JP3157213B2 - Fluid transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid transmission having a lock-up clutch.

[0002]

2. Description of the Related Art Conventionally, an automatic transmission is provided with a fluid transmission device, for example, a torque converter and a speed change mechanism, and transmits the rotation of an engine taken out by a crankshaft to an input shaft via a torque converter, and further transmits the speed change mechanism. It has a structure to transmit to. The torque converter functions as a torque converter and a fluid coupling by the action of oil circulating inside, and is constituted by a pump impeller, a turbine runner, a stator, and a lockup clutch.

That is, the rotation from the engine transmitted through the crankshaft is transmitted to the front cover and transmitted to the pump impeller fixed to the front cover. When the pump impeller rotates, the oil inside the torque converter generates a flow that rotates around the shaft, and the oil flow becomes a flow circulating between the pump impeller, the turbine runner, and the stator due to centrifugal force. .

[0004] As long as the pump impeller has just started rotating and the rotational speed difference with the turbine runner is large, the oil flowing out of the turbine runner flows in a direction that hinders the rotation of the pump impeller. Therefore, the stator is located between the pump impeller and the turbine runner and serves to convert the oil flow to a direction that assists the rotation of the pump impeller when the rotation speed difference between the two is large.

[0005] When the rotational speed difference between the pump impeller and the turbine runner decreases, the flow of oil that has hit the front side of the stator hits the reverse side. At this time, the stator starts to rotate spontaneously by the action of the one-way clutch so as not to obstruct the flow of oil. In this way, the torque converter transmits the rotation of the engine to the input shaft, but if the rotation of the engine is transmitted to the input shaft via oil while the vehicle is running, the torque transmission efficiency is poor, so the torque converter is set in advance. When the vehicle speed reaches the predetermined speed, the lock-up clutch is engaged to directly transmit the rotation of the engine to the input shaft.

The lock-up clutch has a lock-up clutch piston facing a front cover that transmits the rotation of the engine to a pump impeller. The lock-up clutch piston is disposed on the inner surface of the front cover. It is supported by the turbine hub so that it can come and go. An annular friction material is attached to the outer periphery of the lock-up clutch piston, and when the lock-up clutch is engaged, rotation of the engine is transmitted from the front cover to the turbine hub via the friction material. It has become.

The friction material is constituted by an annular body formed of a resin mixed with fibers, and one surface of the annular body is used as a friction surface, and the other surface is attached to the lock-up clutch piston with an adhesive. I have to.

[0008]

However, in the above-mentioned conventional fluid transmission device, the surface of the initially formed friction material is stuck if the fibers mixed in the resin project and the lock-up clutch is raised. , The area of contact with the inner surface of the front cover is reduced and the coefficient of friction is reduced.

The above-mentioned friction material is molded in a state in which the resin is dissolved by a solvent. When the solvent evaporates after molding, the internal resin moves with the solvent to the vicinity of the surface. A high resin ratio layer having a high resin density is formed, and the μ-v characteristics of the friction material deteriorate. As described above, the high resin ratio layer has a high resin density and accordingly has a high static friction coefficient due to the characteristics of the resin. And μ of friction material
The -v characteristic is such that when the slip rotation speed is low, the friction coefficient is high, and when the slip rotation speed is high, the friction coefficient is low.

When a friction material having such characteristics is used for a lock-up clutch, stick-slip vibration occurs when the lock-up clutch starts engagement and disengagement. SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional hydraulic power transmission device, improves the characteristics of the friction material used for the lock-up clutch, and generates vibration due to stick-slip at the start of engagement and at the start of disengagement. It is an object of the present invention to provide a fluid transmission device without any of them.

[0011]

For this purpose, in the fluid transmission of the present invention, a front cover for transmitting the rotation of the engine, a pump impeller connected to the front cover, and a pump impeller are arranged facing the pump impeller. A turbine runner provided and connected to the input shaft of the transmission mechanism;
A lock-up clutch disposed between the turbine runner and the front cover and selectively disengaged. The lock-up clutch includes a lock-up clutch piston connected to the turbine runner, and a friction material attached to one of the opposing surfaces of the lock-up clutch piston and the front cover. In addition, the friction surface of the friction material that is engaged when the lock-up clutch is started is formed of a low resin ratio layer formed by performing a cutting process.

In another fluid transmission of the present invention, the friction material further includes a friction surface formed by a high resin ratio layer on an inner peripheral portion, and a low friction material having a lower resin ratio on the outer peripheral portion than the high resin ratio layer. It has a friction surface formed by a resin ratio layer and is integrally formed.

[0013]

According to the present invention, in the fluid transmission device as described above, the front cover for transmitting the rotation of the engine, the pump impeller connected to the front cover, and the pump impeller facing the pump impeller. Arranged
Further, it has a turbine runner connected to the input shaft of the transmission mechanism, and a lock-up clutch disposed between the turbine runner and the front cover and selectively engaged and disengaged.

The lock-up clutch includes a lock-up clutch piston connected to the turbine runner, and a friction material attached to one of the opposing surfaces of the lock-up clutch piston and the front cover. . In addition, the friction surface of the friction material that is engaged when the lock-up clutch is started is formed of a low resin ratio layer formed by performing a cutting process.

In this case, the friction surface of the friction material to be engaged at the start of engagement of the lock-up clutch is composed of a low resin ratio layer formed by performing a cutting process. Slip control of the fluid transmission can be performed according to the characteristics of the low resin ratio layer. Therefore, in the low-resin-rate layer, when the slip rotation speed is low, the friction coefficient is low, and when the slip rotation speed is high, the friction coefficient is high. Can be prevented.

When the lock-up clutch is completely engaged, the lock-up clutch can be engaged with a high coefficient of static friction according to the characteristics of the high resin ratio layer.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram of a fluid transmission device of the present invention, and FIG. 2 is an explanatory diagram of a lock-up clutch piston. 2A is a cross-sectional view of a lock-up clutch piston, and FIG. 2B is an enlarged cross-sectional view of a portion surrounded by a circle in FIG.

Referring to FIG. 1, the torque converter comprises a pump impeller 1, a turbine runner 2, a stator 3, and a lock-up clutch 4. The pump impeller 1 and the turbine runner 2 form a torus 5. That is, the rotation of the engine transmitted through a crankshaft (not shown) is transmitted to the front cover 6 and transmitted to the pump impeller 1 fixed to the front cover 6. When the pump impeller 1 rotates, the oil in the torus 5 generates a flow that rotates around the shaft, and the oil flow circulates among the pump impeller 1, the turbine runner 2, and the stator 3 by centrifugal force. It becomes a flow.

When the pump impeller 1 has just started to rotate and the rotation speed difference between the pump impeller 1 and the turbine runner 2 is large, the oil flowing out from the turbine runner 2 flows in a direction that hinders the rotation of the pump impeller 1. Therefore, when the stator 3 is provided between the pump impeller 1 and the turbine runner 2 and the rotational speed difference between the two is large,
The oil flow is converted to a direction that assists the rotation of the pump impeller 1.

When the rotation speed of the turbine runner 2 increases and the difference in rotation speed between the turbine runner 2 and the pump impeller 1 decreases, the oil that has hit the front side of the blades 31 of the stator 3 has hit the back side, so that the flow is blocked. become.
Therefore, a one-way clutch 7 that allows the stator 3 to rotate only in a certain direction is provided on the inner peripheral side of the stator 3. Therefore, when the oil hits the back side of the blade 31, the stator 3 naturally rotates, and the oil can circulate smoothly. The outer race 8 of the one-way clutch 7 is connected to the stator 3, and the inner race 9 is fixed to a case of an automatic transmission (not shown).

As described above, the torque converter works as a torque converter when the rotational speed difference between the pump impeller 1 and the turbine runner 2 is large, and amplifies the torque. When the difference is small, it works as a fluid coupling. Next, the lock-up clutch 4 is operated by switching the supply of oil by a lock-up relay valve (not shown), and the lock-up clutch piston 11 moves in the axial direction, thereby engaging and disengaging the friction material 10 and the front cover 6. Will be When the front cover 6 and the lock-up clutch piston 11 are engaged via the friction material 10,
The rotation of the crankshaft is directly transmitted to an input shaft (not shown) via the front cover 6, the lock-up clutch piston 11, the damper 12, and the turbine hub 13.

The damper 12 is for absorbing a shock generated when the lock-up clutch 4 is disengaged and includes a spring 14 therein. That is, the rotation transmitted from the front cover 6 via the friction material 10 is transmitted once to the damper 12 and transmitted from the damper 12 to the turbine hub 13. In this case, the rotation is caused by the contraction of the spring 14. Can be reduced when the shock is transmitted.

The pump impeller 1 and the turbine runner 2 are composed of blades 21, 24, outer shells 22, 25, and inner cores 23, 26 disposed on both sides of the blades 21, 24. The outer shell 25 of the turbine runner 2 is connected to the damper 12 and the turbine hub 13 by rivets 27. In FIG. 2, reference numeral 11 denotes a lock-up clutch piston, and an annular friction material 10 is adhered to the outer periphery. The friction material 10 is provided near the outer peripheral edge in order to increase the contact area with the front cover 6 (FIG. 1) facing the friction material. Then, the supply of oil is switched by a lock-up relay valve (not shown) to operate, and the lock-up clutch piston 11 moves in the axial direction, so that the friction material 10 and the front cover 6 are moved.
A disengagement between them is performed. The lock-up clutch 4 is
The mounting surface of the friction material 10 is inclined from the center side to the outer periphery toward the front cover 6 so that the engagement of the lock-up clutch 4 prevents the surface of the friction material 10 from being parallel to the inner surface of the front cover 6. I have.

At this time, the pressure of the oil supplied from the lock-up relay valve is applied to the back surface 11a of the lock-up clutch piston 11. On the other hand, the friction material 10 forms a fulcrum after coming into contact with the front cover 6, and the lock-up clutch piston 11 moves the center side to the left side in the drawing by the oil pressure when the lock-up clutch 4 is completely engaged. To bend. Therefore, the lock-up clutch piston 11 is inclined from the center side to the outer peripheral side so that the surface of the friction material 10 and the inner surface of the front cover 6 are in parallel contact with each other when the engagement is completed.

Also, at a predetermined portion on the outer peripheral side of the friction material 10, a part of the surface of the friction material 10 is Flat part q
Is formed. Incidentally, the friction material 10 is formed of an annular body formed of a resin mixed with fibers, one surface of the annular body is used as a friction surface, and the other surface is attached to the lock-up clutch piston 11 with an adhesive. Like that. Also, on the surface of the initially formed annular body, if fibers mixed into the resin protrude and become fuzzy,
When used for the lock-up clutch 4, the contact area with the inner surface of the front cover 6 is reduced, and the friction coefficient is reduced.

Further, a high resin ratio layer having a high resin density exists near the surface of the annular body, and if the annular body 10 is used as it is, the μ-v characteristics will be reduced. That is, the friction material 10
The friction coefficient is high when the slip rotation speed between the motor and the front cover 6 is low, and decreases when the slip rotation speed is high. When the friction material 10 having such characteristics is used for the lock-up clutch 4, stick-slip occurs, and vibration occurs when the lock-up clutch 4 starts engagement and disengagement.

The stick-slip is a movement that occurs when a frictional force acts on the vibrating object when the vibrating object is moved through the elastic body. In this case, the lock-up clutch piston 11 The damper 12 corresponds to the elastic body. This movement has a period in which the lock-up clutch piston 11 and the front cover 6 are relatively attached (stick) and a period in which the lock-up clutch piston 11 and the front cover 6 slip (slip).

The movement during the slip period is free vibration, and the initial speed of the lock-up clutch piston 11 at the end of the slip period, that is, at the start of the stick period, is substantially equal to the drive speed of the front cover 6, and The clutch piston 11 adheres to the front cover 6. In the stick period, since the lock-up clutch piston 11 is attached to the front cover 6, the displacement between the two increases linearly with time. Since the end of the stick period is the start of the slip period, the state returns to the start state of the slip period.

Therefore, if there is no time during which the speed of the lock-up clutch piston 11 becomes equal to the speed of the front cover 6 during the slip period, stick-slip will not occur. That is, in the μ-v characteristic of the friction material 10, the friction coefficient only needs to increase as the slip rotation speed increases. Therefore, the burr after molding of the annular body is removed to increase the contact area with the inner surface of the front cover 6 and to increase the μ-v characteristic of the friction material 10 when the slip rotation speed is low. A predetermined portion of the surface of the friction surface is cut so that the friction coefficient increases when the slip coefficient increases and the slip rotation speed increases. Is prevented from occurring.

FIG. 3 is a view for explaining the surface condition of the annular body used in the fluid transmission of the present invention, and FIG. 4 is a characteristic diagram of the friction material used in the fluid transmission of the present invention. 3A is a state diagram after molding, and FIG. 3B is a state diagram after cutting. In FIG. 3, reference numeral 10 denotes a friction material, 10k denotes an annular body, e denotes a high resin ratio layer having a high resin density, and f denotes a low resin ratio layer having a low resin density. In the state (a) after molding, the high resin ratio layers e exist on both surfaces of the annular body 10k. The high resin ratio layer e has a high resin density, and has a high friction coefficient when the slip rotation speed with the front cover 6 is low, and a low friction coefficient when the slip rotation speed is high.

When the cutting is performed, the flatness is increased, and the low resin ratio layer f is exposed on the surface of the friction material 10.
As shown in FIG. 4, when the slip rotation speed between the friction material 10 and the front cover 6 is low, the friction coefficient is low, and when the slip rotation speed is high, the friction coefficient is high. Further, in the friction material 10 shown in FIG. 2, a flat portion q is formed on an inner surface of the front cover 6 by performing a cutting process on a predetermined portion of an outer peripheral portion. When the number is low, the friction coefficient is low, and when the slip rotation speed is high, the friction coefficient is high. On the other hand, portions other than the flat portion q are not subjected to cutting, so that the friction coefficient is high when the slip rotation speed is low, and the friction coefficient is low when the slip rotation speed is high.

Therefore, when the friction material 10 starts engaging with the inner surface of the front cover 6, only the flat portion q comes into contact with the inner surface of the front cover 6, and slip control of the torque converter is performed. Will be The flat portion q is cut and has a low coefficient of friction when the slip rotation speed is low, and has a high friction coefficient when the slip rotation speed is high. At this time, it is possible to prevent the occurrence of vibration due to stick-slip.

When the oil pressure in the torque converter rises and the increased oil pressure is applied to the back surface 11a of the lock-up clutch piston 11, the lock-up clutch piston 11 bends and the central portion moves forward. As a result, the flat portion q separates from the inner surface of the front cover 6, and the uncut portion other than the flat portion q contacts the inner surface of the front cover 6, and
Fully engage.

In this case, the friction material 10 and the front cover 6
Since the slip rotation speed during this period is low, and the static friction coefficient of the portion other than the flat portion q, which has not been subjected to the cutting process, increases, the engaging force increases. In addition, since the contact with the front cover 6 is made at a wide portion other than the flat portion q, the surface pressure does not increase. It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic view of a fluid transmission according to the present invention.

FIG. 2 is an explanatory diagram of a lock-up clutch piston.

FIG. 3 is a diagram illustrating a surface state of an annular body used in the fluid transmission device of the present invention.

FIG. 4 is a characteristic diagram of a friction material used in the fluid transmission of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump impeller 2 Turbine runner 4 Lockup clutch 6 Front cover 10 Friction material 11 Lockup clutch piston e High resin rate layer f Low resin rate layer q Flat part

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shuji Kato 10 Takane, Fujii-machi, Anjo, Aichi Prefecture Inside Aisin AW Co., Ltd. (72) Takuji Taniguchi 10 Takane, Fujii-machi, Anjo, Aichi Prefecture Aishi (72) Inventor Kunihiro Iwatsuki Kunihiro Iwaki 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Kazuaki Watanabe 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Company Stock In-company (72) Inventor Yasushi Ando 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Hirofumi Nakagomi 2-9-2 Izumicho, Fukuroi City, Shizuoka Prefecture Green Heights 203 (72) Inventor Mitsuro Tetsuomi 2-10-8 Izumicho, Fukuroi-shi, Shizuoka Prefecture Maison Estel 203 (56) Reference JP-A-57-140920 (JP, A) JP-A-51565 (JP, A) JP-A-57-76329 (JP, A) JP-A-1-109631 (JP, U) JP-A-56-113233 (JP, U) JP-A-56-139050 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F16H 45/02 F16D 11/00-23/14

Claims (2)

(57) [Claims] 1. A front cover for transmitting rotation of an engine, a pump impeller connected to the front cover, and a turbine runner disposed opposite to the pump impeller and connected to an input shaft of a transmission mechanism. And a lock-up clutch disposed between the turbine runner and the front cover and selectively disengaged, wherein the lock-up clutch comprises:
A lock-up clutch piston connected to the turbine runner; and a friction material attached to one of the opposing surfaces of the lock-up clutch piston and the front cover, and engagement of the lock-up clutch with the friction material. friction surface which is engaged at the start, the switching
A hydraulic power transmission, wherein formed <br/> Rukoto low resin index layer formed by applying a cutting processing. 2. The friction material has a high resin ratio layer on an inner peripheral portion thereof .
The friction surface formed I, provided with a friction surface of the resin ratio is formed by a lower low resin index layer from the high resin index layer on the outer periphery,
Hydraulic power transmission device according to claim 1 that will be formed integrally.