Patent Description:
It is known to provide an over-running decoupler in a drive system to permit one or more driven components in the drive system to decouple to reduce or eliminate torsional loads occurring as a result of the deceleration of a source of rotary power relative to the driven component. Exemplary over-running decouplers are disclosed in <CIT> , <CIT>, <CIT> and <CIT> and employ Serial Nos. <CIT> , <CIT>, <CIT>and <CIT> and employ a torsionally resilient coupling between a decoupler input member and a decoupler output member.

We have noted that operation of an over-running decoupler under some load conditions can cause the torsionally resilient coupling of the over-running decoupler to vibrate at a natural frequency (i.e., resonate), which can significantly reduce the operating life of the over-running decoupler. Resonance in the torsionally resilient coupling may be brought about through the torsional load produced by a driven accessory, through torsional vibrations input to the drive system from a source of rotary power or combinations thereof. Accordingly, there remains a need in the art for a method for attenuating or inhibiting resonance in an over-running decoupler, as well as for an over-running decoupler that can attenuate or inhibit resonance in the torsionally resilient coupling located between the decoupler input member and the decoupler output member.

Further, a coil spring for an over-running spring clutch is described in <CIT>. A spring clutch and a decoupler is described also in <CIT>. Additionally, further decouplers are disclosed in <CIT>, <CIT>, and <CIT>.

In particular, it is provided a method defined in claim <NUM>. In the following there may be described some decouplers. However, the scope of protection is defined by the claims.

An over-running decoupler that is configured to transmit rotary power between a rotary member and a hub. The over-running decoupler includes a one-way clutch having a clutch spring, a carrier that is coupled to the clutch spring and at least one spring that resiliently couples the carrier to the hub. The method includes: establishing a desired fatigue life of the at least one spring; establishing a design deflection of the at least one spring during resonance, wherein deflection of the at least one spring at the design deflection during resonance does not reduce a fatigue life of the at least one spring below the desired fatigue life; and preventing resonance in the overrunning decoupler by controlling a maximum deflection of the at least one spring such that the maximum deflection is less than or equal to the design deflection.

The over-running decoupler may include a one-way clutch having a clutch spring, a carrier that is coupled to the clutch spring and at least one spring that resiliently couples the carrier to the hub. The method includes: establishing a desired fatigue life of the at least one spring; establishing a design deflection of the at least one spring during resonance, wherein deflection of the at least one spring at the design.

The over-running decoupler includes a hub, a rotary member and a one-way clutch between the hub and the rotary member. The one-way clutch includes a carrier, a clutch spring and one or more springs disposed between the carrier and the hub. The clutch spring has a first end, which is engaged to the carrier, and is configured to be drivingly coupled to the rotary member. The method includes: operating the drive system under a first set of operating conditions to cause coupling of the clutch spring to the rotary member to facilitate transmission of torque through the over-running decoupler; and decoupling the over-running decoupler in response to deflection of the at least one spring by an amount that is greater than or equal to a predetermined spring deflection. The predetermined spring deflection is selected to inhibit onset of a resonant condition in the at least one spring.

The over-running decoupler includes a clutch having a clutch spring, a carrier that is coupled to the clutch spring and at least one spring that resiliently couples the carrier to the hub. The method includes: establishing a desired fatigue life of the at least one spring; establishing a design torque that may be transmitted through the at least one spring during resonance, wherein transmission of the design torque through the at least one spring during resonance does not reduce a fatigue life of the at least one spring below the desired fatigue life; and preventing resonance in the over-running decoupler by controlling a maximum torque transmitted through the decoupler such that the maximum torque is less than or equal to the design torque.

There may be an overrunning decoupler having a rotary member, a hub, a one-way clutch that is disposed between the hub and the rotary member, and a resonance-inhibiting clutch. The one-way clutch includes a spring carrier, a helical wrap spring and a torsionally resilient coupling between the spring carrier and the hub. The helical wrap spring includes a plurality of coils that are engaged to the rotary member, a first end and a second end. The first end of the helical wrap spring is drivingly engaged to the spring carrier. The resonance-inhibiting clutch is configured to cause the one-way clutch to disengage the rotary member when a deflection of the torsionally resilient coupling exceeds a predetermined deflection.

It should be understood that the description and specific examples are intended for purposes of illustration only and are not.

Similar or identical elements are given consistent identifying numerals throughout the various figures.

With reference to <FIG> of the drawings, an over-running decoupler constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral <NUM>. The particular over-running decoupler <NUM> illustrated is particularly suited for use with a driven device <NUM>, such as an alternator or a supercharger, in a drive system <NUM> that employs an endless power transmitting element <NUM>, such as a belt or a chain, from a source of rotary power <NUM>, such as an engine or a transmission. Those of skill in the art will appreciate that the over-running decoupler <NUM> could be configured for use in another type of drive system (e.g., a drive system employing gears) and/or that the over-running decoupler <NUM> could be employed to transmit rotary power from a drive shaft <NUM> into the drive system as shown in <FIG>. Accordingly, it will be appreciated that the teachings of the present disclosure have application in a crankshaft decoupler, similar to those which are disclosed in <CIT> and <CIT>, the disclosures of which are hereby incorporated by reference as if fully set forth in detail herein.

With reference to <FIG> and <FIG>, the over-running decoupler <NUM> can include a one-way clutch <NUM>, a rotary member <NUM>, a hub <NUM>, and a resonance-inhibiting clutch <NUM>. Except as described herein, the one-way clutch <NUM>, the hub <NUM> and the rotary member <NUM> can be configured in the manner described in <CIT> and/or <NUM>/<NUM>,<NUM>.

The one-way clutch <NUM> can comprise a resilient torque transmitting coupling <NUM>, a clutch spring carrier <NUM> and a clutch spring <NUM>. The resilient torque transmitting coupling <NUM> is configured to torsionally resiliently couple the clutch spring carrier <NUM> and the hub <NUM> and can comprise one or more springs. In the particular example provided, the resilient torque transmitting coupling <NUM> comprises a single helical torsion spring <NUM> that is disposed concentrically about the rotary axis <NUM> of the over-running decoupler <NUM>, but it will be appreciated that other torsionally-compliant couplings could be employed, such as two or more arcuate coil compression springs as disclosed in <CIT>. The torsion spring <NUM> can be formed of an appropriate spring wire with a desired cross-sectional shape (e.g., round, square, rectangular) and can have ends that can be ground or unground. In the particular example provided the torsion spring <NUM> has closed ends <NUM> that are not ground.

With reference to <FIG> and <FIG>, the clutch spring carrier <NUM> can be torsionally coupled to the resilient torque transmitting coupling <NUM>, as well as engaged to the clutch spring <NUM>. In the particular example provided, the clutch spring carrier <NUM> comprises a helical raceway <NUM>, which is configured to abut a corresponding one of the ends <NUM> of the torsion spring <NUM>, an abutment <NUM>, and a clutch spring groove <NUM>. The abutment <NUM> can be configured to abut an axial end face <NUM> of the wire that forms the torsion spring <NUM> when the end <NUM> of the torsion spring <NUM> is abutted against the helical raceway <NUM>. The clutch spring groove <NUM> can extend from an outer circumferential surface <NUM> of the clutch spring carrier <NUM> into a radially interior portion of the clutch spring carrier <NUM> and can terminate at a clutch spring abutment <NUM>.

The clutch spring <NUM> can be formed of a spring wire material and can comprise a first end <NUM>, a second end <NUM> and a plurality of helical coils <NUM> between the first and second ends <NUM> and <NUM>. The spring wire material can have a desired cross-sectional shape, such as square, rectangular or round, and can be uncoated (i.e., bare) or coated with an appropriate plating and/or coating. Moreover, a lubricant, such as a grease lubricant, can be employed on the helical coils <NUM> of the clutch spring <NUM>. The first end <NUM> can be received into the clutch spring groove <NUM> in an axial direction and can cooperate with the clutch spring groove <NUM> such that the first end <NUM> is retained to the clutch spring carrier <NUM> in radial and circumferential directions. Moreover, an axial end <NUM> of the wire that forms the first end <NUM> can abut the clutch spring abutment <NUM> so that rotary power may be transmitted between the spring carrier <NUM> and the clutch spring <NUM> (i.e., from the spring carrier <NUM> to the clutch spring <NUM> or from the clutch spring <NUM> to the spring carrier <NUM>) via contact between the clutch spring abutment <NUM> and the axial end <NUM> of the first end <NUM>.

Returning to <FIG> and <FIG>, the rotary member <NUM> can have an external surface <NUM>, which is shaped or otherwise configured to transmit rotary power in a particular drive system, and an internal cylindrical surface <NUM>. In the example provided, the rotary member <NUM> is a pulley with an external surface that is configured to engage a poly-vee belt, but it will be appreciated that the rotary member <NUM> could be configured with a different pulley configuration, or with the configuration of a roller, a friction roller, a sprocket or a gear, for example. The internal cylindrical surface <NUM> can be sized to frictionally engage the helical coils <NUM> of the clutch spring <NUM>. In the particular example provided, the helical coils <NUM> of the clutch spring <NUM> engage the internal cylindrical surface <NUM> with an interference fit.

With reference to <FIG> and <FIG>, the hub <NUM> can be torsionally coupled to the resilient torque transmitting coupling <NUM> and can include a head or flange portion <NUM> and a shank portion <NUM>. In the particular example provided, the flange portion <NUM> comprises a helical raceway <NUM>, which is configured to abut a corresponding one of the ends <NUM> of the torsion spring <NUM> and an abutment <NUM> that can be configured to abut an axial end face <NUM> of the wire that forms the torsion spring <NUM> when the end <NUM> of the torsion spring <NUM> is abutted against the helical raceway <NUM>. The shank portion <NUM> can be configured to be coupled to an input member of a driven accessory <NUM> (<FIG>) or to an output member <NUM> (Fig. 1A) of a source of rotary power through any appropriate means, such as an interference fit, a mating spline or toothed geometry, threads, threaded fasteners, keys, etc., such that the hub <NUM> will rotate with the input member of the accessory or the output member of power source. The hub <NUM> may include one or more features that aid in the installation of the over-running decoupler <NUM>, such as a hex recess <NUM> that can be employed to hold or turn the hub <NUM> relative to the input member of the accessory or the output member of power source. The shank portion <NUM> can be received through the one-way clutch <NUM> such that the clutch spring carrier <NUM> is rotatably disposed thereon.

A thrust washer <NUM> can be fixedly coupled to the shank portion <NUM> to axially retain the one-way clutch <NUM> to the hub <NUM>. In the particular example provided, the thrust washer <NUM> can also maintain the torsion spring <NUM> in an axially compressed state. The thrust washer <NUM> and the clutch spring carrier <NUM> can be configured to cooperate with one another as is disclosed in <CIT> to inhibit relative rotation between the helical raceway <NUM> (<FIG>) of the clutch spring carrier <NUM> and the corresponding end <NUM> of the torsion spring <NUM>.

Bearings and/or bushings can be employed to rotatably support the rotary member <NUM> on the hub <NUM>. In the particular example provided, a bushing <NUM> can be disposed between the flange portion <NUM> and the rotary member <NUM>, while a sealed or unsealed bearing assembly <NUM> employing bearing balls or rollers can be disposed between the shank portion <NUM> and the rotary member <NUM>. One or more seals or shields <NUM> can also be provided between the rotary member <NUM> and the shank portion <NUM> to inhibit the ingress of dust, debris and moisture into the interior of the over-running decoupler <NUM>, as well as to inhibit the egress of any lubricant on the helical coils <NUM> of the clutch spring <NUM> from the interior of the over-running decoupler <NUM>.

With renewed reference to <FIG> and <FIG>, when rotary power is to be transmitted through the over-running decoupler <NUM>, relative rotation between the rotary member <NUM> and the hub <NUM> in a first rotational direction tends to cause the clutch spring <NUM> to uncoil such that its outer circumferential surface <NUM> grippingly engages the internal cylindrical surface <NUM> of the rotary member <NUM> to thereby enable the transmission of rotary power through the over-running decoupler <NUM>. If the rotational inertia of an object (i.e., the driven accessory in <FIG> or the drive system in <FIG>) is sufficiently high to cause relative rotation between the rotary member <NUM> and the hub <NUM> in a second, opposite rotational direction by a sufficient amount, the clutch spring <NUM> will tend to coil more tightly such that the rotary member <NUM> and hub may rotate independently of one another.

The resonance-inhibiting clutch <NUM> can comprise any means for disengaging the one-way clutch <NUM> when rotary power is transmitted through the over-running decoupler <NUM> to limit deflection of the resilient torque transmitting coupling <NUM>. In the particular example provided, the resonance-inhibiting clutch <NUM> comprises the second end <NUM> of the clutch spring <NUM> and a clutch feature <NUM> formed on the flange portion <NUM> of the hub <NUM>.

The second end <NUM> of the clutch spring <NUM> can extend away from the helical coils <NUM> in a desired direction. In the particular example provided, the second end <NUM> extends parallel to the rotary axis <NUM> of the over-running decoupler <NUM> in a tubular zone <NUM> defined by the helical coils <NUM>. It will be appreciated, however, that the second end <NUM> could extend in another direction, such as radially inwardly or radially outwardly.

The clutch feature <NUM> can comprise a clutch member <NUM> that can engage the second end <NUM> of the clutch spring <NUM> to cause the clutch spring <NUM> to coil tighter and thereby disengage the internal cylindrical surface <NUM> in response to deflection of the resilient torque transmitting coupling <NUM> by a predetermined amount. In the particular example provided, an arc-shaped window or aperture is formed in the flange portion <NUM> and the clutch member <NUM> is formed or defined by a side of the aperture. The second end <NUM> of the clutch spring <NUM> can be disposed within the aperture when rotary power is transmitted through the over-running decoupler <NUM> and the clutch member <NUM> can rotate toward and away from the second end <NUM> of the clutch spring <NUM> as deflection of the resilient torque transmitting coupling <NUM> increases and decreases, respectfully. As noted above, deflection of the resilient torque transmitting coupling <NUM> at a predetermined design deflection will result in contact between the clutch member <NUM> and the second end <NUM> that causes the clutch spring <NUM> to coil more tightly and thereby disengage the rotary member <NUM>. <FIG> illustrates the relative positioning of the second end <NUM> and the clutch member <NUM> when the deflection of the resilient torque transmitting coupling <NUM> is at a given magnitude that is less than the predetermined amount, whereas <FIG> illustrates the relative positioning of the second end <NUM> and the clutch member <NUM> when the deflection of the resilient torque transmitting coupling <NUM> is at a magnitude that is equal to the predetermined amount. It will be appreciated that depending on the configuration of the clutch spring <NUM> and the magnitude of the predetermined amount of deflection of the resilient torque transmitting coupling <NUM>, more or less tightening (coiling) of the clutch spring <NUM> may be required to cause the clutch spring <NUM> to disengage the internal cylindrical surface <NUM> than that which is illustrated in <FIG>.

With reference to <FIG>, plots depicting various aspects of the operation of an alternator driven through a prior art over-running decoupler are illustrated. Plot <NUM> represents the rotational speed of the pulley of the prior art over-running decoupler as a function of time, plot <NUM> represents the voltage of the alternator field as a function of time, and plot <NUM> represents the rotational speed of the hub of the prior art over-running decoupler as a function of time. Although the testing that produced these plots was performed on a test bench, it should be appreciated that the testing was configured to simulate the driving of the alternator through a front engine accessory drive of the type that is commonly employed in automotive vehicles. In this regard, we note that while the change in rotational speed of the pulley may seem large, it should be appreciated that the diameter of the alternator pulley is relatively small as compared with the crankshaft pulley so that relatively small variances in engine rotational speed are magnified by an amount that is approximately related to a ratio of the circumference of the crankshaft pulley to the circumference of the alternator pulley.

Absent other torsional inputs, the prior art over-running decoupler is configured to attenuate the effect on the hub of the oscillation in the speed of the pulley and as such, one would have expected the rotational speed of hub to have oscillations having peak-to-peak variation of a smaller magnitude than the magnitude of the peak-to-peak variation in the rotational speed of the pulley.

In plot <NUM>, sudden changes in the magnitude of the alternator field voltage occur when the regulator of the alternator switches off or on. Since the torque required to rotate the alternator is related to the alternator field voltage, the switching off and on of the alternator produces sudden changes in the torsional loading of the over-running decoupler. The torsional vibration input to the prior over-running decoupler via the pulley and the torsional load input to the prior over-running decoupler via the hub combine to drive the torsionally resilient coupling into resonance as is shown in <FIG>, which illustrates the angular displacement of the hub relative to the pulley. The dashed horizontal lines in <FIG> depict the upper and lower bounds of the angular displacement for a given cycle as being approximately <NUM> degrees over a <NUM> second interval.

Plots depicting various aspects of the operation of an alternator driven through the over-running decoupler <NUM> (<FIG>) are illustrated in <FIG>. In <FIG>, plot <NUM> represents the rotational speed of the rotary member <NUM> (<FIG>) as a function of time, plot <NUM> represents the voltage of the alternator field as a function of time, and plot <NUM> represents the rotational speed of the hub <NUM> (<FIG>) as a function of time. In <FIG>, the plot depicts the angular displacement of the hub <NUM> (<FIG>) relative to the rotary member <NUM> (<FIG>). The dashed horizontal lines in <FIG> depict the upper and lower bounds of the angular displacement for a given cycle as being approximately <NUM> degrees over a <NUM> second interval. As with the above-described example, the testing that produced these plots was performed on a test bench under conditions identical to that which were employed to generate the plots associated with <FIG>. As shown in <FIG>, however, the over-running decoupler <NUM> (<FIG>) is not in resonance.

With renewed reference to <FIG> and <FIG>, it will be appreciated that a method is provided herein in for the operation of a drive system having an over-running decoupler with a resilient torque transmitting coupling. More specifically, the drive system can be operated under a first set of operating conditions to cause coupling of the one-way clutch <NUM> to the rotary member <NUM> to facilitate transmission of torque through the over-running decoupler <NUM>; the over-running decoupler can be decoupled in response to deflection of the resilient torque transmitting coupling <NUM> in the one-way clutch <NUM> by an amount that is equal to a predetermined deflection that is selected to inhibit onset of a resonant condition in the resilient torque transmitting coupling <NUM>.

A method is also provided herein for producing an over-running decoupler constructed in accordance with the teachings of the present disclosure (i.e., a non-resonating over-running decoupler). The method can comprise: establishing a desired fatigue life of the resilient torque transmitting coupling <NUM> (or the over-running decoupler <NUM>); establishing a design deflection of the resilient torque transmitting coupling <NUM>; and preventing resonance in the resilient torque transmitting coupling <NUM> by controlling a maximum deflection of the resilient torque transmitting coupling <NUM> such that the maximum deflection experienced by the resilient torque transmitting coupling <NUM> is less than or equal to the design deflection.

It will be appreciated that the desired fatigue life of the resilient torque transmitting coupling <NUM> may be established in any number of ways, such as through analytical means, experiment, choice, or combinations thereof. Typically the over-running decoupler <NUM> would be required to survive a predetermined regimen or systematic plan involving a predetermined quantity of test or operating cycles. For example, an over-running decoupler employed in a front engine accessory drive of an automotive vehicle may be required to survive a test regimen comprising a predetermined quantity of engine starts, such as <NUM>,<NUM> engine starts. A more sophisticated test regimen may include a first quantity of engine starts, a second quantity of engine idle segments (simulating the idling of the engine of the vehicle for a predetermined quantity of time), a third quantity of acceleration segments (simulating the acceleration of the engine of the vehicle over a predetermined quantity of time and at a predetermined rate), and a fourth quantity of deceleration segments (simulating the deceleration of the engine of the vehicle over a predetermined quantity of time and at a predetermined rate). In such situation, it may be desirable to employ an analytical means, such as simulation software, to initially design the resilient torque transmitting coupling <NUM>, then modify the resilient torque transmitting coupling <NUM> in view of criteria involving the cost or manufacturability of the torque transmitting device (e.g., the decoupler assembly <NUM>), and thereafter modify the resilient torque transmitting coupling <NUM> in response to data collected during testing. Alternatively, the desired fatigue life may established simply through choice, for example through the copying of a resilient torque transmitting coupling <NUM> in a non-resonating over-running decoupler known to have a desired fatigue life, or the choosing of a non-resonating over-running decoupler from one or more non-resonating over-running decouplers based on at least one of an inertia of the device or devices that are to be driven by the non-resonating over-running decoupler and a peak torque to drive the device or devices that are to be driven by the non-resonating over-running decoupler.

The design deflection is a deflection that the resilient torque transmitting coupling <NUM> may experience during resonance without reducing the fatigue life of the resilient torque transmitting coupling below the desired fatigue life. The design deflection is not necessarily the maximum deflection and may be established in any number of ways, such as through analytical means, experiment, choice or combinations thereof. For example, the design deflection may be set or chosen at a level that is below the maximum deflection that the resilient torque transmitting coupling <NUM> may experience during resonance without reducing the fatigue life of the resilient torque transmitting coupling <NUM> below the desired fatigue life. Alternatively, the design deflection may be established simply through choice, for example through the copying of operational or physical characteristics from a non-resonating over-running decoupler known to have a desired fatigue life.

As deflection of the resilient torque transmitting coupling <NUM> is directly related to the amount of torque that is transmitted through the resilient torque transmitting coupling <NUM>, it will be appreciated that the design deflection can be sized large enough to ensure that the component or components receiving rotary power through the non-resonating over-running decoupler may be driven under all circumstances. For example, it may be desirable in some situations to establish a peak torque of the device or devices that are to receive rotary power through the non-resonating over-running decoupler and to establish that the deflection of the resilient torque transmitting coupling <NUM> when transmitting the peak torque is less than the design deflection.

Claim 1:
A method for producing an over-running decoupler (<NUM>) that is configured to transmit rotary power between a rotary member (<NUM>) and a hub (<NUM>), the over-running decoupler (<NUM>) comprising the rotary member (<NUM>), the hub (<NUM>), a one way clutch (<NUM>) disposed between the hub (<NUM>) and the rotary member (<NUM>) and a resonance inhibiting clutch (<NUM>), wherein the one way clutch (<NUM>) comprises a resilient torque transmitting coupling (<NUM>) wherein the over-running decoupler (<NUM>) is adapted that rotary power is transmitted between the rotary member (<NUM>) and the hub (<NUM>), during relative rotation of the rotary member (<NUM>) and the hub (<NUM>) in a first direction, and to decouple the rotary member (<NUM>) and the hub (<NUM>) during relative rotation of the rotary member (<NUM>) and the hub (<NUM>) in a second direction which is opposite to the first direction, the method comprising:
establishing a desired fatigue life of the resilient torque transmitting coupling (<NUM>);
establishing a design deflection of the resilient torque transmitting coupling (<NUM>); and
characterised in preventing resonance in the resilient torque transmitting coupling (<NUM>) by controlling a maximum deflection of the resilient torque transmitting coupling (<NUM>) such that the maximum deflection experienced by the resilient torque transmitting coupling (<NUM>) is less than or equal to the design deflection.