Flat friction SHIM

Abstract

A flat shim 100 for securing a battery frame assembly (20, fig 2) in a vehicle comprising a substrate, preferably steel, and a main aperture 102 suitable for receiving a shaft of a fastener for mounti

Description

TECHNICAL FIELD The present disclosure relates to a flat friction shim. Aspects of the invention relate to a shim, to a battery frame assembly, and to a vehicle. BACKGROUND It is known to secure a battery frame to a vehicle structure using one or more bolted joints. Due to high local stiffness in both the battery frame and the vehicle structure, high shear loads are generated in the fasteners of bolted joints at the extremities of the battery frame assembly that attach the battery frame to the vehicle structure. Due to geometric limitations of a battery frame, it may not be practical to increase a number of bolted joints to share the shear load between more fasteners. Therefore, it is desirable to increase the shear force capacity of a bolted joint. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a shim, a battery frame assembly, and a vehicle as claimed in the appended claims. According to an aspect of the present invention there is provided a shim for securing a battery frame assembly in a vehicle, the shim comprising a substrate, the substrate comprising a main aperture for receiving a shaft of a fastener. The shim comprises a friction-enhancing coating. The friction-enhancing coating increases the coefficient of friction at the joint, causing less relative slip between a component of the battery frame and the vehicle part to which it is connected. Due to reduced relative slip, the shear forces in the fastener are reduced. According to an aspect of the present invention there is provided a shim for securing a battery frame assembly in a vehicle, the shim comprising a substrate, the substrate comprising a main aperture for receiving a shaft of a fastener; and one or more fixing apertures each arranged to receive one or more fixings. The shim comprises a friction-enhancing coating. The friction-enhancing coating increases the coefficient of friction at the joint, causing less relative slip between the vehicle and a component of a battery frame. Due to reduced relative slip, the shear forces in the fastener are reduced, the fastener primarily acting to press the vehicle and component together to activate the shear restraining capacity of the coated shim. The use of fixings and fixing apertures enables the friction shim to be kept in place on the battery frame during assembling or disassembling of the battery frame assembly. Accordingly, the risk that the friction shim is not installed or reinstalled on a joint during the assembly or reassembly process is reduced, because the friction shim remains affixed to the battery frame. Optionally, the friction-enhancing coating comprises a nickel matrix and embedded diamond particles. When the fixing is tightened into the battery frame, the friction shim is compressed between a surface of the fixing and a surface of the battery frame. The relative hardness of the diamond particles compared to the surfaces of the fixing and battery frame, causes the diamond particles to press into the surface of the fixing and / or battery frame. As such, a form fit is created between the friction-enhancing coating of the shim and the surface of the fixing and / or battery frame, which increases the coefficient of static friction between the shim and the surface of the fixing and / or battery frame. Optionally, the one or more fixing apertures are arranged to receive one or more bolts. The one or more bolts secure the friction shim to the battery frame during assembling or disassembling of the battery frame assembly, thus reducing the risk that the fixing is installed or reinstalled into the battery frame without using the friction shim. This reduces a risk of errors in assembly of the battery frame assembly due to leaving out the friction shim. Securing the friction shim to the battery frame via fixings also improves manufacturability of the battery frame assembly. Optionally, the one or more fixing apertures comprises a first fixing aperture and a second fixing aperture. Use of at least two fixing apertures prevents rotation of the shim relative to the battery frame, as may occur when using only a single fixing. A first fixing in a first fixing aperture secures the friction shim to the battery frame, and a second fixing in a second fixing aperture prevents rotational movement of the shim around the first fixing. Optionally, each of the first and aperture and the second fixing aperture are arranged to receive one or more bolts. Use of a bolt in each of the first and second fixing apertures enables both a first bolt and a second bolt to secure the friction shim to a battery frame, as well as to prevent rotational motion of the friction shim relative to the battery frame. Optionally, the first fixing aperture is arranged to receive one or more bolts, and the second fixing aperture is arranged to receive a locating protrusion. Using a bolt in a first aperture secures the friction shim to a battery frame, whereas a locating protrusion on the battery frame may be used to prevent rotational movement of the shim relative to the battery frame. Optionally, the shim may comprise a secondary aperture. A secondary aperture may serve to reduce the overall surface area of a friction shim. By reducing the surface area the amount of friction-enhancing coating required to fully cover the shim is reduced. This reduces the material requirement for producing each shim. Optionally, the substrate may comprise steel. A steel substrate has a strength sufficient to withstand the clamping force present in a bolted joint without yielding or compressing, in such a way that would otherwise cause loss ofclamping load. According to another aspect of the invention, there is provided a battery frame assembly for a vehicle, comprising a battery frame, said battery frame comprising a mounting aperture; a shim as described above, wherein the main aperture of the shim is arranged proximate the mounting aperture of the battery frame; one or more fixings, the one or more fixing arranged to secure the shim to the battery frame. A fastener may be arranged to pass through the main aperture of the shim and the mounting aperture of the battery frame. By using the friction shim in the battery frame assembly, the coefficient of friction at the bolted joint is increased, and therefore the shear forces experienced by bolted joints in the battery assembly are reduced. According to yet another aspect of the invention, there is provided a vehicle comprising a battery frame assembly as described above. According to yet another aspect of the invention, there is provided a method of installing a battery frame in a vehicle using a shim as described above, comprising positioning the main aperture of the shim proximate a mounting aperture of a battery frame; securing the shim to the battery frame using one or more fixings; inserting a shaft of a fastener through the main aperture of the shim and the mounting aperture of the battery frame; and tightening a portion of the fastener so that the shim is pressed between the vehicle and frame. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a friction shim assembly comprising a shim according to embodiments of the invention; Figure 2 shows a component of a battery frame assembly including a friction shim according to embodiments of the invention; Figure 3 shows a further view of the component of Figure 2; Figures 4A and 4B show different friction shims according to embodiments of the invention; Figures 5A and 5B show further friction shims according to embodiments of the invention; Figure 6 shows another friction shim according to an embodiment of the invention; Figure 7 shows an alternative friction shim according to an embodiment of the invention; Figure 8 shows a vehicle; and Figure 9 shows a flow chart showing a method of installing a shim according to embodiments of the invention. DETAILED DESCRIPTION With reference to Figure 1, there is shown a friction shim assembly 10 suitable for securing a battery assembly of a vehicle. As shown in Figure 8, the friction shim assembly may be installed in a vehicle 800. The friction shim assembly 10 as illustrated in Figure 1 comprises a friction shim 100. The friction shim 100 comprises a substrate which itself comprises a main aperture 102. The main aperture 102 is suitable for receiving at least part of a shaft of a fastener. The substrate of the friction shim 100 may further comprise a secondary aperture 106 as shown. The secondary aperture 106 may function to reduce a surface area of the friction shim 100. The friction shim assembly 10 comprises one or more fixings 110a, 110b suitable for securing the friction shim assembly to a component of a battery frame assembly. The friction shim 100 comprises a friction-enhancing coating. The friction enhancing coating may increase the coefficient of friction on a surface of the friction shim 100 compared to the coefficient of friction for an uncoated surface of the friction shim 100. The friction-enhancing coating is applied over both a vehicle facing surface of the substrate and a battery frame component facing surface of the substrate. The substrate may comprise steel. The substrate may comprise a steel foil. The substrate may comprise a carbon steel. The substrate may comprise one of C60 steel or C75 steel. The friction-enhancing coating may comprise a nickel matrix. The nickel matrix may have a thickness from 5 pm to 30 pm. In some embodiments the nickel matrix may have a thickness of 5 pm to 9 pm. In some embodiments the nickel matrix may have a thickness of 13 pm to 17 pm. In some embodiments the nickel matrix may have a thickness of 14 pm to 22 pm. In some embodiments the nickel matrix may have a thickness of 22 pm to 30 pm. The nickel matrix may comprise nickel-phosphorous. The friction-enhancing coating may comprise diamond particles embedded in the nickel matrix. The frictionenhancing coating may comprise an electroless nickel matrix in which a quantity of diamond particles is embedded. A mean particle size of the diamond particles on the surface of the shim may be 10 pm to 55 pm. The average concentration of diamond particles on the surface may be 8% to 60%. In some embodiments, the mean particle size is 10 pm and the average concentration of diamond particles may be 8% to 16%. In some embodiments, the mean particle size is 25 pm and the average concentration of diamond particles may be 8% to 25%. In some embodiments, the mean particle size is 35 pm and the average concentration of diamond particles may be 10% to 30%. In some embodiments, the mean particle size is 55 pm and the average concentration of diamond particles may be 20% to 60%. The friction shim 100 (i.e. the substrate of the friction shim 100) may have a thickness of 0.11 mm to 0.28mm. In some embodiments, the thickness of the friction shim 100 may be 0.13 mm to 0.23 mm. In some embodiments, the thickness of the friction shim 100 may be 0.13 mm. In some embodiments, the thickness of the friction shim 100 may be 0.16 mm. In some embodiments, the thickness of the friction shim 100 may be 0.19 mm. In some embodiments, the thickness of the friction shim 100 may be 0.23 mm. In embodiments, the shim 100 may be formed as a single part. In embodiments, the substrate of the friction shim 100 may be formed using a laser cutting process. In embodiments, the substrate of the friction shim 100 may be formed using a stamping process. In some embodiments, the friction-enhancing coating may be applied to the substrate via a dipping process. In embodiments, the friction-enhancing coating may be applied to the substrate via a spraying process. Figure 2 shows a component of a battery frame assembly 20 including a friction shim 200. The battery frame assembly 20 may comprise a battery frame casting 220. The friction shim 200 may be secured to the battery frame casting 220 by one or more fixings 210. In some embodiments, the one or more fixings 210 may be removably securable to a portion of the battery frame casting 220. In embodiments, the battery frame casting 220 may comprise aluminium. In embodiments, the battery frame casting 220 may be painted. Figure 3 shows a further view of the component of the battery frame assembly 20 of Figure 2, including a friction shim 200, one or more fixings 210, and a battery frame casting 220. Figures 4A to 7 showa numberof different shapes of friction shims, according to embodiments of the invention. Figure 4A shows a friction shim 400a having two fixing apertures 404a, 404b. The friction shim 400a comprises a main aperture 402. The main aperture 402 is suitable for receiving at least part of a shaft of a fastener. The friction shim 400a comprises a first fixing aperture 404a and a second fixing aperture 404b. Each of the first fixing aperture 404a and the second fixing aperture 404b are suitable for receiving a fixing, said fixings suitable for securing the friction shim 400a to a component of a battery frame assembly, such as battery frame casting 220 of Figure 2. Use of a first fixing aperture 404a and a second fixing aperture 404b enables prevention, or at least reduction, of rotation of the friction shim 400a relative to a battery frame. In some embodiments, in use, each of first fixing aperture 404a and second fixing aperture 404b may receive a fixing, such as a bolt, screw, or similar, in order to secure the friction shim 400a to the component of the battery frame assembly. In some embodiments, one of the first fixing aperture 404a or the second fixing aperture 404b may receive a fixing, such as a bolt, screw, or similar, and the other of the first fixing aperture 404a or the second fixing aperture 404b may receive a locating protrusion. The locating protrusion may be a protrusion of a component of the battery frame assembly. The locating protrusion in one of the first fixing aperture 404a or the second fixing aperture 404b may serve to prevent (or at least act to reduce) rotation of the friction shim 400a relative to the component of the battery frame assembly, said rotation being around the other fixing and retain the shim in position so that the main aperture 402 is aligned with a corresponding aperture in the battery frame casting 220. Figure 4E3 shows an alternative friction shim 400b having two fixing apertures 404a, 404b. The friction shim 400b of Figure 4B is substantially the same as the friction shim 400a of Figure 4A. The friction shim 400b additionally comprises a secondary aperture 406. The secondary aperture 406 may function to reduce a surface area of the friction shim 400b. Reducing the surface area of the friction shim 400b reduces the quantity of material forthe friction-enhancing coating. Accordingly, the quantity of nickel matrix and / or diamond particles for the friction-enhancing coating is reduced, compared to a friction shim not having a secondary aperture 406. Figure 5A shows a friction shim 500a having a single fixing aperture 504. The friction shim 500a comprises a main aperture 502. The main aperture 502 is suitable for receiving at least part of a shaft of a fastener. The friction shim 500a comprises a fixing aperture 504. The fixing aperture 504 is suitable for receiving a fixing, said fixing suitable for securing the friction shim 500a to a component of a battery frame assembly, such as battery frame casting 220 of Figure 2. Figure 5B shows an alternative friction shim 500b having a single fixing aperture 504. The friction shim 500b of Figure 5B is substantially the same as the friction shim 500a of Figure 5A. The friction shim 500b additionally comprises a secondary aperture 506. The secondary aperture 506 may function to reduce a surface area of the friction shim 500b. Figure 6 shows a friction shim 600 having a single slotted fixing aperture 604. The friction shim 600 comprises a main aperture 602. The main aperture 602 is suitable for receiving at least part of a shaft of a fastener. The friction shim 600 comprises a fixing aperture 604. The fixing aperture 604 has a slotted profile, such that the fixing aperture 604 is suitable for receiving a plurality of fixings in the single slotted fixing aperture 604. Figure 7 shows an alternative friction shim 700 having two fixing apertures 704a, 704b located on separate wing portions of the shim. The friction shim 700 comprises a main aperture 702, in this example between the separate wing portions. The main aperture 702 is suitable for receiving at least part of a shaft of a fastener. The friction shim 700 comprises a first fixing aperture 704a and a second fixing aperture 704b. Each of the first fixing aperture 704a and the second fixing aperture 704b are suitable for receiving a fixing, said fixings suitable for securing the friction shim 700 to a component of a battery frame assembly, such as battery frame casting 220 of Figure 2. Figure 8 shows a vehicle 800 in accordance with an embodiment of the invention. A battery frame assembly comprising one or more friction shims as described herein may be directly installed to the vehicle 800, or preattached to a sub-assembly which is then fitted to the vehicle 800. Figure 9 shows a flow chart showing a method 900 of installing a battery frame in a vehicle. At step 910, a shim is positioned such that a main aperture of the shim is arranged proximate a mounting aperture of a battery frame. At step 920, the shim is secured to the battery frame using one or more fixings, said fixings inserted through one or more fixing apertures of the shim. At step 930, the battery frame is positioned on the vehicle and a shaft of a fastener is inserted through both the main aperture of the shim and the mounting aperture of the battery frame. At step 940, the fastener is tightened, such that a surface of the shim is compressed between a surface of the vehicle and a surface of the battery frame. The fastener may be a screw-threaded bolt that is screwed into a correspondingly threaded bore in either the vehicle or the battery frame. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. A shim for securing a battery frame assembly in a vehicle, the shim comprising:a substrate, the substrate comprising:a main aperture suitable for receiving a shaft of a fastener; and one or more fixing apertures, each arranged to receive one or more fixings; and a friction-enhancing coating.

2. The shim of claim 1, wherein the friction-enhancing coating comprises a nickel matrix and embedded diamond particles.

3. The shim of claim 1 or 2, wherein the one or more fixing apertures are arranged to receive one or more bolts.

4. The shim of claim 3, wherein each of a first fixing aperture and a second fixing aperture are arrangedto receive one or more bolts.

5. The shim of claim 4, wherein the first fixing aperture is arranged to receive one or more bolts, and the second fixing aperture is arranged to receive a locating protrusion.

6. The shim of any of claims 1 to 3, wherein the coating is applied to both a vehicle facing surface and a component facing surface of the shim.

7. The shim of any of claims 1 to 6, comprising a secondary aperture.

8. The shim of any of claims 1 to 7, wherein the substrate comprises steel.

9. A battery frame assembly for a vehicle, comprising:a battery frame, said battery frame comprising a mounting aperture;the shim of any of claims 1 to 8, wherein the main aperture of the shim is arranged proximate the mounting aperture of the battery frame; andone or more fixings, the one or more fixings arranged to secure the shim to the battery frame.

10. A vehicle comprising the battery frame assembly of claim 9 and a fastener that pass through the main aperture and clamps the battery frame assembly to the vehicle with the shim between the vehicle and frame.

11. A method of installing a battery frame in a vehicle employing the shim of any of claims 1 to 8, the method comprising:positioning the main aperture of the shim proximate a mounting aperture of a battery frame; securing the shim to the battery frame using one or more fixings;assembling the frame on a vehicle;inserting a shaft of a fastener through the main aperture of the shim and the mounting aperture of the battery frame; andtightening the fastener to press the shim between a surface of the vehicle and a surface of the5 frame.

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