CN113632344A

CN113632344A - Electric linear actuator

Info

Publication number: CN113632344A
Application number: CN202080024225.4A
Authority: CN
Inventors: 李友行
Original assignee: Hitachi Astemo Ltd
Current assignee: Hitachi Astemo Ltd
Priority date: 2019-07-11
Filing date: 2020-06-26
Publication date: 2021-11-09
Also published as: JPWO2021006067A1; GB2599013A; JP7217350B2; WO2021006067A1; GB2599013B

Abstract

The actuator has a cylindrical outer tube having a bottom and a cylindrical intermediate tube having both closed ends. An armature having a coil is provided at one end of the intermediate pipe. A plurality of permanent magnets are provided on the inner peripheral surface of the outer tube so as to face the coil. The intermediate pipe is provided with a communication hole which is positioned at one end side of the partition member when the outer pipe and the intermediate pipe are at the maximum relative length position, and which communicates the inside of the outer pipe with the inside of the intermediate pipe.

Description

Electric linear actuator

Technical Field

The present invention relates to an electric linear actuator for damping vibration of a vehicle such as an automobile or a railway vehicle.

Background

In general, in a vehicle such as an automobile or a railway vehicle, a shock absorber is provided between a vehicle body side (sprung portion) and an axle (underframe or wheel) side (unsprung portion). As such a damper, an electric linear actuator (linear motor) including an armature (coil) and a permanent magnet that are supported so as to be linearly movable relative to each other is known. Here, patent document 1 describes a linear actuator capable of moving air by providing a passage (communication groove) separately between air chambers having a variable volume in order to reduce air resistance during expansion and contraction. On the other hand, patent document 2 describes an electromagnetic suspension device in which the coil of an electromagnetic damper can be cooled by circulating air in one direction inside an air spring.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2014-003824

Patent document 2: japanese laid-open patent publication No. 2002-257189

Disclosure of Invention

Problems to be solved by the invention

The electric linear actuator is preferably capable of reducing air-generated damping, that is, an air spring force accompanying a change in volume of an internal air chamber, during operation (expansion and contraction, and stroke). In addition, in order to suppress a temperature rise of the armature (coil), it is preferable to be able to cool the armature (coil).

The invention aims to provide an electric linear actuator which can reduce the air spring force and improve the cooling performance of an armature.

Means for solving the problems

One embodiment of the present invention is an electric linear actuator which is mounted between two members which move relative to each other and generates a control force, the electric linear actuator including: a first cylinder having a bottomed cylindrical shape having a bottom at one end portion attached to one of the two members, the first cylinder extending in an axial direction; a second cylinder extending in an axial direction of the first cylinder, located radially inside the first cylinder, having another end attached to the other of the two members, and having both ends closed; a partition member provided at the other end of the first cylinder, sliding on an outer peripheral surface of the second cylinder, and partitioning the outer periphery of the second cylinder from the outside; a plurality of permanent magnets formed in a ring shape on an inner peripheral surface of the first cylinder, the permanent magnets extending in an axial direction of the first cylinder; an armature provided at one end of the second cylinder; the second cylinder is formed with a first communication hole which is located closer to one end side than the partition member when the first cylinder and the second cylinder are at the maximum relative length positions, and communicates the inside of the first cylinder with the inside of the second cylinder.

Effects of the invention

According to one embodiment of the present invention, the air spring force can be reduced and the cooling performance of the armature can be improved.

Drawings

Fig. 1 is a side view schematically showing a railway vehicle on which an electric linear actuator according to the embodiment is mounted.

Fig. 2 is a plan view schematically showing the positional relationship of the vehicle body, the inverter, the electric linear actuator, the acceleration sensor, and the like in fig. 1.

Fig. 3 is a longitudinal sectional view showing the electric linear actuator according to the first embodiment in a reduced state.

Fig. 4 is a longitudinal sectional view showing the electric linear actuator of fig. 3 in an extended state.

Fig. 5 is a longitudinal sectional view showing an electric linear actuator according to a second embodiment in a reduced state.

Fig. 6 is a longitudinal sectional view showing the electric linear actuator of fig. 5 in an extended state.

Fig. 7 is a longitudinal sectional view showing an electric linear actuator according to a third embodiment in a reduced state.

Fig. 8 is a longitudinal sectional view showing the electric linear actuator of fig. 7 in an extended state.

Fig. 9 is a longitudinal sectional view showing an electric linear actuator according to a fourth embodiment in a reduced state.

Fig. 10 is a longitudinal sectional view showing the electric linear actuator of fig. 9 in an extended state.

Fig. 11 is a longitudinal sectional view showing an electric linear actuator according to a fifth embodiment in a contracted state.

Fig. 12 is a longitudinal sectional view showing the electric linear actuator of fig. 11 in an extended state.

Fig. 13 is a longitudinal sectional view showing an electric linear actuator according to a sixth embodiment in an extended state.

Fig. 14 is a longitudinal sectional view showing an electric linear actuator according to a seventh embodiment in an extended state.

Detailed Description

Hereinafter, an example of a case where the electric linear actuator according to the embodiment is mounted on a railway vehicle will be described with reference to the drawings.

Fig. 1 to 4 show a first embodiment. In fig. 1, a railway vehicle 1 (hereinafter, referred to as a vehicle 1) includes: a vehicle body 2 on which a passenger such as a passenger or a crew member sits, a front underframe 3A and a rear underframe 3B provided under the vehicle body 2. In fig. 1 and 2, in order to avoid the complexity of the drawing, a train of one car 1, that is, one consist is shown. However, the vehicle is generally operated on a train in which a plurality of vehicles 1 are connected, that is, a train composed of a plurality of vehicles 1.

Two wheel shafts 6, each having

wheels

4, 4 provided on both ends of the

axles

5, 5 in the longitudinal direction (i.e., both ends of the vehicle body 2 in the width direction), are mounted on the

chassis

3A, 3B so as to be separated in the front-rear direction. Thus, four

wheels

4, 4 are provided on the

respective undercarriages

3A, 3B. The vehicle 1 travels along the left and right rails R (only one is shown in fig. 1) by the

wheels

4, 4 rotating on the rails R.

Between the vehicle body 2 and the

respective underframes

3A, 3B of the vehicle 1, a plurality of air springs 7A-7D for elastically supporting the vehicle body 2 on the

respective underframes

3A, 3B and a plurality of actuators 11A-11D arranged in parallel relation to the respective air springs 7A-7D are provided. The air springs 7A to 7D are also referred to as "bolster springs" or "suspension springs", and correspond to "secondary springs" provided between the vehicle body 2 or the like serving as "sprung mass" and the

underframes

3A, 3B or the like serving as "unsprung mass". The "primary spring" corresponds to a shaft spring provided on the

underframe

3A, 3B, that is, a shaft spring provided between the wheels 4, 4 (wheel shafts 6, 6) serving as "unsprung mass" and the underframe frame of the

underframe

3A, 3B serving as "unsprung mass". One air spring 7A-7D is provided on each of the left and right sides of each of the

underframes

3A, 3B.

The actuators 11A to 11D are inter-vehicle body chassis actuators provided between the vehicle body 2 and the

chassis

3A, 3B of the vehicle 1, and generate control forces adjustable in the up-down direction. In this case, the actuators 11A to 11D are constituted by linear actuators (electric linear actuators), and electric linear motors (electromagnetic actuators) such as three-phase linear motors, for example. The actuators 11A to 11D and the air springs 7A to 7D constitute an electric suspension (electromagnetic suspension) that damps (damps) vibrations in the vertical direction between the vehicle body 2 and the under

frames

3A and 3B. The actuators 11A to 11D are provided two by two in the left-right direction for each of the

chassis

3A, 3B.

The actuators 11A to 11D are mounted in the up-down direction with respect to the vehicle 1. The actuators 11A to 11D generate forces so that vibrations of the vehicle body 2 with respect to the front underframe 3A and the rear underframe 3B are individually damped and reduced in the left-right direction of each

underframe

3A, 3B, respectively, in accordance with command signals individually output from the control device 14. In this case, the actuators 11A to 11D generate force by electric power supplied via the inverters 12A to 12D. The inverters 12A to 12D are power supply circuits for the actuators 11A to 11D.

The power line side of the inverters 12A to 12D is connected to a vehicle power source (not shown) (for example, a power supply source from an overhead wire, a generator, or the like), and the power line side is connected to the actuators 11A to 11D. The inverters 12A to 12D are configured to include a plurality of switching elements each configured by, for example, a transistor, a Field Effect Transistor (FET), an Insulated Gate Bipolar Transistor (IGBT), or the like, and each switching element is controlled based on a command signal from the control device 14.

The inverters 12A to 12D drive the actuators 11A to 11D based on a command signal from the control device 14 and electric power from a vehicle electric power source. That is, during powering operation of the actuators 11A-11D, electrical power is supplied to the actuators 11A-11D from the vehicle electrical power source via the inverters 12A-12D. At this time, the inverters 12A to 12D generate three-phase (u-phase, v-phase, w-phase) ac power from the power supplied from the vehicle power source via the power lines, and supply the power to the

coils

31A, 31B, and 31C of the actuators 11A to 11D via the power lines (see fig. 3 and 4).

As shown in fig. 2, acceleration sensors 13A to 13D that detect the vertical acceleration of the vehicle body 2 as sprung acceleration at respective positions are provided on the vehicle body 2 at positions on the four-corner sides that are separated in the front-rear direction and the left-right direction. The acceleration sensors 13A to 13D are sensors (behavior sensors) that are mounted at a plurality of different positions of the vehicle 1 and detect the behavior of the vehicle 1 (more specifically, the vibration state of the vehicle body 2). The acceleration sensors 13A to 13D are connected to a control device 14. The acceleration sensors 13A to 13D output detection signals of the acceleration of the vehicle body 2 detected at the respective positions to the control device 14 as mutually different signals (detection signals of the vibration of the vehicle body 2 as the vehicle behavior).

The control device 14 variably controls the force generated by each of the actuators 11A to 11D. The control device 14 is constituted by a microcomputer or the like, for example. An input side of the control device 14 is connected to the inverters 12A to 12D, the acceleration sensors 13A to 13D, and the like. The output side of the control device 14 is connected to the actuators 11A to 11D via the inverters 12A to 12D.

Vehicle information of the vehicle 1 (for example, a traveling position, a traveling speed, and the like of the vehicle) is input to the control device 14 via the communication line 15. The control device 14 performs an operation (control operation) therein based on, for example, signals (acceleration) obtained from the acceleration sensors 13A to 13D and signals (vehicle information) obtained via the communication line 15, and outputs command signals to the actuators 11A to 11D (specifically, the inverters 12A to 12D).

In this case, the control device 14 reads detection signals from the acceleration sensors 13A to 13D at each sampling time and calculates command signals (current values of control commands) in accordance with, for example, a skyhook damping theory (skyhook damping control rule) in order to reduce vibrations such as roll (yaw) and pitch (forward and backward swinging) of the vehicle body 2 and improve the riding comfort. On this basis, the control device 14 individually outputs command signals to the inverters 12A to 12D, variably controlling the generation force of each actuator 11A to 11D. The control rule of the actuators 11A to 11D is not limited to the skyhook damping control rule, and may be a configuration using, for example, an LQG control rule, an H ∞ control rule, or the like.

Next, the actuators 11A to 11D (hereinafter, also simply referred to as the actuators 11) will be described with reference to fig. 3 and 4.

The actuator 11 includes, for example, a stator 21 disposed on the vehicle body 2 side and a mover 34 disposed on the

chassis

3A, 3B (wheel 4) side. The actuator 11 is a three-phase linear motor (three-phase linear synchronous motor) including a permanent magnet 43 provided on a mover 34 serving as a first member and a coil member 31 of an armature 29 provided on a stator 21 serving as a second member. More specifically, the actuator 11 is configured as a cylindrical linear electromagnetic actuator including a coaxial inner cylinder (displacement member) and outer cylinder (displacement member) that are relatively displaceable, and is interposed between the vehicle body 2 (sprung member) and the under frames 3A and 3B (unsprung members) on the wheel 4 side. In this case, the actuator 11 includes: a coil member 31 (

coils

31A, 31B, 31C) composed of a multi-phase coil group provided on an intermediate tube (middle tube)23 of the support member 22 corresponding to the inner tube via a core 30; the permanent magnet 43 as a magnetic member is provided on the outer tube (outer tube)35 corresponding to the outer tube, and faces the coil member 31.

The stator 21 and the mover 34 of the actuator 11 are respectively installed between two members that move relatively (for example, between the base frames 3A, 3B that become one member and the vehicle body 2 that becomes the other member). The stator 21 and the mover 34 are arranged so as to be linearly displaceable relative to each other (relatively movable) between the vehicle body 2 and the

chassis

3A, 3B, and generate thrust in the axial direction which is the stroke direction, that is, in the vertical direction in fig. 3 and 4 which is the direction of the relative displacement. In the present embodiment, a case in which the first member of the first member and the second member is the mover 34 and the second member is the stator 21 is exemplified. However, the present invention is not limited to this, and the first member may be a stator and the second member may be a mover. In the following description, one axial end side of the actuator 11 is referred to as a lower end side (lower end side in fig. 3 and 4) and the other axial end side is referred to as an upper end side (upper end side in fig. 3 and 4).

The stator 21 has an armature 29 on its lower end side. That is, the stator 21 includes the support member 22, the armature 29, the stroke sensor 32, and the housing 33. The support member 22 includes, for example, a cylindrical intermediate pipe 23 extending in the axial direction and an inner pipe (inner tube)28 disposed radially inside the intermediate pipe 23. The intermediate pipe 23 as a second cylinder extends in the axial direction of the outer pipe 35, and is located radially inside the outer pipe 35. An armature 29 is provided at one end (lower end in fig. 3 and 4) of the intermediate pipe 23. The other end portion (the upper end portion in fig. 3 and 4) of the intermediate pipe 23 is attached to the vehicle body 2 (the other of the two members). The intermediate tube 23 is closed at both ends. That is, the lower end portion that becomes one end portion of the intermediate pipe 23 is closed by the lower end side closing portion 24 that becomes one end side closing portion. An upper end portion which becomes the other end portion of the intermediate pipe 23 is closed by an upper plate 26 which becomes the other end side closing portion.

More specifically, the intermediate pipe 23 includes: a cylindrical tube portion 25 extending in the vertical direction (axial direction), a lower end side closing portion 24 closing the lower end side of the tube portion 25, and an upper plate 26 closing the upper end side of the tube portion 25. An armature 29 is integrally (fixedly) provided to the lower end side closing portion 24. The lower end side closing portion 24 is provided with a stroke sensor 32 that detects the relative position of the armature 29 (i.e., the stroke amount of the actuator 11). The upper plate 26 is formed in a disc shape having a larger diameter dimension than the outer tube 35. A cylindrical housing 33 extending downward over the entire circumference is attached to the outer peripheral edge of the upper plate 26. In the upper plate 26, a mounting hole 27 is provided, and the mounting hole 27 is mounted to, for example, a spring of the vehicle 1 (for example, the vehicle body 2). The mounting hole 27 is a mounting member for mounting the upper plate 26 to a sprung member (vehicle body 2 side) of the vehicle 1. The outer casing 33 covers the upper side of the outer tube 35, i.e., the upper half and the middle tube 23. The upper plate 26 and the outer shell 33 protect the intermediate pipe 23 and the outer pipe 35 from flying stones and the like while the vehicle 1 is traveling.

The inner pipe 28 as a third cylinder is disposed inside the intermediate pipe 23. More specifically, the inner tube 28 is disposed inside the intermediate tube 23 with a space. The lower end side of the inner tube 28 extends in the axial direction on the inner peripheral side of the armature 29 (core 30), and is fixed to the inside of the core 30 by, for example, fitting, press-fitting, or the like. That is, the lower end 28A, which is one end of the inner tube 28, extends to the armature 29 and is positioned on the inner circumferential side of the armature 29. An upper end portion 28B, which is the other end portion of the inner pipe 28, is fixed to an upper end portion of the intermediate pipe 23, that is, the upper plate 26. In other words, the upper end portion 28B of the inner tube 28 extends axially to the position of the upper plate 26 and is closed by the upper plate 26. In the inner tube 28, a rod 38 is inserted.

The armature 29 is formed in a ring shape. The inner peripheral portion (inner peripheral side space) of the armature 29 is connected to the inside (inner side space) of the intermediate pipe 23. The armature 29 is composed of a substantially cylindrical core 30 made of a magnetic material, for example, and a plurality of

coils

31A, 31B, and 31C (i.e., a u-phase coil 31A, v-phase coil 31B, w-phase coil 31C) provided on the core 30 and constituting a coil member 31. The number of coil components 31 (

coils

31A, 31B, and 31C) is not limited to three, and may be changed as appropriate according to design specifications, for example, such as six, nine, and twelve.

The stroke sensor 32 is provided on the lower end side closing portion 24 of the intermediate pipe 23. The stroke sensor 32 detects a stroke position of the actuator 11. That is, the stroke sensor 32 measures an absolute position or a relative position between the armature 29 and the mover 34. The stroke sensor 32 can be constituted by a magnetic sensor such as a magnetoresistive element or a hall element (hall IC) for detecting a magnetic field (magnetic field or magnetic flux) or a polarity (magnetic pole) by using a change in magnetic resistance or a hall effect. The stroke sensor 32 detects a magnetic field, a polarity, and the like of the permanent magnet 43 that is displaced in the axial direction relative to the stroke sensor 32. This enables the axial position (stroke position) of the permanent magnet 43 to be calculated, and the current necessary for the

coils

31A, 31B, and 31C to be supplied based on the position. The stroke sensor 32 is not limited to a magnetic sensor, and various stroke sensors (displacement sensors) such as a laser displacement meter capable of measuring the relative position or the absolute position between the armature 29 and the mover 34 may be used.

The lower end of the mover 34 is connected to the

chassis

3A, 3B. The mover 34 is provided with excitation magnets each formed of a plurality of permanent magnets 43 extending in the axial direction of the mover 34 and formed in a ring shape. The mover 34 has an outer tube 35 which is a cylindrical member. That is, the mover 34 includes: an outer tube 35 as a yoke (outer tube) disposed on the outer peripheral side of the armature 29 (the core 30 and the

coils

31A, 31B, 31C), a rod 38 located inside the outer tube 35 and extending in the axial direction, and a plurality of permanent magnets 43 as magnetic members provided on the outer tube 35 and facing the

coils

31A, 31B, 31C with gaps in the radial direction. In the drawings, the plurality of permanent magnets 43 are illustrated as one magnet, but, for example, a plurality of annular permanent magnets 43 are provided in an axially aligned manner.

The outer tube 35 as the first cylinder is formed using, for example, a magnetic material that forms a magnetic circuit when placed in a magnetic field. The outer tube 35 forms a magnetic circuit of the actuator 11 by using a magnetic material, and also has a function as a cover for preventing the magnetic flux of the permanent magnet 43 from leaking to the outside. The outer tube 35 is formed in a bottomed cylindrical shape and extends in the axial direction. That is, the outer tube 35 has a bottom 37 at a lower end portion which is one end portion. The lower end of the outer tube 35 is mounted on the

chassis

3A, 3B (one of the two members). The outer tube 35 includes: a cylindrical tube portion 36 extending in the vertical direction (axial direction), a bottom portion 37 closing the lower end side of the tube portion 36, and an annular partition member 42 provided on the upper end side of the tube portion 36 and extending radially inward toward the intermediate pipe 23.

A plurality of permanent magnets 43 are arranged in an axial direction on the radially inner side of the cylindrical portion 36. At the bottom 37, a rod 38 is provided, the rod 38 being located inside the cylindrical portion 36 and extending from the bottom 37 in the axial direction inside the armature 29. The bottom portion 37 is provided with a mounting hole 41, and the mounting hole 41 is located on the opposite side of the rod 38 in the axial direction. The mounting hole 41 is a mounting member for mounting the outer tube 35 to the unsprung member (the

chassis

3A, 3B side) of the vehicle 1.

The rod 38 is inserted into the inner tube 28. The rod 38 is slidable in the inner tube 28 in an axially relative displaceable manner via a first bearing 39 formed of a sliding member such as a sleeve or a bush. A lower end portion 38A, which becomes one end portion, of the rod 38 is attached to the bottom portion 37 of the outer tube 35. An upper end portion 38B of the rod 38, which is the other end portion, extends into the intermediate pipe 23 via an inner peripheral portion (inner peripheral side space) of the armature 29. The first bearing 39 is provided on the inner peripheral side of the core 30, for example. That is, the first bearing 39 is fixed to the armature 29 side. The first bearing 39 slides with the rod 38. The first bearing 39 corresponds to a guide portion for guiding (guiding) the armature 29 with respect to the rod 38. The rod 38 may be formed integrally with the outer tube 35 at the bottom portion 37 of the outer tube 35, or may be fixed to the bottom portion 37 by a screw, a bolt, or the like, which is separate from the outer tube 35.

The partition member 42 is provided at an upper end portion of the outer tube 35, which is one end portion. A second bearing 40, which is a sliding member such as a sleeve or a bush and is in sliding contact with the outer peripheral surface 23A of the intermediate pipe 23, is provided on the inner peripheral surface of the partition member 42. The partition member 42 and the second bearing 40 constitute a guide member that slidably supports the intermediate pipe 23 in the axial direction. That is, the partition member 42 slides on the outer peripheral surface 23A of the intermediate pipe 23 via the second bearing 40. The partition member 42 partitions the outer periphery of the intermediate pipe 23 from the outside.

A plurality of permanent magnets 43 to be excited are provided on the mover 34. That is, a plurality of annular permanent magnets 43 as magnetic members that are members generating a magnetic field are arranged in an axial direction on the inner peripheral surface 35A side of the outer tube 35. That is, the plurality of permanent magnets 43 are provided on the inner peripheral surface 35A of the outer tube 35. The plurality of permanent magnets 43 extend in the axial direction of the outer tube 35 and are formed in a ring shape. In this case, the permanent magnets 43 adjacent in the axial direction are, for example, mutually opposite in polarity. For example, a permanent magnet having an inner peripheral surface side of an S pole and an outer peripheral surface side of an N pole is disposed next to a permanent magnet having an inner peripheral surface side of an N pole and an outer peripheral surface side of an S pole.

Next, an air chamber of the actuator 11 will be described.

The actuator 11 generally has three air chambers, i.e., a variable air chamber a, a fixed air chamber B, and a variable air chamber C. The variable air chamber a (hereinafter referred to as air chamber a) is a space between the outer tube 35 and the intermediate tube 23. Specifically, the air chamber a is a space formed by the inner periphery of the outer tube 35, the intermediate tube 23, the core 30, and the outer periphery of the rod 38. The variable air chamber C (hereinafter referred to as an air chamber C) is a space inside the inner tube 28. Specifically, the air chamber C is a space formed by the inner periphery of the inner tube 28 and the outer periphery of the rod 38 (a space into which the rod 38 enters inside the inner tube 28).

The volumes of the two air chambers A, C change according to the expansion and contraction of the actuator 11. That is, the volume of the air chamber A, C increases when the actuator 11 shown in fig. 4 extends, and decreases when the actuator 11 shown in fig. 3 contracts. In this case, when the actuator 11 is contracted, as shown in fig. 3, the intermediate pipe 23 enters (is inserted into) the outer pipe 35 from the expanded state shown in fig. 4, and the volume of the air chamber a is reduced. On the other hand, when the actuator 11 is contracted, as shown in fig. 3, the rod 38 enters (is inserted into) the inner tube 28 from the expanded state shown in fig. 4, and the volume of the air chamber C decreases. The ratio of the change in volume and the amount of change in volume of the air chamber a and the air chamber C are different from each other, but the volume increases or decreases, and the same tendency is exhibited in conjunction with the stroke (expansion or contraction) of the actuator 11.

On the other hand, the fixed air chamber B (hereinafter referred to as air chamber B) is a space between the intermediate pipe 23 and the inner pipe 28. Specifically, the air chamber B is a space formed by the inner periphery of the intermediate pipe 23 and the outer periphery of the inner pipe 28. The air chamber B always has a constant volume regardless of the stroke of the actuator 11. The air chamber B can be used as a wiring path of cables (power lines) connected to the

coils

31A, 31B, and 31C of the actuator 11, for example.

However, as shown in fig. 1 and 2, an active suspension system is known as an example of a control suspension system for a railway vehicle. The active suspension system is configured by arranging an actuator 11 between the

undercarriages

3A and 3B of the vehicle 1 and the vehicle body 2 in parallel with air springs 7A to 7D (hereinafter, also simply referred to as air springs 7) serving as secondary springs. An active suspension, which is one of the control suspensions, can change the control force of the actuator 11 in real time in accordance with the vibration state of the vehicle body 2, and can improve the riding comfort of the vehicle 1. Examples of the electric linear actuator constituting the control suspension include a system in which a rotary motor is directly converted, and a system in which a linear motor as in the present embodiment is used. The control force of the actuator 11 is generated by an electromagnetic force (magnetomotive force) generated by passing a current through the

coils

31A, 31B, and 31C, and an attractive force and/or a repulsive force between the magnetic force and the permanent magnet 43 disposed so as to face the

coils

31A, 31B, and 31C.

Here, when the electric linear actuator is used in a railway vehicle, a waterproof/dustproof structure is required in order to prevent adhesion (biting into a sliding portion) or a reduction in insulation performance due to, for example, intrusion of rainwater or dust. At this time, by sealing the electric linear actuator, a waterproof/dustproof structure can be satisfied. However, in the case of a sealed electric linear actuator, there is a possibility that a change in volume of the air chamber due to the stroke becomes a problem. Specifically, the air spring force may be generated by a volume change in the electric linear actuator accompanying the stroke, and the control force of the electric linear actuator may be hindered. That is, when the electric linear actuator is configured not to inject oil into the linear motor, there is a possibility that air-induced damping occurs during operation, and the control force of the electric linear actuator is hindered. This requires an excessive force (electric power) for correcting (canceling) the air spring force, and may increase power consumption, reduce control performance, and reduce riding comfort. In other words, the performance inherent in the electric linear actuator may not be exhibited.

On the other hand, patent document 1 describes a linear actuator in which a passage (communication groove) is additionally provided between air chambers having a variable volume in order to reduce air resistance during expansion and contraction, thereby enabling air movement. In order to cope with the volume change due to the stroke, it is also conceivable to provide a sub-tank outside. However, in the case of providing the sub-tank, an additional cost and an installation space for providing the sub-tank are required. This may increase the mounting length and complicate the structure, for example. On the other hand, patent document 2 describes an electromagnetic suspension device in which the coil of an electromagnetic damper can be cooled by circulating air in one direction inside an air spring. However, in the case of this structure, an electromagnetic damper (linear actuator) needs to be provided inside the air spring, and there is a possibility that mountability (mounting freedom) is limited, for example.

In short, the electric linear actuator is preferably capable of reducing the damping by air during operation (expansion and contraction, stroke), that is, the air spring force accompanying the change in volume of the internal air chamber. In addition, in order to suppress a temperature rise of the armature (coil), it is preferable to be able to cool the armature (coil). Therefore, in the embodiment, the air in the electric linear actuator is discharged (compensated), so that the control performance (product performance) is improved by saving electric power, and the cooling of each component (armature and the like) is enabled by the air flow. In this case, the structure of the electromagnetic suspension is configured to be able to suppress a volume change inside the electromagnetic suspension as much as possible without changing the structure of the electromagnetic suspension.

That is, in the first embodiment, the communication hole 44 as the first communication hole is formed as a through hole penetrating in the radial direction in the intermediate pipe 23. In this case, when the actuator 11 is in the extended state shown in fig. 4, that is, when the outer tube 35 and the intermediate tube 23 are at the maximum length position relative to each other, the communication hole 44 is located on one end side (lower end side) of the partition member 42. The communication hole 44 communicates between the inside of the outer pipe 35 (the air chamber a between the outer pipe 35 and the intermediate pipe 23) in the first cylinder and the inside of the intermediate pipe 23 (the air chamber B between the intermediate pipe 23 and the inner pipe 28) in the second cylinder. Thus, the two air chambers A, B are connected to each other as the same space so that air can flow therethrough.

Here, as shown in fig. 3 and 4, two communication holes 44 are provided at 180 degrees intervals in the circumference. However, the number of the communication holes 44 is not limited to the illustrated example, and may be one or more on the circumference. Further, if the air resistance when the air passes through the communication hole 44 is large, there is a possibility that a large amount of air spring force remains. Therefore, in order to suppress air resistance, for example, the communication holes 44 may be provided at a plurality of locations on the circumference of the intermediate pipe 23. For example, eight communication holes 44 may be provided in the circumference and sixteen communication holes 44 may be provided in two positions in the axial direction. That is, the number and the arrangement position of the communication holes 44 can be designed (set) arbitrarily in consideration of the suppression of the air spring force and the suppression of the air resistance.

On the other hand, the larger the size (diameter) of the communication hole 44 is, the more preferable, but the strength of the intermediate pipe 23 needs to be secured. On the other hand, if the communication hole 44 is too small, the flow rate of air passing through the communication hole 44 increases, and there is a possibility that sound is generated when air passes through the communication hole 44. In order to determine the size of the communication holes 44, it is preferable to determine the diameter and the number of the communication holes 44 by obtaining the maximum flow velocity from the maximum velocity of the actuator 11 and the volume change amount at that time. In short, in the first embodiment, the air chamber a and the air chamber B are connected by the communication hole 44 of the intermediate pipe 23. Therefore, the air chamber a and the air chamber B can circulate air through the communication hole 44.

The actuator 11 according to the first embodiment is an actuator having the structure described above, and the operation thereof will be described next.

The vehicle 1 travels along the track R, for example, toward the left side in fig. 1 and 2. When the vehicle 1 travels, if vibration such as roll (yaw) or pitch (forward-backward swing) is generated, the vibration in the up-down direction at that time is detected by each of the acceleration sensors 13A to 13D. The control device 14 determines the signals detected by the acceleration sensors 13A to 13D as individual detection signals of the vehicle behavior (acceleration), and calculates a target control force to be generated by the actuators 11(11A to 11D), for example, in order to suppress the vibration of the vehicle 1. Then, the actuators 11(11A to 11D) are variably controlled in accordance with the command signals individually output from the control device 14 so that the generated control forces have characteristics along the target control force. At this time, electric power is supplied to the

coils

31A, 31B, and 31C of the armature 29 in accordance with a command signal from the control device 14.

Here, according to the first embodiment, the intermediate pipe 23 is formed with the communication hole 44 that communicates the inside of the outer pipe 35 (air chamber a) with the inside of the intermediate pipe 23 (air chamber B). Therefore, along with the stroke, air flows between the inside of the outer pipe 35 (air chamber a) and the inside of the intermediate pipe 23 (air chamber B) through the communication hole 44. This can alleviate the change in volume of the air chamber A, B in the outer tube 35 accompanying the stroke. That is, compared to a configuration in which the communication hole 44 is not provided, the air spring force associated with the volume change of the air chamber A, B in the outer tube 35 can be reduced, and the control force for correcting the air spring force (control force for canceling the air spring component) can be reduced. As a result, a desired control force can be generated with a small amount of power consumption (power saving), and the riding comfort (vibration damping performance) of the vehicle 1 in which the actuator 11 is mounted can be ensured. That is, the force to be generated between the

coils

31A, 31B, 31C and the permanent magnet 43 can be reduced by the amount by which the air spring force can be reduced. This ensures a similar ride comfort with less force than a structure in which the communication hole 44 is not provided. In other words, the riding comfort can be further improved with the same power consumption as that of the configuration in which the communication hole 44 is not provided.

In addition, along with the stroke, not only the air in the outer pipe 35 (air chamber a) but also the air in the intermediate pipe 23 (air chamber B) flows. Therefore, the armature 29 serving as a heat generating body can be cooled using not only the air in the outer tube 35 but also the air in the intermediate tube 23. This can improve the cooling performance of the armature 29 and suppress a temperature rise of the armature 29. As a result, for example, a large thrust can be generated for a long time, and a large vibration can be suppressed for a long time. In other words, from this aspect, the riding comfort (vibration damping performance) can be improved. Further, in the first embodiment, since the sub-tank is not required, it is possible to suppress an increase in the installation length and a complication in the structure.

According to the first embodiment, the rod 38 is attached to the bottom 37 of the outer tube 35, and the rod 38 slides on the first bearing 39 fixed to the armature 29 side. Therefore, by the structure in which the armature 29 is guided in the axial direction with respect to the outer tube 35 by the rod 38 at the time of stroke, the air spring force can be reduced, and the cooling performance of the armature 29 can be improved. Accordingly, the ride comfort (vibration damping performance) can be improved by the structure in which the relative displacement in the axial direction between the armature 29 of the intermediate pipe 23 (i.e., the stator 21) and the permanent magnet 43 of the outer pipe 35 (i.e., the mover 34) can be stably performed.

According to the first embodiment, the inner tube 28 disposed inside the intermediate tube 23 is fixed to the upper end portion of the intermediate tube 23, and the lower end portion 28A of the inner tube 28 extends to the armature 29. Therefore, the armature 29 can be positioned (fixed to the shaft) by the inner tube 28 extending to the armature 29, and the intermediate tube 23 and the armature 29 can be assembled well.

Next, fig. 5 and 6 show a second embodiment. A second embodiment is characterized in that a bearing member is provided at the upper end of the rod. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

In the second embodiment, a piston 51 as a bearing member is provided at an upper end portion 38B which becomes the other end portion of the rod 38. The outer peripheral surface of the piston 51 is in sliding contact with the inner peripheral surface 28C of the inner tube 28. Thereby, the piston 51 supports the rod 38 against the inner peripheral surface 28C of the inner tube 28. The piston 51 divides the interior of the inner tube 28 (the air chamber C) into two chambers, namely, an air chamber C1 located below the piston 51 (on the rod 38 side) in fig. 5 and 6 and an air chamber C2 located above the piston 51 (on the opposite side of the rod 38) in fig. 5 and 6. The piston 51 is provided with an axial communication hole 52 as a through hole extending in the vertical direction (axial direction). The axial communication hole 52 communicates between the air chamber C1 and the air chamber C2. In the second embodiment, the axial communication hole 52 is provided in the piston 51, but the axial communication hole 52 may be omitted.

The second embodiment is an embodiment in which the piston 51 is provided at the upper end portion 38B of the rod 38 as described above, and regarding its basic function, there is no significant difference from the embodiment according to the first embodiment. In particular, according to the second embodiment, the armature 29 is guided by the rod 38 not only by the first bearing 39 provided on the armature 29 but also by the inner tube 28 and the piston 51 at the time of the stroke. In addition, by the structure in which the two portions separated in the axial direction are guided in this way, the air spring force can be reduced, and the cooling performance of the armature 29 can be improved. Therefore, the ride comfort (vibration damping performance) can be improved by the structure in which the axial relative displacement between the armature 29 of the intermediate pipe 23 (i.e., the stator 21) and the permanent magnet 43 of the outer pipe 35 (i.e., the mover 34) can be stably performed. Further, the armature 29 can be positioned (fixed axis) by the inner tube 28 extending to the armature 29, and the assembling property of the intermediate tube 23 and the armature 29 can be improved.

Next, fig. 7 and 8 show a third embodiment. The third embodiment is characterized in that a second communication hole is provided in the third cylinder (inner pipe). In the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

In the first embodiment described above, the air chamber a and the air chamber B communicate with each other through the first communication hole 44. However, the air chamber C changes in volume with the stroke, but the air chamber C is not connected to the other air chamber A, B. Therefore, in the third embodiment, in addition to the communication hole 44 provided in the intermediate pipe 23, a communication hole 61 as a second communication hole is provided in the inner pipe 28. The communication hole 61 is formed in the outer periphery (cylindrical portion) of the inner tube 28. The communication hole 61 communicates between the inside of the inner tube 28 (air chamber C) in the third cylinder and the inside of the intermediate tube 23 (air chamber B) in the second cylinder. Thus, in the third embodiment, the three air chambers A, B, C are connected by the two

communication holes

44, 61. That is, the three air chambers A, B, C are connected to be able to circulate air as the same space.

Here, the axial position of the communication hole 61 is preferably located above the upper end portion 38B of the rod 38 (toward the vehicle body 2) even in the contracted state shown in fig. 7 (more specifically, the state in which the actuator 11 is completely contracted). However, when the position of the communication hole 61 is in the vicinity of the upper end 28B of the inner tube 28, the distance from the upper end 38B of the rod 38 to the communication hole 61 may be increased, which may increase air resistance. Thus, there is a possibility of residual air spring force. Therefore, in order to reduce air resistance, for example, the communication holes 61 may be provided at a plurality of positions in the axial direction of the inner pipe 28. That is, the hole diameter, the number, and the position of the communication holes 61 are preferably set to be the same as those of the communication holes 44 of the first embodiment, so that the strength of the inner tube 28 can be secured, the generation of noise due to the increase in the flow velocity of air can be suppressed, and the air resistance when the air passes through the communication holes 61 can be suppressed.

The third embodiment is an embodiment in which the second communication hole 61 is provided on the inner tube 28 as described above, and regarding its basic function, there is no significant difference from the embodiment according to the first embodiment. In particular, according to the third embodiment, since the second communication hole 61 is formed in the inner tube 28, three spaces (the air chamber a, the air chamber B, and the air chamber C) in the outer tube 35, the intermediate tube 23, and the inner tube 28 communicate as one space via the communication hole 44 and the communication hole 61. This can further reduce the air spring force and further improve the cooling performance of the armature 29.

Next, fig. 9 and 10 show a fourth embodiment. The fourth embodiment is characterized in that the first communication hole is provided in the lower end side closing portion (one end side closing portion) of the intermediate pipe. In the fourth embodiment, the same components as those in the third embodiment are denoted by the same reference numerals, and the description thereof is omitted.

In the third embodiment, the air chamber A, B, C is communicated with the communication hole 44 and the communication hole 61, thereby reducing the air spring force generated by the volume change accompanying the stroke. However, when the communication hole 44 as the first communication hole is provided in the cylindrical portion 25 of the intermediate pipe 23, the minimum length (installation length) of the actuator 11 may be increased. That is, when the first communication hole is provided on one end side (lower end side) of the partition member 42 when the actuator 11 has the maximum length, the minimum length (attachment length) of the actuator 11 can be shortened by providing the first communication hole on the lower side of the cylindrical portion 25 of the intermediate pipe 23. Thus, for example, it is conceivable to provide the core 30 of the armature 29 with a first communication hole extending in the axial direction. In this case, the air passing through the first communication hole can directly cool the

coils

31A, 31B, and 31C, and therefore, the cooling performance (cooling efficiency) of the armature 29 can be improved. However, in the case of this structure, when a large thrust force is generated with a large current, the first communication hole is provided in the core 30, and the magnetic path is reduced, so that the core 30 may be magnetically saturated, and the thrust force generation efficiency may be lowered.

Therefore, in the fourth embodiment, the communication hole 71 as the first communication hole is formed in the lower end side closing portion 24 located on the lower end side than the cylindrical portion 25 of the intermediate pipe 23. The communication hole 71 has a portion extending in the axial direction and a portion extending in the radial direction. Here, a stroke sensor 32 is provided on the lower end side closing portion 24. Therefore, the communication hole 71 is provided at a position that does not affect the sensing of the stroke sensor 32. The diameter and number of the communication holes 71 are preferably set so as to ensure the strength of the lower end side closing portion 24, suppress the generation of sound due to the increase in the flow velocity of air, and suppress air resistance when air passes through the communication holes 71.

The fourth embodiment is an embodiment in which the communication hole 71 is provided in the lower end side closing portion 24 of the intermediate pipe 23 as described above, and regarding its basic function, there is no significant difference from the embodiment according to the third embodiment. In particular, according to the fourth embodiment, the stroke sensor 32 is provided in the lower end side closing portion 24 of the intermediate pipe 23, and the communication hole 71 is formed in the lower end side closing portion 24. Therefore, the communication hole 71 is provided in the lower end side closing portion 24 of the intermediate pipe 23, whereby the installation length can be suppressed from increasing. In this case, the communication hole 71 is not provided in the core 30 (armature 29) but is provided below the cylindrical portion 25. Therefore, compared to the structure in which the first communication hole is formed in the core 30, the influence of insufficient magnetic path and magnetic saturation can be suppressed. Further, the stroke sensor 32 can be cooled by the air flowing through the communication hole 71.

Next, fig. 11 and 12 show a fifth embodiment. The fifth embodiment is characterized in that a third communication hole is provided in the outer tube. In the fifth embodiment, the same components as those in the fourth embodiment are denoted by the same reference numerals, and the description thereof is omitted.

In the fourth embodiment described above, the three air chambers A, B, C of the actuator 11 communicate with each other so as to form one air chamber. However, the air chamber A, B, C is sealed as one air chamber. Therefore, in the fifth embodiment, the communication hole 81 as the third communication hole communicating with the outside air (atmosphere) is formed in the outer tube 35. The communication hole 81 communicates between the inside and the outside of the outer tube 35. Thus, the air chamber A, B, C, which is a space in the actuator 11, communicates with the outside (in the atmosphere) via the communication hole 81. The communication hole 81 is preferably provided at a position hidden by the housing 33 even when the actuator 11 is in an extended state as shown in fig. 12 (more specifically, a state in which the actuator 11 is fully extended). Further, the diameter and number of the communication holes 81 are preferably set to be the same as those of the communication holes 44, 61, 71 described above, so that the strength of the outer tube 35 can be secured, the generation of sound due to the increase in the flow velocity of air can be suppressed, and the air resistance when the air passes through the communication holes 81 can be suppressed.

The fifth embodiment is an embodiment in which the communication hole 81 is provided on the outer tube 35 as described above, and regarding its basic function, there is no significant difference from the embodiment according to the fourth embodiment. In particular, according to the fifth embodiment, since the inside of the outer tube 35 communicates with the outside via the communication hole 81, air can be circulated to the outside (outside air). This can further reduce the air spring force and further improve the cooling performance of the armature 29. That is, when the air chamber A, B, C does not communicate with the outside, the flow of air circulates inside the actuator 11. In contrast, in the fifth embodiment, the three air chambers A, B, C communicate with the outside. Therefore, cooling can be performed by heat exchange between the inside and the outside in addition to cooling by air circulation inside, and temperature rise of each member (the armature 29 and the like) can be suppressed.

Next, fig. 13 shows a sixth embodiment. The sixth embodiment is characterized in that a strainer is provided in the third communication hole. In the sixth embodiment, the same components as those in the fifth embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

In the fifth embodiment, foreign matter such as dust or water may enter the actuator 11 from outside the actuator 11 through the communication hole 81. Further, when the intrusion of dust is significant, the actuator 11 may be stuck. When water intrusion is significant, the insulating performance of the

coils

31A, 31B, and 31C may be reduced.

Therefore, in the sixth embodiment, the filter 91 that enables bidirectional flow between the inside and the outside of the outer tube 35 is provided in the communication hole 81 that is the third communication hole communicating with the outside air. That is, the communication hole 81 has the filter 91. The filter 91 can be fixed in the communication hole 81 by bonding, for example. In consideration of replacement of the filter 91, the filter 91 may be detachably attached (engaged) to the communication hole 81. As the filter 91, for example, a filter made of a mesh material, a filter made of a sintered member, or the like can be used. The pore size (filtration pore size) and thickness of the filter 91 are preferably selected according to the actual use conditions of the actuator 11. However, when the pore diameter of the filter 91 is reduced or when the thickness of the filter 91 is increased, there is a possibility that air resistance (pressure loss) increases. Therefore, the filter 91 is preferably selected in consideration of air resistance and filtering performance (trapping performance).

The sixth embodiment is an embodiment in which the filter 91 is provided in the communication hole 81 as described above, and regarding its basic function, there is no significant difference from the embodiment according to the fifth embodiment. In particular, according to the sixth embodiment, the filter 91 can suppress the intrusion of foreign matter such as water or dust from the outside. This ensures water resistance and dust resistance even in a configuration in which the intake air can be taken out through the communication hole 81.

That is, the actuator 11 can prevent the intrusion of foreign matter such as water or dust from the outside by sealing the air chamber A, B, C. However, if the air chamber A, B, C of the actuator 11 is made to communicate with the outside air in order to further reduce the air spring force, foreign matter may enter the actuator 11 from the outside. In contrast, in the sixth embodiment, since the filter 91 is provided in the communication hole 81, the air spring force can be further reduced and the intrusion of foreign matter can be suppressed. When the actuator 11 is contracted, air in the actuator 11 is exhausted (discharged) through the filter 91, and when the actuator 11 is expanded, outside air is sucked (sucked) into the actuator 11 through the filter 91. Since the actuator 11 is finally returned to the mounting length, the total value of the displacement amounts of the reduction is the same as the total value of the displacement amounts of the extension. Therefore, the filter 91 provided in the actuator 11 can reduce the amount of dust or dirt accumulated in the filter 91 as compared with a normal filter provided on the intake side.

In the sixth embodiment, the filter 91 is provided in the communication hole 81. On the other hand, although not shown, for example, filters may be provided in the communication holes 61 and 71 other than the communication hole 81. In this case, the pore diameter and thickness of the filter 91 in the communication hole 81 and the pore diameter and thickness of the filter in the communication holes 61 and 71 can be appropriately designed. For example, the pore diameter of the filter 91 in the communication hole 81 may be increased to actively exchange the air in the air chamber a with the outside air. In this case, the air hole diameter of the filter in the communication holes 61 and 71 may be set smaller than the air hole diameter of the filter 91 in the communication hole 81, thereby suppressing the intrusion of foreign matters such as water and dust into the air chamber B, C.

In the case of such a configuration, even if foreign matter intrudes into the air chamber a through the communication hole 81, the filter provided in the communication hole 71 can suppress intrusion into the air chamber B. Even when foreign matter enters the air chamber B, the filter provided in the communication hole 61 can suppress the entry into the air chamber C. That is, not only the filter 91 is provided in the communication hole 81 but also the filters are provided in the communication holes 61 and 71, and the respective filters 91 are set to have air hole diameters or thicknesses corresponding to the respective air chambers A, B, C. This can ensure waterproof and dustproof properties suitable for the respective air chambers A, B, C, and can reduce the air spring force due to the volume change accompanying the stroke.

Next, fig. 14 shows a seventh embodiment. A seventh embodiment is characterized in that a magnet is provided in the vicinity of the third communication hole provided in the outer tube. In the seventh embodiment, the same components as those in the sixth embodiment are denoted by the same reference numerals, and the description thereof is omitted.

In the sixth embodiment described above, the filter 91 is provided in the communication hole 81, and thus, even if the communication hole is configured to communicate with the outside air, the waterproof property and the dustproof property can be secured. However, since the pore diameters of the filter 91 are different, foreign matter (dust, etc.) may enter the filter 91. Here, for example, when dust entering the inside is nonmagnetic powder (nonmagnetic component), it is considered that the nonmagnetic powder stays in a portion (for example, a groove portion or a lower portion) in the actuator 11, which is likely to be accumulated. On the other hand, when the dust is magnetic powder (magnetic component), it is considered that the magnetic powder adheres to each permanent magnet 43 of the actuator 11. As long as the magnetic force of each permanent magnet 43 continues, the magnetic powder once adhered may continue to adhere to each permanent magnet 43, and may be deposited with the passage of time. When the accumulated magnetic powder exceeds a certain threshold value, the magnetic powder may contact the core 30 or the

coils

31A, 31B, and 31C, and damage the surfaces of these components. This may reduce the insulation performance of the

coils

31A, 31B, and 31C.

Therefore, in the seventh embodiment, a foreign material attracting magnet 101 (magnet) for adhering magnetic powder intruding into the actuator 11 is provided on the inner peripheral side of the outer tube 35. The attachment position of the foreign-substance-attracting magnet 101 is preferably in the vicinity of the communication hole 81. For example, the foreign-substance-attracting magnet 101 is preferably provided on the inner circumferential surface 35A of the outer tube 35 or on the inner surface of the partition member 42 in the vicinity of the communication hole 81. However, the position and size of the foreign-substance-attracting magnet 101 are set so as not to contact the core 30 or the

coils

31A, 31B, and 31C of the armature 29 even when the actuator 11 is in the extended state, that is, the foreign-substance-attracting magnet 101 is close to the armature 29. The number of foreign-substance attracting magnets 101 is preferably equal to or greater than the number of communicating holes 81. The foreign-substance attracting magnet 101 is preferably a neodymium magnet or a ferrite magnet, and is preferably selected from a variety according to the use temperature range.

The seventh embodiment is an embodiment in which the foreign-substance-attracting magnet 101 is provided in the vicinity of the communication hole 81 as described above, and regarding its basic function, there is no significant difference from the embodiment according to the sixth embodiment. In particular, in the seventh embodiment, since the magnetic powder that has entered through the communication hole 81 is collected (attracted) by the foreign-substance adsorbing magnet 101, it is possible to suppress the magnetic powder from adhering to each permanent magnet 43. This can suppress damage caused by contact between the

coils

31A, 31B, and 31C and the magnetic powder, and can ensure good insulation performance.

In the seventh embodiment, an example is described in which the filter 91 is provided in the communication hole 81 and the foreign-substance-attracting magnet 101 is provided in the vicinity of the communication hole 81. However, the present invention is not limited to this, and for example, a configuration may be adopted in which a foreign substance adsorption magnet is provided but a filter is not provided. That is, the filter may be omitted.

In the first embodiment, an example of a configuration in which the rod 38 is attached to the outer tube 35 as the first cylinder is described. However, the present invention is not limited to this, and the lever (and the guide portion) may be omitted, for example. The same applies to the second to seventh embodiments.

In the first embodiment, an example of a configuration including the inner tube 28 as the third cylinder is described. However, the present invention is not limited to this, and for example, the inner tube may be omitted. The same applies to the third to seventh embodiments.

In the first embodiment, an example in which the stroke sensor 32 is provided in the one end side closing portion 24 of the intermediate pipe 23 is described. However, the present invention is not limited to this, and for example, the stroke sensor may be provided at a position offset from the one end side closing portion. The same applies to the second to seventh embodiments.

In each embodiment, an example is described in which the sprung member (for example, the vehicle body 2) of the vehicle 1 is set as the fixed side and the unsprung member (for example, the

undercarriages

3A and 3B and the wheels 4) of the vehicle 1 is set as the movable side. That is, the description has been given of an example in which the first member connected to the

chassis

3A, 3B serving as the unsprung member of the vehicle 1 is the mover 34, and the second member connected to the vehicle body 2 serving as the sprung member of the vehicle 1 is the stator 21. However, the present invention is not limited to this, and for example, the unsprung member of the vehicle may be set to the fixed side and the sprung member of the vehicle may be set to the movable side. That is, the first member or the second member connected to the unsprung member (chassis) of the vehicle may be used as the stator, and the first member or the second member connected to the sprung member (vehicle body) of the vehicle may be used as the mover. In other words, the first member may be a stator and the second member may be a mover, or the first member may be a mover and the second member may be a stator.

In each embodiment, an example is described in which one of two members to which the actuator 11 as an electric linear actuator is attached is used as the

chassis

3A, 3B, and the other of the two members is used as the vehicle body 2. However, the present invention is not limited to this, and for example, one of the two members to which the electric linear actuator is attached may be a vehicle body, and the other of the two members may be an undercarriage.

In each embodiment, an example in which the actuator 11 is disposed in the vertical direction between the vehicle body 2 and the

undercarriages

3A and 3B is described. However, the present invention is not limited to this, and for example, an electric linear actuator may be disposed between the vehicle body and the underframe in the left-right direction.

In each embodiment, an example in which the actuator 11 is disposed between the vehicle body 2 and the

undercarriages

3A and 3B is described. However, the present invention is not limited to this, and for example, the electric linear actuator may be disposed between the underframe (underframe frame) and the bearing housing (wheel, wheel axle).

In each embodiment, an example in which the air spring 7 and the actuator 11 constitute an electric suspension (electromagnetic suspension) for a railway vehicle is described. That is, in each embodiment, an example in which the actuator 11 is mounted on the railway vehicle 1 is described. However, the present invention is not limited to this, and may be mounted on a vehicle other than a railway vehicle such as an automobile. Further, the present invention can be widely applied to various electric linear actuators mounted on various machines, buildings, and the like, which are vibration sources. Further, the embodiments are examples, and it is obvious that structures shown by different embodiments can be partially replaced or combined.

As the electric linear actuator according to the embodiment described above, for example, an electric linear actuator of the following type can be considered.

As a first aspect, an electric linear actuator mounted between two members that move relative to each other and generating a control force, the electric linear actuator comprising: a first cylinder having a bottomed cylindrical shape having a bottom at one end portion attached to one of the two members, the first cylinder extending in an axial direction; a second cylinder extending in an axial direction of the first cylinder, located radially inside the first cylinder, having another end attached to the other of the two members, and having both ends closed; a partition member provided at the other end of the first cylinder, sliding on an outer peripheral surface of the second cylinder, and partitioning the outer periphery of the second cylinder from the outside; a plurality of permanent magnets formed in a ring shape on an inner peripheral surface of the first cylinder, the permanent magnets extending in an axial direction of the first cylinder; an armature provided at one end of the second cylinder; the second cylinder is formed with a first communication hole which is located closer to one end side than the partition member when the first cylinder and the second cylinder are at the maximum relative length positions, and communicates the inside of the first cylinder with the inside of the second cylinder.

According to the first aspect, the air flows between the first cylinder and the second cylinder through the first communication hole along with the stroke. Therefore, the air spring force associated with the change in the volume of the air chamber in the first cylinder can be reduced, and the control force for correcting the air spring force can be reduced. This makes it possible to generate a desired control force with a small amount of power consumption (power saving), and to ensure, for example, the riding comfort (vibration damping performance) of a vehicle in which the electric linear actuator is mounted. In addition, along with the stroke, not only the air in the first cylinder but also the air in the second cylinder flows. Therefore, the armature serving as a heating element can be cooled using not only the air in the first cylinder but also the air in the second cylinder. This can improve the cooling performance of the armature and suppress the temperature rise of the armature. As a result, for example, a large thrust can be generated for a long time, and a large vibration can be suppressed for a long time. In other words, from this aspect, the riding comfort (vibration damping performance) can be improved.

As a second aspect, in the first aspect, the armature is annular, and an inner peripheral portion thereof is connected to an interior of the second cylinder, and the electric linear actuator includes: a rod having one end attached to a bottom of the first cylinder and the other end extending into the second cylinder through an inner peripheral portion of the armature; and a guide portion fixed to the armature side and sliding with the rod. According to the second aspect, the air spring force can be reduced and the cooling performance of the armature can be improved by the structure in which the armature is axially guided by the rod with respect to the first cylinder at the time of stroke. Thus, the riding comfort (vibration damping performance) can be improved by the structure in which the axial relative displacement between the armature of the second cylinder and the permanent magnet of the first cylinder can be performed more stably.

As a third aspect, in the second aspect, the electric linear actuator includes: a third cylinder which is disposed inside the second cylinder, is fixed to the other end of the second cylinder, has one end extending to the armature, and into which the rod is inserted; and a bearing member provided at the other end of the rod and supporting the rod with respect to an inner peripheral surface of the third cylinder. According to the third aspect, the air spring force can be reduced and the cooling performance of the armature can be improved by the structure in which the armature is also guided by the rod via the bearing member of the third cylinder and the rod. Thus, the riding comfort (vibration damping performance) can be improved by the structure in which the axial relative displacement between the armature of the second cylinder and the permanent magnet of the first cylinder can be performed more stably. Further, since the armature can be positioned (the shaft can be determined) by the third cylinder extending to the armature, the assembling property can be improved.

As a fourth aspect, in the third aspect, a second communication hole that communicates between the third cylinder and the second cylinder is formed in an outer periphery of the third cylinder. According to the fourth aspect, the three spaces in the first cylinder, the second cylinder, and the third cylinder communicate with each other via the first communication hole and the second communication hole. In this way, the air spring force can be reduced and the cooling performance of the armature can be improved.

As a fifth aspect, in any one of the first to fourth aspects, a stroke sensor that detects a relative position of the armature is provided at one end side closing portion of the second cylinder, and the first communication hole is formed at the one end side closing portion. According to the fifth aspect, the first communication hole is provided in the one end side closing portion of the second cylinder, whereby the mounting length can be suppressed from increasing. In addition, the stroke sensor can be cooled by air flowing through the first communication hole.

As a sixth aspect, in any one of the first to fifth aspects, a third communication hole that communicates between the inside and the outside of the first cylinder is formed in the first cylinder. According to the sixth aspect, since the first cylinder communicates with the outside via the third communication hole, air can be circulated to the outside. This can further reduce the air spring force and further improve the cooling performance of the armature.

As a seventh aspect, in the sixth aspect, a strainer capable of allowing bidirectional flow between the inside and the outside of the first cylinder is provided in the third communication hole. According to the seventh aspect, the filter can suppress the intrusion of foreign matter such as water or dust from the outside. Thus, even in a configuration in which the external air can be taken out and introduced through the third communication hole, the waterproof and dustproof properties can be ensured.

The present invention is not limited to the above-described embodiments, and various modifications are also included. For example, the above-described embodiments are described in detail to explain the present invention easily and understandably, and are not limited to having all of the structures described. In addition, a part of the structure of one embodiment may be replaced with the structure of another embodiment, or the structure of another embodiment may be added to the structure of one embodiment. Further, a part of the configuration of each embodiment can be added, deleted, or replaced with another configuration.

The application claims the priority of the Japanese patent application No. 2019-129144, which is applied on 7, 11 and 2019. All disclosures of the japanese laid-open application No. 2019-129144, filed on 7/11/2019, including the specification, claims, drawings and abstract, are incorporated herein by reference in their entirety.

Description of the reference numerals

2 vehicle body (two parts)

3A, 3B Chassis (two parts)

11. 11A-11D actuator (electric linear actuator)

23 middle tube (second jar)

23A outer peripheral surface

24 lower end side closing part (one end side closing part)

28 inner tube (third jar)

28A, 38A lower end (one end)

28B, 38B upper end portion (the other end portion)

28C, 35A inner peripheral surface

29 armature

32 stroke sensor

35 outer tube (first jar)

37 bottom part

38 rod

39 first bearing (guide part)

42 partition member

43 multiple permanent magnets

44. 71 communication hole (first communication hole)

51 piston (bearing parts)

Communicating hole 61 (second communicating hole)

81 communication hole (third communication hole)

91 filter

Claims

1. An electric linear actuator mounted between two members that move relative to each other and generating a control force, comprising:

a first cylinder having a bottomed cylindrical shape having a bottom at one end portion attached to one of the two members, the first cylinder extending in an axial direction;

a second cylinder extending in an axial direction of the first cylinder, located radially inside the first cylinder, having another end attached to the other of the two members, and having both ends closed;

a partition member provided at the other end of the first cylinder, sliding on an outer peripheral surface of the second cylinder, and partitioning the outer periphery of the second cylinder from the outside;

a plurality of permanent magnets formed in a ring shape on an inner peripheral surface of the first cylinder, the permanent magnets extending in an axial direction of the first cylinder;

An armature provided at one end of the second cylinder;

the second cylinder is formed with a first communication hole which is located closer to one end side than the partition member when the first cylinder and the second cylinder are at the maximum relative length positions, and communicates the inside of the first cylinder with the inside of the second cylinder.

2. The electric linear actuator of claim 1,

the armature is annular, an inner peripheral portion of the armature is connected to an inside of the second cylinder,

the electric linear actuator includes:

a rod having one end attached to a bottom of the first cylinder and the other end extending into the second cylinder through an inner peripheral portion of the armature;

and a guide portion fixed to the armature side and sliding with the rod.

3. The electric linear actuator of claim 2,

the electric linear actuator includes:

a third cylinder which is disposed inside the second cylinder, is fixed to the other end of the second cylinder, has one end extending to the armature, and into which the rod is inserted;

and a bearing member provided at the other end of the rod and supporting the rod with respect to an inner peripheral surface of the third cylinder.

4. The electric linear actuator of claim 3,

a second communication hole for communicating the third cylinder with the second cylinder is formed in the outer periphery of the third cylinder.

5. The electric linear actuator according to any of claims 1 to 4,

a stroke sensor for detecting a relative position of the armature is provided at one end side closing portion of the second cylinder,

the first communication hole is formed in the one-end-side closed portion.

6. The electric linear actuator according to any of claims 1 to 5,

the first cylinder is provided with a third communication hole for communicating between the inside and the outside of the first cylinder.

7. The electric linear actuator of claim 6,

the third communication hole is provided with a filter that allows bi-directional flow between the inside and the outside of the first cylinder.