JPS62218231A - Four-wheel drive running gear - Google Patents

Abstract

PURPOSE:To make a vehicle drivable with maximum drive all the time in its driving state at that time, by increasing the transfer torque capacity of a differential limiting device limiting the differential action of a center differential gear according to an increase in input torque. CONSTITUTION:In this four-wheel drive vehicle, an automatic transmission 2 and a four wheel driving transfer unit 3 are connected to an output shaft of an internal combustion engine 1. The transfer unit 3 is provided with a differential control clutch 21 which selectively connects a planetary gear type center differential gear 10 and its sun gear 13 and a ring gear 14. The differential control clutch 21 is driven by a hydraulic servomechanism controlled by a hydraulic controller 22. In this case, the hydraulic controller 22 is controlled so as to increase the extent of transfer torque capacity according to an increase in the input torque. And, a variation to the input torque of the transfer torque capacity is made variable settable by a manual characteristic setter 50.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a four-wheel drive system used in vehicles such as automobiles, and more particularly to a full-time four-wheel drive system having a center differential.

Conventional technology As one of the four-wheel drive devices used in vehicles such as automatic vehicles, the Hinta Diff 7 performs differential operation between the rear wheels and front wheels.
A full-time four-wheel drive system having a differential control device and a differential limiting device that limits the M operation of the center deino/range cell device has already been proposed, and this type of four-wheel drive system! 73 device is disclosed in, for example, Japanese Utility Model Application No. 47-203, Japanese Patent Application Publication No. 50-147027 @, Japanese Patent Application Publication No. 59-206228.
This is shown in each publication of the issue.

In the above-mentioned four-wheel drive system, the differential operation of the center differential device avoids the occurrence of the tight course flake phenomenon due to the difference in the turning radius between the front wheels and the rear wheels when the vehicle turns, but on the other hand, If any one of the wheels slips and loses driving force,
A problem arises in that the driving force for all wheels is reduced due to the differential operation of the center differential system. For this reason, four-wheel drive systems that have a center differential device are equipped with a differential limiting device that limits the differential operation of the center differential device, and this differential limiting device is generally called a viscous coupling. A viscous fluid type coupling or a 111 friction engagement type clap is used.

Problems to be Solved by the Invention In a differential limiting device using a viscous fluid coupling, the differential Luri limiting effect is determined by the difference in rotational speed between the front wheels and the rear wheels, and the difference in rotational speed is reduced by the action of the viscous fluid coupling. When the torque is large, the transmission torque capacity is increased to increase the differential limiting effect, but the front wheels and rear wheels cannot be completely connected to each other. That is, the front wheels and rear wheels cannot be completely locked up. Viscous fluid type couplings can cause a state close to lock-up as their capacity increases, but as the number of people increases, the transmission torque increases even in areas where the rotational speed difference between the front and rear wheels is small. The capacity will be relatively large, which will result in an excessive differential limiting action, and the occurrence of tight corner braking will not be well avoided.On the contrary, if a viscous fluid type coupling with a small capacity is selected,
This avoids the tight corner braking phenomenon when the vehicle turns, but unless the tire slip suspension becomes considerably large and the difference in rotational speed between the four wheels and the rear wheels becomes too large, the necessary differential limiting effect in the event of tire slip cannot be achieved. Although it is possible to avoid a loss of driving force across the entire width of the vehicle, it is not possible to increase the driving force of the slipping tire. Further, in the case of a viscous fluid type coupling, its transmission torque capacity is highly dependent on temperature, and it is difficult to select and maintain an appropriate torque value under all usage conditions F.

In a differential A, II limiter using a friction engagement type clutch,
If this goes on and off between fully engaged and completely disengaged, the four-wheel drive state will suddenly change due to the switching, and it is difficult to judge the switching, especially with manual switching type, and it is difficult to judge whether the switching is appropriate in reality. difficult to use.

In view of the above-mentioned problems with conventional four-wheel drive systems, the present invention has been developed to appropriately distribute drive power between the front wheels and rear wheels to maximize the drive power as much as possible under the current driving condition. This allows the vehicle to run with driving force, and also avoids the loss of driving force across the entire width due to slipping and the occurrence of tight corner braking, and also allows the operating characteristics of the differential A+11 limiter to be adjusted to the driver's preference. The aim is to provide a four-wheel drive system that can be manually set according to the vehicle's requirements.

Means for Solving the Problems According to the present invention, the above-mentioned object includes one input member and two output members, one for the rear wheels and the other for the front wheels, and between the rear wheels and the front wheels. A center differential device that performs differential operation, and two members of an input member and two output members of the center differential device are connected to a base with variable transmission torque capacity to limit the differential operation of the center differential device. a differential limiting device that increases the transmission torque capacity of the differential limiting device in accordance with an increase in input torque; This is accomplished by a four-wheel drive system with a variable setting manual characteristic setter.

Effects and Effects of the Invention According to the configuration as described above, the transmission torque Furukawa of the differential limiting v device is increased in accordance with an increase in human torque, thereby increasing the drive torque between the front wheels and the rear wheels in accordance with the input torque. This ensures that the vehicle is driven with the maximum possible driving force under the current driving conditions, and that the vehicle is driven with the maximum possible driving force under the current driving conditions. It is possible to reduce the amount of slip of wheels that are already slipping without inducing slip in the other wheels, and even at the time of slipping, more driving force is transmitted to the road surface, and even at this time, all wheels are prevented from slipping. The vehicle now runs with the maximum possible driving force -6 within the range that does not cause bumps, and the degree of differential restriction of the center differential device is determined by the driver's preference or driver's judgment. This allows the driver to freely set the settings and obtain driving performance that more closely reflects the driver's preferences and intentions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail by way of embodiments with reference to the accompanying drawings.

FIG. 1 is a skeleton diagram showing a four-wheel drive system according to the present invention. In the figure, reference numeral 1 indicates an internal combustion engine, which is installed vertically at the front of the vehicle, and an automatic transmission 2 for the vehicle and a transfer device 3 for four-wheel drive are installed at the rear of the internal combustion engine. are connected in order.

The vehicular automatic transmission 2 includes a hydraulic type 1 to lux converter 5 of a general structure provided in a converter case 4 and a gear type transmission provided in a transmission case 6.
7, and is drivingly connected to an output shaft (crankshaft, not shown) of the internal combustion engine 1 by an input member 8 of the hydraulic torque converter 5 to transfer the rotational power of the interlayer 1 (internal combustion) through the hydraulic torque converter 5. The signal is applied to the transmission 7. The transmission 7 is a well-known transmission comprised of a planetary gear mechanism or the like, and is configured to shift between a plurality of gear stages, and is controlled by a hydraulic control device 9. .

The four-wheel drive transfer device 3 is a planetary gear type center differential device for full-time 4WD [10
The center differential device 10 has a carrier 11 as an input member capable of receiving rotational power from the transmission 7, a planetary pinion 12 supported on the gear rear, and a planetary pinion 12 that meshes with the planetary pinion 12. The ring gear 14 is connected to the rear wheel drive shaft 15, and the sun gear 13 is connected to the rear wheel drive shaft 15 and a sleeve-shaped front wheel drive intermediate shaft 1.
6. Four-wheel drive transfpg device 3
A front wheel drive shaft 17 is provided in parallel with the front wheel drive intermediate shaft 16, and the front wheel drive intermediate shaft 16 and the front wheel drive shaft 1
7 are drivingly connected by sprockets 18 mounted on each of them and an endless '7-I-ne 20 meshing with one of them.

The four-wheel drive transnor device 3 is provided with a hydraulically operated initial arrival control clutch 21 that selectively connects the sun gear 13 and the ring gear 14, and the operation of the differential control clutch is controlled by the four-wheel drive transfer control clutch. This can be done by a hydraulic control device 22 provided in the equipment d3.

The differential control clutch 21, as shown in FIG.
This is a hydraulic servo type wet multi-disc clutch, and the servo piston 37 is moved to the right in the figure against the spring force of the return spring 38 by the servo oil pressure supplied to the oil chamber 36 of the hydraulic servo device 35. The number gear 13 and ring gear 1 of the center differential device 10 are used for torque transmission.
4, and the transmission torque capacity is increased proportionally in accordance with an increase in the servo oil pressure supplied to the oil chamber 36.

The hydraulic control device 22 is provided with hydraulic pressure from an oil pump 39 incorporated in the vehicle automatic transmission l112, and regulates the hydraulic pressure to a predetermined hydraulic pressure.
and an electromagnetic servo hydraulic control 1-roll valve 41 to which hydraulic pressure is applied from a pressure regulator valve 40. The servo hydraulic control valve 41 is
It has a boat a connected to the oil chamber 36 of the hydraulic servo device 35, a hydraulic boat b supplied with hydraulic pressure from the regulator valve 40 of the brake lever 11, and a drain boat C. When energized, the boat 1-a is The hydraulic boat b is connected to the hydraulic boat b, while the boat a is connected to the drain boat C when the power is not energized. A pulse signal of a predetermined duty pressure is given to the servo hydraulic control valve 41 by the control device 45, and from this, the servo hydraulic control valve 41 applies servo hydraulic pressure of a magnitude according to the duty ratio to the oil chamber 36 of the hydraulic servo v4@35. will be supplied to

One end of a rear propeller shaft 24 is drivingly connected to the rear wheel drive shaft 15 through a universal joint 23 .

The bamboo wheel drive shaft 17 is connected to one end of a front wheel drive shaft 26 by a universal joint 25. The front differential 1 to the propeller shaft 26 extend approximately parallel to the axis on one side of the vehicle automatic transmission 2, and are connected to the front differential 7 by a universal joint 27 and an intermediate connecting shaft 28 at the other end. The drive pinion shaft 31 is connected to one end of a drive pinion shaft 31, which is an input shaft of the 11-channel device 30. The drive pinion shaft 31 is integrally formed with the cast iron oil pan 29 of the internal combustion engine 1.
It is rotatably supported by the primary case 32.

A drive pinion 33 made of a bevel gear is provided at the end of the drive pinion shaft 31, and the drive pinion meshes with a ring gear 34 of the front differential device fi30.

The hydraulic control devices 9 and 22 operate based on control signals from the electric control device 45 to control the gear change of the transmission 7 and the transmission torque of the differential control clutch 21. The control device 45 includes a microcomputer with a general structure, and receives information regarding the vehicle speed from the vehicle speed sensor 46, information regarding the throttle opening of the internal combustion engine 1 from the throttle opening sensor 47, and information regarding the manual shift from the manual shift position sensor 48. Information about the range, information about the input torque given to the four-wheel drive transfer device 3 by the input torque sensor 49, and information about the degree of manual characteristic setting from the manual characteristic setting device 50 are respectively given, and basically the manual shift range is given. (changes according to a predetermined shift pattern according to vehicle speed and thrower 1-hell opening) *Outputs a control signal for controlling the gear change of the device 7 to the hydraulic control device 9, and also outputs a control signal to the hydraulic control device 9, and also controls input torque and throttle opening. 1. Differential control ramp 2 according to the gear position of the transmission A7 and the degree of manual characteristic setting.
A pulse signal of a predetermined duty ratio for controlling the transmission torque capacity of the servo hydraulic controller 1-roll valve 41
It is designed to output to.

The transmission torque capacity ff1Tc of the differential control clutch 21 is controlled by transmission 1 to torque according to the degree of manual characteristic setting by the manual characteristic setting device 50, as shown by symbols A, B, and CSD in the graph of FIG. In order to set the capacity ff1Tc, a pulse signal with a predetermined duty ratio is output to the servo hydraulic control valve 41 so that Tc-kx-Ti (Ti: input torque, kx: manual characteristic setting coefficient). This is done by

As a result, the transmission torque capacity of the differential control clutch 21 is FC
increases with an increase in the input torque Ti at an increase rate determined by the degree of manual characteristic setting determined by the manual characteristic setting device 5o. In this example,
In FIG. 3, the transmission torque capacity characteristics are switched and set to four types of characteristics indicated by symbols A, B, C, and D.

The reason why vehicle tires do not slip is because the torque TO given to the tires is the torque T that the tires can transmit to the road surface.
−μ・Fn−R (where μ: coefficient of friction of the tire against the road surface, Fn: normal force of the tire, R: effective radius of tie ψ), that is, when To≦Tt
When TO>Tt, a slip occurs.

Therefore, in order to avoid slippage or reduce slippage, it is sufficient to reduce the torque TO applied to the tire.

In a four-wheel drive system that has a center differential device and a differential limiting device, the output torque 7r to the rear wheels and the output 1 to torque Tt to the front wheels are the unique front and rear wheels 1 to 1 of the center differential device. It is determined by the torque distribution ratio and the torque capacity of the differential limiting device, and in the four-wheel drive system according to the present invention, the transmission torque capacity 1firc of the differential control clutch 21, which is the differential limiting device, is variable. By specifically controlling this transmission torque capacity M'rc, the degree of distribution of the output torque between the rear wheels and the front wheels during slipping can be quantitatively and variably set.

That is, when the rear wheels are slipping, the torque Tr applied to the rear wheels and the torque T'' applied to the front wheels are expressed by the following formula.

1-r = (1/ (1+ρ)) Ti-TcT
f-(ρ/(1+ρ))Ti+TOFurthermore, when the front wheels are slipping, the torque king r given to the rear wheels and the torque d given to the front wheels are expressed by the following formula.

Tr = (1/ (1+, Q))Ti +TCTf
= (D/ (1+/)) ) Ti −Tc However, ρ
(Number of gear teeth of center differential device/
How many teeth does the ring gear have?

Therefore, in order to prevent the rear wheel C from slipping, the following formula should be established.

Tr=(1/<1+ρ)Il'i-Tc≦1'-tr
/ir,',Tc≧(1/(1+ρ))Ti−(
Ttr/ir)≧(1/ (1+ρ)1'ri-(Rr
・1"nr-Rr/ir) However, Ttr: Torque ir that the rear tires can transmit to the road surface
:Rear diff? Reduction ratio of range V 11r': Coefficient of friction of the rear tire against the road surface Fnr: Normal force Rr of the rear tire: Effective radius of the rear tire In Fig. 4, the thin line is 'T-c-(1/ (1+ρ))T
i −(Rr −Fnr−Rr /ir), μr=O
.

μr-0,2, Rr = 0.4, Rr = 0.6,
It is shown for each of μr-0, 8 and Rr=i.

In order to prevent the front wheels from slipping, the following equation should hold true.

Tf = (ρ/(1+ρ)) Ti −Tc≦Tf/
if, ゛, Tc≧(ρ/(1+C)>) Ti −(
'rtf/ir) ≧ (ρ/(1+ρ)) Ti-(μf・Fnf-Rf/if)
: Front diff? Renshall's reduction ratio μ [1110 coefficient F nf for the road surface of the two front tires
: Normal force of front tire [<[: Effective radius of front tire In Figure 4, the broken line is Tc = <ρ/(1+ρ))T
i −<Ilf ・Fnf−Rf /if>, μ[=
0.11f = 0.2.71 (= 0.4, Rr =
o, e, 11 (=.

, 8, μ[=1 is shown.

In the illustrated embodiment, the ring gear 14 of the center differential device 10 is connected to the rear wheel drive shaft 15, and the ring gear 14 of the center differential device 10 is connected to the rear wheel drive shaft 15.
is connected to the front wheel drive shaft 17, so (1/(1
+ρ))/(ρ/(1+ρ)) is approximately 7/3 to 6/4.

Therefore, the transmission torque capacity fitT of the differential control clutch 21
c is determined by the manual characteristic setter 50 in FIG.
When set as shown by symbol A, the differential control clutch 21 remains fully engaged at all times, and the center differential device 10 is always locked up and does not perform differential operation at all.

On the other hand, if the transmission torque capacity ff1Tc is set as indicated by the symbol B in FIG.

When driving on a road surface with a friction coefficient μr = 0.2 and the input torque Ti is less than the predetermined 1 dT Ti 2, even if the rear wheels slip, the center differential tear 10 maintains a substantial lock-up state and the front wheels The transmission torque capacity fttTc of the differential control clutch 21 at this time is smaller than the predetermined value C, and the transmission torque capacity is limited to the predetermined value TC3 or less. A drive torque corresponding to 11Tc is transferred from the rear wheels to the front wheels via the differential control clutch 21, thereby reducing the slip amount of the rear wheels and increasing the drive torque given to the front wheels.
If the front wheels do not slip at this time, the driving torque that effectively acts on the running of the vehicle increases.

Under the same conditions, when driving on a road surface with a friction coefficient μr = 0.4, the input torque ``i'' is equal to the predetermined value Ti5 (Ti
3>Tiz), even if the rear wheels slip, the center differential device 10 is effectively
The pulled-up state is maintained so that no rotational speed difference occurs between the front wheels and the rear wheels, and the transmission torque capacity Tc of the differential control clutch 21 at this time is a predetermined value of 11aTCa (TO4>
The drive torque corresponding to the IC transmission torque capacity TC, which is small and is limited to below this predetermined value TC4, is transferred from the rear wheels to the front wheels via the differential control clutch 21, thereby reducing the slip amount of the rear wheels. As the torque decreases, the driving torque applied to the front wheels increases, and in this case as well, if the front wheels do not slip at this time, the driving torque that effectively acts on the running of the vehicle increases.

Therefore, in this case, the drive torque transfer M between the front wheels and the rear wheels by the differential control clutch 21 during slipping is limited to a smaller value as the S friction coefficient μ of the road surface is smaller. This results in 1'! ! Under conditions where the coefficient of friction is small, excessive drive torque is not transferred from the wheel that is slipping to the wheel that is not slipping (this prevents the wheels that are not slipping from slipping. .

Furthermore, if the transmission torque capacity fftT-c is set as shown by symbol C or D, the differential operation range of the center differential device 10 is expanded.

Since the transmission torque capacity ff1Tc of the differential control clutch 21 is 0 when the input torque Ti is zero in any case, and when the throttle opening of the internal combustion engine 1 is below a predetermined value, the transmission torque Furukawa Tc is set to 0, that is, the differential control clutch 21 is set to a completely disengaged state, so that the center differential device VIt10 performs differential operation without any restriction. As a result, in many cases, when cornering is performed, the depression of the accelerator pedal is released or reduced, and accordingly, when cornering, the center differential device 10 effectively operates as a differential, and tight corner braking phenomenon may occur. Avoided.

Incidentally, the differential control device such as the differential control clutch 21 has the following characteristics: 1. In addition to connecting one output member of the center differential device with the variable transmission torque capacity 10 as in the above embodiment, one of the two output members of the center differential device and the input member are connected. , that is, carrier and variable transmission torque! There may be a connection with T I'7% (- may also be present, and in this case, the same effect as in the above embodiment can be obtained by 1[1).

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited thereto.
It will be apparent to those skilled in the art that various embodiments are possible within the scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a four-wheel drive device according to the present invention, FIG. 2 is a schematic configuration diagram showing a control system for a differential control clutch of the four-wheel drive device according to the present invention, and FIG.
The figure is a graph showing the control characteristics of the differential control clutch of the four-wheel drive system according to the present invention. 1...Internal combustion engine, 2...Automatic transmission for vehicles, 3...
- Four-wheel drive transfer device, 4... converter case, 5... hydraulic torque converter, 6... transmission casing, 7... transmission device, 8... input member. 9... Hydraulic control device, 10... Center differential device, 11... Carrier, 12... Planetary binion 913... Sun gear, 14... Ring gear, 15... Contact wheel drive shaft , 16... Front wheel drive intermediate shaft, 17... Front wheel drive shaft, 18.19... Sprocket, 20... Endless chain, 21... Differential control clutch, 22... Hydraulic control device , 23... Universal joint, 24... Rear propeller shaft, 25... Universal joint, 2
6...Front propeller shaft, 27...Universal joint, 2
9...Oil pan, 30...Front differential 1ffi, 31...Drive pinion shaft, 32
... Differential case, 33 ... Drive pinion, 34 ... Ring gear, 35 ... Hydraulic servo device, 36 ... Oil chamber, 37 ... Servo piston,
3...Oil pump, 40...Pressure regulator valve, 41...Servo hydraulic control valve, 45...Control device, 46...Vehicle speed sensor, 4
7...Throttle opening sensor, 48...Manual shift (-posi/1 sensor), 49...Input torque limiter, 50...Manual characteristic setting device patent applicant Toyota Motor Corporation Agent
Patent Attorney Masatake Akashi Figure 2 218a
h'flAaFigure 3

Claims (1)

[Claims] A center differential device that has one input member and two output members, one for rear wheels and one for front wheels, and performs differential operation between the rear wheels and the front wheels, and an input member and two outputs of the center differential device. a differential limiting device that connects two of the members with each other with variable transmission torque capacity to limit the differential operation of the center differential device; and increasing the transmission torque capacity of the differential limiting device to an input torque. A four-wheel drive device comprising: a control device that increases the transmission torque capacity according to the input torque; and a manual characteristic setting device that is manually operated and variably sets the rate of change of the transmission torque capacity with respect to the input torque.