Rotary device with clutch with time-based slip and method of providing time-based slip for a rotary device

Patent metadata

Field	Value
Publication number	US-12005779-B2
Application number	US-202017593289-A
Country	US
Kind code	B2
Filing date	Mar 26, 2020
Priority date	Mar 26, 2019
Publication date	Jun 11, 2024
Grant date	Jun 11, 2024

Abstract

In one aspect, there is provided a decoupler for an accessory drive for an engine. The decoupler includes a decoupler input member and a decoupler output member. One of the decoupler input member and the decoupler output member has a clutch engagement surface. The decoupler further includes a wrap spring clutch and an isolation spring that act in series in a torque path between the decoupler input member and the decoupler output member. The wrap spring clutch has a radially inner surface and a radially outer surface. One of the radially inner and outer surfaces engages the clutch engagement surface in an interference fit with the clutch engagement surface. The decoupler further includes a volume of lubricant. During sufficiently high acceleration of the decoupler input member, there is slippage at the wrap spring clutch for a selected period of time after which the slippage stops.

First claim

What is claimed is:

1. A decoupler for an accessory drive for an engine, comprising:
a decoupler input member and a decoupler output member, wherein one of the decoupler input member and the decoupler output member has a clutch engagement surface;
a wrap spring clutch and an isolation spring that act in series in a torque path between the decoupler input member and the decoupler output member, wherein the wherein the wrap spring clutch has a radially inner surface and a radially outer surface, wherein one of the radially inner and outer surfaces engages the clutch engagement surface in an interference fit with the clutch engagement surface; and
a volume of lubricant that, in a first state of the decoupler, is positioned between said one of the radially inner and outer surfaces and the clutch engagement surface to lubricate the wrap spring clutch and the clutch engagement surface,
wherein, the amount of interference and the lubricant are selected such that, when the decoupler is in the first state and the decoupler input member is accelerated at an acceleration that is beyond a threshold acceleration, the volume of lubricant generates slippage between said one of the radially inner and outer surfaces and the clutch engagement surface for a selected period of time,
wherein, after the selected period of time, said one of the radially inner and outer surfaces engages the clutch engagement surface without slippage;
wherein the decoupler is in the first state when the engine is off, and wherein, when the engine is turned on, the decoupler input member is accelerated at a startup acceleration that is beyond the threshold acceleration, but for a period of time that is less than the selected period of time, such that there is slippage throughout when the decoupler input member is accelerated at the startup acceleration.

2. The decoupler as claimed in claim 1 , wherein the isolation spring is a helical torsion spring that is radially spaced from the wrap spring clutch by a sleeve, wherein the wrap spring clutch has a spring engagement end that is held in a carrier, and a free end, wherein the free end is positioned to transfer torque with the clutch engagement surface during acceleration of the decoupler input member relative to the decoupler output member,
and wherein the isolation spring has a first end and a second end, wherein the second end is positioned in the carrier to transfer torque with the spring engagement end of the wrap spring clutch, and the first end is positioned to transfer torque with the other of the decoupler input member and the decoupler output member,
wherein the first end of the isolation spring is positioned axially adjacent the free end of the wrap spring clutch,
wherein, during acceleration of the decoupler input member relative to the decoupler output member, there is relative movement of the free end of the wrap spring clutch relative to the carrier in a first rotational direction, and there is relative movement of the second end of the isolation spring relative to the carrier in a second rotational direction,
and wherein during acceleration of the decoupler input member relative to the decoupler output member that is greater than the threshold acceleration, radial movement of the first end of the isolation spring drives radial movement of the sleeve so as to frictionally engage the free end of the wrap spring clutch so as to cause resistance to rotational movement of the free end of the wrap spring clutch in the first rotational direction relative to the carrier.

3. The decoupler as claimed in claim 1 , wherein said one of the radially inner and outer surfaces is the radially outer surface, and the clutch engagement surface is a radially inner surface of the decoupler input member.

4. The decoupler as claimed in claim 3 , wherein the decoupler input member is a pulley and the decoupler output member is a shaft adapter that is configured for mounting to an accessory for the engine.

5. The decoupler as claimed in claim 1 , wherein the decoupler input member is a pulley and the decoupler output member is a shaft adapter that is configured for mounting to an alternator for the engine.

6. The decoupler as claimed in claim 1 , wherein the wrap spring clutch is made from a wire having cross-sectional shape with a radial dimension and an axial dimension that is greater than the radial dimension.

7. A method of controlling torque to an accessory in an accessory drive on an engine, comprising:
a) providing a decoupler including a decoupler input member and a decoupler output member, wherein one of the decoupler input member and the decoupler output member has a clutch engagement surface, and further including a wrap spring clutch and an isolation spring that act in series in a torque path between the decoupler input member and the decoupler output member, wherein the wrap spring clutch has a radially inner surface and a radially outer surface, wherein one of the radially inner and outer surfaces engages the clutch engagement surface, and further including a volume of lubricant that, in a first state of the decoupler, is positioned between said one of the radially inner and outer surfaces and the clutch engagement surface to lubricate the wrap spring clutch and the clutch engagement surface;
b) while the decoupler is in the first state and the engine is on, accelerating the decoupler input member at an acceleration that is beyond a threshold acceleration, during which the volume of lubricant generates slippage between said one of the radially inner and outer surfaces and the clutch engagement surface for a selected period of time, and then during continued acceleration beyond the threshold acceleration after the first period of time, said one of the radially inner and outer surfaces engages the clutch engagement surface without slippage; and
c) while the decoupler is in the first state and the engine is off, turning the engine on and accelerating the decoupler input member at a startup acceleration that is beyond the threshold acceleration, but for a period of time that is less than the selected period of time, such that there is slippage throughout when the decoupler input member is accelerated at the startup acceleration.

8. The method as claimed in claim 7 , wherein the isolation spring is a helical torsion spring that is radially spaced from the wrap spring clutch by a sleeve, wherein the wrap spring clutch has a spring engagement end that is held in a carrier, and a free end, wherein the free end is positioned to transfer torque with the clutch engagement surface during acceleration of the decoupler input member relative to the decoupler output member,
and wherein the isolation spring has a first end and a second end, wherein the second end is positioned in the carrier to transfer torque with the spring engagement end of the wrap spring clutch, and the first end is positioned to transfer torque with the other of the decoupler input member and the decoupler output member,
wherein the first end of the isolation spring is positioned axially adjacent the free end of the wrap spring clutch,
wherein, during acceleration of the decoupler input member relative to the decoupler output member, there is relative movement of the free end of the wrap spring clutch relative to carrier in a first rotational direction, and there is relative movement of the second end of the isolation spring relative to carrier in a second rotational direction,
and wherein during acceleration of the decoupler input member relative to the decoupler output member that is greater than the threshold acceleration, radial movement of the first end of the isolation spring drives radial movement of the sleeve so as to frictionally engage the free end of the wrap spring clutch so as

Assignees

• Litens Automotive Inc

Inventors

• Bahri Ashaad

Classifications

• F16H7/20

  Mountings for rollers or pulleys · CPC title

• F16D7/022

  with a helical band or equivalent member co-operating with a cylindrical torque limiting coupling surface · CPC title

• F16D7/021

  with radially applied torque-limiting friction surfaces (F16D7/022 takes precedence) · CPC title

• F16D3/14

  combined with a friction coupling for damping vibration or absorbing shock · CPC title

• F02B67/06

  driven by means of chains, belts, or like endless members · CPC title