JPH0737211B2 - Power transmission device for four-wheel drive vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a power transmission device for a four-wheel drive vehicle of a full-time system having a center differential device, and particularly a power for a four-wheel drive vehicle suitable for use in passenger cars. The present invention relates to a transmission device, and more particularly to control of a differential control device that controls the differential of a center differential device.

(B) Conventional Technology In general, a power transmission device for a four-wheel drive vehicle performs a switching operation between a two-wheel drive state and a four-wheel drive state when it is a part-time system, and a center operation when it is a full-time system. It requires an operation to operate or release the differential device, the driver needs the above operation depending on the road surface condition, corner curvature, etc., and requires a high driving technique in order to fully exhibit the characteristics of four-wheel drive. .

Therefore, a power transmission device for a four-wheel drive vehicle of a wet multi-plate clutch system and a traction control system has been devised as a device that does not require the above-mentioned operation.

The wet multi-plate clutch system is based on a part-time system power transmission device for four-wheel drive vehicles, for example, a power transmission device for four-wheel drive vehicles based on front-wheel drive, and is based on hydraulic pressure that changes in running conditions, such as an automatic transmission. The power is transmitted to the rear wheel side via a wet multi-plate clutch that is crimped by the line pressure in the above. This allows the clutch to slide during cornering to absorb the difference in rotation between the front and rear wheels, and to control the clutch crimping force. Then, the drive torque to the rear wheels is changed.

In addition, the traction control system uses a hydraulic clutch and a center differential device in combination, such as FR (front engine / rear drive) during normal driving.
When the vehicle is driven as a wheel drive vehicle and the drive wheels (rear wheels) run idle, the on-vehicle computer determines and the center differential device is connected by a hydraulic clutch to distribute 35% of the drive torque to the front wheels. If the wheels still idle, the center differential device is directly connected and the front-rear driving torque is distributed at 50:50.

The above-described power transmission device for a four-wheel drive vehicle of the wet multi-plate clutch system is a clutch crimp that can withstand the drive torque when traveling four wheels because the front wheel drive is mainly used to control the drive of the rear wheels through the wet multi-plate clutch. To give power,
It is necessary to constantly apply a relatively high oil pressure, and a relatively low oil pressure is supplied when the vehicle is traveling at a low speed during tight corners, with reference to the relatively high oil pressure. That is, the wet multi-plate clutch system basically allows the front and rear wheels to be directly connected to each other to allow slippage, requires a large clutch capacity, and therefore tends to always cause slippage between the road surface and the tire. In addition to deteriorating the characteristics, the tire is worn relatively early, the clutch hydraulic pressure is not sufficiently reduced even at the tire corner, and the rotation difference between the front and rear wheels cannot be sufficiently absorbed.

Further, the traction control system requires an advanced computer such as constantly monitoring the rotation speed of the wheels, resulting in an extremely complicated and expensive device.

Further, the applicant of the present invention, as disclosed in Japanese Patent Laid-Open No. 62-74713, supplies accumulator control pressure as engagement pressure to a Sendiff lock clutch of a center differential device so that when turning by steering at a tight corner. A power transmission device for a four-wheel drive vehicle has been proposed which prevents a tight corner braking phenomenon that occurs with a simple device without using a complicated electronic control device.

The power transmission device is made by paying attention to the fact that the accumulator control pressure has a low pressure characteristic in a region where the throttle opening is low, and normally supplies a line pressure to a hydraulic actuator that performs differential limiting. Then, the differential control clutch is completely engaged, and the hydraulic pressure lower than the line pressure is supplied only when the throttle opening is small so that the clutch can be slipped.

(C) Problems to be solved by the invention However, the tight corner braking phenomenon occurs not only when the throttle opening is low such as when entering a garage, but also when traveling on a steeply curved uphill road on a mountain road. This occurs even when the throttle opening is relatively high, and in such a power transmission device for a four-wheel drive vehicle, a tight corner braking phenomenon occurs in such a case.

Further, for example, when a vehicle travels on a paved road at a high speed, if there is a difference in the diameter of the front and rear tires due to a difference in air pressure or the like, it is necessary to absorb the differential generated by the difference in the diameter by the center differential device. With the above accumulator control pressure, since the throttle opening is relatively high during high-speed traveling, it becomes equal to the line pressure and the clutch is directly connected, causing tire wear,
Fuel efficiency will deteriorate.

In addition, when traveling on a snowy road, etc., the friction coefficient between the road surface and the tire is low, tire slip is likely to occur, and it is possible to prevent either the front wheel or the rear wheel from idling by directly connecting the center differential lock clutch. Desirable,
Generally, when traveling on snowy roads, etc., the throttle opening is relatively low, so the accumulator control pressure is
A low hydraulic pressure is obtained by greatly reducing the line pressure. Therefore, if the supplied hydraulic pressure is too low, differential limiting cannot be performed by the clutch, and the running performance of the vehicle is deteriorated when the friction coefficient of a snow road or the like is low. There is fear.

Therefore, the present invention has a simple structure, but can properly control the differential limiting clutch of the center differential device at any time, thereby solving the above-mentioned problems.
An object of the present invention is to provide a power transmission device for a wheel drive vehicle.

(D) Means for Solving the Problem The present invention has been made in view of the above circumstances, and an automatic transmission that changes a power transmission path by selectively supplying a line pressure from a hydraulic control device and shifts the speed. A center differential device (18) for branching and transmitting the driving force from the automatic transmission to the front wheel side and the rear wheel side, and a differential control device (10) for controlling the differential of the center differential device.
In the power transmission device for a four-wheel drive vehicle, the differential control device includes a wet friction material clutch (26) and a predetermined pressure for pressing the wet friction material clutch by a predetermined hydraulic pressure from the hydraulic control device. Hydraulic actuator (2 that controls the differential of the center differential device by connecting with
7), wherein the hydraulic control device is switched to a plurality of driving ranges including at least a normal driving range (D) by a driver's operation, and a manual valve for outputting a signal pressure according to the plurality of driving ranges. (55)
And a first regulator valve (46) that regulates the hydraulic pressure from the hydraulic pump (45) and outputs it as the line pressure (P _L ).
Is disposed between the first regulator valve (46) and the hydraulic actuator (27), the signal pressure from the manual valve (55) is input, and the manual valve is set to the normal travel range (D). ) Is increased according to the throttle opening and is lower than the line pressure (P _L ) in the entire throttle opening, and is related to the friction coefficient between the wheel and the road surface, When the friction coefficient is low, the wet friction material clutch (26) is in the engaged state, and when the friction coefficient is high, the wet friction material clutch (26) is in the slip state. _L ) depressurizes the hydraulic actuator (27)
And a second regulator valve (40) for supplying to the power transmission device for a four-wheel drive vehicle.

(E) Operation and effects of the invention Based on the above configuration, the second regulator valve (40)
Is increased below the line pressure (P _L ) in the entire throttle opening range when the manual valve (55) is switched to the normal travel range (D).
Further, in relation to the friction coefficient between the wheel and the road surface, when the friction coefficient is low, the wet friction material clutch (26) is engaged, and when the friction coefficient is high, the wet friction material clutch (26) is slipped. The line pressure (P _L ) is reduced to a predetermined hydraulic pressure (C) that is brought into a state, and the hydraulic actuator (27)
Supply to.

Therefore, even when the throttle opening is relatively high, such as when traveling on a steeply curved uphill road on a mountain road of a paved road, the predetermined hydraulic pressure (C) is lower than the line pressure (P _L ) as described above and When the friction coefficient with the road surface is high, the clutch slips, so the tight corner braking phenomenon can be prevented.

Also, for example, when the vehicle travels at high speed on a paved road, even when the throttle opening is high such that a difference between the front and rear tires causes a differential between the front wheels and the rear wheels,
Since the friction coefficient between the tire and the road surface is high, the wet friction material clutch (26) slips before the tire slips, and the center differential device (18) can absorb the rotation difference between the front wheel and the rear wheel. .

Further, when traveling on a snowy road or a wet road surface where the friction coefficient is low, when slipping is attempted on the front wheels or the rear wheels, the friction coefficient between the road surface and the tire is low. 26) is in a coupled state without slippage, and the driving force can be transmitted from the front wheels and the rear wheels to the road surface without causing either the front wheels or the rear wheels to idle.

Further, even when the throttle opening such as when entering a garage is low, the clutch (26) slips and the tight corner braking phenomenon can be prevented.

Therefore, according to the present invention, it is possible to prevent the tight corner braking phenomenon, the deterioration of fuel consumption, and the early wear of tires in the normal driving range even in any running state, and to provide an expensive and complicated electronic control device. Although it is an inexpensive structure which is not used, the driver can drive in a four-wheel drive state without requiring complicated operations.

The reference numerals in the parentheses are for the purpose of contrasting with the drawings, but do not limit the configuration of the present invention in any way.

(F) Example Hereinafter, an example of the present invention will be described with reference to the drawings.

As shown in FIG. 1, a power transmission device U for a full-time front engine front four-wheel drive vehicle of a full-time type has an input gear 1 to which power is transmitted from an engine (not shown) via a torque converter and an automatic transmission. The input gear 1 is fixed to the gear mount case 2. The mount case 2 is composed of split case pieces, is fastened together with the input gear 1 by bolts 12, and is supported by the support case 9 by tapered roller bearings 9a and 9b. Inside the mount case 2, the front differential device 3 and A differential control device 10 is housed. Further, the front differential device 3 has a front differential case 3c which is rotatably supported by two needle bearings 11a and 11b in the mount case 2, and the differential case 3c.
Forms a carrier by vertically supporting the pinion shaft 3d that supports the pinion 3p, and the left and right side gears 3a, 3b.
Are rotatably supported by extending in the left-right direction, and the left and right front axles 8 are respectively attached to the side gears 3a and 3b.
l and 8r are connected to each other so that power can be transmitted.

Further, a transfer case that can be divided into two parts on the right side of the input gear mount case 2, that is, behind the engine.
13 is assembled, and the transfer unit 15 is assembled in the transfer case 13 coaxially with the input gear mount case 2 and the front differential device 3. The transfer portion 15 has a ring gear mount case 16, the ring gear mount case 16 can be divided into left and right parts, and integrally supports a rear wheel drive ring gear 17 formed of a hypoid gear.
The transfer case (13) is rotatably supported by a pair of tapered roller bearings (19, 19). Then, the gear 17 is constantly meshed with a gear 21 formed of a hypoid gear formed on the driven pinion shaft 20,
The driven pinion shaft 20 is connected to the left and right rear axle shafts via a propeller shaft and a rear differential device (not shown) so that power can be transmitted.
A center differential device 18 is arranged in the ring gear mount case 16, and the center differential device 18 includes a differential carrier 18c whose tip is in an open state. Further, the differential carrier 1
8c is connected to the sleeve portion 2b extending from the input gear mount case 2, and the opposite side of the connecting boss portion 18c 'is open to form an open end, and the open end portion and the connecting boss 18c' are connected to each other. It is rotatably supported by the ring gear mount case 16 via needle bearings 23, 23. Further, a pinion shaft 18d for supporting the pinion 18p is attached to the differential carrier 18c, the right side gear 18b is directly spline-coupled to the ring gear mount case 16, and the left side gear 18a is connected to the differential carrier. linked to the differential case 3c of the front differential 3 through a boss portion 18c 'fitted within and sleeve portion 3c which is fitted on the right front axle shafts 8r _1'.

A spline joint 22 is slidably fitted to a spline formed at the tip of the sleeve portion 2b of the input gear mount case 2, and the spline joint 22 is axially operated by an operating lever (not shown). The lock position (see the upper half of FIG. 1) that engages with the spline formed on the sleeve portion of the ring gear mount case 16 and the release position (see the lower half of FIG. 1) that disengages the mechanism are switched. It constitutes a diff lock mechanism. The mechanical diff lock mechanism is normally in the released position, but can be switched to the locked position when the tire is placed on the roller and various inspections are performed in a service factory or the like.

The differential control device 10 is arranged in the input gear mount case 2 provided so as to cover the front differential device 3 and coaxially with the device 3, and the wet friction multi-plate clutch 26 and its hydraulic actuator. It consists of 27. The clutch 26 has its separator connected to the mount case 2 and its friction plate connected to the differential case 3c, and the separator and the friction plate are pressed and controlled by a hydraulic actuator 27. The hydraulic actuator 27 includes a first piston 28 and a second piston that are oil-tightly housed in a cylinder formed in the mount case 6.
29, and a reaction force plate 30 disposed between both pistons in an oil-tight manner. These pistons include a first piston 28 in contact with an outer peripheral flange portion of the second piston 29, and The reaction plate 30 is in contact with the cylinder end surface to form a double piston. A valve unit 31 for the differential control device 10 is installed in the transfer case 13, and the control hydraulic pressure from the unit 31 is transmitted through the pipe 36 and the oil passages 37, 38 to the first piston 28 of the hydraulic actuator 27. And the second piston 29.

Further, the valve unit 31, as shown in detail in FIG.
The switching valve 33 includes a solenoid valve 32 and a switching valve 33. The switching valve 33 has a modulator pressure (described later) reduced in proportion to the line pressure, a control port a communicating with the solenoid valve 32, a supply port b supplying the modulator pressure, and a differential valve. It has a port c communicating with the hydraulic actuator 27 of the control device, and a drain port EX. Reference numeral 35 in the figure is a diaphragm having a hole of a predetermined diameter.

Next, the operation based on the above structure will be described.

The rotation of the engine is appropriately shifted by the automatic transmission and transmitted to the input gear mount case 2 via the input gear 1. During normal traveling, that is, when the driver puts the shift lever in the D range and selects the automatic mode, the solenoid valve 32 of the valve unit 31 is in the on state and the pressure at the control port a is drained. The switching valve 33 is in the lower half position in FIG. Of course, when the solenoid valve 32 is off, the pressure at the control port a may be set to drain.
In this state, the supply port b and the port c communicate with each other, and the modulator pressure reduced in proportion to the line pressure is the pipe 36.
Also, the wet multi-plate clutch 26 is in a connected state with a predetermined crimping force by acting on both pistons 28, 29 of the hydraulic actuator 27 via the oil passages 37, 38. Therefore, in the center differential device 18, the differential carrier 18c and the right side gear 18a are coupled with each other with a predetermined coupling force, and the differential thereof is limited by the predetermined regulation force. As a result, when the frictional force between the road surface and the tire is smaller than the regulation force, for example, on a road surface having a small friction coefficient such as a snow road or a dirt road, the center differential device is based on the pressure force of the clutch 26.
18 is almost directly connected, and the rotation of the input gear mount case 2 is transmitted to the differential case 3c of the front differential device 3 through the friction clutch 26 and the center differential device 18 that rotates integrally, and further the pinion.
Torque is distributed to the left and right sun gears 3a, 3b via 3p to drive the left and right front wheels, and also transmitted to the driven pinion shaft 20 via the ring gear 17 and the gear 21 fixed to the center differential device 18, and further to the rear differential device. The torque is distributed by the drive to drive the left and right rear wheels. Further, when the frictional force between the road surface and the tire is approximately balanced with the restriction force by the clutch 26, for example, when traveling on a paved road at a relatively high speed, in the relationship of the friction coefficient of the road surface, tire slip is The clutch 26 is crimped while sliding so that it does not occur. That is, the center differential device 18 has a torque distribution of 50: 5 to the front and rear wheels.
The torque is distributed to the front and rear wheels while absorbing the rotation difference between the front and rear wheels in a state of being urged to approach 0. Therefore, at this time, when there is a difference in diameter between the front and rear tires due to different tire pressures for the front and rear wheels, the modulator pressure is lower than the line pressure even when the throttle opening is high, and the friction is low. The slip of the clutch 26 absorbs the rotation difference between the front wheels and the rear wheels due to the difference in the diameter of the tire.

Also, when turning the steering angle greatly at low speed, such as when entering the garage,
Although there is a rotation difference between the front wheels and the rear wheels, in this case, the throttle opening is small, and therefore the modulator hydraulic pressure reduced in proportion to the line pressure is also low, so the pressing force by the hydraulic actuator 27 is also weak and the friction of the differential control device 10 is low. The engagement force of the clutch 26 is also weak. Therefore, the left and right side gears 18a of the center differential device 18 based on the rotation difference between the front wheels and the rear wheels,
In order to allow the relative rotation of 18b, the friction clutch 26 slips and transmits torque to the front and rear wheels while preventing the occurrence of the tight corner braking phenomenon.

Then, when traveling at a relatively high speed on a road where a sharp curve continuously follows a mountain road or the like, the driver can turn off the automatic mode according to his / her preference, but the driver can also drive in the on state. In this state, the modulator pressure is lower than the line pressure over the entire throttle opening, and the friction coefficient between the tire and the road surface is high because of the paved road,
The engagement force of the friction clutch 26 of the differential control device 10 is weak as compared with the resistance from the tire having the high friction coefficient. Therefore, in a tight corner where the rotation speeds of the front wheels and the rear wheels are different, the friction clutch 26 slips to prevent the occurrence of the tight corner braking phenomenon, while the center differential device 18 distributes the torque to the front and rear wheels by 50. Energize to approach: 50 and transmit power. Further, in the paved road where the sharp curves are continuous, the auto mode may be turned off. In this state, the solenoid valve 32 of the valve unit 31 is in the off state, a predetermined hydraulic pressure acts on the control port a of the switching valve 33, the valve 33 is switched to the upper half position, and the port c becomes the drain port EX. Communicate. Then, the supply of hydraulic pressure to the hydraulic actuator 27 of the differential control device 10 is cut off, and the friction clutch 26 is released. In this state, rotation of the mount case 2 is performed by the differential carrier 18 of the center differential device 18 via the sleeve portion 2b.
18c, and further branched and transmitted from the differential pinion to the left and right side gears 18a, 18b. And left side gear 1
The rotation of 8a is transmitted to the differential case 3c of the front differential device 3 through the sleeve portion 3c ₁ ', further branched and transmitted from the differential pinion 3p to the left and right side gears 3a and 3b, and transmitted to the left and right front axle shafts 8l and 8r, respectively. It On the other hand, the rotation of the right side gear 18b is transmitted to the gear mount case 16 that is spline-coupled to the gear, further transmitted to the driven pinion shaft 20 via the rear wheel drive ring gear 17 and the gear 21, and then to a propeller shaft (not shown). And transmitted to the left and right rear wheels via the rear differential device.

It should be noted that the solenoid valve 32 of the valve unit 31 is intermittently turned on / off in a high-speed driving state such as a fourth speed and a vehicle speed of 100 km / H in addition to the operation by the driver, and is controlled by a large number of valves. The friction of the plate clutch 26 is radiated.

Further, in the above-mentioned embodiment, the hydraulic pressure consisting of one path is supplied to the first oil chamber and the second oil chamber of the hydraulic actuator 27 consisting of the double piston, and it is used as a mere boosting mechanism. It may be configured to supply individually controlled hydraulic pressure to enable fine slip control.

Next, with reference to FIG. 3, an embodiment will be described in which the hydraulic actuator 27 of the differential control device 10 is supplied with modulator pressure obtained by relatively reducing the line pressure.

In the figure, 31 is a valve unit consisting of the solenoid valve 32 and the switching valve 33 shown in FIG. 2, only this part is provided in the transfer part, and each valve described below is installed in the valve body of the automatic transmission. To be done. Reference numeral 40 is a regulator valve for the differential control device. Further, 41 is a torque converter equipped with a lockup clutch 41a, 42 is a lockup relay valve, and 43 is a lockup signal valve. Reference numeral 45 is a hydraulic pump, 46 is a primary regulator valve, 47 is a secondary regulator valve, 49 is a throttle valve with a kick damper plug, 50 is a cutback valve, 51 is a detent regulator valve, and 52 is a throttle modulator valve. 55 is a manual valve, 56 is a 1-2 shift valve, 57 is a 2-3 shift valve, 59 is a 3-4 shift valve, 60 is a low coast modulator valve, 61 is a second coast modulator valve, and 62 is a 3-4. A switch valve, 63 is a solenoid valve for operating the switch valve, and 65 is a cabana valve. Furthermore, 66 is an accumulator control valve, 67 is a C1 accumulator, and 69 is
A B2 accumulator, 70 is a C2 accumulator, 71 is a C3 accumulator, and 72 is a B4 accumulator. And C1
Is the forward clutch, C2 is the direct clutch, and C3 is
O / D direct clutch, B1 is 2nd coast brake, B2
Shows the 2nd brake, B3 shows the 1st & Rev brake, and B4 shows the O / D brake hydraulic servos.

The differential control regulator valve 40 includes a line pressure port e, a throttle pressure port f, an L range line pressure port g, an R range line pressure port h, a feedback pressure port i, a pressure adjusting port j, and a drain port EX. Further, it comprises a pressure adjusting spool 40a and two plugs 40b, 40c having different cross-sectional areas from the spool.

Since the present embodiment is configured as described above, during normal traveling, that is, when the manual valve 55 is in the D range, the L range line pressure port g and the R range line pressure port h of the differential control device regulator valve 40 are used. Is not supplied with oil pressure. In this state, the regulator valve 40
Is supplied with the line pressure P _L from the primary regulator valve 46 to the line pressure port e, the throttle pressure from the throttle valve 52 to the throttle pressure port f, and the pressure adjusting port j to the feedback port i.
The pressure regulation from works. Therefore, the regulator valve 40
Is the first and second plugs 40b, 40 as shown in the right half position.
c is seated on the bottom surface, throttle pressure and spring urging force act on the lower surface of the pressure adjusting spool 40a, and the pressure adjustment is fed back to the upper surface of the pressure adjusting spool 40a to act as a balance between these two pressures. The line pressure P _L of the port e is reduced at a predetermined rate, and a reduced pressure (modulator pressure) proportional to the throttle pressure is supplied from the pressure adjusting port j to the switching valve 33 of the valve unit 31 described above.

Therefore, in this state, the hydraulic actuator 27 of the differential control device 10 is acted on by the hydraulic pressure C (see FIG. 4) which is reduced in proportion to the line pressure indicated by P _L (D) in FIG. The plate clutch 26 is connected with a weak crimping force. Therefore, the center differential device 18 by the differential control device 10
The differential regulation force of the vehicle, that is, the urging force that tries to bring the torque distribution to the front and rear wheels closer to 50:50, is reduced, and the rotation difference between the front and rear wheels is reliably absorbed, and the loss of fuel consumption due to slip between the tire and the road surface and It is possible to surely eliminate an increase in tire wear and a braking phenomenon at the time of tight corners.

Further, when one wheel is idling due to wheel removal or the like, the center differential device 18 may be differential due to the weak differential restriction force, making it impossible to escape. Therefore, in such a case, the manual valve 55 is operated to the L range or the R range.

When operated in the R range, the line pressure is supplied from the R port of the manual valve to the R range line pressure port h of the regulator valve 40. In this state, as shown in the left half position of the regulator valve 40, the line pressure acting on the lower surface of the plug 40c becomes the throttle pressure acting on the upper surface of the plug 40b and the feedback pressure (line pressure) acting on the upper surface of the spool 40a. When it is overcome, the pressure adjusting spool 40a is moved upward together with the plugs 40b and 40c, and the line pressure port e and the pressure adjusting port j are completely passed. Therefore, the high line pressure P _L (R) (see FIG. 4) in the R range from the primary regulator valve 46 is supplied to the port j via the switching valve 33 to the hydraulic actuator 27 of the differential control device 10. . As a result, the pressing force of the clutch 26 is increased, the differential restriction force of the center differential device 18 is increased, and the wheel can escape.

In addition, when stacking such as derailing and when a large climbing force is required, the manual valve 55 is put in the L range. Then, the line pressure from the L range port of the manual valve 55 changes to the L range line pressure port g of the regulator valve 40.
Is supplied to. In this state, the lower plug 40c is seated on the bottom surface and acts on the lower surface of the upper plug 40b.
The line pressure from the above overcomes the feedback pressure or the like acting on the upper surface of the spool 40a and moves the spool 40a upward together with the plug 40b so that the line pressure port e and the pressure adjusting port j are entirely passed.

On the other hand, in the L range, the manual valve 55
Line pressure is supplied from the L port to the port k of the second coast modulator valve 61 via the 2-3 shift valve 57. The spring of the modulator valve 57 is set so that the modulator pressure is high, and the modulator pressure from the port 1 of the valve is transmitted through the oil passage m and the check ball 75 to the port n of the primary regulator valve 46. Is supplied to. This allows
As shown in FIG. 4, when the throttle opening is low,
The line pressure by the primary regulator valve 46 is a substantially constant hydraulic pressure F irrespective of the throttle opening based on the higher modulator pressure from the second coast modulator valve 61, and the cutback pressure of the predetermined throttle opening x or more. The hydraulic pressure E'is based on the throttle pressure that does not act.

Therefore, from the pressure regulating port j of the regulator valve 40 via the switching valve 33, the hydraulic actuator of the differential control device
The boosted line pressure is supplied to 27, and the clutch 26 is engaged from a low opening throttle region with a substantially constant and relatively large pressure-bonding force.
18 is a large regulation force and differential is regulated.

In FIG. 4, G is the throttle pressure.

As described above, according to the embodiment of the present invention, during normal use of the vehicle, a predetermined hydraulic pressure (c) is supplied to the hydraulic actuator (27) of the differential control device (10) to cause the wet friction material clutch (26). ) Is connected with a predetermined crimping force, and torque is transmitted to the front and rear wheels while the center differential device (18) is biased so that the torque distribution to the front and rear wheels approaches a predetermined ratio. It is possible to drive the vehicle in an appropriate four-wheel drive state without requiring any operation, and it is possible to improve various performances such as the starting acceleration performance of the vehicle, the high-speed straight traveling performance, and the steerability. Further, the friction material clutch (26) only needs to regulate the differential of the center differential device (18), and has a large torque capacity to drive the rear wheels (or front wheels) like the conventional wet multi-disc clutch system. Therefore, it is possible to easily absorb the rotation difference between the front and rear wheels on a road surface having a high friction coefficient such as a paved road, and based on the small torque capacity, the hydraulic actuator (27) is operated when the throttle opening is low. Since the hydraulic pressure supplied to is reduced, the tight corner braking phenomenon can be reliably prevented. Further, it suffices to supply the hydraulic actuator (27) with a predetermined hydraulic pressure (C), which is a hydraulic pressure reduced in proportion to the line pressure, and it is not necessary to use an expensive and complicated electronic control device, and the cost can be reduced. it can.

Further, since the hydraulic pressure (line pressure) is reduced by the regulator valve (40) at a predetermined rate to the hydraulic actuator (27), the difference in rotation between the front and rear wheels is more reliably absorbed, which reduces fuel consumption and reduces tire tires earlier. It is possible to reliably prevent wear and the occurrence of a tire corner braking phenomenon.

[Brief description of drawings]

FIG. 1 is a sectional view showing a power transmission device for a four-wheel drive vehicle to which the present invention can be applied, and FIG. 2 is a hydraulic circuit diagram showing the valve unit thereof. Then, FIG. 3 is a diagram showing a hydraulic circuit according to the present invention, and FIG. 4 is a diagram showing changes in respective hydraulic pressures depending on the throttle opening. 10 …… Differential controller, 15 …… Transfer section, 26 ……
Wet friction multi-plate clutch, 27 …… hydraulic actuator, 31
...... Valve unit, 32 ...... Solenoid valve, 33 ......
Switching valve, 40 ...... second regulator valve (regulator valve for differential control device), 45 ... hydraulic pump,
46 …… First regulator valve (primary regulator valve), 55 …… Manual valve, C …… Predetermined hydraulic pressure, D …… Normal running range, P _L …… Line pressure, U …… 4
Power transmission device for wheel drive vehicle.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Fumitomo Yokoyama 10 Takane, Fujii-cho, Anjo City, Aichi Prefecture, within Ishin Warner Co., Ltd. (72) Inventor, Yasushi Nakamura 1 Toyota-cho, Toyota City, Aichi Prefecture Toyota Automobile Incorporated (72) Inventor Yuu Minamoto 1 Toyota-cho, Toyota-shi, Aichi Toyota Automobile Co., Ltd. (72) Inventor Kosei Akashi 1-cho, Toyota-cho, Aichi Toyota Automobile Co., Ltd. (72) Inventor KUBO Masanori 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (56) References JP 62-74713 (JP, A)

Claims (1)

[Claims] 1. An automatic transmission for changing a power transmission path to change gears by selectively supplying line pressure from a hydraulic control device,
A four-wheel drive vehicle including a center differential device that branches and transmits the driving force from the automatic transmission to the front wheel side and the rear wheel side, and a differential control device that controls the differential of the center differential device. In the power transmission device for a vehicle, the differential control device connects the wet friction material clutch and the wet friction material clutch with a predetermined crimping force by a predetermined hydraulic pressure from the hydraulic control device to connect the differential of the center differential device. And a hydraulic valve for limiting, wherein the hydraulic control device is switched to a plurality of traveling ranges including at least a normal traveling range by a driver's operation, and a manual valve for outputting a signal pressure according to the plurality of traveling ranges, A first regulator valve for adjusting the hydraulic pressure from a hydraulic pump and outputting it as the line pressure, and the first regulator valve The throttle opening is arranged between the rotary valve and the hydraulic actuator, and is increased according to the throttle opening when the signal pressure from the manual valve is input and the manual valve is switched to the normal traveling range. When the friction coefficient between the wheel and the traveling road surface is lower than the line pressure in all regions and the friction coefficient is low, the wet friction material clutch is engaged, and when the friction coefficient is high, the wet friction material clutch is engaged. And a second regulator valve for reducing the line pressure to a predetermined hydraulic pressure that brings the wet friction material clutch into a slip state and supplying the hydraulic pressure actuator with the predetermined line hydraulic pressure, the electric power transmitting apparatus for a four-wheel drive vehicle.