JPH0617905A - Hydraulic power transmission provided with lockup clutch - Google Patents

Abstract

PURPOSE:To determine force of pressing a friction plate against a front cover. CONSTITUTION:A friction plate 31 is frictionally slid against a front cover 4. A hydraulic chamber 28 to which a hydraulic pressure is applied for engagement of a lockup clutch 11 is formed between a damper mechanism 13 and an inner surface of the front cover 4. A pressure receiving area of the lockup clutch 11 at the engagement of the lockup clutch 11 is set wider than a pressure receiving area of the damper mechanism 13, which pressure is a hydraulic pressure from the hydraulic chamber 28. Pressing force in respect to the friction plate 31 is determined according to the difference between the pressure receiving areas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic power transmission device having a lockup clutch such as a torque converter in an automatic transmission for a vehicle.

[0002]

As is well known, a fluid transmission device such as a torque converter transmits torque through a fluid.
The transmission efficiency is not always good, and therefore, recently, in order to improve the transmission efficiency of power and improve fuel efficiency, a lockup clutch is widely incorporated in a torque converter. Since the lockup clutch directly connects the input-side member and the output-side member of the torque converter by a mechanical means, it also transmits the vibration due to the fluctuation of the input torque. Therefore, normally, a damper mechanism is also used for the lockup clutch.

Conventionally, a damper mechanism is generally provided between an output member such as a hub to which a turbine runner is attached and a lockup clutch. However, the applicant of the present invention has developed a rotary inertia mass in order to improve vibration damping characteristics. A large-sized damper mass is connected to an input side (driving side) member such as a housing via a damper spring, and a lockup clutch is engaged with the damper mass. Proposed by No. 3-309835. With such a configuration, the damper mass acts as an inertial resistance with respect to the fluctuation of the input torque,
The damper spring absorbs the fluctuation of the input torque to damp the vibration and prevent muffled noise.

[0004]

In the fluid transmission device described above, vibration damping characteristics are excellent because the inertia resistance due to the damper mass is large, but the input torque fluctuates greatly, for example, when the accelerator is suddenly turned on and off. In this case, the amount of bending of the damper spring, that is, the amount of elastic energy stored by the damper spring, fluctuates greatly.
Therefore, in such a case, the damper spring absorbs and releases the elastic energy, so that a large torque fluctuation is input to the automatic transmission through the lock-up clutch. As a result, a long-wavelength torque fluctuation occurs in the output shaft of the automatic transmission, and this may be felt as so-called "hiking", which may deteriorate the riding comfort of the vehicle.

In order to eliminate such inconvenience, it is considered that sliding friction is given to relative rotation of the damper mass to increase hysteresis in the damper mechanism. However, since the frictional force is determined by the friction coefficient and the surface pressure of the contact surface, if the friction member is simply interposed between the front cover and the damper mechanism, the surface pressure will not be constant, and the frictional force will be as expected. May not be obtained. That is, while the housing of the torque converter is made thin to reduce its weight, the converter hydraulic pressure acts on the housing to increase the pressure, so that the housing expands when the torque converter operates. Therefore, the dimension between the front cover and the damper mechanism changes, so that the contact pressure of the friction member interposed therebetween changes. The amount of deformation of the torque converter housing due to hydraulic pressure is not always constant, and
Since it is difficult to calculate in advance, the contact pressure between the friction member and the front cover or damper mechanism does not reach the intended pressure, and as a result, the effect of preventing hiccups cannot be obtained, or conversely, excessive There is a possibility that sliding friction may occur and durability may be reduced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydraulic power transmission device with a lock-up clutch, which is capable of obtaining a stable hiccup prevention effect.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention forms a housing by an outer shell of a pump impeller for generating a fluid flow and a front cover integrally connected to the outer shell. A turbine runner is arranged in the housing so as to face the pump impeller, and a lock-up clutch for selectively transmitting torque between the housing and an output member integrated with the turbine runner is provided in the front cover. In a fluid transmission device with a lock-up clutch arranged to move back and forth by hydraulic pressure toward an inner surface, a rotary inertia mass body engaged with the lock-up clutch is elastically driven by a drive member that rotates integrally with the housing. The direction in which the damper mechanism supported via the inner cover moves toward and away from the inner surface of the front cover. While being movably arranged,
A friction member that frictionally slides with respect to the front cover is arranged between the damper mechanism and the inner surface of the front cover, and a hydraulic pressure for engaging a lockup clutch between the damper mechanism and the inner surface of the front cover. Is formed, and the pressure-receiving area of the lock-up clutch when the lockup clutch is engaged is set to be wider than the pressure-receiving area that receives the hydraulic pressure from the hydraulic chamber of the damper mechanism.

[0008]

In the present invention, the damper mechanism is arranged between the lock-up clutch and the front cover, and the lock-up clutch is pressed by the hydraulic inertia mass of the damper mechanism into the engaged state. In the hydraulic chamber between the damper mechanism and the front cover,
The hydraulic pressure to engage the lockup clutch acts,
Since the pressure receiving area of the lock-up clutch is wider than the pressure receiving area of the damper mechanism, a load that pushes the damper mechanism toward the front cover acts. Since this damper mechanism can be moved to the front cover side,
When the lockup clutch is engaged, the friction member interposed between the damper mechanism and the front cover is pressed against the front cover side by the damper mechanism. That is, the contact pressure between the front cover of the friction member and the damper mechanism is secured by the hydraulic pressure that engages the lockup clutch to generate the desired frictional force, and as a result, the absorption and absorption of elastic energy in the damper mechanism.
You can effectively prevent hiccups due to large release,
In addition, the prevention effect is stable.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the present invention, in which a shell 2 of a pump impeller 1 is integrally connected to a front cover 4 via an annular extension member 3. The extension member 3 and the front cover 4 form a torque converter housing 5. Inside the housing 5, a turbine runner 6 is arranged so as to face the pump impeller 1.
The turbine runner 6 is attached at its inner peripheral portion to a hub 7 which is an output member by rivets 8. Further, between the pump impeller 1 and the turbine runner 6, and on the inner peripheral side thereof, a stator 10 spline-fitted to the outer race of the one-way clutch 9 is arranged. And the inner surface of the front cover 4 and the turbine runner 6
A damper mechanism 13 including a lock-up clutch 11 and a damper mass 12, which is a rotary inertia mass body, is disposed between and.

The lock-up clutch 11 is a lock-up piston 14 which is an annular plate member curved along the back surface (left side surface in FIG. 1) of the turbine runner 6 and a lining material attached to the outer peripheral side surface thereof. It is composed of 15 and. A cylindrical portion 16 is formed on the inner peripheral portion of the lock-up piston 14, and the cylindrical portion 16 is formed.
A plurality of protrusions 17 that act as engaging teeth for torque transmission are formed at one end of the so as to be spaced at regular intervals in the circumferential direction and project toward the inner peripheral side.

The lock-up piston 14 is the hub 7
Is fitted so as to be slidable in the axial direction. This hub 7
Has a boss portion 18 into which the cylindrical portion 16 of the lockup piston 14 is fitted, and a seal ring 19 attached thereto seals the lockup piston 14 and the lockup piston 14 in a liquid-tight state. . Also this boss 1
A plurality of protrusions 20 that engage with the protrusions 17 in the circumferential direction are formed on one side surface of the protrusion 8. Therefore, torque is transmitted between the lock-up piston 14 and the hub 7 by the protrusion 17 and the protrusion 20.

The damper mass 12 has a main member 21 having an outer diameter substantially equal to that of the lock-up piston 14 and an inner diameter smaller than that of the lock-up piston 14 and having a substantially annular shape as a whole, and having a larger inner diameter and smaller mass. It is composed of an annular cover member 22. The main member 21 and the cover member 22 are connected to each other by rivets 23 so as to face each other to form the damper mass 12, and are arranged between the lockup piston 14 and the inner surface of the front cover 4. This damper mass 12
The inner peripheral portion of the main member 21 is rotatably fitted to the outer peripheral surface of the annular protrusion 24 provided on the inner surface of the front cover 4 so as to be positioned on the same axis as the housing 5. That is, it is centered with respect to the housing 5.

Further, on the main member 21, an annular projection 25 having an inner diameter larger than that of the cylindrical portion 16 of the lockup piston 14 is formed toward the inner surface of the front cover 4. The annular protrusion 25 is rotatably fitted to a cylindrical portion 26 provided on the inner surface of the front cover 4. A space between the annular projection 25 and the cylindrical portion 26 is sealed in a liquid-tight state by a seal ring 27 attached to the cylindrical portion 26. That is, the radius R ₁₂ of the seal portion on the inner peripheral side of the damper mass 12 is larger than the radius R ₁₄ of the seal portion on the inner peripheral side of the lock-up piston 14. By sealing the space between the front cover 4 and the damper mass 12 with a seal ring 27 in a liquid-tight state, a hydraulic chamber 28 is formed between the inner surface of the front cover 4 and the damper mass 12.

Main member 2 forming damper mass 12
In each of the facing portions of 1 and the cover member 22, a plurality of concave portions along the circumferential direction are formed at regular intervals, and a damper spring 29 which is a coil spring is accommodated therein. A center plate 30 which is an annular plate-shaped member is provided between the main member 21 and the cover member 22.
However, they are sandwiched so as to be rotatable relative to the damper mass 12. Further, the center plate 30 is formed with a window hole into which the damper spring 29 is fitted. Therefore, when the damper mass 12 and the center plate 30 rotate relatively, the damper mass 12 and the center plate 30 compress the damper spring 29.

Further, the outer peripheral portion of the center plate 30 is
The housing 5 is engaged with the housing 5 in the circumferential direction, and torque is transmitted between the two. As the meshing structure, various structures can be adopted as required. For example, the outer peripheral end of the front cover 4 is formed with teeth protruding in the axial direction, and the outer peripheral end of the center plate 30 is formed. It is also possible to form teeth protruding outward in the radial direction and mesh these teeth to transmit torque between the housing 5 and the center plate 30. Therefore, the center plate 30 is a driving member that rotates together with the housing 5. Then, the damper mass 12 and the damper spring 29 described above are used.
And a damper mechanism 1 including the center plate 30
3 can move slightly in the axial direction.

The torque converter shown in FIG. 1 further includes a friction mechanism. This friction mechanism serves to prevent a so-called hiccup by absorbing a part of the elastic energy released by the damper spring 29. In the example shown in FIG. 1, the inner surface of the front cover 4 and the damper mechanism 13 are separated from each other. The friction plate 31 interposed therebetween is mainly configured. 2 and 3 show the shape of the friction plate 31.

That is, the friction plate 31 is in the form of a disc spring which is annular as a whole, and the leaf spring portion which acts as a spring is provided at four points of the ring portion 33 having a diameter larger than the annular projection 25 of the main member 21 described above. 32 is formed. The leaf spring portion 32 is formed by protruding a plurality of claw pieces 34 projecting in the inner peripheral direction and the outer peripheral direction toward the damper mechanism 13 side in the installed state.
The four claw pieces 34 are provided at four locations on the inner circumference side and two at the outer circumference side. A friction material 36 is attached to the surface of the ring portion 33 that faces the inner surface of the front cover 4 in the installed state.

The friction plate 31 is arranged between the center plate 30 of the damper mechanism 13 and the inner surface of the front cover 4 by elastically deforming the leaf spring portion 32, and has such an arrangement structure. Therefore, the cover member 2 which is one member of the damper mass 12
2 includes a leaf spring portion 3 of the friction plate 31.
Punching portions 37 for allowing 2 to enter are formed at four places. The relative position in the assembled state with the friction plate 31 is shown in FIG.

As shown in FIG. 4, the punched portion 37 has a narrow width in the circumferential direction (that is, a small central angle) on the outer peripheral side and a wide width in the circumferential direction (that is, a large central angle). ) It is formed from the inner peripheral side portion. The outer peripheral claw piece 34 of the friction plate 31 is arranged inside the narrow portion of the punched portion 37 and is in contact with the side surface of the center plate 30. The inner peripheral claw piece 34 is arranged inside the wide portion of the punched-out portion 37, and the claw piece 34 is in contact with the side surface of the center plate 30.

The interval between the edge 38 of the wide portion of the punched-out portion 37 and the edges 39 at both ends in the circumferential direction of the claw piece 34 on the inner peripheral side is set to θ at the central angle, and therefore the damper is formed. When the mass 12 rotates relative to the front cover 4 or the center plate 30 by an angle θ or more (when twisted), the damper mass 12 engages with the friction plate 31 and both rotate together. Similarly, when the relative rotation (twisting) of the angle 2θ or more in the opposite direction is continued, the damper mass 12 and the friction plate 31 are also integrally rotated.

The friction plate 31 is provided between the center plate 30 and the front cover 4 as described above.
By being elastically deformed and arranged in the axial direction, the friction material 36 attached to the ring portion 33 is in frictional contact with the inner surface of the front cover 4. In that case, the claw pieces 34 on the inner peripheral side and the claw pieces 34 on the outer peripheral side of the friction plate 31.
And are in elastically deformed contact with the center plate 30, and therefore the elastic force of these claw pieces 34 acts on both the inner peripheral side and the outer peripheral side of the ring portion 33, and as a result, the ring portion 33 Friction material 36 attached to the portion 33
However, almost the entire surface contacts the inner surface of the front cover 4,
When a relative slip occurs, a sufficient sliding friction force is generated.

The above-described torque converter transmits the torque by applying the fluid flow generated by the pump impeller 1, that is, the spiral flow of oil, to the turbine runner 6 to rotate the turbine runner 6, and therefore the housing 5. The inside of the is filled with oil. The lock-up clutch 11 is a clutch that engages and disengages according to the pressure difference between both sides of the lock-up piston 14, and therefore, the lock-up piston 14 is provided in the space on the turbine runner 6 side with respect to the lock-up piston 14. An oil passage for supplying hydraulic pressure (oil passage indicated by arrow A in FIG. 1) and an oil passage for supplying hydraulic pressure between the lockup piston 14 and the damper mass 12 (oil passage indicated by arrow B in FIG. 1) are provided. Has been formed.

As is known from the configuration shown in FIG.
When the lock-up piston 14 moves to the left in FIG. 1 and the lining material 15 comes into contact with the damper mass 12 so that torque can be transmitted, that is, when the lock-up clutch 11 is engaged, the hydraulic chamber 28 is locked with the damper mass 12. Although not in communication with the up piston 14, it is in communication with the location where hydraulic pressure is supplied from the lock up piston 14 to the turbine runner 6 side, that is, in the direction of arrow A. In other words, the hydraulic pressure for engaging the lockup clutch 11 also acts on the hydraulic chamber 28.

Next, the operation of the torque converter shown in FIG. 1 will be described. FIG. 1 shows a lock-up / off state, that is, a state in which the lock-up clutch 11 is released. Supplying hydraulic pressure from the direction of arrow B to increase the hydraulic pressure between the lock-up piston 14 and the damper mass 12. As a result, the lockup piston 14 is separated from the damper mass 12. When torque is applied to the front cover 4 from an engine (not shown) in this state, the pump impeller 1 rotates together with the housing 5 to generate a spiral flow of oil. By giving the spiral flow to the turbine runner 6, torque is transmitted to the turbine runner 6 and rotates together with the hub 7. The torque is transmitted to the automatic transmission via an input shaft (not shown) fitted to the hub 7.

When the lockup clutch 11 is engaged, that is, when the lockup is turned on, the lockup clutch 11 shown in FIG.
The hydraulic pressure is supplied in the direction of arrow A and is discharged in the direction opposite to arrow B. The lining material 15 and the main member 2
Since the distance between the lockup piston 1 and the main member 21 is small, the orifice effect in this portion reduces the pressure in the space between the lockup piston 14 and the main member 21.
4, the pressure in the space on the turbine runner 6 side of the lock-up piston 14 is higher than that of the lock-up piston 14. As a result, the lockup piston 14 relatively approaches the damper mass 12, and the lining material 15 comes into contact with the side surface of the main member 21 so that torque can be transmitted.

In this case, the hydraulic chamber 28 is the seal ring 27.
Damper mass 12 and lock-up piston 1
4 is fluid-tightly sealed against a low-pressure portion between the lockup piston 14 and the damper mass 12 and is in communication with a high-pressure portion on the turbine runner 6 side. It becomes equal to the pressure that pushes to the side. Since the radius R ₁₂ of the seal portion on the inner peripheral side that divides the hydraulic chamber 28 is larger than the radius R ₁₄ of the seal portion on the inner peripheral side of the lockup piston 14, the lockup piston 14
The load for pushing to the left in FIG. 1 is larger than the load for pushing the damper mass 12 to the right in FIG.

That is, the hydraulic pressure for engaging the lockup clutch 11 is Pa, the hydraulic pressure between the lockup piston 14 and the damper mechanism 13 is Pb, and the diameter of the seal portion for isolating the places where these hydraulic pressures act is R0. Then, the force F14 that pushes the lock-up piston 14 to the left in FIG. 1 is F14 = π × (R ₀ ² −R ₁₄ ² ) × (Pa−Pb), and the damper mechanism 13 is set to the right in FIG. The force F13 pushing in the direction is F13 = π × (R ₀ ² −R ₁₂ ² ) × (Pa−Pb). Since R ₁₄ <R ₁₂ and the pressure receiving area of the lock-up piston 14 is wider than the pressure receiving area of the damper mechanism 13, the damper mechanism 13 causes the force difference FF = F14−F13 = π × (R ₁₂ ^2- R ₁₄ ² ) x (Pa-P
It is pushed to the left in Fig. 1 in b). Therefore, the friction plate 31 arranged between the center plate 30 and the front cover 4 is pressed against the front cover 4 by the force F.

The input torque transmitted from the engine to the front cover 4 is transmitted to the damper mass 12 via the damper spring 29 in the damper mechanism 13, and the lockup piston 1 is further transmitted from the damper mass 12.
4 is transmitted. When the input torque fluctuates, the damper mass 12 is rotatable with respect to the housing 5, and the lock-up piston 14 is in contact with the damper mass 12 so that torque can be transmitted. Members such as the lockup piston 14 act as inertial resistance. As a result, the damper spring 29 is compressed according to the fluctuation of the input torque, and the damper spring 29 absorbs the vibration. Further, since the sliding resistance between the damper mass 12 and the housing 5 is small, muffled noise can be prevented when the input rotation speed is high.

Further, in the structure shown in FIG. 1, when the fluctuation of the input torque is large, the friction mechanism acts to prevent or suppress the hiccup phenomenon. That is, if the input torque increases with the lock-up clutch 11 engaged, the relative rotation angle (twisting angle of the damper mechanism 13) between the damper plate 12 and the center plate 30 that is the driving side member increases. When the input torque abruptly fluctuates in a state of a predetermined twist angle, the twist angle of the damper mechanism 13 increases, and the angle is the center between the edge 38 of the punched portion 37 and the edge 39 of the claw piece 34 described above. When the angle becomes equal to the angle θ, these edges 38 and 39 contact each other, and the damper mass 12 rotates relative to the center plate 30 and the front cover 4 while pushing the friction plate 31. As described above, since the friction plate 31 is pressed against the front cover 4 by the force based on the hydraulic pressure that engages the lockup clutch 11, the friction plate 31 is attached to the front cover 4.
By sliding with respect to each other, torque is transmitted by a frictional force between the two. That is, a resistance force is generated in a direction that suppresses the twist of the damper mechanism 13.

When the input torque fluctuates in the direction of decrease and elastic damper 29 starts to release elastic energy, the damper mechanism 13 is started.
The twist angle at starts to decrease, and as a result, the damper mass 12 and the friction plate 31 are separated from each other. Then, when the twist angle of the damper mechanism 13 increases in the opposite direction to the above-mentioned case and the angle from the start of the decrease of the twist angle reaches 2θ, the edge 38 on the opposite side of the punched-out portion 37 and the claw opposed thereto. The edges 39 of the pieces 34 come into contact with each other, and as a result, the friction plate 31 is pushed by the damper mass 12 and rotates together with the damper mass 12. Therefore, also in this case, a resistance force is generated between the front cover 4 and the damper mass 12 in a direction in which the torsion of the damper mechanism 13 is suppressed.
This is the transmission of torque in the so-called negative direction, and after the twist in the negative direction reaches the limit, torque transmission and twist in the positive direction that give torque from the member on the drive side occur, and the angle When the angle reaches 2θ, as described above, the friction plate 31 and the damper mass 12 are engaged with each other to rotate integrally, and sliding resistance is generated between the damper mass 12 and the front cover 4.

As described above, in the torque converter shown in FIG. 1, when the twist angle of the damper mechanism 13 becomes a predetermined angle or more, sliding resistance is generated between the driving side member and the output side member. As a result, when the fluctuation of the input torque is large, a part of the power acting in the direction of compressing the damper spring 29 and a part of the power released by the damper spring 29 are absorbed by the sliding friction by the friction plate 31, It is possible to suppress or prevent hiccup due to compression / expansion of the damper spring 29.

The sliding friction of the friction plate 31 which suppresses the hiccups is caused by the friction plate 31.
Occurs due to relative rotation with respect to the front cover 4, and the force pressing the friction plate 31 against the front cover 4 is the hydraulic pressure for engaging the lockup clutch 11 and the pressure received by the lockup clutch 11 and the damper mechanism 13. Since the force is determined by the area difference, it is possible to obtain a stable pressing force without being substantially affected by manufacturing errors and assembly errors. In other words, the hiccup prevention effect is stable, and the friction plate 3
Dimensional management of 1 etc. becomes easy.

The present invention is not limited to the above-described embodiment. For example, instead of attaching a seal ring 19 for sealing between the hub 7 and the lockup clutch 14 to the outer peripheral surface of the hub 7, FIG. As shown in, the O-ring 40 may be fitted on the inner peripheral surface of the lockup clutch 14 to seal between the hub 7 and the lockup clutch 14. In this way, the sealing material can be easily attached.

The lining material 15 for generating a frictional force for transmitting torque between the lock-up piston 14 and the damper mass 12 is mounted on the lock-up piston 14 instead of being attached to the lock-up piston 14, as shown in FIG. May be attached to. In this way, the turbine runner 6
Since the inertial force of the output side member such as, for example, becomes smaller, it is advantageous in reducing the shift shock, and the drive side inertial force of the damper mechanism 13 and the like becomes larger, so that the idle speed decreases and the fuel consumption improves accordingly. Be advantageous to.

In the structure shown in FIG. 1, the force pressing the friction plate 31 against the front cover 4 is
Since it acts on the friction plate 31 via the main member 21 and the center plate 30 in the damper mechanism 13, a load acts between the main member 21 and the center plate 30 in the direction of bringing them into contact with each other. When the main member 21 and the center plate 30 are brought into contact with each other over a wide area by this load to generate a frictional force, the hysteresis of the damper mechanism 13 in the state where the fluctuation of the input torque is small becomes large, which is disadvantageous in reducing muffled noise. Become. Therefore, when it is necessary to reduce the friction between the main member 21 and the center plate 30 as much as possible, a bearing 41 is provided between the main member 21 and the center plate 30 as shown in FIG. It should be provided.

The friction member according to the present invention is
Since it is pressed against the front cover by hydraulic pressure, it need not be particularly elastic.

[0037]

As is apparent from the above description, according to the present invention, the friction member that causes the hysteresis of the damper mechanism is loaded by the load based on the difference in the pressure receiving area between the lock-up clutch and the damper mechanism engaged with the lock-up clutch. Since it is configured to obtain the desired frictional force by pressurizing, it is possible to obtain the predetermined frictional force and the accompanying hysteresis without being substantially affected by the dimensional accuracy of the friction member and other members with which it comes into contact,
As a result, it is possible to effectively prevent hiccups, stabilize the effect of hiccups, and facilitate dimensional control of parts such as friction members.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a front view of the friction plate.

3 is a cross-sectional view taken along the line III-III in FIG.

FIG. 4 is a partial front view showing a state where a friction plate is assembled to a damper mechanism.

FIG. 5 is a partial cross-sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 1 Pump Impeller 2 Shell 4 Front Cover 5 Housing 6 Turbine Runner 11 Lockup Clutch 12 Damper Mass 28 Hydraulic Chamber 29 Damper Spring 30 Center Plate

Claims (1)

[Claims] 1. A housing is formed by an outer shell of a pump impeller for generating a fluid flow and a front cover integrally connected to the outer shell, and a turbine runner is arranged in the housing so as to face the pump impeller. Further, a lock-up clutch for selectively transmitting torque between the housing and an output member integrated with the turbine runner is arranged so as to be moved back and forth by hydraulic pressure toward the inner surface of the front cover. In the fluid transmission device, a damper mechanism in which a rotary inertia mass body engaged with the lock-up clutch is supported by a drive member that rotates integrally with the housing via an elastic body is provided with respect to an inner surface of the front cover. And the damper mechanism and the flow mechanism. A friction member that slides frictionally with respect to the front cover is arranged between the inner cover and the inner surface of the front cover, and a hydraulic chamber in which a hydraulic pressure for engaging the lockup clutch acts between the damper mechanism and the inner surface of the front cover. And a pressure-receiving area of the lock-up clutch when the lock-up clutch is engaged is set to be wider than a pressure-receiving area for receiving hydraulic pressure from the hydraulic chamber of the damper mechanism.