JP2022057253A - Linear actuator - Google Patents

Abstract

To provide a linear actuator which is light-weight and achieves high precision and low costs and yet enables a long operation stroke.SOLUTION: A linear actuator 100 includes: a motor 10; a rotary shaft 20 which transmits rotational force of the motor 10; a guide part 40 which guides the rotary shaft 20; and a stage 50 which supports the guide part 40. The guide part 40 has: guide rails 42 which pivotally support the rotary shaft 20; and rod-like members 45 each of which is provided between the guide rails 42 and in which at least a surface is made of a resin.SELECTED DRAWING: Figure 1

Description

The present invention relates to a linear actuator that converts a rotary motion of a motor into a linear motion, and particularly to a linear actuator that can be significantly reduced in size.

In recent years, the demand for linear actuators has been increasing due to the development of the robot industry accompanying the needs for automation. A linear actuator is a device that converts the rotational motion of a motor into a linear motion using a feed screw or a ball screw. In actual use, a linear actuator is mainly used to attach an object to a stage to be linearly moved, reciprocate the stage, and stop the attached object at a target position. The largest market for this linear actuator is a factory where various assembly operations are performed. Further, the general-purpose size of the linear actuator is a stroke of 100 mm to 1000 mm. Further, the required load capacity of the linear actuator at that time is 5 kg to 30 kg.

If the linear motion is performed only with the feed screw and ball screw mentioned above, rattling occurs. Therefore, we are trying to reduce friction by using ball bearings and rollers to slide on the rails, and to prevent rattling by using restraints such as set screws. Further, when rolling such a ball bearing or roller, it is important that the ball bearing or roller does not pop out from the left, right, front, back, up and down, and no gap is formed. Therefore, a precise guide is used for the linear actuator to solve the problem of rolling ball bearings and rollers.

It is also important to give the guide strength. This is because ball bearings and rollers are also usually made of metal, and the load capacity of the object is also applied to the guide. That is, if the strength of the guide is low, the guide is quickly worn by the rolling motion of the ball bearing or the roller, and the life is shortened. Therefore, the guide is given strength by performing "quenching" and "tempering" operations on the guide.

However, a challenge emerges here. Originally, iron is processed by cutting and the like is subjected to "quenching" and "tempering" work to manufacture a guide, but the dimensions change before and after this work. If you want to manufacture a high-precision linear actuator, it may be necessary to consider many conditions for such baking work.

As mentioned above, until now, the concept of "guide" = "baking work" has existed, but as linear actuators become smaller, the weight becomes lighter, so the demand for durability decreases, and the need for baking work for guide production decreases. Will disappear. When the need for baking work is eliminated, the durability can be sufficiently maintained even if the guide is made of general-purpose steel such as stainless steel. Further, in this case, if the product is manufactured while paying attention to the processing accuracy, it is possible to manufacture a product with very little play and high accuracy.

With the development of the robot market, energy saving and miniaturization will be required in the future. Alternatively, in the field of biotechnology research dealing with cells, further fine manipulation is required.

A linear actuator as described in Patent Document 1 has been proposed as an attempt to reduce the size. The linear actuator described in Patent Document 1 is provided with a mover having a function as a linear motor and a function as a guidance mechanism such as a linear guide, and is intended to be miniaturized and lightweight. ..

Japanese Unexamined Patent Publication No. 2005-185077

However, although the linear actuator described in Patent Document 1 is intended to be miniaturized and lightened, there is no mention of further miniaturization and weight reduction, and it has been used in a high-precision linear actuator. There is no mention of expensive parts such as cross roller guides that are complicated to manufacture. In addition, by finely processing the pitch of the lead screw and increasing the number of rotation steps by improving the functionality of the motor and motor driver, a stroke of several tens of mm is realized while achieving resolution and accuracy up to 10 nanometers. At present, there is no inexpensive linear actuator of about tens of thousands of yen.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to review the cross roller guide and to provide a compact linear actuator which is advantageous in terms of both accuracy and cost.

The linear actuator according to the present invention includes a motor, a rotation shaft that transmits the rotational force of the motor, a guide portion that guides the rotation shaft, and a stage that supports the guide portion, and the guide portion includes the motor. It has a plurality of guide rails that rotatably support the rotating shaft, and a rod-shaped member having at least a surface made of resin provided between the guide rails.

The linear actuator according to the present invention is provided with three guide rails and two rod-shaped members, and the guide rail provided in the center of the guide rails is made longer than the left and right guide rails. , The thing.

Further, in the linear actuator according to the present invention, the guide rail is made of general-purpose steel.

Further, the linear actuator according to the present invention is provided with a coupling having a slit formed between the motor and the rotating shaft.

The linear actuator according to the present invention is configured to be compact and lightweight, and since the rod-shaped member constituting a part of the guide portion is made of resin, it has advantages in terms of both cost and accuracy. Will occur.

Since the linear actuator according to the present invention is provided with a rotary shaft guide composed of three guide rails and two rod-shaped members, it is possible to reduce the number of parts as compared with the conventional one. It has become.
In the linear actuator according to the present invention, since the guide rail forming a part of the guide portion is made of general-purpose steel such as stainless steel, further weight reduction can be realized.

Since the linear actuator according to the present invention is provided with a coupling having a slit formed as a joint, it becomes possible to transmit the rotational force to the rotary shaft while suppressing the rattling of the rotational force of the motor. It can be highly accurate.

It is an image figure which shows schematic the appearance structure of the linear actuator which concerns on embodiment of this invention. It is an image diagram which shows the state which disassembled the guide part of the conventional linear actuator roughly. It is an image diagram which shows the state which disassembled the guide part of the linear actuator which concerns on embodiment of this invention. It is an image diagram for demonstrating the guide rail of the linear actuator which concerns on embodiment of this invention. It is a schematic diagram schematically showing the structural example of the rod-shaped member which constitutes a part of the guide part 40 used for the linear actuator which concerns on embodiment of this invention. It is a figure which compared the weight of the linear actuator which concerns on embodiment of this invention, and the conventional linear actuator.

FIG. 1 is an image diagram schematically showing an external configuration of a linear actuator 100 according to an embodiment of the present invention. FIG. 2 is an image diagram schematically showing a state in which a guide portion of a conventional linear actuator is disassembled. FIG. 3 is an image diagram schematically showing a state in which the guide portion of the linear actuator 100 is disassembled. FIG. 4 is an image diagram for explaining the guide rail 42 of the linear actuator 100. FIG. 5 is a schematic diagram schematically showing a configuration example of a rod-shaped member 45 that constitutes a part of a guide portion 40 used for the linear actuator 100. The configuration of the linear actuator 100 will be described with reference to FIGS. 1 to 5.

The linear actuator 100 guides a motor 10 having a stator and a mover, a rotary shaft 20 that transmits the rotational force of the motor 10, a coupling 30 that is a joint between the motor 10 and the rotary shaft 20, and a rotary shaft 20. The guide portion 40 is included, and the stage 50 that supports the guide portion 40 is included. The coupling 30 is not an essential configuration for the linear actuator 100.

The motor 10 generates a rotational force that rotates the rotary shaft 20 when the power is turned on. The motor 10 has a casing 11 that constitutes an outer shell, and a stator and a mover are arranged in the casing 11. The stator has a coil. The mover has a magnet. By supplying electric power to the stator, the rotor is driven to rotate.

The rotary shaft 20 has a predetermined length and converts the rotational force of the motor 10 into a linear motion (linear motion). As the rotating shaft 20, for example, a feed screw or a ball screw can be used.
The coupling 30 connects the motor 10 and the rotary shaft 20. The coupling 30 is formed with one or more slits 31. The slit 31 serves to reduce variations in the rotational force transmitted to the rotating shaft 20.

The guide portion 40 has a function of suppressing rattling that occurs during the linear motion of the rotating shaft 20. The guide portion 40 has a housing 41, and ball bearings and rollers are housed inside the housing 41. If the linear motion is performed only on the rotating shaft 20, rattling occurs. Normally, a ball bearing, a roller, or the like is used to slide the rotating shaft 20 on the rail. By doing so, the friction of the rotary shaft 20 is reduced, and the rattling of the rotary shaft 20 is suppressed by utilizing the restraint of the set screw and the like. At this time, it is important that the ball bearings and rollers do not pop out from the left, right, front, back, up and down, and there is no gap. Therefore, in the linear actuator 100, a guide portion 40 is provided to solve the problem of rolling the ball bearing or the roller.

Here, the configuration of the guide unit 40 will be described with reference to FIGS. 2 and 3 in comparison with the guide unit 40A of the conventional linear actuator. The conventional linear actuator includes a guide portion 40A, and the guide portion 40A is provided with four guide rails 42A and two cross rollers 43A. That is, a plurality of pairs of guide rails 42A are provided, and a cross roller 43A is provided for each pair of guide rails 42A.

Two (pair) guide rails 42A and one cross roller 43A are configured to form a set of rotary shaft guides. The guide portion 40A is pivotally supported by two sets of rotary shaft guides so as to be rotatable and linearly movable during rotation.

Ball bearings and rollers are made of metal. Therefore, it is common to give strength to the guide portion 40A as well. That is, the guide rail 42A and the cross roller 43A are also made of metal, and the guide portion 40A is designed to have load bearing capacity. This is because if the strength of the guide portion 40A is low, the guide portion 40A is quickly worn by the rolling operation of the ball bearing or the roller, and the life is shortened.

Therefore, in general, the metal guide rail 42A and the cross roller 43A constituting the guide portion 40A are subjected to "quenching" and "tempering" operations to increase the strength of the guide rail 42A and the cross roller 43A. are doing. However, the dimensions may change before and after the "quenching" and "tempering" operations. However, although this is required for sizes that are generally used in factories, smaller ones are now replaced with general-purpose steel such as stainless steel, and the linear actuator itself and the objects to be mounted are made lighter to reduce the weight of the guide section. 40A does not need that much strength.

Based on these, in the linear actuator 100, it was decided not to install a cross roller on the guide portion 40. That is, in the linear actuator 100, a resin rod-shaped member 45 is used instead of the cross roller. Examples of the resin material constituting the rod-shaped member 45 include HDPE (high density polyethylene = ultra high molecular weight polyethylene / high molecular weight polyethylene), PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene / perfluoroalkoxyethylene copolymer resin). ), POM (polyoxymethylene), PP (polypropylene), PS (polystyrene), PVC (polyvinyl chloride) and the like can be considered. Of these, HDPE is the most suitable. Further, the shape is preferably a rectangular parallelepiped, and the size is preferably the same in terms of width and thickness, and is preferably in the range of 0.5 × 0.5 mm to 5 × 5 mm. Further, the cutting angle to the guide rail is preferably 90 degrees, which makes it possible to maintain the slipperiness while keeping the side guide rail horizontal by tightening from the side surface direction.
Even if the strength is the rod-shaped member 45, the same function as that of the cross roller can be achieved. The rod-shaped member 45 may have at least a resin surface. The rod-shaped member 45 may be entirely made of resin, or the surface of the metal / ceramic member may be coated with a resin.
Further, since the weight of the guide rail 42 can be reduced, the guide rail 42 can be manufactured of general-purpose steel such as stainless steel, and "quenching" and "tempering" are not required.

The guide rail 42 will be described with reference to FIG. FIG. 4A is an image in which the Teflon (registered trademark) seal 46 is attached to the stage 50, and FIG. 4B is an image in which the Teflon (registered trademark) seal 46 is not attached to the stage 50. Is shown.
By affixing the Teflon (registered trademark) seal 46 as an auxiliary, it is possible to minimize the left-right tilt when facing the stage traveling direction.
It should be noted that the attachment of the Teflon (registered trademark) seal 46 is an auxiliary one and does not necessarily have to be attached.
Further, Teflo (registered trademark) Nseal 46 is also an example, and may be another non-slip adhesive seal.

FIG. 3 shows an example in which a set of rotary shaft guides is composed of two guide rails 42 and one rod-shaped member 45, as in the case of the rotary shaft guide having a conventional structure. As shown in FIG. In addition, the Lini actuator 100 can be configured to be a set of rotary shaft guides with three guide rails 42. In this case, the central guide rail 42 may be made longer than the two left and right guide rails 42 to guide the rotating shaft 20. The rod-shaped member 45 is installed between the central guide rail 42 and the left and right guide rails 42, respectively. Therefore, a set of rotary shaft guides is composed of three guide rails 42 and two rod-shaped members 45. By doing so, the number of parts can be reduced as compared with the conventional linear actuator, and cost reduction and weight reduction can be realized.

FIG. 3 shows a configuration example of the rod-shaped member 45. As shown in FIG. 5 (A), the rod-shaped member 45 may be configured as a prismatic shape, or as shown in FIG. 5 (B), the rod-shaped member 45 may be configured as a cylindrical shape, and the inside may be hollow. A pipe structure (FIG. 5 (C)) may be used. However, the rod-shaped member 45 may be configured with another polygonal prism shape. Further, the rod-shaped member 45 may have a surface made of resin, and the type of resin is not particularly limited.

The stage 50 supports the guide portion 40, and also attaches the linear actuator 100 to the target object by using a screw or the like. That is, the linear actuator 100 is attached to the target object via the stage 50. The stage 50 is determined according to the length of the rotating shaft 20. Further, the width and shape of the stage 50 are not particularly limited.

Here, the linear actuator 100 will be described in detail. The linear actuator 100 has been made smaller. That is, since it is assumed that the linear actuator 100 is used for an object that does not require a large force, the linear actuator 100 does not need to be increased in size. Therefore, the weight of the linear actuator 100 becomes lighter. The weight of the linear actuator 100 can be reduced by the amount of miniaturization. FIG. 6A shows the weight of the linear actuator 100 and FIG. 6B shows the weight of the linear actuator using the cross roller guide.

Further, since the linear actuator 100 has been made smaller and lighter, the demand for durability is reduced, and a general-purpose steel such as stainless steel or a resin material can be used for the guide portion 40. Therefore, according to the linear actuator 100, the rod-shaped member 45 made of resin can be used, and it is possible to further reduce the weight. In addition, the linear actuator 100 has very little play and high accuracy by manufacturing while paying attention to the processing accuracy.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims, and the present invention can be obtained by appropriately combining the technical means disclosed in the different embodiments. The form is also included in the technical scope of the present invention. The numerical values shown are not particularly limited, and various changes can be made within the range shown in the claims.

10: Motor 11: Casing 20: Rotating shaft 30: Coupling 31: Slit 40: Guide part 40A: Guide part 41: Housing 42: Guide rail 42A: Guide rail 43A: Cross roller 45: Rod-shaped member 46: Teflon (registered) Trademark) Seal 50: Stage 100: Linear actuator

Claims (4)

With the motor
A rotating shaft that transmits the rotational force of the motor,
A guide unit that guides the rotation axis and
Including a stage that supports the guide portion,
The guide portion is
A plurality of guide rails that rotatably support the rotating shaft,
A linear actuator provided between the guide rails and having a rod-shaped member having at least a surface made of resin. With the three guide rails
The two rod-shaped members are provided,
The linear actuator according to claim 1, wherein the guide rail provided at the center of the guide rails is made longer than the left and right guide rails. The linear actuator according to claim 1 or 2, wherein the guide rail is made of general-purpose steel. The linear actuator according to any one of claims 1 to 3, wherein a coupling having a slit formed between the motor and the rotating shaft is provided.

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