JP2016008669A - Sintered oil impregnation bearing and linear actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict occurrence of irregular noise or variations in vibration frequency of a movable element at the time of driving a linear actuator.SOLUTION: A linear actuator 1 of this invention comprises a fixed shaft 20 and a movable element 30 moved along the fixed shaft 20. The movable element 30 includes a main body part 31 having a permanent magnet and bearings 32 arranged at each of the ends of the main body part 31 in an axial direction. An insertion hole h2 into which the fixed shaft 20 is inserted and passed is formed in each of the bearings 32. Then, at each of the bearings 32, an inner diameter of a bearing (x) having a bearing surface (b) is formed within a range from 0.4 mm or more and 0.8 mm or less, and a chamfer part (y) continuous with the bearing (x) is formed in at least one of both ends in an axial direction of the insertion hole h2.

Description

  The present invention relates to a sintered oil-impregnated bearing and a linear actuator provided with the sintered oil-impregnated bearing. It relates to an actuator.

In general, a mobile information terminal such as a smartphone, a tablet, or a mobile phone is provided with a vibration actuator capable of generating vibration, and when receiving an incoming call, the vibration actuator is driven to generate vibration. A function for notifying incoming calls and the like is provided.
Conventionally, as a vibration actuator disposed in a portable information terminal, one that rotates an eccentric weight disposed on a rotating shaft of a DC motor (see Patent Document 1), and one that rotates a fan-shaped movable element (Patent Document 2) For example, a device that linearly reciprocates the mover by electromagnetic force (so-called “linear actuator”) is known.
In particular, in recent years, with the downsizing and thinning of portable information terminals, there has been a demand for downsizing and thinning of vibration actuators. As a vibration actuator that can be easily reduced in size and thickness, development of a linear actuator (so-called “horizontal linear actuator”) in which a mover is reciprocated in parallel with respect to the installation surface of the vibration actuator is proceeding (Patent Literature). 3).
The horizontal linear actuator according to Patent Document 3 includes a fixed shaft fixed in a frame and a driver that moves along the fixed shaft. A coil is disposed on the inner peripheral surface of the frame. The driver has a cylindrical permanent magnet and a bearing disposed at each end of the permanent magnet shaft method. The driving element is supported by the fixed shaft by inserting the fixed shaft through the pair of bearings.
And in the linear actuator which concerns on patent document 3, a driver element is reciprocated (vibrated) along a fixed axis | shaft by controlling the electric current sent through a coil.

JP-A-7-107699 JP-A-6-205565 JP 2003-117488 A

However, in the conventional horizontal linear actuator, abnormal noise may occur during driving, and the frequency of the driver (mover) may vary.
That is, in the conventional horizontal linear actuator, there is a possibility that minute burrs (protrusions generated when processing the material) are formed in the openings of the bearings arranged at the respective ends of the permanent magnet in the axial direction. . When the burr is formed in the opening of the bearing, the burr formed in the bearing contacts the fixed shaft during driving, so that abnormal noise is generated and the frequency of the mover varies.
The subject of this invention is suppressing generation | occurrence | production of the abnormal noise at the time of the drive of a linear actuator, and the dispersion | variation in the frequency of a needle | mover.

In order to solve the above-mentioned problem, a sintered oil-impregnated bearing according to a first aspect of the present invention is a sintered oil-impregnated bearing disposed in a linear actuator having a mover moved along a fixed shaft, wherein the mover An inner diameter of a bearing portion in which the bearing surface facing the fixed shaft is formed is 0.4 mm or more and 0.8 mm. A chamfered portion that is formed within the following range and that is continuous with the bearing portion is formed in at least one of both end portions in the axial direction of the insertion hole.
In the sintered oil-impregnated bearing according to the first invention, the inner diameter of the bearing portion on which the bearing surface is formed is formed within the range of 0.4 mm or more and 0.8 mm or less. And the chamfering part which follows a bearing part is formed in at least one among the both ends of an insertion hole.
As a result, in the sintered oil-impregnated bearing according to the first aspect of the invention, even when a minute burr is formed at the end (opening) of the insertion hole, the burr is prevented from contacting the fixed shaft. be able to.
Therefore, according to the sintered bearing according to the first aspect, it is possible to suppress the generation of abnormal noise and the variation in the frequency of the mover when the linear actuator is driven.

The sintered oil-impregnated bearing according to the second invention is the sintered oil-impregnated bearing according to the first invention, wherein the chamfered portion is formed by pressing.
In the sintered oil-impregnated bearing according to the second invention, the chamfered portion can be easily configured.
In particular, by forming the chamfered portion by pressing after the insertion hole is formed in the sintered oil-impregnated bearing, it is possible to remove the minute burrs generated when the insertion hole is formed by pressing.

The sintered oil-impregnated bearing according to the third invention is the sintered oil-impregnated bearing according to the first or second invention, wherein the inner peripheral surface of the chamfered portion is an R surface.
In the sintered oil-impregnated bearing according to the third aspect of the invention, by setting the inner peripheral surface of the chamfered portion continuous to the bearing portion to be an R surface, a corner is not formed at the boundary between the bearing portion and the chamfered portion. It is possible to improve the smoothness of movement of the mover relative to the shaft.

The sintered oil-impregnated bearing according to the fourth invention is the sintered oil-impregnated bearing according to the first or second invention, wherein the inner peripheral surface of the chamfered portion is a tapered surface, and the tapered surface is inclined with respect to the bearing surface. The angle is formed within a range of 1 ° or more and 4 ° or less.
In the sintered oil-impregnated bearing according to the fourth invention, the chamfered portion can be easily formed as compared with the case where the inner peripheral surface of the chamfered portion is the R surface.
Here, in a sintered oil-impregnated bearing having an inner diameter of the bearing portion of 0.4 mm or more and 0.8 mm or less, if the inclination angle of the tapered surface with respect to the bearing surface is less than 1 °, the insertion hole There is a possibility that minute burrs formed at the end (opening) may come into contact with the fixed shaft.
On the other hand, if the inclination angle of the tapered surface with respect to the bearing surface exceeds 4 °, the sintered oil-impregnated bearing may be broken.
Therefore, by forming the inclination angle of the tapered surface with respect to the bearing surface within a range of 1 ° or more and 4 ° or less, the generation of abnormal noise during the driving of the linear actuator and the frequency of the mover are prevented while preventing cracking. It is possible to suppress the variation of.

The linear actuator which concerns on 5th invention is equipped with the sintered oil impregnation bearing which concerns on any one invention among 1st thru | or 4th, It is characterized by the above-mentioned.
With the linear actuator according to the fifth aspect of the invention, it is possible to suppress the generation of abnormal noise during driving and the variation in the frequency of the mover.

  According to the present invention, it is possible to suppress the generation of abnormal noise and the variation in the frequency of the mover when the linear actuator is driven.

It is sectional drawing which shows schematic structure of the linear actuator 1 which concerns on embodiment of this invention. It is sectional drawing of the bearing which concerns on a 1st example. It is sectional drawing of the bearing which concerns on a 2nd example. It is a figure which shows the relationship between the kind of antioxidant added to base oil, and the loss rate of lubricating oil. It is a figure which shows the relationship between the kind of extreme pressure agent and oiliness agent added to base oil, and the lubricity of lubricating oil. It is a figure which shows the chamfering processing method which concerns on a prior art. It is a figure which shows the 1st process of the chamfering processing method which concerns on this embodiment. It is a figure which shows the 2nd process of the chamfering processing method which concerns on this embodiment.

Hereinafter, a linear actuator 1 according to an embodiment of the present invention will be described with reference to the drawings.
The linear actuator 1 is arranged in a portable information terminal such as a smartphone, a tablet, or a mobile phone, and is an actuator of a type that generates a vibration when driven when receiving an incoming call (so-called “vibration actuator”).
The linear actuator 1 is a linear actuator (so-called “horizontal linear actuator”) in which a movable element 30 described later is moved in parallel with the installation surface of the linear actuator 1.
(Configuration of linear actuator 1)
FIG. 1 is a cross-sectional view showing a schematic configuration of a linear actuator 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the bearing according to the first example. FIG. 3 is a cross-sectional view of a bearing according to a second example. FIG. 4 is a diagram showing the relationship between the type of antioxidant added to the base oil and the loss rate of the lubricating oil. FIG. 5 is a diagram showing the relationship between the types of extreme pressure agents / oil agents added to the base oil and the lubricity of the lubricating oil.
A linear actuator 1 shown in FIG. 1 includes a housing 10, a fixed shaft 20 fixed inside the housing 10, a mover 30 supported by the fixed shaft 20, and a pair of members that urge the mover 30. A spring 40 and a coil portion 50 disposed inside the housing 10 are provided.
The housing 10 is formed in a cylindrical shape or a rectangular tube shape. The housing 10 is made of a metal such as iron. In the present embodiment, the dimension (internal dimension) of the casing 10 (in the left-right direction shown in FIG. 1) is formed within a range of 8 mm to 15 mm. The height of the housing 10 is 5 mm or less.
The fixed shaft 20 is formed in a cylindrical shape. The fixed shaft 20 is made of SUS420J2, SUS303, ceramic, cobalt alloy, cemented carbide or the like. The fixed shaft 20 is disposed between both side walls in the axial direction of the housing 10. Each end of the fixed shaft 20 is held by each side wall in the axial direction of the housing 10. In the present embodiment, the outer diameter of the fixed shaft 20 is formed within a range of 0.4 mm to 0.8 mm.

The mover 30 has a main body portion 31 in which permanent magnets (not shown) are disposed, and bearings 32 disposed at respective end portions in the axial direction of the main body portion 31.
The main body 31 has an insertion hole h1 through which the fixed shaft 20 is inserted, and is formed in a substantially cylindrical shape. The main body 31 is provided with a permanent magnet formed in a cylindrical shape. The permanent magnet is magnetized with the same polarity in the radial direction. Specifically, the inner peripheral surface of the permanent magnet is magnetized to one of the S and N poles, and the outer peripheral surface is magnetized to the other of the S and N poles.
Here, in the main body 31, a plurality of permanent magnets may be arranged along the axial direction. In such a configuration, different poles are magnetized on the outer peripheral surface side of two adjacent permanent magnets. The main body 31 may be provided with a weight.
The weight provided in the main body 31 is formed of a metal such as tungsten or copper, and is particularly preferably formed of pure copper.

Each bearing 32 is a sintered oil-impregnated bearing. Each bearing 32 has an insertion hole h2 (see FIGS. 2 and 3) through which the fixed shaft 20 is inserted, and is formed in a substantially cylindrical shape. The inner diameter of the insertion hole h2 is smaller than the inner diameter of the insertion hole h1 of the main body 31 (permanent magnet).
As shown in FIG.2 and FIG.3, each bearing 32 has the chamfering part y formed in each edge part of an axial direction, and the bearing part x formed between the double-sided chamfering part y. .
Here, in each bearing 32, the chamfered portion y is set to one of the axial end portions of each bearing 32 (for example, the end portion on the opposite side of the main body portion 31 of the axial end portions of each bearing 32). You may form only.
The inner peripheral surface of the bearing portion x is a bearing surface b that comes into contact (sliding contact) with the outer peripheral surface of the fixed shaft 20. In the present embodiment, the inner diameter of the bearing portion x is formed within a range of 0.4 mm to 0.8 mm.
Each chamfered portion y is formed by press working (chamfering processing, chamfering processing) as will be described later. The inner peripheral surface of each chamfered portion y is continuous with the bearing surface b of the bearing portion x. The inner diameter of each chamfered portion y gradually increases from the inner side (the bearing portion x side) toward the outer side (the opposite side to the bearing portion x).
In the present embodiment, as shown in FIG. 2, the inner peripheral surface of each chamfered portion y is an R surface. The curvature of each chamfered portion y (R surface) is preferably formed within a range of R0.03 mm to R0.7 mm.
Moreover, as shown in FIG. 3, the inner peripheral surface of each chamfered portion y may be a tapered surface. At this time, when the inner diameter of the bearing portion x is formed within a range of 0.4 mm to 0.8 mm or less, the inclination angle a of the tapered surface (the inner peripheral surface of each chamfered portion y) with respect to the bearing surface b is 1. If it is less than 0 °, a minute burr formed at the end (opening) of the insertion hole h2 may come into contact with the fixed shaft 20. On the other hand, if the inclination angle a exceeds 4 °, the bearing 32 may break when forming a tapered surface or during driving. Therefore, the inclination angle a is preferably formed within a range of 1 ° to 4 °.

In the portable information terminal, strength that can withstand an impact at the time of dropping is required. For this reason, generally, at the time of manufacturing a portable information terminal, a predetermined drop test (for example, a test for dropping the portable information terminal from a height of 180 cm is performed 100 times to verify the strength) is performed. Along with this, each bearing 32 also needs to be strong enough to withstand the predetermined drop test.
On the other hand, the linear actuator 1 is formed with a smaller size than a general linear actuator in order to be disposed in a portable information terminal. Along with this, each bearing 32 also needs to be formed with a smaller size than a general sintered oil-impregnated bearing, and the bearing volume is reduced. In general, in a sintered oil-impregnated bearing, the strength decreases as the bearing volume decreases.
Therefore, in each bearing 32, the strength is ensured by increasing the density and decreasing the oil content as compared with a general sintered oil-impregnated bearing. Specifically, in each bearing 32, the density is formed in the range of 6.6 g / cm to 7.4 g / cm, and the oil content is formed in the range of 8 vol% to 15 vol%. . Thereby, in each bearing 32, generation | occurrence | production by the shortage of lubricating oil is suppressed, ensuring required intensity | strength. Note that the oil content of a general sintered oil-impregnated bearing is 18 vol% or more.

  Moreover, in each bearing 32, when the axial dimension of the bearing portion x is less than 0.2 mm, the strength is insufficient, and there is a risk of deformation due to the predetermined drop test. Therefore, in each bearing 32, it is preferable that the axial dimension of the bearing portion x is 0.2 mm or more. Accordingly, in each bearing portion x, it is preferable to form the chamfered portion y within a range of 0.03 mm to 0.2 mm.

In addition, the linear actuator requires durability and reliability that can withstand repeated use. For this reason, in general, when a linear actuator is manufactured, a predetermined durability test (for example, the operation for 2 seconds is repeated 1,000,000 times to verify the durability) is performed.
In general, the linear actuator is attached to the portable information terminal by a soldering process in a reflow furnace at a high temperature. For this reason, when the soldering process is performed, the lubricating oil impregnated in the sintered oil-impregnated bearing may be lost (evaporated), and if the lubricating oil is lost, the durability and reliability of the linear actuator deteriorates.
Therefore, in each bearing 32, the loss (evaporation) of the lubricant is suppressed by including an antioxidant in the impregnated lubricating oil, and the durability and reliability of the linear actuator 1 are improved.
Specifically, the lubricating oil impregnated in each bearing 32 is composed of a base oil and an additive. As the base oil, it is preferable to use a poly α-olefin base oil. And an antioxidant is included as an additive.
As the antioxidant, one containing at least one of phenol, amine, Zn-DTP (zinc dialkyldithiophosphate), and sulfur can be used.
As shown in FIG. 4, the loss rate of the lubricating oil can be reduced by using an amine-based, Zn-DTP, or sulfur-based antioxidant, and in particular, an aromatic amine-based one is used. And the effect which reduces the loss rate of lubricating oil becomes high.

Moreover, in the linear actuator 1, since the fixed shaft 20 does not rotate with respect to each bearing 32, an oil film is not formed between the outer peripheral surface of the fixed shaft 20 and the bearing surface b of each bearing 32. Improvement in lubrication properties (wear resistance and low friction) due to formation cannot be expected.
Therefore, in each bearing 32, the lubricating characteristics are improved by including an extreme pressure agent / oil-based agent in the impregnated lubricating oil.
Specifically, an extreme pressure agent / oil agent is included as the additive. As an extreme pressure agent / oil-based agent, at least among Mo-DTP (molybdenum dialkyldithiophosphate), Zn-DTP (zinc dialkyldithiophosphate), chlorinated paraffin, sulfurized fat, aliphatic phosphate ester, and aromatic phosphate ester One including one can be used.
In particular, as shown in FIG. 5, by using an aliphatic phosphate ester as the extreme pressure agent / oil agent, the friction coefficient can be reduced, and the wear amount can be reduced.

  Each bearing 32 is disposed on each end face of the main body 31 in the axial direction. The central axis of the insertion hole h1 of the main body 31 and the central axis of the insertion hole h1 of each bearing 32 are arranged on a straight line. And the needle | mover 30 is arrange | positioned in the state by which the fixed axis | shaft 20 was penetrated by the continuous penetration hole h1 and the penetration hole h2. Thereby, the mover 30 is supported by the fixed shaft 20 so as to be movable along the fixed shaft 20. In the mover 30, the bearing surface b of each bearing 20 is in contact (sliding contact) with the outer peripheral surface of the fixed shaft 20, and other portions are not in contact with the fixed shaft 20.

Each spring 40 is a compression coil spring. Each spring 40 is disposed between the inner surface of each side wall in the axial direction of the housing 10 and the outer end surface of each bearing 32. The spring 40 disposed on the one side wall biases the mover 30 toward the other side wall. As a result, in a state where no current flows through the coil 50, the mover 30 is disposed at a substantially central portion in the axial direction in the housing 10.
The coil unit 50 (stator) is disposed on the inner peripheral surface of the housing 10. The coil unit 50 is formed of a plurality of coils. The plurality of coils are arranged along the axial direction of the housing 10. Each coil includes a winding wound along the inner peripheral surface of the housing 10. In the two adjacent coils, the winding directions are opposite to each other, and currents in opposite directions flow in the circumferential direction.

The linear actuator 1 is installed on a predetermined installation surface of the portable information terminal. At this time, the fixed shaft 20 is installed in parallel to the installation surface. Thereby, the moving direction of the mover 30 is parallel to the installation surface.
The linear actuator 1 is driven by passing a current through each coil of the coil unit 50. Specifically, the mover 30 can be reciprocated (vibrated) along the fixed shaft 20 by switching the direction of the current flowing through each coil at a predetermined cycle. In the present embodiment, when the linear actuator 1 is driven, the mover 30 is set to vibrate at a predetermined frequency within the range of 100 Hz to 200 Hz.

(Manufacturing method of each bearing 32)
Next, a method for manufacturing each bearing 32 will be described.
FIG. 6 is a diagram showing a chamfering method according to the prior art. FIG. 7 is a diagram showing a first step of the chamfering method according to the present embodiment. FIG. 8 is a diagram showing a second step of the chamfering method according to the present embodiment.
In the manufacture of the bearing 32, first, a mold lubricant is added to the metal powder as a raw material, and the mixture is stirred and mixed. Here, as the metal powder, copper powder, bronze powder, brass powder, white powder, iron powder, copper nickel alloy powder, copper-coated iron powder, stainless steel powder, tin powder, graphite powder, a mixed powder thereof or the like should be used. Can do.
As the mold lubricant, a metal soap powder represented by zinc stearate, lithium stearate, etc., a fatty acid amide powder such as ethylene bis stearamide, or a wax lubricant powder such as polyethylene is used. be able to.
Note that the metal powder, solid lubricant component, and mold lubricant as raw materials are not limited to these.

Next, the mixed raw material powder is press-molded in a mold at a pressure of about 100 to 500 MPa to form a green compact.
In the present embodiment, at the time of forming the green compact, a C surface is formed at each corner c between the end surface in the axial direction of the green compact (bearing 32) and the inner peripheral surface of the insertion hole h2 (C chamfering). ). Specifically, the C surface is formed at each corner c by pressing the raw material powder in a mold.
Further, the green compact is sintered under a predetermined atmosphere and a predetermined temperature condition to form a sintered body. By sintering the green compact, adjacent metal particles are diffusion-bonded and the metal particles are bonded to form a porous sintered body.
The predetermined atmosphere includes a vacuum, a reducing gas (ammonia decomposition gas, hydrogen gas, endothermic gas, etc.), an inert gas (nitrogen gas, argon gas, etc.), and a mixture of these reducing gas and inert gas. The gas is selected as appropriate depending on the raw material composition.
The predetermined temperature related to the sintering is practically about 600 to 1200 ° C., for example, in the case of bronze (Cu—Sn), about 600 to 800 ° C., and the material mainly composed of iron is about 700 to 1200 ° C. Also, this is appropriately selected depending on the raw material composition.
Further, the sintered body is sized (recompressed) in a mold to form a compression molded body (hereinafter referred to as “sintered body”). By sizing the sintered body, the dimensional accuracy can be improved and the surface roughness can also be improved.

And chamfering part y is formed in a sintered compact.
The chamfered portion y is formed by pressing (chamfering or chamfering). Specifically, the chamfered portion y includes a processing pin p (see FIGS. 6 to 8), and a corner portion c (of each end surface in the axial direction of the sintered body (bearing 32) and the inner peripheral surface of the insertion hole h2 ( The corner c is formed by being compressed and deformed by pressing against the corner c) where the C-plane is formed.
Here, as shown in FIG. 6, in the conventional chamfering method, when the machining pin p is pressed against the corner portion c, the outer diameter direction of the sintered body is caused by the stress generated in the sintered body. Deformation or axial compression occurred, which could break the sintered body. In FIG. 6, the stress generated in the sintered body is indicated by a broken line arrow.
Therefore, in the chamfering method according to the present embodiment, the use of the press working apparatus 100 shown in FIGS. 7 and 8 suppresses the sintered body from cracking.
Specifically, the press processing apparatus 100 includes a base 110, a mold 130 attached to the base 110 via a compression coil spring 120, and a processing pin p that can be moved in the vertical direction. ing.
The mold 130 is made of metal. The mold 130 is formed with a mounting portion on which the sintered body (bearing 32) can be mounted. The inner diameter of the mounting portion substantially matches the outer diameter (target outer diameter) of the sintered body (bearing 32).
A transfer surface corresponding to the surface (R surface or taper surface) formed at the corner portion c is formed at the tip of the processing pin p.

In the chamfering method according to the present embodiment, first, one corner c of both corners c of the sintered body (bearing 32) (the corner c existing at one end of both axial ends). ) Is chamfered.
That is, as shown in FIG. 7, the sintered body is placed on the mounting portion of the mold 130 with one end face of the both end faces of the shaft method facing upward. Then, the processing pin p is lowered, and the tip of the processing pin p is pressed against the sintered body placed on the placement portion of the mold 130 with a predetermined strength.
At this time, since the outer peripheral surface of the sintered body is supported by the mold 130, deformation of the sintered body in the outer diameter direction is prevented. In addition, the compression coil spring 120 absorbs the downward component of the stress generated in the sintered body, so that the axial compression of the sintered body is suppressed. This suppresses cracking of the sintered body.
Then, after the chamfering process for one of the corner parts c of the sintered body is finished, the other corner part c (the corner part c existing at the other end part of both end parts in the axial direction) is chamfered. Apply.
That is, as shown in FIG. 8, the sintered body is placed on the mounting portion of the mold 130 with the other end face of the both end faces of the shaft method facing upward, and the processing pin p is lowered. The tip of the processing pin p is pressed against the sintered body placed on the placement portion of the mold 130 with a predetermined strength.
Thus, the chamfered portion y is formed in the sintered body (bearing 32).
In the present embodiment, the chamfered portion y is formed on the sintered body (compression molded body) after sizing (recompression). However, the chamfered portion y may be formed on the sintered body before sizing.

Then, the sintered body (the sintered body after sizing) on which the chamfered portion y is formed is subjected to a cleaning process to remove metal scraps generated by various processes, sizing lubricant, and the like.
Then, the bearing 32 is completed by impregnating the cleaned sintered body with lubricating oil. Here, the impregnation of the lubricating oil into the sintered body is performed by a method of impregnating the lubricating oil in a vacuum oil immersion pot (vacuum oil immersion).

(Operation and effect of each bearing 32 and linear actuator 1)
In each bearing 32, the inner diameter of the bearing portion x where the bearing surface b is formed is formed within a range of 0.4 mm or more and 0.8 mm or less. And the chamfering part y which follows the bearing part x is formed in at least one among the both ends of the insertion hole h2.
As a result, in each bearing 32, even if a minute burr is formed at the end (opening) of the insertion hole h <b> 2, it is possible to suppress the burr from contacting the fixed shaft 20.
Therefore, in the linear actuator 1, it is possible to suppress the generation of abnormal noise during driving and the variation in the vibration frequency of the mover 30.
Further, in the linear actuator 1, the chamfered portion y is formed by press working.
This makes it possible to easily configure the chamfered portion y.
In particular, in the linear actuator 1, the chamfered portion y is formed by press working after the insertion hole h2 is formed in the sintered body.
As a result, it is possible to remove minute burrs generated during the formation of the insertion hole h2 by pressing.
Further, in each bearing 32, the inner peripheral surface of the chamfered portion y continuous with the bearing portion x is an R surface, so that no corner is formed at the boundary between the bearing portion x and the chamfered portion y. Thus, the smoothness of the movement of the mover 30 relative to 20 can be improved.
On the other hand, in each bearing 32, when the inner peripheral surface of the chamfered portion y continuous with the bearing portion x is a tapered surface, the inclination angle of the tapered surface with respect to the bearing surface b is within a range of 1 ° to 4 °. Thus, it is possible to suppress the generation of abnormal noise and the variation in the frequency of the mover while driving the linear actuator while preventing cracking.

DESCRIPTION OF SYMBOLS 1 Linear actuator 10 Housing | casing 20 Fixed shaft 30 Movable element 31 Main body part 32 Bearing h1 Insertion hole h2 Insertion hole x Bearing part y Double-sided part 40 Spring 50 Coil part 100 Press processing apparatus 110 Base 120 Compression coil spring 130 Mold p Processing pin

Claims (5)

A sintered oil impregnated bearing disposed in a linear actuator having a mover moved along a fixed axis,
Disposed in the mover,
Having an insertion hole through which the fixed shaft is inserted;
The inner diameter of the bearing portion in which the bearing surface facing the fixed shaft is formed in the insertion hole is formed within a range of 0.4 mm or more and 0.8 mm or less,
A sintered oil-impregnated bearing, wherein a chamfered portion continuous to the bearing portion is formed in at least one of both end portions in the axial direction of the insertion hole.   The sintered oil-impregnated bearing according to claim 1, wherein the chamfered portion is formed by press working.   The sintered oil-impregnated bearing according to claim 1 or 2, wherein an inner peripheral surface of the chamfered portion is an R surface. The inner peripheral surface of the chamfered portion is a tapered surface,
3. The sintered oil-impregnated bearing according to claim 1, wherein an inclination angle of the tapered surface with respect to the bearing surface is formed within a range of 1 ° or more and 4 ° or less. A linear actuator comprising the sintered oil-impregnated bearing according to any one of claims 1 to 4.

Images