JP2013024325A - Lockup clutch mechanism of torque converter and method of manufacturing front cover to be used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lockup clutch mechanism of a torque converter configured to increase calorific capacity and stiffness of a front cover, and to reduce the wall thickness and weight of the front cover, while preventing the front cover from being unbalanced.SOLUTION: The lockup clutch mechanism is mainly composed of the front cover 3 constituting a part of converter housing 2 and a lockup clutch piston 7. An annular different-material sliding layer 13 is formed by thermal spraying on a part of an inner surface 3d in a bottom wall part 3c of the front cover 3, which faces a clutch fading 12 of the lockup clutch piston 7. The different-material sliding layer 13 is made, for example, of cast iron.

Description

  The present invention relates to a lockup clutch mechanism for a torque converter incorporated in an automatic transmission for a vehicle and a method for manufacturing a front cover used therefor.

  In this type of torque converter lock-up clutch mechanism, a front cover that forms a converter housing together with a pump impeller, and a lock-up clutch that is housed inside the front cover and that can be moved closer to and away from the bottom wall of the front cover. A piston, and an annular friction material mounted on a portion of the lockup clutch piston facing the bottom wall of the front cover, and the friction material is attached to the bottom of the front cover together with the lockup clutch piston. Lock-up is possible by pressing against the wall and friction fastening.

  Patent Document 1 discloses a structure in which an annular sliding member such as cast iron is disposed in a portion of the front cover facing the friction material on the lockup clutch piston side for the purpose of increasing heat capacity and improving rigidity. As proposed by the present applicant.

JP 2010-106900 A

  However, in the lock-up clutch mechanism described in Patent Document 1, a sliding member separate from the front cover is fixed to the bottom wall portion of the front cover by brazing. The thickness and weight are both larger than necessary, and a large heat capacity can be secured. However, there is still room for improvement in reducing the size and weight of the lockup clutch mechanism and the torque converter.

  In addition, since both the plate thickness and weight of the sliding member brazed as described above are larger than necessary, unbalance is likely to occur during rotation of the front cover (converter housing), and this unbalance is minimized. But there is still room for improvement.

  The present invention has been made paying attention to such problems, while increasing the heat capacity and rigidity of the portion of the bottom wall portion of the front cover where the friction material is pressed, The present invention provides a torque converter lock-up clutch mechanism which eliminates the occurrence of weight reduction and unbalance, and a method of manufacturing a front cover used therefor.

  According to the first aspect of the present invention, the front cover that forms the converter housing together with the pump impeller, and is housed and disposed inside the front cover, can approach and separate from the bottom wall of the front cover in the axial direction of the front cover. A lock-up clutch piston, and an annular friction material mounted on a portion of the lock-up clutch piston facing the bottom wall of the front cover, and the friction material together with the lock-up clutch piston. It is assumed that this is a lock-up clutch mechanism for a torque converter that can be locked up by being pressed against the bottom wall of the front cover and frictionally fastened.

  In addition, an annular dissimilar material sliding layer is formed on the portion of the front cover facing the friction material on the lock-up clutch piston side by a thermal spraying method.

  In this case, the thermal spraying method is not particularly limited as long as an annular dissimilar material sliding layer can be firmly fixed to a portion of the front cover facing the friction material on the lockup clutch piston side. In addition, a different material from the front cover such as cast iron or other metals, ceramics, plastic, cermet, etc. shall be used. By spraying on the front cover, a different material film is formed by thermal spraying to form an annular different material sliding layer.

  In the invention according to claim 2, the dissimilar material sliding layer is formed by thermal spraying cast iron represented by gray cast iron that is easy to handle and has excellent friction sliding properties. Clarified.

  Here, since the front cover is mainly formed by pressing a steel plate into a bottomed shallow dish shape, the inner corner curvature portion formed by the bottom wall portion and the trunk portion of the front cover is the torque converter. Stress concentration tends to occur due to hydraulic pressure. Therefore, as described in claim 3, the dissimilar material sliding layer extends from the inner surface side of the bottom wall portion of the front cover to the inner corner curvature portion formed by the inner surface of the bottom wall portion and the inner surface of the trunk portion. In order to reduce the stress concentration, it is desirable that the inner corner curvature portion is smoothly continuous.

  More preferably, the dissimilar material sliding layer has a thickness from an inner surface side of the bottom wall portion of the front cover to an inner corner curvature portion formed by the inner surface of the bottom wall portion and the inner surface of the trunk portion. By extending gradually so as to become smaller, it is assumed that the inner corner curvature portion is smoothly continuous.

  In forming the annular dissimilar material sliding layer on the front cover, the inner surface of the bottom wall portion of the front cover is formed on the portion where the dissimilar material sliding layer is to be formed. While spraying guns face each other and rotating the front cover around its axial center, spraying a material that should be a different material sliding layer from the spraying gun to the front cover eliminates imbalance in the front cover. Is desirable.

  According to the first and second aspects of the invention, the dissimilar material sliding layer having the necessary thickness can be formed only in the necessary portion of the front cover, so that the heat capacity and rigidity at the same portion are secured. The thickness and weight of the dissimilar material sliding layer can be reduced, and the lockup clutch mechanism and thus the torque converter can be reduced in size and weight. Further, since the dissimilar material sliding layer can be made relatively thin as compared with the conventional sliding member by brazing, the occurrence of unbalance of the front cover can be suppressed.

  According to the third and fourth aspects of the present invention, the dissimilar material sliding layer extends to the inner corner curvature portion of the front cover, so that the stress concentration due to the working hydraulic pressure of the torque converter at that portion can be alleviated.

  According to the invention described in claim 5, the different material sliding layer can be formed in a state where the thickness of the different material sliding layer is uniform and there is no weight imbalance.

The figure which shows more specific 1st Embodiment for implementing this invention, and is a half sectional view in the non-lock-up state of a torque converter. The principal part enlarged view of FIG. Explanatory drawing which shows the manufacturing method of the said front cover.

  1 and 2 show a more specific embodiment for carrying out the present invention, FIG. 1 shows a half sectional view of a torque converter, and FIG. 2 shows an enlarged view of a main part of FIG. Further, FIG. 3 shows an example of a method for manufacturing the front cover.

  As shown in FIGS. 1 and 2, the torque converter 1 is roughly divided into a bottomed shallow dish-shaped front cover 3 having a bottom wall portion 3 c and a cylindrical body portion 3 a, and a converter housing 2 together with the front cover 3. The circular deep dish-shaped pump impeller 4 to be formed, the same circular deep dish-shaped turbine runner 5 disposed opposite to the pump impeller 4, and the pump impeller 4 and the turbine runner 5 are disposed between the pump impeller 4 and the turbine runner 5. In addition to the wheel-shaped stator 6, the lock-up clutch piston 7 and the damper 8 are included. Both the pump impeller 4 and the turbine runner 5 have a known so-called torus structure having a plurality of blades 4a or 5a. The inner side surface of the corner portion formed by the bottom wall portion 3c of the front cover 3 and the cylindrical portion 3a is a smooth inner corner curvature portion 3b as will be described later.

  The front cover 3 and the pump impeller 4 are joined by the welded portion 2a, and as described above, the converter housing 2 is formed by both of them, and the fluid chamber of the torque converter 1 is formed therein. The The front cover 3 is connected to the crankshaft of the engine via bolts 9 welded to the outside of the front cover 3 and a drive plate (not shown). Thereby, the converter housing 2 which consists of the front cover 3 and the pump impeller 4 rotates integrally with a crankshaft. A cover boss 18 is fixed to the center of the front cover 3 by welding.

  The lock-up clutch piston 7 has a bottomed shallow dish shape having a cylindrical body portion 7a as with the front cover 3, and the front cover 3 and the turbine runner 5 are accommodated inside the front cover 3. The inner peripheral portion is fitted and supported so as to be axially displaceable with respect to the turbine hub 5b. In addition, a damper 8 is provided between the lockup clutch piston 7 and the turbine runner 5 for transmitting torque while attenuating transmission torque fluctuation from the engine side when the lockup clutch is engaged (lockup state). ing. The damper 8 includes a drive plate 8a coupled to the lockup clutch piston 7 by a rivet 10, a driven plate 8b coupled to the turbine hub 5b by the rivet 20 together with the turbine runner 5 described above, and the drive plate 8a and the driven plate 8b are composed of a plurality of torsion absorbing springs 8c interposed between the two at the overlapping portion.

  The lock-up clutch piston 7 is pressed against the front cover 3 based on the driving state such as the vehicle speed and the throttle opening, for example, and the rotation of the front cover 3 as an input from the crankshaft is made via the damper 8 and the turbine hub 5b. It has a function of transmitting directly and mechanically to the output shaft 11. An annular clutch fading 12 having a predetermined thickness is adhered and fixed to the portion of the lockup clutch piston 7 that faces the inner surface 3d of the bottom wall 3c of the front cover 3 as a friction material.

  Furthermore, a dissimilar material sliding layer 13 is formed on a portion of the inner surface 3d of the bottom wall portion 3c of the front cover 3 that faces the clutch fading 12.

  Thus, the lockup clutch piston 7 forms a lockup clutch mechanism together with a part of the front cover 3 and the clutch fading 12.

  Due to the presence of the lock-up clutch piston 7, the fluid chamber of the torque converter 1 is incomplete in two chambers, that is, a chamber (release chamber) 15 on the front cover 3 side and a chamber (apply chamber) 14 on the turbine runner 5 side. While isolated.

  The stator 6 is supported via a one-way clutch 16 so as to be rotatable only in one direction.

  FIG. 2 shows an enlarged view of a main part of the front cover 3 in FIG.

  Here, the front cover 3 is formed, for example, by press-molding a steel plate into a bottomed shallow dish shape, and faces the clutch fading 12 on the lock-up clutch piston 7 side of the inner surface 3d of the bottom wall portion 3c. The part is formed as an annular dissimilar material sliding layer 13 by a known thermal spraying method such as flame spraying using a powdered cast iron which is a material different from that of the front cover 3. .

  Specifically, the dissimilar material sliding layer 13 is sprayed from the inner surface 3d of the bottom wall portion 3c of the front cover 3 to the inner corner curvature portion (inner corner radius portion) 3b extending between the inner surface 3d and the cylindrical body portion 3a. The thickness t is, for example, 3 to 5 mm by the method, and the thickness t is gradually reduced toward the inner corner curvature portion 3b. Therefore, the dissimilar material sliding layer 13 is smoothly continuous from the inner surface 3d of the bottom wall portion 3c toward the inner corner curvature portion 3b side. Then, in order to ensure the smoothness of the surface of the dissimilar material sliding layer 13, it is subjected to mechanical processing such as cutting or grinding after thermal spraying and is cut out by about 0.5 mm, and as a result, the thickness t is 3 to 3 as described above. It is about 5 mm.

  FIG. 3 is a view showing a method of forming the annular dissimilar material sliding layer 13 on the inner surface 3d of the bottom wall portion of the front cover 3. As shown in FIG.

  In the present embodiment, for example, the front cover 3 is fixed to the main shaft of a machine tool (not shown) by chucking with the cover boss 18 as a gripping portion, and the motor 19 is started so that the front cover 3 is rotated around the axis C. It is rotated in the direction of arrow D1 together with the main shaft at a predetermined speed.

  Then, the nozzle 17a of the spray gun 17 is made to face the inner surface 3d of the bottom wall portion 3c of the front cover 3 so that the dissimilar material sliding layer 13 is melted or melted from the spray gun 17 to the front cover 3. Cast iron particles are sprayed by powder flame spraying or the like.

  The cast iron used in this case is, for example, gray cast iron, as well as carbon present in excess of the amount that can be dissolved and retained in austenite at the eutectic temperature, as described in JP-A No. 51-112440. Iron and carbon alloys that normally contain various amounts of silicon, manganese, phosphorus, and sulfur are used.

  In the lockup clutch mechanism of the torque converter 1 configured as described above, the hydraulic pressure in the converter housing 2 is controlled based on the vehicle operating state such as the vehicle speed and the throttle opening, for example. The lock-up clutch mechanism having the lock-up clutch piston 7 as a main element is controlled to switch according to the difference in hydraulic pressure between the apply chamber 14 and the release chamber 15 which are the chambers on both sides.

  For example, when the vehicle speed is relatively low, the hydraulic pressure in the release chamber 15 is greater than the hydraulic pressure in the apply chamber 14, so the clutch fading 12 does not contact the dissimilar material sliding layer 13 that is the contact surface on the front cover 3 side. When the vehicle is in a locked-up state (lock-up released state or turbine state) and the vehicle speed is increased to some extent, the hydraulic pressure in the apply chamber 14 becomes larger than the hydraulic pressure in the release chamber 15. On the other hand, the clutch fading 12 is pressed while being incomplete, and a slip state is allowed in which both slips are allowed. As the vehicle speed further increases, the differential pressure between the apply chamber 14 and the release chamber 15 increases further, so that the clutch fading 12 is frictionally fastened to the dissimilar material sliding layer 13 on the front cover 3 side with a greater force and locked. It becomes an up state.

  In the non-lock-up state, the rotation of the pump payer 4 integral with the front cover 3 is transmitted to the turbine runner 5 via the hydraulic oil between the pump payer 4 and the turbine runner 5, and the turbine hub 5 b and the spline are transmitted. It is transmitted to the coupled output shaft 11.

  On the other hand, in the lock-up state, as described above, the clutch fading 12 is pressed against the dissimilar material sliding layer 13 on the front cover 3 side and the both are frictionally fastened. Is mechanically transmitted to the output shaft 11 splined with the turbine hub 5b via the lockup clutch piston 7 and the damper 8.

  In the slip state, the clutch fading 12 is pressed against the dissimilar material sliding layer 13 on the front cover 3 side as described above, and both are brought into an incomplete frictional engagement state, and a part of the rotation of the front cover 3 is caused. Via the lock-up clutch piston 7 and the damper 8, it is mechanically transmitted to the output shaft 11 splined with the turbine hub 5b.

  As described above, according to the present embodiment, the annular dissimilar material sliding layer 13 is formed on the inner surface 3d of the bottom wall 3c of the front cover 3 by thermal spraying. 3 can be improved in rigidity and heat capacity.

  In particular, unlike the brazing type disclosed in Patent Document 1 previously cited as a prior art document, it is not necessary to cut the front cover 3 in advance, which is further advantageous in terms of improving rigidity.

  Further, since the dissimilar material sliding layer 13 extends not only to the inner surface 3d of the bottom wall portion 3c of the front cover 3 but also to the inner corner curvature portion 3b, the inner corner where the stress concentration due to the hydraulic pressure of the converter housing 2 is likely to occur. Even the curvature portion 3b can be reinforced to further improve the rigidity of the front cover 3.

  Furthermore, in the case of the conventional brazing type, the sliding member needs to have a predetermined thickness or more in order to prevent thermal deformation of the sliding member. In this embodiment, the problem of thermal deformation of the sliding member does not occur, and the dissimilar material sliding layer 13 having a necessary thickness can be formed only at a necessary portion of the front cover 3. Therefore, it is possible to reduce the thickness and weight due to the formation of the dissimilar material sliding layer 13 while ensuring the heat capacity and rigidity at the same part, and the lock-up clutch mechanism and thus the torque converter 1 can be reduced in size and weight. Can contribute.

  In addition, since the dissimilar material sliding layer 13 is formed while rotating the front cover 3 around its center, the occurrence of unbalance in the rotating direction of the front cover 3 can be suppressed.

  Furthermore, by forming the dissimilar material sliding layer 13 by spraying cast iron, in addition to wear resistance, which is a characteristic of cast iron, the friction coefficient, thermal conductivity, and high heat capacity are utilized. This can further contribute to improving the function of the cover 3.

  Here, in the present embodiment, cast iron is used as the thermal spray material for forming the dissimilar material sliding layer 13, but a material different from that of the front cover 3, such as other metal, ceramics, plastic, cermet, or the like, is used as necessary. As the thermal spraying method, a known thermal spraying method such as flame spraying or plasma spraying is appropriately selected according to the thermal spray material.

  Further, in the present embodiment, the case where a torque converter is employed as the fluid coupling has been described. However, the present invention can also be applied to a fluid coupling which is a fluid coupling having a configuration without the stator 6, and in that case, the same applies. Has an effect.

DESCRIPTION OF SYMBOLS 1 ... Torque converter 2 ... Converter housing 3 ... Front cover 3a ... Cylindrical trunk | drum 3b ... Inner corner curvature part 3c ... Bottom wall part 3d ... Inner surface 4 ... Pump impeller 7 ... Lock-up clutch piston 12 ... Clutch fading (friction material)
13 ... Dissimilar material sliding layer 17 ... Thermal spray gun C ... Axle

Claims (5)

A front cover that forms a converter housing with the pump impeller;
A lock-up clutch piston that is housed and arranged inside the front cover and that can approach and separate from the bottom wall of the front cover in the axial direction of the front cover;
An annular friction material mounted on a portion of the lockup clutch piston facing the bottom wall of the front cover,
With
A lock-up clutch mechanism of a torque converter that enables lock-up by pressing the friction material together with a lock-up clutch piston against the bottom wall portion of the front cover and frictionally fastening,
A lockup clutch mechanism for a torque converter, characterized in that an annular dissimilar material sliding layer is formed by a thermal spraying method on a portion of the bottom wall portion of the front cover facing the friction material on the lockup clutch piston side.   The lockup clutch mechanism for a torque converter according to claim 1, wherein the dissimilar material sliding layer is formed by spraying cast iron made of a material different from that of the front cover.   The front cover is formed by pressing a steel plate into a bottomed shallow dish shape, and the dissimilar material sliding layer is formed between the inner surface of the bottom wall portion of the front cover and the inner surface of the bottom wall portion and the inner surface of the trunk portion. The lock-up clutch mechanism for a torque converter according to claim 2, wherein the lock-up clutch mechanism of the torque converter according to claim 2, wherein the lock-up clutch mechanism extends to the inner corner curvature portion and smoothly continues to the inner corner curvature portion.   The dissimilar material sliding layer extends from the inner surface side of the bottom wall portion of the front cover to the inner corner curvature portion formed by the inner surface of the bottom wall portion and the inner surface of the trunk portion so that the thickness gradually decreases. 4. The lockup clutch mechanism for a torque converter according to claim 3, wherein the lockup clutch mechanism is smoothly continuous with the corner curvature portion. A method for forming an annular dissimilar material sliding layer on the front cover in the lockup clutch mechanism according to claim 1,
The spray gun is made to face the part where the different material sliding layer should be formed in the inner surface of the bottom wall portion of the front cover,
A method of manufacturing a front cover, comprising: forming a different material sliding layer by spraying a material to be a different material sliding layer from the thermal spray gun to the front cover while rotating the front cover about its axis. .

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