JPH11263137A - Four-wheel drive vehicle equipped with automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the transmission efficiency of highest transmission stage by increasing by a center differential device a speed for a transmission stage having a highest transmission efficiency so as to obtain a highest transmission stage having a smallest transmission ratio. SOLUTION: In an automatic transmission 30, among transmission stages, a third speed for directly connecting an input shaft 14 with an output shaft 15 has a highest transmission efficiency. Thus, when a speed is further increased under the traveling condition of a fourth speed and a speed is shifted to a fifth speed as a highest transmission stage, the automatic transmission 30 is placed in the state of the third speed, the second sungear 53 of a center differential device 50 is simultaneously fixed by the engagement of a brake 63 for the fifth speed, and a carrier 55 is increasingly rotated. Then, the motive power of the third speed of the automatic transmission 30 is transmitted to front wheels after the carrier 55 by greatly increasing the speed of the center differential gear 50, and a speed is shifted to the fifth speed. Thus, since the third speed having the highest transmission efficiency is increased, a transmission efficiency is increased when a highest transmission stage is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel drive vehicle with an automatic transmission, and more particularly to a center differential device that further increases the driving force shifted by the automatic transmission, thereby providing the highest speed with the smallest gear ratio. The present invention relates to a four-wheel drive vehicle with an automatic transmission for obtaining a gear.

[0002]

2. Description of the Related Art The applicant of the present invention can change the distribution of driving force to the front and rear wheels by combining an automatic transmission that can be changed to four forward steps and one reverse step and a center differential device using a compound planetary gear. A controllable automatic transmission was developed and filed earlier (Japanese Unexamined Patent Publication No. Hei.
41 and JP-A-5-112147).

[0003] The automatic transmission employs a configuration in which the speed of the second speed of the automatic transmission is increased by the center differential device to obtain the fifth forward speed as the highest speed.

[0004]

However, in the above-mentioned prior art, when the fifth forward speed is obtained as the highest gear, the second speed is required.
The fifth gear ratio is set by multiplying the gear ratio of the second speed by the automatic transmission by the gear ratio of the center differential device, so that the reduction gear ratio by the second speed having a large reduction ratio is used. Therefore, the gear efficiency, that is, the transmission efficiency is disadvantageously reduced.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a four-wheel drive vehicle with an automatic transmission capable of improving transmission efficiency when obtaining the highest gear.

[0006]

In order to achieve the above object, according to the present invention, a compound planetary gear type center differential device is arranged in the middle of a drive system from an engine to front and rear wheels via an automatic transmission. A first output element for constantly transmitting power to one of the front and rear wheels, and a second for variably controlling the torque distribution between the front and rear wheels and the front and rear wheels.
In a four-wheel drive vehicle with an automatic transmission, a third output element for obtaining a predetermined gear is connected to a second sun gear of the center differential device. The speed ratio with the highest transmission efficiency obtained by the machine is increased by the center differential device to obtain the highest speed speed with the smallest speed ratio.

According to a second aspect of the present invention, in the first aspect of the present invention, a speed of the automatic transmission is increased by connecting the input shaft and the output shaft of the automatic transmission by the center differential device. It is characterized in that the highest gear stage with the smallest gear ratio is obtained.

According to a third aspect of the present invention, in the first aspect of the present invention, the automatic transmission changes a driving force by using a pair of planetary gears and locks the pair of planetary gears together. The obtained shift speed is increased by the center differential device to obtain the highest shift speed with the smallest speed ratio.

That is, in the four-wheel drive vehicle with the automatic transmission according to the present invention, the gear stage having the highest transmission efficiency obtained by the automatic transmission is increased by the center differential device, and the highest gear stage having the smallest gear ratio is obtained. , The transmission efficiency at the time of obtaining the highest gear is improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 illustrates a drive system in which an engine and an automatic transmission are vertically arranged in a vehicle longitudinal direction as a four-wheel drive vehicle with an automatic transmission to which the present invention is applied. First, a transmission case 3 is provided at the rear of the torque converter case 1 and the differential case 2.
The transfer case 4 and the extension case 6 are joined to the rear part of the transmission case 3, and the oil pan 5 is attached to the lower part of the transmission case 3.

Reference numeral 10 denotes an engine. A crankshaft 11 of the engine 10 is connected to a torque converter 13 having a lock-up clutch 12 inside the torque converter case 1, and an input shaft 14 from the torque converter 13.
Is input to the automatic transmission 30 inside the transmission case 3. The transmission output shaft 15 is output coaxially with the input shaft 14 from the automatic transmission 30, and the transmission output shaft 15 is coaxially connected to a center differential device 50 inside the transfer case 4.

Inside the transmission case 3, a front drive shaft 16 is arranged in parallel with the input and output shafts 14 and 15, and a rear end of the front drive shaft 16 is connected to a center differential device 50 by a pair of reduction gears 17 and 18. The front end of the front drive shaft 16 is transmitted to the front wheels via a front differential device 19 inside the differential case 2. On the other hand, a hydraulic multi-plate clutch device 60 is provided at the rear of the center differential device 50. The rear drive shaft 20 output from the hydraulic multi-plate clutch device 60 is rearwardly transmitted via a propeller shaft 21, a rear differential device 22, and the like. Driven by wheels.

The automatic transmission 30 is configured to obtain four forward speeds and one reverse speed by two sets of front planetary gears 31 and rear planetary gears 32. That is, the input shaft 14 is connected to the sun gear 32 a of the rear planetary gear 32, and the ring gear 31 b of the front planetary gear 31 and the carrier 32 c of the rear planetary gear 32 are connected to the transmission output shaft 15. A first one-way clutch 34 and a forward clutch 35 are provided in series between a coupling element 33 integral with the carrier 31c of the front planetary gear 31 and a ring gear 32b of the rear planetary gear 32, and are fixed to the coupling element 33. Between the case side which is a member,
A second one-way clutch 36 and a low reverse brake 37 are provided in parallel. An overrunning clutch 38 is provided between the coupling element 33 and the ring gear 32b in a bypass manner.

A connecting element 39 integral with the sun gear 31a of the front planetary gear 31 is provided with a band brake 40, and a coupling element 41 integral with the input shaft 14 is provided.
A high clutch 43 is provided between the carrier 31c and the integral connecting element 42. Further connecting element 39
A reverse clutch 44 is provided between and.

With the construction of the automatic transmission 30, the forward clutch 35 is engaged at the first speed in the D range or the third range and the second range, and in the case of acceleration, the two-way clutches 34, 36 act to actuate the ring gear together with the connecting element 33. 32
b, the sun gear 32
a, power is transmitted to the transmission output shaft 15 via the carrier 32c. At this time, during coasting, the first one-way clutch 34 becomes free, and even if the overrunning clutch 38 is engaged to restrict the free rotation of the first one-way clutch 34, the second one-way clutch 36 becomes free. The engine brake does not work. At the first speed in one range, the ring gear 32b is always locked via the overrunning clutch 38 by the engagement of the low reverse clutch 37, so that the engine brake operates.

In the D range or the second speed of the third and second ranges, the forward clutch 35 and the band brake 4
And the band brake 40 locks the sun gear 31a of the front planetary gear 31. Then, the carrier 31c and the ring gear 32b rotate via the connecting element 33, the forward clutch 35, and the first one-way clutch 34, and the ring gear 3
The power whose speed has been increased by the rotation of 2b is output. At this time, at the time of deceleration, by maintaining the connecting element 33 and the ring gear 32b in the connected state by the engagement of the overrunning clutch 38, the reverse driving force is transmitted to the engine side and the engine brake acts.

In the third range of the D range or the third range, the forward clutch 35 and the high clutch 43 are engaged,
The input shaft 14 is connected to the connecting element 4 by the high clutch 43.
1, 42, the carrier 31c, the connecting element 33, the forward clutch 35, and the first one-way clutch 34 to connect to the ring gear 32b. For this reason, the rear planetary gear 32 is integrated with the input shaft 14 and the transmission output shaft 1.
5 is directly connected. At this time, when the overrunning clutch 38 is engaged during deceleration, the idling of the first one-way clutch 34 is restricted, so that the engine brake operates in the same manner as the second speed.

At the 4th speed in the D range, the sun gear 31a is locked by the engagement of the band brake 40 in addition to the above. Therefore, the high planetary gear 31
3, the power input to the carrier 31c by the ring gear 3
1b, which is transmitted to the transmission output shaft 15. In this case, since the first and second one-way clutches 34 and 36 do not intervene, the engine brake always operates.

Here, the functions of the automatic transmission 30 according to the present embodiment in the first to fourth speeds are summarized as shown in FIG. As is clear from the figure, in the automatic transmission 30, good transmission efficiency can be obtained in the first, third, and fourth speeds. Of course, the input shaft 14
The third speed obtained by directly connecting the motor and the output shaft 15 has the highest transmission efficiency.

In the R range, the power of the input shaft 14 is input to the sun gear 31a by the engagement of the reverse clutch 44. In addition, since the carrier 31c is locked together with the connecting element 33 by the engagement of the low reverse brake 37, the front planetary gear 31 reversely rotates to the ring gear 31b to output power having a large gear ratio, and this reverse rotation power is transmitted to the transmission output shaft 15. Transmit and go to reverse speed. Thus, the automatic transmission 30 has four forward speeds and one reverse speed.

On the other hand, an oil pump 45 is provided in front of the automatic transmission 30 and is always driven by a drive shaft 46 on the pump impeller side of the torque converter 13. A control valve body 47 is housed in the oil pan 5, and supplies and discharges oil to and from each of the above-mentioned clutches and brakes to be selectively engaged.

Referring to FIG. 2, the parts of the center differential device 50 and the hydraulic multiple disc clutch device 60 will be described. First, the first and second gears are provided behind the transmission output shaft 15.
The rear drive shaft 20 is arranged coaxially via the intermediate shafts 23 and 24 of the first embodiment. The transmission output shaft 15 has a bearing 28.
The reduction gear 17 on the front wheel side is rotatably fitted through the transmission output shaft 15 and the reduction gear 1.
A center differential device 50 is coaxially arranged between the seventh and first and second intermediate shafts 23 and 24.

The center differential device 50 is composed of a compound planetary gear, and includes a first sun gear 51 formed on the transmission output shaft 15 and a second sun gear 53 formed on the second intermediate shaft 24. Have.
The carrier 55 is formed by integrating left and right flanges 55a and 55b by an arm 55c.
First and second pinions 52 and 54 formed integrally in the axial direction are rotatably mounted via a needle bearing 27 on a pinion shaft 56 mounted between a and 55b.
Then, a first pinion 52 is provided on the first sun gear 51,
The second sun gear 53 is meshed with the second pinion 54, and is configured to output the torque-distributed power to the second intermediate shaft 24 as a third output element.

On the other hand, a first intermediate shaft 23 as a second output element is further loosely fitted inside the second intermediate shaft 24, and two sun gears 51, 53 are provided at the front end of the first intermediate shaft 23.
Is connected to the arm 55c of the carrier 55 to perform an operation such as differential limiting. Further, on one flange 55a of the carrier 55,
Reduction gear 17 as a first output element is coupled to output the power of carrier 55. here,
At the front of the carrier 55, a reduction gear 17 integral therewith is supported by the wall 3a of the transmission case 3 via a ball bearing 26a.
The outer periphery of the boss portion 55d of the transfer case 4 is supported by the wall portion 4a of the transfer case 4 via the ball bearing 26b, and the inner periphery of the boss portion 55d is
6c, it is installed rotatably with both ends supported.

Referring to FIG. 5, the structure of the center differential device 50 will be described in more detail. Flanges 55e are protruded at three places on the circumference of the rear flange 55b of the carrier 55, and three sets of the flange 55e and the front flange 55a are provided. The pinion shaft 56 and the first and second pinions 52, 54 are mounted at equal intervals, and arms 55c are arranged at three locations on the circumference between them. The arm 55c is formed in a small diameter with a U-shaped middle in the middle, and a spline groove 55g is provided on the inner periphery of the small diameter portion 55f. The connecting member 57 connected to the end of the first intermediate shaft 23 is formed in a substantially triangular shape,
Three locations on the circumference are formed in an L-shaped cross section, and spline grooves 57a are provided. These spline grooves 55g, 5
7a is set slightly smaller than the inner diameter of the boss portion 55d of the flange 55b, whereby the first spline groove is aligned.
By inserting the connecting member 57 of the intermediate shaft 23 from the boss portion 55d into the carrier 55, the two spline grooves 5
5g and 57a are fitted and connected.

This center differential device 50
According to the configuration described above, the power input to the first sun gear 51 is
The torque is transmitted to the carrier 55 and the second sun gear 53 at a torque distribution ratio according to the gear specifications of the first and second sun gears 51 and 53 and the first and second pinions 52 and 54, and the torque is distributed to the front and rear wheels. It has a function to do. Further, it has a differential function of absorbing a rotational speed difference between the carrier 55 and the second sun gear 53 caused by a difference in turning radius during turning due to the planetary rotation of the first and second pinions 52 and 54.

Here, the torque distribution function of the center differential device 50 will be described in detail with reference to the schematic diagram of FIG. The input torque of the first sun gear 51 is Ti, the mesh pitch radius thereof is rs1, the front side torque of the carrier 55 is TF, the mesh pitch radii of the first and second pinions 52 and 54 are rp1 and rp2, respectively. The rear side torque of the second sun gear 53 is TR, and the meshing pitch radius is r.
If s2, then Ti = TF + TR (1) rs1 + rp1 = rs2 + rp2 (2)

The tangential load P acting on the meshing point between the first sun gear 51 and the first pinion 52 is the tangential load P1 acting on the carrier 55, the second sun gear 53 and the second pinion. Since it is equal to the sum of the tangential load P2 acting on the meshing point with 54, the following equation is established. P = Ti / rs1 P1 = TF / (rs1 + rp1) P2 = TR / rs2 Ti / rs1 = {(TF / (rs1 + rp1)} + TR / rs2 (3) Then, the equations (1) and (2) are replaced by the equations (3). TF = (1−rp1 · rs2 / rs1 · rp2) × Ti TR = (rp1 · rs2 / rs1 · rp2) × Ti

From this, the first and second sun gears 5
It can be seen that the reference torque distribution ratio of the front torque TF and the rear torque TR can be freely set by the engagement pitch radii of the first and second pinions 52 and 54 with the first and second pinions 52 and 54. Here, rs1, rp1, rp2, and rs2 can be replaced with the respective numbers of teeth Zs1, Zp1, Zp2, and Zs2, and Zp1 = Zp2 = 24, Zs1 = 30, and Zs
If 2 = 15, then TF: TR = 50.0: 50.0.

Next, the center differential device 5
A case where 0 is used as a gearbox will be described. The composite planetary gear type center differential device 50 can obtain a predetermined speed increasing gear ratio by fixing the second intermediate shaft 24. , The gear is further shifted to the fifth speed as the highest gear having the smallest gear ratio. Therefore, for example, the case where the third speed is used will be described. The fifth speed gear ratio i5 is as follows based on the third speed gear ratio i3 and the speed increasing gear ratio ip of the center differential device 50. i5 = i3 · ip

Here, if the above-described gear specifications of the center differential device 50 are used, ip = (30
−15) /30=0.500, for example, i3 = 1.
If 000, i5 = 0.500, and a proper gear ratio interval can be obtained at the fifth speed, which is smaller than the fourth speed. In this case, as shown in FIG.
Since the fifth speed is obtained by using the power of the third speed having the highest transmission efficiency among the fourth speeds, good transmission efficiency can be obtained. On the other hand, in the fifth speed, the hydraulic multiple disc clutch 62
The transmission torque is generated by controlling the hydraulic pressure in accordance with the traveling state and road surface conditions, and a four-wheel drive in which the torque distribution of the front and rear wheels can be controlled.

In FIG. 3, a hydraulic multiple disc clutch device 60 is shown.
Will be described. First, a hydraulic multi-plate clutch 61 is provided between the second intermediate shaft 24 and the rear drive shaft 20 as a frictional engagement element for transmitting torque, and is disposed between the first intermediate shaft 23 and the rear drive shaft 20. And a hydraulic multi-plate clutch 62 as a frictional engagement element for differential limiting and torque transfer.
And a fifth speed brake 63 as a frictional engagement element for preventing the differential function of the center differential device 50 and rotating the carrier 55 at a higher speed, provided on the second intermediate shaft 24. And these hydraulic multi-plate clutches 6
The first and second speed brakes 63 are connected to the first intermediate shaft 23 immediately after the center differential device 50.
Are superposed three-dimensionally in the radial direction around them and are arranged coaxially. That is, the hydraulic multi-plate clutches 61 and 62 are both connected to the rear drive shaft 20, and the hydraulic multi-plate clutch 61 and the fifth speed brake 63 are both connected to the second intermediate shaft 24. A fifth speed brake 63 is provided outside the hydraulic multi-plate clutch 61.
However, a hydraulic multi-plate clutch 62 is disposed inside.

Therefore, the drum member 6 is attached to the second intermediate shaft 24.
4 is spline-coupled, and a drum member 65 integrally formed with the front end of the rear drive shaft 20 is disposed inside the drum member 64, and a hydraulic multi-plate clutch 61 is provided between the drum members 64 and 65. The hydraulic multi-plate clutch 61 has a drive plate 6 between the drum members 64 and 65.
1a and the driven plate 61b are provided alternately, and a hydraulic chamber 61c, a piston 61d, and a return spring 61e are provided inside the drum member 64, and the second intermediate shaft 24 is provided.
Is connected to or disconnected from the rear drive shaft 20.

The fifth speed brake 63 includes a drum member 64
A drive plate 63a and a driven plate 63b are provided alternately between the transfer case 4 and the transfer case 4. A hydraulic chamber 63c, a piston 63d, and a return spring 63e are provided inside a wall 4a of the transfer case 4, and a second intermediate shaft is provided. 24 is configured to be fixed or free.

The hydraulic multi-plate clutch 62 includes a first intermediate shaft 2
3 and a hub member 66 and a drum member 65 which are spline-connected
, Drive plates 62a and driven plates 62b are provided alternately. Further, the hydraulic chamber 62c, the piston 62d, and the return spring 62e generate a large pressing force inside the boss portion 6a of the extension case 6 on the fixed side. It is provided as possible. The piston 62d is connected to the plate via a ball bearing 62f and a pressing member 62g, and is configured to generate a variably controlled differential limiting torque and transmission torque. A bearing 28 is provided at the shaft fitting portion, and a thrust bearing 25 is provided at the abutting portion between the shafts and the shaft and other members.
Is interposed. Also, reference numerals 70 to 74 in FIG.
Is a lubricating oil passage.

The hydraulic multi-plate clutches 61 and 62 and the fifth speed brake 63 are provided with a control valve body 4.
At 7, hydraulic control is performed together with shift control of the automatic transmission 30 and the like. That is, when the automatic transmission 30 shifts the gear between four forward speeds and one reverse speed, the fifth speed brake 63 is released and the hydraulic multiple disc clutch 61 is engaged. A differential limiting torque is generated in the multiple disc clutch 62. On the other hand, when the vehicle speed rises above the set value at the fourth speed, the fifth speed brake 63 is engaged to release the hydraulic multiple disc clutch 61, and at this time, the hydraulic multiple disc clutch 62 is Generates transmission torque.

FIG. 6 shows the clutch and brake operations of the automatic transmission 30 and the center differential device 50 in each of the D range and R range gears. In FIG. 6, the circles indicate clutches,
The brake engagement operation, ● represents the generation of differential limiting torque by the hydraulic multi-plate clutch 62, and ◎ represents the hydraulic multi-plate clutch 62.
Respectively shows transmission torque states in a case where the driving force distribution control to the front and rear wheels is performed by the following.

FIG. 7 shows the gear ratios, the examples of the gear ratios, and the torque distribution ratios at each shift speed. In FIG. 7, α1 is the number of teeth Zs1 of the sun gear 31a of the front planetary gear 31 and the ring gear 31b.
Α1 = Zs1 / Zr1, α2 is the ratio of the number of teeth Zs2 of the sun gear 32a of the rear planetary gear 32 to the number of teeth Zr2 of the ring gear 32b, and α2 = Zs2 /
Zr2 is shown.

The relationship between the number of rotations of each element of the front planetary gear 31 is given by the following equation. Nr1 + α1 · Ns1 = (1 + α1) · Nc1 where α1 = Zs1 / Zr1 The relationship between the rotation speeds of the elements of the rear planetary gear 32 is expressed by the following equation. Nr2 + α2 · Ns2 =
(1 + α2) · Nc2 where α2 = Zs2 / Zr2, where Nr1 in the above equation is the rotation speed of the ring gear 31b of the front planetary gear 31, and Ns1 is the sun gear 3.
Nc1 is the rotation speed of the carrier 31c, Nr2 is the rotation speed of the ring gear 32b of the rear planetary gear 32, Ns2 is the rotation speed of the sun gear 32a,
Nc2 is the rotation speed of the carrier 32c.

Next, the operation of the present embodiment will be described. First, the power of the engine 10 is the torque converter 1
3, input to the automatic transmission 30 via the input shaft 14, and two sets of front planetary gears 31 and rear planetary gears 3
2, the clutches 44, 43, 35, 38, 36, 3
Due to the selective engagement of the brake 4 and the brakes 40 and 37, when shifting to the D range, the speed is automatically changed to the first to fourth forward speeds, and when shifting to the R range, the reverse speed is achieved. Then, the shifting power is input from the transmission output shaft 15 to the first sun gear 51 of the center differential device 50, and the torque is distributed. In this case, the hydraulic multiple disk clutch 61 of the hydraulic multiple disk clutch device 60 is engaged, and the second sun gear 53 of the center differential device 50 is engaged.
Are connected to the rear drive shaft 20.

Here, TF: TR = 50.0: 5 according to the gear specifications of the center differential device 50.
Since it is set to 0.0, 50.0% of the shifting power is distributed to the carrier 55 and 50.0% is distributed to the second sun gear 53 for output. The power of the carrier 55 is transmitted to the front wheels via a reduction drive gear 17, a reduction driven gear 18, a front drive shaft 16, and a front differential device 19. The power of the second sun gear 53 is supplied to the second intermediate shaft 24,
The transmission is transmitted to the rear wheels of the hydraulic multi-plate clutch 61 and the rear drive shaft 20 and thereafter, and four-wheel drive travel is performed. That is, in the four-wheel drive vehicle with the automatic transmission according to the present embodiment, the front-rear distribution ratio of the drive torque is 50:50, and the steer characteristics of the vehicle are made closer to the neutral steer. Further, at the time of turning in the four-wheel drive running, the difference in rotation speed between the front and rear wheels caused at the time of turning is absorbed by the planetary rotation of the first and second pinions 52 and 54 of the center differential device 50, so that the vehicle can be turned freely. .

Next, when the rear wheel slips first on a slippery road surface, for example, as shown in FIG. 4, the differential limiting torque Tc of the hydraulic multiple disc clutch 62 is controlled according to the slip state. You. That is, the first and the second on the carrier 55 side of the center differential device 50.
Between the pinion 52, 54 and the second sun gear 53,
Another transmission path formed by the small diameter portion 55f of the carrier 55, the connecting member 57, the first intermediate shaft 23, and the hydraulic multi-plate clutch 62 is configured to be bypassed. The high-speed rear wheel-side second sun gear 53 is moved to the low-speed front wheel-side carrier 55.
Then, a torque bypass is performed according to the differential limiting torque Tc.
Therefore, torque distribution control is performed near the front wheels to prevent rear wheel slip and improve running performance. Even in the case where the front wheel slips first, the torque distribution control is performed toward the rear wheel by the operation opposite to that described above, so that the running performance is improved.

Further, when the differential limiting torque Tc becomes maximum, the center differential device 50 is locked by a direct connection between the second sun gear 53 and the carrier 55 to be a direct connection type four-wheel drive. The corresponding torque distribution results.

As described above, the differential limiting torque Tc of the hydraulic multi-plate clutch 62 is controlled in accordance with the slip state, and the differential limiting torque generated by the engagement of the gears constituting the center differential device 50 and the thrust load is expressed by T.
c, the input torque to the center differential device 50 is Ti, the distribution torque to the front wheels is TF, the distribution torque to the rear wheels is TR, the front axle rotation speed is NF, and the rear axle rotation speed is NR. When NF> NR, TF = (0.5 · Ti) −Tc TR = (0.5 · Ti) + Tc When NF <NR, TF = (0.5 · Ti) + Tc TR = (0.5 · Ti) Ti) -Tc can be obtained, and a part of the driving force can be transferred from the slip-side axle to the non-slip-side axle to improve the traveling performance of the vehicle.

On the other hand, when the speed is further increased due to the fourth speed running condition, the automatic transmission 30 enters the third speed state, and at the same time, the second sun gear of the center differential device 50 is engaged by the engagement of the fifth speed brake 63. 53 is fixed, and the carrier 55 rotates at an increased speed. Therefore, the automatic transmission 30
The third speed power of the center differential device 5
At 0, the speed is greatly increased and transmitted to the front wheels after the carrier 55, and the speed is shifted to the overdrive fifth speed having a smaller gear ratio than the fourth speed, thereby enabling high-speed running.

At this time, when the transmission torque TD of the hydraulic multi-plate clutch 62 is controlled in accordance with the running state, the state of the front wheel slip, and the like, the small diameter portion 55f of the carrier 55
7, torque is also transmitted to the rear wheels via the first intermediate shaft 23 and the hydraulic multi-plate clutch 62 (see FIG. 4). Therefore, four-wheel drive traveling is performed in which the slip of the front wheels can be prevented and the torque distribution of the front and rear wheels can be similarly controlled.

As described above, according to the present embodiment, the input and output shafts 14 and 15 are directly connected to the fifth speed (highest gear) among the gears obtained by the automatic transmission 30. The third speed is obtained by increasing the speed by the center differential device 50. That is, in the third speed according to the present embodiment, since the input and output shafts 14 and 15 are directly connected and the speed increase or deceleration by the automatic transmission 30 is not performed, the power to the center differential device 50 is not transmitted. The transmission efficiency is the highest, and the transmission efficiency can be improved in obtaining the highest gear.

In the present embodiment, since the third speed directly connecting the input shaft 14 and the output shaft 15 has the highest transmission efficiency, the third speed is increased to obtain the fifth speed as the highest speed stage. However, for example, a pair of planetary gears 31 and 32 of the automatic transmission 30 are locked together to obtain a shift speed with the best transmission efficiency, and the obtained shift speed is increased by the center differential device 50. Alternatively, the highest gear with the smallest gear ratio may be obtained.

[0049]

As described above, in the four-wheel drive vehicle with an automatic transmission according to the present invention, the gear stage having the highest transmission efficiency obtained by the automatic transmission is increased by the center differential device to achieve the highest gear change. By obtaining the highest shift speed with a small ratio, the transmission efficiency when obtaining the highest shift speed can be improved.

[Brief description of the drawings]

FIG. 1 is a skeleton diagram showing a drive system of a four-wheel drive vehicle with an automatic transmission.

FIG. 2 is an enlarged sectional view of a part of a center differential device and a hydraulic multi-plate clutch device.

FIG. 3 is an enlarged sectional view of a portion of the hydraulic multi-plate clutch device.

FIG. 4 is a schematic diagram illustrating a flow of a torque distribution state, a differential limitation, and a transmission torque for direct connection.

FIG. 5 is an exploded perspective view of a center differential device.

FIG. 6 is a table showing the operation of each part of the automatic transmission and the center differential device.

FIG. 7 is a table showing a gear ratio and a torque distribution ratio of a four-wheel drive vehicle with an automatic transmission according to an embodiment of the present invention.

FIG. 8 is a table showing functions of an automatic transmission and a center differential device when a D range is selected.

[Explanation of symbols]

 Reference Signs List 10 engine 15 output shaft 17 reduction gear (first output element) 20 rear drive shaft 23 first intermediate shaft (second output element) 24 second intermediate shaft (third output element) 30 automatic transmission 50 Center differential device 53 Second sun gear 55 Carrier 60 Hydraulic multi-plate clutch device 61, 62 Hydraulic multi-plate clutch 63 Brake for fifth speed

Claims (3)

[Claims] 1. A compound planetary gear type center differential device is disposed in the middle of a drive system from an engine to an front and rear wheel via an automatic transmission, and power is always transmitted to one of the front and rear wheels to a carrier of the center differential device. And a second output element for variably controlling the torque distribution of the front and rear wheels and variably controlling the torque distribution of the front and rear wheels, and a second sun gear of the center differential device, In a four-wheel drive vehicle with an automatic transmission, in which a third output element for obtaining a third gear is connected, a gear having the highest transmission efficiency obtained by the automatic transmission is increased by the center differential device, and A four-wheel drive vehicle with an automatic transmission, characterized by obtaining the highest gear stage with a small ratio. 2. The speed ratio obtained by connecting an input shaft and an output shaft of the automatic transmission is increased by the center differential device to obtain a highest speed stage having the smallest speed ratio. Item 4. A four-wheel drive vehicle with an automatic transmission according to item 1. 3. The automatic transmission according to claim 1, wherein the driving force is shifted using a pair of planetary gears, and a shift speed obtained by locking the pair of planetary gears together is increased by the center differential device. 4. The four-wheel drive vehicle with an automatic transmission according to claim 1, wherein a maximum gear stage having a small ratio is obtained.