JPH04300730A - Driving force distribution device for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To simplify the construction, miniaturize the device, and reduce the weight by providing two set of differential gears on a driving force transmitting route, providing respective differential gears on prescribed positions concerning to three wheels, and additionally providing a differential limiting mechanism to limit differential movement of front wheels and rear wheels. CONSTITUTION:Two set of planetary gear mechanisms 30, 40 and an input gear 18 are provided side by side in series around front wheel drive shafts 10a, 10b, and a one body type differential 14 is constituted out of them 30, 40, 18. Driving force transmitted from the input gear 18 to the carrier 32 of the planetary gear mechanism 30 is distributed to a ring gear 36 and a sun gear 38 through a planet gears 34, the driving force distributed to the sun gear 38 is transmitted to the left front wheel drive shaft 10a. Meanwhile, the driving force distributed to the ring gear 36 is transmitted to the carrier 42 of the planetary gear mechanism 40, and transmitted to a ring gear 46 and a sun gear 48. The driving force transmitted to the sun gear 48 is transmitted to the right front wheel drive shaft 10b, and the driving force transmitted to the ring gear 46 is transmitted to rear wheel drive shafts 27a, 27b.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides a drive force distribution for a four-wheel drive vehicle in which a differential is provided with a differential limiting mechanism capable of regulating the drive force distribution between the front and rear wheels by limiting the differential of the differential. Regarding equipment.

0002

2. Description of the Related Art Generally, in a four-wheel drive vehicle, the driving force from the engine is shifted by a transmission and then transmitted to a center differential (hereinafter referred to as center differential), where it is distributed between the front wheels and the rear wheels. The signal is transmitted to the front differential (front differential) and rear differential (rear differential).

For example, FIG. 4 is a schematic diagram showing the configuration of a conventional driving force distribution device for a four-wheel drive vehicle, in which (a) is a plan sectional view and (b) is a side view configuration diagram. In this four-wheel drive vehicle driving force distribution system, the engine 2A is placed on the right when facing the front of the vehicle, the transmission 6A is placed on the left (hereinafter, this type is referred to as the E-W type), and the center differential 52
is arranged behind these 2A and 6A.

[0004]The driving force from the engine 2A is transmitted to a transmission (in this case, an automatic transmission) 6 via a torque converter 3A.
A, the speed is changed, and the transmission is transmitted from the main shaft 4A to the intermediate shaft 8A via gear mechanisms 51a and 51b, and further to each shaft on the front wheel drive shaft axis 10A via gear mechanisms 51c and 51d. It is meant to be transmitted.

That is, the driving force from the engine 2A is transmitted from a gear mechanism 51 to a center differential 52 constituted by a planetary gear mechanism, and in this center differential 52, the driving force is input to a ring gear 52a and then to a planetary gear 52c.
, 52d to the rear wheel shaft 53a, and the front wheel shaft 53b through the sun gear 53e, which is rotationally driven through the planetary gears 52c, 52d. 53b to a front differential 54, and from the rear wheel side shaft 53a to a rear differential (not shown) via a bevel gear 55 and a propeller shaft 56.

In this E-W type four-wheel drive vehicle driving force distribution device, the rear wheel shaft 53a and the front wheel shaft 53b
is arranged coaxially on the axis 10A of the front wheel drive shaft, and the shaft system near the engine from the engine to the front wheel drive shaft includes the main shaft 4A, intermediate shaft 8A, and front wheel drive shaft system (10
It consists of three axes: A).

FIG. 5 is a schematic diagram showing the configuration of another conventional driving force distribution device for a four-wheel drive vehicle, in which (a) is a plan cross-sectional view, and (b) is a side view configuration diagram. As shown in the figure, toward the front of the vehicle, the engine 2B is on the left, and the transmission 6 is on the right.
B are arranged respectively (hereinafter, this type is referred to as W-E type), and the center differential 62 is arranged behind these 2B and 6B.

[0008]The driving force from the engine 2B is then transmitted to a transmission (in this case, an automatic transmission) 6 via a torque converter 3A.
B, the speed is changed, and it is transmitted from the main shaft 4B to the intermediate shaft 8B via the gear mechanisms 61a and 61b, and further transmitted from the intermediate shaft 8B to the center shaft 9B via the gear mechanisms 61b and 61c. The power is transmitted to the front and rear wheel shafts.

That is, a center differential 62 is provided on the outer periphery of the center shaft 9B, and the driving force from the engine 2B is input to the center differential 62, and is transmitted from the pinion through the side gear to the front wheel shaft 63a and the rear wheel shaft (= (center shaft) 63b, and is transmitted from the front wheel shaft 63a to the front differential 64, and from the rear wheel shaft 63b via the bevel gear 65 and propeller shaft 66 to the rear differential (not shown).

In this W-E type drive force distribution device for four-wheel drive vehicles, since the rotation direction of the engine output shaft is different from that of the E-W type device, the shaft system near the engine from the engine to the front wheel drive shaft is is a center shaft system 9A and a front wheel drive shaft 10A in which one axis has been added, and a main shaft 4A, an intermediate shaft 8A, a rear wheel side shaft 53a and a front wheel side shaft 53b are arranged.
It consists of an axis.

As shown in each of these conventional examples, the conventional four
In the drive force distribution system for wheel drive vehicles, engine output is first distributed to the front wheels and rear wheels through the center differentials 52 and 62, then distributed to the left and right wheels through the front differential on the front wheel side, and then distributed to the left and right wheels through the front differential. In this case, the power is distributed to the left and right wheels through the rear differential.

0012

By the way, among the conventional driving force distribution devices for four-wheel drive vehicles as described above, the E-W type device shown in FIG. 4 has an efficient structure in the case of 2WD. However, when converting to 4WD, there are many additional items such as the addition of a transfer case, and the structure becomes complicated, such as a triple structure around the front wheel drive shaft, resulting in an increase in the size and weight of the device. Problems may also occur, such as deterioration of assembly efficiency and increased costs.

Furthermore, in the W-E type device shown in FIG.
Although it is suitable for 4WD because it has an axial structure and a center differential can be installed around the center shaft, the center shaft system has a double structure, so the structure is still somewhat complicated and the above-mentioned problems cannot be solved. In addition, in the case of 2WD, there is an unnecessary shaft, which results in wasted space and cost.In addition, the rotation direction of the engine and the rotation direction of the front wheel drive shaft are opposite, which is disadvantageous in terms of vibration. Problems are also likely to occur.

The present invention was devised in view of the above-mentioned problems, and it simplifies the structure, makes the device smaller, reduces weight, improves ease of assembly, and reduces costs, and also eliminates vibration problems. It is an object of the present invention to provide a driving force distribution device for a four-wheel drive vehicle that does not cause such problems.

[0015]

[Means for Solving the Problems] In order to achieve this object, the driving force distribution device for a four-wheel drive vehicle of the present invention is configured to distribute power from an engine to four wheels, two front wheels and two rear wheels, in a four-wheel drive vehicle. A first differential gear and a second differential gear are provided in a driving force transmission path leading to the wheels,
The first differential gear is interposed between one of the four wheels and the other three wheels, and the second differential gear is interposed between one of the four wheels and the other three wheels. It is interposed between one wheel, the left and right paired wheels, and the other two wheels of the three wheels, and limits the differential between the front wheels and the rear wheels to the driving force transmission path. It is characterized by being equipped with a differential limiting mechanism.

Preferably, the first differential gear and the second differential gear are both constructed from a planetary gear mechanism, and are arranged coaxially with each other.

[0017]

[Operation] In the above-mentioned driving force distribution device for a four-wheel drive vehicle of the present invention, the first differential gear distributes the driving force between one of the four wheels and the other three wheels. Then, the second differential gear transmits a driving force between the left and right pair of the one wheel of the three wheels and the other two wheels of the three wheels. Allocate. A differential limiting mechanism attached to the driving force transmission path limits the differential between the front wheels and the rear wheels, and the above-mentioned distribution of driving force is adjusted by this differential limiting.

[0018]

[Embodiment] A driving force distribution device for a four-wheel drive vehicle as an embodiment of the present invention will be explained below with reference to the drawings.
is its schematic configuration diagram, and Figure 2 is its side view configuration diagram (Figure 1
FIG. 3 is a speed diagram showing the relationship between each gear.

As shown in FIG. 1, this driving force distribution system for four-wheel drive vehicles is of the E-W type in which the engine 2 is placed on the right and the transmission 6 is placed on the left when facing the front of the vehicle. A center differential, a front differential, and a rear differential are provided in the drive power transmission path from the output portion of the transmission 6 to the front wheels 3L, 3R and the rear wheels 5L, 5R. However, in this device, the center differential is not independent, but is integrated with the front differential (integrated differential; hereinafter referred to as an integrated differential) 14.

[0020] That is, the front wheel drive shaft (third shaft)
Around the axes 10a and 10b are two sets of planetary gear mechanisms 30,
40 and input gear 18 are arranged in series in parallel, and these planetary gear mechanisms 30, 40 and input gear 18 constitute integrated differential 14. The input gear 18 is integrally connected to the carrier 32 of the planetary gear mechanism 30, and the ring gear 36 of the planetary gear mechanism 30 is integrally connected to the carrier 32 of the planetary gear mechanism 30. Furthermore, the sun gear 38 of the planetary gear mechanism 30 is connected to the left front wheel drive shaft 10.
a, and is integrally coupled with the sun gear 48 of the planetary gear mechanism 40.
is integrally connected to the right front wheel drive shaft 10b.

Furthermore, the ring gear 46 of the planetary gear mechanism 40
An output gear 22 is integrally formed on the outer periphery of the front wheel drive shafts 10a and 10b, and this output gear 22 meshes with an input gear 24 of a shaft (fourth shaft) 12 provided adjacent to the front wheel drive shafts 10a, 10b. The shaft 12 is connected to a rear differential 26 via a bevel gear mechanism 15 and a drive shaft 17.

[0022] As a result, the driving force from the engine 2 is
After being transmitted from the output shaft (first shaft) 4 to the transmission 6 for speed change, the transmission is transmitted from the output shaft (intermediate shaft, second shaft) 8 of the transmission 6 to the integrated differential via gear mechanisms 16 and 18. 14.

That is, from the input gear 18 to the planetary gear mechanism 30
The driving force transmitted to the carrier 32 is distributed to the ring gear 36 and the sun gear 38 through the planetary gear 34, and the driving force distributed to the sun gear 38 is transmitted to the left front wheel drive shaft 10a.
The driving force distributed to the carrier 4 of the planetary gear mechanism 40
2 and is distributed to a ring gear 46 and a sun gear 48 through a planetary gear 44. The driving force distributed to the sun gear 48 is then transferred to the right front wheel drive shaft 1.
On the other hand, the driving force distributed to the ring gear 46 is transmitted to the rear wheel drive shafts 27a, 27b through the gear mechanisms 22, 24, the shaft 12, the bevel gear mechanism 15, the drive shaft 17, and the rear differential 26. It has become.

Therefore, in this driving force distribution system for a four-wheel drive vehicle, the engine output is first distributed to the left front wheel 3L side and the other three wheels (right front wheel 3R and left and right rear wheels 5L, 5R) through the planetary gear mechanism 30. ), and then, through the planetary gear mechanism 40, it is distributed between the right front wheel 3R side and the other two wheels (left and right rear wheels 5L, 5R), and then the rear differential is distributed on the rear wheel side. 26 and is distributed to the left and right wheels 5L and 5R.

Further, a differential limiting clutch mechanism 28 is provided in such a driving force distribution path. In other words,
An input gear 18 is engaged with the outer circumferential portion of the shaft 12 so that the shaft 1
2, a rotatable interlocking gear 20 is provided. The clutch mechanism 28 is interposed between the interlocking gear 20 and the shaft 12, that is, between the input gear 18 to the integral differential 14 and the input gear 24 to the rear wheels.

The frictional force of this clutch mechanism 28 is adjusted by an actuator 29, and by applying this frictional force, the difference in rotation between the front wheel side and the rear wheel side is reduced.
The distribution of driving force between the front wheels and the rear wheels approaches an evenly distributed state, and when the clutch mechanism 28 is directly connected, the driving force is evenly distributed between the front and rear wheels. Note that the actuator 29 may be of an electromagnetic type or a hydraulic type.

Furthermore, depending on the settings of the planetary gear mechanisms 30 and 40, the driving force distribution when the clutch mechanism 28 is not engaged and the clutch is free can be distributed mainly to the rear wheels or mainly to the front wheels. .

By the way, for example, in order to be able to start the turn comfortably at the beginning of the turn, and to be able to complete the turn while stabilizing the behavior of the vehicle in the latter half of the turn,
Normally, torque distribution is distributed closer to the rear wheels to ensure responsiveness during turning, but if driving stability is compromised, the torque distribution to the front wheels can be increased depending on the degree of damage. good. Therefore, it is only necessary to perform torque control in a range from, for example, torque distribution based on the rear wheels to uniform torque distribution between the front and rear wheels.

Therefore, in the integrated differential 14 as described above, the planetary gear mechanisms 30 and 40 may be set to realize such torque distribution based on the rear wheels, but such settings may be changed depending on the speed. For example, it is shown in a diagram as shown in FIG.

In FIG. 3, the horizontal axis represents the planetary gear mechanism 30,
40, the vertical axis is the rotational speed (N), C1 is the input from the engine to the carrier 32, C2
is the input from the planetary gear mechanism 30 to the carrier 42, R1
is the output from the ring gear 36 to the planetary gear mechanism 40, R
2 is the output from the ring gear 46 to the rear wheel side, S1 is the output from the sun gear 38 to the left front wheel, and S2 is the output from the sun gear 48
shows the output from to the right front wheel, where Z1 is the number of teeth of sun gear 38, Z2 is the number of teeth of ring gear 36, and Z3 is the number of teeth of sun gear 48.
Z4 indicates the number of teeth of the ring gear 46.

[0031] Here, i is the input torque from the engine,
Assuming that fl is the output to the front left wheel (front left wheel), fr is the output to the front right wheel (front right wheel), and r is the output to the rear wheel, the torque relational expression is as follows.

From the characteristics of the planetary gear, Tfl=[Z1/(Z1 +Z2)]・Ti
...(1.1)T
fr=[Z3/(Z3 +Z4)]・[Z2/(
Z1 + Z2 )]・Ti

...(1.2)
Tr = [Z4 / (Z3 + Z4 )]・[Z2 /
(Z1 +Z2)]・Ti

...(1.3
) Front left and right torque needs to be distributed equally, so Tfl
=Tfr From the above formula and formulas (1.1) and (1.2), Z1 ・(Z
3 + Z4 ) = Z2 ・Z3
...(1.4).

Here, the front wheel distribution ratio of driving force is a (however, 0<a<1), the rear wheel distribution ratio is 1-a, that is, the front wheel distribution ratio is as follows: Front wheel: Rear wheel = a: 1 −a, then equations (1.1) to (1
．． 3), a/(1-a)=[ Z1(Z3+Z4)+Z2 Z
3] /Z2 Z4...(1.5)

00
34] Also, the rotation speed relational expression is as follows. Ni is a condition for the front differential function to work properly.
=Nr =0 (input and rear rotation fixed) Nfr=-Nfl Therefore, from Fig. 3, -(Z1 /Z2)Nfl=[Z3/(Z3 +Z
4)]Nfr∴Z1 /Z2 =Z3 /(Z3 +
Z4) ・
...(1.6)

The conditions for establishing an integrated planetary gear of the center differential and front differential are the above equations (1.4) and (1
．． 5) and (1.6) must be satisfied at the same time. Therefore, rearranging these three equations, Z1 /Z2 = Z3 / (Z3 + Z4)
...(1.6
)a=(Z1 Z3 +Z1 Z4 +Z2 Z3)
/ [(Z1 +Z2) (Z3 +Z4)]

・・・
- (1.5)' When formula (1.6) is substituted into formula (1.5), the conditions for the establishment are as follows. Z1 /Z2 =Z3 /(Z3 +Z4)
...(1.6
)a=2Z3/(Z1 +Z2)
...(1
．． 7)

Therefore, for example, the planetary gear mechanism 3
If the sun gears 38 and 48 of 0 and 40 are set to the same size, from equation (1.6), Z1 = Z3, Z4 = Z2 - Z1
...(1
．． 8).

On the other hand, if the ring gears 36 and 46 of the planetary gear mechanisms 30 and 40 are set to the same size, the formula (1.6
), Z2 = Z4 , Z3 = (Z2 ・Z1 )/(Z2
-Z1) ...(1.9).

Therefore, for example, the front-rear driving force distribution ratio is
If front wheel: rear wheel = 40:60, a = 40/(40+60) = 0.4, and the size of each sun gear 38, 48 is Z1 = Z3
= 20 (assuming m = 2.5), from equations (1.7) and (1.8), Z2 = 80, Z3 = 20, Z4 = 60 (established when the number of planetary pinions is 4) ).

Since the driving force distribution device for a four-wheel drive vehicle as an embodiment of the present invention is constructed as described above, the driving force output from the engine 2 is distributed from the output shaft 4 to the transmission 6. After being transmitted and shifted, the signal is input from the output shaft (intermediate shaft) 8 of the transmission 6 to the integrated differential 14 via the gear mechanisms 16 and 18. In the integrated differential 14, the engine output is first determined by the planetary gear mechanism 30.
Through the left front wheel side and the other three wheel sides (right front wheel and left and right rear wheels)
and then distributed between the right front wheel side and the other two wheels (left and right rear wheels) through the planetary gear mechanism 40,
After this, on the rear wheel side, the power is distributed to the left and right wheels through the rear differential.

Furthermore, at this time, the distribution of driving force to the front and rear wheels is adjusted depending on the engagement state of the clutch mechanism 28. For example, if the drive force distribution is set to mainly focus on the rear wheels when the clutch is free as described above, as the engagement of the clutch mechanism 28 is strengthened, the drive force distribution to the front wheels will increase, and when the clutch mechanism 28 is locked, the drive force distribution will increase. , the driving force is equally distributed between the front and rear wheels (that is, 50:50).

[0041] Such a driving force distribution device for a four-wheel drive vehicle has the following advantages and effects.

■If there is approximately the same space as a bevel gear type front differential, the unequal distribution type center differential (torque distribution adjustable type center differential) and front differential can be installed together, which has the advantage of saving installation space.

■ By installing the center differential differential limiting device on the fourth shaft via the counter gear, the difference in rotation speed of the differential limiting section becomes the level before final deceleration, and the HCU (hydraulic coupling unit) and VCU When a rotation speed sensitive unit such as a viscous coupling unit (viscous coupling unit) is attached, there is an advantage that a low capacity unit can be used effectively.

■Fourth installation of center differential differential limiting device
The shaft can be built into the transmission case, and the transfer case only needs to cover the transfer bevel, making the device more compact. Furthermore, it is easy to use transmission system parts of other forms, which is advantageous in terms of cost.

[0045] Since the double shaft portion is eliminated, the structure is simplified, and this also has the effect of reducing the size and weight of the device and improving the ease of assembling the device.

[0046] In this example, the arrangement is of the E-W type, and since the direction of rotation of the engine and the direction of rotation of the front wheel drive shaft are the same, it is also advantageous in terms of vibration.

By the way, the structure of the driving force distribution device for a four-wheel drive vehicle of the present invention is not limited to the form of the above-described embodiment. It is distributed between the front wheel side and the other three wheel sides (the left front wheel and the left and right rear wheels), and then between the left front wheel side and the other two wheel sides (the left and right rear wheels) through the planetary gear mechanism 40. It is also possible to have a structure in which the power is distributed to the left and right wheels through a rear differential on the rear wheel side. Furthermore, the configuration of each gear of the planetary gear mechanisms 30 and 40 can also be freely set.

Furthermore, as described above, instead of the multi-disc clutch mechanism 28, a viscous coupling unit (VCU) or a hydraulic coupling unit (HCU) may be employed as the differential limiting mechanism. .

[0049]

Effects of the Invention As detailed above, according to the drive force distribution device for a four-wheel drive vehicle of the present invention, in a four-wheel drive vehicle, communication from the engine to four wheels, two front wheels and two rear wheels, is achieved. A driving force transmission path is provided with a first differential gear and a second differential gear, and the first differential gear is interposed between one of the four wheels and the other three wheels. and the second
A differential gear is interposed between the one wheel of the three wheels, a left and right pair of wheels, and the other two wheels of the three wheels, and the driving force transmission path is The following advantages and effects can be obtained by the configuration in which the above-mentioned differential limiting mechanism for limiting the differential movement between the front wheels and the rear wheels is attached.

■The center differential and front differential can be integrated to save installation space. ■The center differential differential limiter is connected to the 4th gear via the counter gear.
By installing it on the shaft, the difference in rotation speed of the differential limiting section can be kept at the level before final reduction, and rotation speed sensitive units such as HCU (hydraulic coupling unit) and VCU (viscous coupling unit) are attached. Low capacity can be used effectively when ■The fourth shaft on which the center differential differential limiting device is installed can be built into the transmission case, making the device more compact, making it easier to use parts from other types of transmission systems, and being cost-effective. ■ Eliminating the double shaft portion simplifies the structure, contributing to smaller and lighter equipment and improved ease of assembly. ■The rotation direction of the engine and the rotation direction of the front wheel drive shaft can be set in the same direction, which is advantageous in terms of vibration.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a driving force distribution device for a four-wheel drive vehicle as a first embodiment of the present invention.

FIG. 2 is a side view configuration diagram (a view taken in the direction of arrow A in FIG. 1) of a driving force distribution device for a four-wheel drive vehicle as a first embodiment of the present invention.

FIG. 3 is a speed diagram showing the relationship between gears of the driving force distribution device for a four-wheel drive vehicle as a first embodiment of the present invention.

FIG. 4 is a schematic diagram showing the configuration of a conventional driving force distribution device for a four-wheel drive vehicle, in which (a) is a plan sectional view and (b) is a side view configuration diagram.

FIG. 5 is a schematic diagram showing the configuration of another conventional driving force distribution device for a four-wheel drive vehicle, in which (a) is a plan sectional view and (b) is a side view configuration diagram.

[Explanation of symbols]

2 Engine 3L, 3R Front wheel 4 Output shaft (first shaft) 5L, 5R Rear wheel 6 Transmission 8 Output shaft of transmission 6 (intermediate shaft, second shaft) 10a, 10b Front wheel drive shaft (third shaft) 1
2 Axis (4th axis) 14 Integrated differential Differential (integrated differential) 1
5 Bevel gear mechanism 16 Output gear 17 Drive shaft 18 Input gear 20 Interlocking gear 22 Output gear 24 Input gear 26 Rear differential (rear differential) 27a, 2
7b Rear wheel drive shaft 28 Clutch mechanism 29 Actuator 30 Planetary gear mechanism 32 Carrier 34 Planetary gear 36 Ring gear 38 Sun gear 40 Planetary gear mechanism 42 Carrier 44 Planetary gear 46 Ring gear 48 Sun gear C1 Input C2 from the engine to the carrier 32
Input R1 from the planetary gear mechanism 30 to the carrier 42
Output R2 from the ring gear 36 to the planetary gear mechanism 40
Output from ring gear 46 to rear wheel side S1 Output from sun gear 38 to left front wheel S2 Output from sun gear 48 to right front wheel Z1 Number of teeth of sun gear 38 Z2 Number of teeth of ring gear 36 Z3 Number of teeth of sun gear 48 Z4 Number of teeth of ring gear 46 Number of teeth

Claims (2)

[Claims] Claim 1: A four-wheel drive vehicle, comprising a first differential gear and a second differential gear in a driving force transmission path leading from an engine to four wheels, two front wheels and two rear wheels, the first differential gear and the second differential gear. A differential gear is interposed between one of the four wheels and the other three wheels, and the second differential gear is interposed between one of the four wheels and the other three wheels. A differential limiter is provided between the left and right pair of wheels and the other two wheels of the three wheels, and limits the differential between the front wheels and the rear wheels in the driving force transmission path. A driving force distribution device for a four-wheel drive vehicle, characterized in that a mechanism is attached. Claim 2: The first differential gear and the second differential gear.
2. The driving force distribution device for a four-wheel drive vehicle according to claim 1, wherein the differential gears are each constructed of a planetary gear mechanism, and are arranged coaxially with each other.