GB2564410A

GB2564410A - Elastomeric torsional isolator

Info

Publication number: GB2564410A
Application number: GB1710911.7A
Authority: GB
Inventors: Harry Colford Terence
Original assignee: Terence Colford Consulting
Current assignee: Terence Colford Consulting
Priority date: 2017-07-06
Filing date: 2017-07-06
Publication date: 2019-01-16
Also published as: GB2564410A9; GB201710911D0

Abstract

A torsional vibration isolator for attenuating crankshaft front-end vibration, and a powertrain system or vehicle incorporating such an isolator are provided. The torsional vibration isolator 21 comprises at least two springs 1a, 1b in series, the springs being rigidly attached together via an intermediate plate 4, and being arranged as either bush construction springs in series, or circular sandwich springs in series. The spring 1a is connected to a hub 3, and the spring 1b is connected to a pulley 2. The springs 1a, 1b may be formed from resilient elastomeric material. The vibrational isolator can be typically located between a crankshaft (not illustrated) and a front-end-accessory-drive (FEAD) belt, the belt being located on the pulley 2, and attenuates torsional vibration therebetween.

Description

Title

TORSIONAL VIBRATION ISOLATOR FOR ATTENUATING CRANKSHAFT FRONT-END VIBRATION

Invention

The invention relates to a torsion vibration isolator comprising a two-rate stiffness elastic device for attachment but not exclusively, to crankshaft between crankshaft and FEAD belt. The purpose of device is to attenuate or eliminate vibration transfer between the crankshaft and FEAD belt. Where the need arises, the device shall also attenuate or eliminate vibration transfer between FEAD belt and crankshaft. The nature of vibration to be attenuated may be continuous or transient, may be cyclic or irregular, may occur at sub-idle engine speeds, idle or low engine speeds or high engine speeds.

To reduce the magnitude and severity of vibration within the crankshaft, the isolator device may also include a torsional vibration damper (TVD) as an integral part of the device. The TVD may be of tuned elastomeric or viscous construction.

Summary

The proposed isolator device is composed of a single piece composite body comprising an outer pulley, an inner hub and an intermediate two rate elastomer isolation spring comprising a preliminary torsional stiffness pipette portion and a primary torsional stiffness pipette portion (sketch 1). A single piece pulley-hub spring composite body is preferred but not mandatory as it could comprise assembled components either permanently attached or temporary attached.

The hub is extended to provide the isolator with structural strength compliance and a means of assembly containment. The centre of hub defines the principle axis of rotation for the isolator. The hub is further extended to locate and support axial and radial slip-bearings (or friction bearings) and provide structural stability to those bearing components (sketch 2). The inclusion of axial bearings is preferred but not mandatory. The hub is attachable to a typical rotatable shaft, for example but not exclusively, a crankshaft or driveshaft, and has integral a means of attachment. The pulley has freedom to rotate about the hub's principle axis via a radial bearing and is constrained by the two torsionally resilient pipette elastomer springs. These pipette elastomer springs may be described as a) a Preliminary pipette spring and b) a primary pipette spring. The preliminary and primary pipette springs are arranged in series via an intermediate plate and thereby resist torque loading between hub and pulley and allow controlled torsional displacement according to and defined by stiffness rates and stiffness tolerance bands that are applied. The primary spring (Pipette 2) will typically, but not exclusively, have a significantly higher stiffness than the preliminary spring (Pipette 1). It is a feature of the two-rate stiffness design such that the initial (transitional) torsional spring rate (Kt Nm/°) will be the series sum of Ktpjpettei and Ktpjpette2- The amount of torsional displacement of the preliminary spring is controlled according to the invention to a predetermined angle and movement of the intermediate plate is arrested by contact with the hub via a buffer control if necessary. Buffer control is preferred but is not mandatory. Following transitional torsional stiffness arrest the continuance of torsional stiffness will be Ktpjpette2 via primary spring.

Description

Isolator (21) according to Fig.l comprises Inner Hub (3) for connection to rotary shaft, or crankshaft, or intermediate connecting flange or hub. Hub (3) is connected via bonding/adhesive or other to an elastic member, preferably pipette or sleeve (la). Pipette (la) is connected, in series, via bonding/adhesive or other to an intermediate plate (4) which is attached, in series, via bonding/adhesive or other to a second elastic member, preferably pipette or sleeve (lb). Pipette (lb) is connected, in series, via bonding/adhesive or other to a Pulley (2).

Isolator (21) according to Fig.2 has degrees of freedom constrained such that Pulley (2) is prevented from moving radially in translational direction perpendicular in relation to main rotational axis by a radial bearing (6). The Pulley (2) is supported via radial bearing (6) by structural hub (7). Pulley (2) may contain a single belt vee or an extended number of vee's (polyvee) or alternative belt drive configuration, which engages with suitable FEAD belt driving accessories. Tension loads within FEAD belt can be resisted radially by virtually of radial load transferred through pulley (2) via radial bearing (6) to structural hub (7). Radial bearing (7) permits torsional movement of pulley about the main rotational axis of isolator.

Isolator (21) according to Fig.2 has degrees of freedom constrained such that Pulley (2) is prevented from moving axially in translational direction parallel in relation to main rotational axis by two axial bearings (5a & 5b). Axial bearing (5a) accedes torsional movement of pulley (2) about the main rotational axis of isolator and is supported by an axial support plate (8). Axial bearing (5b) accedes torsional movement of intermediate plate (4) about the main rotational axis of isolator and is supported by an axial structural hub (7).

Isolator (21) according to Fig.2 has hub (3), structural hub (7) and axial support plate (8) rigidly connected together and attached by screws or welding or rivets or adhesive or other.

Pulley (2) is free to move torsionally with resistance from pipette elastomers (la & lb) acting as elastic members in series relative to Hub (3).

Isolator (21) according to Fig.3 comprising hub (3) and pulley (2) interposed by preliminary elastomer pipette (la), intermediate plate (4) and primary elastomer pipette (lb) arranged in series. Rigidly connected to intermediate plate (4) is a displacement controller (22) via means of screws or welding or rivets or adhesive or other.

Distributed around the inner diameter of displacement controller (22) are a series of inwardly projecting ridges, for example four ridges, distributed around the inner diameter as indicated in cutaway section drawing Fig. 4. In combination, outwardly projecting ridges of corresponding number are disposed around an adjacent diameter of hub (3). At a predetermined torsional angle (φ) when the intermediate plate (4) and attached displacement controller (22) are rotated then ridges located on displacement controller will engage with ridges in structural hub (7) to inhibit further rotation thereby preventing further relative movement between Hub (3) and intermediate plate (4).

The inwardly projecting ridges of displacement controller (22) may have side faces bonded to a softer material or elastomer material (23), in order to dampen the harshness of contact, according to Fig. 4.

Pulley (2) within isolator assembly according to Fig.3, comprising isolator (21), radial bearing (6), axial bearings (5a & 5b), structural hub (7), axial support plate (8) and displacement controller (22), is free to move torsionally with resistance from pipette elastomers (la & lb) acting as elastic members in series. At a predetermined torsional angle (φ) when the intermediate plate (4) and attached displacement controller (22) are rotated then ridges located on displacement controller will engage with ridges in structural hub (7) to inhibit further rotation thereby preventing further relative movement in preliminary elastomer, pipette (la) and between Hub (3) and intermediate plate (4).

The primary elastomer, pipette (lb) and pulley (2) are free to continue torsional movement. Thus a 2-rate torsional stiffness characteristic is created according to graph in Fig. 6. A torsional damper may be included within the product as seen by example in Fig.5.

Diagrams

Sketch 1/ Fig. 1 - Hub (3) connected to elastomer pipette (la), connected to an intermediate plate (4), connected in series to elastomer pipette (lb), connected in series to a pulley (2).

Sketch 2/ Fig. 2 - Hub (3) rigidly connected to structural hub (7) and axial support plate (8). Hub (3) connected to elastomer pipette (la), connected to an intermediate plate (4), connected in series to elastomer pipette (lb), connected in series to a pulley (2). Pulley (2) is constrained by radial bearing (6) and axial bearings (5a & 5b) thus allowing rotational movement about main rotational axis of isolator (21). Rotational movement of pulley (2) is resisted by elastomer springs (5a and 5b) arranged in series and interposed between pulley (2) and Hub (3).

Sketch 3 / Fig. 3 - Isolator (21) assembled with radial bearing (6), axial bearings (5a & 5b), structural hub (7), axial support plate (8) and displacement controller (22).

Sketch 4 / Fig. 4 - Cut away view of isolator (21) assembled with radial bearing (6), axial bearings (5a & 5b), structural hub (7), axial support plate (8) and displacement controller (22), showing buffer pads (23) on inwardly projecting ridges of displacement controller (22).

Sketch 5 / Fig. 5 - Example of isolator structural hub (7) with torsional damper, elastomer (31) and inertia ring (32).

Sketch 6/ Fig. 6 - Graph exhibiting typical 2-rate stiffness characteristic of torsional vibration isolator.

Claims

1. A two-rate torsional stiffness isolator comprising at least two springs in series which are rigidly and/or permanently attached together via an intermediate plate with springs constructed and arranged in any of the following ways: - Bush construction springs arranged in series and acting in torsional shear. - Circular sandwich construction springs arranged in series and acting in torsional shear.

2. An isolator as claimed in claim 1. wherein spring material is of elastomer or plastic or other flexible material.

3. An isolator as claimed in claim 1. or claim 2. wherein one open load-bearing elastomer surface is rigidly and/or permanently attached to an inner hub plate and the remaining open load-bearing elastomer surface is rigidly and/or permanently attached to a pulley.

4. An isolator according to any of proceeding claims 1. to 3. wherein springs are arranged in series as: Torsional shear bush configuration, side by side in series or nested one inside the other, or Circular sandwich construction, side by side in series or nested one inside the other.

5. An isolator according to any of proceeding claims 1. to 4. wherein the two connected springs in series comprise a preliminary spring and a primary spring such that the preliminary spring has a stiffness rate lower than that of primary spring.

6. An isolator according to any of proceeding claims 1. to 5. whereby pulley is supported in a radial direction by a radial bearing and successively supported by a structural hub that is rigidly fixed to the isolator inner hub, thus allowing the pulley freedom to rotate with resistance from torsional shear stiffness of preliminary spring in series with torsional shear stiffness of primary spring in such a way that axis of rotation for pulley is center axis position of the rigidly connected structural hub and isolator inner hub.

7. An isolator according to any of proceeding claims 1. to 6. whereby pulley is supported in an axial and/or axial-radial direction by an axial bearing interposed between pulley and axial support plate that is rigidly fixed to the isolator inner hub and structural hub, thus allowing the pulley freedom to rotate about rotation axis with axial directional control, with resistance from torsional shear stiffness of preliminary spring in series with torsional shear stiffness of primary spring in such a way that axis of rotation for pulley is center axis position of the rigidly connected structural hub, isolator inner hub.

8. An isolator according to any of proceeding claims 1. to 7. whereby isolator intermediate plate is supported in an axial and/or axial-radial direction by an axial bearing interposed between intermediate plate and structural hub, thus allowing the intermediate plate freedom to rotate with axial directional control, with resistance primarily from torsional shear stiffness of preliminary spring in such a way that axis of rotation for pulley is center axis position of the rigidly connected structural hub.

9. An isolator according to any of proceeding claims 1. to 8. wherein a displacement limiter and/or torque limiter is in place between structural hub and isolator intermediate plate. The displacement limiter and/or torque limiter shall comprise a contact surface on intermediate plate and contact surface on structural hub such that when relative torsional movement between hub and intermediate plate occurs, the two surfaces will engage after a pre-set angle of displacement, thus arresting further displacement of preliminary spring.

10. An isolator as claimed in claim 9. whereby a displacement limiter and/or torque limiter is in place between structural hub and isolator intermediate plate and will operate in forward and reverse torsional directions such as those displacements may be equal or unequal.

11. An isolator according to any of proceeding claims 9. to 10. wherein a displacement limiter and/or torque limiter is in place between structural hub and pulley. The displacement limiter and/or torque limiter shall comprise a contact surface on pulley and contact surface on structural hub such that when relative torsional movement between hub and pulley occurs, the two surfaces will engage after a pre-set angle of displacement, thus arresting further displacement of both preliminary spring and primary spring.

12. An isolator according to any of proceeding claims 9. to 11. whereby any of the displacement limiter contact surfaces may have interposed a softening buffer layer to lessen any impact loading arising from contact.

13. An isolator according to any of proceeding claims 1. to 12. whereby a third spring in series is added to the preliminary and primary springs in series.

14. An isolator according to any of proceeding claims 1. to 12. wherein a tuned torsional vibration damper or viscous torsional vibration damper is added as an integral part of assembly or attached to the assembly.

15. An isolator for reducing torsional vibration between an input source and an output structure.

16. An isolator as claimed in claim 15. wherein the input source is a combustion engine crankshaft and the output structure is an accessory drive belt.

17. An isolator as claimed in claim 15. wherein the input source is an accessory drive belt and the output structure is a combustion engine crankshaft.

18. An isolator substantially as hereinbefore described with reference to accompanying sketches/drawings.

19. A powertrain system or vehicle incorporating an isolator according to any one of the preceding claims