JP2507718B2 - Vehicle differential equipment - 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 a 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, as is well known, viscous coupling
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, reliability, etc. to combine these two parts having different performance, reliability, etc. into a unit, and there is room for improvement in this respect.

In addition, the hump phenomenon of the viscous coupling described above occurs in a short time when the rotational speed is relatively large, and the mechanical conventional example cannot effectively cope with this in terms of its responsiveness. There is a nature.

Furthermore, in the above-mentioned known example, when the temperature of the viscous coupling becomes higher than a predetermined value, that is, after the sudden differential that causes the temperature rise of the viscous coupling occurs, the operation of the viscous coupling is performed ex post facto. Since air bubbles are already generated in the viscous fluid by such operation freezing, the proper operation characteristics of the viscous coupling are hindered, or the viscous coupling is accompanied by a large input. There is a concern that it will break down.

(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 differential limitation of a differential mechanism is performed by viscous coupling. With such a configuration, a state in which a hump phenomenon occurs in the viscous coupling can be detected accurately and in advance, and this can be prevented in advance.

(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. Viscous coupling for transmitting power using the viscosity of fluid when a rotation difference occurs between the differential mechanism and the two shafts, which differentially operates between the first output member and the second output member. And a viscous coupling for restricting 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. In the differential device, when there is a rotation difference of a predetermined level or more between the first output member and the second output member of the differential mechanism, this is detected. Outputting detection means, differential blocking means for blocking relative rotation between the first output member and the second output member, and a signal from the detection means are input to determine that the rotation difference is a predetermined value or more. And a control means for controlling the differential prevention means so as to prevent a differential between the first output member and the second output member when being operated.

In this configuration, the predetermined level may be set to a value corresponding to the relatively high rotational speed difference such that the viscous coupling immediately causes a hump phenomenon.

(Operation) According to the present invention, with such a configuration, when a speed difference of a predetermined level or more occurs between the first output member and the second output member of the differential mechanism, that is, the hump phenomenon in the viscous coupling. When it is considered that there is a risk that the differential limiting action of the differential mechanism will not be effectively performed due to the occurrence of the above, the above-mentioned detecting means detects this and at the same time receives the signal from the above-mentioned detecting means. Means controls the differential blocking means to block relative rotation of the first output member and the second output member.

(Effects of the Invention) Therefore, according to the vehicle differential device of the present invention, the state in which it is necessary to prevent the relative rotation of the first output member and the second output member is electrically detected by the detection means, Since the control means controls the operation of the differential blocking means on the basis of this detection signal, (1) the viscous coupling and the differential blocking means can be separately incorporated into the differential device. The versatility of the viscous coupling and the differential blocking means is improved as compared with the case where the viscous coupling and the clutch functioning as the differential blocking means need to be unitized as in the conventional example, and the cost can be reduced. (2) Since the viscous coupling can be handled alone, it is necessary to pay close attention to the relative relationship with other members and equipment when applying it to the equipment. Since the degree of freedom in application to the device is improved, etc., the effect that the hump phenomenon of the viscous coupling can be surely prevented by the simpler and cheaper configuration than the case of the above-mentioned conventional example is obtained. In addition, even when the hump phenomenon occurs in a relatively short time, it can be dealt with without a response delay.

(3) Further, when a speed difference of a predetermined level or more occurs between the first output member and the second output member of the differential mechanism, that is, the hump phenomenon occurs in the viscous coupling and the differential of the differential mechanism is changed. When it is considered that there is a risk that the limiting action will not be effectively performed, the differential preventing means is controlled by the control means at that time to control the first output member and the second output member of the differential mechanism. Since the relative rotation between the viscous fluid and the viscous fluid is prevented, an excessive temperature rise of the viscous fluid that causes the hump phenomenon of the viscous coupling is suppressed. Freezing the differential when the temperature rises above a certain value Viscous coupling cavitation occurrence or excess as in the conventional example No problem such as a failure by the force, the driving force distribution control to the front and rear wheels by the differential device is intended to be maintained satisfactorily over a long term.

(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.
26 and an inner plate 27 provided on a rotary shaft 28 that is relatively rotatably fitted in the casing 25,
A known viscous coupling in which a viscous fluid (for example, silicon oil) is enclosed in the casing 25, and the casing 25 of the viscous coupling 10 includes the first rotary shaft 21 and the rotary shaft 28. Are respectively coupled to the second rotating shafts 22. Therefore, when a speed difference occurs between the first rotating shaft 21 and the second rotating shaft 22, the first rotating shaft 21 and the second rotating shaft 21 are connected to each other via the viscous coupling 10.
Power is transmitted between the rotating shafts 22 of each other.

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 that control the inflow of hydraulic oil into the chamber 53, and connect the supply oil passage 55 that communicates with the oil chamber (not shown) of the first clutch 11 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 operates by opening and closing the second electromagnetic on-off valve 34. Be punished. 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 A normal four-wheel drive traveling in which the operation of the differential mechanism 3 is restricted by the viscous coupling 10 (hereinafter, abbreviated as normal 4WD for convenience of description) is realized (traveling 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 this embodiment, as described above, it is possible to travel by selecting any traveling mode by the mode selection switches 41, 42, 43, but during 2WD traveling, it is suitable for the current driving state. The drive mode is determined and the drive mode can be automatically switched from 2WD drive to 4WD drive. That is, when there is a rotation difference of more than a predetermined value between the front and rear wheels in 2WD traveling (that is, when the drive wheels slip), the drive mode is switched from 2WD traveling to 4WD traveling. , In the region where the rotational difference is relatively small, the normal 4WD traveling in which there is a differential limitation within the 4WD traveling is performed, but in the region where the rotational difference is larger than a predetermined value, the viscous coupling 10 does not function sufficiently ( In other words, viscous coupling 10
It is judged that there is a risk that a hump phenomenon will occur in the vehicle and the differential limiting action will not be effectively performed), and in this area, 2WD running or normal 4WD running is switched to direct drive 4WD running. . Hereinafter, a specific control method of the automatic switching of the traveling mode will be described with reference to FIGS. 3 and 4.

First, in a state where 2WD traveling in the traveling mode is performed, a rotation difference between the first rotating shaft 21 and the third rotating shaft 23 (that is, a rotation difference between the front wheels and the rear wheels, ΔN) is calculated (step S ₁ ), When the rotation difference ΔN is ΔN n ₁ (first reference rotation difference) (during the first generation mode shown in FIG. 3), a slip that makes it difficult to drive in 2WD is generated. not without and, therefore, it determines that the continuation of the 2WD running is best to continue the running mode (step S _4).

On the other hand, when ΔN> n _1, it is determined that there is a slip between the front and rear wheels that cannot be covered by 2WD driving, and it is necessary to switch the driving mode to 4WD. However, in this case, it is determined whether the viscous coupling 10 is causing a hump phenomenon according to the magnitude of the rotation difference, and based on that, whether the normal 4WD or the direct connection 4WD among the 4WD is determined ( step S _2). That is, as a result of the calculation, when the rotation difference ΔN is n ₁ <ΔN ≦ n ₂ (second reference rotation difference) (during the second generation mode in FIG. 3),
It is judged that the viscous coupling 10 is not likely to cause the hump phenomenon and has sufficiently limited the differential action.In this case, the drive mode is switched to the drive mode and normal operation is performed.
The 4WD traveling (step S _5).

On the other hand, when ΔN> n ₂ (during the third generation mode in FIG. 3), the viscous coupling 10 causes a hump phenomenon and reaches a state in which the differential limiting function is not fulfilled sufficiently. There is a fear that it is necessary to lock the operation of the viscous coupling 10 immediately to protect it.In this case, switch the drive mode to the drive mode and directly connect 4WD.
Traveling to (Step S _3).

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.

[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 …… Clutch 12 …… Clutch 15 …… Front wheel drive shaft 16 …… Rear wheel drive shaft 17 …… Rotational speed sensor 18 ... Rotational speed sensor 21 ... First rotating shaft (first output member) 22 ... Second rotating shaft (second output member) 23 ... Third rotating shaft

Claims (1)

(57) [Claims] 1. An input member to which a driving force is input from an engine side, a first output member, and a second output member are provided.
A differential mechanism that performs a differential action between the output member and the second output member, and a viscous coupling that transmits power using the viscosity of the 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. Detecting means for detecting a rotation difference of a predetermined level or more between the first output member and the second output member of the differential mechanism, and the first output member and the second output. The differential blocking means for blocking relative rotation with the member, and the first signal when the signal from the detecting means is input and the rotation difference is determined to be a predetermined value or more. Differential apparatus for a vehicle, characterized in that a control means for controlling the differential blocking means in order to prevent the differential between the output member and the second output member.