JPH09323557A - Stand-by four wheel drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stand-by four wheel drive capable of transmitting torque to rear wheels in the case when variation of a revolution ratio exceeds a specified value without transmitting torque to the rear wheels in the case when the variation of the revolution ratio of front wheels and the rear wheels is lower than the specified value. SOLUTION: It is furnished with front wheels 11 connected to an engine 1, a front propeller shaft 12 and a rear propeller shaft 16 serially connected to the engine 1, rear wheels 40 connected to the rear propeller shaft 16 and a unidirectional clutch 14 and a viscous coupling 15 serially arranged on a connecting part of the front propeller shaft 12 and the rear propeller shaft 16. Additionally, rotational speed of the rear propeller shaft 16 in a steady travelling state of a vehicle is set higher than rotational speed of the front propeller shaft 12, and the unidirectional clutch 14 is engaged in the case when rotational speed of the front propeller shaft 12 exceeds rotational speed of the rear propeller shaft 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a two-wheel drive state when the vehicle is in a steady running state, and a four-wheel drive state automatically when the driving wheels slip on a bad road or an ice / snow road. The present invention relates to a configured standby four-wheel drive vehicle.

[0002]

2. Description of the Related Art A four-wheel drive vehicle has a two-wheel drive state which is maintained during steady running of the vehicle, and when the drive wheels slip on a bad road or a snowy road, the four-wheel drive system is automatically operated. There is a standby four-wheel drive system that is configured to transmit torque to a vehicle, and an example thereof is described in Japanese Patent Laid-Open No. 63-186043.

The four-wheel drive vehicle described in this publication includes an engine, a transmission, and a differential gear, and front wheels are connected to the differential gear via an axle. Further, a propeller shaft, a power transmission device, and a viscous coupling are sequentially connected in series to the differential device, and the rear wheel is connected to the viscous coupling via an axle.

The viscous coupling includes silicon oil and an inner plate and an outer plate which are relatively rotatable. The power transmission device is provided with a one-way clutch capable of transmitting torque only from the input shaft of the propeller shaft to the output shaft of the propeller shaft.

The torque output from the engine is transmitted to the front wheels through the transmission, the differential device and the axle to drive the vehicle. On the other hand, the viscous coupling does not operate in the steady running state of the vehicle. The torque is not transmitted to the wheels and the two-wheel drive state is maintained.

Further, when the front wheels slip while the vehicle is running, the inner plate and the outer plate of the viscous coupling rotate relative to each other, and the shearing force serves to limit the relative rotation, that is, the torque is generated. It is transmitted to the wheels and becomes a four-wheel drive state. Since the power transmission device of the four-wheel drive vehicle is provided with the one-way clutch, there is an advantage that the braking force for the front wheels is not transmitted to the rear wheels.

As described above, in a standby four-wheel drive vehicle having a structure in which the distribution ratio of the torque transmitted to the front wheels and the rear wheels is controlled using the viscous coupling, the viscosity of the silicone oil used for the viscous coupling causes The running performance of the vehicle is affected.

[0008]

By the way, when the four-wheel drive vehicle described in the above publication turns a corner, that is,
The tight corner braking phenomenon can be avoided by suppressing the torque transmitted to the rear wheels in a traveling state in which the difference in differential rotation speed between the front wheels and the rear wheels is small. This can be achieved by setting the viscosity of the silicone oil to a low value due to the characteristics of the viscous coupling described above.

On the other hand, when the front wheels slip while traveling on a bad road or a snowy road, the torque transmitted to the front wheels is suppressed, and the torque is transmitted to the rear wheels so that the four wheels are driven. Performance is improved. This can be achieved by setting the viscosity of the silicone oil of the viscous coupling to be high.

However, in the four-wheel drive vehicle described in the above publication, it is impossible to simultaneously set the viscosity of the silicone oil of the viscous coupling to both high and low,
It was difficult to achieve both the avoidance of the tight corner braking phenomenon and the securement of sufficient transmission torque in a traveling state in which the differential rotation speed between the front wheels and the rear wheels is large.

In order to deal with this situation, by setting the outer diameters of the inner plate and the outer plate of the viscous coupling to be large or by increasing the number of the inner plates and the outer plates, it is possible to reduce the running speed when the differential rotation speed is large. It is possible to secure sufficient transmission torque, but this is not practical because the entire viscous coupling becomes large and the vehicle mountability deteriorates, and the manufacturing cost increases.

The present invention has been made in view of the above circumstances. When the amount of change in the rotational speed ratio between the first drive wheel and the second drive wheel is less than or equal to a predetermined value, more specifically, the first drive wheel is Second
If the rotation speed difference with the drive wheels is less than or equal to a predetermined value, torque is not transmitted to the second drive wheels, and the change amount of the rotation speed ratio between the first drive wheel and the second drive wheel exceeds the predetermined value. In this case, more specifically, a standby four-wheel drive vehicle that can transmit torque to the second drive wheel when the rotational speed difference between the first drive wheel and the second drive wheel exceeds a predetermined value. The purpose is to do.

[0013]

In order to achieve the above object, the present invention is directed to a first driving source connected to a driving force source.
A driving wheel, a first torque transmitting member connected to the driving force source, a second torque transmitting member connected to the first torque transmitting member, and a second torque transmitting member connected to the second torque transmitting member.
A standby four-wheel drive vehicle including: a drive wheel; and a one-way clutch and a viscous coupling, which are arranged at a connecting portion between the first torque transmitting member and the second torque transmitting member and are connected in series with each other, Means is provided for setting the rotation speed of the second torque transmission member to be higher than the rotation speed of the first torque transmission member in a steady traveling state of the vehicle, and the one-way clutch is configured to operate the first torque transmission member. It is characterized in that it is engaged when the rotation speed exceeds the rotation speed of the second torque transmission member.

In the present invention, the steady running state of the vehicle means that the braking force of the braking device provided on the vehicle is the first driving wheel and the second driving wheel.
The first drive wheel and the second drive wheel do not act on the drive wheel.
The driving state in which the drive wheels do not slip.

According to the present invention, the output torque of the driving force source is transmitted to the first drive wheels to drive the vehicle, and in the steady running state of the vehicle, the rotational speed ratio between the first drive wheels and the second drive wheels is increased. Since the rotation speed of the second torque transmission member is set to be constant and faster than the rotation speed of the first torque transmission member, the one-way clutch is released, the viscous coupling does not generate torque, and the two-wheel drive state is set. Become.

Even when the rotation speed ratio between the first drive wheel and the second drive wheel changes while the vehicle is traveling, if the change amount of the rotation speed ratio is smaller than a predetermined value, specifically, In a traveling state in which the rotation speed of the first torque transmission member is equal to or lower than the rotation speed of the second torque transmission member, the one-way clutch is maintained in the released state. Therefore, even if a small change in the rotational speed ratio occurs between the first drive wheel and the second drive wheel when the vehicle turns a corner, torque is not transmitted to the second drive wheel, and the tight corner braking phenomenon is prevented. it can.

On the other hand, when the vehicle travels on a bad road, a snowy road, or the like, and the first drive wheels slip and a large change in the rotational speed ratio between the first drive wheel and the second drive wheel exceeds a predetermined value. Specifically, when the rotation speed of the first torque transmission member exceeds the rotation speed of the second torque transmission member, the one-way clutch is engaged. As a result, the viscous coupling first
Torque is generated according to the difference in rotational speed between the torque transmission member and the second torque transmission member, and sufficient torque is transmitted to the second drive wheels to bring the vehicle into a four-wheel drive state, improving the running performance of the vehicle.

Further, according to the present invention, by setting the rotational speeds of the first torque transmitting member and the second torque transmitting member and setting the engaging direction of the one-way clutch, sufficient torque to be transmitted to the second drive wheels can be obtained. Since the structure is ensured, a general-purpose viscous coupling can be used as it is, and it is possible to prevent a decrease in vehicle mountability and an increase in manufacturing cost due to an increase in size of the viscous coupling.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an FF to which the present invention is applied.
(Front engine front drive) It is a plan view showing a schematic configuration of a vehicle-based standby four-wheel drive vehicle. FIG.
In, the engine 1 is mounted on the front part of the vehicle. As the engine 1, for example, an internal combustion engine such as a gasoline engine, a diesel engine or an LPG engine is used. The transmission 2 is connected to the output side of the engine 1. As the transmission 2, for example, a selection gear type transmission, a planetary gear type transmission, an automatic transmission or the like is used.

A front differential 3 is connected to the output side of the transmission 2. The front differential 3 includes a front differential case 4, and the front differential case 4 is formed with a ring gear 5 and a transfer drive gear 6. Also, front differential case 4
Pinion gear 8 supported by pinion pin 7 inside
The front drive shaft 10 is connected to the side gear 9 meshed with the pinion gear 8, and the front wheel 11 as the first drive wheel is attached to the end portion of the front drive shaft 10.

On the other hand, behind the front differential 3, a front propeller shaft 12 as a first torque transmitting member is arranged in the front-rear direction of the vehicle, and a transfer driven gear 13 formed at the tip of the front propeller shaft 12 is transferred. It is meshed with the drive gear 6. A one-way clutch 14 and a viscous coupling 15 are connected in series behind the front propeller shaft 12, and behind the viscous coupling 15 there is a first torque transmission member arranged in the front-rear direction of the vehicle. The rear propeller shaft 16 is connected.

FIG. 2 is an enlarged sectional view showing the structures of the one-way clutch 14 and the viscous coupling 15, and the one-way clutch 14 and the viscous coupling 15 are integrally assembled. Reference numeral 17 denotes a flange yoke provided at the rear end of the front propeller shaft 12, and a flange 18 is formed at the rear portion of the flange yoke 17. The one-way clutch 14 includes an outer race 19 and
An inner race 20 arranged inside the outer race 19 and a plurality of engagement bodies 21 arranged in the circumferential direction between the outer race 19 and the inner race 20 are provided, and the outer race 19 and the flange 18 are provided. But screw 2
It is fastened and fixed by 2.

A flange 23 is formed on the outer periphery of the rear end of the inner race 20. The one-way clutch 14 is configured such that when the rotation speed of the front propeller shaft 12 exceeds the rotation speed of the rear propeller shaft 16, the plurality of engaging bodies 21 are engaged with the outer race 19 and the inner race 20 and the outer race 19 is engaged. The torque is transmitted to the inner race 20.

The viscous coupling 15 has a cylindrical case 24 fixed to the outer periphery of the flange 23, and a cylindrical hub 25 spline-fitted to the tip of the rear propeller shaft 16. One end of 25 is inserted so as to be rotatable relative to the inner circumference of the inner race 20. An annular cover 26 having an L-shaped cross section is fixed to the rear end of the case 24.
The other end is inserted into the cover 26 so as to be rotatable relative to the inner circumference of the cover 26.

The above-mentioned flange 23, case 24, hub 2
5, the annular oil chamber 27 formed by the cover 26 is filled with silicone oil (not shown). further,
A plurality of ring-shaped outer plates 28 are spline-fitted to the inner circumference of the case 24, while a plurality of ring-shaped inner plates 29 are spline-fitted to the outer circumference of the hub 25. And are arranged alternately. A seal ring 30 is attached to the inner circumference of the inner race 20, and a seal ring 31 is attached to the inner circumference of the cover 26. The seal rings 30, 31 maintain the hermeticity of the oil chamber 27. .

On the other hand, a drive pinion gear 32 is formed at the rear end of the rear propeller shaft 16, and the rear end of the rear propeller shaft 16 is connected to the rear differential 33. The rear differential 33 includes a differential case 34, and the differential case 34 includes a ring gear 35 meshed with the drive pinion gear 32.
And a pinion gear 37 supported by a pinion pin 36 is provided inside the differential case 34. Further, the side gear 3 is attached to the pinion gear 37.
8 are meshed with each other, and a rear wheel 40 serving as a second drive wheel is attached to the side gear 38 via a rear drive shaft 39.
Are connected.

In this embodiment, the outer diameter of the front wheel 11 and the outer diameter of the rear wheel 40 are set to be substantially the same, while the gear ratio between the front differential 3 and the rear differential 33 is the value of the front differential 3. The value of the rear differential 33 is set to be larger than that of the rear differential 33.

Next, the operation of the standby four-wheel drive vehicle having the above structure will be described. First, the torque output from the engine 1 is transmitted to the front wheels 11 via the transmission 2, the differential device 3, and the front drive shaft 10, and the vehicle is driven by the driving force of the front wheels 11. The steady running state of the vehicle, that is,
In a traveling state in which the braking force of the braking device provided on the vehicle side does not act on the front wheels 11 and the rear wheels 40, and the front wheels 11 and the rear wheels 40 do not slip, the front wheels 11 and the rear wheels 40
And the rotational speed ratio is 1: 1, and the rotational speed of the rear propeller shaft 16 is set higher than the rotational speed of the front propeller shaft 12.

This is based on the outer diameters of the front wheels 11 and the rear wheels 40 and the setting of the gear ratios of the front differential 3 and the rear differential 33. As a result, the one-way clutch 14 is disengaged, the viscous coupling 15 does not operate, and the two-wheel drive mode is set.

When the vehicle turns a corner, the front wheels 1
When there is a change in the rotational speed ratio between the rear wheel 40 and the rear wheel 40, that is, when differential rotation occurs due to the difference in moving radius, the rotational speed of the front propeller shaft 12 and the rotational speed of the rear propeller shaft 16 are However, the one-way clutch 14 is maintained in the released state until the rotational speeds of the front propeller shaft 12 and the rear propeller shaft 16 become substantially the same. Therefore, torque is not transmitted to the rear wheels 40, the two-wheel drive state is maintained, and the tight corner braking phenomenon can be prevented.

On the other hand, when the vehicle travels on a bad road or a snowy road and the front wheels 11 slip and the differential rotation speed between the front wheels 11 and the rear wheels 40 exceeds a predetermined value, specifically, the front propeller shaft. When the rotational speed of 12 exceeds the rotational speed of the rear propeller shaft 16, the one-way clutch 14 is engaged and the torque of the front propeller shaft 12 is transmitted through the inner race 20 to the case 24 of the viscous coupling 15. Be transmitted to.

Then, a shearing force is generated in the silicon oil according to the difference in the number of rotations of the outer plate 28 and the inner plate 29, and the torque of the inner plate 29 rotated by the shearing force causes the rear propeller shaft 16, the rear differential 33, and the rear differential 33 to rotate. It is transmitted to the rear wheels 40 via the drive shaft 39, and the four-wheel drive state is set. Therefore, when the differential rotation speed between the front wheels 11 and the rear wheels 40 exceeds a predetermined value, sufficient torque can be transmitted to the rear wheels 40, and the running performance of the vehicle is improved. In this embodiment, by changing the gear ratio between the front differential 3 and the rear differential 33, the differential rotation speed at which torque transmission is started to the rear wheels 40 can be set arbitrarily.

FIG. 3 is a diagram comparing the running performance of the standby four-wheel drive vehicle according to the above embodiment with the running performance of the standby four-wheel drive vehicle according to the comparative example. The viscosity of the silicone oil of the viscous coupling used in the examples and comparative examples is set to be the same.

As shown in FIG. 3, in the comparative example, when a small differential rotation occurs between the front wheels and the rear wheels, the viscous coupling operates and torque is transmitted to the rear wheels, so that a tight corner braking phenomenon occurs. Is likely to occur. In order to avoid this tight corner braking phenomenon, it is possible to set the viscosity of the silicone oil in the viscous coupling to a low value to suppress the torque transmitted to the rear wheels. The performance is reduced, and the torque transmitted to the rear wheels becomes insufficient in a traveling state in which the differential rotation speed between the front wheels and the rear wheels is large, resulting in poor traction.

On the other hand, according to the embodiment, when the differential rotation speed between the front wheels and the rear wheels is less than the predetermined value, the region where the torque is not transmitted to the rear wheels, in other words, the dead zone region is set. , It is possible to prevent the tight corner braking phenomenon when the vehicle turns a corner. In addition, if the vehicle runs on a bad road or a snowy road and the front wheels slip and the differential rotation speed between the front wheels and the rear wheels exceeds a predetermined value, the viscous coupling will operate. As a result, sufficient torque is transmitted to the rear wheels, the torque distribution ratio between the front and rear wheels is appropriately controlled, and good traction is maintained.

According to this embodiment, the silicone oil of the viscous coupling 15 is improved for the purpose of improving the torque transmission capability in a traveling state in which the differential rotation speed between the front wheels and the rear wheels becomes a predetermined value or more. Even if you increase the viscosity of
Since the torque is not transmitted to the rear wheels in the dead zone region where the differential rotation speed between the front wheels and the rear wheels is equal to or lower than the predetermined value, the tight corner braking phenomenon can be easily avoided.

Further, in the above embodiment, sufficient torque is transmitted to the rear wheels 40 based on the setting of the rotational speeds of the front propeller shaft 12 and the rear propeller shaft 16 and the setting of the engaging direction of the one-way clutch 14. It is configured to be. Therefore, the viscous coupling 15
A general-purpose structure can be used as it is, and it is possible to prevent a decrease in vehicle mountability and an increase in manufacturing cost due to an increase in size of the viscous coupling 15.

Further, in the above embodiment, the one-way clutch 14 is provided at the connecting portion between the front propeller shaft 12 and the rear propeller shaft 16, so that the four-wheel drive vehicle has an anti-lock brake system (hereinafter referred to as AB).
(Abbreviated as S), the braking force of the braking device acts on the front wheels 11 and the front propeller shaft 12
Even when the rotation speed of the vehicle is slower than that in the steady running state of the vehicle, the released state of the one-way clutch 14 is maintained and the torque is not transmitted to the rear wheels 40, which impairs the ABS function. There is no.

FIG. 4 is a sectional view showing another example of mounting the one-way clutch 14 and the viscous coupling 15. In this embodiment, the one-way clutch 14 and the viscous coupling 15 are directly attached to the differential carrier 41 of the rear differential 33.

That is, the differential carrier 41
A flange 42 is provided on the front part of the
A cylindrical front cover 43 is fixed in front of 2 by screws 44. The inner race 20 and the viscous coupling 15 of the one-way clutch 14 are arranged inside the front cover 43.
Are rotatably held by bearings 45 provided on the inner circumference of the front cover 43. Further, the cover 26 is rotatably held by a bearing 46 provided on the inner circumference of the front cover 42.

A rear propeller shaft 47 is spline-fitted to the inner periphery of the hub 25 of the viscous coupling 15, and a drive pinion gear 48 is formed at the rear end of the rear propeller shaft 47. The drive pinion gear 48 is the ring gear 35 of the rear differential 33.
Are engaged. Further, the rear propeller shaft 47 is held by bearings 49 and 50 provided inside the differential carrier 41. The other structure is the same as that of the embodiment shown in FIGS.

According to the embodiment of FIG. 4, since the one-way clutch 14 and the viscous coupling 15 are integrally attached to the rear differential 33 side, the holding force for the one-way clutch 14 and the viscous coupling 15 is increased. Therefore, the vibration of the one-way clutch 14 and the viscous coupling 15 and the abnormal noise due to the vibration can be suppressed.

The present invention can be applied to a standby four-wheel drive vehicle having a front propeller shaft fitted with a viscous coupling and a rear propeller shaft fitted with a one-way clutch. To be Further, by setting the outer diameter of the front wheels larger than the outer diameter of the rear wheels, it is possible to set the rotational speeds of the front propeller shaft and the rear propeller shaft in the steady running state of the vehicle.

As described above, when the outer diameters of the front wheels and the rear wheels are set, a predetermined differential rotation occurs between the front wheels and the rear wheels in the steady running state of the vehicle, and the rotation speed ratio between the front wheels and the rear wheels. When the amount of change in the above exceeds a predetermined value, the rotation speed of the front propeller shaft exceeds the rotation speed of the rear propeller shaft, and sufficient torque is transmitted to the rear wheels, and the same effect as that of the above embodiment can be obtained. Furthermore, the present invention can be applied to a four-wheel drive vehicle in which a midship type or a rear engine type is adopted as the powertrain arrangement.

[0045]

As described above, according to the present invention, the output torque of the driving force source is transmitted to the first drive wheels to drive the vehicle, and the first drive wheels and the second drive wheels are operated in the steady running state of the vehicle. And the rotational speed ratio of the second torque transmission member is set to be higher than the rotational speed of the first torque transmission member, the one-way clutch is released and the viscous coupling generates torque. Without it, it becomes a two-wheel drive state.

Even when the rotation speed ratio between the first drive wheel and the second drive wheel changes while the vehicle is running, if the change amount of the rotation speed ratio is smaller than a predetermined value, specifically, In a traveling state in which the rotation speed of the first torque transmission member is equal to or lower than the rotation speed of the second torque transmission member, the one-way clutch is maintained in the released state. Therefore, even if a small change in the rotational speed ratio occurs between the first drive wheel and the second drive wheel when the vehicle turns a corner, torque is not transmitted to the second drive wheel, and the tight corner braking phenomenon is prevented. it can.

On the other hand, when the vehicle travels on a bad road, a snowy road, etc., and the first drive wheels slip, and the first drive wheel and the second drive wheel have a large change in rotational speed ratio exceeding a predetermined value. Specifically, when the rotation speed of the first torque transmission member exceeds the rotation speed of the second torque transmission member, the one-way clutch is engaged. As a result, the viscous coupling first
Torque is generated according to the difference in rotational speed between the torque transmission member and the second torque transmission member, and sufficient torque is transmitted to the second drive wheels to bring the vehicle into a four-wheel drive state, improving the running performance of the vehicle.

Further, according to the present invention, by setting the rotational speeds of the first torque transmitting member and the second torque transmitting member and setting the engaging direction of the one-way clutch, sufficient torque to be transmitted to the second drive wheels can be obtained. Since the structure is ensured, a general-purpose viscous coupling can be used as it is, and it is possible to prevent a decrease in vehicle mountability and an increase in manufacturing cost due to an increase in size of the viscous coupling.

[Brief description of drawings]

FIG. 1 is a plan view showing a schematic configuration of an FF-based standby four-wheel drive vehicle to which the present invention is applied.

FIG. 2 is an enlarged sectional view showing the configurations of a one-way clutch and a viscous coupling used in the embodiment of FIG.

FIG. 3 shows the running performance of a four-wheel drive vehicle according to an embodiment of the present invention,
It is a diagram comparing the running performance of a four-wheel drive vehicle according to a comparative example.

FIG. 4 is an enlarged sectional view showing another example of attachment of the one-way clutch and the viscous coupling used in the present invention.

[Explanation of symbols]

1 Engine (Drive Power Source) 11 Front Wheel (First Drive Wheel) 12 Front Propeller Shaft (First Torque Transmission Member) 14 One-Way Clutch 15 Viscous Coupling 16 Rear Propeller Shaft (Second Torque Transmission Member) 40 Rear Wheel (No. 1) 2 drive wheels)

Claims (1)

[Claims] 1. A first driving wheel connected to a driving force source, a first torque transmitting member connected to the driving force source, and a second torque transmitting member connected to the first torque transmitting member.
A second drive wheel connected to the second torque transmission member and a one-way clutch and a viscous cup which are arranged at a connection portion between the first torque transmission member and the second torque transmission member and which are connected in series with each other. A standby four-wheel drive vehicle including a ring, means for setting the rotational speed of the second torque transmission member to be faster than the rotational speed of the first torque transmission member in a steady traveling state of the vehicle, and The standby four-wheel drive vehicle, wherein the one-way clutch is configured to be engaged when the rotation speed of the first torque transmission member exceeds the rotation speed of the second torque transmission member.