JPH0825401B2 - 4 wheel drive transfer structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a four-wheel drive vehicle, and more particularly to a transfer structure for a four-wheel drive vehicle capable of switching between a two-wheel drive mode and a full-automatic four-wheel drive mode. .

(Prior Art) A four-wheel drive vehicle in which front wheels and rear wheels are driven by output torque of an engine or a transmission is
Although it has the advantage that good running performance can be obtained on bad roads such as snow roads, it has the disadvantage that the fuel consumption of the engine is inferior to that of two-wheel drive vehicles. A four-wheel drive vehicle capable of switching drive modes has been proposed.

Further, as a four-wheel drive vehicle of this type of two-wheel / four-wheel drive switching type, for example, as disclosed in Japanese Patent Laid-Open No. 60-172764, a so-called fully automatic four-wheel drive in a four-wheel drive mode. There is a four-wheel drive vehicle that is designed to perform. In this four-wheel drive vehicle, the front wheel is always driven by the transmission located at the front of the vehicle, and the power transmission to the rear wheels can be connected / disconnected.
A car-based viscous in which a large number of plates, which are alternately coupled to these members, are arranged between a pair of driving-side and driven-side rotating members, and viscous fluid is filled around the plates. A structure using a coupling, in which the transmission output shaft is directly connected to the front wheels and the rear wheels are connected via a propeller shaft having a two-wheel to four-wheel drive switching mechanism and the viscous coupling. It is said that. According to this four-wheel drive vehicle, when the four-wheel drive mode is selected by the switching mechanism,
When there is no difference in rotational speed between the rear wheels, the viscous coupling does not transmit torque, so only the front wheels are driven.
Wheel drive state, but during cornering and drive wheels (front wheels)
When there is a difference in rotational speed between the front and rear wheels when the vehicle is slipping, etc., the viscous coupling transmits torque to the rear wheels according to the difference in rotational speed and automatically shifts to the four-wheel drive state. Therefore, good traveling performance can be obtained even when cornering or when the drive wheels slip.

By the way, in a four-wheel drive vehicle capable of switching between the two-wheel drive mode and the full-auto four-wheel drive mode as described above, the transmission output shaft and the viscous coupling are cut off by the switching mechanism. When traveling in the drive mode, the driven-side rotating member of the viscous coupling rotates in conjunction with the rotation of the wheel that is the driven wheel, and at this time, the plate connected to the rotating member and the driving-side rotation are rotated. The plate connected to the member rotates integrally with the action of the viscous fluid to generate inertial resistance. Then, this becomes the rotational resistance of the driven wheels and increases the drive loss of the four-wheel drive vehicle, which causes deterioration of fuel consumption in the two-wheel drive mode in which economic efficiency is important.

To solve this problem, for example, a structure disclosed in Japanese Patent Laid-Open No. 56-135320, that is, a drive shaft of a wheel that is a driven wheel at the time of two-wheel drive is equipped with a clutch as a freewheel mechanism to drive the two-wheel drive. It is conceivable to apply the configuration in which the clutch is disengaged at times to the four-wheel drive vehicle using the viscous coupling disclosed in the above-mentioned JP-A-60-172764.

According to this, the rotation of the wheel that is the driven wheel during two-wheel drive is not transmitted to the viscous coupling, and the rotational resistance of the driven wheel is reduced.

(Problems to be Solved by the Invention) However, in the four-wheel drive vehicle based on the FF vehicle as described above, a configuration including a viscous coupling and a freewheel mechanism is provided by an output shaft of a transmission extending in the vehicle longitudinal direction. When trying to apply to a four-wheel drive vehicle based on an FR (front engine / rear drive) vehicle that always drives the rear wheels, the following problems occur.

That is, in this case, the two-wheel / four-wheel switching mechanism and the viscous coupling are arranged on the propeller shaft toward the front wheels, which are driven wheels during two-wheel drive. Therefore, a transmission mechanism such as a chain or sprocket that transmits power from the transmission output shaft that constantly drives the rear wheels to the front wheel side propeller shaft will rotate even during two-wheel drive, and a freewheel mechanism will be provided. Nevertheless, the drive loss in the two-wheel drive mode will not be sufficiently reduced. Further, since the switching mechanism and the viscous coupling are arranged on the propeller shaft on the front wheel side, which is different from the transmission output shaft, the transfer structure becomes large in size. This problem also applies to a four-wheel drive vehicle based on an RF (rear engine / front drive) vehicle.

Therefore, the present invention provides a FR-based or RF-based four-wheel drive vehicle capable of switching between the two-wheel drive mode and the fully-automatic four-wheel drive mode as described above, while suppressing an increase in the size of the structure. An object of the present invention is to prevent unnecessary rotation of a viscous coupling and a transmission mechanism during wheel drive to improve fuel economy in the two-wheel drive mode.

(Means for Solving the Problems) That is, the transfer structure of the four-wheel drive vehicle according to the present invention is configured such that the output shaft of the transmission extending in the front-rear direction of the vehicle body is extended in the same direction so that either one of the front wheels or the rear wheels of the vehicle is extended. A four-wheel drive vehicle configured to drive a wheel and to drive the other front wheel or the rear wheel by a second output shaft arranged in parallel with the transmission output shaft. A viscous coupling is arranged, and one rotating member of the viscous coupling is connected to the output shaft so as to be connectable / disconnectable via a switching mechanism, and the other rotating member is connected to the second output shaft via a transmission mechanism. Further, a freewheel mechanism for connecting and disconnecting the second output shaft to a wheel driven by the output shaft is provided on the drive shaft. The free wheel mechanism is disconnected when the transmission output shaft and one rotating member of the viscous coupling are disconnected by the switching mechanism.

(Operation) According to the above configuration, when the transmission output shaft and one rotating member of the viscous coupling are shut off by the switching mechanism, the torque from the output shaft causes one of the front wheels or the rear wheels to rotate. A two-wheel drive mode that is transmitted only to Further, if the output shaft is connected to one rotating member of the viscous coupling, the output shaft is also connected to the other wheel via the viscous coupling, and the output shaft is connected to the one wheel in accordance with the rotational speed difference with the one wheel. A fully automatic four-wheel drive mode in which torque is also transmitted to the other wheel can be obtained. In the two-wheel drive mode, the freewheel mechanism disconnects the other (driven side) rotating member of the viscous coupling from the other wheel (driven wheel), so that the viscous cup is interlocked with the driven wheel. The rotation member on the driven side of the ring or the plate connected thereto is prevented from rotating, and the rotation resistance of the driven wheel is reduced accordingly.

Further, the viscous coupling is arranged on the transmission output shaft that transmits power to the wheels that are constantly driven, and one rotating member of the viscous coupling is connected to the output shaft via the switching mechanism in a connectable and disconnectable manner. In the two-wheel drive mode in which the switching mechanism is disconnected, the portion from the viscous coupling and the other rotating member of the viscous coupling to the second output shaft via the transmission mechanism rotates in conjunction with the transmission output shaft. Therefore, the drive loss in the two-wheel drive mode is further reduced.

(Example) Hereinafter, the Example of this invention is described.

First, the overall configuration of a four-wheel drive vehicle according to this embodiment will be described with reference to FIG. 1. In this four-wheel drive vehicle, a power plant including an engine 1, a transmission 2, and a transfer device 3 at the front of the vehicle body. Is installed. The engine 1 is arranged so that its output shaft 4 extends in the front-rear direction of the vehicle body, and the transmission 2 also has an input shaft 6 connected to the engine output shaft 4 via a clutch 5 and the same axis line as the input shaft 6. The output shaft 7 is arranged in the front-rear direction of the vehicle body. The output shaft 7 of the transmission 2 extends rearward and the transfer device 3
The left and right rear wheels 11 and 11 are connected to each other through a propeller shaft 8, a rear differential 9, and rear axles 10 extending from the rear differential 9 to the left and right. A front wheel output shaft 12 parallel to the transmission output shaft 7 projects forward from the transfer device 3, and a propeller shaft 13, a front differential 14, and a front axle 1 extending left and right from the front differential 14.
It is connected to the left and right front wheels 16, 16 via 5, 15. Here, a freewheel mechanism 20 described later is provided on the front axle 15 between the front differential 14 and one front wheel 16.

Next, referring to FIG. 2, the internal structure of the transfer device 3 will be described. In the case of this embodiment, the transmission output shaft 7 penetrating through the device 3 is first from the front.
The output shaft 7 ₁ , the second output shaft 7 ₂ , and the third output shaft 7 ₃ are connected in a line, and the viscous coupling 30 is provided at the rear of the second output shaft 7 ₂ and the drive mode is provided at the front. Switching mechanisms 40 are arranged respectively, and between the intermediate portion of the second output shaft 7 ₂ and the output shaft 12 for the front wheels, there is a rotatably supported second output shaft 7 ₂ . 1 sprocket 51 and front wheel output shaft 12
The second sprocket 52 fixed to the and two sprockets 5
A front wheel drive transmission mechanism 50 including a belt 53 wound between 1, 52 is provided.

The viscous coupling 30 is an inner case 31,
The outer case 32 and a large number of plates 33 arranged between the cases 31 and 32 and alternately coupled to the cases 31 and 32.
... 33, and the viscous fluid is filled around the plates 33 ... 33. Then, the inner case 31 is rotatably supported cylindrical extension shaft 31a extending forward is continuously provided on the second output shaft 7 _2, also, the transmission mechanism 50 on the extension shaft 31a First to make up
The sprocket 51 is rotatably supported, and the sprocket 51 and the outer case 32 are joined together.

Further, the switching mechanism 40, a second output shaft 7 can freely rotate relative to each other _2, the inner case extension shaft 31a and the first sprocket 51
The first, second, and
Third splines 41, 42, 43 and these splines 41-43
And a sleeve 44 that is slidably fitted over the lever 45.
The sleeve 44 is configured to slide via the 46 and the fork 47. Then, in a state in which the sleeve 44 is located on the leftmost side as shown in the drawing, the first to third
When the splines 41 to 43 are separated, slide a certain amount from this position to the right side, and then the first and second splines 41, 4
2 is coupled and the inner case 31 of the second output shaft 7 ₂ and the viscous coupling 30 is connected, also when brought into a certain amount slid further right sleeve 44, the first to third splines 41-43 are connected, so that the three parties of the first sprocket 51 of the inner case 31 and the transmission mechanism 50 of the second output shaft 7 ₂ and viscous cut ring 30 described above is bonded.

On the other hand, the free wheel mechanism 20 provided on the front axle 15 between the front differential 14 and the one front wheel 16 shown in FIG. 1 is configured as shown in FIG. That is, the freewheel mechanism 20 is a hydraulic clutch mechanism that connects and disconnects the front axle 15 divided into the front differential 14 side and the front wheel 16 side, and the end portion of the front axle 15 on the front differential side 15a. The drum 21 fixed to the front and the hub 22 fixed to the end portion of the front wheel side 15b inside and outside, and the drum 21 and the hub.
Multiple clutch plates that are alternately connected to these between 22 and
23 ... 23 are arranged and a piston 24 is fitted in the drum 21 to form a hydraulic chamber 25 at the back of the piston 24.
When the hydraulic pressure is not supplied to the hydraulic chamber 25, the piston 24 is retracted by the return spring 26, so that the clutch plates 23 ...
When the hub 22, that is, the front differential side 15a and the front wheel side 15b of the front axle 15 are disconnected, and the hydraulic pressure is supplied to the hydraulic chamber 25 from the outside, the piston 24 moves forward to move the clutch plates.
By fastening 23 ... 23, the front differential side 15a and the front wheel side 15b of the front axle 15 are connected via the drum 21 and the hub 22. The supply and discharge of the hydraulic pressure to and from the hydraulic chamber 25 are performed in conjunction with the sliding operation of the sleeve 44 in the switching mechanism 40, and the hydraulic chamber 25 is located only when the sleeve 44 is located at the leftmost side shown in FIG. The supply of hydraulic pressure to the unit is stopped (the hydraulic pressure is discharged).

Next, the operation of the above embodiment will be described. First, when the sleeve 44 of the switching mechanism 40 in the transfer device 3 is slid to the leftmost side as shown in FIG. 2, the transmission output shaft 7 (second output shaft) 7 ₂ ) is not coupled to either the inner case 31 of the viscous coupling 30 or the first sprocket 51 of the front wheel transmission mechanism 50, the torque output from the engine 1 or the transmission 2 to the output shaft 7 is The propeller shaft 8 for driving rear wheels from the output shaft 7 without being divided.
It is transmitted to the side and drives the left and right rear wheels 11, 11 via the rear differential 9 and the rear axles 10, 10. Therefore, in this case, the rear wheel 1
It becomes the two-wheel drive mode in which only 1 and 11 are driven.

If the sleeve 44 of the switching mechanism 40 is slid rightward from the position shown in FIG. 2 and the first and second splines 41 and 42 are connected, the inner case of the transmission output shaft 7 and the viscous coupling 30 is connected. Since the output shaft 7 transmits torque to the rear wheels 11 and 11 side as described above, the output shaft 7 simultaneously transmits the viscous coupling 30, the transmission mechanism 50, the front wheel output shaft 12, the propeller shaft 13, and the front shaft. Differential
It will be connected to the left and right front wheels 16, 16 via 14 and the front axles 15, 15. In this case, since the hydraulic pressure is supplied to the hydraulic chamber 25 in the freewheel mechanism 20 on one of the front axles 15, the front differential side 15a and the front wheel side 15b of the front axle 15 are connected. Is in a state.

In this case, in the viscous coupling 30, the inner case 31 is connected to the rear wheels 11, 11 via the output shaft 7.
The outer case 32 has a transmission mechanism.
Since it is interlocked with the front wheels 16 and 16 via 50, when there is no difference in rotation speed between the front and rear wheels, the difference in rotation speed between the cases 31 and 32 becomes equal and torque is not transmitted. Although only 11 is driven, it becomes a two-wheel drive state, but when a difference in rotation speed occurs between the front and rear wheels, both cases 31 and 32 relatively rotate and the viscous coupling 30 becomes a torque transmission state. As a result, a part of the torque is output from the output shaft 7 to the transmission mechanism 50 or the front wheel output shaft 12 side via the viscous coupling 30, and the front wheels 16 and 16 are automatically driven to the four-wheel drive state. Will be moved to. In this way, the fully automatic four-wheel drive mode is obtained, and good running performance is obtained during cornering or when the rear wheels 11, 11 that are the drive wheels slip.

Further, when the sleeve 44 of the switching mechanism 40 is stroked to the rightmost position, the transmission output shaft 7 has the inner case 31 of the viscous coupling 30.
In addition to being coupled to the first sprocket 51 of the transmission mechanism 50, the output shaft 7 is connected to the left and right front wheels 16 via the transmission mechanism 50, the front wheel output shaft 12, the front differential 14, and the front axles 15, 15. 16
Thus, a direct connection four-wheel drive mode in which the torque of the output shaft 7 is directly transmitted to both the rear wheels 11 and 11 and the front wheels 16 and 16 is obtained.

However, in the above two-wheel drive mode, the switching mechanism
The front wheels 16, 16 that are disconnected from the transmission output shaft 7 by the 40 are driven wheels that rotate as the vehicle travels. At this time, on the front axle 15 between the front differential 14 and one of the front wheels 16. In the freewheel mechanism 20 provided in the drum 21, since the hydraulic pressure is not supplied to the hydraulic chamber 25, the drum 21
Then, the hub 22, that is, the front differential side 15a and the front wheel side 15b of the front axle 15 are disconnected. Therefore, at the same time that the one front wheel 16 freely rotates, the other front wheel 16 also causes each of the constituent gears of the front differential 14 to idle, and the rotation of these front wheels 16 and 16 causes the propeller shaft 13 and the front wheel output shaft 12 to rotate. Also, it is not transmitted to the viscous coupling 30 side via the transmission mechanism 50. As a result, in the viscous coupling 30, not only the inner case 31 that is disconnected from the transmission output shaft 7 is not driven from the rear wheels 11 and 11, but also the outer case 32 is driven from the front wheels 16 and 16. It is also blocked, and the whole is completely separated from the front and rear wheels. This prevents the viscous coupling 30 from being a resistance to the rotation of the front wheels 16 and 16 that are driven wheels during two-wheel drive, reduces the rotational resistance of the front wheels 16 and 16, and reduces the transmission mechanism 50, It is also avoided that the front wheel output shaft 12, the propeller shaft 13 and the like rotate in conjunction with the transmission output shaft 7.

The free wheel mechanism 20 is not limited to the hydraulic clutch type as described above, but may be an electromagnetic clutch, a mechanical clutch, or the like, and as shown by reference numeral 20 'in FIG.
It may be provided between 12 and the front differential 14.

(Effects of the Invention) As described above, according to the present invention, a FR-based or RF-based four-wheel drive mode capable of switching between a two-wheel drive mode and a fully automatic four-wheel drive mode using a viscous coupling. In the driving vehicle, since the free wheel mechanism is provided to disconnect the drive shaft of the wheel that becomes the driven wheel when the two-wheel drive mode is selected, the viscous coupling acts as a resistance to the rotation of the driven wheel when traveling in the mode. This is prevented, and the rotational resistance of the driven wheel is reduced. Further, when the two-wheel drive is performed, the transmission mechanism to the wheels that are driven wheels does not rotate unnecessarily in conjunction with the transmission output shaft. This prevents an increase in drive loss during traveling in the two-wheel drive mode and improves fuel economy.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a skeleton diagram showing the overall structure of a four-wheel drive vehicle, and FIGS. 2 and 3 are cross-sectional views showing a transfer device and a freewheel mechanism in the four-wheel drive vehicle, respectively. It is a figure. 7 ... Transmission output shaft, 8,10 ... Rear wheel drive shaft (propeller shaft, rear axle), 11 ... Rear wheel, 12 ... Second output shaft (front wheel output shaft), 13,15 ... … Front wheel drive shaft (propeller shaft, front axle), 16 …… front wheel, 20 …… freewheel mechanism, 30 …… viscus coupling, 31,32 …… rotating member (inner case, outer case), 40 …… Switching mechanism.

Claims (1)

[Claims] Claim: What is claimed is: 1. A transmission output shaft extending in the front-rear direction of a vehicle body is extended in the same direction to drive either one of front wheels and rear wheels, and a second output arranged parallel to the transmission output shaft. In a four-wheel drive vehicle configured to drive the other front wheel or rear wheel by a shaft, a viscous coupling is arranged on the transmission output shaft, and one rotating member of the viscous coupling is switched to the output shaft. And connecting the other rotating member to the second output shaft via a transmission mechanism, and driving from the second output shaft to a wheel driven by the output shaft. A freewheel mechanism for connecting and disconnecting the shaft is provided on the shaft, and when the transmission output shaft and one rotating member of the viscous coupling are disconnected by the switching mechanism, Transportation structure of a four-wheel drive vehicle, characterized in that so as to cut the freewheel mechanism.