JPS6249507B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a casing, and more particularly to a casing formed from a light metal material by die casting.

For example, in various devices such as automatic door devices, a variable speed gear mechanism is used as a mechanism to change the rotational output of an appropriate drive source such as an electric motor to an appropriate speed and transmit it to a driven part. . This speed change gear mechanism generally includes a plurality of various gears and a gear box serving as a casing that rotatably supports a shaft to which these gears are fixed and that surrounds the gears. The shaft is supported on the gear box by forming a mounting portion having a circular inner circumferential surface on the inner wall of the gear box, and mounting a bearing member having a circular outer circumferential surface on the shaft, and attaching the bearing member to the gear box. This is accomplished by mounting on the mounting section.

Recently, it has been proposed and put into practical use that a casing such as the gear box is formed from a light metal material such as aluminum or an aluminum-based alloy by die casting. However, in the casing as described above, it is important to mold the mounting portion with considerable precision, so conventionally, after die-casting, the mounting portion was further subjected to so-called precision machining.

In this regard, referring to FIG. 1, the inner surfaces of the opposing side walls 2a and 2b of the casing have circular inner circumferential surfaces 4a and 4b, respectively, at corresponding positions. Mounting parts 6a and 6b are formed. On the other hand, at both ends of the shaft 10 to which the gear 8 is fixed, shown by the two-dot chain line,
Bearing member 1 having circular outer peripheral surfaces 12a and 12b
4a and 14b are attached, and these bearing members 14a and 14b are attached to the mounting portion 6a, respectively.
and 6b. In such a configuration, first of all, the distance L 1 between the end surfaces of the two mounting portions 6a and 6b and the distance L ₂ between the outer surfaces of the bearing members 14a and 14b located on both sides of the shaft 10 are as _follows . It is important that they be substantially equal. When L ₁ is larger than L ₂ and the value of L ₁ −L ₂ becomes excessive, the following disadvantages occur. For example, if the gear 8 is a worm gear that engages with another gear (not shown), when the rotation of the gear 8 is reversed, the direction of the thrust load acting on the shaft 10 is reversed; is moved in the direction shown by the arrow 16 or 18, and the bearing member 14a or 14b is moved to the mounting portion 6a.
and collides with the end face of 6b, which causes noise, vibration, etc. On the other hand, if L ₁ is smaller than L ₂ , the bearing members 14a and 14b are originally attached to the mounting portion 6.
However, if the bearing members 14a and 14b are forcibly attached to the mounting parts 6a and 6b using the elastic displacement of the side walls 2a and 2b, the mounting parts 6a and 6b can be forcibly mounted. A large thrust load is applied to the bearing members 14a and 14b from 6b, and as is easily understood, the bearing members 14a and 14b rotatably support the shaft 10.
function will be damaged. Second, the mounting part 6a
and the inner diameter D ₁ of the inner peripheral surfaces 4a and 4b of the bearing members 14a and 14b, and the outer peripheral surfaces 12a and 12 of the bearing members 14a and 14b.
It is important that the outer diameter D ₂ of b is substantially equal. If D ₁ is excessively smaller than D ₂ , the bearing members 14a and 14b cannot be fitted into the mounting portions 6a and 6b, as a matter of course. On the other hand, D ₁ is D ₂
If it is larger than this, so-called looseness will occur when the bearing members 14a and 14b are mounted to the mounting portions 6a and 6b.

By the way, as is well known to those skilled in the art, according to the die-casting method, the end surfaces of the mounting parts 6a and 6b can be formed with sufficient precision, and therefore the mounting parts 6
The distance L ₁ between the end faces of bearing members 14a and 6b can be formed with sufficient precision to be substantially equal to the distance L ₂ between the outer faces of bearing members 14a and 14b. However, the inner peripheral surfaces 4a and 4b of the mounting parts 6a and 6b
As shown in FIG. 2, which shows an enlarged view of the mounting portion 6b, the inner circumferential surfaces 4a and 4b inevitably have a slight slope due to the draft angle of the mold used for die casting. The inner diameter D ₁ of the bearing members 14a and 14b is determined with sufficient accuracy, and therefore the overall inner diameter D 1 of the inner circumferential surfaces 4a and 4b is determined with sufficient accuracy.
It is impossible to mold it substantially equal to the outer diameter D ₂ of 2b.

Therefore, conventionally, after die-casting the casing, the inner circumferential surfaces 4 of the mounting portions 6a and 6b are
Precision machining was performed on parts a and 4b. However, if precision machining is performed in addition to die casting, the manufacturing cost of the casing will naturally increase considerably. In addition, precision machining itself has errors due to positioning errors and processing errors when attaching the workpiece to the machine tool.
Therefore, even if precision machining is performed, the inner peripheral surfaces 4a and 4
There is some so-called variation in the inner diameter _D1 of b due to machining errors, and there is some variation in the meshing between the gear 8 fixed to the shaft 10 and other gears (not shown). will occur.

On the other hand, the inner peripheral surfaces 4a and 4 of the mounting parts 6a and 6b
The minimum inner diameter D ₁ ^- min of bearing members 14a and 14
b, and the maximum outer diameter D ₁ ^- max of the inner peripheral surfaces 4a and 4b of the mounting parts 6a and 6b is smaller than the outer diameter D ₂ of the outer peripheral surfaces 12a and 12b of the bearing members 14a and 1.
The mounting portion 6a is set larger than the outer diameter D ₂ of the outer circumferential surfaces 12a and 12b of the mounting portion 6a as shown by the two-dot chain line in FIG. and 6
Attempts have also been made to fit the bearing members 14a and 14b into the bearing members 14a and 14b by press fitting. However, in this case, when the bearing members 14a and 14b are press-fitted, a part of the inner peripheral surfaces 4a and 4b of the mounting parts 6a and 6b are scraped off by the corners of the bearing members 14a and 14b, and this The metal debris thus generated will damage the end surfaces of the mounting portions 6a and 6b and the bearing members 14a and 14.
The bearing member 14a remains on the end surface of the mounting portions 6a and 6b due to such metal debris.
and 14b cannot be brought into contact with each other as required, resulting in incomplete attachment to the attachment parts 6a and 6b. Also,
The metal debris is removed by some method, and the attached part 6a is
Even if the outer surfaces of the bearing members 14a and 14b can be forcibly brought into contact with the end surfaces of the mounting portions 6a and 6b as required, the inner peripheral surfaces 4 of the mounting portions 6a and 6b
As can be easily understood from FIG. 2, there is a considerable distance between a and 4b and the outer peripheral surfaces 12a and 12b of the bearing members 14a and 14b, and the radius of the bearing members 14a and 14b is This results in insufficient directional support.

Therefore, as a measure to solve the above-mentioned problem when press-fitting a bearing member into the mounting part in the die-cast state, we developed the U.S. Pat.
Publication No. 80653 discloses that an opening that matches the circular inner circumferential surface of the mounting part is also formed in the wall where the mounting part is formed,
The so-called draft angle between the opening and the circular inner circumferential surface of the mounting part is made so that the inner diameter gradually decreases from the outer wall surface toward the tip of the mounting part, contrary to the usual case, and further, the cylindrical wall of the mounting part is A configuration is disclosed in which radial through grooves are formed at intervals in the circumferential direction. In such a configuration, the bearing member is press-fitted into the mounting portion from the outer wall side, and at this time, the cylindrical wall portion of the mounting portion is elastically bent radially outward due to the presence of the groove. In this way, the bearing member is elastically held in the mounting portion. Therefore, the above-mentioned problem, namely, that when the bearing member is press-fitted into the mounting part, the inner circumferential surface of the mounting part is scraped off and metal debris is generated, which causes various problems, can be solved. Avoided.

However, the configuration disclosed in the above-mentioned Japanese Utility Model Publication No. 50-80653 is still not completely satisfactory and has the following problems.

First, a draft angle is created on the inner circumferential surface of the mounting portion, in which the inner diameter gradually decreases from the outer wall surface toward the tip of the mounting portion. Therefore, when the bearing member is press-fitted into the mounting part from the outer wall side, the inner circumferential surface of the mounting part will come into close contact with the outer circumferential surface of the bearing member at the distal end, which has a small inner diameter, but at the proximal end, which has a large inner diameter. At this point, a slight gap is created between the inner circumferential surface of the mounting section and the outer circumferential surface of the bearing member. Therefore, the bearing member is not supported by the mounting portion throughout its axial direction;
Only its tip is supported. Therefore, the holding of the bearing member is unstable, the central axis of the bearing member does not coincide with the central axis of the mounting part and is tilted, and also the bearing member and the shaft are subjected to considerable damage while the shaft is rotated. Vibrations may be generated.

Second, since the bearing member is press-fitted into the mounting part using the elastic deflection of the mounting part, the contact pressure between the inner peripheral surface of the mounting part and the outer peripheral surface of the bearing member is determined by the elastic deflection of the mounting part. Therefore, it cannot be made to a sufficiently large value, and from this point of view as well, the holding of the bearing member becomes unstable and insufficient.

Thirdly, in order to form the grooves at intervals in the circumferential direction in the cylindrical wall portion of the mounting portion, it is necessary to form the grooves at intervals in the circumferential direction in either the male die or the female die of the die-casting mold. It is necessary to form a plurality of thin flap pieces. Such thin flap pieces have low strength and are highly likely to break in a short period of time.

The present invention has been made in view of the above facts, and its main purpose is to provide a casing formed from a light metal material by die-casting, without performing precision machining on the mounting part after die-casting. Therefore, the bearing member can be press-fitted into the mounting portion in the die-cast state without causing any problems, and the press-fitted bearing member can be held sufficiently stably and firmly. The objective is to provide a new and superior casing that can

The solution of the present invention to achieve this object is as follows: (1) disposing a plurality of support protrusions extending in the axial direction at intervals in the circumferential direction on the circular inner circumferential surface of the mounting part; (2) It is necessary to provide a draft angle for die cutting in each of the support protrusions, but such draft angles are made to exist on both sides in the circumferential direction, and no draft angle is made to exist on the inner surface in the radial direction of the support protrusion. Therefore, although the circumferential width of each of the support projections varies when viewed in the axial direction, the diameter of the circle defined by the radial inner surface of each of the support projections does not vary when viewed in the axial direction. It's about forcing someone to do something.

That is, according to the present invention, the casing is formed from a light metal material by die-casting, and the inner wall surface of the casing is formed with a mounting portion having a circular inner circumferential surface, so that the shaft can be freely rotated. In a casing in which a bearing member having a circular outer circumferential surface for supporting is press-fitted into the mounting surface; Support protrusions are formed, draft angles of each of the support protrusions are generated on both sides in the circumferential direction, and the width of each of the support protrusions in the circumferential direction gradually increases from the receiving end to the bottom end of the mounting portion. A casing is provided, characterized in that, although increasing, the diameter of the circle defined by the radial inner surface of each of the support projections does not vary in the axial direction.

In the casing of the present invention, when the bearing member is press-fitted into the mounting portion, each of the support protrusions is compressed and deformed in the radial direction (more specifically, from the cross-sectional shape shown by the two-dot chain line in FIG. 6 to the shape shown by the solid line). The bearing member is compressed and deformed) and is mounted on the mounting portion.

Since there is no draft on the radial inner surface of each of the support protrusions, the compressive deformation of each of the support protrusions in the longitudinal direction is sufficiently uniformly performed over the entire length in the axial direction. Therefore, each of the support protrusions supports the bearing member sufficiently uniformly over the entire length in the axial direction, and the bearing member is stably held. On the other hand, in accordance with the general technical knowledge regarding draft angles in die-casting methods, if the draft angle necessary for mold removal of each support projection is made to exist on the radial inner surface of each support protrusion rather than on its circumferential side surface, The following problem occurs. That is, if the draft angle of each support protrusion is made to exist on its radial inner surface,
The diameter of the circle defined by the radially inner surface of each of the support projections will gradually decrease from the receiving end to the bottom end of the mounting portion. Therefore, the amount of radial compressive deformation of the support projection when the bearing member is press-fitted into the mounting portion gradually increases from the receiving end toward the bottom end. In such a case, each of the support projections supports the bearing member sufficiently firmly at the bottom end, but provides little support at the receiving end. In other words, the support of the bearing member by each of the support protrusions is not uniform over the entire length in the axial direction, but is concentrated only at the bottom end. Therefore, the holding of the bearing member is
The structure becomes unstable as in the case of the structure disclosed in Publication No. 80653.

In addition, since the bearing member is press-fitted into the mounting part using compressive deformation of the support protrusion, the contact pressure between the radially inner surface of the support protrusion and the outer peripheral surface of the bearing member is determined by the compressive deformation of the support protrusion. .

Therefore, the bearing member can be made considerably larger than in the case where it is defined by the elastic deflection of the mounting portion, and the bearing member can be held sufficiently firmly.

Furthermore, in order to form a plurality of supporting protrusions extending in the axial direction at intervals in the circumferential direction on the circular inner circumferential surface of the mounting part, it is necessary to A plurality of grooves may be formed at intervals. Therefore, there is no low-strength portion such as the above-mentioned thin flap piece in the die-casting mold, and the die-casting mold can be used for a long period of time.

Hereinafter, specific examples of the casing constructed according to the present invention will be described in more detail.

Referring to FIG. 3, which illustrates the mounting portion of a casing constructed in accordance with the present invention, the casing may be formed by die casting from a suitable light metal material such as aluminum or an aluminum-based alloy. , a circular inner circumferential surface 4 is provided on the inner surface of the side wall 2, similar to the mounting part in a conventional casing.
A mounting portion 6 is formed. According to the present invention, a plurality of support protrusions 20 are formed on the circular inner circumferential surface 4 at appropriate intervals in the circumferential direction and extend in the axial direction. In the specific example shown in FIG. 3, eight support protrusions 20 are formed at equal intervals in the circumferential direction. The radial protrusion heights of these support projections 20, that is, the amount of protrusion from the circular inner circumferential surface 4, are all substantially the same. The plurality of support protrusions 20 may be formed over the entire circular inner circumferential surface 4 in the axial direction, or
Alternatively, it may be formed only in a portion thereof.

When molding the casing by die-casting, in order to perform die-cutting, the circular inner circumferential surface of the mounting portion 6 as well as each of the plurality of support protrusions 20 formed thereon are Although it is necessary to generate a draft angle, in the casing constructed according to the present invention, the draft angle in each of the plurality of support protrusions 20 is generated on both sides of the support protrusion 20 in the circumferential direction. It is important that the protrusions 20 are not formed on the radially inner surface thereof. As will be clearly understood from the embodiment described later with reference to FIG. Draft angles are formed on both circumferential side surfaces of the support protrusion 20 so as to gradually increase from the end (projection end) to the bottom end (base end). However, there is substantially no draft on the radial inner surface of each of the support projections 20, and therefore the diameter D ₃ of the circle defined by the radial inner surface of each of the support projections 20 does not vary in the axial direction. It is made evenly.

Continuing the explanation with reference to FIG. 4 as well as FIG. 3, in the mounting portion 6 as described above, the inner diameter D ₁ of the circular inner peripheral surface 4 is equal to the bearing member 1 to be mounted thereon.
It is important that the outer diameter D ₂ of the circular outer circumferential surface 12 of No. 4 is set slightly larger than the outer diameter D 2 of the circular outer circumferential surface 12 of No. 4. On the other hand, the diameter D ₃ of the circle defined by the radial inner surface of the plurality of support protrusions 20 is
It is important that the outer diameter is set slightly smaller than the outer diameter _D2 .

The radial protrusion height of the plurality of support protrusions 20 depends on the inner diameter D ₁ of the circular inner circumferential surface 4, the outer diameter D ₂ of the circular outer circumferential surface 12, and the material used for die casting of the casing. 1/100 to 10/10
It is preferably about 0 mm (in order to clearly illustrate the support protrusion 20, the radial protrusion height of the support protrusion 20 is exaggerated in the drawing).

In the above-described casing according to the present invention, a shaft 10 to which a gear (see FIG. 1) is fixed is rotatably mounted in the mounting portion 6 of the casing without any machining after die casting. A bearing member 14 for supporting is attached by press fitting such as press fitting. In this way, due to the press-fitting of the bearing member 14, the plurality of support protrusions 20 are forcibly deformed so that the diameter _D3 is made equal to the outer diameter _D2 of the outer peripheral surface of the bearing member 14, and thus the bearing member 14 is mounted in the mounting section 6. As described above, no draft angle is generated on the radial inner surface of the plurality of support protrusions 20, and the plurality of support protrusions 20
Since the diameter D ₃ of the circle defined by the radial inner surface of Therefore,
The bearing member 14 is supported over its entire axial width by the radially inner surfaces of the plurality of support projections 20, and is thus held sufficiently reliably and firmly.

By the way, in die casting, the dimensions of each part of the mounting part 6, especially the diameter D 3 of a circle defined by the inner diameter D ₁ of the circular inner circumferential surface 4 and the radial inner surface of the plurality of support projections ₂₀ , are set to a predetermined value. However, as long as the die casting is carried out using the same mold, the dimensions of each part of the molded casing mounting portion 6 will all be substantially the same. Therefore, in the casing according to the present invention, as long as the casing is die-cast using the same mold, the bearing member 14 for the mounting portion 6 is
The mounting will be substantially the same without any variation. Therefore, first make a mold,
The casing is die-cast using such a mold, and then the gear 8 to be fixed to the shaft 10 (see FIG. 1) and the gear 8 are formed according to the press-fitted state of the bearing member 14 into the mounting portion 6 of the casing.
By appropriately setting the amount of shift of the gear (not shown) that engages with the casing, substantially the same and appropriate engagement of the gears can be achieved without causing any variation for all casings. Can be done.

Example JIS standard 6001 deep groove ball bearing (diameter of circular outer surface
D ₂ = 28 mm), a mounting part 106 having a shape as shown in Fig. 6 is provided on the inner wall surface.
A casing having the following properties was molded from an aluminum material by die casting.

The dimensions of each part of the mounting part 106 were as follows.

Depth ₁ of the mounting portion 106 ……5.00mm Depth ₂ of the part without draft at the bottom of the mounting portion 106 ……1.00mm Maximum inner diameter D ₁ −max of the circular inner peripheral surface of the mounting portion 106
...28.25mm Minimum inner diameter D of the circular inner circumferential surface of the attachment part 106 ₁ ^- min
...27.95mm Diameter of the circle defined by the radially protruding end of the support protrusion 120 D ₃ ...27.80mm The support protrusion 120 is placed evenly in the circumferential direction on the circular inner circumferential surface of the mounting portion 106. Twelve support projections 120 are arranged at intervals, and the circumferential width of each support projection 120 is 0.4 mm at the receiving end (protruding end) of the mounting section 106 and 0.5 mm (base end) at the bottom end (base end) of the mounting section 106. Therefore, the draft angle in the support protrusion 120 is present on both sides in the circumferential direction.

When the deep groove ball bearing according to JIS standard 6001 was press-fitted into the mounting portion 106 as described above and mounted, it was successfully mounted as required and was able to be held sufficiently reliably and firmly. When the shape of the support protrusion 120 was observed after being installed, it was found that before being installed, it had the shape shown by the two-dot chain line in FIG. 7, but after being installed, it changed to the shape shown by the solid line in FIG. Was.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing a conventional casing. FIG. 2 is an enlarged partial cross-sectional view of a part of the mounting portion of the casing shown in FIG. 1; FIG. 3 is a partial front view showing a mounting portion of a first embodiment of a casing constructed in accordance with the present invention. FIG. 4 is a partial sectional view of the mounting portion shown in FIG. 3. FIG. 5 is a partial sectional view showing the shape of the mounting part in the embodiment of the present invention.
FIG. 6 is an enlarged partial front view showing deformation of the support protrusion in the embodiment of the present invention. 2...Side wall of casing, 4...Circular inner circumferential surface of mounting portion, 6...Mounting portion, 14...Bearing member, 20
...Support protrusion.

Claims (1)

[Scope of Claims] 1. A casing molded from a light metal material by die-casting, the inner wall surface of which is formed with a mounting portion having a circular inner circumferential surface, which rotatably supports a shaft. In a casing in which a bearing member having a circular outer circumferential surface is press-fitted into the mounting part for the purpose of A protrusion is formed, a draft angle of each of the support protrusions is generated on both side surfaces in the circumferential direction, and a width of each of the support protrusions in the circumferential direction gradually increases from the receiving end to the bottom end of the mounting part. casing, characterized in that the diameter of the circle defined by the radially inner surface of each of the support projections does not vary in the axial direction.