Patent Application
20200386278
The present invention generally relates to a core plate of a friction plate and, more specifically, to a friction plate for use in a clutch assembly of a wet friction system, and a method of making a core plate of a friction plate.
Several components of a motor vehicle powertrain may employ a wet friction system to facilitate the transfer of power from the motor vehicle's power generator (e.g., an internal combustion engine, electric motor, fuel cell, etc.) to drive wheels of the motor vehicle. A transmission, located downstream from the power generator that enables vehicle launch, gear shifting, and other torque transfer events, is one such component that may employ a wet friction system. Some form of a clutch assembly may be found throughout many different types of transmissions currently available for motor vehicle operation. A wet clutch may be utilized in a torque converter for an automatic transmission, in a multi-plate wet clutch pack for an automatic transmission or a semi-automatic dual-clutch transmission (DCT), and in a wet start clutch that may be incorporated into an automatic transmission equipped with as many as seven to ten gears as a substitute for the torque converter, to name but a few examples. Similar wet clutches may be found elsewhere in the vehicle powertrain besides the transmission.
The clutch assembly typically includes a plurality of friction plates rotatably coupled to a shaft, with the plurality friction plates being used to interlock two or more opposed, rotating surfaces in the presence of a lubricant by imposing selective interfacial frictional engagement between those surfaces. Each friction plate includes a core plate defining a bore for receiving the shaft such that each friction plate is rotatably coupled to the shaft. Each friction plate additionally includes a friction material disposed on the core plate, which effectuates the intended interlocking of frictional engagement between the plurality of friction plates. The presence of the lubricant cools and reduces wear of the friction material and permits some initial slip to occur so that torque transfer proceeds gradually, although very quickly, in an effort to avoid the discomfort that may accompany an abrupt torque transfer event (i.e., shift shock).
During operation, conventional friction plates move between an engaged position where the plurality friction plates are engaged with one another, and a disengaged position where the plurality friction plates are disengaged from one another. However, clutch assemblies including conventional friction plates often experience drag torque when the plurality of friction plates are rotating in the disengaged position, which is caused by the friction plates rotating through the lubricant. Increased drag torque reduces performance of the clutch assembly and, in turn, the wet friction system, and reduces fuel economy of the motor vehicle's power generator.
As such, there remains a need to provide an improved friction plate for a clutch assembly.
A friction plate for use in a clutch assembly of a wet friction system includes a lubricant, with the clutch assembly including a shaft, and with the friction plate including a core plate defining a bore extending along an axis and adapted to receive and be rotatably coupled to the shaft. The core plate includes an interior core surface defining the bore, and an exterior core surface radially spaced from the interior core surface with respect to the axis such that the exterior core surface surrounds the interior core surface about the axis. The core plate also includes a first clutch face extending between the interior core surface and the exterior core surface and facing a first direction along the axis, with the first clutch face having a first plane extending along the first clutch face, and a second clutch face extending between the interior core surface and the exterior core surface and facing a second direction opposite the first direction along the axis, with the second clutch face having a second plane extending along the second clutch face. The friction plate also includes a friction material disposed on at least one of the first and second clutch faces. The core plate includes a plurality of projections along the exterior core surface extending radially away from the axis. At least one of the projections extends away from the first and second planes with respect to the axis such that the first plane is disposed between the at least one of the projections and the second plane with respect to the axis, and such that the at least one of the projections is configured to provide a spring force to another friction plate of the clutch assembly during disengagement of the friction plate from the other friction plate, and to direct the lubricant axially away from the first clutch face along the axis during rotation of the core plate for limiting drag torque in the clutch assembly. A method of producing the core plate is also disclosed herein.
Accordingly, the core plate including a plurality of projections, with at least one of the projections extending away from a first and second plane with respect to an axis such that the first plane is disposed between the at least one of the projections and the second plane with respect to the axis, and such that the at least one of the projections is configured to provide a spring force to another friction plate of the clutch assembly during disengagement of the friction plate from the other friction plate, and to direct the lubricant axially away from a first clutch face along the axis during rotation of the core plate limits drag torque in the clutch assembly, which ultimately increases performance of the clutch assembly, and increases fuel economy.
Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
With reference to the Figures, wherein like numerals indicate like parts throughout the several views, a clutch assembly 20 including a friction plate 22 is generally shown in
With reference to
The friction plate 22 also includes a friction material 50 disposed on at least one of the first and second clutch faces 42, 46. Typically, the friction plate 22 includes the friction material 50 on both the first and second clutch faces 42, 46. However, it is to be appreciated that the friction plate 22 may have the friction material 50 on only one of the first and second clutch faces 42, 46. For example, when the clutch assembly 20 includes a plurality of friction plates 22, each of the friction plates 22 are disposed about the axis A such that clutch assembly 20 includes two friction plates 22 sandwiching the other friction plates 22 between one another with respect to the axis A. In such cases, each of the two friction plates 22 sandwiching the other friction plates 22 typically only have the friction material 50 on one of the first and second clutch faces 42, 46. Typically, the clutch assembly 20 includes a plurality of pressure plates 52 disposed between the friction plates 22. The plurality of pressure plates 52 help move the friction plates 22 between an engaged position, as shown in
The core plate 32 includes a plurality of projections 54 along the exterior core surface 38 extending radially away from the axis A. The plurality of projections 54 may define a plurality of notches 56 therebetween. Typically, the plurality of projections 54 are disposed 360 degrees about the axis A. At least one of the projections 54 extends away from the first and second planes FP, SP with respect to the axis A such that the first plane FP is disposed between the at least one of the projections 54 and the second plane SP with respect to the axis A, and such that the at least one of the projections 54 is configured to provide a spring force to another friction plate 22 of the clutch assembly 20 during disengagement of the friction plate 22 from the other friction plate 22, and to direct the lubricant axially away from the first clutch face 42 along the axis A during rotation of the core plate 32 for limiting drag torque in the clutch assembly 20.
Having at least one of the projections 54 extending away from the first and second planes FP, SP with respect to the axis A such that the first plane FP is disposed between the at least one of the projections 54 and the second plane SP with respect to the axis A, and such that the at least one of the projections 54 is configured to provide a spring force to another friction plate 22 of the clutch assembly 20 during disengagement of the friction plate 22 from the other friction plate 22, and to direct the lubricant axially away from the first clutch face 42 along the axis A during rotation of the core plate 32 for limiting drag torque in the clutch assembly 20 limits drag torque, also known as open pack drag, in the clutch assembly 20. Limiting drag torque in the clutch assembly 20 ultimately increases performance of the clutch assembly 20, and increases fuel economy. Specifically, the at least one of the projections 54 extending away from the first and second planes FP, SP with respect to the axis A provides a spring force to another friction plate 22 of the clutch assembly 20 as the friction plates 22 move from an engaged position, as shown in
The plurality of projections 54 may be integral, i.e., one-piece, with the core plate 32. The plurality of projections 54 may be a separate component coupled to the core plate 32, such as a ring or any other suitable component that is configured to provide a spring force to another friction plate 22 of the clutch assembly 20 during disengagement of the friction plate 22 from the other friction plate 22, and to direct the lubricant axially away from at least one of the first and second clutch faces 42, 46 along the axis A during rotation of the core plate 32. In such cases where the plurality of projections 54 is a separate component coupled to the core plate 32, the plurality of projections 54 may be coupled to the core plate 32 in any suitable manner, such as fastened or bonded. Additionally, when the plurality of projections 54 is a separate component coupled to the core plate 32, the separate component, such as the ring or any other suitable component, may be comprised of a metallic or polymeric material.
As shown in
Typically, each projection 54 of the first group of projections 60 is disposed between two projections 54 of the second group of projections 62 about the axis such that each projection 54 of the plurality of projections 54 alternates about the axis A between extending away from the first and second planes FP, SP with respect to the axis such that the first plane FP is disposed between each projection 54 of the first group of projections 60 and the second plane SP, and extending away from the first and second planes FP, SP with respect to the axis A such that the second plane SP is disposed between each projection 54 of the second group of projections 62 and the first plane FP. The alternating of each projection 54 between extending away from the first and second planes FP, SP with respect to the axis such that the first plane FP is disposed between each projection 54 of the first group of projections 60 and the second plane SP, and extending away from the first and second planes FP, SP with respect to the axis A such that the second plane SP is disposed between each projection 54 of the second group of projections 62 and the first plane FP may be referred to as having a saw tooth configuration.
In one embodiment, the first and second groups of projections 54 include all projections 54 of the plurality of projections 54. The first group of projections 60 may include one half of the plurality of projections 54, and the second group of projections 62 may include the other half of the plurality of projections 54. For example, the first group of projections 60 may include eight projections 54, and the second group of projections 62 may include eight projections 54. However, it is to be appreciated that first group of projections 60 and second group of projections 62 may include any number of suitable projections 54, such as five, six, seven, nine, ten, eleven, or twelve projections 54.
In one embodiment, the first clutch face 42 has a first friction surface 64 presented by the plurality of projections 54, and the second clutch face 46 has a second friction surface 66 presented by the plurality of projections 54. In such embodiments, the friction material 50 is disposed on at least one of the first and second friction surfaces 64, 66. The friction material 50 may be disposed on both of the first and second friction surfaces 64, 66. When the friction material 50 is disposed on both the first and second friction surfaces 64, 66 the friction material may be disposed on the first friction surface 64 of each projection 54, and on the second friction surface 66 of each projection 54. It is to be appreciated that the friction material 50 may be partially embedded in the first and second friction surfaces 64, 66, or may be disposed on the first and friction surfaces 64, 66.
The first friction surface 64 of each projection 54 of the first group of projections 60 and the first clutch face 42 adjacent the interior core surface 36 may define a first angle θ1 therebetween. Similarly, the second friction surface 66 of each projection 54 of the second group of projections 62 and the second clutch face 46 adjacent the interior core surface 36 may define a second angle θ2 therebetween. It is to be appreciated that the first and second angles θ1, θ2 may be any suitable angle for the plurality of projections to provide a spring force to another friction plate 22 of the clutch assembly 20 during disengagement of the friction plate 22 from the other friction plate 22, and to direct the lubricant axially away from the first and second clutch faces 42, 46 for reducing drag torque in the clutch assembly 20. By way of a non-limiting example, the first and second angles θ1, θ2 may be between 0.05 and 1.50 degrees, 0.10 and 1.25 degrees, and 0.15 and 0.90 degrees. The first friction surface 64 of each projection 54 of the first group of projections 60 and the first clutch face 42 adjacent the interior core surface 36 may have a curved surface joining the first clutch face 42 and the first friction surface 64. Similarly, the second friction surface 66 of each projection 54 of the second group of projections 62 and the second clutch face 46 adjacent the interior core surface 36 may have a curved surface joining the second clutch face 46 and the second friction surface 66. Typically, when the first friction surface 64 and the first friction face 42 are joined by a curved surface, the curved surface typically has concave configuration.
The core plate 32 may be comprised of any suitable material for use in the wet friction system 24. For example, the core plate 32 may be comprised of a metallic material. For example, such metallic materials that may be used include stainless steel, mild carbon steel, aluminum, and may contain surface treatments such as phosphate coating, nickel coating, anodizing, and the like. As another example, the core plate 32 may be comprised of a polymeric material.
With reference to
The method 100 further includes the step of disposing the unformed core plate 68 between a first clamp plate 72 and a second clamp plate 74 disposed about the alignment shaft 70, as indicated in box 204. The unformed core plate 68 is shown as being disposed between the first and second clamp plates 72, 74 in
The method 100 further includes the step of clamping the unformed core plate 68 between the first and second clamp plates 72, 74 to form the core plate 32 including the plurality of projections 54 along the exterior core surface 38 extending radially away from the axis A, as indicated in box 206 of
In one embodiment, as shown in
The method 100 may further include the step of disposing the friction material 50 on at least one of the first and second clutch faces 42, 46. As described above, it is to be appreciated that the friction material 50 may be disposed on both of the first and second clutch faces 42, 46, and that the friction material 50 may be disposed on the first and second friction faces 64, 66. The friction material 50 may be disposed on at least one of the first and second clutch faces 42, 46 prior to the step 202 of disposing the unformed core plate 68 about the alignment shaft 70. It is to be appreciated that the friction material 50 may be embedded in the first and second friction surfaces 64, 66, or may be disposed on the first and friction surfaces 64, 66. Typically, the core plates 32 are formed without the friction material 50. In other words, the friction material 50 is typically added to the core plate 32 after the plurality of projections 54 are formed.
In one embodiment, the step 206 of clamping the unformed core plate 68 between the first and second clamp plates 72, 74 occurs in a furnace set at any suitable temperature, such as between 800 and 1,000 degrees Fahrenheit, and the unformed core plate 68 and the first and second clamp plates 72, 74 may be in the furnace for any suitable time interval, such as between 30 to 120 minutes.
It is to be appreciated that other methods may be employed for making the core plate 32 of the friction plate 22. For example, the core plate 32 of the friction plate 22 may be formed by a stamping press, where the stamping press selectively bends at least one of the projections 54 to extend away from the first and second planes FP, SP with respect to the axis A such that the first plane FP is disposed between the at least one of the projections 54 and the second plane SP with respect to the axis A. As another example, the core plate 32 of the friction plate 22 may be formed by directing a laser at the core plate 32 to selectively bend the projections 54 to extend away from the first and second planes FP, SP with respect to the axis A such that the first plane FP is disposed between the at least one of the projections 54 and the second plane SP with respect to the axis A. When a laser is used to selectively bend at least one of the projections 54, at least a portion of the core plate 32 may be case hardened to cause at least one of the projections 52 to bend.
The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings, and the invention may be practiced otherwise than as specifically described.
