of the switching pulp 38 is in a de-energized state. The oil passage 35 is shut off and the piston chamber 33 of the transfer clutch 22 is drained of oil. Therefore, in the clutch 22, the piston 32 is moved backward by the spring 34, and the clutch plate 27 is moved back by the spring force of the diaphragm spring 31.
．． 29 is engaged in a half-clutch state. In this way, all of the gear-shifted power from the automatic transmission 4 is directly transmitted to the front wheels via the front final reduction gear [14], and a portion of the power is transmitted by a transmission force corresponding to the half-clutch engagement force of the transfer clutch 22. But even more rear wheel reduction 311if! The signal is also transmitted to the rear wheels via the gear 25, and in this way four-wheel drive driving is always performed using the front and rear wheels with priority given to the front wheels.

In such four-wheel drive driving where the front wheels are prioritized, when internal circulation torque is generated due to the difference in the turning radius of the front and rear wheels during turning, the transfer clutch 22 is engaged in a half-clutch state. Clutch plate 27.
29 to absorb internal circulation torque. Incidentally, even if the diameters of the front and rear tires are different due to a difference in tire air pressure or loading of cargo, and the above-mentioned internal circulation torque is generated, that torque can be absorbed in the same way.

On the other hand, when the front wheel slips in a road surface condition where slips are likely to occur, the control circuit 42 energizes the solenoid 37 to switch the switching pulp 38, which connects the oil passage 35 and supplies oil to the piston chamber 33 of the transfer clutch 22. . Therefore, the piston 32 is moved by the high oil pressure in the piston chamber 33, and the clutch plates 27 and 29 are moved to the above-mentioned diaphragm spring 3 via the pressure plate 30.
In addition to the spring force of 1, there is a strong pressure contact, so that the plates 27, 29 are completely integrally engaged. Therefore, in this case, power is transmitted to the rear wheels equally as to the front wheels, resulting in a complete four-wheel drive driving state in which the driving force of the front and rear wheels is the same, thereby ensuring stable driving and driving the front and rear wheels equally. If one of the two gets stuck in the mud, it is easy to get out of it.

As is clear from the above description, according to the present invention, in a direct-coupling full-time four-wheel drive vehicle using the transfer clutch 22, the transfer clutch 22 absorbs the internal circulation torque during turning. Increase in force and prevent abnormal tire wear. In this case, the characteristics of the transfer clutch 22 are used to engage it in a slippery half-clutch state to absorb internal circulating torque, so the structure is simple, no special control is required, and there are no inconveniences. Does not occur. In particular, since the vehicle is running in four-wheel drive with the front wheels dominant, it is possible to maintain good running performance. In addition, in cases where slipping occurs, complete 4-way
Since the vehicle automatically switches to wheel drive, it can fully demonstrate its performance as a four-wheel drive vehicle.

[Brief explanation of the drawing]

FIG. 1 is a skeleton diagram showing a transmission system of an example of a four-wheel drive vehicle to which the present invention is applied, and FIG. 2 is a configuration diagram showing an embodiment of the present invention. 4... Automatic transmission, 14... Front wheel final reduction gear, 22
・・・Hydraulic clutch type transfer clutch, 25...
・Rear wheel final reduction gear, 27.29...Clutch plate, 30...Pressure plate, 31...Diaphragm spring, 32...Piston, 35...Oil passage, 31...Solenoid, 38 ...Switching pulp, 39
．． 41... Rotation sensor, 42... Control circuit.

Claims (1)

[Scope of Claims] A transmission is configured to transmit power directly to one of the front and rear wheels, and also to the other of the front and rear wheels via a hydraulic clutch type transfer clutch, and the clutch is configured to transmit power directly to one of the front and rear wheels. Normally, the clutch is in a half-engaged state where it can be slipped by a spring, and before the above. Full-time type 4, which is characterized by a two-stage control system that, when slippage occurs between the rear wheels, suppresses the piston to achieve a completely integrated state of engagement.