GB2543087A

GB2543087A - Battery pack

Info

Publication number: GB2543087A
Application number: GB1517847.8A
Authority: GB
Inventors: Blair Dobson Simon
Original assignee: Johnson Matthey PLC
Current assignee: Johnson Matthey PLC
Priority date: 2015-10-08
Filing date: 2015-10-08
Publication date: 2017-04-12
Also published as: GB201517847D0

Abstract

A battery pack comprises a core pack 124 and a housing 101 having a sloped or curved inner surface 102. The core pack 124 comprises a pair of counteracting wedge elements 114 slidable from a first configuration (Fig. 6a) in which the core pack is insertable into the housing 101 to a second configuration (as shown) in which the wedge elements press against the core pack and the inner surface 102 of the housing, thus fixing the core pack in the housing. The wedge elements 114 may be moved relative to each other using a pair of counteracting elements 112 which have surfaces which mate with surfaces on the wedge elements (best seen in Figs. 4 and 8).

Description

Battery Pack

Field of the Invention

The present invention relates to battery packs, core packs and methods of manufacturing battery packs.

Background

Battery packs may be manufactured by manufacturing a core pack, which typically comprises the cells, cell trays or other support structure, and the electrical interconnections between the cells, and then securing the core pack within an extruded housing. The extruded housing will typically have a generally convex form. It is necessary to dimension the core-pack so that it can always be inserted into the extruded housing, however the clearances necessary to accomplish this are in direct conflict with the need to eliminate play and so prevent relative movement of the core pack and housing. It is advantageous for the cells to be firmly retained in the battery as this reduces stresses on welds and other features within the pack, and thus increases the expected mechanical life, and robustness of the battery when subject to the loading and vibration environment of the application for which the battery is designed. Free play between the core pack and the external housing would lead to noise, vibration and fatigue loading on components within the pack, and should be avoided. In the case of an extruded housing, it is also advantageous to retain the interior form in an “as extruded” condition, with no subsequent machining, as this machining adds manufacturing costs, and also may result in a degraded surface finish within the housing, which in turn may lead to difficulties in sealing the end housings to the extrusion. In many cases, the sealing of the battery housing is critical for the application concerned.

The core pack typically includes an array of cylindrical cells. Cylindrical cells are manufactured to tight tolerances, however it is known that the diameters of the cells differs between positive and negative ends of the same cell, and significant variability is observed between cells from different manufacturers. Similarly, cell lengths are typically consistent within a single part number; however it is known that the lengths of cells from different manufacturers may vary by some tenths of a millimetre. Whilst this is a relatively small range, this variability is additional to the variation that occurs in the manufacturing processes of the cell trays, and support structure of the core pack and in the manufacturing of the extruded or tubular housing itself.

Typical battery pack designs today comprise a structural housing into which the cells are fitted, either with elastomeric layers or with some form of screwed fixation which provides a means of compensating for manufactured part variability. The approach of screwed fixation is practical where the housing is conveniently split, however it may prove to be expensive, and, where there are many fixings, prone to missed operations. Elastomeric components may suffer from degradation over lifetime, particularly in an environment with significant thermal or vibration cycles, and also may be difficult to assemble with sufficient preload to ensure a rigid and functional assembly.

There is therefore a need fora practical, economic and effective means of supporting a core pack within an extruded housing of generally convex form.

Preferred embodiments of the present invention seek to overcome one or more of the above disadvantages of the prior art. In particular, preferred embodiments of the present invention seek to provide an improved battery pack.

Summary of Invention

According to a first aspect of the invention, there is provided a battery pack comprising a core pack and a housing having a sloped or curved inner surface, the core pack comprising a pair of counteracting wedge elements slidable from a first configuration in which the core pack is insertable into the housing to a second configuration in which the wedge elements press against the core pack and the inner surface of the housing, thus fixing the core pack in the housing.

Such a battery pack may be advantageous in that the manufacturing step of inserting the core pack into the housing may be straightforward and quick to perform and the core pack may then be secured firmly in the housing by a further step of sliding the counteracting wedge elements from the first configuration to the second configuration. That further step is also straightforward and quick to perform. As a result the manufacture of the battery pack can be carried out economically and efficiently, whilst still providing a battery pack that is robust and able to cope with shocks and vibrations.

Preferably the housing is an extruded housing. Preferably the housing is a substantially tubular extruded housing. A substantially tubular extruded housing will be understood as being an extruded housing in which the cross-section of the housing is substantially uniform (for example, to within normal manufacturing tolerances) along the length of the housing. The cross-section does not need to be circular, but is a closed loop and is preferably generally convex. Such tubular extruded housings may provide sufficient stiffness for the counteracting wedge elements to effectively clamp the core pack by pressing against the housing.

Preferably, the core pack comprises a pair of counteracting elements contacting the wedge elements along mating surfaces such that sliding the counteracting elements from a first arrangement to a second arrangement forces the counteracting wedge elements to move from the first configuration to the second configuration. Such an arrangement may be efficient for forcing the counteracting wedge elements into the second configuration. For example, the core pack will typically be inserted into one end of a housing having a convex profile transverse to the direction of insertion and the counteracting wedge elements will be forced apart in the transverse direction to wedge them against the housing. However, it may be more convenient and efficient to carry out a manufacturing step in which elements are pressed or pulled parallel to the direction of insertion. That can be provided by the pair of counteracting elements, which act on the counteracting wedge elements along the mating surfaces. Preferably the core pack is arranged such that forcing the counteracting elements together from the first arrangement to the second arrangement drives the wedge elements apart from the first configuration to the second configuration. Thus a force applied to the counteracting elements in a first direction may cause the counteracting elements to act on the counteracting wedge elements so as to exert a force on the counteracting wedge elements in a second direction, orthogonal to the first direction, thus causing the counteracting wedge elements to exert a force on the core pack (through the reaction of the compression of the counteracting wedge elements on the housing) in a third direction, orthogonal to the first and second directions.

The counteracting wedge elements and the counteracting elements preferably interact through mating surfaces which are perpendicular to the surface of the core pack, and angled with respect to the desired directions of movement of the counteracting wedge elements and the counteracting elements. Preferably, movement of the counteracting elements causes a perpendicular movement of the counteracting wedge elements. Preferably moving the counteracting elements towards each other separates the counteracting wedge elements. However, in some embodiments, moving the counteracting elements towards each other may move the counteracting wedge elements towards each other.

The core pack may comprise various means for forcing the counteracting elements from the first arrangement to the second arrangement. In a preferable embodiment a threaded connection between the counteracting elements is present. The threaded connection interacts with threaded holes on the counteracting elements such that rotating the threaded connection draws the counteracting elements together. Rotating the thread in the opposite direction may force the counteracting elements apart. In other embodiments a tension element is attached to one of the counteracting elements and is pulled by a suitable tool, whose forces are reacted on the other of the counteracting elements. When the tension element is pulled and the counteracting elements are forced to the second arrangement, the tension element is locked in place, for example by a locking arrangement (which may for example be of the type used in a pop riveter) or by heat staking, collets, glue or other fixing means. The means for forcing the counteracting elements from the first arrangement to the second arrangement advantageously provides a reliable, repeatable manufacturing step, which results in the core pack being firmly retained in the housing.

The counteracting wedge elements and the counteracting elements preferably slide across the surface of the core pack. The surface is preferably provided with guide rails which interact with features, such as grooves, formed in the counteracting wedge elements and the counteracting elements to ensure that they slide along the guide rails. In that way the direction of movement of the counteracting elements and wedge elements is controlled, regardless of the precise direction of the applied force during manufacture. That may result in a more reliable and robust manufacturing process.

Preferably the wedge elements are arranged to act upon the housing and the core pack in the second configuration in such a way as to apply a compressive force over a significant part of the surface area of the core pack, reacting this on the sloped or curved inner surface of the housing. In this way the load is spread across the core pack and the core pack is firmly retained with little opportunity for undesirable bending or flexing when the battery pack is handled or subject to shocks or vibrations. Preferably the counteracting wedge elements cover at least 10%, preferably at least 20%, more preferably at least 30% and yet more preferably at least 40% of the surface of the core pack.

Preferably the core pack includes a second pair of counteracting wedge elements on an opposite side of the core pack to the pair of counteracting wedge elements, the second pair of counteracting wedge elements being slidable from a first configuration in which the core pack is insertable into the housing and a second configuration in which the wedge elements press against the core pack and the inner surface of the housing, thus fixing the core pack in the housing. By providing a second pair of counteracting wedges on an opposite side of the core pack, the core pack may be centralised in the housing.

In some embodiments it may be advantageous for the core pack to be configured such that the counteracting wedge elements do not remain on the surface of the core pack, but are deflected away from the surface towards the inner surface of the housing. In this case, the mating surfaces through which the counteracting elements and the counteracting wedge elements interact would not be perpendicular to the surface of the core pack, but instead angled so as to provide a component of force in the desired direction, perpendicular to the plane. The mating surfaces would thus be inclined at an angle to the normal of the core pack surface. For example, the surfaces may be inclined at an angle of from 1-10° to the normal, preferably at an angle of from 1-5°. Such embodiments may be advantageous in that they reduce the lateral movement of the counteracting wedge elements across the core pack required in order to result in a strong force against the inner surface of the housing. Such embodiments may also permit the use of housings with shallower curves or slopes, while still resulting in a sufficient compressive force on the core pack. Advantageously, such embodiments also result in some of the reaction to the compressive force exerted by the counteracting wedge elements on the inner surface of the housing being transferred to the counteracting elements, thus resulting in both the counteracting wedge elements and the counteracting elements pressing on the core pack. That may result in the core pack being more firmly held in place. Preferably the counteracting wedge elements and the counteracting elements cover in total at least 50%, preferably at least 60%, more preferably at least 70% and yet more preferably at least 80% of the surface of the core pack. The angle may also serve as a draft angle to permit removal of the parts from a mould during manufacture of the parts.

The core pack may be arranged to be removable to facilitate service or other intervention, or may be “single operation” in which the core pack, once fixed by moving the counteracting wedge elements to the second configuration, can only be removed by removal or damage of one or more components.

According to a second aspect of the invention there is provided a core pack suitable for insertion into a housing having a sloped or curved inner surface, the core pack comprising a pair of counteracting wedge elements slidable from a first configuration in which the core pack is configured to be insertable into the housing to a second configuration in which the core pack is configured such that, in use, the wedge elements press against the core pack and the inner surface of the housing, thus fixing the core pack in the housing.

According to a third aspect of the invention there is provided a method of manufacturing a battery pack, the method comprising: providing a core pack comprising a pair of counteracting wedge elements slidable from a first configuration a second configuration; inserting the core pack into a housing having a sloped or curved inner surface with the counteracting wedge elements in the first configuration; and sliding the counteracting wedge elements into the second configuration so that the counteracting wedge elements press against the core pack and the inner surface of the housing, thus fixing the core pack in the housing.

Preferably, the method comprises sliding a pair of counteracting elements from a first arrangement to a second arrangement, the counteracting elements contacting the wedge elements along mating surfaces, thus forcing the counteracting wedge elements to move from the first configuration to the second configuration. Preferably the method comprises forcing the counteracting elements together from the first arrangement to the second arrangement to drive the counteracting wedge elements apart from the first configuration to the second configuration.

Preferably, sliding the counteracting elements causes a perpendicular sliding of the counteracting wedge elements. Preferably sliding the counteracting elements towards each other separates the counteracting wedge elements.

It will be appreciated that features described in relation to one aspect of the invention may be equally applicable in another aspect of the invention. For example, features described in relation to the battery system of the invention, may be equally applicable to the method of the invention, and vice versa. Some features may not be applicable to, and may be excluded from, particular aspects of the invention.

Description of the Drawings

Embodiments of the present invention will now be described, by way of example, and not in any limitative sense, with reference to the accompanying drawings, of which:

Figure 1 is a view of an extruded housing;

Figure 2 is a view of a core pack;

Figure 3 is a view of the core pack of Figure 2 inserted into the housing of Figure 1;

Figure 4 is a view of counteracting wedge elements and counteracting elements;

Figure 5 is a view of a the core pack of Figure 2 fitted with the counteracting wedge elements and counteracting elements of Figure 4 and inserted into the extruded housing of Figure 1;

Figure 6 is a view of a core pack fitted with the counteracting wedge elements and counteracting elements and inserted into an extruded housing;

Figure 7 is a view of part of the core pack of Figure 2; and

Figure 8 is a view of the underside of the counteracting wedge elements and the counteracting elements of Figure 4.

Detailed Description

In Figure 1 an extruded housing 1 fora battery pack has a convex curved inner surface 2. In Figure 2, a core pack 24 is formed from a bank of cells 3 sandwiched between cell holders 8. Electrical connecting elements 7 are arrayed on the top of the core pack for connecting the cells 3 in a desired configuration. Power is transferred from the connecting elements 7 to the power connectors 6 via a current shunt 4 and a controller PCB 5. On the top surface of the core pack 24 guide rails 9 and 10 run perpendicular to each other across the core pack 24 surface. In Figure 3, the core pack 24 is inserted into the housing 1. Because the top surface of the core pack 24 is flat and the inner surface 2 of the housing 1 is curved, there is a space 11 between the core pack 24 and the housing 1.

In Figure 4a counteracting wedge elements 14 in a first configuration interface with counteracting elements 12 in a first arrangement along mating surfaces 15. When the counteracting elements 12 are forced together 16, the counteracting elements 12 slide together in to a second arrangement (Figure 4b) and in doing so, the force applied to the counteracting wedge elements 14 via the mating surfaces 15 causes the counteracting wedge elements 14 to be driven apart 17 into a second configuration.

In Figure 5a, the core pack 24 is inserted into the housing 1, with the counteracting wedge elements 14 in the first configuration. In that configuration the counteracting wedge elements 14 are together in the centre of the core pack 24 and the curved inner surface 2 of the housing 1 results in an installation gap 18 between the counteracting wedges 14 and the inner surface 2. The installation gap 18 means the core pack 24, including the counteracting wedge elements 14, can be easily inserted into the housing 1.

In Figure 5b the counteracting wedge elements 14 are driven apart 17 thus causing the counteracting wedge elements 14 to press 19 against the inner surface 2 of the housing 1 and to press 20 against the surface of the core pack 24. The compression forces 19 and 20 securely fix the core pack 24 in the housing 1 and provide support across a large area of the core pack 24, thus reducing the possibility of bending or flexing of the core pack 24.

In Figure 6a a core pack 124 is inserted into a housing 101 having a curved inner surface 102. On top of the core pack 124 counteracting wedge elements 114 are in a first configuration and counteracting elements 112 (of which only one is visible) are in a first arrangement. An installation gap 118 between the counteracting wedge elements 114 in their first configuration and the inner surface 102 of the housing 101 facilitates insertion of the core pack 124 into the housing 101. The battery pack of Figure 6a differs from that of Figure 5a in that the mating surfaces 115 between the counteracting wedge elements 114 and the counteracting elements 112 is inclined at an angle to the vertical. The result is that sliding the counteracting elements 112 from the first arrangement to the second arrangement (Figure 6b) exerts a force 117 on the counteracting wedge elements 114 both outwardly and upwardly. That force 117 drives the counteracting wedge elements 114 apart so that they press 119 on the inner surface 102 of the housing 101 and press 120 on the top surface of the core pack 124. In that way the core pack 124 is retained similarly to the core pack 24 in Figure 5b. However, in Figure 6b the reaction of the force 117 on the counteracting elements 112 also causes the counteracting elements 112 to press 121 on the top surface of the core pack 124. Thus the core pack is held firmly across an even greater area of its surface, further reducing the possibility of damage from shocks and vibrations.

In Figure 7 the upper part of the core pack 24 has guide rails 9 and 10 running across the surface. The guide rails interlock with guide grooves 22 and 23 in the underside of the counteracting wedge elements 14 and the counteracting elements 12 (Figure 8). The counteracting elements 12 thus slide along the guide rails 9 and the counteracting wedge elements 14 slide along the guide rails 10. The interaction of the guide rails 9 and 10 with the grooves 22 and 23 ensures that the counteracting elements 12 and the counteracting wedge elements 14 move in the desired linear direction, regardless of the precise direction of the force applied to them.

To manufacture a battery pack, the core pack 24,124 is inserted into the housing 1,101 with the counteracting wedge elements 14,114 in the first configuration. Force is then applied to the counteracting elements 12,112 to draw them together, thus driving the counteracting wedge elements 14,114 apart and securing the core pack 24,124 in the housing 1,101. The force may be applied for example by rotating a threaded connection between the counteracting elements 12, 112, or by pulling a connector from one of the elements 12,112 through a locking element (such as a ratchet element) on the other element 12,112. The system may be such that the counteracting elements 12, 112 can be released and moved back to the first arrangement, thus permitting removal of the core pack 24, 124 from the housing 1, 101, or single use so that the core pack 24, 124 can only be removed by dismantling at least some of the components.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. For example, the counteracting elements and the counteracting wedge elements could be arranged in other ways, for example so that moving the counteracting elements apart caused the counteracting wedge elements to move apart.

Claims

1. A battery pack comprising a core pack and a housing having a sloped or curved inner surface, the core pack comprising a pair of counteracting wedge elements slidable from a first configuration in which the core pack is insertable into the housing to a second configuration in which the wedge elements press against the core pack and the inner surface of the housing, thus fixing the core pack in the housing.

2. A battery pack according to claim 1, wherein the core pack comprises a pair of counteracting elements contacting the counteracting wedge elements along mating surfaces such that sliding the counteracting elements from a first arrangement to a second arrangement forces the counteracting wedge elements to move from the first configuration to the second configuration.

3. A battery pack according to claim 2, wherein the mating surfaces are perpendicular to a surface of the core pack, and angled with respect to desired directions of movement of the counteracting wedge elements and the counteracting elements.

4. A battery pack according to claim 2, wherein the mating surfaces are inclined at an angle of from 1 -10° to the normal of the surface of the core pack.

5. A battery pack according to any of claims 2 to 4, wherein movement of the counteracting elements causes a perpendicular movement of the counteracting wedge elements.

6. A battery pack according to any preceding claim wherein the core pack is provided with guide rails which interact with features formed in the counteracting wedge elements and the counteracting elements.

7. A battery pack according to any preceding claim wherein the core pack includes a second pair of counteracting wedge elements on an opposite side of the core pack to the pair of counteracting wedge elements, the second pair of counteracting wedge elements being slidable from a first configuration in which the core pack is insertable into the housing and a second configuration in which the wedge elements press against the core pack and the inner surface of the housing, thus fixing the core pack in the housing.

8. A core pack suitable for insertion into a housing having a sloped or curved inner surface, the core pack comprising a pair of counteracting wedge elements slidable from a first configuration in which the core pack is configured to be insertable into the housing to a second configuration in which the core pack is configured such that, in use, the wedge elements press against the core pack and the inner surface of the housing, thus fixing the core pack in the housing.

9. A method of manufacturing a battery pack, the method comprising: providing a core pack comprising a pair of counteracting wedge elements slidable from a first configuration a second configuration; inserting the core pack into a housing having a sloped or curved inner surface with the counteracting wedge elements in the first configuration; and sliding the counteracting wedge elements into the second configuration so that the counteracting wedge elements press against the core pack and the inner surface of the housing, thus fixing the core pack in the housing.

10. A method according to claim 9, wherein the method comprises sliding a pair of counteracting elements from a first arrangement to a second arrangement, the counteracting elements contacting the wedge elements along mating surfaces, thus forcing the counteracting wedge elements to move from the first configuration to the second configuration.

11. A method according to claim 10, wherein sliding the counteracting elements causes a perpendicular sliding of the counteracting wedge elements.

12. A method according to claim 10 or claim 11, wherein sliding the counteracting elements towards each other separates the counteracting wedge elements.

13. A battery pack substantially as herein described with reference to the accompanying figures.

14. A core pack substantially as herein described with reference to the accompanying figures.

15. A method of manufacturing a battery pack substantially as herein described with reference to the accompanying figures.