Cylindrical linear motor

Abstract

To provide a cylindrical linear motor that can obtain a cushioning effect near the end of the stroke toward the contraction side.SOLUTION: A cylindrical linear motor 1 includes: a cylindrical field 6 having a plurality of annular permanent magnets 10a, 10b stacked such that north poles and south poles are arranged alternately on the inner circumference in the axial direction; an armature 2 that is inserted into the inner peripheral side of the field 6 so as to be freely movable in the axial direction; a cylindrical rod 11 having the armature 2 attached to its outer periphery and inserted into the field 6 so as to be movable in the axial direction; a guide rod 16 that can enter the rod 11; and a friction ring 50 attached to either the inner circumference of the rod 11 or the outer circumference of the guide rod 16. When the friction ring 50 is contracted to the vicinity of the contraction side stroke end, the friction ring comes into slide contact with the other of the inner circumference of the rod 11 or the outer circumference of the guide rod 16.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tubular linear motor.

Background Art

[0002] A tubular linear motor includes, for example, a tubular mover having a bottomed cylindrical outer cylinder, a plurality of permanent magnets fixed to the inner circumference of the outer cylinder such that S poles and N poles are alternately arranged in the axial direction, and a mover-side rod standing from the bottom of the outer cylinder, and a stator including a cylindrical stator-side rod and an armature attached to the outer circumference of the stator-side rod, and the stator is inserted into the mover so as to be movable in the axial direction.

[0003] In such a tubular linear motor, the mover-side rod is inserted into the stator-side rod via a bearing, and the axial movement of the mover with respect to the stator is guided by the stator-side rod and the mover-side rod (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In such a tubular linear motor, the sliding resistance between the bearing and the mover-side rod is constant, and even when it contracts to near the stroke end on the contraction side, a cushioning effect that suppresses movement toward the stroke end side cannot be obtained, and there is a problem that the impact at the time of bottoming cannot be mitigated.

[0006] Therefore, an object of the present invention is to provide a tubular linear motor that can obtain a cushioning effect near the stroke end on the contraction side.

Means for Solving the Problems

[0007] To achieve the above objective, the cylindrical linear motor of the present invention comprises a cylindrical field having a plurality of annular permanent magnets stacked so that north poles and south poles are alternately arranged in the axial direction; an armature inserted into the inner circumference of the field so as to be movable in the axial direction; a cylindrical rod having the armature mounted on its outer circumference and inserted into the field so as to be movable in the axial direction; a guide rod that can enter into the rod; and a friction ring mounted on the outer circumference of the guide rod, wherein when the motor is retracted to the vicinity of the retracted stroke end, the friction ring slides against the inner circumference of the rod.

[0008] With a cylindrical linear motor configured in this way, when the friction ring enters and slides into the rod, it generates frictional force, providing a cushioning effect that prevents the cylindrical linear motor from contracting.

[0009] Furthermore, the cylindrical linear motor may also include a barrel that is cylindrical and holds the field, a bottom cap that is cylindrical and is provided at the end of the barrel and has a hole at the bottom into which the elastic ring is fitted together with the base end, and a plate attached to the bottom cap to suspend the guide rod.

[0010] In this configuration of a cylindrical linear motor, the guide rod is fitted into the hole in the bottom cap via an elastic ring and is suspended by a plate. As a result, radial eccentricity relative to the bottom cap and inclination of the guide rod relative to the bottom cap are permitted due to the deformation of the elastic ring. This configuration of a cylindrical linear motor prevents excessive sliding resistance between the rod and the rod guide, ensuring smooth extension and retraction of the cylindrical linear motor, and also simplifies the assembly process of inserting the rod guide onto the rod. [Effects of the Invention]

[0011] According to the cylindrical linear motor of the present invention, a cushioning effect can be achieved near the end of the stroke toward the contraction side. [Brief explanation of the drawing]

[0012] [Figure 1] This is a longitudinal cross-sectional view of a cylindrical linear motor in one embodiment. [Figure 2] This is a bottom view of a cylindrical linear motor in one embodiment. [Modes for carrying out the invention]

[0013] The present invention will be described below based on the embodiments shown in the figures. In one embodiment, the cylindrical linear motor 1, as shown in Figure 1, comprises a cylindrical field 6 having a plurality of annular permanent magnets 10a, 10b stacked so that north poles and south poles are alternately arranged in the axial direction; an armature 2 inserted into the inner circumference of the field 6 so as to be movable in the axial direction; a cylindrical rod 11 to which the armature 2 is mounted on the outer circumference and which is inserted into the field 6 so as to be movable in the axial direction; a guide rod 16 that can enter into the rod 11; and a friction ring 50 mounted on the outer circumference of the guide rod 16.

[0014] The following describes in detail each part of the cylindrical linear motor 1. The armature 2 is composed of a core 3 and windings 5. The core 3 is composed of a cylindrical core body 3a and a plurality of annular teeth 3b provided on the outer circumference of the core body 3a at axial intervals.

[0015] As mentioned above, the core 3 is cylindrical and, as shown in Figure 1, has 10 teeth 3b arranged at equal intervals in the axial direction on the outer circumference of the core body 3a, with slots 4 formed between the teeth 3b, 3b, which are air gaps into which the windings 5 ​​are mounted. In this embodiment, a total of 9 slots 4 are provided between adjacent teeth 3b, 3b in Figure 1. The windings 5 ​​are wound around and mounted in these slots 4. The windings 5 ​​consist of three phases: a U-phase winding, a V-phase winding, and a W-phase winding. In the 9 slots 4, from left to right in Figure 1, the W-phase, W-phase, W-phase and V-phase, V-phase, V-phase, V-phase and U-phase, U-phase, U-phase, U-phase and W-phase are mounted.

[0016] The armature 2 is mounted on the outer circumference of the tip of a cylindrical rod 11, which is the output shaft and is made of a non-magnetic material. The rod 11 comprises a cylindrical first rod 20 and a cylindrical second rod 21, on which a core 3 is mounted on the outer circumference and which is screwed onto the inner circumference of the first rod 20.

[0017] The first rod 20 comprises a rod body 22 which is cylindrical and has threaded portions 22a and 22b on the outer circumference of the left end and the inner circumference of the right end in Figure 1, respectively, and a rod cap 23 which has a bracket 23a for attaching the cylindrical linear motor 1 to the equipment and is screwed onto the threaded portion 22a at the left end of the rod body 22 in Figure 1, thereby closing the left end of the rod body 22.

[0018] Furthermore, an annular slider 25 is fitted to the outer circumference of the right end of the rod body 22 in Figure 1. The slider 25 comprises a sliding contact portion 25a that slides against the inner circumference of the cylindrical portion 9b, which will be described later, a small-diameter portion 25b with a smaller outer diameter than the sliding contact portion 25a, located on the base end side of the rod 11, which is to the left of the sliding contact portion 25a in Figure 1, an annular groove 25c provided along the circumferential direction on the outer circumference of the small-diameter portion 25b, and a flange 25d provided on the inner circumference of the right end in Figure 1. A rubber seal ring 26, which acts as an elastic body, is fitted into the annular groove 25c of the slider 25. The inner diameter of the flange 25d is greater than or equal to the inner diameter of the rod body 22 and less than or equal to the outer diameter of the rod body 22, so that when the slider 25 is fitted to the rod body 22, the flange 25d abuts against the right end surface of the rod body 22 in Figure 1.

[0019] The second rod 21 comprises a cylindrical core-holding cylinder 21a on which the core 3 is mounted, and an annular slider 21b provided on the outer circumference of the tip of the core-holding cylinder 21a, which is the right end in Figure 1. Furthermore, a threaded portion 21c is provided on the outer circumference of the base end of the core-holding cylinder 21a, which is the left end in Figure 1, and a large-diameter inner portion 21d is provided on the inner circumference of the base end side of the core-holding cylinder 21a, which has a larger inner diameter than other parts. When the base end of the core-holding cylinder 21a is inserted into the inner circumference of the rod body 22 of the first rod 20 at the right end in Figure 1, and the threaded portion 21c is screwed into the threaded portion 22b, the first rod 20 and the second rod 21 are connected. Thus, in this embodiment, the rod 11 is composed of the first rod 20 and the second rod 21 and is cylindrical in shape.

[0020] Further, a core 3 is fitted and mounted on the outer periphery of the core holding cylinder 21a of the second rod 21. Since the outer diameter of the core holding cylinder 21a is smaller than the outer diameter of the rod body 22 of the first rod 20, when the second rod 21 with the armature 2 mounted thereon is connected to the first rod 20 with the slider 25 mounted thereon in the manner described above, the armature 2 and the slider 25 are sandwiched and fixed between the right end in FIG. 1 of the first rod 20 and the slider 21b of the second rod 21. When the armature 2 is mounted on the rod 11 in this way, the core 3 is fixed to the rod 11 in such a manner that it is sandwiched between the slider 21b and the slider 25. In the present embodiment, the armature 2 is configured to have only a single core 3, but it may be configured to have a plurality of cores 3 in order to improve the thrust or the like.

[0021] Subsequently, the rod 11 is provided with a cover 17 that covers the outer periphery of the rod 11 and forms a gap G. Specifically, the cover 17 is cylindrical and is fitted on the outer periphery of an annular cover end 18 provided on the outer periphery of the rod 11 at one end and is fitted on the outer periphery of the small-diameter portion 25b of the slider 25 at the other end and is mounted on the rod 11.

[0022] Lead wires L for connecting the windings 5 of each phase mounted on the core 3 to a drive circuit (not shown) outside are accommodated in the gap G between the cover 17 and the rod 11, and wiring work between the winding 5 and the lead wires L can be performed in a state where the cover 17 is removed, facilitating the assembly work of the tubular linear motor 1.

[0023] Subsequently, in the present embodiment, the field magnet 6 is configured to include permanent magnets 10a that are alternately laminated in the axial direction to form a plurality of annular main magnetic poles and permanent magnets 10b that are a plurality of annular auxiliary magnetic poles. Further, the field magnet 6 is accommodated in an annular gap between a cylindrical barrel 7, an inner tube 9 inserted into the barrel 7, and a back yoke 8 formed of a cylindrical magnetic body mounted on the outer periphery.

[0024] The barrel 7 is made of a non-magnetic material and has a threaded portion 7a on the inner circumference of the open end on the left side in Figure 1 and a threaded portion 7b on the outer circumference of the open end on the right side in Figure 1. A bottom cap 12 is screwed onto the outer circumference of the open end on the right side of the barrel 7 in Figure 1, closing the open end on the right side of the barrel 7 in Figure 1. The bottom cap 12 is a bottomed cylindrical shape with an annular bottom portion 12a having a hole 12a1 in the center and a cylindrical portion 12b, and is attached to the right end of the barrel 7 in Figure 1, which is the end of the barrel 7, by screwing the cylindrical portion 12b onto the outer circumference of the barrel 7. The bottom cap 12 also has a bracket formed by a pair of mounting pieces 12c, 12c that protrude axially from the bottom portion 12a and face each other. The bracket is used to attach the cylindrical linear motor 1 to equipment not shown.

[0025] Furthermore, the bottom cap 12 has its bottom portion 12a facing the other end of the field 6, which is the right end 6b in Figure 1. In addition, as shown in Figure 2, a plate 13 is attached to the bottom portion 12a of the bottom cap 12, positioned parallel to the mounting pieces 12c, 12c and crossing the hole 12a1 in the bottom portion 12a when the bottom cap 12 is viewed from the axial direction. The plate 13 has a through hole 13a in the center and is fixed to the bottom portion 12a by bolts 14, 14 that are screwed between the mounting pieces 12c, 12c and on either side of the through hole 13a. Thus, the through hole 13a in the center of the plate 13 is positioned coaxially with the hole 12a1 in the bottom portion 12a of the bottom cap 12 when viewed from the axial direction.

[0026] Next, the inner tube 9 is made of a non-magnetic material and comprises an annular head portion 9a that is attached to the open end at the left end of the barrel 7 in Figure 1 by screw fastening, and a cylindrical portion 9b that is thinner in wall thickness than the head portion 9a and extends from the inner circumference of the right end of the head portion 9a in Figure 1 and is inserted into the inner circumference of the field magnet 6. Therefore, the right end of the head portion 9a in the inner tube 9 in Figure 1 functions as a head member that faces the left end 6a in Figure 1, which is one end of the field magnet 6 attached to the outer circumference of the cylindrical portion 9b.

[0027] Furthermore, the inner tube 9 has a curved surface 9c at the boundary between the right end of the head portion 9a in Figure 1 and the cylindrical portion 9b, so that even if an axial force acts only on the head portion 9a, stress does not concentrate at the boundary between the head portion 9a and the cylindrical portion 9b. In addition, to avoid stress concentration in this way, a tapered surface may be provided at the boundary between the head portion 9a and the cylindrical portion 9b.

[0028] The field magnet 6 is composed of multiple annular permanent magnets 10a that serve as main magnetic poles and multiple annular permanent magnets 10b that serve as secondary magnetic poles, which are alternately stacked in the axial direction and inserted into the inner circumference of a cylindrical back yoke 8. The permanent magnets 10a and 10b are stacked with an adhesive in between to prevent scattering. In Figure 1, the triangular marks indicated on the main magnetic pole permanent magnets 10a and secondary magnetic pole permanent magnets 10b indicate the magnetization direction; the magnetization direction of the main magnetic pole permanent magnets 10a is radial, and the magnetization direction of the secondary magnetic pole permanent magnets 10b is axial. The main magnetic pole permanent magnets 10a and secondary magnetic pole permanent magnets 10b are arranged in a Halbach arrangement, so that on the inner circumference side of the field magnet 6, the S poles and N poles appear alternately in the axial direction.

[0029] Furthermore, in the cylindrical linear motor 1 of this embodiment, the axial length of the main magnetic pole permanent magnet 10a is longer than the axial length of the secondary magnetic pole permanent magnet 10b. By increasing the axial length of the main magnetic pole permanent magnet 10a in this way, the magnetic resistance between the main magnetic pole permanent magnet 10a and the core 3 can be reduced, and the magnetic field acting on the core 3 can be increased, thereby improving the thrust of the cylindrical linear motor 1.

[0030] Furthermore, in the cylindrical linear motor 1 of this embodiment, a back yoke 8 is provided on the outer circumference of the permanent magnets 10a and 10b. Providing the back yoke 8 ensures a magnetic path with low magnetic resistance, thereby suppressing the increase in magnetic resistance caused by the shortening of the axial length of the auxiliary pole permanent magnet 10b. Therefore, by making the axial length of the main pole permanent magnet 10a longer than the axial length of the auxiliary pole permanent magnet 10b, and providing a cylindrical back yoke 8 on the outer circumference of the permanent magnets 10a and 10b, the thrust of the cylindrical linear motor 1 can be greatly improved. The thickness of the back yoke 8 should be set to a thickness suitable for suppressing the increase in the external magnetic resistance of the main pole permanent magnet 10a.

[0031] Furthermore, the armature 2 is inserted into the inner circumference of the field 6 so as to be axially movable, and the field 6 applies a magnetic field to the core 3. Since the field 6 only needs to apply a magnetic field to the movable range of the core 3, the installation range of the permanent magnets 10a and 10b can be determined according to the movable range of the core 3. Therefore, permanent magnets 10a and 10b do not need to be installed in the annular gap between the barrel 7 and the cylindrical portion 9b in a range that does not face the core 3.

[0032] In this embodiment, the field magnet 6 is composed of permanent magnets 10a and 10b in a Halbach arrangement. However, it may also be composed of annular permanent magnets that are radially magnetized and have an N pole on their inner circumference, and annular permanent magnets that are radially magnetized and have an S pole on their inner circumference, stacked in sequence.

[0033] Between the outer circumference of the cylindrical portion 9b and the inner circumference of the barrel 7, an annular head-side spacer 40, a field magnet 6, and an annular end-side spacer 41 are housed. The head-side spacer 40 is cylindrical, and its outer diameter on the anti-field side (left side in Figure 1) is larger than the outer diameter on the field side (right side in Figure 1). The left end of the head-side spacer 40 in Figure 1 abuts against the right end surface of the head portion 9a of the inner tube 9 in Figure 1, and the right end of the head-side spacer 40 in Figure 1 abuts against the left end 6a of the field magnet 6. The right end of the head-side spacer 40 in Figure 1 fits into the gap between the cylindrical portion 9b and the back yoke 8 and abuts directly against the left end 6a of the field magnet 6.

[0034] The end spacer 41 is cylindrical, and its shape is such that the outer diameter of the anti-field side (right side in Figure 1) is larger than the outer diameter of the field side (left side in Figure 1). The right end of the end spacer 41 in Figure 1 abuts against the left end surface of the bottom 12a of the bottom cap 12, and the left end of the end spacer 41 in Figure 1 abuts against the right end 6b of the field 6. The left end of the end spacer 41 in Figure 1 fits into the gap between the cylindrical part 9b and the back yoke 8 and abuts directly against the right end 6b of the field 6.

[0035] Then, on the outer circumference of the cylindrical portion 9b, an annular head-side spacer 40, the field magnet 6, and an annular end-side spacer 41 are fitted in order from left to right in Figure 1. After screwing the head portion 9a of the inner tube 9 to the barrel 7, the bottom cap 12 is attached to the right end of the barrel 7 in Figure 1. At this point, the head-side spacer 40, the field magnet 6, and the end-side spacer 41 are sandwiched between the head portion 9a of the inner tube 9 and the bottom portion 12a of the bottom cap 12, and the field magnet 6 is fixed to the inner circumference of the barrel 7. The back yoke 8, which is attached to the outer circumference of the field magnet 6, is not sandwiched in the axial direction by the head portion 9a and the bottom cap 12, but it is bonded to the field magnet 6 and therefore does not move within the barrel 7. If the axial movement of the back yoke 8 relative to the field magnet 6 can be restrained by the magnetic force of the field magnet 6, the back yoke 8 does not need to be bonded to the field magnet 6.

[0036] Furthermore, an annular sealing member 28 is provided on the inner circumference of the head portion 9a, which slides against the outer circumference of the cover 17 that covers the outer circumference of the first rod 20, thereby preventing dust, water, and other contaminants from entering the cylindrical linear motor 1 from between the head portion 9a and the cover 17.

[0037] Then, a rod 11 to which the armature 2 is attached is inserted into the inner tube 9 so as to be movable in the axial direction, and sliders 21b and 25 slide against the inner circumference of the cylindrical portion 9b, guiding the axial movement of the armature 2.

[0038] The cylindrical portion 9b forms a gap between the outer circumference of the core 3 and the inner circumference of each permanent magnet 10a, 10b, and also plays a role in cooperating with the sliders 21b, 25 to guide the axial movement of the core 3. In this embodiment, the armature 2 is configured to have only a single core 3, but if there are multiple cores 3, sliders that slide against the inner circumference of the cylindrical portion 9b may be provided not only at both axial ends of the armature 2 but also between the cores 3, 3.

[0039] Furthermore, a guide rod 16 is inserted into the hole 12a1 in the bottom 12a of the bottom cap 12. The guide rod 16 comprises a cylindrical guide portion 16a that can be inserted into the rod 11, a cylindrical base end portion 16b provided at the right end in Figure 1 which is the base end of the guide portion 16a and has an outer diameter larger than the outer diameter of the guide portion 16a, and an elastic ring 16c attached to the outer circumference of the base end portion 16b, and is attached to the bottom 12a of the bottom cap 12 via a plate 13.

[0040] Specifically, a screw hole is formed at the right end of the guide portion 16a, and the guide rod 16 is connected to the plate 13 by a bolt 19 inserted through a through hole 13a of the plate 13, which is fixed by bolts 14, 14 at the bottom portion 12a. In this way, the guide rod 16 is inserted into the rod 11 with one end suspended by the plate 13. The outer diameter of the base portion 16b is smaller than the inner diameter of the hole 12a1 in the bottom portion 12a of the bottom cap 12. The inner diameter of the through hole 13a in the plate 13 is larger than the outer diameter of the shaft portion of the bolt 19, and an elastic ring 16c is fitted into the hole 12a1 of the bottom cap 12 on the outer circumference of the base portion 16b of the guide rod 16. In the cylindrical linear motor 1 of this embodiment, the elastic ring 16c is an O-ring, and the outer diameter of the elastic ring 16c is larger than the inner diameter of the hole 12a1.

[0041] When the base end 16b of the guide rod 16 is inserted into the hole 12a1 of the bottom cap 12, a gap is created between the outer circumference of the base end 16b and the inner circumference of the bottom 12a of the bottom cap 12, causing the elastic ring 16c to shrink in diameter and make close contact with the inner circumference of the bottom 12a. Therefore, when the guide rod 16 is inserted into the hole 12a1 of the bottom cap 12, it is elastically supported by the elastic ring 16c, allowing for radial eccentricity and inclination relative to the bottom cap 12.

[0042] The guide rod 16 is connected to the plate 13 at its right end in Figure 1 by a bolt 19 inserted through a through hole 13a in the plate 13. Thus, the left end of the guide rod 16 is not supported in Figure 1, and only the right end is cantilevered to the plate 13, and it is inserted into the rod 11 while suspended from the plate 13. Furthermore, the plate 13 is elastic and allows for twisting and bending. Therefore, since the guide rod 16 is suspended from the plate 13 and elastically supported to the bottom cap 12 by the elastic ring 16c, even though it is connected to the bottom cap 12 via the plate 13, a slight radial eccentricity relative to the bottom cap 12 and a slight inclination of the guide rod 16 relative to the bottom cap 12 are permitted.

[0043] Furthermore, the guide portion 16a of the guide rod 16 always slides against the inner circumference of the rod 11 even when the cylindrical linear motor 1 extends or retracts, guiding the axial movement of the armature 2 relative to the field 6. More specifically, the guide portion 16a of the guide rod 16 is slidably inserted toward the tip of the second rod 21 beyond the large-diameter inner portion 21d.

[0044] In this embodiment of the cylindrical linear motor 1, the guide rod 16 slides against the inner circumference of the rod 11, and the sliders 21b and 25 slide against the inner tube 9, so the armature 2 can move smoothly in the axial direction together with the rod 11 without eccentricity with respect to the field 6.

[0045] Furthermore, in the cylindrical linear motor 1 configured in this way, the inner tube 9, which guides the axial movement of the armature 2 and prevents eccentricity of the armature 2 with respect to the field 6, is integrated with the head cap. As a result, distortion is less likely to occur in the inner tube 9 and the head cap, allowing the sliders 21b and 25 to slide smoothly along the inner circumference of the inner tube 9 and extend and retract smoothly.

[0046] In the cylindrical linear motor 1, the motor reaches its most retracted state when the slider 21b contacts the bottom of the bottom cap 12 during the contraction operation in which the armature 2 moves to the right in Figure 1 relative to the field 6. In other words, in the cylindrical linear motor 1 of this embodiment, the position where the slider 21b contacts the bottom 12a of the bottom cap 12 is the stroke end on the contraction side. An annular groove 16a1 is provided on the outer circumference of the guide portion 16a of the guide rod 16, near the base end 16b, and a friction ring 50 made of an O-ring is fitted inside the annular groove 16a1. Specifically, the friction ring 50 is positioned on the outer circumference of the guide portion 16a, at a position where it is inserted into the rod 11 before the cylindrical linear motor 1 reaches its most retracted state. Therefore, the friction ring 50 is inserted into the rod 11 when the cylindrical linear motor 1 contracts to near the stroke end on the contraction side during the contraction operation in which the armature 2 moves to the right in Figure 1 relative to the field 6. The outer diameter of the friction ring 50 fitted in the annular groove 16a1 is set to be larger than the inner diameter of the right end of the second rod 21. When the friction ring 50 is inserted into the second rod 21, a frictional force is generated between the friction ring 50 and the inner circumference of the second rod 21. This frictional force acts as resistance to suppress further displacement of the rod 11 relative to the guide rod 16. Therefore, in this embodiment, when the cylindrical linear motor 1 is retracted to near the stroke end on the retraction side, the frictional force generated by the friction ring 50 provides a cushioning effect that prevents the cylindrical linear motor 1 from retracting.

[0047] In this embodiment, the cylindrical linear motor 1 houses a stroke sensor S within the rod 11. In this embodiment, the stroke sensor S is a linear variable differential transformer, and although not shown in detail, it comprises a cylindrical sensor body 30 housing a primary coil and two secondary coils, and a probe 31, which is inserted into the sensor body 30 so as to be movable in the axial direction and is the element to be detected. The linear variable differential transformer detects the position of the probe 31 from the difference in induced voltages of the two secondary coils induced when an AC voltage is applied to the primary coil.

[0048] The sensor body 30 is fixed within the first rod 20, on which the armature 2 is not mounted, and is housed in a region of the rod 11 that does not face the armature 2 in the radial direction. The probe 31 in the stroke sensor S is rod-shaped and is attached to the tip of the guide portion 16a of the guide rod 16 via the sensor holding rod 32. Thus, the probe 31, which is the element to be detected, is connected to the field 6 via the guide rod 16 and barrel 7. As described above, the probe 31 is inserted into the sensor body 30. Therefore, as the armature 2 moves axially relative to the field 6, the probe 31 moves relative to the sensor body 30 in the axial direction and moves within the sensor body 30.

[0049] A guide rod 16 that holds the probe 31 is slidably inserted into the rod 11 that houses the sensor body 30, thereby preventing radial eccentricity of the probe 31 relative to the sensor body 30. The wiring for supplying power to the primary coil of the sensor body 30 and the wiring connected to the secondary coil are routed to the outside through a hole in the rod cap 23 (not shown) and connected to a controller (not shown).

[0050] The controller (not shown in the figure) detects the position of the rod 11 relative to the field 6 using a stroke sensor S, grasps the electrical angle of the core 3 relative to the field 6, performs potential phase switching, and controls the amount of current in each winding 5 by PWM control to control the thrust and the direction of movement of the armature 2 in the cylindrical linear motor 1. Note that the control method in the controller described above is just one example and is not limited to this. Furthermore, when an external force acts that causes relative displacement of the armature 2 and the field 6 in the axial direction, the cylindrical linear motor 1 can dampen vibrations and motions of the equipment caused by the external force by generating a thrust that suppresses the relative displacement by energizing the winding 5 or by the induced electromotive force generated in the winding 5, and energy regeneration to generate power from the external force is also possible.

[0051] As described above, the cylindrical linear motor 1 of the present invention comprises a cylindrical field 6 having a plurality of annular permanent magnets 10a, 10b stacked so that N poles and S poles are alternately arranged in the axial direction, an armature 2 inserted into the inner circumference of the field 6 so as to be movable in the axial direction, a cylindrical rod 11 on which the armature 2 is mounted on the outer circumference and which is inserted into the field 6 so as to be movable in the axial direction, a guide rod 16 that can enter into the rod 11, and a friction ring 50 mounted on the outer circumference of the guide rod 16, wherein when the motor is retracted to the vicinity of the retraction-side stroke end, the friction ring 50 slides against the inner circumference of the rod 11.

[0052] With the cylindrical linear motor 1 configured in this way, when the friction ring 50 enters and slides into the rod 11, it generates a frictional force, providing a cushioning effect that prevents the cylindrical linear motor 1 from contracting. Furthermore, with the cylindrical linear motor 1 of this embodiment, a cushioning effect is obtained near the end of the stroke toward the contraction side, so the stroke speed toward the contraction side of the cylindrical linear motor 1 can be reduced by the cushioning effect, thereby mitigating the impact caused by bottoming out.

[0053] Furthermore, the stroke range in which the cushioning effect is generated can be tuned by adjusting the axial position of the friction ring 50 relative to the guide portion 16a. If a greater cushioning effect is desired, one or more friction rings 51 can be added in addition to the friction ring 50, as shown by the dashed line, at positions offset in the axial direction from the friction ring 50 relative to the guide portion 16a.

[0054] Alternatively, the friction ring 50 may be mounted on the inner circumference of the rod 11 at a position where the guide portion 16a is inserted when the cylindrical linear motor 1 has contracted to near the stroke end on the contraction side. Even if the friction ring 50 is provided on the inner circumference of the rod 11 in this way, it will slide against the outer circumference of the guide portion 16a of the guide rod 16 before the cylindrical linear motor 1 is fully contracted, generating frictional force and providing a cushioning effect.

[0055] Furthermore, in the cylindrical linear motor 1 of this embodiment, the guide rod 16 comprises a barrel 7 that is cylindrical and holds the field magnet 6, a bottom cap 12 that is bottomed cylindrical and is provided at the end of the barrel 7, and has a hole 12a1 in its bottom 12a into which the elastic ring 16c is fitted together with the base end 16b, and a plate 13 that is attached to the bottom cap 12 and suspends the guide rod 16.

[0056] With the cylindrical linear motor 1 configured in this way, the guide rod 16 fits into the hole 12a1 of the bottom cap 12 via the elastic ring 16c and is suspended by the plate 13, so the guide rod 16 is allowed to be radially eccentric with respect to the bottom cap 12 and to be tilted relative to the bottom cap 12. Therefore, even if the rod 11 and the bottom cap 12 are misaligned or slightly tilted, the guide portion 16a of the guide rod 16 can be inserted into the rod 11 without force, and the rod 11 and the guide rod 1 6 andThis prevents the sliding resistance between the rods from increasing. Thus, with the cylindrical linear motor 1 of this embodiment, it is possible to prevent the sliding resistance between the rod 11 and the guide rod 16 from increasing, thereby ensuring smooth extension and retraction of the cylindrical linear motor 1, and also making the assembly work of inserting the guide rod 16 into the rod 11 easier.

[0057] Furthermore, if the inner diameter of the through hole 13a in the plate 13 is larger than the outer diameter of the shaft portion of the bolt 19, the allowable range of eccentricity of the guide rod 16 relative to the bottom cap 12 increases, thereby improving the ease of assembly of the connection between the guide rod 16 and the plate 13.

[0058] Furthermore, if the elastic ring 16c can also function as a seal like an O-ring, the space between the base end 16b of the guide rod 16 and the inner circumference of the bottom 12a of the bottom cap 12 can be sealed with the elastic ring 16c to prevent dust, water, and other contaminants from entering the cylindrical linear motor 1. In addition, since eccentricity and inclination of the guide rod 16 relative to the bottom cap 12 are permitted, the guide rod 16 can be aligned with respect to the rod 11, thereby aligning the sensor body 30 held on the rod 11 and the probe 31 held on the guide rod 16.

[0059] In this embodiment of the cylindrical linear motor 1, the friction ring 50 is an O-ring, but as long as it can generate frictional force when sliding against the rod 11 or the guide rod 16, the friction ring 50 may be a ring made of rubber or synthetic resin other than an O-ring. Also, although the elastic ring 16c is an O-ring, it may be a ring made of rubber or synthetic resin other than an O-ring, as long as it elastically supports the guide rod 16 and allows for eccentricity or tilting relative to the bottom cap 12.

[0060] Although preferred embodiments of the present invention have been described in detail above, modifications, alterations, and changes are permitted as long as they do not deviate from the scope of the claims. [Explanation of Symbols]

[0061] 1...Cylindrical linear motor, 2...Armature, 6...Field, 7...Barrel, 10a,10b...Permanent magnets, 11...Rod, 12...Bottom cap, 12a...Bottom, 12a1...Hole, 13...Plate, 16...Guide rod, 16a...Guide section, 16b...Base end, 16c...Elastic ring, 50,51...Friction ring

Claims

1. A cylindrical field magnet having multiple annular permanent magnets stacked such that north poles and south poles are alternately arranged in the axial direction, A cylindrical armature is inserted into the inner circumference of the field so as to be movable in the axial direction, A cylindrical rod, which is cylindrical in shape and has the armature mounted on its outer circumference, and is inserted into the field so as to be movable in the axial direction, A guide rod that can enter the aforementioned rod, The rod comprises a friction ring attached to either the inner circumference of the rod or the outer circumference of the guide rod, When the rod is retracted to the vicinity of the retracted stroke end, the friction ring slides against the other of the inner circumference of the rod or the outer circumference of the guide rod. A cylindrical linear motor characterized by the following features.

2. The guide rod has a guide portion that can be inserted into the rod, a base end portion provided at the base end of the guide portion, and an elastic ring attached to the outer circumference of the base end portion. A cylindrical barrel that holds the field, A bottom cap that is cylindrical with a bottom and is provided at the end of the barrel, and has a hole in the bottom, into which the elastic ring is fitted together with the base end, It comprises a plate attached to the bottom cap for suspending the guide rod. The cylindrical linear motor according to feature 1.

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