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A linear electrical machine comprising a movable piston, an axially segmented cylinder having least one magnetically permeable segment and a bore configured to allow the piston to move within the cylinder, a cylinder housing having a bore for receiving the segmented cylinder, and means for securing

A linear electrical machine comprising a movable piston, an axially segmented cylinder having least one magnetically permeable segment and a bore configured to allow the piston to move within the cylinder, a cylinder housing having a bore for receiving the segmented cylinder, and means for securing the segmented cylinder in place within the cylinder housing. This arrangement permits the construction of it free piston engine linear with improved piston position control, more consistent combustion and improved electrical conversion efficiency.

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1. A linear electrical machine comprising: a piston comprising one or more elements arranged coaxially along a piston shaft,a first axially segmented cylinder stator defining a bore therethrough along a cylinder axis and comprising at least one magnetically permeable segment, and a plurality of coil

1. A linear electrical machine comprising: a piston comprising one or more elements arranged coaxially along a piston shaft,a first axially segmented cylinder stator defining a bore therethrough along a cylinder axis and comprising at least one magnetically permeable segment, and a plurality of coils, wherein the at least one magnetically permeable segment is configured coaxially to allow the piston to reciprocate within the bore and the plurality of coils are arranged in close proximity to the piston, and wherein the coils, the at least one magnetically permeable segment and the piston elements are arranged to provide toroidal magnetic flux paths that are coaxial with the direction of travel of the piston, so that the reciprocation of the piston causes a variation of the magnetic flux within the coils;a second axially segmented cylinder stator;an intake means for permitting a flow of intake charge fluid, wherein the first axially segmented cylinder stator, the second axially segmented cylinder stator, and the intake means define the bore therethrough along the cylinder axis;a cylinder housing having a cylinder bore for receiving the first axially segmented cylinder stator; andmeans for securing the axially segmented cylinder stator within the housing secures the first axially segmented cylinder stator, the second axially segmented cylinder stator and the intake means within the cylinder housing by applying compression of the first axially segmented cylinder stator, the second axially segmented cylinder stator, and the intake means along the cylinder axis;wherein the at least one magnetically permeable segment is formed from a magnetically permeable material having isotropic electrical resistivity greater than 5.0×10−6 Ω·m in all directions; andwherein the means for securing the axially segmented cylinder stator within the housing comprises at least one clamping plate attached to the cylinder housing and an end of the axially segmented cylinder stator wherein the at least one clamping plate applies compression on the axially segmented cylinder stator along the cylinder axis. 2. The linear electrical machine of claim 1 wherein the cylinder bore is coated with or formed from material having hardness value greater than that of mild steel. 3. The linear electrical machine of claim 1 wherein the at least one cylinder segment has an elasticity modulus less than 10 GPa (10×109 N/m2). 4. A linear electrical machine of claim 1, wherein the length of the piston is at least five times its maximum diameter. 5. The linear electrical machine of claim 1, also having switching means by which the magnetic flux applied by the coils may be varied with a frequency of at least 100 Hz. 6. The linear electrical machine of claim 1 arranged within a free piston engine having a liquid spraying means that permits a coolant and/or lubricating liquid to be sprayed directly onto the piston surface. 7. The linear electrical machine of claim 1 wherein at least one of the piston elements is formed from a non-magnetising material and each element being secured such that contact is maintained between neighbouring elements. 8. A method of manufacturing a linear electrical machine according to claim 1, the method comprising: wherein the bore of the axially segmented cylinder stator is honed or otherwise finished after the axially segmented cylinder stator is secured in place;securing the axially segmented cylinder stator within the housing under compression along the cylinder axis by applying an axial tension load to the cylinder housing; andhoning or finishing the bore of the axially segmented cylindrical stator. 9. The linear electrical machine of claim 1, wherein the at least one clamping plate comprises a first clamping plate and a second clamping plate attached to each end of the cylinder housing. 10. The linear electrical machine of claim 1, wherein the at least one clamping plate comprises a first clamping plate and a second clamping plate attached to each end of the cylinder housing and the first clamping plate engages the first axially segmented cylinder stator and the second clamping plate engages the second axially segmented cylinder stator to apply the compression to the first axially segmented cylinder stator, the second axially segmented cylinder stator, and the intake means along the cylinder axis. 11. The linear electrical machine of claim 1 wherein the cylinder housing has a uniform cross section. 12. The linear electrical machine of claim 11 wherein the cylinder housing incorporates cooling fins formed in the common cross section along at least a portion of the length of the cylinder housing. 13. The linear electrical machine of claim 1, further comprising a fastener secured to the housing, wherein the compression applied on the axially segmented cylinder along the cylindrical axis is between the at least one clamping plate and the fastener. 14. The linear electrical machine of claim 13, wherein the fastener comprises at least one of a feature of the housing, an adhesive, a compression fitting, and a threaded fastener. 15. The linear electrical machine of claim 1 further comprising a piston crown provided at one or both extremities of the piston. 16. The linear electrical machine of claim 15, wherein the piston crown is ceramic. 17. The linear electrical machine of claim 15, wherein the piston crown is concave. 18. The linear electrical machine of claim 15 wherein an exposed surface area of the piston crown is at least twice the section area of the piston, and whose exposed surface material acts as a catalyst to promote oxidation of combustion chamber contents. 19. The linear electrical machine of claim 15, wherein the piston shaft is hollow. 20. The linear electrical machine of claim 15, wherein the elements coaxially arranged on the piston shaft are formed as annular rings having the same outer diameters.