JP2023046877A - Manufacturing method and manufacturing apparatus for hollow cylindrical sintered magnet - Google Patents

Abstract

To provide a manufacturing method and a manufacturing apparatus for a hollow cylindrical sintered magnet.SOLUTION: The present invention relates to a manufacturing method for a hollow cylindrical sintered magnet which has an axial length L (mm)±1 and an internal diameter D±d (mm). The manufacturing method for the hollow cylindrical sintered magnet includes: repeating the processes of preparing a sintered magnet before internal surface processing which has an internal diameter less than D-d (mm), using a rod-like grindstone for grinding to increase the internal diameter of the magnet before the internal surface processing, and measuring an internal diameter Da (mm) at a position at a distance a (mm) from one axial end part of the magnet after the internal surface processing and an internal diameter Db (mm) at a position at a distance b (mm); and changing any one or more of the position of the grindstone, the position of the magnet and a grinding time if -X≤(Db-Da)/(b-a)≤X is not satisfied. Here, X is a constant defining upper and lower limit values of a rate of variation in internal diameter to the distance from the one axial end part of the magnet after the processing, and X<2d/L is satisfied.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a manufacturing method and manufacturing apparatus for hollow cylindrical sintered magnets.

A hollow cylindrical sintered magnet (hereinafter also referred to as a “ring sintered magnet”) is basically produced by sintering a hollow cylindrical magnet compact (hereinafter also referred to as a “ring magnet compact”). obtained by Furthermore, the sintered ring magnet is processed so that the length in the axial direction (that is, the direction perpendicular to the radial direction) has a predetermined dimension, and / or as described in Patent Document 1, the axis of the sintered ring magnet It is known to machine the directional end faces to adjust the squareness.

Ring sintered magnets have come to be used in servo motors in recent years, and their demand is increasing. A servo motor is manufactured by inserting and fixing a shaft inside a sintered ring magnet. High dimensional accuracy is required for the inner diameter of the sintered ring magnet in order to insert the shaft. It is difficult to obtain the desired inner diameter by simply sintering the ring magnet compact due to dimensional changes before and after sintering. has been adjusted.

JP-A-60-123258

With the increase in demand for sintered ring magnets in recent years, the amount of processing per grindstone has increased, and as a result, the problem of errors in the inner diameter of sintered ring magnets has become apparent. In this case, the grindstone can be replaced, but the replacement of the grindstone results in an increase in cost and a decrease in productivity.

The present disclosure has been made in view of such circumstances, and one of its purposes is to provide a hollow cylindrical sintered magnet that can stably obtain a desired inner diameter and reduce the frequency of grindstone replacement. It is to provide a manufacturing method and a manufacturing apparatus.

Aspect 1 of the present invention is
A method for producing a hollow cylindrical sintered magnet having an axial length of L (mm)±l and an inner diameter of D±d (mm),
Preparing a pre-inner-surface-processed sintered magnet having a hollow cylindrical shape and an inner diameter of less than Dd (mm);
obtaining a sintered magnet after inner surface processing by grinding using a bar-shaped grindstone so as to expand the inner diameter of the sintered magnet before inner surface processing;
In the sintered magnet after inner surface processing, the inner diameter D a (mm) at the position a (mm) from one end in the axial direction and the inner diameter D _b (mm) at the position _b (mm) and
comprising repeatedly performing a group of steps comprising
If the inner-surface-machined sintered magnet after the previous group of steps does not satisfy the following formula (1), the inner-surface-machined sintered magnet after the latter group of steps satisfies the following formula (1). , in obtaining the sintered magnet after inner surface processing in the subsequent group of steps, changing any one or more of the position of the grindstone, the position of the sintered magnet before inner surface processing, and the grinding time; A method for manufacturing a hollow cylindrical sintered magnet.

-X≤( _Db - _Da )/(ba)≤X (1)

In the above formula, in the above formula (1), X is a constant that determines the upper and lower limits of the rate of change of the inner diameter with respect to the distance from one end in the axial direction of the sintered magnet after inner surface processing. It satisfies the formula (2).

X<2d/L (2)

Aspect 2 of the present invention is
The manufacturing method according to aspect 1, wherein D is 10.0 (mm) or less.

Aspect 3 of the present invention is
3. The production method according to aspect 1 or 2, wherein L/D is 2.5 or more.

Aspect 4 of the present invention is
Changing any one or more of the position of the grindstone, the position of the sintered magnet before inner surface processing, and the grinding time,
When (D _b −D _a )/(b−a) is −X ₁ or X ₁ (provided that X ₁ >X) for the sintered magnet after inner surface processing after the previous group of steps, In obtaining the inner-surface-processed sintered magnet in the subsequent group of steps, the angle between the central axis of the grindstone and the central axis of the inner-surface-processed sintered magnet is θ ₁ (where 2tan θ ₁ <X ₁ ).

Aspect 5 of the present invention is
Obtaining a sintered magnet after inner surface processing includes:
gripping the pre-inner-surface-processed sintered magnet with a first gripping portion disposed at a first position;
inserting the grindstone gripped by the second gripping portion arranged at the second position inside the sintered magnet before inner surface processing;
Rotating the sintered magnet before inner surface processing along the central axis of the first gripping portion and rotating the grindstone along the central axis of the second gripping portion;
moving the sintered magnet before inner surface processing or the grindstone in the radial direction of the sintered magnet before inner surface processing to grind the inner surface of the sintered magnet before inner surface processing with the grindstone;
stopping and holding the movement of the sintered magnet before inner surface processing or the grindstone;
stopping rotation of the sintered magnet before inner surface processing, returning the first grip portion to the first position, and returning the second grip portion to the second position;
The production method according to any one of aspects 1 to 4, comprising

Aspect 6 of the present invention is
The manufacturing method according to aspect 5, wherein changing any one or more of the position of the grindstone, the position of the sintered magnet before inner surface processing, and the grinding time includes lengthening the holding time. is.

Aspect 7 of the present invention is
In the grinding in the previous group of steps, R (mm) is the distance by which the sintered magnet before inner surface processing or the grindstone is moved in the radial direction of the sintered magnet before inner surface processing,
When the smaller of D _a and D _b of the sintered magnet after inner surface processing after the previous group of steps is D−d ₁ (mm) (provided that d ₁ >d), the latter group In the grinding of the step of (1), the distance by which the sintered magnet before inner surface processing or the grindstone is moved in the radial direction of the sintered magnet before inner surface processing is (R + d/10) (mm) or more (R + d/5) (mm) or less,
For the sintered magnet after inner surface processing after the previous group of steps, when the larger one of D _a and D _b is D + d ₁ (mm), in the grinding of the latter group of steps, Aspect 5 or 6, including setting the distance by which the sintered magnet before inner surface processing or the grindstone is moved in the radial direction to be (Rd/5) (mm) or more and (Rd/10) (mm) or less. It is a manufacturing method described in.

Aspect 8 of the present invention is
An apparatus for producing a hollow cylindrical sintered magnet having an axial length of L (mm)±l and an inner diameter of D±d (mm),
A hollow cylindrical pre-processing sintered magnet having an inner diameter of less than Dd (mm) and a rod-shaped grinding wheel are detachable, and the inner diameter of the pre-inner processing sintered magnet is expanded. A grinder configured to be able to grind using the grindstone;
In the sintered magnet after inner surface processing, which is obtained by grinding the sintered magnet before inner surface processing, the inner diameter D _a (mm) at the position where the distance from one end in the axial direction is a (mm) and the distance is b ( mm), a measuring instrument configured to be able to measure the inner diameter D _b (mm) at the position of
including
When the measurement result by the measuring device does not satisfy the following formula (1), any one or more of the position of the grindstone, the position of the sintered magnet before inner surface processing, and the grinding time can be changed. , a hollow cylindrical sintered magnet manufacturing apparatus.

-X≤( _Db - _Da )/(ba)≤X (1)

In the above formula, in the above formula (1), X is a constant that determines the upper and lower limits of the rate of change of the inner diameter with respect to the distance from one end in the axial direction of the sintered magnet after inner surface processing. It satisfies the formula (2).

X<2d/L (2)

Aspect 9 of the present invention is
The grinding machine includes a first gripping portion arranged at a first position and detachable with the sintered magnet before inner surface processing, and a second holding portion arranged at a second position and detachable with the grindstone. a gripping portion;
The first gripping portion and the second gripping portion are
operable so that the grindstone can be inserted inside the sintered magnet before inner surface processing,
The sintered magnet before inner surface processing is rotatable along the central axis of the first grip part,
The grindstone is rotatable along the central axis of the second grip,
By moving the sintered magnet before inner surface processing or the grindstone in the radial direction of the sintered magnet before inner surface processing, the inner surface of the sintered magnet before inner surface processing can be ground with the grindstone,
It is possible to stop and hold the movement of the grindstone or the sintered magnet before inner surface processing,
It is possible to stop the rotation of the sintered magnet before inner surface processing, return the first gripping portion to the first position, and return the second gripping portion to the second position,
By moving one or more of the first position and the second position, the angle between the center axis of the grindstone and the center axis of the sintered magnet before inner surface processing can be adjusted. 9. The manufacturing apparatus according to aspect 8.

According to the embodiments of the present invention, it is possible to provide a hollow cylindrical sintered magnet manufacturing method and manufacturing apparatus that can stably obtain a desired inner diameter and reduce the frequency of grindstone replacement.

FIG. 1A is a diagram schematically showing how the inner surface of the sintered ring magnet is processed in a cross section including the central axis of the sintered ring magnet and the central axis of the rod-shaped grindstone according to the embodiment of the present invention. . FIG. 1B is a diagram schematically showing how the inner surface of the sintered ring magnet is processed in a cross section including the central axis of the sintered ring magnet and the central axis of the rod-shaped grindstone according to the embodiment of the present invention. . FIG. 1C is a diagram schematically showing how the inner surface of the sintered ring magnet is processed in a cross section including the central axis of the sintered ring magnet and the central axis of the rod-shaped grindstone according to the embodiment of the present invention. . FIG. 2 is a perspective view of a sintered ring magnet according to an embodiment of the present invention. FIG. 3 is a flow chart showing an example of a method for manufacturing a sintered ring magnet according to an embodiment of the present invention. FIG. 4A is a schematic diagram explaining S2.1. FIG. 4B is a schematic diagram explaining S2.2. FIG. 4C is a schematic diagram explaining S2.3. FIG. 4D is a schematic diagram explaining S2.4. FIG. 4E is a schematic diagram explaining S2.5. FIG. 4F is a schematic diagram explaining S2.6. FIG. 5A is a schematic diagram explaining S3. FIG. 5B is a schematic diagram explaining S3. FIG. 6A is a diagram showing an example of changing the position of the grindstone and/or the sintered magnet before inner surface processing when the sintered magnet after inner surface processing after the previous group of steps does not satisfy formula (1). FIG. 6B is a diagram showing an example of changing the position of the grindstone and/or the sintered magnet before inner surface processing when the sintered magnet after inner surface processing after the previous group of steps does not satisfy formula (1).

The inventors of the present invention have been working from various angles to realize a method for manufacturing hollow cylindrical sintered magnets (ring sintered magnets) that can stably obtain a desired inner diameter and reduce the frequency of grindstone replacement. investigated.
The present inventors first studied in detail how the inner surface of a sintered ring magnet is processed, and obtained the following findings.
1A to 1C are diagrams schematically showing how the inner surface of the sintered ring magnet is processed in a cross section including the central axis of the sintered ring magnet before inner surface processing and the central axis of the rod-shaped grindstone.

As shown in FIG. 1A, the grindstone 2 gripped by the second gripping portion 22 is placed inside (hollow portion) of the ring sintered magnet 1 before inner surface processing (hereinafter also referred to as "sintered magnet 1 before inner surface processing"). After being inserted, the sintered magnet 1 before inner surface processing rotates along the central axis 1 a , and the grindstone 2 rotates along the central axis 22 a of the second grip portion 22 . Then, by moving the grindstone 2 toward the inner surface 1b in the radial direction (r direction) of the sintered magnet 1 before inner surface processing (or by moving the inner surface 1b toward the grindstone 2), the inner surface is processed. Processing of the pre-sintered magnet 1 is performed. At this time, the central axis 1a of the sintered magnet 1 before inner surface processing and the central axis 2a of the grindstone 2 can be parallel.

As shown in FIG. 1B, when the inner surface is processed, the grindstone 2 bends, the central axis 1a of the sintered magnet 1 before inner surface processing and the central axis 2a of the grindstone 2 form an angle θ, and the axis of the sintered magnet 1 before inner surface processing A difference in inner diameter can occur at a rate of change of 2 tan θ per direction (Z direction).
Here, the inner diameter D a (mm) at a position a (mm) _from one end 1c in the axial direction of the sintered magnet 1 before inner surface processing and the inner diameter D _b at a position b (mm) Then, 2tan θ is represented by the following formula (3).

2 tan θ=( _Db - _Da )/(b-a) (3)

After that, as shown in FIG. 1C, while the sintered magnet 1 before inner surface processing and the grindstone 2 are rotating, the movement of the grindstone 2 (or the sintered magnet 1 before inner surface processing) is completed for a predetermined time (for example, 30 seconds or less). As time elapses, the flexure of the grindstone 2 gradually returns to its original state, and finally θ becomes 0°, and the inner diameter difference in the axial direction of the sintered magnet 1 before inner surface processing disappears. After that, the rotation of the sintered magnet 1 before inner surface processing is stopped, and the grindstone 2 is brought out from the inside of the sintered ring magnet.

Before the study by the present inventors, only the state in which the deflection of the grindstone was eliminated as shown in FIG. 1C was confirmed. Therefore, the deflection of the grindstone 2 as shown in FIGS. The phenomenon of returning to the original state was not recognized. In addition, at the initial stage of production, the whetstone 2 returned to its original state after a predetermined period of time, so no particular problem occurred.

However, as a result of studies by the present inventors, when the amount of processing of one grindstone 2 increases, unlike the initial stage of manufacture, the deflection of the grindstone 2 becomes difficult to return to its original state only after a predetermined period of time (i.e., FIG. 1B It becomes easy to maintain the state of the grindstone 2 shown in )). This is true when the diameter of the grindstone 2 is reduced as the diameter of the sintered ring magnet is reduced, and when the aspect ratio (ratio of axial length/inner diameter) of the sintered ring magnet increases. It was also found that it occurs remarkably when the ratio (ratio of length in the axial direction/diameter) is increased.

Further, as a result of investigation by the present inventors, when the desired inner diameter cannot be obtained when the processing amount of one grindstone 2 increases, the main cause is the generally recognized grindstone 2 It was found that the above-mentioned flexing is difficult to return to its original state, rather than the decrease in sharpness. That is, due to the increase in the rate of change of the inner diameter in the axial direction of the sintered ring magnet, the sharpness of the grindstone 2 is reduced, and the frequency of falling below the desired inner diameter is reduced. More often than not, the inner diameter at either end in the axial direction was above or below the desired range.
Therefore, the error in the rate of change of the inner diameter represented by the above formula (3) is obtained from the length L (mm) and the maximum inner diameter difference 2d (mm) as shown in the above formulas (1) and (2). It was checked whether it is within ±X, which is smaller than ±(2d/L). As a result, the problem of deflection can be detected at an early stage, and one or more of the position of the grindstone 2, the position of the sintered magnet 1 before inner surface processing, and the grinding time can be changed, and the axis of the sintered ring magnet can be changed. An increase in the inner diameter error due to an increase in the rate of change of the inner diameter in the direction can be suppressed at an early stage without replacing the grindstone.
As described above, a method for producing a sintered ring magnet has been realized, in which a desired inner diameter can be stably obtained and the frequency of replacement of the grindstone can be reduced.

Details of each requirement defined by the embodiments of the present invention are shown below.

First, the dimensions of the hollow cylindrical sintered magnet 10 (hereinafter also referred to as "ring sintered magnet 10") according to the embodiment of the present invention will be described. FIG. 2 is a perspective view of the sintered ring magnet 10. FIG. As shown in FIG. 2, the sintered ring magnet 10 is manufactured to have a length of L±l in the axial direction (Z direction). Note that the axial direction is a direction perpendicular to the radial direction (r direction). L is not particularly limited, but can be about 5 to 30 mm. The permissible error l is not particularly limited, but may be 0.1 mm, for example. In addition, the allowable error l may adopt a value standardized in the product, preferably a value smaller than the standardized value (e.g., 50% or less than the standardized value) may be

The sintered ring magnet 10 is manufactured to have an inner diameter of D±d. The inventors of the present invention have found that when D is 10.0 mm or less, the problem that the deflection of the grindstone becomes difficult to recover may occur in a relatively early stage of production. That is, when D is 10.0 mm or less, it is necessary to make the diameter of the grindstone less than 10.0 mm (more specifically, less than (10.0-d) mm). Since it becomes difficult to return at an early stage, the effect of being able to suppress an increase in the inner diameter error according to the embodiment of the present invention at an early stage becomes remarkable. When D is 6.0 mm or less, the problem that the deflection of the grindstone becomes difficult to return may occur in an earlier stage of production, and in that case, the effect of the embodiment of the present invention becomes more pronounced.
Although the allowable error d is not particularly limited, it may be 0.1 mm, for example. Also, the allowable error d can be a value smaller than the tolerance for the final dimensions of the product (for example, 50% or less of the tolerance for the final dimensions).

The present inventors discovered that when the aspect ratio L/D of the length L and the inner diameter D of the sintered ring magnet 10 is 2.5 or more, the problem that the flexure of the grindstone 2 is difficult to return is relatively early in the manufacturing process. We have found that it can occur in stages. That is, when L/D is 2.5 or more, it is necessary to make the aspect ratio of the length and diameter of the grindstone 2 exceed 2.5, in which case the deflection of the grindstone 2 returns at a relatively early stage of production. Therefore, the effect of being able to suppress an increase in inner diameter error in an early stage according to the embodiment of the present invention becomes remarkable. When L/D is 4.0 or more, the problem that the flexure of the grindstone 2 is difficult to return may occur in an earlier stage of production, and in that case, the effect of the embodiment of the present invention becomes more pronounced.

The difference between the outer diameter and the inner diameter of the sintered ring magnet 10 is not particularly limited, but can be 1.0 to 10.0 mm.

FIG. 3 is a flow chart showing an example of a method for manufacturing the hollow cylindrical sintered magnet 10 according to the embodiment of the present invention. Steps S1 to S6 will be described in detail below.

(S1) Preparing the sintered magnet 1 before inner surface processing In S1, a hollow cylindrical sintered magnet 1 with an inner diameter less than Dd (mm) is prepared. The pre-inner-surface-processed sintered magnet 1 can be produced by pulverizing a magnet raw material, compressing the powder into a hollow cylindrical shape, and sintering it. Two types of magnet raw materials are widely used in various fields: rare earth/iron/boron magnets and rare earth/cobalt magnets. Among them, rare earth/iron/boron magnets (hereinafter referred to as “R—Fe—B magnets”. R is at least one element selected from the group consisting of rare earth elements and yttrium, Fe is iron, and B is boron. ) has the highest magnetic energy product among various magnets and is relatively inexpensive, so it is actively used in various parts. Part of Fe may be replaced with a transition metal element such as Co. Further, up to half of boron may be substituted with carbon.

The inner diameter of the sintered magnet 1 before inner surface processing (hereinafter sometimes referred to as “D _i ”) must be less than (D−d) mm in consideration of grinding the inner surface later, and is preferably (D−d−0.2) mm or less. However, if it is too small, processing takes a long time, so _Di is preferably (D−d−0.6) mm or more. Dimensions other than the inner diameter of the sintered magnet 1 before inner surface processing are preferably adjusted to the final dimensions shown in FIG. Preferably, it should be easily adjustable to final dimensions.

(S2) Grinding using a rod-shaped grindstone to obtain a sintered magnet after inner surface processing In S2 (not shown), a rod-shaped grindstone 2 is used to expand the inner diameter of the sintered magnet 1 before inner surface processing. The sintered ring magnet after inner surface processing (hereinafter also referred to as “sintered magnet 11 after inner surface processing”) is obtained.

An example of the bar-shaped grindstone 2 is an electrodeposited diamond grindstone. The electrodeposited diamond grindstone is formed by fixing abrasive grains such as synthetic diamond to the surface of a cylindrical metal (for example, SK material) by nickel electroplating or the like. The diameter of the grindstone 2 (hereinafter sometimes referred to as “D _w ”) must be smaller than the inner diameter D _i of the sintered magnet before inner surface processing, and is preferably (D _i ×0.9) mm or less. is. However, in order for the grindstone 2 to easily return to its flexure, _Dw is preferably as large as (D _i ×0.7) mm or more.

S2 may specifically include:
(S2.1) gripping the sintered magnet 1 before inner surface processing by the first gripping part;
(S2.2) inserting the grindstone 2 inside the sintered magnet 1 before inner surface processing;
(S2.3) rotating the sintered magnet 1 before inner surface processing and the grindstone 2;
(S2.4) Grinding by moving the sintered magnet 1 before inner surface processing or the grindstone 2;
(S2.5) stopping and holding the movement of the sintered magnet 1 before inner surface processing or the grindstone 2; and (S2.6) stopping the rotation of the sintered magnet 1 before inner surface processing and the grindstone 2.
An example of S2.1 to S2.6 will be described below with reference to FIGS. 4A to 4F. 4A-4F also show an example of a grinder 20 according to an embodiment of the present invention. For example, as shown in FIG. 4A, the grinder 20 has a first gripper 21 arranged at a predetermined position (first position) and a predetermined position (second position) different from the first position. and a second grip portion 22 . A general-purpose lathe chuck can be used for the first gripper 21 and the second gripper 22 . As shown in FIG. 4A, the central axis 21a of the first grip may be collinear with the central axis 22a of the second grip 22, but is not limited to this.

(S2.1) Grasping the sintered magnet 1 before inner surface processing by the first gripping portion In S2.1, the sintered magnet 1 before inner surface processing is gripped by the first gripping portion 21 arranged at the first position. Grasp. As shown in FIG. 4A , the sintered magnet 1 before inner surface processing is moved in the direction of the solid arrow and inserted into the first gripping portion 21 , and the sintered magnet 1 before inner surface processing is moved by the first gripping portion 21 . Grasp. At this time, the central axis 1 a (not shown) of the sintered magnet 1 before inner surface processing can be on the same straight line as the central axis 21 a of the first grip portion 21 . It should be noted that the sintered magnet 1 before inner surface processing may be moved using a conveying section (not shown).

(S2.2) Inserting the grindstone 2 inside the sintered magnet 1 before inner surface processing It is inserted inside (hollow part) of the sintered magnet 1 . As shown in FIG. 4B, the second gripper 22 is moved in the direction of the solid arrow to insert the grindstone 2 into the sintered magnet 1 before inner surface processing. 4B, the second gripping portion 22 is moved. It may be inserted into the pre-processed sintered magnet 1 . In order to grind efficiently, the first gripping portion 21 and/or the second gripping portion 22 are moved, and the grindstone 2 is baked before inner surface processing so that the grindstone 2 penetrates the sintered magnet 1 before inner surface processing. It is preferably inserted inside the magnet 1 .

(S2.3) Rotating the sintered magnet 1 before inner surface processing and the grindstone 2 In S2.3, the sintered magnet 1 before inner surface processing is rotated along the central axis 21a of the first grip portion 21, and The grindstone 2 is rotated along the central axis 22 a of the second grip portion 22 . As shown in FIG. 4C, as for the direction of rotation, the grindstone 2 and the sintered magnet 1 before inner surface processing may be rotated in opposite directions as viewed from the Z direction, as indicated by broken line arrows, or may be rotated in the same direction. good too. The rotation speed of the grindstone 2 (second grip portion 22) is preferably faster than the rotation speed of the pre-inner-surface-processing sintered magnet 1 (first grip portion 21). ) can be 70,000 to 80,000 rpm, and the rotational speed of the sintered magnet 1 (first grip part 21) before inner surface processing can be 1,200 to 1,800 rpm.

(S2.4) Grinding by moving the sintered magnet 1 before inner surface processing or the grindstone 2 In S2.4, the sintered magnet 1 before inner surface processing or the grindstone 2 is moved in the radial direction of the sintered magnet 1 before inner surface processing. Then, the inner surface of the sintered magnet 1 before inner surface processing is ground by the grindstone 2 . As shown in FIG. 4D, for example, the grindstone 2 and the second gripper 22 are moved in the direction of the solid arrow. Although the second gripping portion 22 is moved in FIG. 4D, the first gripping portion 21 (or the first gripping portion 21 and the second gripping portion 22) may be moved. In order to improve accuracy, it is preferable to move either one of the second gripping portion 22 and the first gripping portion 21 .
If the grinding time required for S2.4 (hereinafter also referred to as "first grinding time") is short, the productivity improves, but on the other hand, the grindstone 2 tends to bend. Therefore, the first grinding time is preferably 10 to 60 seconds. The moving speed can be, for example, 0.01 to 2 mm/min. Grinding may be performed while supplying a general-purpose grinding fluid. Further, grinding may be performed while the grindstone 2 is cooled.

(S2.5) Stopping and Holding the Sintered Magnet 1 Before Inner Surface Processing or the Grindstone 2 In S2.5, the movement of the sintered magnet 1 before inner surface processing or the grindstone 2 is stopped and held. As shown in FIG. 4E, since the grindstone 2 and the pre-inner-surface-processing sintered magnet 1 continue to rotate while being held, the inner-surface grinding of the pre-inner-surface-processing sintered magnet 1 proceeds. The time required for S2.5 (hereinafter also referred to as the “second grinding time”) is also the time for the grinding wheel 2 to return to its original state as shown in FIGS. 1B to 1C, and from the viewpoint of productivity 30 seconds or less is preferable. However, if the second grinding time is too short, the deflection of the grindstone 2 may not be sufficiently restored in many cases, so it is preferable to set it to 5 seconds or longer.

(S2.6) Stopping the rotation of the sintered magnet 1 before inner surface processing In S2.6, the rotation of the sintered magnet 1 before inner surface processing is stopped, and the first grip portion 21 is returned to the original first position. The second grip 22 is returned to its original second position. After that, by removing the sintered magnet 11 after inner surface processing from the first gripping portion 21 , the next sintered magnet 1 before inner surface processing can be gripped by the first gripping portion 21 . As shown in FIG. 4F, for example, the sintered magnet 11 after inner surface processing is taken out from the first gripping portion 21 in the direction of the solid line arrow. It should be noted that the sintered magnet 11 after inner surface processing may be taken out using a conveying section (not shown).

(S3) Measure the inner diameter of the sintered magnet after inner surface processing. In S3, the inner diameter D _a (mm) and The inner diameter D _b (mm) is measured at the position where the distance is b (mm). An example of S3 will be described below with reference to FIGS. 5A and 5B. 5A-5B also show an example of a measuring instrument 30 according to an embodiment of the present invention. For example, as shown in FIG. 5A, the measuring instrument 30 has a third gripper 31 arranged at a predetermined position (third position) and a predetermined position (fourth position) different from the third position. and an inner diameter measuring device 32 . A general-purpose chuck can be used for the third gripper 31 . The inner diameter measuring device 32 may have a sensor portion 32b, and when the sensor portion 32b is inserted into the inside (hollow portion) of the sintered magnet 11 after inner surface processing, the sensor 32b is displaced inside the inner diameter measuring device 32, The inner diameter can be measured from the amount of displacement. As the general-purpose inner diameter measuring device 32, a BMD plug gauge (manufactured by Diatest Japan Co., Ltd.) or the like is used.
First, as shown in FIG. 5A , the sintered magnet 11 after inner surface processing is moved in the direction of the solid line arrow and inserted into the third gripping portion 31 , and the sintered magnet 11 after inner surface processing is moved by the third gripping portion 31 . grasp the At this time, the central axis (not shown) of the sintered magnet 11 after inner surface processing can be on the same straight line as the central axis 31 a of the third grip portion 31 . It should be noted that the sintered magnet 11 after inner surface processing may be moved using a conveying section (not shown).
Next, as shown in FIG. 5B, the inner diameter measuring device 32 is moved and inserted into the sintered magnet 11 after inner surface processing. At this time, the central axis 32a of the inner diameter measuring device 32 can be aligned with the central axis of the sintered magnet 11 after inner surface processing. Although the inner diameter measuring device 32 is moved in FIG. 5B, the third gripping portion 31 (or the third gripping portion 31 and the inner diameter measuring device 32) may be moved. Then, the sensor part 32 of the inner diameter measuring device 32 is arranged at a position where the distance from one end 11c in the axial direction of the sintered magnet 11 after inner surface processing is a (mm) and b (mm), and _the inner diameter Da (mm) and inner diameter D _b (mm). After the measurement, the inner diameter measuring device 32 (and/or the third gripper 31) is returned to its original position. After that, by removing the sintered magnet 11 after inner surface processing from the third gripping portion 31 , the next sintered magnet 11 after inner surface processing can be gripped by the third gripping portion 31 . It should be noted that the sintered magnet 11 after inner surface processing may be taken out using a conveying section (not shown).
In order to make it easier to detect the difference in the inner diameter of the sintered magnet 11 after inner surface processing, it is preferable that these two measurement positions are separated. more preferred. Since chips and the like from inner surface processing may adhere to the sintered magnet 11 after inner surface processing and cause measurement errors, it is preferable to remove chips and the like by air blowing before measurement.

(S4) Check if the measurement result satisfies the formula (1) In S4, the measurement result in S3 is the length L (mm) and the maximum inner diameter difference Confirm whether it is within ±X, which is smaller than ±(2d/L) obtained from 2d (mm).

-X≤( _Db - _Da )/(ba)≤X (1)

In the above formula (1), X is a constant that determines the upper and lower limits of the rate of change of the inner diameter of the sintered magnet 11 after inner surface processing with respect to the distance from one end in the axial direction, and is expressed by the following formula (2): meet.

X<2d/L (2)

X is preferably d/L or less, so that an increase in inner diameter error due to an increase in the change rate of the inner diameter of the sintered magnet 11 in the axial direction after inner surface processing can be suppressed more quickly. However, if X is set to a too small value, the position of the grinding wheel 2 and/or the sintered magnet 1 before inner surface processing, which will be described later, will be repeated many times, and in some cases productivity may decrease. /5L or more is preferable.
In addition, when the above formula (1) is not satisfied continuously for a plurality of times, the grindstone 2 may be replaced before processing the next sintered magnet 1 before inner surface processing.

(S5) Determine whether to change the grinding time. In S5, if the above formula (1) is not satisfied in S4, when processing the next sintered magnet 1 before inner surface processing, in S2.4 Decide whether to lengthen the first grind time and/or the second grind time of S2.5. When lengthening the first grinding time and/or the second grinding time, for example, it may be 1.5 times, 2.0 times, or 3.0 times, respectively. Preferably, only the second grinding time is 1.5 times, 2.0 times, 3.0 times, or the like. However, from the viewpoint of productivity, it is preferable to change the position of the grindstone 2 and/or the sintered magnet 1 before inner surface processing in S6, which will be described later, rather than changing the grinding time. In FIG. 3, for convenience of explanation, if No in S5 (that is, if the grinding time is not changed), the process proceeds to S6. Even if there is, it may proceed to S6.

(S6) Determine whether to change the position of the sintered magnet 1 before inner surface processing and/or the grindstone 2. In S6, if the above formula (1) is not satisfied in S4, the sintered magnet 1 before inner surface processing and/or Determine whether to change the position of the grindstone 2.

6A and 6B show changes in the position of the grindstone 2 and/or the sintered magnet 1 before inner surface processing when the sintered magnet 11 after inner surface processing after the previous group of steps does not satisfy the above formula (1). FIG. 4 is a diagram showing an example;
6A and 6B, the inclination of the grindstone 2 indicates the inclination in which the grindstone 2 is in contact with the magnet 1 before inner surface processing during processing.
As shown in FIG. 6A, when the rate of change 2 tan θ of the inner diameter of the inner surface-processed sintered magnet 11 after the previous group of steps is −X ₁ or X ₁ (where X ₁ >X), the grindstone 2 can be inclined at an angle θ with respect to the central axis 1a of the sintered magnet 1 before inner surface processing. In addition, although the central axis 2a of the grindstone 2 in FIG. 6A schematically shows the case of being linear, it may be curved. Even in the case of a curved shape, the curvature does not become so large, so, for example, tan θ may be calculated using the above equation (3) in the same way as in the case of a linear shape.
From the state of FIG. 6A, as shown in FIG. 6B, the grindstone 2 and/or the sintered magnet before inner surface processing is changed so that the central axis 2a of the grindstone 2 and the central axis 1a of the sintered magnet 1 before inner surface processing are parallel. Change the position of the magnet 1 (for example, rotate the grindstone 2 (second gripper 22) in the direction of the solid arrow as shown in FIG. 6B). As a result, changes in the inner diameter in the axial direction are eliminated in the sintered magnet 11 after inner surface processing in the subsequent group of steps. Considering the case where the angle in FIG. 6A is θ or less due to a measurement error or the like, in a group of later steps, the central axis 2a of the grinding wheel 2 and the central axis 1a of the sintered magnet 1 after inner surface processing The position of the grindstone 2 and/or the sintered magnet 1 before inner surface processing may be changed so that the angle θ ₁ (where θ ₁ ≤ θ (that is, 2 tan _{θ 1} ≤ X ₁ )). Furthermore, when the inner diameter is managed in a narrow _range with an allowable error d of _0.1 mm, considering that the influence of measurement errors etc. and/or it is preferable to relatively incline the sintered magnet 1 before inner surface processing. However, if θ ₁ is too small, the position will _be changed many times, which may reduce productivity in some cases _.

A step (S7) (not shown) of checking whether Da _and /or _Db of the sintered magnet 11 after inner surface processing after the previous group of steps is outside the range of D±d is included after S4, for example. You can stay. If it is outside the range of D±d in S7, for example, before processing the next sintered magnet 1 before inner surface processing, the grindstone 2 or the sintered magnet 1 before inner surface processing in S2.4 is moved. A step (S8) (not shown) of determining whether to change the distance may be included. By including S7 and S8, it is possible to stably obtain a desired inner diameter even when, for example, the sharpness of the grindstone 2 is deteriorated.

An example of a method for changing the distance for moving the sintered magnet 1 before inner surface processing or the grindstone 2 in S2.4 will be described. Assume that the distance by which the sintered magnet 1 before inner surface processing or the grindstone 2 is moved in the radial direction of the sintered magnet 1 before inner surface processing is R (mm) in S2.4 of the previous group of steps. . At this time, when the smaller of D _a and D _b of the sintered magnet 11 after inner surface processing after the previous group of steps is D−d ₁ (mm) (where d ₁ >d), In S2.4 of the subsequent group of steps, the distance by which the sintered magnet before inner surface processing 1 or the grindstone 2 is moved in the radial direction of the sintered magnet before inner surface processing 1 can be made larger than R. When the inner diameter is managed within a narrow range of allowable error d of 0.1 mm, the distance to move the sintered magnet 1 before inner surface processing in the radial direction is set in consideration of the greater influence of measurement errors and the like. It is preferable to increase the distance little by little to R+d/5 (mm) or less. However, if the amount of change in the distance (d/5 (mm)) is too small, the movement distance of the sintered magnet 1 before inner surface processing or the grindstone 2 will be changed many times, and in some cases productivity will decrease. Therefore, it is preferable to set the moving distance to R+d/10 (mm) or more.
Further, for _the inner surface-machined sintered magnet 11 after the previous group of steps, when the larger of Da and _Db is D+d ₁ (mm), in S2.4 of the latter group of steps , the distance by which the sintered magnet 1 before inner surface processing or the grindstone 2 is moved in the radial direction of the sintered magnet 1 before inner surface processing can be made smaller than R. When the inner diameter is managed within a narrow range of allowable error d of 0.1 mm, the distance to move the sintered magnet 1 before inner surface processing in the radial direction is set in consideration of the greater influence of measurement errors and the like. It is preferable to reduce the distance little by little with Rd/5 (mm) or more. However, if the amount of change in the distance (d/5 (mm)) is too small, the movement distance of the sintered magnet 1 before inner surface processing or the grindstone 2 will be changed many times, and in some cases productivity will decrease. Therefore, it is preferable to set the moving distance to Rd/10 (mm) or less.

In S7, if either D _a or D _a is outside the range of D±d for a plurality of consecutive times, the grindstone 2 may be replaced.

An apparatus for manufacturing a hollow cylindrical sintered magnet 10 according to an embodiment of the present invention includes:
An apparatus for manufacturing a hollow cylindrical sintered magnet 10 having an axial length of L (mm)±l and an inner diameter of D±d (mm),
A hollow cylindrical pre-processing sintered magnet 1 having an inner diameter of less than Dd (mm) and a rod-shaped grindstone 2 are detachable, and the inner diameter of the pre-inner processing sintered magnet 1 is expanded. A grinder 20 configured to be able to grind using the grindstone 2 so as to
An inner diameter D a (mm) at a position a (mm) from one _end 11c in the axial direction of the sintered magnet 11 after inner surface processing, which is obtained by grinding the sintered magnet 1 before inner surface processing, and the distance a measuring instrument 30 configured to be able to measure the inner diameter D _b (mm) at the position where is b (mm);
including
Any one or more of the position of the grindstone 2, the position of the sintered magnet 1 before inner surface processing, and the grinding time can be changed when the measurement result by the measuring device 30 does not satisfy the above formula (1). It is

The grinding machine 20 includes a first gripping portion 21 arranged at a first position and detachable with the sintered magnet 1 before inner surface processing, and a second holding portion 21 arranged at a second position and detachable with the grindstone 2. and a gripping portion 22 of . Furthermore, the first gripping portion 21 and the second gripping portion 22 may be configured to be able to perform S2.1 to S2.6, and furthermore, the first position and the second position are changed. , the angle formed by the central axis 2a of the grindstone 2 and the central axis 1a of the sintered magnet 1 before inner surface processing may be adjustable.
As the grinding machine 20, a general-purpose internal grinding machine or the like can be used, for example, STG-3N (manufactured by Seiko Instruments) or the like can be used. In addition, it may include a conveying section that conveys the inner-surface-processed sintered magnet 1 into the first gripping section 21 and enables the inner-surface-processing sintered magnet 1 to be taken out from the first gripping section 21 . .

The measuring device 30 may include an inner diameter measuring device 32 capable of measuring inner diameters at a plurality of locations of the sintered magnet 11 after inner surface processing. A BMD plug gauge (manufactured by Diatest Japan Co., Ltd.) or the like is used as the inner diameter measuring device 32 . Further, a transfer unit may be included that transfers the inner surface-machined sintered magnet 11 from the grinder 20 to the inner diameter measuring device 32 and arranges it so that the inner diameter can be measured. In addition, a nozzle capable of air blowing the sintered magnet 11 after inner surface processing may be included before inner diameter measurement.

The manufacturing apparatus is configured to be able to change one or more of the position of the grindstone 2, the position of the sintered magnet 1 before inner surface processing, and the grinding time based on the inner diameter measurement result of the measuring device 30. Further, the manufacturing apparatus may include a control unit (not shown) capable of controlling the driving of the grinding machine 20 and the measuring machine 30 so as to automatically perform S2 to S8. The control unit is a known computer, and may include an arithmetic device, a storage device, and an input/output device. In order to drive the grinding machine 20 and the measuring machine 30 in various ways, a plurality of driving units (not shown) such as motors may be provided, and the plurality of driving units may be controllable by the control unit. The various drives include driving the conveying unit for moving the sintered magnet 1 after inner surface processing in S2.1, driving the second gripping portion 22 (and/or the first gripping portion 21) in S2.2, Rotational driving of the first gripping part 21 and the second gripping part 22 in S2.3, driving of the second gripping part 22 and/or the first gripping part 21 in S2.4, and firing after the inner surface processing in S2.6. Driving the conveying unit for moving the magnet 1, driving the conveying unit for moving the sintered magnet 11 after inner surface processing in S3, driving the inner diameter measuring device 32 and/or the third gripping unit 31, and moving the grindstone 2 in S6. Driving the first gripping portion 21 and/or the second gripping portion 22 for changing the angle between the central axis 2a and the central axis 1a of the sintered magnet 1 after inner surface processing, etc. can be mentioned.

An example of the operation of the control section of the manufacturing apparatus will be described. First, the grinding conditions preset in the storage device are read. Next, the grinding machine 20 is driven according to the grinding conditions to perform S2 (S2.1 to S2.6). After that, the measuring machine 30 is driven to perform S3. The inner diameters D _a and D _b measured by the measuring machine are stored in the storage device. The measurement results (inner diameters D _a and D _b ) of S3 are read out from the storage device, and S4 is performed using the arithmetic device. In S4, when the above formula (1) is satisfied, the grinding conditions are not changed in S5 and S6, and when the above formula (1) is not satisfied, the grinding conditions are changed in S5 and/or S6, New grinding conditions to be used from now on are stored in the storage device. If necessary, after S3, S7 may be performed using an arithmetic unit, and if Da _and /or _Db are outside the range of D±d, the grinding conditions are changed in S8, and the next A new grinding condition to be used from may be stored in the storage device. In S5, S6 and S8, the user of the apparatus can decide whether or not to change the grinding conditions in consideration of productivity and the like. may be set. In addition, the manufacturing apparatus replaces the grindstone 2 when the above formula (1) is not satisfied continuously a plurality of times (and when Da _and /or _Db are outside the range of D±d). It may be configured as

In addition to the above, those skilled in the art can implement various modifications to the above embodiments without departing from the scope of the present disclosure, and the present disclosure also includes such modifications. be.

1 sintered magnet before inner surface processing 1a central axis of sintered magnet before inner surface processing 1b inner surface of sintered magnet before inner surface processing 1c one axial end of sintered magnet before inner surface processing 2 rod-shaped grindstone 2a rod-shaped grindstone Central axis 10 Ring sintered magnet 11 Sintered magnet after inner surface processing 11c One axial end of sintered magnet after inner surface processing 20 Grinding machine 21 First grip portion 21a Central axis of first grip portion 22 Second gripping portion 22a central axis of second gripping portion 30 measuring instrument 31 third gripping portion 31a central axis of third gripping portion 32 inner diameter measuring device 32a central axis of inner diameter measuring device 32b sensor portion

Claims (9)

A method for producing a hollow cylindrical sintered magnet having an axial length of L (mm)±l and an inner diameter of D±d (mm),
Preparing a pre-inner-surface-processed sintered magnet having a hollow cylindrical shape and an inner diameter of less than Dd (mm);
obtaining a sintered magnet after inner surface processing by grinding using a bar-shaped grindstone so as to expand the inner diameter of the sintered magnet before inner surface processing;
In the sintered magnet after inner surface processing, the inner diameter D a (mm) at the position a (mm) from one end in the axial direction and the inner diameter D _b (mm) at the position _b (mm) and
comprising repeatedly performing a group of steps comprising
If the inner-surface-machined sintered magnet after the previous group of steps does not satisfy the following formula (1), the inner-surface-machined sintered magnet after the latter group of steps satisfies the following formula (1). , in obtaining the sintered magnet after inner surface processing in the subsequent group of steps, changing any one or more of the position of the grindstone, the position of the sintered magnet before inner surface processing, and the grinding time; A method for producing a hollow cylindrical sintered magnet.

-X≤( _Db - _Da )/(ba)≤X (1)

In the above formula (1), X is a constant that determines the upper and lower limits of the rate of change of the inner diameter of the sintered magnet after inner surface processing with respect to the distance from one end in the axial direction, and is expressed by the following formula (2): meet.

X<2d/L (2)
The manufacturing method according to claim 1, wherein D is 10.0 (mm) or less. The production method according to claim 1 or 2, wherein L/D is 2.5 or more. Changing any one or more of the position of the grindstone, the position of the sintered magnet before inner surface processing, and the grinding time,
When (D _b −D _a )/(b−a) is −X ₁ or X ₁ (provided that X ₁ >X) for the sintered magnet after inner surface processing after the previous group of steps, In obtaining the inner-surface-processed sintered magnet in the subsequent group of steps, the angle between the central axis of the grindstone and the central axis of the inner-surface-processed sintered magnet is θ ₁ (where 2tan θ ₁ <X ₁ ), the manufacturing method according to any one of claims 1 to 3. Obtaining a sintered magnet after inner surface processing includes:
gripping the pre-inner-surface-processed sintered magnet with a first gripping portion disposed at a first position;
inserting the grindstone gripped by the second gripping portion arranged at the second position inside the sintered magnet before inner surface processing;
Rotating the sintered magnet before inner surface processing along the central axis of the first gripping portion and rotating the grindstone along the central axis of the second gripping portion;
moving the sintered magnet before inner surface processing or the grindstone in the radial direction of the sintered magnet before inner surface processing to grind the inner surface of the sintered magnet before inner surface processing with the grindstone;
stopping and holding the movement of the sintered magnet before inner surface processing or the grindstone;
stopping rotation of the sintered magnet before inner surface processing, returning the first grip portion to the first position, and returning the second grip portion to the second position;
The manufacturing method according to any one of claims 1 to 4, comprising 6. The manufacture according to claim 5, wherein changing any one or more of the position of the grindstone, the position of the sintered magnet before inner surface processing, and the grinding time includes increasing the holding time. Method. In the grinding in the previous group of steps, R (mm) is the distance by which the sintered magnet before inner surface processing or the grindstone is moved in the radial direction of the sintered magnet before inner surface processing,
When the smaller of D _a and D _b of the sintered magnet after inner surface processing after the previous group of steps is D−d ₁ (mm) (provided that d ₁ >d), the latter group In the grinding of the step of (1), the distance by which the sintered magnet before inner surface processing or the grindstone is moved in the radial direction of the sintered magnet before inner surface processing is (R + d/10) (mm) or more (R + d/5) (mm) or less,
For the sintered magnet after inner surface processing after the previous group of steps, when the larger one of D _a and D _b is D + d ₁ (mm), in the grinding of the latter group of steps, 5 or 6. The manufacturing method according to 6. An apparatus for producing a hollow cylindrical sintered magnet having an axial length of L (mm)±l and an inner diameter of D±d (mm),
A hollow cylindrical pre-processing sintered magnet having an inner diameter of less than Dd (mm) and a rod-shaped grinding wheel are detachable, and the inner diameter of the pre-inner processing sintered magnet is expanded. A grinder configured to be able to grind using the grindstone;
In the sintered magnet after inner surface processing, which is obtained by grinding the sintered magnet before inner surface processing, the inner diameter D _a (mm) at the position where the distance from one end in the axial direction is a (mm) and the distance is b ( mm), a measuring instrument configured to be able to measure the inner diameter D _b (mm) at the position of
including
When the measurement result by the measuring device does not satisfy the following formula (1), any one or more of the position of the grindstone, the position of the sintered magnet before inner surface processing, and the grinding time can be changed. , production equipment for hollow cylindrical sintered magnets.

-X≤( _Db - _Da )/(ba)≤X (1)

In the above formula (1), X is a constant that determines the upper and lower limits of the rate of change of the inner diameter of the sintered magnet after inner surface processing with respect to the distance from one end in the axial direction, and is expressed by the following formula (2): meet.

X<2d/L (2)
The grinding machine includes a first gripping portion arranged at a first position and detachable with the sintered magnet before inner surface processing, and a second holding portion arranged at a second position and detachable with the grindstone. a gripping portion;
The first gripping portion and the second gripping portion are
operable so that the grindstone can be inserted inside the sintered magnet before inner surface processing,
The sintered magnet before inner surface processing is rotatable along the central axis of the first grip part,
The grindstone is rotatable along the central axis of the second grip,
By moving the sintered magnet before inner surface processing or the grindstone in the radial direction of the sintered magnet before inner surface processing, the inner surface of the sintered magnet before inner surface processing can be ground with the grindstone,
It is possible to stop and hold the movement of the grindstone or the sintered magnet before inner surface processing,
It is possible to stop the rotation of the sintered magnet before inner surface processing, return the first gripping portion to the first position, and return the second gripping portion to the second position,
By moving one or more of the first position and the second position, the angle between the center axis of the grindstone and the center axis of the sintered magnet before inner surface processing can be adjusted. 9. The manufacturing apparatus according to claim 8, wherein

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