Double flanged pulley

Abstract

To provide a double flanged pulley in which welding burrs do not erupt even when a pulley body and a flange body are joined by ultrasonic welding and a joining strength between the pulley body and the flange body can be increased.SOLUTION: An inner diameter part 6 provided in a radially inner part RI of a flange body 3 includes: a first outer cylindrical surface 6A facing an inner cylindrical surface B of a resin part 2A; and a second outer cylindrical surface 6B that tapers radially inward RI from an end part D of the first outer cylindrical surface 6A and faces an inner cylindrical surface C of a core 2B. A first space S1 formed by a first gap G1 between an annular connecting surface 6C connecting the outer cylindrical surfaces 6A, 6B and an end face E of the core 2B, and a second gap G2 between the second outer cylindrical surface 6B and the inner cylindrical surface B of the core 2B, and a second space S2 formed by a third gap G3 between the second outer cylindrical surface 6B and the inner cylindrical surface C of the core 2B serve as resin pools for molten resin when a pulley body 2 and the flange body 3 are joined by ultrasonic welding.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a double flanged pulley that meshes with a toothed belt. [Background technology]

[0002] The toothed pulley that meshes with the toothed belt is often a double-flanged pulley that has flanges on both sides in the width direction to prevent the toothed belt from coming off (for example,

[0002] of Patent Document 1).

[0003] When a toothed pulley with double flanges is integrally molded using a synthetic resin material in an injection mold, the flanges get caught in the mold, making it impossible to remove the molded toothed pulley in the axial direction from the mold. Therefore, to enable removal in the axial direction, toothed pulleys with double flanges are molded using separate injection molds: a pulley body with one flange and a flange body with the other flange (see, for example, Patent Document 1

[0003] ). Ultrasonic welding is used to join the molded pulley body and flange body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-96500 A Summary of the Invention [Problem to be solved by the invention]

[0005] When joining the pulley body and the flange body by ultrasonic welding, one problem is the formation of welding burrs from the joint (see, for example,

[0004] of Patent Document 1). The presence of welding burrs can lead to problems such as making it impossible to assemble parts, or the burrs becoming trapped between parts and causing malfunctions. Therefore, the welding burrs must be removed, which increases manufacturing costs. Furthermore, the joining strength between the pulley body and the flange body must be increased to prevent the toothed belt from coming off.

[0006] The present invention aims to provide a double-flanged pulley that can increase the joining strength between a pulley body having one flange and a flange body having the other flange by ultrasonic welding without generating welding burrs. [Means for solving the problem]

[0007] The double-flanged pulley of the present invention comprises a pulley body made of synthetic resin and a flange body made of synthetic resin joined to the pulley body in a concave-convex fit. The pulley body has a resin portion including teeth and a cylindrical core. The resin portion has a first flange protruding outward in a radial direction perpendicular to the rotation axis at a first axial end portion parallel to the rotation axis, and a cylindrical mating protrusion protruding in the axial direction at a second axial end portion. The flange body has a second flange protruding outward in the radial direction, a cylindrical mating recess recessed in the axial direction that fits with the mating protrusion, and a cylindrical inner diameter portion located radially inward of the mating recess.

[0008] The inner diameter portion has a first outer cylindrical surface facing the inner cylindrical surface of the resin portion that is connected to the inner cylindrical surface of the fitting protrusion, and a second outer cylindrical surface that tapers radially inward from the end of the first outer cylindrical surface on the first axial end side and faces the inner cylindrical surface of the core bar or the inner cylindrical surface of the resin portion that covers the second axial end side of the core bar. The double-flanged pulley has a first gap between an annular connecting surface connecting the first outer cylindrical surface and the second outer cylindrical surface and the end face of the core bar on the second axial end side or the end face of the resin portion covering the end face of the core bar, a first space formed by a second gap between the second outer cylindrical surface and the inner cylindrical surface of the resin portion, and a second space formed by a third gap between the second outer cylindrical surface and the inner cylindrical surface of the core bar or the inner cylindrical surface of the resin portion covering the second axial end side of the core bar, which serve as resin reservoirs for molten resin when the pulley body and the flange body are joined by ultrasonic welding.

[0009] In the double-flanged pulley according to the present invention, the first space and the second space serve as resin reservoirs for molten resin when the pulley body and the flange body are joined by ultrasonic welding. Therefore, the molten resin can be stored in the first space or the first and second spaces, which are the resin reservoirs, so that molten burrs do not erupt from the joint between the pulley body and the flange body. When the solidified portion of the molten resin advances into the first space and extends to the inner cylindrical surface of the resin portion connected to the inner cylindrical surface of the fitting protrusion and the second outer cylindrical surface of the inner diameter portion, the joint strength between the pulley body and the flange body can be increased.

[0010] In a structure in which the second axial end side of the core is not covered with the resin portion, when the molten resin abuts against the end face of the second axial end side of the core, changes direction, and enters the second space from the first space, the molten resin contacts the annular end face of the core and the inner cylindrical surface of the core. Because the core is made of metal, heat is removed from the molten resin in contact with the core, making it easier for the molten resin to cool and solidify. This effectively suppresses the molten resin from spilling out of the joint. [Effects of the Invention]

[0011] As described above, according to the present invention, a double-flanged pulley can be obtained in which no welding burrs are produced when a pulley body with one flange and a flange body with the other flange are joined by ultrasonic welding, and the joining strength between the pulley body and the flange body can be increased. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view of a double-flanged pulley according to an embodiment of the present invention; [Figure 2] FIG. 2 is a vertical cross-sectional view of the double flanged pulley of FIG. 1. [Figure 3] FIG. 10 is a vertical cross-sectional view showing a modified example of a double-flanged pulley having a double core metal. [Figure 4] FIG. 2 is an enlarged longitudinal cross-sectional view of a main part showing an example of a solidified portion of molten resin. [Figure 5] FIG. 10 is an enlarged longitudinal cross-sectional view of a main part showing another example of a solidified portion of molten resin. [Figure 6] FIG. 10 is a vertical cross-sectional view showing a modified example of the resin portion of the pulley body. [Figure 7] 10A and 10B are longitudinal cross-sectional views showing modified examples of the core metal and resin portion of the pulley body. [Figure 8] 10A and 10B are explanatory views showing an example of a process for joining a pulley body and a flange body using an ultrasonic welding machine. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] In this specification, the direction parallel to the direction of the rotation axis (see symbol O in Figure 2) of the double-flanged pulley 1 is referred to as the "axial direction" (see arrow J in Figure 2), and the direction perpendicular to the direction of the rotation axis is referred to as the "radial direction" (see arrow R in Figure 2).

[0015] In this specification, the radial direction approaching the rotation axis is referred to as the "radially inward direction" (see, for example, arrow RI in Figure 2), and the radial direction moving away from the rotation central axis is referred to as the "radially outward direction" (see, for example, arrow RO in Figure 2).

[0016] 2, for example, the end of the resin part 2A on the first flange F1 side in the axial direction J is referred to as the first end J1, and the end of the resin part 2A on the fitting protrusion 4 side in the axial direction J is referred to as the second end J2. In addition, in the double-flanged pulley 1 and its component parts, the first flange F1 side is referred to as the first end J1 side in the axial direction J, and the second flange F2 side is referred to as the second end J2 side in the axial direction J.

[0017] [Double flanged pulley] 1 and 2, a double-flanged pulley 1 according to an embodiment of the present invention is used, for example, in a power transmission mechanism of an electric power steering device. The double-flanged pulley 1 includes a pulley body 2 made of synthetic resin, and a flange body 3 made of synthetic resin joined to the pulley body 2 in a concave-convex fit.

[0018] The pulley body 2 has a resin part 2A including teeth T, and a cylindrical core 2B. The teeth T on the outer peripheral surface of the pulley body 2 are helical teeth, and the teeth T mesh with the teeth of a toothed belt (not shown).

[0019] In the double flanged pulley 1 according to the embodiment of the present invention, the resin portion 2A including the teeth T of the pulley body 2 and the flange body 3 are made of synthetic resin, so the double flanged pulley 1 can be made lightweight.

[0020] [Core] The core metal 2B has a bottom plate K at the end on the first end J1 side in the axial direction J. The bottom plate K has a plurality of mounting holes (in this embodiment, three circular holes equally divided in the circumferential direction) H in the axial direction J. The pulley 1 with both flanges can be easily and surely fixed to the member to which the pulley 1 with both flanges is attached by bolts passed through the mounting holes H of the core metal 2B.

[0021] The inner cylindrical surface I on the first end J1 side in the axial direction J of the core metal 2B is exposed. The inner diameter M of the core metal 2B is smaller than the inner diameter N of the flange body 3 (M < N), and the inner cylindrical surface I is used for the radial R positioning of the pulley 1 with both flanges with respect to the nut of the ball screw of the power transmission mechanism of the electric power steering device (not shown). The core metal 2B is made by pressing a cold-rolled steel sheet, a hot-rolled steel sheet, a high-tensile steel sheet, etc. Note that the inner cylindrical surface I of the core metal 2B may be covered with resin, and in that case, the inner diameter of the resin covering the inner cylindrical surface I of the core metal 2B is made smaller than the inner diameter N of the flange body 3.

[0022] The core metal integrated with the resin part 2A may have a double structure consisting of a thin core metal 2B and a core metal 2C as shown in FIG. 3. In that case, the bottom plate K is provided at the end on the first end J1 side in the axial direction J of the core metal 2C on the radially inner side RI. Also, the inner diameter M of the core metal 2C is smaller than the inner diameter N of the flange body 3 (M < N), and the inner cylindrical surface I of the core metal 2C is used for the radial R positioning of the pulley 1 with both flanges with respect to the nut of the ball screw of the power transmission mechanism of the electric power steering device (not shown). The core metal 2C is made by pressing a cold-rolled steel sheet, a hot-rolled steel sheet, a high-tensile steel sheet, etc. in the same manner as the core metal 2B. Note that the inner cylindrical surface I of the core metal 2C may be covered with resin, and in that case, the inner diameter of the resin covering the inner cylindrical surface I of the core metal 2C is made smaller than the inner diameter N of the flange body 3.

[0023] The cylindrical core metal 2B in FIGS. 2 and 3 is located on the radially inner side RI of the teeth T and has a sufficiently long length in the axial direction J, so it can meet the required accuracy of the synthetic resin teeth T with which the toothed belt meshes.

[0024] [Resin part, and flange body] The material of the resin portion 2A and the flange body 3 is, for example, a thermoplastic resin material such as PBT, PA6, PA66, PA46, PPS, or PEEK, and among these, a preferred embodiment is one in which PPS, which has excellent heat resistance, mechanical properties, flame retardancy, and dimensional stability, is blended with several tens of weight percent of glass fiber as a reinforcing material.

[0025] The resin part 2A has a first flange F1 at a first end J1 in the axial direction J that protrudes radially outward RO, and a cylindrical mating protrusion 4 at a second end J2 in the axial direction J that protrudes radially inward RI from the tooth surface of the tooth T with which the toothed belt engages.

[0026] The flange body 3 is located on the second end J2 side in the axial direction J and has a second flange F2 that protrudes radially outward RO, and has a cylindrical mating recess 5 that is recessed in the axial direction J and fits into the mating protrusion 4, and a cylindrical inner diameter portion 6 that is located radially inward RI of the mating recess 5.

[0027] [Inner diameter] As shown in Figure 4, the inner diameter portion 6 has a first outer cylindrical surface 6A that faces the inner cylindrical surface B of the resin portion 2A that is connected to the inner cylindrical surface 4A of the fitting convex portion 4, and a second outer cylindrical surface 6B that narrows radially inward RI from an end D on the first end J1 side of the axial direction J of the first outer cylindrical surface 6A and faces the inner cylindrical surface C of the core bar 2B.

[0028] A gap G0 exists between the first outer cylindrical surface 6A and the inner cylindrical surface 4A and between the first outer cylindrical surface 6A and the inner cylindrical surface B. A first gap G1 exists between an annular connecting surface 6C connecting the first outer cylindrical surface 6A and the second outer cylindrical surface 6B and an end face E of the core 2B on the second end J2 side in the axial direction J. A second gap G2 exists between the second outer cylindrical surface 6B and the inner cylindrical surface B of the resin portion 2A, and a third gap G3 exists between the second outer cylindrical surface 6B and the inner cylindrical surface C of the core 2B.

[0029] Here, the size of the first gap G1 is set to G1≧G0, and is adjusted according to the amount of molten resin when joining the pulley body 2 and the flange body 3 by ultrasonic welding, and the required specifications for the joining strength between the pulley body 2 and the flange body 3, etc.

[0030] [Resin pool, solidified part of molten resin] In the double-flanged pulley 1 according to the embodiment of the present invention, the first space S1 formed by the first gap G1 and the second gap G2, and the second space S2 formed by the third gap G3 are resin reservoirs for molten resin when the pulley body 2 and the flange body 3 are joined by ultrasonic welding.

[0031] When the pulley body 2 and the flange body 3 are joined using an ultrasonic welding machine, the molten resin passes over the end D on the first end J1 side in the axial direction J of the first outer cylindrical surface 6A of the inner diameter portion 6 and enters the first space S1. Referring to the examples in Figures 4 and 5, the molten resin abuts against the annular end face E on the second end J2 side in the axial direction J of the core 2B, changes direction radially inward RI, and then enters the second space S2.

[0032] For example, in Fig. 4, solidified portion A of the molten resin formed when the pulley body 2 and the flange body 3 were joined by ultrasonic welding penetrates from the first space S1 to a position slightly inside the second space S2. In the example of Fig. 5, which shows a case where the amount of molten resin is greater than that in Fig. 4, solidified portion A of the molten resin penetrates further into the second space S2.

[0033] [Modification of the resin part of the pulley body] As shown in FIG. 6, a core metal receiving portion U for receiving an annular end face E of the core metal 2B may be provided on the resin portion 2A of the pulley body, thereby increasing the effect of preventing the core metal 2B from coming off.

[0034] As shown in FIG. 7, the resin portion 2A of the pulley body may be provided with a covering portion V that covers the second end J2 of the core 2B in the axial direction J, thereby further enhancing the effect of retaining the core 2B. In the example of FIG. 7, the first gap G1 is a gap between the annular connecting surface 6C and the end face F of the covering portion V, which is a resin portion that covers the end face E of the core 2B. The third gap G3 that forms the second space S2 is a gap between the second outer cylindrical surface 6B and the inner cylindrical surface B2 of the covering portion V. As shown in FIG. 7, in a preferred embodiment, the inner cylindrical surface C2 of the core 2B on the second end J2 in the axial direction J side is expanded in diameter so that the inner cylindrical surface B2 of the covering portion V and the inner cylindrical surface C of the core 2B are flush with each other.

[0035] When the structure has a core support portion U that supports the annular end face E of the core 2B as shown in Figure 6, or a covering portion V that covers the second end J2 side of the core 2B in the axial direction J as shown in Figure 7, in addition to the effect of preventing the core 2B from coming loose as described above, the following effect is also achieved.

[0036] That is, to further improve the accuracy of the belt transfer surface of the double-flanged pulley 1, if the core 2B is positioned radially inward RI over a wider range of the axial direction J of the teeth T with which the toothed belt engages, the annular end face E of the core 2B must be brought closer to the second flange F2. In the structure of FIG. 4, bringing the end face E closer to the second flange F2 shortens the axial direction J of the gap G0, thereby shortening the distance over which the ultrasonic welding function is exerted. In contrast, in the structure of FIG. 6 or FIG. 7, if the end face E is brought closer to the second flange F2, the molten resin contacts the metal core 2B in the first space S1 in the structure of FIG. 6, but does not contact the metal core 2B in the structure of FIG. 7, so heat loss from the molten resin in the first space S1 is reduced. Therefore, in the structure of FIG. 6 or FIG. 7, the molten resin flows into the first space S1 while remaining at a high temperature, thereby increasing the joining strength achieved by welding in the first space S1.

[0037] [Example of the process of joining a pulley body and a flange body using an ultrasonic welder] See Figure 8. Before the flange body 3 is joined, the fitting protrusion 4 of the pulley body 2 has a circular corner L on the radially inward side RI of its tip. The pulley body 2 having this shape is installed with the first flange F1 facing downward, the fitting protrusion 4 facing upward, and the axial direction J aligned vertically.

[0038] Next, the flange body 3 is placed on the pulley body 2 so that the mating recess 5 is mated with the mating protrusion 4 of the pulley body 2. The circular corner L of the mating protrusion 4 of the pulley body 2 comes into contact with the inclined surface W of the truncated cone side of the mating recess 5 of the flange body 3.

[0039] Next, the horn Q of the ultrasonic welding machine P presses the flange body 3 downward in the direction of the arrow X, while transmitting ultrasonic vibrations from the horn Q to the inside of the flange body 3 and the inside of the pulley body 2, generating frictional heat and melting mainly the circular corner L of the pulley body 2 ((a) to (b) of Figure 8).

[0040] Since the corners L of the radially inner RI of the pulley body 2 are mainly melted, the molten resin tends to flow downward from the ends of the radially inner RI of the side inclined surface W of the truncated cone, as shown in Figure 8(b), and the molten resin enters, for example, the first space S1 and the second space S2, which are resin reservoirs. The molten resin is cooled and solidified, becoming a solidified portion A of the molten resin.

[0041] [Action and effect] In the double-flanged pulley 1 according to the embodiment of the present invention, the first space S1 and the second space S2 serve as resin reservoirs for molten resin when the pulley body 2 and the flange body 3 are joined by ultrasonic welding. Therefore, the molten resin can be stored in the resin reservoirs, the first space S1 or the first space S1 and the second space S2, so no molten burrs are ejected from the joint between the pulley body 2 and the flange body 3. When the solidified portion A of the molten resin advances into the first space S1 and extends to the inner cylindrical surface B of the resin portion 2A connected to the inner cylindrical surface 4A of the fitting protrusion 4 and the second outer cylindrical surface 6B of the inner diameter portion 6, the joint strength between the pulley body 2 and the flange body 3 can be increased.

[0042] In a structure in which the second end J2 side of the core 2B in the axial direction J is not covered with the resin portion 2A (a structure without the covering portion V in FIG. 7), when the molten resin contacts the end face E of the core 2B on the second end J2 side in the axial direction J and changes direction, entering the second space S2 from the first space S1, the molten resin contacts the annular end face E of the core 2B and the inner cylindrical surface C of the core 2B. Because the core 2B is made of metal, heat is removed from the molten resin in contact with the core 2B, making it easier for the molten resin to cool and solidify. This effectively suppresses the molten resin from spilling out of the joint.

[0043] The above description of the embodiments is given by way of example only and is not intended to be limiting, and various improvements and modifications can be made without departing from the scope of the present invention. [Explanation of symbols]

[0044] 1. Pulley with double flanges 2. Pulley body 2A Resin part 2B,2C Core metal 3 Flange body 4 Fitting protrusion 4A Inner cylindrical surface 5 Fitting recess 6 Inner diameter portion 6A First outer cylindrical surface 6B Second outer cylindrical surface 6C Annular connecting surface A Solidified part of molten resin B, B2, C, C2 Inner cylindrical surface D End E,F End face F1 First flange F2 Second flange G0, G1, G2, G3 Gap H Mounting hole I Inner cylindrical surface J Axial direction J1 1st end J2 2nd end K Bottom plate L Corner M: Inner diameter of core metal N: Inner diameter of flange body O Rotating shaft P Ultrasonic welding machine Q Horn R Radial direction RI radially inward RO radially outward S1 1st space S2 2nd space T tooth U core bar receiving part V Covered part W Inclined surface X pressing direction

Claims

[Claim 1] A double-flanged pulley comprising a pulley body made of synthetic resin and a flange body made of synthetic resin joined to the pulley body in a concave-convex fit state, The pulley body has a resin portion including teeth and a cylindrical core metal, The resin portion is a first flange protruding outward in a radial direction perpendicular to the rotation axis at a first end in an axial direction parallel to the rotation axis; a cylindrical fitting protrusion protruding in the axial direction at a second end in the axial direction; The flange body is a second flange protruding radially outward; a cylindrical fitting recess recessed in the axial direction and fitted to the fitting protrusion; and a cylindrical inner diameter portion located radially inward of the fitting recess, The inner diameter portion is a first outer cylindrical surface facing the inner cylindrical surface of the resin portion connected to the inner cylindrical surface of the fitting protrusion, and a second outer cylindrical surface that reduces in diameter radially inward from an end of the first outer cylindrical surface on the first axial end side and faces the inner cylindrical surface of the core metal or the inner cylindrical surface of the resin portion covering the second axial end side of the core metal, a first gap between an annular connecting surface connecting the first outer cylindrical surface and the second outer cylindrical surface and an end face of the core metal on the second end side in the axial direction or an end face of the resin portion covering the end face of the core metal, and a second gap between the second outer cylindrical surface and an inner cylindrical surface of the resin portion; and a second space formed by a third gap between the second outer cylindrical surface and an inner cylindrical surface of the core or an inner cylindrical surface of the resin portion covering a second end side of the core in the axial direction, A resin pool of molten resin is formed when the pulley body and the flange body are joined by ultrasonic welding. Double flanged pulley.

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