JPH0825400B2 - Vehicle differential gear - Google Patents

Description

TECHNICAL FIELD The present invention relates to a differential device for a vehicle.

(Prior Art) Conventionally, in a four-wheel drive vehicle, a differential mechanism (commonly called center differential) that absorbs a rotation difference between the front wheels and the rear wheels and a viscous resistance of fluid are included in a transfer that distributes power to the front wheels and the rear wheels. It is known that a viscous coupling for transmitting power is provided by utilizing the differential mechanism of the differential mechanism by the viscous coupling (for example, US Pat.
(See Japanese Patent No. 31780).

By the way, the viscous coupling, like public knowledge,
A disc-shaped outer plate is attached to the inner peripheral surface thereof at an appropriate pitch, and a rotary shaft having a disc-shaped inner plate attached to the outer peripheral surface thereof at an appropriate pitch is fitted so as to be relatively rotatable. When each outer plate and each inner plate are closely opposed to each other, and a viscous fluid of high viscosity (for example, silicone oil) is enclosed in the casing, and a rotation difference occurs between the casing and the rotating shaft. Power is transmitted by viscous resistance of the viscous fluid.

In such a viscous coupling, power is transmitted by utilizing the viscous resistance of the viscous fluid at the time of friction between the plate and the viscous fluid as described above. It is expected that the viscous fluid becomes hot and thermally expands, and in some cases, the plates come into contact with each other and the viscous coupling does not perform its function (this phenomenon is called a hump phenomenon).

Therefore, when the viscous coupling does not function effectively as the differential limiting device of the differential mechanism, from the viewpoint of protecting the viscous coupling,
The casing of the viscous coupling is fixed to the rotating shaft, their mutual rotation is restricted, and the differential mechanism is locked to directly connect the front wheels and the rear wheels to the engine side,
It is desirable to perform four-wheel drive traveling without a differential limiting action, that is, direct-coupled four-wheel drive traveling.

From this, in the known example, a multi-plate friction type clutch is provided in parallel with the viscous coupling for the differential mechanism, and when the viscous coupling reaches a high temperature, the heat of the viscous coupling is increased. The expansion force is used to operate the piston, and the piston pressing force engages the clutch to freeze the operation of the viscous coupling to protect it.

However, in this known example, as described above, the viscous coupling and the clutch are connected so as to be interlockable via the piston, and the occurrence of a state in which the viscous coupling needs to be frozen operation is mechanically detected. Therefore, the assembly including the viscous coupling, the piston, and the clutch must be handled as one unit, and the viscous coupling and the clutch are inevitably dedicated, which may cause a cost increase.

Also, when comparing the viscous coupling with the clutch, the viscous coupling has a short history and the performance tends to vary due to its processing technology.
The clutch has high reliability because its processing technology and its control system have already been established. For this reason, it is not a good idea in terms of performance and reliability to unitize these two parts having different performance and reliability into one unit, and there is room for improvement in this respect.

(Object of the Invention) The present invention is intended to solve the problems pointed out in the above-mentioned prior art, and is a simple and inexpensive vehicle differential device in which the differential limitation of the differential mechanism is performed by viscous coupling. The purpose is to prevent the hump phenomenon of viscous coupling with such a structure.

(Means for Achieving the Object) As means for achieving the above object, the present invention comprises an input member to which a driving force is input from the engine side, a first output member, and a second output member. A differential mechanism that performs a differential differential between the first output member and the second output member, and a viscous coupling that performs power transmission using the viscosity of the fluid when a rotation difference occurs between the two shafts. A differential device for a vehicle, which is provided with the viscous coupling so as to restrict the relative rotation of the first output member and the second output member of the differential mechanism to limit the differential action of the differential mechanism. When the rotational difference of a predetermined level or more between the first output member and the second output member of the differential mechanism continues for a set time or more, It is provided with detecting means for detecting this, and differential blocking means for receiving a signal from the detecting means and blocking relative rotation between the first output member and the second output member.

(Operation) According to the present invention, by the above means, when the speed difference of the predetermined level or more continues between the first output member and the second output member of the differential mechanism for the set time or more, that is, the hump phenomenon in the viscous coupling. Occurs and it is considered that the differential limiting action of the differential mechanism is not effectively performed, the detecting means detects this and the differential blocking means operates in response to the signal from the detecting means.
The relative rotation of the output member and the second output member is prevented, and the viscous coupling is protected.

(Embodiment) A preferred embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 shows a transfer Z portion of a four-wheel drive vehicle equipped with a differential device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a main transmission. A planetary differential mechanism 3 is attached to one end of an output shaft 2 of the main transmission 1.

The differential mechanism 3 includes a ring gear 4 connected to a rear wheel drive shaft 16 via a first rotary shaft 21 and a second rotary shaft 22 fitted so as to be rotatable relative to the output shaft 2.
And a pinion gear 6 that meshes with the ring gear 4 and the sun gear 5, respectively, and is connected to the output shaft 2 via a carrier 7. still,
In this embodiment, the first rotary shaft 21 corresponds to the first output member in the claims, the second rotary shaft 22 corresponds to the second output member, and the output shaft 2 is input. It corresponds to a member.

Reference numeral 10 is an outer plate provided on the casing 25 side.
A well-known structure having an outer plate 26 and an inner plate 27 provided on a rotary shaft 28 that is relatively rotatably fitted in the outer casing 25, and in which a viscous fluid (for example, silicon oil) is enclosed in the casing 25. A viscous coupling of the above-mentioned casing 25 of this viscous coupling 10.
Is the first rotary shaft 21 and the rotary shaft 28 is the second rotary shaft 21.
Are respectively coupled to the rotating shafts 22 of. Therefore, when a speed difference occurs between the first rotary shaft 21 and the second rotary shaft 22, the power is transmitted between the first rotary shaft 21 and the second rotary shaft 22 via the viscous coupling 10. Is performed.

Further, between the first rotary shaft 21 and the second rotary shaft 22,
A first hydraulically actuated clutch 11 for selectively connecting or disconnecting the two is provided. Therefore, when the first clutch 11 is engaged, the first rotating shaft 21 and the second rotating shaft 21
Is integrated with the rotary shaft 22 of
10 is locked, and in the released state of the first clutch 11, the first rotary shaft 21 and the second rotary shaft 22 are relatively rotatable, and the viscous coupling 10 is activated.

A third rotary shaft 23 provided with a first transmission gear 13 is fitted on the output shaft 2 coaxially with the second rotary shaft 22 so as to be relatively rotatable. The first transmission gear 13 is chain-connected to the second transmission gear 14 provided on the front wheel drive shaft 15.

Further, between the third rotary shaft 23 and the first rotary shaft 21, there is provided a hydraulically actuated second clutch 12 for selectively connecting or disconnecting the both. Therefore, in the engaged state of the second clutch 12, the third rotating shaft
Power is transmitted from the differential mechanism 3 side via the 23 and the first rotary shaft 21, and the front wheel drive shaft 15 is rotated.

In FIG. 1, reference numerals 17 and 18 respectively denote the first rotary shaft 21 and the third rotary shaft 23 (that is, the second rotary shaft 22).
Is a rotation speed sensor that detects the rotation speed of the
N ₁ and N ₂ are input to the controller 40, respectively.

Reference numeral 31 is a first control valve that controls the supply of hydraulic oil to the first clutch 11, and opens and closes the first electromagnetic on-off valve 33 based on a control signal from the controller 40 to cause oil to open. A pressure port 54A and a drain port, which control the inflow of hydraulic oil into the chamber 53, connect the supply oil passage 55 that communicates with the oil chamber (not shown) of the first clutch 1 by using the spool 51 to the hydraulic pump 36. By selectively communicating with 54B, the first clutch 11 can be engaged or disengaged (the state of FIG. 1 shows the engaged state of the first clutch 11). . Further, reference numeral 32 is the second control valve 32,
The second control valve 32 controls the supply of hydraulic oil to the second clutch 12 to engage or disengage the second clutch 12, and by opening and closing the second electromagnetic on-off valve 34. It is activated. Since the structure of the second control valve 32 is the same as that of the first control valve 31, the description thereof will be omitted.

The four-wheel drive vehicle including the transfer Z configured as described above can obtain three traveling modes by selectively operating the first clutch 11 and the second clutch 12. That is, as shown in FIG. 2, while the first control valve 31 is turned on and the first clutch 11 is engaged,
When the second control valve 32 is turned off and the second clutch 12 is released, the first rotary shaft 21 and the second rotary shaft 22 are integrated and the viscous coupling 10 and the differential mechanism 3 are locked. The second rotary shaft 22 and the third rotary shaft 23 are separated from each other, so that rear-wheel drive two-wheel traveling (hereinafter, abbreviated as 2WD) is realized (travel mode).

In addition, the first control valve 31 is turned off and the first clutch 11
When the second control valve 32 is turned on and the second clutch 12 is engaged while the second control valve 32 is turned on, both the viscous coupling 10 and the differential mechanism 3 are activated and the second rotary shaft 22 and the third rotary shaft 23 is connected, and normal four-wheel drive traveling (hereinafter, abbreviated as normal 4WD for convenience of description) in which differential limitation of the differential mechanism 3 is performed by the viscous coupling 10 is realized (travel mode).

Further, both the first control valve 31 and the second control valve 32 are turned on.
When the first clutch 11 and the second clutch 12 are both engaged, the differential mechanism 3 and the viscous coupling 10 are locked together, and at the same time, the second rotary shaft 22 and the third rotary shaft 23 are coupled. Thus, four-wheel drive traveling in a direct connection state (hereinafter, abbreviated as direct connection 4WD for convenience of description) is realized (travel mode).

This mode selection is performed by selectively turning on the three mode switches 41, 42 and 43 shown in FIG.
The currently selected running mode is displayed by the mode indicators 44, 45, 46 corresponding to the mode switches 41, 42, 43.

By the way, in the case of the traveling mode and the traveling mode among the above three traveling modes, the viscous coupling is performed.
Since 10 is locked, the hump phenomenon does not occur, but in the traveling mode, the hump phenomenon may occur in some cases because the viscous coupling 10 is in the operating state.

For this reason, in this embodiment, during traveling in the traveling mode, a state in which the hump phenomenon of the viscous coupling 10 is considered to occur is detected electrically, and in that case, the traveling The mode is forcibly switched from the driving mode to the driving mode, and the viscous coupling 10
Trying to protect. Hereinafter, a control method when the hump phenomenon of the viscous coupling 10 occurs will be described with reference to FIGS. 3 and 4.

First, the method for detecting the occurrence of the hump phenomenon of the viscous coupling 10 is used. In this embodiment, the rotation difference between the first rotating shaft 21 and the third rotating shaft 23 (that is, the rotation difference between the front wheel and the rear wheel). ) Is used as a reference. That is, as shown in FIG. 3, the front and rear wheel rotation difference (ΔN) is ΔN n.
_{When it is 1} (first reference rotation difference) (first generation mode)
It is determined that the viscous coupling 10 is operating without any problem, but the continuous occurrence time (T) of the front and rear wheel rotation difference in the range of n ₁ <ΔN n ₂ (second reference rotation difference) is When the preset value (t ₁ ) is exceeded (second generation mode),
Number of occurrences of front-rear wheel rotation difference in the range of n ₁ <ΔN n ₂ (F →
f _1, f _2, · · · ·) is the case of exceeding a predetermined set number (fi) (third generation form), front and rear wheel rotation difference range .DELTA.N> n ₂ has also occurs once In the three cases of the case (fourth generation mode), it is determined that the hump phenomenon occurs in the viscous coupling 10.

The specific control flow will be described with reference to FIG. 4. First, when the vehicle is operating in the traveling mode, the rotational speeds N ₁ and N ₂ of the front wheels and the rear wheels are read, and based on this, the current front and rear wheel rotation difference is detected. ΔN is calculated, and this ΔN is compared with the first reference rotation difference n ₁ (step S ₁ ). Judgment result, ΔN
If it is n ₁ , it is the first generation mode, and it is determined that the viscous coupling 10 is operating without any trouble, and in this case, the current traveling mode, that is, the traveling mode is continued (step S ₄ ).

On the other hand, when ΔN> n ₁ , the hump phenomenon occurs in the viscous coupling 10 and the front-rear wheel rotation difference is generated in either the first generation mode, the second generation mode, or the second generation mode. This is the case where the occurrence mode of 3 is expected.
Therefore, in this case, the magnitude relationship between ΔN, the first reference rotation difference n ₁ and the second reference rotation difference n ₂ is determined (step
S ₂ ).

If ΔN> n _{2 as} a result of the determination, it is recognized as the fourth mode of occurrence. In this case, the mode switching operation is immediately performed, the traveling mode is set, and the viscous coupling 10
Is locked to protect the viscous coupling 10.

On the other hand, when n ₂ ΔN> n ₁ , the second and third modes of occurrence are expected, so first of all, a front-rear wheel rotation difference exceeding the first reference rotation difference n ₁ is generated. The time T is measured (step S ₅ ), and if T> t _1, it is recognized as the second generation mode, and the traveling mode is switched from the traveling mode to the traveling mode (step S ₈ ).

On the other hand, if T t ₁ , the third mode of occurrence is expected, so the number of times F of front-rear wheel rotation difference that exceeds the first reference rotation difference n ₁ is measured (step S ₆ ), F> fi
If it is, the third generation mode is recognized, and the mode is switched from the traveling mode to the traveling mode (step
S ₉ ).

Further, in the case of F fi, although there is a front-rear wheel rotation difference that exceeds the first reference rotation difference n ₁ , there is a concern that the hump phenomenon of the viscous coupling 10 may occur in view of the number of occurrences. is determined to be other than, it is continued as the current drive mode (step S _7).

Although the present invention is applied to the center differential of a four-wheel drive vehicle in the above embodiment, the present invention can also be applied to other differential devices, for example, an inter-wheel differential device.

(Advantageous Effects of the Invention) The present invention includes the input member to which the driving force is input from the engine side, the first output member, and the second output member, and
A differential mechanism for performing differential differential between the output member and the second output member, and a viscous coupling for transmitting power using viscosity of fluid when a rotation difference occurs between the two shafts. A differential device for a vehicle configured to limit a differential action of the differential mechanism by restricting relative rotation between the first output member and the second output member of the differential mechanism by the viscous coupling, A detecting means for detecting a rotational difference of a predetermined level or more between the first output member and the second output member of the differential mechanism when the rotational difference continues for a set time or more, and a signal from the detecting means for receiving the signal. It is characterized by comprising differential blocking means for blocking relative rotation between the first output member and the second output member.

Therefore, according to the differential device for a vehicle of the present invention, the state in which it is necessary to prevent the relative rotation between the first output member and the second output member is electrically detected by the detection means, and this detection signal is detected. Since the differential blocking means is operated on the basis of the above, (1) the viscous coupling and the differential blocking means can be individually incorporated into the differential device as separate devices, and the viscous coupling and The versatility of the viscous coupling and the differential blocking means can be improved and cost can be reduced compared to the case where unitization with the clutch functioning as the differential blocking means is required. (2) The viscous coupling is used in the vehicle body It is not necessary to pay much attention to the relative relationship with other members and equipment when applying it to the equipment from the point where it can be handled with To, From the like, the effect of being able to prevent the hump phenomenon of viscous coupling with a more simple and inexpensive structure as compared with the case of the conventional example is obtained.

[Brief description of drawings]

FIG. 1 is a skeleton diagram showing the structure of a four-wheel drive vehicle equipped with a differential device according to an embodiment of the present invention, FIG. 2 is an operation characteristic diagram of the transfer shown in FIG. 1, and FIG. 3 is a four-wheel drive. FIG. 4 is a generation pattern diagram of front-rear wheel rotation difference in the vehicle, and FIG. 4 is a control flowchart diagram of the transfer shown in FIG. 1 …… Main transmission 2 …… Output shaft (input member) 3 …… Differential mechanism 10 …… Viscous coupling 11,12 …… Clutch 15 …… Front wheel drive shaft 16 …… Rear wheel drive shaft 17,18 …… Rotation speed sensor 21 ... First rotary shaft (first output member) 22 ... Second rotary shaft (second output member) 23 ... Third rotary shaft

Claims (1)

[Claims] 1. A differential action between the first output member and the second output member, comprising an input member for inputting a driving force on the engine side, a first output member and a second output member. And a viscous coupling for transmitting power by utilizing the viscosity of the fluid when a rotation difference occurs between the two shafts. The viscous coupling allows the first output member and the first output member of the differential mechanism. Two
A differential device for a vehicle, wherein the differential action of the differential mechanism is limited by restricting relative rotation with respect to the output member, the first output member and the second output member of the differential mechanism. Between the first output member and the second output member in response to a signal from the detection means for detecting a rotation difference of a predetermined level or more for a preset time or more during A differential device for a vehicle, comprising: