JPH01103543A - Transfer structure in four-wheel-drive vehicle - Google Patents

Abstract

PURPOSE:To aim at miniaturization by installing a one-way clutch interposingly between the front-wheel and rear-wheel output members of a center differential. CONSTITUTION:A sprag type one-way clutch mechanism 37 is installed on a front axle shaft 8 at the left of a transfer gear 35, and when rotation at the side of an outer race 37a is turned speedier than that at the side of an inner race 37b, a sprag 37c is set up so as to transmit driving force at the side of the outer race 37a to the side of the inner race 37b. Consequently, in the state that front wheels are turned speedier than rear wheels, the one-way clutch mechanism 37 comes into a state of being freed and these wheels are raced, whereby driving force (driving force to the front wheels) out of a differential case 26 will not be transmitted to the transfer gear 35, namely, the rear wheels. In the case of reverse, the one-way clutch mechanism 37 is locked so that the driving force is transmitted to the front wheels from the rear wheels. With this constitution, miniaturization is thus attainable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-wheel drive vehicle, and particularly to a transfer structure that transmits driving force from an engine to front and rear wheels.

[Prior art]

Traditionally, one of the front and rear wheels of a four-wheel drive vehicle
In order to prevent the drive force from being transmitted to the other wheel due to wheel slip, or when the rotation difference between the front and rear wheels is large during cornering, the center differential function increases the drive force to the wheel on the high rotation side. In order to limit and transmit appropriate driving force to the wheels on the low rotation side and improve cornering performance, we use a so-called viscous coupling in which a sealed case is filled with a fluid such as high viscosity silicone oil. It is known that the relative rotation of the front and rear wheels is restricted (see British Patent No. 1252753).

On the other hand, the present applicant has filed an earlier application (Patent Application No. 6l-21307).
In 1), a planetary gear type center differential is installed on the side of the inter-wheel differential installed between either the front wheels or the rear wheels, and the other inter-wheel differential is installed on the opposite side of the center differential from the above-mentioned inter-wheel differential. A transfer gear that transmits power to the wheels is installed, and a viscous coupling that restricts relative rotation between the differential case of the inter-wheel differential and the transfer gear is installed on the opposite side of the transfer gear from the center differential, resulting in a compact overall design. I suggested something like this.

For reference, in a four-wheel drive vehicle, a one-way clutch is installed on either side of the inter-wheel differential installed on the front and rear axles, without a center differential in the drive transmission system, to transfer the driving force from the engine to the wheels. There is a device configured to intermittent the time depending on the driving situation (see Japanese Patent Application Laid-Open No. 110623/1983).

For example, when the above-mentioned one-way clutch is installed in the front wheel differential, the driving force from the engine is distributed and transmitted to the front and rear wheel differentials via the transmission and transfer device, but the rotation of the front wheel axle is When the vehicle is ahead of the vehicle, that is, when cornering, the system is configured so that the vehicle changes from a four-wheel drive state to a two-wheel drive state in which the front wheels are spinning, and in the above-mentioned driving situations, the vehicle is placed in two-wheel drive mode to smoothly corner. It was made to be done.

[Problem that the invention seeks to solve]

In the four-wheel drive vehicle described in the above-mentioned Japanese Patent Application Laid-Open No. 61-110623, in driving conditions where the rotation difference between the front and rear wheels becomes large, such as when turning, the vehicle is driven in two-wheel drive. The loss of driving force is large, resulting in reduced drivability and poor driving feeling.

Furthermore, there is a problem in that the behavior and turning characteristics of the vehicle vary greatly when switching from four-wheel drive to two-wheel drive during cornering.

On the other hand, in a four-wheel drive vehicle with a transfer structure, which is equipped with the above-mentioned viscous coupling for the purpose of limiting the function of the center differential and transmitting appropriate driving force to the front and rear wheels to improve driving performance, the It is possible to drive by regulating the driving force distribution effect of the center differential caused by the small rotation difference between the front and rear wheel differentials during normal driving and the large rotational difference between the front and rear wheel differentials when turning Smooth four-wheel drive performance can be achieved by smoothly distributing the driving force and preventing loss of driving force and uneven wear of the wheels during driving.

However, the viscous coupling is difficult to miniaturize due to its structure, which incorporates a large number of plates consisting of an inner plate and an outer plate, and its cost is high.

On the other hand, many electronically controlled brake control systems, so-called anti-skid brakes, have been put into practical use to improve the drivability and drivability of four-wheel drive vehicles as well as shorten the stopping distance during braking. In a four-wheel drive vehicle in which a viscous coupling is provided as a differential limiting function of a center differential, there is a possibility that the differential limiting function of the viscous coupling and the control function of the brake control system may interfere with each other. In other words, while the former function requires torque transmission between the front wheel drive system and the rear wheel drive system, the latter function requires torque transmission between the redrive systems, especially from the front wheel drive system to the rear wheel drive system. There is no need for torque transmission to take place.

[Means for solving problems]

A transfer structure for a four-wheel drive vehicle according to the present invention is a four-wheel drive vehicle in which driving force from an engine is distributed between a front wheel drive system and a rear wheel drive system by a center differential to drive the front and rear wheels. Between the front wheel output member that outputs the driving force to the front wheel output member and the rear wheel output member that outputs the driving force to the rear wheel drive system, preferably a one-way that transmits the driving force only from the rear wheel output member to the front wheel output member. It is equipped with a clutch.

[Effect]

In the transfer structure for a four-wheel drive vehicle according to the present invention, a one-way clutch is preferably provided that transmits the driving force from the engine from the rear wheel output member of the center differential to the front wheel output member, so that the rear wheel drive When the system rotates faster than the front wheel drive system, the one-way clutch transmits the driving force that is transmitted at a high distribution rate to the fast-rotating rear wheel output member for differential operation of the center differential. Since it is transmitted to the front wheel output member by the action, the driving force from the engine is prevented from being concentrated on the rear wheel drive system, and is also transmitted to the front wheel drive system. That is, the differential operation of the center differential is regulated, and appropriate driving force is transmitted to the front and rear wheels.

On the other hand, when the rotation of the front wheel drive system precedes the rotation of the rear wheel drive system, the one-way clutch idles, and the driving force is not transmitted from the front wheel output member to the rear wheel output member, and the center differential is used for differential operation. is allowed.

Therefore, if the rear wheels slip while driving, the differential operation of the center differential is regulated by the action of the one-way clutch. Appropriate driving force is transmitted to the vehicle, which prevents the rear wheels from slipping on locally frozen roads and making it impossible to drive. Also, during normal driving,
Particularly during braking, the ground contact load is low and the slippage of the rear wheels, which are prone to slip, can be suppressed to improve running performance.

In addition, when the rotation of the front wheel drive system precedes the rotation of the rear wheel drive system during driving such as when turning or during normal driving,
Smooth driving is possible by allowing the center differential's original differential operation.

〔Effect of the invention〕

According to the transfer structure for a four-wheel drive vehicle according to the present invention,
As explained above, by providing a one-way clutch that is smaller than a viscous compression ring and can transmit a sufficiently large driving force with a simple mechanism,
For example, it is possible to suppress the slipping of the rear wheel, which has a low ground load and a relatively high possibility of slipping, and transmit appropriate driving force to the other wheel, the front and rear wheels.
The running performance of a four-wheel drive vehicle during practical driving can be sufficiently improved without using an expensive viscous coupling, and the configuration of the front and rear wheel drive force transmission system of the transfer system can be made more compact.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an overall schematic configuration of a four-wheel drive vehicle according to an embodiment of the present invention. An engine 2 is disposed at the front of a vehicle body 1, and a crankshaft 2a of the engine 2 extends in the vehicle width direction. It is mounted horizontally, slightly to the right.

A manual transmission 3 is disposed on the left side of the engine 2, and the transmission 3 is mounted horizontally so that an input shaft 6 and an output shaft 7 arranged in parallel inside a casing 4 extend in the vehicle width direction. The input shaft 6 is connected to and disconnected from the crankshaft 2a via the clutch device 5, and the gear transmission path between the input shaft 6 and the output shaft 7 arranged parallel to the input shaft 6 is switched to change the gear ratio. It is now possible to

At the rear of the portion of the transmission 3 near the center of the vehicle width, a front axle shaft 8 divided into left and right parts and a transfer output shaft 9 arranged in parallel behind the front axle shaft 8 are provided as inputs to the transmission 3, respectively. The left and right front axle shafts 8 are arranged parallel to the shaft 6 and the output shaft 7, and each of the left and right front axle shafts 8 has a constant velocity joint 1.
0 and the left and right front wheels 12 via a drive shaft 11.

The right end of the transfer output shaft 9 is connected to a propeller shaft 1 that extends in the longitudinal direction of the vehicle body via a bevel gear mechanism 14.
A rear differential mechanism 17 is connected to the front end of the propeller shaft 15 via a universal joint 15a, and the rear end of the propeller shaft 15 is on a rear axle shaft 16 that is divided into left and right parts.
is connected to via a constant velocity joint 15b.

The rear differential mechanism 17 is connected to the propeller shaft 1
5 via a bevel gear mechanism 18, a pair of pinions 20 supported by the differential gear case 19, and left and right gears meshing with the pinions 20 and fixed to the inner ends of the left and right rear axle shafts 16 The outer end of each of the left and right rear axle shafts 16 is connected to each of the left and right rear wheels 24 via a constant velocity joint 22 and each of the left and right drive shafts 23.

On the left and right front axle shafts 8, as shown in enlarged detail in FIG. ) are externally fitted, and the differential case 26 is integrally formed with a hollow spherical main body part 26a and cylindrical sleeve parts 26b on the left and right sides of the main body part 26a, and the main body part 2
Inside 6a, there is a pair of side gears 27 connected to each of the left and right front axle shafts 8, and a pinion shaft 2 meshing with the side gears 27 and disposed at right angles to the front axle shaft 8.
A pair of pinion gears 28 rotatably supported by the main body portion 26a via 8a are fitted.

Furthermore, a center differential mechanism 29 that distributes driving force to the front and rear wheels 12 and 24 is mounted on the left sleeve portion 26b of the differential case 26.

The center differential mechanism 29 includes a sun gear 30 and a ring gear 31.
It is constituted by a double-binion type planetary gear mechanism in which the two binions are meshed and connected via two systems of binions (an outer binion 33 and an inner binion 34) carried by a binion carrier 32.

The ring gear 31 is a main body portion 26a of the differential case 26.
input gear part 3 of sun gear 30.
0a, an input gear portion 31a that meshes with the gear 7a of the output gear on the output shaft 7 of the transmission 3 is formed on the outer peripheral surface of the ring gear member 31A.
is rotatably supported by the differential case 26 via bearings.

The above-mentioned nion carrier 32 is coupled to the differential case 26 of the front differential 25 so as to rotate integrally with it, and the sun gear 30 is mounted on the left front axle shaft 8.
A transfer gear 35 (rear wheel output member) is integrally formed on the left side of the transfer output shaft 9 and transmits driving force to the rear wheel 24. The transfer gear 35 is rotatably provided on the left end of the transfer output shaft 9. The transmission gear 36 is meshed with the transmission gear 36.

Further, a sprag type one-way clutch mechanism 37 is provided on the front axle shaft 8 on the left side of the transfer gear 35. This one-way clutch mechanism 3
Reference numeral 7 refers to a conventionally known sprag 37c which is constructed by equally disposing a predetermined number of sprags 37c between an outer race 37a and an inner race 37b with a holder 37d via an annular spring 37e. The inner race 37b corresponds to the outer race 37a on the sleeve portion 26b of the differential case 26. A stopper part 37f is formed at the left end of the inner race 37b to prevent the sprag 37c, the holder 37d, and the spring 37e from coming off.

The one-way clutch mechanism 37 is configured to transmit the driving force of the outer race 37a to the inner race 37b when the outer race 37a rotates faster than the inner race 37b.
7c is installed.

That is, rotation of the center of curvature of the inner and outer surfaces of the sprag 37c by degrees toward the outer race 37a causes the rotation of the center of curvature of the inner and outer surfaces of the sprag 37c.
The setting is such that when the rotation becomes faster than the rotation on the b side, a wedge effect occurs and the one-way clutch mechanism 37 becomes in a locked state (driving force transmission state). Therefore, in the front and rear wheels 12 and 24, when the front wheel 12 rotates faster than the rear wheel 24 while driving, the one-way clutch mechanism 37 is in the free state H (idling state where no driving force is transmitted).
The driving force from the differential case 26, that is, the driving force toward the front wheels 12, is not transmitted to the transfer gear 35, that is, the rear wheels 24, and the rear wheels 24 rotate faster than the front wheels 12 (rear wheel slip state). Then, the one-way clutch mechanism 37 is in a locked state (driving force transmission state), and the driving force from the transfer gear 35, that is, the driving force toward the rear wheels 24, is transmitted to the differential case 26, that is, the front wheels 12.

Therefore, in the four-wheel drive vehicle of this embodiment, when the one-way clutch mechanism 37 causes relative rotation between the front and rear wheels 12 and 24 and the rear wheel 24 slips, the differential case 26 of the front differential 25 and the transfer The transfer structure is such that the relative rotation with the gear 35, that is, the relative rotation of the front and rear wheels 12 and 24 is restricted.

A sleeve 40 that slides left and right is provided on the right sleeve portion 26b of the differential case 26 of the front differential 25, and the sleeve 40 is mechanically moved to the right position in the figure (center differential lock) via a fork (not shown) or the like. position)
By moving the ring gear member 3 of the center differential mechanism 29, which extends above the right front axle shaft 8,
1A and the differential case 26 of the front differential 25 to stop the operation of the center differential mechanism 29. A center defroster mechanism 41 is provided which rotationally connects the differential case 26 of the front differential 25 to stop the operation of the center differential mechanism 29. By switching the sleeve 40 to the lock position and operating it, the front and rear wheels 12. 24 direct connection four-wheel drive mode is available.

The transfer output shaft 9 is a solid left shaft 9a.
and a hollow cylindrical right shaft 9b, and the divided part has a two-wheel drive state in which the driving force of the engine 2 is transmitted only to the front wheels 12 by intermittent connection of both the divided shafts 9a and 9b. A 2/4 drive switching mechanism 1 that operates to switch between a four-wheel drive state transmitted to the front and rear wheels 12 and 24 via a fork, etc. not shown.
3 is provided.

Furthermore, the front differential 25 is connected to the clutch housing 42.
The front axle shaft 8 is disposed in an interior formed to protrude toward the right front axle shaft 8 side.

Furthermore, in order to properly operate the one-way clutch mechanism 37 under the intended running conditions, the total reduction ratio on the front wheels 12 side is set to be slightly higher than the total reduction ratio on the rear wheels 24 side. That is, by setting the rotation speed of the front wheels 12 slightly higher than the rotation speed of the rear wheels 24,
- During normal driving with almost no difference in rotation between the front and rear wheels 12 and 24, the one-way clutch mechanism 37 is locked due to the positive relative rotation speed of the rear wheel 24 with respect to the front wheel 2, which is caused by the difference in air pressure between the front and rear wheels 12 and 24. This is to prevent this from deteriorating the driving feeling. Note that during normal driving, the rotation speed of the front wheels 12 is generally slightly higher than the rotation speed of the rear wheels 24.

Next, the operation of the four-wheel drive vehicle having the transfer mechanism configured as described above will be explained.

The output of the engine 2 is determined by the gear section 7a of the output gear of the transmission 3.
Center differential mechanism 2 on the front axle shaft 8 meshing with the
The signal is transmitted to the ring gear 31 of No. 9, and distributed to the front wheel 12 side and the rear wheel 24 side in the center differential mechanism 29. That is, the output to the front wheel 12 side is transmitted from the front axle shaft 8 to the drive shaft 11 via the pinion carrier 32 constituting the center differential mechanism 29, the differential case 26 of the front differential 25, the pinion gear 28, and the side gear 27, and is transmitted to the front wheel 12. communicated.

On the other hand, the output to the rear wheel 24 side is transmitted from the sun gear 30 of the center differential mechanism 29 to the transfer gear 35, the transmission gear 36,
Transfer output shaft 9 is transmitted to rear wheels 24 via bevel gear mechanism 14, propeller shaft 15, rear differential mechanism 17, rear axle shaft 16, and drive shaft 23.

When the driver selects and operates the 2/4 drive switching mechanism 13 to the two-wheel drive side, both the left and right shafts 9a and 9b of the transfer output shaft 9 are disconnected, and the engine output is directed to the rear wheels 24. is not transmitted to the bevel gear mechanism 14, and the front wheel 1
The vehicle enters a two-wheel drive state with wheel 2 as the driving wheel.

In addition, when the 2/4 drive switching mechanism 13 is selectively operated to the 4-wheel drive side, that is, when driving in the 4-wheel drive state,
If only one of the front and rear wheels 12 or 24 gets stuck due to a locally frozen road surface or a traffic jam, the engine output may be concentrated on that spinning wheel and the vehicle may become unable to drive. The vehicle can be driven by operating the center differential lock mechanism 41 into a locked state.

In other words, when the center differential lock mechanism 41 is locked, the pinions 33 and 34 become unable to rotate, and the ring gear 3
1 rotation is directly connected by the pinion carrier 32 and sun gear 30, resulting in a four-wheel drive state in which the front and rear wheels 12 and 24 are directly connected, and the engine output is distributed to wheels other than the wheels that are idling.

Since the functions of the four-wheel drive vehicle described above are conventionally known, a detailed explanation will be omitted, and the functions according to the present invention will be described below.

In general, in two-wheel drive and four-wheel drive states, the rotational speed of the front and rear wheels 12 and 24 is constantly slightly rotating relative to each other due to drive slips due to road surface conditions, not only when turning but also when driving straight. In the driving range of
The rotation speed of the rear wheel 24 is reasonably higher than that of the rear wheel 24.

Therefore, the one-way clutch mechanism 37 is connected to the front and rear wheels 12.
・If the rotation speed of the rear wheel 24 increases between 24 and 24, especially if the rear wheel 24 slips and loses traction, the transfer gear 35 connected to the rear wheel 24 and the front wheel 1
Differential case 26 of front differential 25 connected to 2
Even if the two wheels try to rotate relative to each other, the sprag 37c of the one-way clutch mechanism 37, which is interposed between the transfer gear 35 and the differential case 26, becomes locked, restricting the relative rotation, and preventing the front and rear wheels 12 and 24 from rotating properly. Since the driving force is transmitted, the front wheels 12 immediately pull the wheel to improve running performance. However, during normal driving and when turning, where the rotation speed of the front wheels 12 is slightly higher than the rotation speed of the rear wheels 24, the above-mentioned The one-way clutch mechanism 37 is in a free state, allowing relative rotation between the transfer gear 35 and the differential case 26, that is, differential operation of the center differential mechanism 29, without impairing the function of the center differential mechanism 29. It goes without saying that in rare situations where the front wheels 12 lose traction on a locally frozen road or the like and the vehicle becomes unable to travel, the center differential lock mechanism 41 allows the vehicle to travel.

In other words, in the transfer structure of the four-wheel drive vehicle of this embodiment, in a general four-wheel drive vehicle in which the power plant such as the engine 2 and transmission 3 is disposed at the front of the vehicle body l, the transfer structure is simple. By regulating the relative rotation of the center differential mechanism 29 when the rear wheel 24, which has a low ground load and is prone to slip, is idling using the one-way clutch mechanism 37, which has a small structure and low cost, the running performance can be sufficiently improved in most normal driving ranges. Therefore, there is no practical problem even if a viscous coupling mechanism with a complicated structure and high cost is not provided.

Furthermore, if we increase the viscous torque (viscous transmission torque) performance of the conventional viscous coupling mechanism in order to further improve the driving performance when driving in four-wheel drive, not only will the performance of the anti-skid brake not be achieved, but it will also be difficult to turn. One-way clutch mechanism 37 has the disadvantage that it sometimes tends to understeer, making it difficult to combine viscous coupling and anti-skid brake.
In this case, since the driving force is distributed to the front wheels 12 with a large braking force distribution, the braking performance is not greatly affected, and it is possible to achieve both anti-skin braking.

On the front axle shaft 8, a center differential mechanism 29 is disposed on the side of the front differential 25, and a transfer gear 35 is disposed on the opposite side of the center differential mechanism 29 from the front differential 25. 35, the one-way clutch mechanism 37 is disposed on the opposite side of the center differential mechanism 29, and the one-way clutch mechanism 37 is disposed on the side of the transfer gear 35, which has a large diameter and requires a relatively large installation space. Therefore, there is no need to take up a large space for arranging the one-way clutch mechanism 37, and it is possible to have a compact configuration.

Also, the one-way clutch mechanism 37 is connected to the front differential 25.
Interference with the clutch housing 42 that would otherwise occur if the front axle shaft 8 is disposed on the opposite side of the center differential mechanism 29 is also avoided, and the front axle shaft 8 can be disposed as close as possible to the transmission 3.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic plan view showing the overall configuration of a power transmission system of a four-wheel drive vehicle, and FIG. 2 is an enlarged sectional view of the main parts. l...Vehicle body, 2...Engine, 3...Transmission, 25
...Front differential, 26.. Differential case (output member for front wheels), 29.. Center differential mechanism, 31.. Ring gear, 35.. Transfer gear (output member for rear wheels).
37...One-way clutch mechanism.

Claims (2)

[Claims] (1) In a four-wheel drive vehicle in which the driving force from the engine is distributed between the front wheel drive system and the rear wheel drive system by a center differential to drive the front and rear wheels, the front wheel output member outputs the driving force to the front wheel drive system in the center differential. A transfer structure for a four-wheel drive vehicle, characterized in that a one-way clutch is interposed between the rear wheel output member and the rear wheel output member that outputs driving force to the rear wheel drive system. (2) The transfer structure for a four-wheel drive vehicle according to claim 1, wherein the one-way clutch is configured to transmit driving force only from the rear wheel output member to the front wheel output member.