Isolator Decoupler

Field o-f the Invention

The invention relates to an isolator decoupler, and more particularly, an isolating decoupler comprising a first torsion spring and a second torsion spring engaged between a spring carrier and a one-way clutch, the first torsion spring and the second torsion spring having a frictional engagement with the one-way ^' clutch, the first torsion spring and the second torsion spring engagable with the pulley whereby upon contact with the pulley the first torsion spring and second torsion spring will release the frictional engagement with the one-way clutch .

Background of the Invention

Diesel engines used for passenger car applications is increasing due to the benefit of better fuel economy. Further, gasoline engines are increasing compression ratios to improve the fuel efficiency. As a result, diesel and gasoline engine accessory drive systems have to overcome the vibrations of greater magnitude from crankshafts due to above mentioned changes in engines.

Due to increased crankshaft vibration plus high acceleration/deceleration rates and high alternator inertia the engine accessory drive system is often experiencing belt chirp noise due to belt slip. This will also reduce the belt operating life.

Crankshaft isolators/decouplers and alternator decouplers/isolators have been widely used for ^' engines with high angular vibration to filter out vibration in engine operation speed range. However, although a crankshaft isolator can function very well in engine running speed range; it still presents problems during engine start-up or shut-down due to the natural frequency of the isolator itself.

Representative of the art is US patent number

6083130 which discloses A serpentine belt drive system for an automotive vehicle comprising a drive assembly including an internal combustion engine having an output shaft with a driving pulley thereon rotatable about a driving pulley axis. A sequence of driven assemblies each has a driven pulley rotatable about an axis parallel with the driving pulley axis and a serpentine belt mounted in cooperating relation with the driving pulley and with the driven pulleys in a sequence which corresponds with the sequence of the driven assemblies when related to the direction of movement of the belt to cause said driven pulleys to rotate in response to the rotation of the driving pulley. The sequence of driven assemblies includes an alternator assembly including an alternator shaft mounted for rotation about a shaft axis. A hub structure is fixedly carried by the alternator shaft for rotation therewith about the shaft axis. A spring and one-way clutch mechanism couples the alternator pulley with the hub structure. The spring and one-way clutch mechanism comprises a resilient spring member separately formed from and connected in series with a one-way clutch member. The resilient spring member is constructed and arranged to transmit the driven rotational movements of the alternator pulley by the serpentine belt to the hub structure such that the alternator shaft is rotated in the same direction as the alternator pulley while being capable of instantaneous relative resilient movements in opposite directions with respect to the alternator pulley during the driven rotational movement thereof. The one- way clutch member is constructed and arranged to allow the hub structure and hence the alternator shaft to rotate at a speed in excess of the rotational speed of the. alternator pulley when the speed of the engine output shaft is decelerated to an extent sufficient to establish the torque between the alternator pulley and the hub structure at a predetermined negative level.

What is needed is an isolating decoupler an isolating decoupler comprising a first torsion spring and a second torsion spring engaged between a spring carrier and a one-way clutch,, the first torsion spring and the second torsion spring having a frictional engagement with the one-way clutch, the first torsion spring and the second torsion spring engagable with the pulley whereby upon contact with the pulley the first torsion spring and second torsion spring will release the frictional engagement with the one-way clutch. The present invention meets this need. Summary of the Invention

The primary aspect of the invention is an isolating decoupler an isolating decoupler comprising a first - torsion spring and a second torsion spring engaged between a spring carrier and a one-way clutch, the first torsion spring and the second torsion spring having a frictional engagement with the one-way clutch, the first torsion spring and the second torsion spring engagable with the pulley whereby upon contact with the pulley the first torsion spring and second torsion spring will release the frictional engagement with the one-way clutch .

Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings . The invention comprises an isolating decoupler comprising a shaft, a pulley rotationally engaged with the shaft, a coil spring ^' engaged between the pulley and a spring carrier, the spring carrier moveable relative to the shaft and pulley, a one-way clutch mounted to the shaft, a first- torsion spring and a second torsion spring engaged between spring carrier and the one-way clutch, the first torsion spring and the second torsion spring having a releasable frictional engagement with the one- way clutch, the first torsion spring and the second- torsion spring comprising adjacent parallel strands and having substantially equal diameters, the first ^' torsion spring and the second torsion spring each being engagable with the pulley, the first torsion spring or the second torsion spring will release its frictional engagement with the one-way clutch upon its engagement with the pulley.

Brief Description of the Drawings

The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.

Figure 1 is a section view of the isolating decoupler.

Figure 2 is an exploded view of the isolating decoupler.

Figure 3 is a cut away view showing how the torsion spring works in the device.

Figure 4 is a free body diagram that explains the use of two wrap springs.

Figure 5 is a perspective view of a torsion spring

30. Figure 6 is a perspective view of a torsion spring

31.

Figure 7 is a perspective view of two torsion springs .

Figure 8 is a perspective view of the spring carrier.

Figure 9 is a perspective view of both torsion springs in the spring carrier.

Detailed Description of the Preferred Embodiment This invention relates to alternator tuning devices, particularly to alternator isolating pulleys with torsional springs for isolation and/or one-way clutches for decoupling. To minimize the physical size of the spring and one-way clutch it is beneificial to have an overload feature that prevents torque in excess of a predetemined amount to be transmitted to the spring and/or one-way clutch. Excessive torque applied to either the spring or one-way clutch could cause either componet to fail. What is needed is a slip feature that permits decoupling of two locked elements when a specific torque is exceeded.

It is known that the rated peak torque of an alternator is less than the peak torque observed when starting the engine. For example, a typical automotive alternator will have a rated peak torque of 12 Nm, an inertia of 0.00030 kg m ² , and an acceleration rate at the alternator of 100,000 rad/s ² during engine starting. Using Equation 1 at engine start-up the device must be able to handle 30 Nm of torque, but will not see such a high torque during all other operating conditions .

Equation 1 T = Ιω ²

where

T = torque I = alternator inertia

ω ² = acceleration rate

To avoid use of an oversize spring and one-way clutch that can handle the starting torque the inventive device uses a wrap spring that is decoupled after the peak rated torque has been experienced.

Figure 1 is a section view of the isolating decoupler. Pulley 1 engages a belt (not shown) to drive a device such as an alternator. Pulley 1 houses a ball bearing 6 and a needle bearing 10 that allows relative motion between a shaft 12 and pulley 1 while transfering the radial load to shaft 12. Pulley 1 also contains a seal 11. Seal 11 is a rotary seal used to seal the lubricant in the device and to prevent contaminants from entering the device.

Power flows from pulley 1 to one end 21 of coil spring 2. Coil spring 2 is an elastic member that attenuates vibration and provides the isolating function of the device. The other end 22 of coil spring 2 is connected to spring carrier 5. Spring carrier 5 is made of plastic as shown, but could be made of any other suitable material as known in the art, for example, metal or phenolic. Pressed fit over spring carrier 5 is a reinforcing ring 4 that retains coil spring 2 in the radial direction. Connected to spring carrier 5 are two torsoin springs 30, 31.

Torsion springs 30, 31 have ^' the same diameter. The volutes for each torsion spring 30, 31 are parallel and thereby comprise adjacent parallel strands or wires. Torsion springs 30, 31 are also parallel in terms of their configuration between the spring carrier 5 and the one-way clutch 8, as compared to springs arranged in series. Each end of each torsion spring 30, 31 is postioned 180° out of phase from the other corresponding spring end in spring carrier 5 so that the load from torsion spring 30 is canceled out by the other torsion spring 31, see Figure 4. End 3b of torsion spring 30 engages spring carrier receiving portion 51. End 3d of torsion spring 31 engages spring carrier receiving portion 52. Receiving portion 51 on the spring carrier for the first torsion spring 30 is 180 degrees out of phase with the receiving portion 52 on the spring carrier for the second torsion spring 31.

Torsion springs 30 and 31 fractionally engage oneway clutch 8 and thereby drive one-way clutch 8. In turn, one-way clutch 8 drives shaft 12. One-way clutch 8 allows shaft 12 to decouple or- overrun when shaft 12 is spinning faster than pulley 1.

Two torsion springs 30, 31 are used to balance or counter act the radial load that is applied to the oneway clutch 8 that would otherwise be applied if only a single torsion spring was frictionally engaged with oneway clutch 8. It is well known in the art that one-way clutches should not be subject to significant radial loading in the absence of bearing supports to take the radial load, therefore the inventive device is designed to counter act the radial force that would otherwise be applied to one-way clutch 8 by a sinlge torsion spring 30.

Torsion spring 30 comprises a tang 3a that interacts with stop la on pulley 1. Tosion spring 30 is frictionally engaged with one-way clutch 8 by wrapping around the outside surface of the one-way clutch 8. The two components move together until tang 3a contacts stop la. Contact with stop la causes torsion spring 30 to be unwound, thereby increasing the diameter of the volutes, which in turn reduces the frictional engagement with oneway clutch 8. This limits the amount of torque that can be transferred from torsion spring 30 to one-way clutch 8 though the frictional connection. Limiting the maximum torque that can be transmitted by torsion spring 30 prevents spring 2 and one-way clutch 8 from being overloaded.

. Torsion spring 31 comprises a tang 3c that interacts with stop lb on pulley 1. Tosion spring 30 is

• fractionally engaged with one-way clutch 8 by wrapping around the outside surface of the one-way clutch 8. The two components move together until tang 3c contacts stop lb. Contact with stop lb causes torsion spring 31 to be. unwound, thereby increasing the diameter of the volutes, which in turn reduces the frictional engagement with oneway clutch 8. This limits the amount of torque that can be transferred from torsion spring 31 to one-way clutch 8 though the frictional connection. Limiting the maximum torque that can be transmitted by torsion spring 31 prevents coil spring 2 and one-way clutch 8 from being overloaded.

A thrust washer 9 holds one-way clutch 8 in its proper axial position when torsion springs 30 and 31 are released casuing slipping between torsion springs 30 and 31 and one-way clutch 8. Thrust washer 9 is in contact with needle bearing 10 and urges .one-way clutch 8 axially into position against spring carrier 5.

Figure 2 is ^' an exploded view of the isolating decoupler.

Figure 3 is a cut away view showing how the torsion spring works in the device. Tang 3a engages stop la on pulley 1. As torque increases, spring carrier 5 will will rotate relative to the shaft 12 as coil spring 2 deflects undedr the load being transmitted to pulley 1. Ultimately, tang 3a will conatct stop la. When this occurs, any further increase in torque will cause torsion spring 30 and 31 to "unwind", thereby releasing the frictional engagement between torsion spring 30 and 31 and the one-way clutch 8. The frictional release will allow the shaft to turn relative to the pulley, thereby reducinng the torque being transmitted to the pulley and belt.

Figure 4 is a free body diagram that explains the use of two wrap springs. "Spring- 1" is the vector representing the power being transmitted from the spring carrier 5 to torsion spring 30. "Spring 2" is the vector representing the power being transmitted from the spring carrier 5 to torsion spring 31. "Reaction 1" is the radial force exerted by torsion spring 30 on the one-way clutch 8. "Reaction 2" is the radial force exerted by torsion spring 31 on the one-way clutch 8. Reaction 1 cancels Reaction 2. Stop la on the pulley that is engagable with the torsion spring 30 is 180 degrees out of phase with the stop lb on the pulley that is engagable with the torsion spring 31.

Figure 5 is a perspective view of a torsion spring

30.

Figure 6 is a perspective view of a torsion spring 31. .

Figure 7 is a perspective view of two torsion springs. Tang 3b is 180 degress out of phase with tang 3d. Tang 3a is 180 degrees out of phase with tang 3c. The volutes for each spring are adjacent and parallel. Each volute from torsio spring 30 is interleaved with the adjacent volute from the other torsion spring 31.

Figure 8 is a perspective view of the spring carrier. Receiving portion 51 receives tang 3b. Receiving portion 52 receives tang 3d. Figure 9 is a perspective view of the torsion springs in the spring carrier. An end of coil spring 2 bears upon surface 53.

Although a form of the invention has been described herein, ^' it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein.