WO2020089566A1

WO2020089566A1 - Torsional vibration isolator for attenuating crankshaft vibration

Info

Publication number: WO2020089566A1
Application number: PCT/GB2018/000142
Authority: WO
Inventors: Terence COLFORD
Original assignee: Colford Terence
Priority date: 2018-11-02
Filing date: 2018-11-02
Publication date: 2020-05-07

Abstract

It has long been known that by inserting an isolator in between a vibrating primary structure and a connected secondary structure or system, will provide protection, comfort, extension to life and allow unfettered function and performance of that secondary structure or system. One such primary vibrating structure could be a crankshaft within a combustion engine. The crankshaft may be used to drive accessories, via a front-end-accessory-drive-belt (FEAD-belt), such as: alternator, belt alternator starter (BAS unit) and/or air-conditioning unit, and/or motor-generator unit (MGU). Optimal vibration isolation between crankshaft (primary system) and FEAD (secondary system) may be achieved by a low stiffness rate within the isolator. However, a low stiffness rate isolator is less compatible with high torque transfer through the FEAD belt such as when operating a MGU unit. Therefore, in order to maximize the operation of all FEAD devices and provide optimal vibration isolation, a two-rate stiffness isolator is desirable. Accordingly, it is proposed a two-rate torsional stiffness isolator (21) comprising at least two springs (la, lb) in series which are rigidly and/or permanently attached together via an intermediate plate (4) with springs (la, lb) constructed and arranged in any of the following ways: - bush construction springs (la, lb) arranged in series and acting in torsional shear; - circular sandwich construction springs (la, lb) arranged in series and acting in torsional shear.

Description

Title

TORSIONAL VIBRATION ISOLATOR FOR ATTENUATING CRANKSHAFT VIBRATION

Invention

The invention relates to a torsion vibration isolator pulley comprising a two-rate stiffness elastic device for attachment but not exclusively, to engine crankshaft between crankshaft front end and the front-end accessory drive (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 higher engine speeds.

To reduce the magnitude and severity of vibration within the crankshaft, the isolator device, where prime purpose is to attenuate or diminish transfer of vibration from crankshaft to FEAD pulley or visa versa, may be complemented by inclusion of a torsional vibration damper (TVD) with prime purpose to dissipate vibration energy. A TVD may be an integral part of the device or a supplementary product to 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 (Fig. 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.

An additional hub is included 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 (Fig. 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 outer 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 pertaining stiffness rates and stiffness tolerance bands. 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 Ktpi_pet_tei and Ktpi_pette2. 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. The use of a buffer control is preferred but is not mandatory. At the point of contact between intermediate plate and hub (or buffer), the preliminary spring becomes virtually inactive and further torsional motion is apportioned through primary spring alone with a continuance torsional stiffness rate equivalent to Ktpj_Pette2.

Description

Isolator Spring Unit (21) according to Fig.l comprises Inner Hub (3) for connection to rotary shaft, or crankshaft, or intermediate connecting flange or hub. Inner 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 Partial Assembly (22) according to Fig.2 comprises Isolator Spring Unit (21) constrained in a manner such that degrees of freedom are constrained. 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 front-end accessory drive belt (FEAD belt) driving accessories. Tension loads within FEAD belt can be resisted radially by action of radial load transferred through Pulley (2) via Radial Bearing (6) to Structural Hub (7). Radial Bearing (6) permits torsional movement of Pulley (2) about the main rotational axis of isolator.

Isolator Partial Assembly (22) 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 in an axial direction by Structural Hub (7).

Isolator Partial Assembly (22) according to Fig.2 has Hub (3), Structural Hub (7) and axial Support Plate (8) rigidly connected together and held together by screws or welding or rivets or adhesive or combinations of these or other. By connecting/clamping together Hub (3), Structural Hub (7) and axial Support Plate (8), a small amount of axial direction pre- compression is established within elastomeric Pipettes (la) and (lb).

Pulley (2) according to Fig.2 is free to move in a torsional direction relative to Hub (3) about the main rotational axis of isolator with resistance from pipette elastomers (la & lb) acting as two elastic members in series.

Isolator Full Assembly (23) according to Fig.3 comprises Isolator Partial Assembly (22) and a Displacement Controller (31) rigidly connected to Intermediate Plate (4) via means of screws or welding or rivets or adhesive or other. The location of Displacement Controller (31) should not be limited to inner diameter portion of Intermediate Plate (4), as seen in Fig.3. The Displacement Controller (31) may be fixed or otherwise integrally constructed at any position around the exposed surface of Intermediate Plate (4).

In accordance with Fig.4 (Fig.4a and cut-away sectional view drawing Fig.4b), distributed around the inner diameter of Displacement Controller (31) are a series of inwardly projecting ridges (31a), for example four ridges of equal dispersion. In combination and coordination, as seen in Fig.4b, an outwardly projecting set of ridges (7a) of corresponding number are disposed around a diameter of Structural Hub (7) adjacent to Displacement Controller (31) inner diameter.

The number of ridges in Structural Hub (7) and Displacement Controller (31) is not fixed to four, neither fixed is the dispersion of ridges which could have intervals of equal or irregular pitch.

In accordance with Fig.4c, at a predetermined torsional angle (f) when the Intermediate Plate (4) and rigidly attached Displacement Controller (31) are rotated in an anti-clockwise direction (33) then ridges located on Displacement Controller (31) will engage and mesh with ridges (7a) in Structural Hub (7) to inhibit further rotation thereby preventing further relative movement between Structural Hub (7) and intermediate plate (4). Likewise, a similar interaction shall occur upon clockwise rotation.

The inwardly projecting ridges of Displacement Controller (31) may have side faces bonded to a softer material or elastomer material to act as a Buffer (32), in order to dampen the harshness of contact when Displacement Controller (31) engages with Structural Hub (7), according to Fig.4c. Moreover, the outwardly projecting ridges of Structural Hub (7) may have side faces bonded to a softer material or elastomer material to act as a buffer, to dampen the harshness of contact.

The inwardly projecting ridges (31a) of Displacement Controller (31) according to Fig.4b in the null torsional load position (for example: free state position) are not necessarily equi-distanced between ridges on Structural Hub (7a). Consequently, anti-clockwise movement angle of Displacement Controller (31) and ridges (31a) to the point of contact or meshing with

Structural Hub (7) ridges (7a) may be different to clockwise movement angle of Displacement Controller (31) and ridges (31a) to the point of engagement or meshing with ridges (7a) of Structural Hub (7).

Intermeshing ridges (7a) and (31a), as shown in Fig.4, as a means of halting rotary motion of intermediate Plate (4) relative to Structural Hub (7), may be replaced by dowel pins or mushroom pins moving in a track with movement constraints or a pinion with movement limiters.

Pulley (2) within Isolator Full Assembly (23) according to Fig.3, is free to move torsionally with resistance from pipette elastomers (la & lb) acting as elastic members together in series and is guided by Radial Bearing (6) and axial bearings (5a & 5b). This provides the isolator witffa lower torsional stiffness rate (A), according to 2-rate Isolator Stiffness Graph seen in Fig.5, showing Y-axis Torque versus X -axis Displacement. According to Fig.4, at a predetermined torsional angle, <p (33) when the Intermediate Plate (4) and connected Displacement Controller (31) are rotated sufficiently then ridges (31a) located on Displacement Controller (31) will engage with ridges (7a) in Structural Hub (7) to inhibit further rotation thereby preventing further relative movement within preliminary elastomer Pipette (la) and between Structural Hub (7) and Intermediate Plate (4). The primary elastomer, Pipette (lb) and Pulley (2) are free to continue torsional movement with a higher stiffness rate (B) according to Fig.5. Thus a 2- rate torsional stiffness characteristic is created according to Graph seen in Fig.5.

The torsional Isolator Full Assembly (23) product as seen in Fig.3 and Fig.4 may be used in combination with torsional vibration dampers, either integrally or extrinsically.

Diagrams

Sketch 1 / Fig. 1 - Isolator Spring Unit (21) comprising Inner 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 - Isolator Partial Assembly (22) comprising Inner Hub (3) rigidly connected to Structural Hub (7) and axial Support Plate (8). Hub (3) is connected to elastomer pipette (la) which is connected to an Intermediate Plate (4), which in turn is connected in series to elastomer pipette (lb), which is in turn 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 Spring Unit (21). Rotational movement of pulley (2) is resisted by elastomer springs (5a and 5b) arranged in series via Intermediate Plate (4) and interposed between pulley (2) and Hub (3).

Sketch 3 / Fig. 3 - Isolator Full Assembly (23) comprising Isolator Partial Assembly (22) assembled with Displacement Controller (31).

Sketch 4 / Fig. 4 (Fig. 4a, Fig. 4b and Fig. 4c) - Cut away view of Isolator Full Assembly (23) and Displacement Controller (31), showing buffer pads (32) on inwardly projecting ridges (31a) of Displacement Controller, and showing outwardly projecting ridges (7a) of Structural Hub (7). Additionally seen is anti-clockwise rotation of Displacement Controller (31) by angle cp (33) and thus contact of projecting ridges (31a and 7a) such to inhibit further rotation between

Structural Hub (7) and intermediate plate (4).

Sketch 5 / Fig. 5 - 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 or equivalent to 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 and 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 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 pulley and hub occurs with stiffness resistance equivalent to the reciprocal of sum of the reciprocal stiffnesses of preliminary and primary springs, ultimately the two contact surfaces of intermediate plate and structural hub will engage after a pre-set angle of displacement, thus arresting further displacement of preliminary spring. Following occlusion of preliminary spring and isolator intermediate plate relative movement, the primary spring will continue to allow movement in between hub and pulley albeit at a higher rate equivalent to the stiffness rate of primary 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 extrinsically 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