JP2006205174A - Fastening structure for magnesium parts - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fastening structure for magnesium parts which is used under comparatively high temperature atmosphere, and in which a fastening axial force is hardly reduced at a low cost, with respect to the structure for fastening, with a bolt, the parts using the magnesium or the magnesium alloy. <P>SOLUTION: When a second member 2 is fastened to a first member 1 composed of the magnesium or the magnesium alloy by using the metal-made bolt 3, a metal member 4 composed of an iron-base material and an aluminum alloy or a heat-resistant magnesium alloy and provided with a fall-out preventive means and a rotating preventive means from the first member 1 together with a female-screw part 4a for screwing to the metal-made bolt 3 is cast in the first member 1 to make the cast-in part and the bolt 3 passed through a bolt inserting hole 2a formed in the second member 2 is fastened into the female-screw part 4a in the cast-in part 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fastening structure of magnesium parts using bolts, for example, magnesium used for fastening parts which require weight reduction while being used in a relatively high temperature environment such as automobile engines and power train parts. The present invention relates to a fastening structure for alloy parts.

  In general, when bolting a part used in a relatively high temperature environment, such as a powertrain part such as an automobile engine or transmission, and which is required to be reduced in weight, as shown in FIG. Both or one of the two members 53 is made of a magnesium alloy part, and both the members 51 and 53 are fastened by a metal bolt 3 such as steel or aluminum alloy. Due to the heat effect, the female thread portion 51a of the first member 51 and the bolt seat surface portion 53a of the second member 53 may sag, resulting in a decrease in fastening axial force.

Therefore, as a countermeasure against such a decrease in fastening axial force, conventionally, calcium (Ca), strontium (Sr), or a rare earth metal is added to the magnesium alloy used as the first member 51 or the second member 52, Magnesium alloy parts with improved heat resistance were used, and special bolts with different bolt lengths and diameters were used to secure the area of the fastening part.
Furthermore, attempts have been made to increase the fastening force by increasing the number of bolts in the fastening portion.

However, magnesium alloy parts that have been improved in heat resistance by adding calcium, strontium, or rare earth metals to the above-described magnesium alloy generally have a problem in productivity at the time of casting, and the performance is sufficiently high. I couldn't do it.
Furthermore, the magnesium alloy to which these metals are added is inevitably expensive from the viewpoint of raw materials, and it is difficult to recycle because various metal elements are contained.

  Similarly, changing the size of the bolt used for fastening, such as the engagement length and bolt diameter, and using it as a special bolt, or making a design change that increases the number of bolts at the fastening part will also increase costs. In addition to the problem of connection, there are many problems such as restrictions on the layout of parts and an increase in the weight of parts when the bolt size is changed or the number of bolts is increased. It was a problem to solve the problem.

  The present invention has been made in view of the above-described problems in bolt fastening of conventional magnesium parts, and is used in a relatively high temperature environment in a fastening structure using bolts of parts using magnesium or a magnesium alloy. It is an object of the present invention to provide a magnesium part fastening structure that can be manufactured at low cost and has little reduction in fastening axial force.

  As a result of intensive studies aimed at achieving the above object, the present inventors have determined that the internal thread portion that is screwed to the metal bolt and the bolt seat surface portion that is in contact with the head portion of the metal bolt are made of an iron-based material or aluminum. Castability that is formed from a dissimilar metal having excellent heat resistance strength, such as an alloy or a heat-resistant magnesium alloy to which silicon, calcium, rare earth metal, etc. are added, and which constitutes a fastened member (first or second member) Found that it is possible to prevent the magnesium parts from sagging and improve the fastening axial force by casting them with a general-purpose magnesium alloy excellent in bolting and bolting both members at this part. I arrived.

  This invention is based on the said knowledge, Comprising: The 1st fastening structure of the magnesium component of this invention is a magnesium component which fastens the 2nd member using the metal volt | bolt to the 1st member which consists of magnesium or a magnesium alloy. A fastening structure comprising an iron-based material, an aluminum alloy, or a heat-resistant magnesium alloy, and having a female screw portion screwed into the metal bolt, and a slip prevention means and a rotation prevention means from the first member While the part is cast in the first member, the second member has a bolt insertion hole for inserting the metal bolt, and the second fastening structure of the magnesium part of the present invention is A magnesium part fastening structure for fastening a second member made of magnesium or a magnesium alloy to a first member using a metal bolt, wherein the first member is the above While having a female thread portion that is screwed into a genus bolt, it is made of an iron-based material, an aluminum alloy, or a heat-resistant magnesium alloy, together with a bolt insertion hole for inserting the metal bolt and a bolt seat surface that is in pressure contact with the bolt head. The cast-in part provided with the means for preventing the two members from coming off and the means for preventing the rotation are cast in the second member.

  According to the present invention, the female threaded portion of the first member and the bolt seating surface portion of the second member, which are likely to sag due to the thermal influence of the engine, are made of a dissimilar material excellent in heat resistance made of iron-based material, aluminum alloy or heat-resistant magnesium alloy Since the dissimilar material portion is cast by the magnesium material forming the main body portion of the first member or the second member, the first member or the second member has a low alloy component and is inexpensive and castable. Even if an excellent general-purpose magnesium-based alloy material is used, when the heat effect of the engine is applied for a long time, the internal thread portion and the bolt seat surface portion do not sag, and the temperature is relatively high. It can be used in the environment and can be made of a magnesium part fastening structure that is inexpensive and has little decrease in fastening axial force. For example, a transmission case or engine By applying the oil pan of the results in an extremely excellent effect that can contribute to weight reduction of the automobile.

  Hereinafter, the fastening structure of the magnesium part of the present invention will be described more specifically.

  FIG. 1 shows a first embodiment of the present invention. In the fastening structure of the magnesium part, the fastened member 1 (first part) made of magnesium or a magnesium alloy and provided with a female screw part 4a described later. Member) and the fastening member 2 (second member) are fastened by the metal bolt 3.

In the drawing, the fastening member 2 as the second member is formed with a bolt insertion hole 2a for allowing the metal bolt 3 to pass therethrough.
On the other hand, the fastened member 1 that is the first member includes a metal member 4 provided with a female screw portion 4 a that is screwed into a male screw portion formed on the bolt 3 on the fastening surface side with the fastening member 2. The metal member 4 is formed in advance from one kind of metal selected from an aluminum alloy, a ferrous material such as steel and cast iron, or a heat-resistant magnesium alloy to which a metal element as described later is added. Then, it is cast by the magnesium alloy constituting the fastened member 1, and becomes a cast-in part in the fastened member 1.

  This metal member 4 (casting portion) has an action of preventing sag at the time of bolt fastening, and as described above, an aluminum alloy, an iron-based material, or a heat-resistant magnesium alloy, for example, silicon (Si). , Silver (Ag), calcium (Ca), strontium (Sr), yttrium (Y), zirconium (Zr), and rare earth metals (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Mg-Al-Zn based alloy which is a magnesium alloy for die casting, which is composed of one kind of metal selected from magnesium alloys to which one or more kinds of metals selected from Ho, Er, Tm, Yb, Lu) are added. The to-be-fastened member 1 is formed by casting with a Mg—Al—Mn alloy or the like.

Here, the addition amount of the metal in the heat-resistant magnesium alloy is desirably in the range of 0.1 to 2.0% by mass ratio. That is, when the amount of added metal is 0.1% by mass or less, the sag resistance effect of the magnesium alloy used as a metal for preventing sag is reduced. On the other hand, even when 2.0% by mass or more is added, the sag resistance effect is constant. Therefore, it is not improved any more and the cost is increased. Therefore, it is preferable to add within this range.
When one or more of the above metals is added to a magnesium alloy used as a metal member for preventing sagging, the heat resistance of the magnesium metal itself is improved, so that the sag resistance in the pressurizing portion is improved and the tensile properties at room temperature. As a result, it is possible to prevent a reduction in the axial force during bolt fastening.

  As shown in FIG. 1, the metal member 4 forming the cast-in part includes a fastening member 2 as an anti-disengagement means for holding the cast-in metal member 4 so as not to fall off the fastened member 1. From the contact surface side, the metal member 4 has a shape that expands toward the inside of the fastened member 1, and when the metal member 4 after fastening is rotated together with the bolt 3, the firm fastening cannot be performed. As a means for preventing rotation, a part or all of the cross section perpendicular to the bolt rotation axis is not a perfect circle but an ellipse.

  In other words, as a means for preventing slipping, the metal member 4 has a maximum or minimum portion in a cross-sectional area perpendicular to the bolt rotation axis, and the maximum or minimum portion is located at a portion other than the surface of the fastened member 1. It would be good if you do. Further, as the rotation preventing means, it suffices that at least a part of the cross section perpendicular to the metal member 4 bolt rotation axis is non-circular, for example, a polygon such as an ellipse, a triangle or a quadrangle, a star or a gear, etc. What is necessary is just to make it an uneven | corrugated shape.

As described above, a general-purpose magnesium alloy such as an Mg—Al—Zn alloy or an Mg—Al—Mn alloy can be used as the casting base material used as the fastened member 1 (first member).
On the other hand, the metal material of the fastening member 2 (second member) is not particularly limited, and the number of the fastening member 2 is not limited to only one as illustrated, and the fastening member 1 includes a plurality of fastening members. It is also possible to bolt 2.

  In the magnesium part fastening structure described above, by screwing the metal bolt 3 passed through the bolt insertion hole 2a formed in the fastening member 2 into the female screw part 4a formed in the cast-in part 4 of the member 1 to be fastened. Since both the members 1 and 2 can be fastened and the metal member is used as the cast-in part only in the female thread portion of the bolt fastening portion, it is possible to reduce the weight of the magnesium component as the fastened member. Thus, a light and inexpensive fastening structure as a whole can be obtained.

  FIG. 2 shows a second embodiment of the present invention. In the fastening structure of the magnesium part, the fastened member 11 (first member) provided with the female screw portion 11a is made of magnesium or a magnesium alloy. The fastening member 12 (second member) formed is fastened by the metal bolt 3.

In the figure, the fastening member 11 as the first member is formed with a female screw portion 11a that is screwed into the male screw portion formed on the metal bolt 3 as described above.
On the other hand, the fastened member 12 that is the second member has the same thickness as the fastened member 12, and the bolt insertion hole 14 a for passing the bolt 3 and the head of the bolt 3 against the head. A metal member 14 having a bolt seat surface 14b in contact with the metal member 14 is provided, and the metal member 14 is a metal selected from the group consisting of aluminum alloys, iron-based materials such as steel and cast iron, and heat-resistant magnesium alloys as described above. Are formed in advance, and are cast with a magnesium alloy constituting the fastening member 12 to form a cast-in part.

  Similarly, this metal member 14 also has an action of preventing sag at the time of bolt fastening, such as the above-described aluminum alloy, iron-based material, or, for example, Si, Ag, Ca, Sr, Y, Zr, And one kind of metal selected from a heat-resistant magnesium alloy to which one or more kinds of metals selected from rare earth metals are added, and this metal member 14 is made of the above Mg-Al-Zn alloy, The fastening member 12 is formed by casting with a magnesium alloy such as an Mg—Al—Mn alloy. The metal member 14 does not necessarily have to penetrate the fastening member 12 as long as the metal member 14 includes the bolt insertion hole 14a and the bolt seat surface 14b.

  As shown in FIG. 2, the cast-in part is such that the vertical cross-sectional shape is H-shaped so that the minimum part of the cross-sectional area perpendicular to the bolt rotation axis is located at the central portion of the fastening member 12 plate thickness. This functions as a means for preventing a dropout. Further, as a rotation preventing means after fastening, a part or all of the cross section perpendicular to the bolt rotation axis is not a perfect circle but an ellipse.

  It does not specifically limit as a metal material which comprises the to-be-fastened member 11 (1st member). On the other hand, as the casting base material used as the fastening member 12 (second member), a general-purpose magnesium alloy such as Mg—Al—Zn alloy or Mg—Al—Mn alloy can be used as in the above embodiment. Also, the number is not limited to one, and a plurality of fastening members 12 can be bolted to the fastened member 11.

  Also in the above-described magnesium component fastening structure, the metal bolt 3 passed through the bolt insertion hole 14 a formed in the metal member 14 cast into the fastening member 12 is screwed into the female screw portion 11 a formed in the fastened member 11. Since both the members 11 and 12 can be fastened and the metal member is cast only in the bolt seating surface portion of the bolt fastening portion, it is possible to reduce the weight of the magnesium component as the fastening member. Thus, as in the above-described embodiment, a light and inexpensive fastening structure can be obtained as a total.

In addition, also when using an aluminum alloy as a material of the metal members 4 and 14 shown in FIG.1 and FIG.2, since a fall of a fastening axial force is little compared with a general purpose magnesium alloy, it can obtain a favorable result. it can. At this time, an aluminum alloy for die casting can be suitably used.
Further, as a material of the metal members 4 and 14, iron-based material steel such as steel and cast iron is preferably used since the decrease in fastening axial force is smaller than that of a general-purpose magnesium alloy, as is the case with an aluminum alloy for die casting. Since these metal members 4 and 14 are cast with an Mg—Al—Zn alloy or an Mg—Al—Mn alloy, all of the fastened members 1 and 11 and the fastening members 2 and 12 are made of an aluminum alloy or steel. Compared to parts made of materials, the parts can be made extremely light.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited at all by these Examples.

Example 1
First, as shown in FIG. 1, it has a polygonal vertical cross-sectional shape, and has an elliptical shape with a maximum cross-sectional area of 60 mm in height and perpendicular to the bolt rotation axis, having a major axis of 40 mm and a minor axis of 30 mm. A metal member 4 made of an ADC12 material (Al-Si-Cu system) defined as aluminum die casting is prepared, and a pilot hole of 8 mm diameter is drilled to a depth of 50 mm in this shaft core part, and then an M8 female thread part 4a was formed.
Next, the metal member 4 is casted with a general-purpose magnesium alloy (Mg—Al—Zn system) defined in ASTM as AZ91D, whereby the fastened member 1 having a cast-in part on the surface of the member as shown in the figure. (First member) was obtained.

  Next, a bolt insertion hole 2a having a diameter of 9 mm is formed in a plate material made of the ADC12 and having a thickness of 20 mm to form a fastening member 2 (second member), and a steel bolt 3 (M8 × 50 mm) passed through the bolt insertion hole 2a. The bolt fastening joint of the magnesium part as shown in FIG. 1 was obtained by screwing the length) into the female screw part 4a formed in the cast-in part 4 of the fastened member 1 so that the initial surface pressure was 100 MPa.

And after hold | maintaining the said bolt fastening joint fastened by the initial surface pressure of 100 Mpa in the atmosphere of 125 degreeC for 200 hours, the surface pressure was measured again and the axial-force retention rate of the volt | bolt with respect to the said initial surface pressure was calculated | required.
The results are shown in Table 1 together with combinations of materials.

(Example 2)
By repeating the same operation as in Example 1 except that FCD700 material defined as spheroidal graphite cast iron in JIS G5502 is used as the material of the metal member 4, bolt fastening of magnesium parts as shown in FIG. A joint was obtained.
And the said bolt fastening joint was similarly hold | maintained in the atmosphere of 125 degreeC for 200 hours, and the axial force retention of the bolt was similarly calculated | required. The results are also shown in Table 1.

(Example 3)
The above implementation except that the heat-resistant magnesium alloy (Mg-Al-Si system, Si: 1.0%, rare earth metal: 0.1% added) defined as ASTM 21 in ASTM is used as the material of the metal member 4 By repeating the same operation as in Example 1, a bolted joint of magnesium parts as shown in FIG. 1 was obtained.
And after holding the said bolt fastening joint similarly in 125 degreeC atmosphere for 200 hours, the axial force retention of the bolt was similarly calculated | required. The results are also shown in Table 1.

Example 4
First, as shown in FIG. 2, it has an H-shaped vertical cross-sectional shape, and has an elliptical shape with a height of 20 mm and a vertical direction of the bolt rotation axis having a major axis of 40 mm and a minor axis of 30 mm. Metal member 14 made of a specified heat-resistant magnesium alloy (Mg—Al—Si system, Ca: 1.0%, rare earth metal: 3.0% added), and having a 9 mm diameter bolt insertion hole 14a at the center. The metal member 14 is cast with a general-purpose magnesium alloy (Mg—Al—Zn) specified by ASTM as AZ91D, and as shown in FIG. A fastening member 12 (second member) having a thickness of 20 mm was obtained.

  Next, an 8 mm diameter pilot hole is drilled to a depth of 50 mm on the fastening side surface of the fastened member 11 (first member) made of the ADC12 material, and then an M8 female thread portion 11 a is formed. By screwing the steel bolt 3 (M8 × 50 mm length) passed through the bolt insertion hole 14a formed in the portion 14 into the female screw portion 11a of the fastened member 11 so that the initial surface pressure becomes 100 MPa, A bolted joint of magnesium parts such as 2 was obtained.

Similarly, after holding the bolt fastening joint fastened at the initial surface pressure of 100 MPa in an atmosphere of 125 ° C. for 200 hours, the surface pressure is measured again to obtain the axial force retention ratio of the bolt with respect to the initial surface pressure. It was.
The results are shown in Table 1 together with combinations of materials.

(Example 5)
Except that the metal member 14 is made of the ADC12 material, the same operation as in Example 4 was repeated to obtain a magnesium component bolted joint as shown in FIG.
And after holding the said bolt fastening joint similarly in 125 degreeC atmosphere for 200 hours, the axial force retention of the bolt was similarly calculated | required. The results are also shown in Table 1.

(Example 6)
Except for using a heat-resistant magnesium alloy (Mg-Al-Si system, Si: 1.0%, rare earth metal: 0.1% added) defined as ASTM in ASTM as the material of the metal member 14, By repeating the same operation as in Example 4, a bolted joint of magnesium parts as shown in FIG. 2 was obtained.
And the said bolt fastening joint was similarly hold | maintained in the atmosphere of 125 degreeC for 200 hours, and the axial force retention of the bolt was similarly calculated | required. The results are also shown in Table 1.

(Comparative Example 1)
As shown in FIG. 3, except that the bolt 3 is screwed into the female screw portion 51 a formed on the fastened member 51 (first member) made of the general-purpose magnesium alloy without casting the metal member 4. By repeating the same operation as in Example 1, a bolted joint for magnesium parts was obtained.
And the obtained bolt fastening joint was similarly hold | maintained in the atmosphere of 125 degreeC for 200 hours, and the axial force retention of the bolt was similarly calculated | required. The results are also shown in Table 1.

(Comparative Example 2)
As shown in FIG. 3, the above-described implementation is performed except that the bolt 3 is passed through the bolt insertion hole formed in the fastening member 53 (second member) made of the general-purpose magnesium alloy without casting the metal member 14. By repeating the same operation as in Example 4, a bolted joint for magnesium parts was obtained.
Then, after the obtained bolted joint was similarly held in an atmosphere of 125 ° C. for 200 hours, the axial force holding ratio of the bolt was similarly obtained. The results are also shown in Table 1.

  As a result of comparing the axial force after fastening the bolt with the bolt axial force holding force after elapse of 125 ° C. × 200 hours, the conventional magnesium alloy, that is, the general-purpose magnesium alloy, is used for the female thread portion or the bolt seat surface portion. In Comparative Examples 1 and 2 using an aluminum alloy as a mating member, the axial force retention was 60%, and it was confirmed that the settling was large.

On the other hand, in Example 2 in which a member made of an iron-based material was cast into the female thread portion of the fastened member, the axial force retention was 100%, and no reduction in axial force was observed. Further, in Examples 1 and 5 in which a metal member made of an aluminum alloy was cast into the female screw portion or the bolt seat surface portion, the axial force retention rate was 98%, and it was confirmed that there was little sag.
Further, in Examples 3, 4 and 6 in which a metal member made of a heat-resistant magnesium alloy added with a predetermined metal element is cast into the female thread portion or the bolt seat surface portion, the axial force retention is 87%, 93% and 87%, respectively. % And it was confirmed that there was little sag.

It is a section explanatory view showing one embodiment of a fastening structure of magnesium parts of the present invention. It is sectional explanatory drawing which shows other embodiment of the fastening structure of the magnesium components of this invention. It is sectional explanatory drawing which shows the fastening structure of the conventional magnesium component.

Explanation of symbols

1, 11 Fastened member (first member)
2, 12 Fastening member (second member)
2a Bolt insertion hole 3 Metal bolt 4, 14 Metal member (casting part)
4a Female thread part 11a Female thread part 14a Bolt insertion hole 14b Bolt seating surface

Claims (6)

In the fastening structure of the magnesium part that fastens the second member to the first member made of magnesium or a magnesium alloy using a metal bolt,
The first member has a cast-in part cast with magnesium or a magnesium alloy forming the first member, and the cast-in part is made of an iron-based material, an aluminum alloy, or a heat-resistant magnesium alloy, and the metal bolt Along with a female thread portion screwed into the first member, the first member is provided with a means for preventing removal and a means for preventing rotation,
The magnesium part fastening structure, wherein the second member includes a bolt insertion hole for inserting the metal bolt.   2. The fastening of a magnesium part according to claim 1, wherein a maximum part or a minimum part of a cross-sectional area in a direction perpendicular to the bolt rotation axis in the cast-in part is located at a part other than the surface of the first member. Construction. In the fastening structure of the magnesium part that fastens the second member made of magnesium or magnesium alloy to the first member using a metal bolt,
The first member includes an internal thread portion that is screwed into the metal bolt,
The second member has a cast-in part that is cast with magnesium or a magnesium alloy forming the second member, and the cast-in part is made of an iron-based material, an aluminum alloy, or a heat-resistant magnesium alloy, and the metal bolt A fastening structure for magnesium parts, comprising: a bolt insertion hole through which the bolt is inserted; and a bolt seat surface that is in pressure contact with the bolt head, and a means for preventing the second member from coming off and a means for preventing the rotation.   4. The fastening of a magnesium part according to claim 3, wherein a maximum part or a minimum part of a cross-sectional area in a direction perpendicular to the bolt rotation axis in the cast-in part is located at a part other than the surface of the second member. Construction.   The fastening structure for a magnesium part according to any one of claims 1 to 4, wherein at least a part of a cross section in a direction perpendicular to the bolt rotation axis in the cast-in part is non-circular.   The heat-resistant magnesium alloy contains at least one metal selected from the group consisting of silicon, silver, calcium, strontium, yttrium, zirconium and rare earth metals. Fastening structure for magnesium parts as described in one item.

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