JPS63163042A - Linear actuator - Google Patents

Abstract

PURPOSE:To permit linear motion without using any fluid controller by attracting a brake shoe made of a magnetic body to a magnetic field to reduce a brake force so that a slide rod can slide. CONSTITUTION:In a housing 12 of a linear actuator 10 is disposed a slide rod 14 moving straight. An electromagnetic coil 26 is wound along the inner periphery of housing 12, while holding through a spring 22 a brake shoe 20 made of a magnetic body or a brake shoe drive portion. The brake shoe 20 of magnetic body is absorbed by a magnetic force to the housing 12 side provided substantially with the coil 26 only when current is supplied to the coil 26. And a brake force for the rod 14 is reduced by the spring pressure while the rod 14 is moved straight by axial electromagnetic force under the action of reducing a frictional force.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a linear actuator, in particular:
In a linear actuator in which a rod is disposed in a housing and the rod is caused to perform a linear motion, a coil is wound around the inner circumference of the housing and a brake shoe made of a magnetic material or a brake shoe driving member is held via a spring. Only when a current is passed through the coil, the magnetic brake shoe or the brake shoe driving member is attracted by magnetic force to the housing side where the coil is arranged, thereby weakening the braking force on the rod due to the spring pressure. and the opening 7 due to the electromagnetic force in the axial direction.
The present invention relates to a linear actuator configured to drive a motor linearly while reducing frictional force.

In recent years, with the technological development of automatic machines such as robots, the importance of linear actuators that perform accurate linear motion is becoming more and more recognized. In particular, linear actuators for transporting workpieces in assembly robots, which require high positioning accuracy, are being widely used.

As mentioned above, these linear actuators have various features such as not only accurate positioning accuracy, but also reliability, long life, compactness, uniformity of operating force, easy change of direction of movement, and high bending rigidity. It is required to have the following characteristics.

In order to meet these demands, various linear actuators have been proposed in the past. An example of this is the device disclosed in Japanese Patent Publication No. 56-14883. In this prior art linear actuator, a linear ball bearing is arranged in the longitudinal direction of the inner circumference of the housing, and a slide rod in which a cylinder is assembled by engaging the bearing is arranged, and the slide rod is moved in the axial direction. For sliding, a plurality of orifices are provided at appropriate locations in the housing, and operating force is applied to the slide rod using hydraulic or air pressure to achieve positional accuracy and smooth sliding.

However, since the linear actuator requires a complete sealing effect with respect to the housing, the linear actuator has a sealed structure, which causes troublesome maintenance and inspection, and a lack of reliability.

Furthermore, since a hydraulic or pneumatic control device is required, the overall size of the device becomes large, and the cost of the hydraulic or pneumatic control device is expensive, making it difficult to be economical. are doing.

Furthermore, since the positional accuracy of the linear actuator is maintained by operating force related to hydraulic pressure or pneumatic pressure, the slide rod becomes unbraking when the power to the control device related to hydraulic pressure, pneumatic pressure, etc. It has been pointed out that it is difficult to ensure safety when the system is turned off, and that there is a risk of malfunction.

The present invention has been made in order to overcome all of the above-mentioned disadvantages, and is a linear actuator in which a rod is disposed in a housing and performs linear motion.A coil is wound around the inner circumference of the housing, and a magnetic material is A brake shoe or a brake shoe driving member consisting of a brake shoe or a brake shoe driving member is attached via a spring, and when the coil is not energized, the brake shoe and the rod are substantially engaged under the pressure of the spring, and a current is applied to the coil. When energized, the magnetic brake shoe or the brake shoe driving member is attracted by magnetic force to the housing side where the coil is arranged, weakening the braking force of the rod due to the spring pressure, and The magnetic field generates eddy currents in the rod, allowing the rod to move linearly under the effect of reducing frictional forces, thereby eliminating the need for hydraulic or pneumatic pressure fluids and, as a result, requiring the use of expensive fluid control devices. It is an object of the present invention to provide a linear actuator that is capable of performing a desired linear movement without any problems and has self-retaining properties.

In order to achieve the above object, the present invention includes a plurality of coil units and a magnetic body as an iron core arranged inside a housing, and a slide rod penetrating the coil units and the magnetic body so as to be freely displaceable. In the linear actuator, a brake shoe or a brake shoe driving member made of a magnetic material is disposed via a spring in correspondence to at least a part of the outer periphery of the rod, and when the alternating current is not applied to the coil, the spring is disposed. The pressure brings the brake shoe into contact with the slide rod to brake it, while when the alternating current is applied, the brake shoe or the brake shoe driving member is attracted by the magnetic field generated between the iron core and the spring. The slide rod is configured to slide by weakening the braking force of the brake shoe against the elastic force of the brake shoe.

Next, preferred embodiments of the linear actuator according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an embodiment of the present invention, and shows a perspective view of a linear actuator having one slide rod. That is, in FIG. 1, reference numeral 10 indicates a linear actuator, and the linear actuator IO basically consists of a housing 12 and a slide rod 14 made of a conductor such as aluminum or copper. and,
Contacts 16a to 16c for inputting electrical signals are attached to the housing 12 on a terminal block 18.

On the other hand, FIG. 2 shows a side sectional view of the linear actuator 10. In FIG. 2, the same components as those shown in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

Therefore, in FIG. 2, reference numerals 20a to 2On are brake shoes made of magnetic material, and the brake shoes 20a to 20n are springs 22a to 22n, respectively.
The other ends of the springs 22a to 22n are locked to an iron core 24 made of a magnetic material. Donut-shaped coils 26a to 26f are embedded in the iron core 24 and are housed inside the housing 12.

Next, a rectangular cap member 28 is attached to both ends of the housing 12, and a ring member 29 is fitted into a circular hole defined in the center of the cap member 28. The slide rod 14 is inserted into the hole defined in the ring member 29. Here, a linear ball bearing may be provided in the hole in which the slide rod 14 of the ring member 29 fits, if necessary.Also, although not shown, the donut-shaped coils 26a to 26f may be arranged in a predetermined manner as described later. The electrical signal input contacts 16a to 16c are connected to the electrical signal input contacts 16a to 16c.

FIG. 3 is a cross-sectional view of the machine along line mm in FIG. 2.

In this figure, it can be understood that the brake shoe 20 in this embodiment has a four-sided configuration with a fan-shaped longitudinal section.

The linear actuator according to the present invention is basically constructed as described above, and its operation and effects will be explained next.

As can be easily understood from FIGS. 1 to 3, in the linear actuator 10 according to the present invention, the slide rod 14 and the housing 12 are slidable relative to each other. That is, in the present invention, the housing 12 is fixed or
Whether or not the slide rod 14 is fixed can be selected as appropriate depending on the user's needs, and in that case, it is possible to use the other fixed component as a movable body. Here, for convenience of explanation, the housing 12
is fixed to a fixed body (not shown).

By the way, in the configuration in which the donut-shaped coils 26a to 26f are arranged on the inner periphery of the housing 12 shown in FIG.
In order to move the slide rod 14 from side to side, an electromagnetic force may be applied to the slide rod 14. This can be done by passing an appropriate alternating current through the donut-shaped coils 26a to 26f. Next, the direction of action of the electromagnetic force induced by passing an appropriate alternating current through the donut-shaped coils 26a to 26f will be considered.

First, donut-shaped coils 26a to 26f shown in FIG.
Connect as shown in Figure 4a. In the circuit connection diagram of FIG. 4a, reference symbols 40a to 4M are fuses that melt at a predetermined temperature,
This is to protect the coil from burnout, etc., but these are not the gist of the present invention and will not be described in detail.

Here, in order to make the above-mentioned wiring connections easier to understand, the circuit connection diagrams are rearranged and rearranged as shown in Figure 4. As can be easily understood from the circuit connection diagram in FIG. 4, this circuit is equivalent to a Δ-connection load in three-phase AC. Therefore, as shown in FIG. 4a, a symmetrical three-phase AC power source 36 is connected to the contacts 16a to 16c. Note that here, reference symbol E represents the grounding of the symmetrical three-phase AC power supply 36.

Next, when the current from the symmetrical three-phase AC power supply 36 is applied to the donut-shaped coils 26a to 26f, the direction of the magnetic flux interlinking with the slide rod 14, and the eddy current generated in the first slide rod 14 as well. The direction of the magnetic flux and the direction of the electromagnetic force, the so-called Lorentz force, generated by these magnetic fluxes and eddy currents will be explained.

For symmetrical three-phase AC, if the period of power of any one phase is T, then
The electromotive force of other phases has the same waveform and the time is T/3.2T/
The same process will be repeated with a delay of 3. Therefore,
Now, assuming T=3t, the direction of the magnetic field generated by the donut-shaped coils 26a to 26f at times t+, 2t+ and 13t+ is shown macroscopically by the direction of the magnetic field lines drawn above FIG. 3a. In the diagram of the direction of the magnetic field drawn above FIG. 3a, the symbol S represents the south pole of the magnet, and the symbol N represents the north pole of the magnet.

The arrow drawn between the S pole and the N pole represents the direction of the lines of magnetic force.

At this time, first, magnetic poles forming the lines of magnetic force appear on the iron core 24, so that the brake shoes 20a to 2On, etc. made of the magnetic material are
is attracted to. This suction action causes the brake shoe 20 to
Since the parts a to 20n are detached from the slide rod 14, the slide rod 14 becomes slidable.

On the other hand, as can be easily understood from the diagram depicting the direction of the lines of magnetic force drawn above FIG. 4a, the magnetic field is
Since the slide rod 14 moves along the axial direction, at this time, an eddy current is generated in the slide rod 14 in a substantially spiral shape. In this case, the slide rod 14 receives electromagnetic force in the axial direction,
As a result, a linear motion is performed in the axial direction.

Note that the moving direction, moving speed, moving distance, etc. of the slide rod 14 can be easily controlled by providing a three-phase power supply reversing switch and a power supply device whose voltage and frequency are variable. In addition, when power is no longer supplied, the brake shoe 20
a is pressed by the spring 22a to brake the slide rod 14.

FIG. 5 is a sectional view of a linear actuator according to another embodiment of the present invention, in which reference numeral 52 is a moving member made of a magnetic material, and the moving member 52 includes a Kumadori coil 5.
0 is buried and comes into contact with the iron core 24 by the spring 22.

Therefore, when the power is not energized, the repulsive force of the spring 22 causes the moving member 52 to move toward the ball bearings 58a and 58 in the direction of the arrow.
It moves while sliding in contact with b. And brake shoe 5
When the roller member 54 slidably disposed on the cap member 28c comes into contact with the projection 28d of the cap member 28c, the roller member 5
4 receives a force in the normal direction from the moving member 52 to the slide rod 14, and the brake shoe 56 comes into contact with the slide rod 14 due to the pressure in the normal direction. the result,
The slide rod 14 is braked by the frictional force.

When energized, the movable member 52 receives a force attracted by the iron core 24, and at this time, the slide rod 14 becomes slidable.

As described above, according to the present invention, a magnetic brake shoe and a coil are arranged on the inner periphery of the housing of a linear actuator, and by passing an alternating current through the coil, the brake shoe is separated from the slide rod and the rod is attached to the brake shoe. A linear actuator can be obtained in which an electromagnetic force in the axial direction is generated and, as a result, the electromagnetic force allows linear movement of the rod. Furthermore, according to the present invention, there is no need for a fluid power medium related to hydraulic pressure or pneumatic pressure, so there is no need for a sealed structure. Moreover, the brake shoes allow immediate braking even in the event of a momentary power cut, which has the effect of improving safety and avoiding malfunctions. Furthermore, since the rod can be moved by electromagnetic force, it is possible to considerably reduce the contact area between the rod and the inner circumference of the housing. As a result, a linear actuator with low frictional force can be obtained.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and various improvements and changes in design can be made without departing from the gist of the present invention. Of course.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a linear actuator according to the present invention, FIG. 2 is a side sectional view of a linear actuator according to the present invention, FIG. 3 is a cross-sectional view of a linear actuator according to the present invention, and FIG. 4 is a linear actuator. FIG. 5 is a longitudinal section of another embodiment of the linear actuator according to the present invention. DESCRIPTION OF SYMBOLS 10... Linear actuator 12... Housing 14... Slide rod 16a-16C... Contact 20... Brake shoe 22a-22n... Spring 24...
・Iron core 26a to 26f...Coil 36...Symmetrical 3-phase AC power supply

Claims (3)

[Claims] (1) A linear actuator in which a plurality of coil units and a magnetic body as an iron core are disposed inside a housing, and a slide rod is disposed movably through the coil units and the magnetic body. A brake shoe or a brake shoe driving member made of a magnetic material is arranged via a spring so as to correspond to at least a part of the outer periphery of the rod, and when the alternating current is not applied to the coil, the brake shoe is moved by the spring pressure to the slide rod. On the other hand, when an alternating current is applied, the brake shoe or brake shoe driving member is attracted by the magnetic field generated between the iron core and brakes against the elastic force of the spring. A linear actuator characterized in that the slide rod is configured to slide by weakening the braking force of the shoe. (2) In the actuator according to claim 1, the brake shoe driving member includes a ring having a tapered hole on one side, a Kumadori coil is encircled on the other side of the ring, and a spring is attached to the other side of the ring. A roller member is disposed inside the tapered hole portion, and the roller member is configured to engage with a cap member forming an end portion of the housing. When the alternating current is not applied, the brake shoe driving member moves in a direction parallel to the axis of the slide rod while one end thereof slides in contact with the outer periphery of the housing due to the elastic force of the spring, thereby moving the roller member toward the end of the housing. and, on the other hand, when the roller member comes into contact with the cap member and stops, the slide rod is braked via the roller member by a force in a normal direction generated in the brake shoe drive member. (3) The linear actuator according to claim 2, wherein the cap member is provided with a protrusion that engages with a roller member and whose displacement is regulated.