GB2543325A

GB2543325A - Improvements in or relating to mounts for engine components

Info

Publication number: GB2543325A
Application number: GB1518229.8A
Authority: GB
Inventors: Joel De Freitas Ren
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2015-10-15
Filing date: 2015-10-15
Publication date: 2017-04-19
Also published as: GB201518229D0

Abstract

A mount 10 is provided for a vehicle engine, gearbox or transmission system. The mount 10 comprises a soft mount 15 configured to damp relative motion between at least two parts 11 12 of the system and a fabric strap(s) 13, (14) configured to restrain or limit relative motion between the two parts of the system 11 12 only when displacement or movement between the two parts exceeds a predetermined threshold. Slots 16, 17 are provided to engage the end of the fabric straps (Ribbons, Ropes, Webbing, Strips).

Description

IMPROVEMENTS IN OR RELATING TO MOUNTS FOR ENGINE COMPONENTS

This invention relates to improvements in or relating to mounts used in vehicle engines and, in particular, to mounts for vehicle engine, gearbox and transmission systems.

There are numerous parts within a vehicle that are mounted in such a way to allow a limited amount of movement between parts in use. The vehicle engine, gearbox and transmission systems include various examples of parts mounted such that some relative movement between the parts is permitted.

It is known to provide a “soft” mount between such parts. A soft mount is a flexible member that is typically formed of rubber that is inserted and subsequently vulcanised. The resulting soft mount allows a limited extent of relative movement between the parts to which it is joined. The rubber deforms elastically, returning to its original form when the force is removed.

Where the relative movement between the two parts takes the form of a small amplitude vibration, the flexible member may act as an isolator, effectively reducing the vibration of one integer relative to the other and also reducing any associated audible witness of such vibrations.

It is also known to provide a travel limiter to prevent the parts actually coming into contact with one another under high force conditions. A travel limiter would typically be provided on one of the two parts between relative movement is permitted. The travel limiter may also be formed of a rubber-based material.

It is against this background that the present invention has arisen.

According to the present invention there is provided a mount for a vehicle engine, gearbox or transmission system, the mount comprising: a soft mount configured to damp relative motion between at least two parts of the system; and a fabric strap configured to restrain relative motion between the two parts of the system only when displacement between the two parts exceeds a predetermined threshold.

The elasticity of the material of the soft mount selected is a compromise between providing a smooth ride and yet minimising unacceptable snubbing, i.e. interfacing with a travel limiter under wide open throttle conditions. Snubbing leads to unacceptable levels of sound and vibrations leading to NVH (noise, vibration and harshness) issues. Therefore, in the absence of the fabric strap, the material used for the soft mount may have to be harder, resulting in a less comfortable experience for the user under light load conditions, in order to avoid NVH issues in wide open throttle conditions. As a result, it is an advantage of the present invention that a softer material can be selected thereby providing a smoother, more comfortable experience as the NVH issues otherwise created by the use of a soft material are avoided by the provision of the fabric strap.

The mount may further comprise a travel limiter configured to limit displacement under full extension. The travel limiter, or bumper stop, is typically a stiff rubber member that halts the relative motion between the two parts of the engine, gearbox or transmission system. The travel limiter has a role in protecting the parts from damage under extreme conditions. However, under normal conditions, it should not come into play at all. In particular, the predetermined threshold may be selected to ensure that the travel limiter is not active under normal operating conditions.

The fabric strap may have a high load to displacement ratio. A high load to displacement ratio means that only a small extension in the strap is achieved per unit force. For example, the load to displacement ratio may be 2kN, 3kN or even 4kN. In particular, the load to displacement ratio may be greater than 2kN.

The fabric strap may not be under tension under low torque conditions. In this context, low torque conditions account for the majority of the driving experience, when the throttle is lightly depressed and the engine torque is low, for example, less than 75% of maximum, or even less than 50% of maximum. Under these conditions, the fabric strap is not under tension and it does not contribute in any way to the operation of the mount. Vibration and minor tensile loads are accommodated by the deformation of the soft mount and the fabric strap is not taut and carries none of the load.

It should also be noted that the fabric strap also does not contribute in any way when the mount is under a compressive force. The strap only operates under tension. Any compressive forces must be absorbed by the soft mount or, failing that, a travel limiter. However, extreme compressive forces are much less common than high tensile forces.

The fabric strap may be moulded into the soft mount and, in particular, where the soft mount is formed from rubber, the fabric strap may be moulded into the rubber of the soft mount.

Furthermore, the strap may be mechanically attached. This may be in addition to being moulded in the rubber of the soft mount or it may be instead of being moulded into the soft mount. The mechanical attachment may take the form of at least one slot provided on each of the two parts of the system into which the fabric strap can be slotted. For example, the fabric strap may be provisionally located by slotting it into place using a loop at the end of the fabric and a slot provided on the facing surface of the relevant part of the mount, engine, gearbox or transmission system. Rubber may then be inserted into and around the strap, filling the cavity between the two parts between which relative movement is to be managed. The rubber may then be vulcanised thus preparing it for use as a soft mount and also holding the fabric strap in place.

In an alternative example, the fabric strap is separate from the soft mount and is attached solely mechanically. This configuration lends itself especially to tortuous configurations where it may be challenging to provide a straight path for the fabric strap between the two parts of the mount, engine, gearbox or transmission system.

The mount may further comprise at least one additional fabric strap. There may be two, three, four or more fabric straps in total. The fabric straps may be distributed evenly around the circumference of the mount. In an alternative configuration, the fabric strap may be configured as an annular strap that extends around the circumference of the mount. As an example, the, or each where more than one is provided, fabric strap may be made of, but not limited to, nylon.

The mount may be a left hand side engine mount, a right hand side engine mount, a hydromount or a roll restrictor.

The invention will now be further and more particularly described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 is a graphical representation of a typical mount progression curve, modified to show the impact of the mount according to the present invention;

Figure 2 shows end, cross section and perspective views of a left hand side engine mount according to the present invention;

Figure 3 shows end, cross section and perspective views of a left hand side engine mount according and an alternative example of the present invention;

Figure 4 shows end, top, cross section and perspective views of a torque roll restrictor according to the present invention;

Figure 5 shows end, cross section and perspective view of a right hand side hydromount according to the present invention.

Figure 1 shows a progression curve for a mount demonstrating the effect of the present invention. The displacement in mm is plotted on the horizontal axis against the force in N on the vertical axis. The majority of low torque driving takes place with displacements between -4mm and +2mm. Within this envelope of operation, the soft mount absorbs the vibration and relative displacement between the parts of the mount. When the displacements range between -4mm and -10mm or between +2mm and +10mm, the fabric strap becomes active. The modification in the displacement caused by the fabric strap is indicated by the hatched area. The fabric strap becomes taut when the displacement reaches -4mm or +2mm and reaches its full extent when the displacement is -10mm or +10mm. If the displacement exceeds -10mm or +10mm, it is likely that the travel limiter or bumper stop will come into play to prevent damage caused by direct contact between the two parts.

It should be noted that the action at negative forces does not imply that the fabric strap is active under compression, but rather that a fabric strap is under tension in whichever direction the force is applied. For example, as shown in Figure 2, two fabric straps are applied and therefore one will be under tension when the force is applied in each of two opposing directions.

Figure 2 shows end, cross section and perspective views of a left hand side engine mount 10. The end and perspective views show the context of the engine mount, but the integers of the invention are shown only in the cross section view. Relative movement between a bracket 11 and a core 12 is controlled by two fabric straps 13, 14 and a soft mount 15. The baseplate 11 and core 12 are fabricated from aluminium, steel or cast iron and are provided with slots 16, 17 which engage with the end of the fabric straps 13, 14.

The length of the fabric strap is selected such that the fabric is not taut when the baseplate 11 and core 12 are aligned in their neutral position i.e. the position in which the two parts rest and from which the displacement is measured. Whilst the fabric is not taut, there is not an appreciable amount of slack which would have to be taken up for the fabric to become taut.

The soft mount 15 is rubber and it is introduced in between the two parts and then subsequently vulcanised thus attaching it to the baseplate 11 and the core 12 as well as to the fabric straps 13, 14. This bonding is particularly effectual if the fabric straps are formed from a mesh or webbing which enables the rubber to spread into the mesh during the vulcanisation process. This ensures that the presence of the fabric strap 13, 14 does not compromise the normal working of the soft mount 15. Furthermore, the overmoulding of the rubber onto the fabric straps 13, 14 and between the two parts 11, 12 provides a cost effective implementation.

Figure 3 shows end, cross section and perspective views of an alternative left hand side engine mount 20. As with Figure 2, the end and perspective views show the context of the engine mount, but the integers of the invention are shown only in the cross section view. Relative movement between a bracket 21 and a core 22 is controlled by two fabric straps 23, 24 and a soft mount 25. The bracket 21 and core 22 are fabricated from aluminium, steel or cast iron and are provided with slots 26, 27 which engage with the end of the fabric straps 23, 24. In this example, the slots 26, 27 are provided adjacent to the soft mount 25 so that the fabric straps 23, 24 do not pass through the soft mount 25. This is advantageous if displacement in a particular mode is likely to lead to snubbing as the straps 23, 24 can be configured in parallel with this mode rather than having their configuration dictated by the location of the soft mount 25.

Figure 4 shows end, top, cross section and perspective views of a torque roll restrictor 30 provided with an outer casing 31, a core 32, internal fabric straps 33, 34 and a soft mount 35. The configuration of the outer casing 31 and the core 32 are more easily compatible with an over-moulded configuration for the fabric straps 33, 34.

Figure 5 shows end, cross section and perspective view of a hydromount 40 including a engine side bracket 41, a core 42, internal fabric straps 43, 44 provided within a main rubber element 45 or soft mount. The engine side bracket 41 and core 42 are provided with slots 46, 47 which engage with the end of the fabric straps 43, 44.

Claims

1. A mount for a vehicle engine, gearbox or transmission system, the mount comprising: a soft mount configured to damp relative motion between at least two parts of the system; and a fabric strap configured to restrain relative motion between the two parts of the system only when displacement between the two parts exceeds a predetermined threshold.

2. The mount according to claim 1, wherein the mount further comprises a travel limiter configured to limit displacement under full extension.

3. The mount according to claim 2, wherein the predetermined threshold is selected to ensure that the travel limiter is not active.

4. The mount according to any one of claims 1 to 3, wherein the fabric strap has high load to displacement ratio.

5. The mount according to any one of claims 1 to 4, wherein the fabric strap is not under tension under low torque conditions.

6. The mount according to any one of claims 1 to 5, wherein the fabric strap is moulded into the soft mount.

7. The mount according to any one of claims 1 to 6, wherein the soft mount is formed from rubber.

8. The mount according to claim 6 or claim 7, wherein the fabric strap is moulded into the rubber of the soft mount.

9. The mount according to any one of claims 1 to 8, wherein the fabric strap is mechanically attached.

10. The mount according to claim 9, wherein the mechanical attachment comprises at least one slot provided on each of the two parts of the system into which the fabric strap can be slotted.

11. The mount according to any one of claims 1 to 10, further comprising at least one additional fabric strap.

12. The mount according to any one of claims 1 to 11, wherein the or each fabric strap is made of nylon.

13. The mount according to any one of claims 1 to 12, wherein the mount is a left hand side engine mount, a right hand side engine mount, a hydromount or a roll restrictor.