JPS63240426A - Four-wheel-drive vehicle - Google Patents

Abstract

PURPOSE:To avoid a tight corner braking phenomenon by transmitting power to one of the front and rear wheels of an FF four wheel drive vehicle via a one-way clutch and controlling a transfer gear ratio being related to the tire slip ratio at the time of tight cornering. CONSTITUTION:In an FF four-wheel-drive vehicle, the power of an engine 1 is directly transmitted to front wheels 5 via a clutch and a transmission 2, a front wheel differential gear 3, and front wheel axles 4. The front wheel differential gear 3 is also power transmittingly connected to two sets of one way clutches 11, 12 via the pairs of gears 7 and 8 of a transfer device 6 and a direction changing gear 10, to transmit the rotation of a propeller shaft 13 to rear wheels 16 via a rear wheel differential gear 14 and rear wheel axles 15. The gear ratios of the pairs of gears 7 and 8 are set above '1', '1 + S' ( S = a slip ratio at the time of tight cornering) respectively, and each of the pairs of gears 7, 8 are switched over go as to use the pair of gears 7 at the time of direct-connected four wheel driving by means of a sleeve 9 while using the pair of gears 8 at the time of normal traveling.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a four-wheel drive vehicle in which a one-way clutch is provided in a transfer device provided in the middle of a transmission system for front and rear wheels.

(Prior Art) A four-wheel drive vehicle using a one-way clutch proposed in Japanese Patent Application Laid-Open No. 60-15226 will be explained with reference to FIG. 2. This is based on the two-wheel drive of an RR. 20 is a drive device having an engine, a clutch, and a transmission, and this is a rear wheel differential device 21 and a rear wheel axle 22.
The power is directly transmitted to the rear wheels 23 via. Further, the rear wheel differential device 21 is connected to two of the transfer devices 24.
．． It is connected to two sets of one-way clutches 27 and 28 via a four-wheel switching clutch 25 and a direction change gear 26, and is further transmitted to the front wheels 32 via a propeller shaft 29, a front wheel differential device 30, and a front wheel axle 31. It has become.

(Problems to be Solved by the Invention) The drive of the conventional four-wheel drive vehicle is based on rear engine rear wheel drive (RR), and when this is installed in a front engine front wheel drive vehicle (FF). When the front wheels turn faster than the rear wheels, a four-wheel drive configuration is established. However, in this case, the front wheels turn faster than the rear wheels during tight corners, resulting in four-wheel drive. In other words, conventional four-wheel drive vehicles have a problem in that tight corner braking cannot be avoided.

[Structure of the invention]

(Means for Solving the Problems) Therefore, the present invention is a front-wheel drive four-wheel drive vehicle, in which power is directly transmitted to one of the front and rear wheels, and power is transmitted to the other through a one-way clutch for forward and reverse travel. In addition to making it conductive, the transfer gear ratio is related to the tire slip rate ΔS at tight corners, and it is equivalent to "1 + ΔS" or "
1+ΔS'' or more, and this is used as a means to solve the problem.

(Function) When moving forward or straight, the forward clutch is selected as the one-way clutch, and the front shaft of the one-way clutch rotates slowly relative to the propeller shaft, and the one-way clutch becomes idle, resulting in two-wheel drive. However, when the front wheels slip beyond a certain level, the one-way clutch becomes locked and torque is transmitted to the propeller shaft, resulting in four-wheel drive.

Also, during tight corners, the front wheels rotate faster than the rear wheels, but due to the gear ratio, the front axle does not rotate faster than the propeller shaft. When going backwards, the one-way clutch for reverse is selected, and the transmission configuration is the same as when going forward.Also, when driving on low μ roads such as snowy roads, direct 4-wheel drive is used, so the one-way clutch locks forward and reverse at the same time. It is established by this.

(Example) The present invention will be explained below with reference to the embodiments shown in the drawings. Fig. 1 shows the transmission system of a four-wheel drive vehicle in an embodiment of the present invention, which is based on a front engine and front wheel drive. . In the figure, 1 is an engine, 2 is a clutch and a transmission, and these directly drive front wheels 5 via a front wheel differential 3 and a front wheel axle 4.

Further, the front wheel differential 3 is transmitted to two sets of one-way clutches 11 and 12 via the gear pair 7 or 8 of the transfer device 6 and the direction change gear 10, and furthermore, the propeller % 113, the rear wheel differential 14, and the rear wheel axle 15. The rear wheels 16 are electrically driven through the transmission.

Further, the gear ratio of gear pairs 7 and 8 is "1" for gear pair 7.
”, gear pair 8 is equivalent to “l+ΔS” or “1+ΔS”
S” or higher. Note that ΔS is a slip rate at a tight corner.

The gear pair 7.8 is used in the case of direct four-wheel drive, and the gear 8 is used during normal driving, and the switching is performed by the sleeve 9.

Now, when the vehicle is running forward or straight, the forward clutch 11 is selected as the one-way clutch, and the propeller shaft 13 is selected as the one-way clutch.
On the other hand, the front shafts 17 of the one-way clutches 11 and 12 are rotating slowly, and the one-way clutch 11 is idle, resulting in two-wheel drive. However, when the front wheel 5 slips and rotates beyond a predetermined level, the one-way clutch 11 becomes locked and torque is transmitted to the propeller shaft 13, resulting in four-wheel drive.

Further, during a tight corner, the front wheels 5 rotate faster than the rear wheels 16, but the front shaft 17 does not rotate faster than the propeller shaft 13 due to the gear ratio of the gear pair 8. On the other hand, when traveling backward, the one-way clutch 12 for reverse is selected, and the transmission configuration is the same as when traveling forward. In addition, for driving on low μ roads such as snowy roads, the transfer gear ratio is set to ``1'' to provide direct four-wheel drive, so the gear pair is 7 and the one-way clutch locks forward and reverse simultaneously.

〔Effect of the invention〕

As explained in detail above, the present invention relates the transfer gear ratio to the tire slip rate ΔS, so that
If the gear ratio is within 1+ΔS, which causes braking phenomenon during tight corners, i.e., the gear ratio where the front wheels rotate faster than the rear wheels, the one-uni-f clutch will idle, resulting in two-wheel drive, and the rotation ratio will change on low μ roads, etc. 1+ΔS'' or more, the vehicle becomes four-wheel drive, so the drawbacks of the conventional system can be avoided. Also, if the front wheels slip in a tight corner on a low μ road, the vehicle will switch to four-wheel drive, so it is not necessarily necessary to use direct-coupled four-wheel drive, but of course there is no problem with direct-coupling four-wheel drive. This is because the four-wheel drive state can be achieved even if the degree of slip is less than in the past.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a transmission system of a four-wheel drive vehicle showing an embodiment of the present invention, and FIG. 2 is a plan view of a transmission system of an example of a conventional four-wheel drive vehicle. Explanation of main parts of the diagram 1... Engine 2 - Clutch and transmission 3 - Front wheel differential 5 - Front wheels 6 - Transfer device 7.8 - Gear pair 10 - One-way conversion gear 11.12 ---One-way clutch 13--Propeller shaft 14--Rear wheel differential 16-Rear wheel 17-Front shaft LI α)

Claims (1)

[Claims] It is a front-wheel drive four-wheel drive vehicle, with power being transmitted directly to one of the front and rear wheels, and power being transmitted to the other through a one-way clutch for forward and reverse travel, and the transfer gear ratio is adjusted to reduce tire slip during tight corners. A four-wheel drive vehicle characterized in that the rate ΔS is equal to or greater than "1+ΔS".