JP2005264989A - Pulley made of magnesium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulley made of magnesium which prevents a body and a bearing from idling while not only obtaining characteristics of magnesium by employing magnesium (or a magnesium alloy) as molding materials but also being able to form and surely hold an almost complete round pulley by insert molding in which a bearing is inserted. <P>SOLUTION: In a pulley having a bearing structure in which a bearing is integrally assembled, a pulley body is formed of magnesium or a magnesium alloy. An annular resin part made of a plastic is interposed between the pulley body and a bearing. By so doing, the annular resin part is insert-molded taking the pulley body and the bearing as insert parts. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnesium pulley having a bearing bearing structure used for transmitting power at high speed via a belt as in, for example, an automobile transmission, and a method for manufacturing the same.

  Many pulleys are used in automobiles. Especially, pulleys in transmissions are severely rotated at high speeds, and if they are distorted with respect to a perfect circle, they cause noise, Moreover, since it becomes a factor of belt breakage, it is required to form the pulley into a perfect circle as much as possible. However, the fact is that a pulley that ideally meets the demand has not been provided.

  Conventional pulleys used for high-speed rotation are generally made of steel, and basically have a vehicle structure with an arm between a boss that fits the shaft and a rim that the belt hangs. In a pulley having a bearing structure, the bearing is fitted to the boss. However, in such a pulley, even if the distortion with respect to the roundness in the inner diameter of the main body is small in the outer diameter, the distortion is increased in the outer diameter (several times to several tens of times) by fitting the bearing. It appears in a ripple effect. Further, since distortion occurs due to subsequent dimensional changes, it is not sufficient to prevent noise generation and belt breakage. In order to solve this problem, it is conceivable to use a magnesium alloy having excellent characteristics as a pulley material.

  Magnesium has a dimensional stability that can withstand harsh use conditions with little dimensional change over time, vibration absorption (maximum vibration absorption among practical metals, extending the life of machinery and equipment, and reducing noise) Damping ability), resistance to deformation is high, and it has a puncture resistance that “dent” due to impact is less likely to occur compared to aluminum alloy and mild steel. In addition, it has the lightest structural material strength among practical metals (specific strength is greater than that of aluminum alloys and steel), heat dissipation properties, machinability, electromagnetic shielding properties, recyclability, and abundant resources. It can be a suitable use condition.

  In addition, an excellent characteristic of magnesium is that it can be molded in a mold by means of die casting or injection molding (thixomold method). Among them, according to the thixomold method, a chip is used as a raw material, and when it is put into a cylinder from a hopper, it is carried to a tip heated to a set temperature therein and eventually a shearing force by a screw. When heated from the cylinder, it becomes a semi-molten state with thixotropy, advances forward of the screw at the tip of the cylinder, and is temporarily stored there, and then the molten metal is injected into the mold at a high speed.

  Here, thixotropy is a phenomenon in which when a shearing force is applied to an alloy in a semi-molten state and the solid phase is granulated, the viscosity of the alloy decreases and the fluidity increases. At this time, since the molding temperature is low, the amount of solidification shrinkage is small, and surface defects, gas defects and the like are reduced. As a result, it is possible to obtain an excellent material having good dimensional accuracy, less deformation, a fine granular structure, and improved mechanical properties. Incidentally, when the dimensional accuracy of injection molding is compared with plastic, plastic is ± 0.1 to 0.15%, whereas magnesium is ± 0.005 to ± 0.01%.

  Therefore, when the product is made of a magnesium alloy, it is easy to obtain a state as close to a perfect circle as possible with respect to the bearing by injection molding in which a bearing is inserted. This is because magnesium is the metal with the lowest potential (high ionization tendency) among practical metals. When it is joined to a bearing of an iron alloy as another metal, a current flows from the potential difference to the boundary, and electrolysis occurs. As a result, an electrolytic corrosion phenomenon occurs in which magnesium having a relatively low potential is vigorously alloyed, and this causes a deviation from the center in the roundness of the pulley.

  Moreover, the bearing is filled with grease by being injected inside the cage as its own lubricant or impregnated in a ball or the like, but even a magnesium product in which the bearing is closely combined by insert molding, Grease enters between the magnesium and the bearing (outer ring of the cage) with a slight electrolytic corrosion portion as an entrance, which causes idle rotation between the pulley body and the bearing.

  Thus, mass-produced magnesium castings and injection-molded products have excellent performance that is incomparable to other materials in terms of dimensional accuracy. There were further problems in finding the perfect circle to the limit.

  Regardless of the die casting method or semi-solidification method, when a high-speed fluid with a specific gravity of 1.6 or more and a flow velocity of 1.8 m / s or more behaves in the mold, it is rare that the metal material is completely filled in the mold. This is because gas or the like is usually involved. Moreover, although a normal molded product has a complicated structure due to ribs, flanges, and the like, it is also possible that cracks tend to occur frequently at the roots of such ribs and flanges of the molded product.

  The reason for this is that when the metal material flows in the mold at a high speed, the generation of the translational flow is much higher than the diffusion flow, which is very different from the flow of the synthetic resin. As a metal material with a flow direction property), it is difficult to enter the inside of a complex structure because the narrow part is out of the straight direction although the flux is small. is there. Incidentally, when the fluid is caused to flow out of the ejection hole, the diameter of the fluid flux is smaller than that of the hole in the vicinity of the hole. This phenomenon is called “bending phenomenon” in physics. In other words, in this case, the flow velocity is linear and intensive without the flexibility to bend in a complicated manner, and this is the cause that the molten metal cannot easily enter the complicated place in the complicated mold. Yes.

  Looking at the product specifications of the pulleys required from the usage performance and usage environment, the uneven surface of the contact part with the belt used for power transmission and the roundness of dimensional accuracy and the hardness to maintain it Is a necessary condition. Regarding hardness, if the belt tension biases the surface of the pulley and wears, an eccentric motion occurs. Conventional injection molding of synthetic resin and die casting of aluminum material or magnesium material cannot satisfy the necessary conditions due to such a narrowing phenomenon.

  In view of the above situation, the present invention not only obtains the characteristics by using a magnesium alloy (or magnesium) as a molding material, but also inserts a pulley that is close to a perfect circle by insert molding to insert a bearing. An object of the present invention is to provide a magnesium pulley that can be molded and can be securely held, and that the main body and the bearing do not rotate freely, and a method for manufacturing the same.

  In order to solve the above-mentioned problems, a first invention (Claim 1) is a pulley having a bearing structure in which a bearing is integrally assembled, wherein the pulley body is made of magnesium or a magnesium alloy, and the pulley body is interposed between the pulley body and the bearing. Provided is a magnesium pulley characterized in that an annular resin part made of plastic is interposed, and the annular resin part is insert-molded using a pulley body and a bearing as insert parts.

  According to a second aspect of the present invention (invention 2), in a pulley having a bearing structure in which a bearing is integrally assembled, a pulley body is formed of magnesium or a magnesium alloy, and an annular resin portion made of plastic is provided between the pulley body and the bearing. The present invention provides a magnesium pulley characterized in that a pulley body is insert-molded with an intervening combination of a bearing and an annular resin portion as an insert part.

  According to said structure, since a pulley main body is formed with a magnesium alloy, not only the above-mentioned various characteristics as magnesium can be obtained but also a structure in which the pulley main body and the bearing are not in direct contact by the intervention of the annular resin portion. Therefore, there is no inconvenience that the pulley body having a relatively low electric potential is damaged by electric corrosion, and the strength and roundness of the pulley body can be obtained, and the pulley body can be safely and securely held.

  The main reason for the roundness is that in addition to the strength, dimensional stability, dent resistance, etc. of the magnesium alloy, a fixed connection structure for each part is obtained by insert molding that contains the bearing. . In the meantime, there is no penetration of grease, and the idle rotation of the pulley body with respect to the bearing is prevented.

  Although maintaining the roundness prevents the belt from being broken, the heat dissipation characteristics and vibration absorption of magnesium also work well. Of these, the heat dissipation characteristics are several hundred times that of plastic materials.

  Further, in the third invention (Claim 3), in the manufacture of a pulley having a bearing structure in which a bearing is integrally incorporated, when the pulley body is formed by die casting or injection molding of magnesium or a magnesium alloy, both sides of the pulley body are A circular annular groove centering on the center of the pulley is formed between the rim portion on the belt joining side and the boss portion on the bearing outer ring side, so that the molds on both sides have annular concave grooves. In addition to forming a corresponding annular protrusion, gates that open toward the other annular protrusion are formed in one or both annular protrusions at regular intervals along the circle, with a constriction phenomenon from the gate. Magnesium characterized in that the metal material to be injected is changed from a narrow portion between the two annular convex portions to a relatively wide rim portion and a boss portion and flows as a diffusion flow. To provide a process for the production of manufactured pulley.

  Since the magnesium pulley manufacturing method is configured as described above, when the pulley body is molded, when a metal material is injected between the annular protrusions of both molds from each gate, the annular protrusions facing each other As a result, the momentum is changed in the direction of the belt joining side and the bearing outer ring side, and as a result, the constriction phenomenon disappears and the flow changes from a translational flow to a diffusion flow. It is evenly distributed until densely packed.

  In addition, since the space between the two annular protrusions is a narrow part, it is surely filled with the increased pressure in this part, and of course, ribs are equally spaced in the circular direction in the annular groove of the pulley body. If the slits corresponding to the ribs are formed at equal intervals in the annular groove of the mold so as to be formed, and the gate is provided at the center between the adjacent slits (Claim 4), Filling is ensured and ribs are formed densely, and the material flows smoothly through the slit to both the rim and boss.

  When the pulley body manufactured according to claim 3 or 4 is used as an insert part and an annular resin portion is insert-molded therebetween, the same action as in the first and second inventions can be obtained, and synergistically true. Circularity increases.

  As described above, according to the magnesium pulley of the present invention, not only the characteristics can be obtained by using magnesium or a magnesium alloy as a molding material, but also a pulley that is almost as close to a perfect circle by insert molding that inserts a bearing. With the structure in which the annular resin part is interposed between the pulley body and the bearing, the strength and roundness can be reliably maintained. Also, according to the magnesium pulley manufacturing method of the present invention, the pulley body is Because it can be manufactured to a perfect circle, no noise is generated even if it is used for ultra-high speed rotation, belt breakage can be prevented, and there is no risk of idle rotation between the pulley body and the bearing. There is an effect.

  Furthermore, if the pulley body has an annular groove, the vibration absorption (damping ability) of the magnesium material will work more effectively, preventing noise generation and preventing belt wear. It also has the effect of

  Next, regarding the embodiment of the present invention, the structure of the magnesium pulley will be described first, and then the method of manufacturing the magnesium pulley will be described.

  1 and 2 show an embodiment in a simplified drawing, and FIG. 3 shows a specific drawing. The magnesium pulley P is integrated with a magnesium alloy pulley body 1 and a steel bearing 2 with an annular resin portion 3 made of plastic interposed. And this integration is made by final injection molding, and it can take the following forms.

(1) The annular resin part 3 is injection-molded using the pulley body 1 and the bearing 2 as insert parts.
(2) The pulley body 1 is injection molded using the bearing 2 and the annular resin portion 3 as insert parts. Even in this case, it is desirable that the annular resin portion 3 is injection-molded in advance using the bearing 2 as an insert part and the bearing 2 and the annular resin portion 3 are integrated.

  For forming the pulley body 1, a die casting method or a thixo mold method is employed. The thixomold method is advantageous in that it has advantages, is safe without risk of ignition, and eliminates pollution of the global environment that occurs when taking safety measures.

  The bearing 2 is a radial bearing in which balls 7, 7,... Are interposed between the inner ring 5 and the outer ring 6 of the cage (FIG. 3), and both the rings 5, 6 are made of steel. The outer ring 6 is disconnected from the pulley body 1 by the annular resin portion 3, and further, rubber ring-shaped seal lids 8, 8 are fixedly attached to the outer ring 6 on both sides, and the inner and outer rings 5 are attached. , 6 is sealed to prevent the grease in the bearing 2 from leaking.

  The annular resin portion 3 is made of a plastic material such as PPS, nylon, or phenol. Although the annular resin portion 3 is ring-shaped, wide recesses 9 and 10 in which the bearing 2 and the pulley body 1 are fitted are provided on the inner surface and the outer surface. It is. Such uneven shape prevents sideways slipping and ensures a stable combination.

  In the case of (1), the pulley body 1 is first injection molded in a mold, and then the annular resin portion 3 is injection molded in a state where the bearing 2 is placed in a predetermined position in the same mold. On the other hand, the pulley body 1 is extremely close to a perfect circle and is accurate.

  In (2), the pulley body 1 is insert-molded with a magnesium alloy in which the bearing 2 and the annular resin portion 3 are integrated into a mold as described above. By accurately setting 2 for the mold, the pulley body 1 is molded close to a perfect circle.

  The pulley body 1 has a boss portion by forming annular grooves 13, 13 and ribs 18, 18,... At equal intervals so as to interrupt the grooves intermittently along a circle centered on the center on both side surfaces. 15 has an arm 17 between the rim portion 16 and the rim portion 16, but the arm 17 is not necessarily required. However, in the invention of the manufacturing method described later, it is essential as a narrow portion. Further, since the annular concave grooves 13 and 13 are provided, the damping ability is increased and the generation of noise is reduced, and wear due to friction with the belt is prevented. Furthermore, since the heat dissipation structure is formed by the recess 13, it works well for preventing the belt from breaking. The illustrated magnesium pulley is a belt unit type, and has a zigzag-shaped unevenness 19 formed on the outer periphery, but this may not be provided.

  When the magnesium pulley P was insert-molded with the diameter set to 70 mm, the difference in the outer diameter was 30 to 20 μm in the difference between the vertical and horizontal diameters (0 in a perfect circle). In addition, in the case of the second invention in which the annular resin portion 3 is finally insert-molded, the pulley body 1 is molded in advance with a magnesium alloy, but the difference in inner diameter is 2 to 4 μm. Further, since this roundness was maintained, it was confirmed that noise and belt breakage due to high speed rotation (7000 / min) did not occur.

  By the way, when compared with a conventional steel pulley, it had a difference of 60 μm on the inner diameter and 180 μm on the outer diameter, so noise generation and belt breakage occurred due to the same high speed rotation (7000 / min). It has been found that the magnesium pulley of the present invention is very excellent in comfort and safety.

  Next, a method for manufacturing a magnesium pulley will be described.

  The method for manufacturing the magnesium pulley will be described with respect to the case where the pulley body 1 is molded independently with respect to the magnesium pulley P of the above embodiment. Therefore, this is the case of (1) in which the pulley body 1 is molded in advance, and the case of (2) is omitted, but can be implemented in the same manner.

  The injection mold M (the same applies to die casting) has annular protrusions 23 and 24 corresponding to the annular grooves 13 and 13 of the pulley body 1 on the molds 21 and 22 on the left and right side surfaces for forming a cavity. (FIGS. 4, 5, and 6), slits 25, 25,... Are formed corresponding to the ribs 18, 18,. Further, gates 29, 29... For injecting a magnesium alloy material into the cavity are provided between the slits 25 in one mold 21. In addition, 29a is a gate mark generated in the pulley body 1.

  Regarding the shape of the cavity, the narrow portion 31 is formed between the two annular convex portions 23 and 24 facing each other, and the narrow portion 31 is opened to the wide rim portion 16 and the boss portion 15. Therefore, when the molten metal is injected from each gate 29, 29... Into the narrow portion 31, the injected molten metal collides with the annular convex portion 24 of the other mold 22 and immediately fills the narrow portion 31 to fill the rim portion 16. As a result, the direction of the fluid flowing so as to overflow the boss 15 is generated (see the arrow in FIG. 4). Therefore, in the rim portion 16 and the boss portion 15, the material flow is a diffusion flow due to the change of the translational flow (refer to the arrow). Also the material is packed tightly.

  Further, since the material is filled into the narrow portion 31 with a high pressure, the material flows into the narrow slit 25 and the material flows into the rim portion 16 and the boss portion 15 even if it passes therethrough. 18, 18,... Are densely formed. It should be noted that because of the high pressure in the narrow portion 31, even if the constriction phenomenon occurs in the vicinity of the gates 29, 29,.

  FIG. 7 shows a micrograph of the cut surface of the pulley body 1 manufactured in this way. According to this, the boss portion 15 (a) and the boss portion 15 filled with a material accompanied by a change of the “necking phenomenon” are shown. Both the rim 16 (b) have a high material density, a metallic luster color and excellent surface roughness (△△△ 6.3S or higher), and extremely high dimensional accuracy including roundness. Is shown. In actual molding experiment results, the solid phase ratio of both materials is about 30% to 38%, and this numerical value is difficult in ordinary metal material molding including die casting. Next, FIG. 8 showing a product inspection table for measuring roundness together with product drawings will be described.

  The dimension value of the product drawing of this product inspection table shows a representative value in many corresponding products (molded products). As shown in this document, on the inner diameter side, the average is 2 μm and the maximum is 5 μm, which is the same as the same structure made of mass-produced synthetic resin and the same size pulley as the same structure made of mass-produced die cast. Even when compared with the roundness of a size pulley of 30 μm, there is an extreme difference. Furthermore, even when compared with the roundness of 10 μm to 15 μm of a pulley having the same structure and the same size as the machined product, there is a great difference.

  As for the size of the product specification of the pulley main body 1 shown in FIG. 8, the thickness is 20 ± 0.3, and the five products (1) to (5) have roundness (crossing diameter) of a, b, c. Value as difference). a shows the outer diameter position on the gate side (see arrow), and b shows the opposite outer diameter position on the EP side (see arrow). Further, c indicates a location 2 mm away from the gate side surface in the thickness direction and a location 7 mm away from the opposite EP side surface.

  As mentioned above, due to high dimensional accuracy including roundness and high uniformity of material density, it always occurs in pulleys in use (long-time continuous rotation 7,000 rpm, short-time high-speed rotation 25,000 rpm). Pulley damage due to noise and resonance due to vibration and belt friction / breakage were reduced by more than 45%.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a magnesium pulley showing a part of an embodiment according to the present invention. It is sectional drawing of the AA arrow of FIG. It is sectional drawing of the pulley made from magnesium which shows a bearing part concretely corresponding to the same figure. It is sectional drawing explaining the manufacturing method of the pulley made from magnesium in the metal mold | die of one Embodiment concerning this invention. It is sectional drawing of the BB line arrow of FIG. It is a side view of the pulley main body shape | molded with the metal mold | die. It is a structure | tissue chart which shows the torn surface of a boss | hub part (I figure) and a rim | limb part (B figure) as a microscope picture about the pulley main body shape | molded with the metal mold | die. It is a roundness measurement display figure which showed the result which measured roundness about five pulley main bodies of (1)-(5) shape | molded with the metal mold | die with the product drawing which shows the measurement position.

Explanation of symbols

P Magnesium pulley M Mold 1 Pulley body 2 Bearing 3 Annular resin part 13 Annular groove 15 Boss part 16 Rim part 18 Rib 21, 22 Side molds 23, 24 Annular convex part 25 Slit 29 Gate 31 Narrow part

Claims (5)

  In a pulley with a bearing structure in which a bearing is assembled integrally, the pulley body is made of magnesium or a magnesium alloy, an annular resin part made of plastic is interposed between the pulley body and the bearing, and the pulley body and the bearing are used as insert parts. Magnesium pulley characterized by insert molding the annular resin part.   In a pulley with a bearing structure in which the bearing is assembled integrally, the pulley body is made of magnesium or a magnesium alloy, and an annular resin portion made of plastic is interposed between the pulley body and the bearing, and the combination of the bearing and the annular resin portion is combined. Magnesium pulley characterized by insert molding the pulley body as an insert part.   In manufacturing a pulley with a bearing structure in which a bearing is integrated, the pulley body is formed by die casting or injection molding with magnesium or a magnesium alloy, and on both sides of the pulley body, a rim portion as a belt joining side and a bearing outer ring side. An annular convex portion corresponding to the annular concave groove is formed on the mold on both side surfaces so that a circular annular concave groove centering on the center of the pulley is formed between each boss portion and one or Gates that open toward both annular protrusions are formed at equal intervals along the circle on both annular protrusions, and a metal material that is ejected from the gate with a constriction phenomenon is formed between the annular protrusions. A method for producing a magnesium pulley, characterized in that it is changed from a narrow portion to a relatively wide rim portion and a boss portion and flows as a diffuse flow.   Slits corresponding to the ribs are formed at equal intervals in the annular groove of the mold so that the ribs are formed at equal intervals in the circular direction in the annular groove of the pulley body, and the gate is formed between the adjacent slits. 2. The method for producing a magnesium pulley according to claim 1, wherein the pulley is provided at the center of the pulley. A method for manufacturing a magnesium pulley, comprising: using the pulley main body and the bearing manufactured according to claim 3 or 4 as an insert component, and insert-molding an annular resin portion therebetween.

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