JPH02155841A - Transmission of four-wheel drive car - Google Patents

Abstract

PURPOSE:To have stable running by arranging a torque transmitting amount adjusting means on a crank mechanism, and by giving the front dif. ratio a value a little larger or smaller than the rear dif. ratio. CONSTITUTION:The front dif. ratio consisting of gear ratio of a counter gear of an automatic transmission mechanism to a ring gear 11 is set a little larger than the rear dif. ratio consisting of the gear ratio of a rear wheel differential device, and thereby the torque from an engine is distributed in priority to the one with larger dif. torque, i.e. to the front axle side with slower rotation. When the operator operates a means to vary the degree of engagement of a clutch mechanism 35 to control the oil pressure supplied to an oil chamber 38, pistons 39a, 39b are slided and the degree of detainment of the front dif. case 13 with front dif. carrier 15 is adjusted. The torque transmitted fron engine via the ring gear 11 is transmitted via the mechanism 35, and the clutched portion is transmitted in priority to a differential device B for front wheels, with the rest distributed to the front and rear wheels by a central differential device A in accordance with the planetary gearing ratio.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a power transmission device for a four-wheel drive vehicle, which is equipped with a torque distribution control device that can vary the amount of torque distribution to front and rear wheels. The present invention relates to a power transmission device for a four-wheel drive vehicle.

(Conventional technology) Conventionally, front-wheel drive cars generally have better stability than rear-wheel drive cars when driving in a straight line, but when cornering, it is necessary to apply force to the steering wheel to keep the tires moving back. Because of this, front-wheel drive vehicles tend to be more difficult to turn. On the other hand, in the case of rear-wheel drive, cornering performance is good, but there is a drawback that if the driving force is too strong, the vehicle will turn too much.

Therefore, it is ideal for an automobile to drive the front wheels and the rear wheels with approximately 50/50 power, and in this respect, four-wheel drive cars can be said to be extremely superior.

In a conventional power transmission device for a four-wheel drive vehicle, the driving force of the engine is first transmitted to a central differential device, and then transmitted to left and right side gears by the differential device.

The driving force transmitted to one side gear is further transmitted to the front width differential, where it is again distributed to the left and right side gears and transmitted to both front axles. Further, the driving force transmitted to the other side gear is transmitted to the rear wheel differential device via the rear wheel drive propeller shaft, where it is again distributed to the left and right side gears and transmitted to both rear axles.

In the above-mentioned conventional four-wheel drive vehicle, when making a sharp turn at low speed on a road surface with a high coefficient of friction, a so-called tight corner braking phenomenon occurs in which the vehicle is braked due to the difference in rotation between the front and rear wheels. Therefore, to prevent this,
The above-mentioned central differential device is required, but because the central differential device is installed, conversely, if any one wheel of a four-wheel drive vehicle becomes unloaded, the central differential device will become differential. Drive energy escapes there, making it impossible to transmit torque.

Therefore, a differential limiting mechanism is provided to stop differential movement of the central differential at this time. The differential limiting mechanism is composed of a wet multi-plate friction material clutch and a hydraulic actuator.

During normal driving, the hydraulic two-wheel clutch is disengaged to maintain the central differential in the operating state, and the front one
- The driving force is branched and transmitted to each of the axle and rear axle, but the clutch is engaged when the tires slip or there is a risk of slipping on a snowy or frozen road.

By the way, the slip-knob limit characteristics of a tire are determined by the load acting perpendicularly to the tire's contact surface, and this load changes mainly due to the N amount distribution G of the vehicle.However,
The conventional central differential system described above always distributes torque between the front and rear wheels at a constant ratio (for example, 50:50), so if the driving force increases, one of the front and rear wheels will be The problem is that slip occurs first, making it impossible to obtain any more driving force. That is, the driving force transmission limit number is balanced to the value of the lower driving force of the front wheels or the rear wheels. For example, when one of the front wheels spins, the driving force of the rear wheel becomes extremely small, and the driving force cannot be sufficiently transmitted to the road surface, resulting in phenomena such as front or rear wheel slipping.

Therefore, a clutch for limiting the center differential differential is installed in parallel with the center differential, and the engagement of the clutch for limiting the center differential differential is limited by an electronic control device to improve the slip limit characteristics of the tires and increase the pitching performance. , products with improved traction and driving stability on snowy roads, etc. are available.
(Refer to Japanese Patent Application Laid-Open No. 61176728).

(Problem B to be solved by the invention) However, in the above conventional power transmission device for a four-wheel drive vehicle, the second differential clutch for limiting differential differential is controlled by an electronic control device, and the transmission is transmitted to the front and rear wheels according to the driving condition. However, it is not possible to actively control the distribution ratio of driving force between the front and rear wheels.

The present invention solves the problems of the conventional power transmission system for four-wheel drive vehicles, and is capable of distributing driving force to four wheels depending on, for example, road surface conditions or driving patterns. The purpose is to provide power transmission devices for drive vehicles.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention aims to solve the problems described above.
8), has a carrier (29) and a ring gear (30), the output of the engine is manually transmitted to the carrier (29), and the center gear (28) or ring gear (30) is connected to either the front or rear wheels. Differential device (A), the central differential device (A)
A clutch mechanism (35) provided between any two of the above-mentioned respective elements of In a four-wheel drive vehicle having a differential device, the clutch mechanism (35) is provided with a l-lux transmission product tN node means, and the freon j-differential ratio is slightly larger or smaller than the rear differential ratio. That's how it is.

(Operations and Effects of the Invention) According to the present invention, as configured as described above, by changing the torque transmission amount of the clutch mechanism (35), various road surface conditions, driving conditions or 1- It becomes possible to arbitrarily or automatically select the driving force distribution ratio between the front and rear wheels depending on the driving pattern or the like.

Furthermore, since the front differential ratio is set to be slightly larger or smaller than the rear differential ratio, the torque distribution ratio does not change unexpectedly due to the influence of the road surface, allowing stable driving.

Note that in the above M, each element is given a reference numeral for convenience of explanation, but this does not limit the configuration of the present invention.

(Example) Hereinafter, a power transmission device for a four-wheel drive vehicle according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram of a power transmission system for a four-wheel drive vehicle according to the present invention.

In the figure, 11 is a ring gear that receives torque via a counter gear on the output side of the automatic transmission.

A front differential case 13 connected to the ring gear is rotatably supported within the transaxle case 12, and a front differential carrier 15 is further rotatably supported within the front differential case 13. The front differential carrier 15 is provided with a pinion shaft 16a that rotates a pinion 16, and left and right side gears 18a and 18b that mesh with the pinion 16 are connected to left and right front wheel drive shafts 20a and 20b, respectively.

Further, there is a transfer case 22 on the right side of the torque axle case 12, and a center differential case 25 to which a hypoid gear 23 is fixed is rotatably supported within the transfer case 22.

A drive pinion shaft 27 is engaged with the hypoid gear 23 via a gear 26, so that power is transmitted to a rear axle (not shown).

By the way, the central differential device A disposed within the center differential case 25 is composed of a sun gear 28, a carrier 29 that pivotally supports the pinion 16, and a ring gear 30.

On the other hand, on the outer periphery of the right front wheel drive shaft 20b, a first hollow shaft 31 extending from the Freon I differential carrier 15 is rotatably disposed, and on the outer periphery of the first hollow shaft 31, a front differential case 13 is provided. A second hollow shaft 32 extending from the second hollow shaft 32 and a third hollow shaft 33 spline-coupled to the second hollow shaft 32 are rotatably disposed.

The ring gear 30 has an integral structure with the center differential case 25, and includes a hypoid gear 23 for rear wheel drive.
connected to. Further, the carrier 29 is connected to a third hollow shaft 33, and the sun gear 28 is further connected to the first hollow shaft 31.

Further, a clutch mechanism 35 is disposed between the front differential case 13 and the front differential carrier 15, which adjusts the degree of engagement between the two to distribute torque to the front and rear wheels and limit the differential.
The oil pressure adjusted by the solenoid valve 36 is applied to the oil path 3.
7, the oil is supplied to the oil chamber 38, and the pistons 39a, 39
The pressing of b adjusts the degree of engagement between the front differential case 13 and the front differential carrier 15 by force.

Here, a control device for adjusting the degree of engagement of the clutch mechanism 35 is shown in FIG.

In the figure, the oil pressure of pressure oil supplied to the oil chamber 38 of the clutch mechanism 35 is adjusted by a solenoid valve 36. The opening degree of the valve of the second solenoid half 36 is adjusted by the transmission control computer 50, and the line pressure is changed into clutch pressure and supplied.

The transmission control 1 call computer 50 includes a center differential control switch 51.
Speed sensor 52, rear speed sensor 53, throttle position sensor 54, neutral start switch 55, stop lamp switch 56, pattern select switch 57, auto life switch 58,
It receives a signal from the ESC controller 59, performs calculations based on the signal, and outputs a command signal to the solenoid valve 36.

Among these, the pattern select switch 57 is used by the driver to select a driving pattern among dry mode, weno 1 mode, and snow & ice mode, as will be described later.

Next, the operation of the power transmission device for a four-wheel drive vehicle having the above configuration will be explained.

The rotation of the engine is appropriately changed in speed via an automatic transmission mechanism, and is transmitted to the front differential case 13 via a counter gear and a ring gear 11. Assuming that the clutch mechanism 35 is now in a completely open state, in this state the rotation of the front differential case 13 is limited to the second hollow shaft I.32 and the third hollow shaft.
The signal is inputted to the carrier 29 of the planetary gear type medium-fire differential device A via the hollow shaft 33. Then, one side is transmitted to the hypoid gear 23 via the ring gear 30,
Further, the signal is transmitted to the rear wheel drive shaft via the drive pinion shaft 27, and the other is transmitted to the first hollow shaft 31 and the front differential carrier 1 of the front wheel differential device B via the sun gear 28.
5, and further transmitted from the pinion 16 to the left and right side gears 18a, 18b, and then to the left and right front wheel drive shafts 20a, 20b, respectively. As a result, the torque input to the carrier 29 is distributed to the front wheels and the rear wheels according to the gear ratios of the sun gear 28 and the ring gear 30.

Conversely, when the clutch mechanism 35 is engaged, the rotation of the front differential case 13 changes depending on the degree of engagement.
5, the signal is directly transmitted to the front differential carrier 15 of the front wheel differential I3, and is further transmitted from the binion gear to the left and right side gears 18a, 18b, and then to the left and right front wheel drive shafts 20a, 20b, respectively.

At the same time, the rotation of the front differential case 13 is transmitted to the carrier 29 and non-gear 28 of the planetary gear type central differential A through hollow shafts 32 and 31, respectively, and is transmitted through the hollow shaft 31 to the differential for the front wheels. moving device B
can be conveyed to. Further, the signal is transmitted to the hypoid gear 23 and the drive pinion shaft 27 via the ring gear 30, thereby rotating the rear wheel drive shaft. This makes it possible to limit the differential motion between the front wheels and the rear wheels and change the torque distribution ratio depending on the degree of engagement of the clutch mechanism 35.

Here, in the power transmission device for a four-wheel drive vehicle having the above configuration, the front differential ratio consisting of the gear ratio of the counter gear of the automatic transmission mechanism and the ring gear 11 is different from the rear differential ratio consisting of the gear ratio of the rear wheel differential. It is set slightly larger. By doing so, torque from the engine is preferentially transmitted to the side with a larger differential ratio, that is, the front axle side that rotates slower.

That is, from the engine to the counter gear and ring gear 11
The torque transmitted via the clutch mechanism 35 is transmitted through the clutch mechanism 35, and the clutch engagement portion is preferentially transmitted to the front wheel differential B, and the remaining torque is transmitted by the central differential A to the planetary gear ratio. It is distributed to the front and rear wheels according to the Therefore, the torque distribution will not change or become unstable due to the influence of the road surface, etc.

A means that can be manually operated by the driver to change the degree of engagement of the clutch mechanism 35 is provided in the driver's cab, and by using the means,
By controlling the oil pressure supplied to the oil chamber 38,
The degree of engagement between the front differential case 13 and the front differential carrier 15 is adjusted by sliding the pistons 39a and 39b.

Moreover, the central differential device A is formed by a planetary gear, and the torque input to the carrier 29 is transferred to the sun gear 2.
8 to the front wheels and to the rear wheels via the ring gear 30, the torque distribution between the front and rear wheels is 30:70 when the clutch mechanism 35 is not engaged, and when it is fully engaged. The ratio can be set to 70:30. Therefore, by completely engaging the clutch mechanism when the vehicle is in the starting position, it becomes possible to improve the drive performance.

Fig. 3 is a diagram showing the torque distribution according to the road surface pattern.
Figure (b) shows the state in wet mode, and Figure 3 (C
) indicates the status during snow & ice mote.

In the figure, in dry mode when the road surface is dry, the torque distribution between the front and rear wheels is 34:66.

Next, when the road surface is wet, the driver selects the wet mode and sets the clutch capacity NT to 'rc = 0.246 TE (T,: engine torque), which changes the torque distribution between the front and rear wheels. 50:5
It is set to 0. At this point, the road surface conditions differ between the front and rear wheels, causing the tires to reach their slip limit and reducing the rear wheel grip to zero.
% or 20%, or the front wheel grip force may be 0% or 20%, but it also shows the torque distribution ratio between the front and rear wheels under these conditions.

In addition, when the road surface is snowy or frozen, the driver selects the snow & ice mode to set the clutch capacity NTc to T, = 0.508 TE, which improves the torque distribution between the front and rear wheels. is 67:3
It is considered to be 3.

Next, FIG. 4 shows a state diagram of torque distribution between the front and rear wheels. The joint shaft shows the ratio of torque distribution to the front wheels, and the horizontal axis shows the ratio of torque distribution to the rear wheels.

In the figure, point a is the state in the dry mode of FIG. 3(a), point b is the state in the wet mode of FIG. 3(b), and 0.
The dots indicate the state in the snow & ice mode in FIG. 3(C). Further, point d indicates a state of an FF vehicle in which all torque is distributed to the front wheels, and point 8 indicates a state of an FR vehicle in which all torque is distributed to the rear wheels.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a power transmission system for a four-wheel drive vehicle according to the present invention, Fig. 2 is a diagram showing a control device for a clutch mechanism of the power transmission system for a four-wheel drive vehicle according to the present invention, and Fig. 3 is a diagram showing a control device for a clutch mechanism of a power transmission system for a four-wheel drive vehicle according to the present invention. Fig. 3(a) is a state diagram in dry mode, Fig. 3(b) is a state diagram in wet mode, and Fig. 3(a) is a state diagram in wet mode.
C) shows a state diagram during snow and ice mode, and FIG. 4 shows a state diagram of torque distribution between the front and rear wheels. 28...Sangia, 29...Career, 30...
Ring gear, 35... Clutch mechanism, A... Central differential device, B... Front wheel differential device.

Claims (1)

[Claims] A central differential device that has a sun gear, a carrier, and a ring gear, inputs the output of the engine to the carrier, and connects the sun gear or ring gear to either the front or rear wheels; any of the above elements of the central differential device; In a four-wheel drive vehicle having a clutch mechanism provided between the two, a front wheel differential device and a rear wheel differential device that further distributes the torque distributed by the central differential device, the torque of the clutch mechanism is A power source for a four-wheel drive vehicle characterized by having a transmission amount adjusting means and by setting a front differential ratio slightly larger or smaller than a rear differential ratio, the torque distribution ratio to the front and rear wheels can be freely selected. transmission device.