fig1 shows a linear compressor , which is located in a hermetically closed case 2 . the linear compressor 1 has a compression section 3 , a drive section 4 and a resonance spring arrangement 5 . the unit formed by the compression section 3 , the drive section 4 and the resonance spring arrangement 5 is suspended in the case 2 by means of two plane annular springs 6 , 7 , each being formed as a spiral with one winding . the annular springs 6 , 7 are fixed on the drive section 4 . the compression section 3 has a cylinder 8 , whose one front side is covered by a cylinder head 9 . cylinder 8 and cylinder head 9 are joined in a capsule 10 in a cartridge - like manner . a suction muffler 11 and a pressure muffler 12 are fixed on the cylinder head 9 . the suction muffler 11 is connected to a suction opening 13 and the pressure muffler 12 is connected to a pressure opening 14 in the cylinder head . the capsule 10 is inserted in an intermediary ring 15 , which is connected to the drive section 4 . during mounting , the capsule 10 and thus the cylinder 8 can be displaced within certain limits in the axial direction of the cylinder in relation to the intermediary ring 15 . when , during mounting , a predetermined position of the cylinder in relation to the drive section 4 has been reached , the capsule 10 is fixed in the intermediary ring , for example by welding , soldering or gluing . in the cylinder 8 is located a piston 16 , which borders a compression chamber 17 together with the cylinder 8 and the cylinder head 9 . before the cylinder with the capsule 10 is fixed in the intermediary piece 15 , the piston 16 is moved to its upper dead point , and the cylinder 8 is displaced , until the compression chamber 17 has reached its smallest permissible extension . the drive section 4 has a linear motor . the linear motor has an outer stator 18 with a recess 19 for a winding , not shown in detail , and an inner stator 20 . between the outer stator 18 and the inner stator 20 is an annular gap 21 , in which an armature 22 is movable . the armature carries permanent magnets 23 , which are connected to each other by means of two outer rings 24 , 25 . the outer rings 24 , 25 can , for example , be made of a plastics material . the outer rings 24 , 25 are connected to inner rings 26 , 27 via arms shown in fig2 and 3 and guided through slots in the inner stator 20 . the inner rings 26 , 27 are connected with a piston rod 28 , which again is connected to the piston 16 . the outer stator 18 and the inner stator 20 are connected to each other via motor covers 29 , 30 , which are fastened against each other by means of screw bolts 31 . the screw bolts extend in parallel to the movement direction of the piston rod 28 . the intermediary ring 15 is connected to the cylinder - side motor cover 30 , for example by soldering , gluing or welding . the resonance spring arrangement 5 , which is located at an end of the drive section 4 , which lies opposite the compression section 3 , has a spring pack 32 of several plate springs 33 . the spring pack 32 is connected in a central area 34 to the piston rod 28 . an outer section 35 of the spring pack 32 is connected via bolts 36 to a stop housing 37 , which forms a stop for the spring pack 32 . at the end projecting from the spring pack 32 , the piston rod 28 is connected to an oil pump arrangement 38 , which immerses in an oil sump , not shown in detail , which forms in the bottom part of the case 2 . when the winding located in the recess 19 is energised , the armature 22 moves in one direction and takes along the piston rod 28 in this direction . if the direction of the current is reversed , the armature 22 with the piston rod 28 moves in the opposite direction , thus also moving the piston 16 in the opposite direction . this periodically increases and reduces the volume of the compression chamber 17 . the resonance spring arrangement 5 is adapted to the frequency of the current , so that the movable part of the linear compressor 1 , which is formed by the armature 22 , the piston rod 28 , the piston 16 , the oil pump arrangement 38 and the moving part of the resonance spring arrangement 5 oscillates in resonance . fig2 and 3 now show the allocation of the piston rod 28 and the armature 22 with further details . in the area of the piston - side end , the piston rod 28 has a circumferential projection 41 , on which the inner ring 27 bears from the side lying opposite the piston 16 . on the opposite side of the projection 41 a connecting element 42 bears , with which the piston rod 28 is connected to the piston 16 . the axial fixing of the inner ring 27 in relation to the piston rod 28 also ensures axial fixing of the outer ring 25 . it forms an axial stop for the permanent magnets 23 . the second inner ring 26 is also pushed onto the piston rod 28 . thus , the second outer ring 24 comes to rest on the opposite axial front side of the permanent magnets 23 , which are then fixed between the two outer rings 24 , 25 . the second inner ring 26 is fixed by an end piece 43 screwed onto the piston rod 28 . the end piece 43 can also be connected to the piston rod 28 in other ways . the fact that in the axial direction the two inner rings 26 , 27 are pressed against each other causes that the permanent magnets 23 are fixed between the outer rings 24 , 25 in the axial direction . an outer ring 24 , 25 , an inner ring 26 , 27 and in the present embodiment three arms 40 form a connecting element 39 . of course , the number of arms 40 can also be chosen to be different . however , at least two arms are available . the connecting elements 39 can be made of a plastics material . each arm 40 has an axial projection 44 , on which the permanent magnets 23 bear from the outside . as the permanent magnets 23 form a hollow cylinder , the projections 44 are sufficient to fix the permanent magnets 23 reliably between the two connecting elements 39 in the radial direction . thus , the permanent magnets 23 are fixed in relation to the piston rod 28 in two positions , which have an axial distance to each other , so that the permanent magnets 23 cannot tilt in relation to the piston rod 28 . on the contrary , they can be guided in parallel with the piston rod 28 with a relatively high accuracy . the piston rod is merely supported via the piston in the compression section 3 and in the spring pack 32 in the resonance spring arrangement 5 . thus , it can be guided through the inner stator in a touch - free manner . accordingly , the armature 22 can also be supported in the annular gap 21 in a touch - free manner , which reduces frictional losses . the piston rod 28 can also be guided through the motor covers 29 , 30 in a touch - free manner . the compression unit with the cylinder 8 and the piston 16 is located axially outside the linear motor , that is , the driving section 4 . accordingly , the compression unit 3 must not be considered with regard to the diameter . the linear motor can therefore be built with a relatively small diameter . the piston rod is guided through the total axial length of the linear motor . at one end it is provided with the oil pump arrangement 38 , so that the oil used for lubricating the compression section 3 can also be used to dissipate a certain heat amount from the drive section 4 . the slots required for the arms 40 in the inner stator 20 are of minor importance with regard to the magnetical properties of the stator . in the inner stator 20 , the magnetic field is directed mainly axially . merely in the axial end , the magnetic field is deflected to the radial direction . however , the magnetic field has practically no component in the circumferential direction , so that the air gaps formed by the slots are not significantly disturbing . guiding the armature 22 , together with the piston rod 28 and the connected oil pump arrangement 38 , by means of the arms 40 in the inner stator 20 prevents that the armature can rotate in the circumferential direction . this secures that the oil pump arrangement is always immersed in the oil sump . while the present invention has been illustrated and described with respect to a particular embodiment thereof , it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present invention .