초록 ▼

A narrow tolerance range slip clutch has a friction clutch and a ball ramp mechanism, with one or more springs associated with the friction clutch and ball ramp mechanism to exert a clamp load on the friction clutch and to establish a trip torque setting on the ball ramp mechanism. With a driving to

A narrow tolerance range slip clutch has a friction clutch and a ball ramp mechanism, with one or more springs associated with the friction clutch and ball ramp mechanism to exert a clamp load on the friction clutch and to establish a trip torque setting on the ball ramp mechanism. With a driving torque below a trip torque setting, there is a normal drive through the slip clutch. When the driving torque exceeds the trip torque setting, the clamp load on the friction clutch is reduced by means of a force balance between a ball ramp axial force and a clutch reaction force also proportional to input torque which are functions of the input torque and spring forces acting on the ball ramp mechanism and the friction clutch. With this force balance, the clamp load on the friction clutch is relieved sufficiently to avoid transmission of torque above the trip torque setting, with the result that there is continuous power flow through the slip clutch and after relief of the overloading, the slip clutch automatically resets itself to a full clamp load in transmitting normal torque levels.

대표청구항 ▼

1. A power-transmitting device associated with a drive input and a drive output comprising, the combination of a friction clutch and a ball ramp mechanism, the friction clutch having frictionally engaged elements drivingly connected at least one with the drive input and one with the drive output, th

1. A power-transmitting device associated with a drive input and a drive output comprising, the combination of a friction clutch and a ball ramp mechanism, the friction clutch having frictionally engaged elements drivingly connected at least one with the drive input and one with the drive output, the ball ramp mechanism having a pair of relatively movable discs with opposed ball ramps and with one of the discs in driving connection with one of the drive input and drive output and a ball positioned therebetween in said ball ramps, the combination further including spring means acting on the ball ramp mechanism and the friction clutch to urge said discs toward each other to establish a trip torque setting and to urge said elements toward each other with a compressive force to establish a drive through the friction clutch, and means operative above the trip torque setting to establish a force balance between said spring means, a force exerted by the coaction of the ball with the ball ramps and a reaction force at the friction clutch to maintain a compressive force on the friction clutch which will permit continued but limited torque transmission. 2. A power-transmitting device associated with a drive input and a drive output comprising, the combination of a friction clutch and a ball ramp mechanism, the friction clutch having frictionally engaged elements associated at least one with the drive input and one with the drive output, the ball ramp mechanism having a pair of relatively movable discs with opposed ball ramps and with one of the discs in driving connection with one of the drive input and drive output and a ball positioned therebetween in said ball ramps, the combination further including spring means acting on the ball ramp mechanism and the friction clutch to urge said discs toward each other to establish a trip torque setting and to urge said elements toward each other with a compressive force to establish a drive through the friction clutch, and means operative to reduce the compressive force of said spring means on said friction clutch elements when the ball ramp mechanism senses a torque above the trip torque setting and the ball moves relative to the ball ramps to exert a separating force on said discs. 3. A power-transmitting device as defined in claim 2 wherein said friction clutch is a cone clutch. 4. A power-transmitting device as defined in claim 2 wherein at least one of the elements of the friction clutch is directly engaged by a disc. 5. A power-transmitting device as defined in claim 2 wherein there are a pair of said ball ramp mechanisms with a central disc positioned between a pair of outer discs and said central disc having ball ramps on opposite faces coacting with opposed ball ramps on the outer discs. 6. A power-transmitting device as defined in claim 5 wherein said friction clutch is positioned intermediate said outer discs. 7. A power-transmitting device as defined in claim 6 including means interconnecting said outer discs to limit their separating movement while permitting movement thereof toward said central disc, and said spring means acting on said means to urge said outer discs toward the central disc. 8. A power-transmitting device as defined in claim 7 wherein said elements of the friction clutch are positioned between said outer discs of the ball ramp mechanism whereby said spring means exerts said compressive force thereon by acting through said outer discs. 9. A power-transmitting device as defined in claim 7 wherein an element of said friction clutch is a cone-shaped element positioned between said outer discs, and said outer discs are shaped to engage surfaces of said cone-shaped element. 10. A power-transmitting device as defined in claim 2 including a clutch housing fixed to one of the discs of the ball ramp mechanism, and said spring means comprises a pair of springs with one spring acting between a shaft of said drive input and said one disc and the other spring acting between the clutch housing and said elements of the friction clutch. 11. A power-transmitting device as defined in claim 10 wherein said means operative to reduce the compressive force of the spring means comprises a push rod which operatively engages the ball ramp mechanism and the friction clutch when the torque exceeds the trip torque setting. 12. A power-transmitting device as defined in claim 2 wherein said friction clutch is a cone clutch, and there are a pair of said ball ramp mechanisms with a central disc common to both pairs positioned between a pair of outer discs and said central disc having ball ramps on opposite faces coacting with opposed ball ramps on the outer discs, means interconnecting said outer discs to limit their separating movement while permitting movement thereof toward said central disc, an element of said friction clutch being a cone-shaped element positioned between said outer discs with said outer discs being shaped to engage surfaces of said cone-shaped element, and said spring means exerting said compressive force to establish the drive through the friction clutch by acting through said outer discs. 13. A narrow torque tolerance range slip clutch for establishing a drive connection between aligned input and output shafts comprising: a friction clutch having interfitted clutch members with at least two clutch members operatively connected one to each of the input and output shafts; a ball ramp mechanism including a pair of facing discs with opposed ball ramps in which a ball is positioned and which are caused to move apart as the ball leaves a centered position in the ball ramps; spring means acting to urge said ball ramp discs toward each other and to exert a compressive force on said interfitted clutch members. 14. A slip clutch providing a narrow tolerance torque range in a drive connection between axially aligned input and output shafts comprising, a ball ramp mechanism having a pair of spaced-apart discs with opposed ball ramps and a ball positioned thereon with one of said discs fixed to the output shaft and the other floating relative thereto, a clutch housing, a plurality of compressively engaged clutch elements with at least one element connected to the clutch housing and one element connected to the input shaft, said clutch housing being fixed to said floating disc of the ball ramp mechanism and having a pair of spaced-apart flanges spanning said clutch elements with one flange engaging a clutch element and the other flanges spaced from the clutch elements, a ball ramp load spring acting between the output shaft and the floating disc of the ball ramp mechanism, a clutch load spring acting between said other flange and one of the clutch elements, and a push rod extended between the disc fixed to the output shaft and the clutch element engaged by the clutch load spring and having a length to only contact both the last-mentioned disc and clutch element when said ball ramp discs are caused to separate by a torque in excess of a trip torque established by the force of the ball ramp load spring. 15. A narrow torque tolerance range slip clutch for establishing a drive connection between aligned input and output shafts comprising: a friction clutch having interfitted clutch members with at least two clutch members operatively connected one to each of the input and output shafts and a movable member, and spring means positioned between said movable member and said clutch members for exerting a clamp load on said clutch members axially of said shafts; a ball ramp mechanism including a pair of facing discs with opposed ball ramps in which a ball is positioned and which are caused to move apart as the ball leaves a centered position in the ball ramps; spring means engaging one of said discs urging said ball ramp plates toward each other; and said spring-engaged disc and said movable member being rigidly interconnected. 16. A slip clutch providing a torque limiting drive connection between axially aligned input and output shafts comprising: a ball ramp mechanism including a center disc connected to one of said shafts and a pair of side discs positioned one at either side of said center disc and spaced therefrom, the adjacent faces of said discs being provided with opposed ball ramps and a ball positioned in each pair of opposed ball ramps, means movably interconnecting said side discs to permit relative movement therebetween while limiting the maximum separation therebetween, a clutch pack positioned between the side discs of the ball ramp mechanism and having clutch elements some of which are keyed to said side discs and others of which are operatively connected to the other of said shafts; and spring means urging said side discs toward each other to exert a clamp load on said clutch pack and the occurrence of a certain torque level in the slip clutch resulting in said balls acting in said ball ramps to exert a force resulting in reduction of the clamp load and which with the force exerted against a ball ramp side disc by the clutch pack is in force balance with the force of said spring means. 17. A slip clutch with a narrow tolerance torque range comprising, a clutch pack having a clutch housing and plurality of interengaging clutch members operatively connected some to an input shaft and others to an output shaft, a torque-sensing ball ramp mechanism, spring means associated with the clutch housing and the ball ramp mechanism exerting a compressive force on the ball ramp mechanism and the clutch pack with a reaction force on the clutch housing, and means interconnecting said ball ramp mechanism and said clutch pack whereby at a certain torque level said ball ramp mechanism establishes a force which is operative to achieve a force balance with said spring means and said reaction force on said clutch housing in order to relieve only that portion of the force of the spring means which would cause the clutch pack to transmit an unacceptable overload.