Toothed pulley and manufacturing method of the same

Abstract

To provide a toothed pulley that is composed of a core and a resin portion, and that can simultaneously secure the dimensional accuracy of a tooth portion and the bonding strength of the resin portion to the core while keeping productivity.SOLUTION: A toothed pulley 1 includes a bottomed cylindrical core 11, and a resin portion 12 forming an outer part of the core 11 by insert molding and including a tooth portion 121. The core 11 is provided with multiple pinhole-shaped recesses 113 dispersed on an outer peripheral surface opposite the tooth portion 121, each recess 113 having a depth of from 0.2 mm to half of a thickness of the core 11 and an average diameter of 0.2 mm or more and 3.5 mm or less. A part of the resin portion 12 is solidified, penetrating into the multiple of recesses 113.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a toothed pulley used for electric power steering of an automobile and a method for manufacturing the same. [Background technology]

[0002] As the shift to electrification in automobiles accelerates, the adoption of electric power steering (EPS) devices is expanding. In this electric power steering device, as shown in, for example, Figures 1 and 2 of Patent Document 4, a belt transmission mechanism (30) is used as a reduction gear for transmitting the driving force of the electric motor (18) to the steering mechanism (12). The belt transmission mechanism (30) is composed of a drive-side toothed pulley (31) connected to the motor shaft (18a) of the electric motor (18), a driven-side toothed pulley (32) connected to a ball nut (42) that engages with the rack shaft (13) in the steering mechanism, and a toothed belt (33) wound around both pulleys.

[0003] In the belt transmission mechanism, in order to further reduce the weight, toothed pulleys (particularly the driven side) are increasingly being made of resin (replaced with resin pulleys).

[0004] In this regard, in the belt transmission mechanism (reduction gear) within the EPS device, as shown in Figures 2 and 6 of Patent Document 4, the small diameter drive pulley (31) may be cylindrical since it is simply fixed to the shaft (18a) of the electric motor, but the large diameter driven pulley (32) is fixed (bolted) in a manner such that it covers and abuts against the ball nut (42) from one end side (the right side in Figure 2), so it may be configured as a bottomed cylinder having a bottom. For this reason, when making resin for toothed pulleys for the belt transmission mechanism in EPS devices, the target is the driven toothed pulley (driven pulley), which offers greater weight reduction benefits.

[0005] (Basic structure of resin pulleys) Typically, when a closed-end cylindrical toothed pulley (driven pulley) is made into a resin (a resin pulley), the outer part including the teeth is made into a resin part made of synthetic resin so as to meet the required specifications for strength and dimensional accuracy, and the inner part is reinforced with a closed-end cylindrical core bar (metal) to combine the two into a single structure.

[0006] (About the manufacturing method of resin pulleys) The manufacturing method of such a toothed pulley (plastic pulley) is generally a method (so-called insert molding) in which a pre-prepared core bar is placed in a mold as an insert member and then injection molded or compression molded to form a resin part integrally with the core bar in order to increase strength and dimensional accuracy.

[0007] (Restrictions on plastic pulleys) When a toothed pulley is formed by a core bar and a resin part, it is necessary to prevent the resin part from shifting (moving relative to) the core bar in the circumferential and axial directions. In other words, it is necessary to properly provide a means for preventing the resin part from rotating in the circumferential direction and a means for preventing the resin part from coming off in the axial direction with respect to the core bar, and to ensure the bonding strength of the resin part to the core bar.

[0008] (Design method to ensure the bonding strength of the resin part to the core metal) In order to ensure the bonding strength of the resin part to the core bar, it is usually necessary to design a toothed pulley so that the outer surface of the core bar has a portion extending in a direction intersecting the circumferential direction [circumferential anti-rotation means (hereinafter, anti-rotation)], and a portion extending in a direction intersecting the axial direction [axial anti-slip means (hereinafter, anti-slip)], i.e., a configuration in which the outer surface of the core bar has convex and / or concave portions.

[0009] (Further constraints) On the other hand, there is an increasing demand for lighter, quieter and less costly belt transmission mechanisms within EPS devices, and when making a toothed pulley out of resin, it is necessary to ensure that the core metal plate thickness and the resin part (especially the tooth groove part, which is the thinnest part of the tooth part) are both thin (for example, both are as thin as about 2 mm), while still ensuring the bonding strength of the resin part to the core metal, and that the dimensional precision of the teeth part is ensured (to ensure sound vibration performance, the outer diameter dimensions of the teeth part, etc. must be kept within the dimensional tolerances, and good meshing between the toothed pulley and toothed belt must be maintained).

[0010] That is, when manufacturing toothed pulleys (plastic pulleys) for EPS devices by insert molding, there are special circumstances that must be addressed: (1) the shape of the outer circumferential surface facing the teeth of the core (a configuration having convex and / or concave portions) must not adversely affect the dimensional accuracy of the teeth; (2) the bonding strength of the resin portion to the core must be ensured even in a usage environment in which significant temperature changes (for example, of the order of 100°C) occur; and (3) a special design that would increase the manufacturing effort (separate process) and lead to increased costs in order to solve these problems must be avoided.

[0011] In this regard, Patent Documents 1 to 3 disclose resin pulleys in which the joining strength of the resin portion to the core metal is ensured in order to address the above-mentioned issues. The contents of Patent Documents 1 to 3 are summarized in Table 1.

[0012] [Table 1] [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Patent Publication No. 2022-109432 [Patent Document 2] JP 2011-214680 A [Patent Document 3] Japanese Utility Model Application Publication No. 2-107862 [Patent Document 4] JP 2020-044854 A Summary of the Invention [Problem to be solved by the invention]

[0014] Patent Document 1 discloses a toothed pulley (Figure 8 of Patent Document 1) that can ensure the bonding strength of the resin part to the core wire, ensure the accuracy of the teeth part, and reduce manufacturing costs by providing a polygonal convex part (outward flange D) when viewed from the axial direction at one end of the outer surface of the core wire (Figure 10 of Patent Document 1) that faces the teeth part.

[0015] However, according to the inventors' verification, although the configuration of Patent Document 1 is believed to ensure the bonding strength of the resin portion to the core, since a convex portion is provided only on one end of the outer circumferential surface facing the teeth of the core, the flow of the molten resin changes significantly at the convex portion during insert molding (particularly injection molding) (i.e., the flow path thickness is locally reduced, causing a local increase in internal pressure). Therefore, after the resin solidifies, there is a concern that the outer diameter (tooth tip diameter) of the teeth facing the convex portion will increase significantly, adversely affecting the dimensional accuracy of the teeth.

[0016] Furthermore, Patent Documents 2 and 3 disclose a configuration in which extremely small recesses or depressions, or gear-shaped projections and recesses are formed on the entire outer circumferential surface of a core bar.

[0017] However, with the solution in Patent Document 2 (very small recesses or depressions), when used in an environment where significant temperature changes (for example, of the order of 100°C) occur, the thermal expansion of the resin part will be significantly larger than that of the core metal (for example, about 0.1 mm in diameter, about 0.05 mm on one side in the radial direction), and with a recess depth of up to a few hundredths of a millimeter, there is a concern that the anchor effect of the recess will be completely lost and the bonding strength of the resin part to the core metal will not be ensured. Also, since the processing of the recesses (depressions) is a separate process from the main (pressing) process of the core metal, there is a concern that the manufacturing work will increase.

[0018] Furthermore, when the solution in Patent Document 3 (gear-shaped uneven portion) is applied to a toothed pulley, if the height of the uneven portion is large (for example, 5 mm), there is a concern that the surface of the tooth portion facing the recessed portion may be depressed (become a depression) even if the uneven portion is arranged at equal intervals in the circumferential direction. Also, if the uneven portion is formed into a gear shape as in Figure 1 described in Patent Document 3, it can prevent rotation but there is a concern that it cannot prevent slipping out.

[0019] As described above, the configurations of Patent Documents 1 to 3 cannot fully solve the above problems (special circumstances).

[0020] As a result of examining conventional toothed pulleys for EPS devices (Patent Documents 1 to 3), the present inventors discovered the following improved points 1 to 3.

[0021] (Improvement point 1) When the tooth portion (particularly the tooth groove portion, which is the thinnest portion) is designed to be thin (for example, to a thickness of about 2 mm), providing a convex (diametrically outwardly protruding) anti-rotation and anti-removal device locally on the outer peripheral surface of the core bar facing the tooth portion will locally change the flow of the molten resin. In other words, compared to a configuration in which no convex portions are provided locally, the internal pressure of the molten resin will locally increase in the cavity (flow path) portion facing the tooth portion during insert molding (particularly injection molding) due to a locally reduced flow path thickness (radial dimension of the cavity) of the molten resin flowing in a molten state.

[0022] Therefore, after the resin solidifies, the outer diameter (tooth tip diameter) of the tooth portion will increase locally (for example, by approximately 0.05 mm), which may make it impossible to ensure the dimensional accuracy of the tooth portion (keeping the outer diameter dimension of the tooth portion within the dimensional tolerance and maintaining good meshing between the toothed pulley and the toothed belt). If a toothed pulley having a tooth tip diameter outside the specified dimensional tolerance (for example, ±0.05 mm from the reference dimension) is used in the belt transmission mechanism (reduction gear) of an EPS device, it is believed that this will cause problems in the meshing between the toothed pulley and the toothed belt, and ultimately in ensuring quietness (noise and vibration performance).

[0023] (Improvement point 2) If a significant temperature change (for example, of about 100°C) occurs in the usage environment, the greater the difference in the linear expansion coefficients between the materials of the resin part and the core wire, the more significantly the thermal expansion of the resin part will be greater than that of the core wire (for example, by about 0.1 mm in diameter), which may result in the bonding strength of the resin part to the core wire not being secured. Therefore, it is considered necessary to ensure the bonding strength of the resin portion to the core metal even in an operating environment where significant temperature changes occur.

[0024] (Improvement point 3) There is a risk of increased manufacturing costs in implementing the above improvement points 1 and 2. It is considered desirable to avoid special designs that would lead to increased manufacturing effort (separate processes) and maintain productivity.

[0025] Based on the above technical improvement points 1 to 3, the present invention has an objective of providing a toothed pulley composed of a core wire and a resin part, which can ensure both the dimensional accuracy of the teeth part and the bonding strength of the resin part to the core wire while maintaining productivity. [Means for solving the problem]

[0026] The present invention includes a cylindrical core bar with a bottom, a resin portion including a tooth portion that is formed by insert molding on an outer side of the core metal, The core has a number of pinhole-like recesses formed in a dispersed manner on an outer peripheral surface facing the teeth, the pinhole-like recesses having a depth of 0.2 mm or more and a half or less of the thickness of the core and an average width, which is an average length along a direction perpendicular to the depth direction, of 0.2 mm or more and 3.5 mm or less, The toothed pulley is characterized in that a portion of the resin portion is solidified in a state where it fills the many recesses.

[0027] According to the above configuration, in a toothed pulley composed of a core and a resin portion, a large number of pinhole-shaped recesses that prevent the resin portion from rotating or coming loose relative to the core are formed in a dispersed manner on the outer peripheral surface facing the teeth of the core, and are not formed locally (see Figure 3). Therefore, even if the thickness of the tooth portion (especially the groove portion of the tooth portion) is designed to be thin (for example, as thin as about 2 mm), when insert molding (especially injection molding) is performed using the core wire as an insert member, the flow of molten resin in the cavity portion of the mold facing the tooth portion (especially the flow path thickness and internal pressure) is kept unchanged locally, making it easier to ensure the dimensional accuracy of the tooth portion (especially the accuracy of the tooth tip diameter). Furthermore, if the depth of the recess is less than 0.2 mm, in an operating environment where significant temperature changes (for example, of the order of 100°C) occur, the thermal expansion of the resin part will be significantly greater (for example, by about 0.1 mm in the radial direction) than that of the core wire, resulting in a poor anchor effect and in some cases making it impossible to ensure the bonding strength of the resin part to the core wire. On the other hand, if the depth of the recess exceeds half the thickness of the core bar, when the recess is formed by plastic processing (press processing), it will undergo excessively large plastic deformation, and the inner surface of the core bar facing the recess may bulge. Furthermore, if the average width (diameter) of the recesses is less than 0.2 mm, when the recesses are formed by plastic processing (press processing), the durability of the pin-shaped die member for forming the recesses may not be ensured. Also, the anchor effect of the recesses is poor, and the bonding strength of the resin part to the core metal may not be ensured. On the other hand, if the average width of the recess exceeds 3.5 mm, the outer surface of the tooth portion facing the recess may be recessed (depressed) after insert molding (particularly injection molding). Therefore, the pinhole-shaped recess has a depth of 0.2 mm or more and half the thickness of the core bar or less, and an average width, which is the average length along the direction perpendicular to the depth direction, of 0.2 mm or more and 3.5 mm or less. As a result, even if in an operating environment where significant temperature changes occur (for example, of the order of 100°C), the difference in the linear expansion coefficients between the materials of the resin part and the core wire causes the thermal expansion of the resin part to be significantly greater than that of the core wire (for example, by about 0.1 mm in diameter), the anchor effect of the recess is not lost, and the joining strength of the resin part to the core wire can be ensured. Furthermore, the formation of the pinhole-shaped recesses does not require special design that would increase the manufacturing effort (separate process), and the above-mentioned anti-rotation and anti-slip features (multiple recesses) can be formed while maintaining productivity, thereby preventing increases in manufacturing costs. That is, according to the above configuration, in a toothed pulley constituted by a core and a resin portion, it is possible to ensure both the dimensional accuracy of the teeth portion and the bonding strength of the resin portion to the core while maintaining productivity.

[0028] Moreover, in the toothed pulley of the present invention, the recess may have the depth of 0.2 mm or more and 1 / 3 or less of the thickness of the core bar, and the average width of 0.5 mm or more and 3 mm or less.

[0029] According to the above configuration, even if, in an operating environment where significant temperature changes (for example, of the order of 100°C) occur, the difference in the linear expansion coefficients between the materials of the resin part and the core wire causes the thermal expansion of the resin part to be significantly greater than that of the core wire (for example, by about 0.1 mm in diameter), the anchor effect of the recess is not lost, and the dimensional accuracy of the tooth part and the bonding strength of the resin part to the core wire can be ensured at a higher level.

[0030] The present invention also provides a method for manufacturing a toothed pulley including a cylindrical core bar with a bottom and a resin part including a tooth part that is formed by insert molding on an outer side of the core bar, the method comprising the steps of: a first pressing step of punching the plate material into a disk shape to form a disk-shaped blank material; a second press process for forming a plate-shaped core bar precursor by forming a plurality of pinhole-shaped recesses having a predetermined depth in a dispersed manner by plastic processing on a portion of the blank material corresponding to an outer peripheral surface facing the teeth portion of the core bar; a third pressing step of forming the core bar precursor into a cylindrical core bar with a bottom by drawing; The method includes an insert molding process in which the core metal is placed in a mold as an insert member, the resin that constitutes the resin portion is filled in a molten state in the mold, and the resin is solidified in a state where it has filled the numerous recesses to form a toothed pulley.

[0031] According to the above method, a disk-shaped blank (flat plate) is plastically processed (pressed) to form a number of pinhole-like recesses of a specified depth, and then a cylindrical core bar with a bottom is formed by drawing. Therefore, a number of recesses that function to prevent rotation and slipping out can be formed relatively easily on the entire outer circumferential surface of the core bar. Furthermore, the series of press processes required for manufacturing the core bar, i.e., the first press process in which a disk-shaped blank material is formed by punching, the second press process in which a plate-shaped core bar precursor with numerous pinhole-like recesses distributed therein, and the third press process in which a bottomed cylindrical core bar is formed from the plate-shaped core bar precursor by drawing, are all carried out by simply pressing the workpieces that flow in one after another using a specified press mold (one set of upper and lower molds) (i.e., only one press process is required as a whole). Therefore, it is possible to suppress an increase in the manufacturing effort (separate steps) required for forming a large number of recesses that perform the functions of preventing rotation and slipping out. Moreover, because plastic processing does not cut the metal fiber structure as in mechanical (cutting) processing, it is possible to prevent the strength of the core bar, including the strength of the recessed portion, from decreasing compared to when the core bar is manufactured by mechanical processing. In addition, it is possible to increase the processing speed and production efficiency while reducing material loss (improving yield), so it is possible to reduce costs by minimizing mechanical processing.

[0032] The present invention provides the above-mentioned second pressing step in the manufacturing method of the toothed pulley, The recess may be formed by the plastic working so that a cross section along a direction perpendicular to a depth direction of the recess is circular.

[0033] According to the above method, it is possible to avoid stress concentration on the recesses, and it becomes relatively easy to process the recesses in the blank in the second press step. Effect of the Invention

[0034] According to the present invention (wherein a large number of predetermined recesses are formed distributed over the entire outer peripheral surface facing the teeth of the core), anti-rotation and anti-slip features are not formed locally on the outer peripheral surface facing the teeth of the core. Therefore, even if the thickness of the teeth (particularly the tooth groove portion) is designed to be thin (for example, as thin as about 2 mm), the flow of molten resin (particularly the flow path thickness and internal pressure) in the cavity (flow path) portion facing the teeth is maintained without local change during insert molding (particularly injection molding), making it easier to ensure the dimensional accuracy of the teeth (particularly the accuracy of the tooth tip diameter) (addressing problem (1)). Even in an operating environment where a significant temperature change (for example, of about 100°C) occurs and the thermal expansion of the resin portion is significantly larger than that of the core (for example, by about 0.1 mm in diameter), the bonding strength of the resin portion to the core can be ensured (addressing problem (2)). Furthermore, without the need for special design that would increase the manufacturing effort (separate process), anti-rotation and anti-slip features can be formed while maintaining productivity, thereby preventing an increase in manufacturing costs (addressing problem (3)). [Brief description of the drawings]

[0035] [Figure 1] FIG. 2 is an exploded perspective view of a ball nut and a toothed pulley (driven toothed pulley) according to the embodiment. [Diagram 2] FIG. 2 is a perspective view of a toothed pulley according to the embodiment. [Diagram 3] FIG. 2 is a cross-sectional view of a toothed pulley according to the embodiment. [Figure 4] FIG. 2 is an exploded perspective view of a core metal and a resin portion that configure the toothed pulley according to the embodiment. [Diagram 5] FIG. 2 is a perspective view of a core bar according to the embodiment. [Figure 6] FIG. 2 is a partial cross-sectional perspective view of a core bar according to the embodiment. [Figure 7]1A is an explanatory diagram of a first press step, and FIG. 1B is an explanatory diagram of a second press step. [Figure 8] 1C is an explanatory diagram of the third press process (before draw-forming) and FIG. 1C is an explanatory diagram of the third press process (after draw-forming (before trimming)). [Figure 9] FIG. 11 is a cross-sectional view of a toothed pulley according to Comparative Example 2. [Figure 10] FIG. 4 is an enlarged view of a portion A of the toothed pulley in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] (Embodiment) The toothed pulley 1 according to this embodiment is used in a belt transmission mechanism of an electric power steering device for an automobile. Specifically, the belt transmission mechanism is a reduction gear that transmits the driving force of the electric motor to the steering mechanism, and is composed of a drive-side toothed pulley (not shown) connected to the motor shaft of the electric motor, a driven-side toothed pulley 10 connected to a ball nut 20 (see FIG. 1) that engages with a rack shaft (not shown) in the steering mechanism, and a toothed belt (not shown) wound around both pulleys. The toothed pulley 1 is used as the driven-side toothed pulley 10 of this belt transmission mechanism (see FIG. 1). The opening side in the rotation axis direction (hereinafter, axial direction) of the toothed pulley 1 is defined as one end side, and the bottom side is defined as the other end side.

[0037] (Toothed pulley 1) As shown in Figures 1 to 3, the toothed pulley 1 (driven toothed pulley 10) has teeth 121 on its outer circumferential surface, and is fixed to the ball nut 20 by bolts 21 while being inserted into the ball nut 20 from the other end side. The belt wound between the driving toothed pulley and the toothed pulley 1 (driven toothed pulley 10) is a toothed belt (timing belt) having teeth on its inner circumferential surface. As a result, the rotation of the electric motor is transmitted to the ball nut 20 via the drive-side toothed pulley, the toothed belt, and the toothed pulley 1 (the driven-side toothed pulley 10).

[0038] As shown in FIG. 4, the toothed pulley 1 is composed of a core bar 11 formed in a cylindrical shape with a bottom including a bottom plate 111 forming the bottom, and a resin part 12 that forms the outer part of the core bar 11 and includes a tooth part 121.

[0039] The teeth 121 of the toothed pulley 1 mesh with the teeth of a toothed belt (timing belt) not shown. The teeth 121 are helical teeth arranged obliquely with respect to the axial direction in order to ensure quietness (sound vibration performance).

[0040] 1, toothed pulley 1 is fixed (bolted) to ball nut 20 via four bolts 21 in such a manner that it covers ball nut 20 from the other end side (the inner peripheral surface of core bar 11 engages with the outer peripheral surface of ball nut 20) and the inner bottom surface of core bar 11 abuts against the other end side surface of ball nut 20. This ensures coaxiality between toothed pulley 1 (driven toothed pulley 10) and ball nut 20.

[0041] A flange portion 122 for restricting movement of the toothed belt in the axial direction is formed on the resin portion 12 of the toothed pulley 1. The flange portion 122 protrudes radially outward over the entire circumference beyond the tooth tips of the toothed portion 121. The toothed pulley 1 of this embodiment is a single-flanged pulley in which the flange portion 122 is integrally formed with one end of the toothed portion 121 in the axial direction (the other end in this embodiment). The toothed pulley 1 may be a double flanged pulley in which flange portions are integrally formed on one end side and the other end side of the toothed portion 121, respectively.

[0042] (Core 11) The core metal 11 is formed in a cylindrical shape with a bottom, with a bottom plate 111 forming a bottom portion at the other end side. A plurality of (four in this embodiment, equally spaced in the circumferential direction) mounting holes 112 are formed in the bottom plate 111 and extend through the bottom plate 111 in the axial direction (see FIG. 5). Bolts 21 are inserted through the mounting holes 112, and the toothed pulley 1 is fixed (bolted) to the ball nut 20. For the core bar 11, mainly from the viewpoint of ensuring productivity, a steel plate (having a thickness of about 2 mm) such as a rolled steel plate or a high-tensile steel plate is pressed by a method described later.

[0043] (Outer surface of core bar 11: anti-rotation and anti-dislodgement) As shown in Figures 4 to 6, the entire outer peripheral surface of core bar 11 facing tooth portion 121 of resin portion 12 is formed with a large number of uniformly distributed pinhole-shaped recesses 113 with a depth of 0.2 mm or more and less than half the thickness of core bar 11 to prevent rotation and slipping out. The recesses 113 may be distributed unevenly over the entire outer peripheral surface facing the tooth portion 121 of the resin portion 12. However, from the standpoint of strength and dimensional accuracy, it is preferable that the recesses 113 are distributed uniformly as in this embodiment.

[0044] The depth of recess 113 (see Figure 10) is 0.2 mm or more and less than half the thickness of core bar 11 (for example, 0.8 mm or less when the thickness (outer peripheral portion) of core bar 11 is 1.6 mm), and preferably 0.2 mm or more and less than 1 / 3 the thickness of core bar 11 (for example, 0.5 mm or less when the thickness (outer peripheral portion) of core bar 11 is 1.6 mm). If the depth of the recess 113 is less than 0.2 mm, in an operating environment where significant temperature changes (for example, of the order of 100°C) occur, the thermal expansion of the resin part 12 will be significantly greater (for example, by about 0.1 mm in the radial direction) than that of the core wire 11, resulting in a poor anchor effect and in some cases making it impossible to ensure the bonding strength of the resin part 12 to the core wire 11. On the other hand, if the depth of the recess 113 exceeds half the thickness of the core metal 11, when the recess 113 is formed by plastic processing (press processing), it will undergo excessively large plastic deformation, and the inner surface of the core metal 11 facing the recess 113 may bulge.

[0045] The cross-sectional shape of the recess 113 (the shape of the cross section along the direction perpendicular to the depth direction of the recess 113) is not limited, and may be a circle, an ellipse, an oval, a triangle, a rectangle, a polygon, or any other special shape. From the viewpoint of ease of processing and avoidance of stress concentration, a circle is preferable. The cross-sectional shape of the recess 113 may be uniform in the depth direction, or may change, for example, to a tapered shape, or may have a pointed shape only near the bottom. The corners of the bottom may be chamfered.

[0046] The average diameter of the recesses 113 (the diameter when a cross section along a direction perpendicular to the depth direction of the recesses 113 is replaced with a circle, see FIG. 10) is 0.2 mm to 3.5 mm, preferably 0.5 mm to 3 mm. If the average diameter of the recesses 113 is less than 0.2 mm, when the recesses 113 are formed by plastic processing (press processing), it may be impossible to ensure the durability of the pin-shaped die member for forming the recesses 113. Furthermore, the anchor effect of the recesses 113 becomes poor, and it may be impossible to ensure the bonding strength of the resin part 12 to the core metal 11. On the other hand, if the average diameter of the recesses 113 exceeds 3.5 mm, the outer surface of the tooth portion 121 facing the recesses 113 may be recessed (dented) after insert molding (particularly injection molding). In particular, when recess 113 has a depth of 0.2 mm or more and 1 / 3 or less of the thickness of core wire 11 and an average diameter (average width) of 0.5 mm or more and 3 mm or less, even if the thermal expansion of resin part 12 is significantly larger than that of core wire 11 (for example, about 0.1 mm in diameter) due to the difference in linear expansion coefficients between the materials of resin part 12 and core wire 11 in an environment of use where significant temperature changes (for example, about 100°C) occur, the anchor effect of recess 113 is not lost, and the dimensional accuracy of tooth part 121 and the bonding strength of resin part 12 to core wire 11 can be ensured at a higher level.

[0047] The number of recesses 113 is large as long as the recesses 113 are formed in a dispersed manner over the entire outer circumferential surface of the core 11 facing the teeth 121 of the resin part 12. "Large number" refers to a number that is large enough to be counted by visual inspection, and a number far smaller than an infinite number (e.g., several hundred). The number of recesses 113 depends mainly on the size (outer diameter, width) of the core 11, the arrangement (arrangement interval) of the recesses 113, and the anchor effect of the recesses 113 (bonding strength of the resin part 12 to the core 11).

[0048] The arrangement (interval) of the recesses 113 may be any as long as the recesses 113 are formed in a dispersed manner over the entire outer circumferential surface of the core 11 facing the teeth 121 of the resin portion 12, in other words, as long as the recesses 113 are not formed locally (in a locally dense and biased manner), but it is preferable that the recesses 113 are arranged at equal intervals in the circumferential and axial directions. This ensures that the recesses 113 are formed in a dispersed manner. The recesses 113 may also be arranged in a staggered manner overall.

[0049] When the recesses 113 are arranged at equal intervals in the circumferential and axial directions, the arrangement interval (pitch) is set to be larger as the size (average diameter) of the recesses 113 becomes larger and to be smaller as the size (average diameter) of the recesses 113 becomes smaller, mainly taking into account the bonding strength of the resin part 12 to the core metal 11.

[0050] The cross-sectional shape and the arrangement interval of the recesses 113 may be somewhat irregular (unevenly narrowed or unevenly widened relative to the design value), and the cross-sectional shape of the recesses 113 may be uneven in the depth direction. This is because, when the core bar 11 is manufactured by press working, stresses such as bending and tension are applied in the process of drawing the core bar 11 from a plate-like state to a cylindrical shape with a bottom, and the cross-sectional shape and the arrangement interval of the recesses 113 may become somewhat irregular, but there is no problem as long as the average diameter of the recesses 113 (the diameter when the cross section is replaced with a circle) and the arrangement interval of the recesses 113 are within the above-mentioned ranges.

[0051] (Bottom plate 111 of core metal 11) In order to ensure sufficient bonding strength between the resin portion 12 and the core metal 11, a rotation stopper may be formed not only on the outer circumferential surface of the core metal 11 but also on the bottom plate 111 of the core metal 11. Incidentally, even if convex portions and / or concave portions extending in a direction parallel to the axial direction are formed on bottom plate 111 of core bar 11 as a normal design method, the anti-rotation function is achieved but the anti-dislodgement function is not achieved.

[0052] Because the bottom plate 111 of the core bar 11 is not opposed to the tooth portion 121 of the resin part 12, it is considered that the anti-rotation provided on the bottom plate 111 of the core bar 11 will not affect the dimensional accuracy of the tooth portion 121. Therefore, the form of the anti-rotation provided on the bottom plate 111 of the core bar 11 does not need to be the same as that of the recess 113, and a normal design method may be used. For example, in addition to the anti-rotation function, for further weight reduction, punched holes (not shown) may be provided between the mounting holes 112 of the bottom plate 111 of the core bar 11 (for example, four holes equally spaced in the circumferential direction), and the resin constituting the resin part 12 may be configured to enter the inside of the punched holes.

[0053] (Resin part 12) The resin part 12 constitutes the outer portion of the core metal 11, and forms the teeth part 121 and the flange part 122. By covering not only the outer peripheral surface of the core metal 11 but also the bottom plate 111 of the core metal 11, the strength and rigidity of the resin part 12 can be increased. Further, a part of the resin constituting the resin portion 12 has solidified in a state in which it has entered the inside of each of the recesses 113 formed on the outer circumferential surface of the core metal 11 .

[0054] When reducing the weight of the toothed pulley 1, the thickness of the tooth portion 121 (especially the tooth groove portion) of the resin portion 12 and the thickness of the covering portion of the bottom plate 111 of the core metal 11 are designed to be as thin as possible (for example, to about 2 mm) within a range that does not interfere with manufacturing.

[0055] The bottom 123 covering the bottom plate 111 of the core bar 11 is provided with a notch 124 that exposes the mounting holes 112 provided in the bottom plate 111 of the core bar 11 and the other end face of the bottom plate 111 around the mounting holes 112 in the axial direction. In this embodiment, concentric notches 124 (four places) having a diameter larger than that of the mounting holes 112 are provided for the four mounting holes 112 provided in the bottom plate 111 of the core bar 11. As a result, the notches 124 function as a counterbore that allows the end face (the end face on the male thread side) of the head of the bolt 21 to abut (seat) on the outer bottom face of the core bar 11 when the toothed pulley 1 is bolted to the ball nut 20 of the electric power steering device, and prevents interference between the head of the bolt 21 and the resin part 12.

[0056] (Material of resin part 12) The material of the resin part 12 may be either a thermoplastic resin or a thermosetting resin, but it is preferable to use a thermoplastic resin, mainly from the viewpoint of shortening the cycle time in insert molding (especially injection molding) and ensuring the productivity of the toothed pulley 1.

[0057] However, taking into consideration that the ambient temperature will rise to about 120°C due to the heat dissipation from the engine, it is advisable to use thermoplastic engineering plastics with excellent heat resistance as the pulley material. Furthermore, in order to provide sufficient rigidity and durability under the operating conditions of the toothed pulley 1, it is advisable to compound glass fiber or the like with synthetic resins classified as engineering plastics.

[0058] Examples of engineering plastics include polyphenylene sulfide, polyacetal, polyphenylene oxide (also referred to as polyphenylene ether), polycarbonate, polyether ether ketone, polyamide, polyimide, polyamide imide, polyether imide, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyether sulfone, polysulfone, polyarylate, and fluororesins (e.g., polytetrafluoroethylene). Among these, polyphenylene sulfide resin (hereinafter abbreviated as PPS) is suitable for this application because of its excellent heat resistance, mechanical properties, dimensional stability, flame retardancy, moldability, and the like. When the resin constituting the resin portion 12 is a thermosetting resin, it can be selected from phenol resin, epoxy resin, vinyl ester resin, unsaturated polyester resin, and the like.

[0059] According to the above configuration, in the toothed pulley 1 composed of a core wire 11 and a resin portion 12, a large number of pinhole-shaped recesses 113, which serve to prevent the resin portion 12 from rotating or coming loose relative to the core wire 11, are uniformly distributed and not formed locally on the outer peripheral surface of the core wire 11 facing the tooth portion 121 of the resin portion 12 (see Figure 3). Therefore, even if the thickness of tooth portion 121 (particularly the groove portion of tooth portion 121) is designed to be thin (for example, as thin as about 2 mm), when insert molding (particularly injection molding) is performed using core wire 11 as an insert member, the flow of molten resin (particularly the flow path thickness and internal pressure) in the cavity portion of the mold facing tooth portion 121 does not change locally and is kept relatively uniform, making it easier to ensure the dimensional accuracy of tooth portion 121 (particularly the accuracy of the tooth tip diameter). Moreover, the pinhole-like recess 113 has a depth of 0.2 mm or more and half the thickness of the core bar 11 or less. Therefore, even if, in an operating environment where significant temperature changes (for example, of the order of 100°C) occur, the difference in the linear expansion coefficients between the materials of resin part 12 and core bar 11 causes the thermal expansion of resin part 12 to be significantly greater than that of core bar 11 (for example, by about 0.1 mm in diameter), the anchor effect of recess 113 is not lost, and the bonding strength of resin part 12 to core bar 11 can be ensured. Furthermore, the formation of the pinhole-shaped recesses 113 does not require a special design that would increase the manufacturing effort (separate process), and the above-mentioned anti-rotation and anti-slip features (multiple recesses 113) can be formed while maintaining productivity, thereby preventing an increase in manufacturing costs. In other words, according to the above configuration, in a toothed pulley 1 composed of a core metal 11 and a resin portion 12, it is possible to ensure both the dimensional accuracy of the tooth portion 121 and the bonding strength of the resin portion 12 to the core metal 11 while maintaining productivity.

[0060] (Other embodiments) As described above, the toothed pulley 1 may be a double-flanged pulley in which flange portions are integrally formed on one end side and the other end side of the toothed portion 121 (not shown). In this case, it can be formed by a known method. For example, although details are omitted, the resin portion 12 on one end side of the single-flanged pulley adopted in the toothed pulley 1 of this embodiment (the resin portion on the side on which the flange portion 122 is not formed) and a flange member separately manufactured using the same resin material as the resin portion 12 are configured to be engaged with each other in a concave-convex manner in the axial direction, and then the two are joined in this convex-convex engaged state (a state in which the axial and radial positions have been determined) by, for example, ultrasonic welding, to form a double-flanged pulley.

[0061] (Manufacturing method of toothed pulley 1: Manufacturing method of core bar 11) The core bar 11 is formed into a cylindrical shape with a bottom by a series of plastic working (pressing) steps, including the formation of the numerous recesses 113, mainly from the viewpoint of ensuring productivity. The multiple mounting holes 112 (and punch holes if punch holes are provided between the mounting holes 112) to be formed in the bottom of the core bar 11 may be punched out simultaneously in the first press process (punching forming), but in order to ensure dimensional accuracy, they may also be punched out in a post-processing step (fourth press process) following the third press process (drawing forming).

[0062] (1) First pressing process (see Fig. 7(a)) First, a blank is formed by stamping. Specifically, a sheet material (a strip-shaped material made of steel) wound in a coil shape is pulled out and punched into a disk shape to form a blank material.

[0063] (2) Second pressing process (see Fig. 7(b)) A core metal precursor having a recess 113 is formed by plastic working. Specifically, the blank material is plastically processed (pressed) while still in plate form to form a plate-shaped core bar precursor in which a large number of pinhole-like recesses 113 of a predetermined depth are uniformly distributed over the entire outer peripheral surface portion (annular portion) of the core bar 11 corresponding to the outer peripheral surface facing the tooth portion 121 of the resin portion 12.

[0064] In this embodiment, the recess 113 formed by plastic working is formed so that the cross section along the direction perpendicular to the depth direction of the recess 113 is circular. In this case, stress concentration on the recess 113 can be avoided, and the processing of the recess 113 in the blank in the second press step becomes relatively easy.

[0065] (3) Third pressing process (see Fig. 8(c1) and Fig. 8(c2)) A bottomed cylindrical core 11 is formed from a plate-shaped core precursor by drawing. The core bar precursor (workpiece) is clamped and held between the holder (pressure) and the die to a degree that prevents defects such as wrinkles from occurring in the core bar precursor (workpiece) during drawing (when the punch is pushed into the die and the core bar precursor, including the portion held down by the holder, is gradually pulled into the die). As a result of the drawing, the thickness of the outer peripheral surface portion of the core bar 11, where stress acts in the tensile (stretching) direction, is formed to be slightly thinner than the thickness of the bottom plate 111.

[0066] (4) Fourth pressing process (not shown) Usually, the following press processing is performed as a process (fourth press processing) following the third press processing (drawing), which is performed after the third press processing. This completes a series of plastic processing (press processing) steps for manufacturing the core bar 11, and the core bar 11 (insert member) is completed. Trimming (cutting off) excess material (see Figure 8(c2)) Processing (punching) the mounting holes 112 (and punching holes if punching holes are provided between the mounting holes 112) Finishing (surface pressing to ensure dimensional accuracy) processing

[0067] All of the above steps are carried out using a pair of upper and lower dies which are relatively close to each other and spaced apart from each other. However, for the third press process (squeezing), in order to prevent excessive bending or pulling stresses from being applied to the core metal precursor (workpiece) during press processing (squeezing), which would cause defects such as wrinkles or breaks in the core metal precursor, it is also possible to use a method in which the squeezing angle performed by a single pair of upper and lower dies is limited, and the squeezing is performed sequentially (while the core metal precursor is fed forward in multiple batches) using multiple dies.

[0068] Note that Figure 8 is an explanatory diagram of the third press process (drawing), but only shows the state before drawing (the state immediately before the first draw-forming is performed) (Figure 8(c1)) and the state after drawing (the state immediately after the final draw-forming is performed) (Figure 8(c2)).

[0069] According to the above method, a disk-shaped blank material (flat plate) is plastically processed (pressed) to form a large number of pinhole-like recesses 113 of a predetermined depth, and then the bottomed cylindrical core bar 11 is formed by drawing. Therefore, a large number of recesses 113 that function as a rotation prevention and slip-out prevention device can be formed relatively easily on the entire outer circumferential surface of the core bar 11. Furthermore, the series of press processes required for manufacturing the core bar 11, i.e., the first press process in which a disk-shaped blank material is formed by punching, the second press process in which a plate-shaped core bar precursor having a number of pinhole-like recesses 113 uniformly distributed therein, and the third press process in which a bottomed cylindrical core bar 11 is formed from the plate-shaped core bar precursor by drawing, are all performed by simply pressing the core bar precursor (workpiece) that flows in one after another using a specified press mold (one set of upper and lower molds) (i.e., only one press process is required as a whole). Therefore, it is possible to suppress an increase in the manufacturing effort (separate process) required for forming a large number of recesses 113 that perform the functions of preventing rotation and coming off. Moreover, because plastic processing does not cut the metal fiber structure as in mechanical (cutting) processing, it is possible to suppress a decrease in the strength of the core 11, including the strength of the recess 113, compared to a case in which the core 11 is manufactured by mechanical processing. In addition, it is possible to increase the processing speed and production efficiency and reduce material loss (improve yield), so that it is possible to minimize the amount of mechanical processing and reduce costs.

[0070] (Manufacturing method of toothed pulley 1: Forming method of resin portion 12) The resin portion 12 is formed by insert molding. Specifically, the core metal 11 is placed in advance in a mold as an insert member, and the resin that constitutes the resin portion 12 is filled in a molten state into the cavity of the mold, and the toothed pulley 1 is formed in a state where the resin has penetrated into each of the recesses 113 and solidified (insert molding process).

[0071] In addition, when forming the resin portion 12 in a cylindrical shape with a bottom, a gate (inlet hole) leading to the cavity of the mold is usually provided on the other end face side (other end side) of the bottom 123 in order to suppress the occurrence of molding defects (welds, etc.) (the gate positions are, for example, multiple locations equally spaced circumferentially near the outer periphery of the other end face of the bottom 123), and the molten resin that enters the cavity flows within the cavity of the bottom 123 to form the resin portion 12 having the bottom 123 and the flange portion 122, and also flows mainly in the axial direction from the other end side (bottom side) to one end side (opening side) within the cylindrical cavity (the space on the outer periphery of the core metal 11) that constitutes the tooth portion 121, forming the tooth portion 121.

[0072] The insert molding may be performed using either a thermoplastic resin or a thermosetting resin, and may be performed using either injection molding or compression molding. However, from the viewpoint of shortening the cycle time and ensuring the productivity of the toothed pulley 1, it is preferable to use injection molding using a thermoplastic resin. EXAMPLES

[0073] In the present invention, in a toothed pulley 1 composed of a core wire 11 and a resin part 12, it is necessary to ensure both the dimensional accuracy of the tooth part 121 and the bonding strength of the resin part 12 to the core wire 11 (at an ambient temperature of 120°C, which corresponds to the actual usage environment) while maintaining productivity. In this example, toothed pulleys according to Examples 1 to 20 and Comparative Examples 1 to 13 (hereinafter referred to as "test specimens") were produced, and visual and dimensional inspections, destructive tests, and disassembly inspections were performed to carry out comparative verifications. The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0074] [Materials used] Core: Cold-rolled steel plate (SPCC) (JIS G 3141:2005 compliant) Resin part: PPS resin (Durafide (registered trademark) 6150T73, manufactured by Polyplastics Co., Ltd.)

[0075] [Manufacturing of toothed pulleys] The core metal was made of the same steel plate as the above-mentioned material in all the test specimens, but the core metal was manufactured in the following manner. For Examples 1 to 20 and Comparative Examples 4 to 13, the cores were produced by a series of press workings in accordance with the method described in the above embodiment, including the "rotation prevention and slip-out prevention" methods. For Comparative Example 3, in order to have a configuration without "anti-rotation and anti-pullout features," the core bar was produced by a series of press processes similar to those of Example 1, except that the second press process (machining of the recess) was omitted from the methods described in the above embodiments. For Comparative Example 1, the same core bar as in Comparative Example 3 was produced by the same method as in Comparative Example 3, and then the "rotation stopper and slip-out stopper" were formed by shot blasting to produce the core bar. For Comparative Example 2, the core bar was produced by machining, including the "rotation stopper and the stopper."

[0076] The resin part was common to each test specimen and was formed by known insert molding (injection molding) using the same thermoplastic resin and the same injection molding die as the above-mentioned materials, in accordance with the method described in the above embodiment. The gates (inlet holes) leading to the cavity were provided (at four equal locations in the circumferential direction) on the cavity wall corresponding to the other end face of the bottom (the part near the outer periphery: the position of the gate mark shown in Figure 2). The injection molding conditions (temperature, pressure, time, etc.) were the same for each specimen, except for the (fine adjustment of) the measurement values.

[0077] [Manufactured toothed pulley (specimen)] (shape and dimensions) Example 1 is shown in Figs. 2 to 6, and Comparative Example 2 is shown in Fig. 9 (Examples 2 to 20, Comparative Example 1, and Comparative Examples 3 to 13 are not shown).

[0078] (Common to each test specimen) The pulley is a single flanged toothed pulley with a single flange that protrudes radially outward from the bottom (other end) all the way around, with a height of 2 mm (from the tip of the teeth to the outer circumferential surface of the flange). The bottom has mounting holes (four holes in the bottom plate of the core) with notches (countersinks), but no anti-rotation holes (punch holes, etc.).

[0079] Teeth: Helical teeth (tooth pitch 2 mm, number of teeth 103, tooth height 0.9 mm), thickness of tooth groove (thinnest part of tooth) 2.2 mm, total thickness of tooth (tooth height + tooth groove thickness) 3.1 mm Outer diameter of teeth (tooth tip diameter) specifications: Reference dimension 65.11mm, tolerance ±0.05mm Teeth width (axial length): 28.5 mm Core: Outer diameter 58.9 mm, width 31.4 mm, thickness (plate thickness) 1.8 mm (bottom plate) / 1.6 mm (outer periphery) Bottom: Resin thickness 1.4mm Pulley width (axial length): 32.8 mm

[0080] (Different for each test specimen) (Prevention of rotation and removal) The only structural differences between the test specimens were the configuration of the "anti-rotation and anti-slip" (target area: the outer peripheral surface of the core wire facing the teeth of the resin part) and the presence or absence of the "anti-rotation and anti-slip" features; there were no other differences.

[0081] (Examples 1 to 20, Comparative Examples 4 to 13) A large number of pinhole-shaped recesses were formed evenly distributed over the entire outer surface of the core bar facing the teeth of the resin part (the resin constituting the resin part was solidified in a state where it had filled the recesses).

[0082] (Design of the recess (goal)) Example 1 Depth 0.5mm [Approx. 1 / 3 of the core thickness (outer periphery)] Circular cross section with average diameter of 1 mm The cross section along the depth direction is rectangular (flat bottom, no chamfered corners) The recesses are spaced 5mm apart in both the circumferential and axial directions. The total number of recesses is 222 (6 axial rows x 37 circumferential rows (multiple))

[0083] (Examples 1 to 4, Comparative Examples 4 to 5) As shown in Table 3, the configuration was the same as that of Example 1 (average diameter of the recesses: 1.0 mm) based on Example 1, except that the depth of the recesses was changed from 0.5 mm to 0.1 mm to 0.9 mm.

[0084] Comparative Example 1 The entire outer peripheral surface of the core wire facing the teeth of the resin part was shot blasted to form a large number of small, pear-skinned recesses (dents) dispersed thereon (the resin that makes up the resin part was solidified in a state where it had filled the recesses). The size of the recesses was about 0.05 mm in both average diameter and depth. The average spacing between the recesses was about 0.1 mm.

[0085] Comparative Example 2 As shown in Figure 9, one end (opening side) of the outer peripheral surface facing the teeth of the core wire is formed with a polygonal convex portion (a 16-sided outward flange (corresponding to D in Figure 10 of Patent Document 1)) that protrudes radially outward around the entire circumference when viewed from the axial direction. The dimensions of the convex part are: height (from the outer surface of the core to the outer periphery of the convex part) minimum 0.5 mm (each side), maximum 1.1 mm (each top), width 2 mm

[0086] (Comparative Example 3 (Blank)) The outer peripheral surface of the core metal, which faces the teeth of the resin portion, is formed flat and solid, without any anti-rotation or anti-disengagement means (convex and / or concave portions).

[0087] (Examples 2, 5 to 8, Comparative Examples 6 to 7) As shown in Table 4, the configuration was the same as that of Example 2 (depth of recesses: 0.2 mm) except that the average diameter of the recesses was changed from 1.0 mm to 0.1 mm to 4.0 mm.

[0088] (Examples 3, 9 to 12, Comparative Examples 8 to 9) As shown in Table 5, based on Example 3 (depth of recesses: 0.3 mm), the average diameter of the recesses was changed from 1.0 mm to 0.1 mm to 4.0 mm, and the other configurations were the same as those of Example 3.

[0089] (Examples 1, 13 to 16, Comparative Examples 10 to 11) As shown in Table 6, the configuration was the same as that of Example 1, except that the average diameter of the recesses was changed from 1.0 mm to 0.1 mm to 4.0 mm, based on Example 1 (depth of recesses: 0.5 mm).

[0090] (Examples 4, 17 to 20, Comparative Examples 12 to 13) As shown in Table 7, the configuration was the same as in Example 4 (depth of recesses: 0.8 mm) except that the average diameter of the recesses was changed from 1.0 mm to 0.1 mm to 4.0 mm.

[0091] [Evaluation of toothed pulleys: items, methods and standards] For each test specimen (Example, Comparative Example), in order to determine whether a toothed pulley capable of solving the problem of the present application was obtained, the manufacturing quality (appearance, dimensions (tooth tip diameter)), the bonding strength of the resin part to the core wire (rotational torque, pull-out strength) (at 120°C), and the productivity (whether or not manufacturing effort (separate process) was required) were verified.

[0092] [Appearance and dimensional inspection] (Test Method) In order to determine the manufacturing quality, the appearance of each part of the toothed pulley (specimen) after production was visually inspected (especially for any abnormalities in appearance due to the processing of "rotation stop and slip-out prevention"), and also, from the viewpoint of ensuring the dimensional accuracy of the teeth and maintaining good meshing with the toothed belt, the "tooth tip diameter" (outer diameter of the teeth), which is the most important dimension, was inspected to see if it was within the specified dimensional tolerance at room temperature according to the specifications. The tooth tip diameter was measured at three points in the axial direction [one end of the teeth (opening side), the center of the teeth, and the other end of the teeth (bottom side)] of each specimen at room temperature using a three-dimensional coordinate measuring machine (DuraMax (registered trademark) manufactured by Tokyo Seimitsu Co., Ltd.).

[0093] (Judgment criteria) In addition to there being no abnormality in the appearance (especially the appearance associated with the "anti-rotation and anti-slip" processing), if the tooth tip diameter is within the dimensional tolerance of ±0.03 mm of the standard dimension 65.11 at all three axial points, the manufacturing quality of the toothed pulley is evaluated as excellent and it is given an A rating. In addition to there being no abnormality in the appearance (especially the appearance associated with the "anti-rotation and anti-slip" processing), if the tooth tip diameter is not within the dimensional tolerance of ±0.03 mm but is within the dimensional tolerance of ±0.04 mm for the reference dimension 65.11 at all three axial points, the manufacturing quality of the toothed pulley is evaluated as good and it is given a grade of b. If any signs of abnormality were found in the appearance (especially the appearance associated with the "anti-rotation and anti-slip" processing), and / or if the tooth tip diameter was not within the dimensional tolerance of ±0.04 mm but within the dimensional tolerance of ±0.05 mm of the reference dimension 65.11 at all three axial points, the manufacturing quality of the toothed pulley was evaluated as being within the acceptable range and given a rating of C. If any abnormalities were found in the appearance (especially the appearance associated with the "anti-rotation and anti-slip" processing) and / or if even one point of the tooth tip diameter was outside the specified dimensional tolerance (±0.05 mm from the standard dimension 65.11), the manufacturing quality of the toothed pulley was evaluated as not being able to be ensured, and a rating of "D" was given. From the viewpoint of suitability for practical use in this application (manufacturing quality of the toothed pulley), any of the toothed pulleys rated a to c was determined to be at the pass level.

[0094] [Destructive testing] (Test Method) In order to determine whether the provision of a "rotation stopper and pull-out stopper" ensures the bonding strength of the resin part to the core wire even in an actual usage environment where significant temperature changes (for example, of about 100°C) occur, measurements were made on two evaluation items, "rotational torque" and "pull-out strength," for each toothed pulley (specimen), excluding those specimens for which external abnormalities were found in the previous appearance and dimensional inspection.

[0095] (Rotational Torque) To verify the effectiveness of the anti-rotation device, the torque was measured when the resin portion was displaced circumferentially relative to the core metal. (Measurement method) A toothed pulley (specimen) was left in a constant temperature bath with the internal temperature held at approximately 120°C for 3 hours, and then while the resin part was fixed (held so that it could not rotate) with a jig, a torque wrench connected to the end of a shaft that was attached to the core wire (central hole part) so that it could not rotate relative to the shaft was rotated, and the torque (Nm) was measured at the time when the core wire began to rotate (slip between the core wire and the resin part).

[0096] (Pull-out strength) To verify the effectiveness of the retaining mechanism, the force exerted when the resin portion was displaced axially relative to the core metal was measured. (Measurement method) Using a universal testing machine with a thermostatic chamber (maximum load capacity 50 kN), a toothed pulley (specimen) was left in the thermostatic chamber with the internal temperature maintained at approximately 120°C for 3 hours, and then, with the resin part fixed to the lower support (supported so that it could not move axially downward), the core bar was pressed from above in the axial direction in compression test mode (pressing speed 5 mm / min), and the load (kN) at which the core bar began to come out was measured.

[0097] In addition, in the toothed pulley (specimen), the estimated difference in the amount of thermal expansion between the resin part and the core metal under actual use conditions (ambient temperature of 120°C) is as follows. Linear expansion coefficient (α) of the core metal material (SPCC): 13.7E-6 Linear expansion coefficient (β) of the resin material (PPS) of the resin part: 3.00E-5 Temperature change (Δt): 100℃ (120℃-20℃) Interface diameter between core and resin (outer diameter of core) (d): 58.9 mm The respective amounts of thermal expansion and the differences between the amounts of thermal expansion for the above interface diameter d are as follows: Thermal expansion of the core metal: 0.081 mm (= α × Δt × d) Thermal expansion of resin part: 0.177mm (=β×Δt×d) Difference in thermal expansion between resin part and core metal: Approx. 0.10 mm in diameter, approx. 0.05 mm on one side in the radial direction

[0098] (Judgment criteria) Looking at the safety factor for practical use, if the "rotational torque" is 180 Nm or more and the "pull-out strength" is 9 kN or more, the joint strength of the toothed pulley (between the core metal and resin part) (at an ambient temperature of 120°C) is evaluated as excellent, and an A rating is given. Looking at the safety factor for practical use, if the "rotational torque" is 150 Nm or more and less than 180 Nm and the "pull-out strength" is 7 kN or more and less than 9 kN, the joint strength of the toothed pulley (between the core wire and resin part) (at an ambient temperature of 120°C) is evaluated as good, and a grade of b is given. Looking at the safety factor for actual use, when the "rotational torque" is between 120 Nm and 150 Nm and the "pull-out strength" is between 5 kN and 7 kN, the joint strength of the toothed pulley (between the core wire and resin part) (at an ambient temperature of 120°C) is evaluated to be within the allowable range and given a C rating. If the "rotational torque" is less than 120 Nm and / or the "pull-out strength" is less than 5 kN, it is evaluated that the joint strength of the toothed pulley (between the core wire and resin part) (at an ambient temperature of 120°C) cannot be secured, and the rating is d. From the viewpoint of suitability for practical use in this application (bonding strength of the resin part to the core metal (at an atmospheric temperature of 120°C)), any of the toothed pulleys rated a to c was deemed to be at the pass level.

[0099] [Disassembly inspection] (Test Method) In order to determine productivity (whether or not manufacturing effort (separate processes) is required), the toothed pulley (test specimen) was disassembled and the structure of the outer surface of the core bar (especially the anti-rotation and anti-slip features) and the manufacturing method of the core bar were confirmed.

[0100] (Judgment criteria) If it is recognized that the formation of the "anti-rotation and anti-slip" does not lead to an increase in the manufacturing effort (separate process) (does not constitute a special design), productivity can be maintained, and an increase in manufacturing costs can be suppressed, it is evaluated that the productivity of toothed pulleys can be ensured, and an A rating is given. If it is recognized that the formation of the "anti-rotation and anti-slip" leads to increased manufacturing effort (separate process) (corresponding to a special design), productivity cannot be maintained, and increases in manufacturing costs cannot be prevented, it is evaluated that the productivity of toothed pulleys cannot be ensured, and a grade of B is given. From the viewpoint of suitability for practical use in this application (productivity of toothed pulleys), a toothed pulley was determined to be at the pass level.

[0101] (Overall Judgment) The overall criteria for judging (ranking) a toothed pulley as capable of resolving this issue were determined based on the results of the above three evaluation items [manufacturing quality, bonding strength of the resin part to the core wire (at an ambient temperature of 120°C), and productivity] as follows, with a rank of C or above being considered a pass. Rank A: When all of the above evaluation items were rated as A, it was determined that there were no problems in practical use and was given the highest rank. Rank B: If productivity was rated a and the other two evaluation items [manufacturing quality, bonding strength of the resin part to the core wire (at an ambient temperature of 120°C)] were not rated c or d, but at least one was rated b, the product was deemed to have no problems in practical use but was ranked somewhat inferior. Rank C: If productivity was rated a and the other two evaluation items [manufacturing quality, bonding strength of the resin part to the core wire (at an ambient temperature of 120°C)] were not rated d but at least one was rated c, the product was deemed to have no problems in practical use but was slightly inferior to Rank B. Rank D: If productivity was rated b and / or any of the other two evaluation items mentioned above [manufacturing quality, bonding strength of the resin part to the core wire (at an ambient temperature of 120°C)] was rated d, the product was deemed to be insufficient in terms of resolving this issue (failed).

[0102] (Verification results and considerations) The verification results are shown in Tables 2 to 7.

[0103] (Comparison with changed "rotation stopper and pull-out stopper" configuration) [Table 2]

[0104] (Example 1, Comparative Examples 1 to 3) The configuration of the "anti-rotation and anti-slip" was changed and compared, including whether or not there was a "anti-rotation and anti-slip" on the outer peripheral surface facing the teeth of the core bar. When the core wire had a "rotation and slip-out prevention" feature in which a large number of pinhole-shaped recesses were uniformly distributed over the entire outer surface facing the teeth of the resin part (depth 0.5 mm, average diameter 1 mm, spacing 5 mm, large number (222 pieces)), (Example 1), the specified (acceptable level) manufacturing quality, bonding strength of the resin part to the core wire (at 120°C), and productivity were ensured (rank A in the overall evaluation).

[0105] In the case of a core wire having a "rotation and slip-out prevention" feature in the form of a large number of concave portions (recesses) dispersed over the entire outer surface facing the teeth of the resin portion, with a depth of 0.05 mm, an average diameter of 0.05 mm, an arrangement spacing of 0.1 mm, and a large number of configurations (Comparative Example 1), the manufacturing quality was rated a, but at an ambient temperature of 120°C, the thermal expansion of the resin portion was significantly greater than that of the core wire (by about 0.05 mm on one radial side), and the anchor effect of the concave portions was almost lost, perhaps because of this, the bonding strength of the resin portion to the core wire (at 120°C) was rated d, and further, because the process of forming the concave portions (shot blasting) is thought to be a separate process from the manufacturing process of the core wire itself, the productivity was also rated b (overall rated as rank D).

[0106] In the case where the core wire had a "rotation and slip-out prevention" (height 0.5 to 1.1 mm, one piece) in which a polygonal (hexagonal) convex portion protruded radially outward around the entire circumference at one end of the outer surface facing the teeth of the resin portion (Comparative Example 2), the bonding strength of the resin portion to the core wire (at 120°C) and the productivity were rated as A, but the tooth tip diameter at one end exceeded the upper limit of the allowable tolerance, and the manufacturing quality was rated as D (rank D in the overall rating).

[0107] When the core wire had no "anti-rotation or anti-slip" feature at all on the outer peripheral surface facing the teeth of the resin part (Comparative Example 3), the manufacturing quality and productivity were rated as A, but the bonding strength of the resin part to the core wire (at 120°C) was rated as D (rank D in the overall evaluation).

[0108] From the above results, it can be said that a toothed pulley having a "rotation and slip-out prevention feature" in the form of a large number of pinhole-shaped recesses (with a depth of 0.5 mm being one of the preferred ranges) uniformly distributed over the entire outer surface facing the teeth of the core is preferable, in that it can ensure the specified (acceptable level) manufacturing quality, bonding strength of the resin part to the core (at 120°C), and productivity.

[0109] (Based on Example 1, comparison with varying the depth of the "anti-rotation and anti-slip" features) [Table 3]

[0110] (Examples 1 to 4, Comparative Examples 4 to 5) In a toothed pulley having a "rotation and slip-out prevention feature in the form of a large number of pinhole-shaped recesses uniformly distributed over the entire outer surface of the core metal that faces the teeth of the resin part, the depth was varied by 0.5 mm based on the toothed pulley of Example 1 (recesses average diameter 1 mm, spacing 5 mm, number of recesses 222) and compared. As the depth of the recess increases, the bonding strength of the resin part to the core metal (at 120°C) tends to increase, possibly due to the increased anchor effect of the recess.

[0111] In Example 4, in which the depth of the recess was increased to 0.8 mm (half the thickness of the core bar) compared to Example 1, signs of abnormality (bulge) were observed in the appearance of the inner surface of the core bar facing the recess, possibly due to the fact that the recess was subjected to a somewhat large amount of plastic processing when it was formed by plastic processing (press processing). As a result, the manufacturing quality was just barely passable (rating c), and was ranked C. Furthermore, in comparison example 5, in which the depth of the recess was increased to 0.9 mm (just over half the thickness of the core bar), an external abnormality occurred in which the inner surface of the core bar facing the recess bulged, possibly due to excessively large plastic deformation when the recess was formed by plastic processing (press processing). As a result, the manufacturing quality was rated d, and the product was ranked D.

[0112] On the other hand, in Example 3 in which the depth of the recessed portion was reduced to 0.3 mm compared to Example 1, it was ranked A, which is the same as Example 1. Furthermore, in Example 2, in which the depth of the recess was reduced to 0.2 mm, the anchor effect of the recess was somewhat lost, and the bonding strength of the resin part to the core wire (at 120°C) was somewhat reduced (rating b), resulting in a rank B. Furthermore, in comparison example 4, in which the depth of the recess was reduced to 0.1 mm, the anchor effect of the recess was significantly lost, and the bonding strength of the resin part to the core wire (at 120°C) was significantly reduced (rating d), resulting in a rank D.

[0113] (Comparison based on Example 2, with the average diameter of the "rotation stopper and pull-out stopper" changed) [Table 4]

[0114] (Examples 2, 5 to 8, Comparative Examples 6 to 7) In a toothed pulley having a "rotation and slip-out prevention feature in the form of a large number of pinhole-shaped recesses uniformly distributed over the entire outer surface of the core metal that faces the teeth of the resin part, the average diameter was varied by 1.0 mm based on the toothed pulley of Example 2 (recesses depth 0.2 mm, spacing 5 mm, number of recesses 222) and compared. In Example 7, in which the average diameter of the recesses was increased to 3.0 mm compared to Example 2, the result was ranked B, equivalent to Example 2. However, when the average diameter of the recesses was increased to 3.5 mm (Example 8), after insert molding (injection molding), signs of abnormality (sink marks) were observed in the appearance of the outer surface of the tooth portion facing the recesses, and the manufacturing quality was at the barely passable level (rating c), resulting in a ranking of C. Furthermore, when the average diameter of the recesses became as large as 4.0 mm (Comparative Example 7), an appearance abnormality occurred in which the outer surface of the tooth portion facing the recesses was sunken (dented), and the manufacturing quality was rated d, resulting in rank D. On the other hand, in Example 6, in which the average diameter of the recesses was reduced to 0.5 mm, the result was ranked B, equivalent to Example 2. However, when the average diameter of the recesses was reduced to 0.2 mm (Example 5), the bonding strength of the resin part to the core wire (at 120°C) was just barely passable (rating c), probably because the anchor effect of the recesses was weakened, and the result was ranked C. Furthermore, when the average diameter of the recesses was reduced to 0.1 mm (Comparative Example 6), the bonding strength of the resin portion to the core metal (at 120° C.) was too small (rating d), resulting in rank D.

[0115] (Comparison based on Example 3, with the average diameter of the "rotation stopper and pull-out stopper" changed) [Table 5]

[0116] (Examples 3, 9 to 12, Comparative Examples 8 to 9) In a toothed pulley having a "rotation and slip-out prevention feature in the form of a large number of pinhole-shaped recesses uniformly distributed over the entire outer surface of the core metal that faces the teeth of the resin part, the average diameter was varied by 1.0 mm based on the toothed pulley of Example 3 (recesses depth 0.3 mm, spacing 5 mm, number of recesses 222) and compared. In Example 11, in which the average diameter of the recesses was increased to 3.0 mm compared to Example 3, the product was ranked A, equivalent to Example 3. However, when the average diameter of the recesses was increased to 3.5 mm (Example 12), after insert molding (injection molding), signs of abnormality (sink marks) were observed in the appearance of the outer surface of the tooth portion facing the recesses, and the manufacturing quality was at the barely passable level (rating c), resulting in a ranking of C. Furthermore, when the average diameter of the recesses became as large as 4.0 mm (Comparative Example 9), an appearance abnormality occurred in which the outer surface of the tooth portion facing the recesses was sunken (dented), and the manufacturing quality was rated d, resulting in rank D. On the other hand, in Example 10, in which the average diameter of the recesses was reduced to 0.5 mm, the anchor effect of the recesses was somewhat lost, and the bonding strength of the resin part to the core metal (at 120°C) was somewhat reduced (rating b), resulting in rank B. Moreover, when the average diameter of the recesses was reduced to 0.2 mm (Example 9), the anchor effect of the recesses was further weakened, and the bonding strength of the resin part to the core metal (at 120°C) was at the barely passable level (rating c), resulting in rank C. Furthermore, when the average diameter of the recesses was reduced to 0.1 mm (Comparative Example 8), the bonding strength of the resin portion to the core metal (at 120° C.) was too small (rating d), resulting in rank D.

[0117] (Comparison based on Example 1, with the average diameter of the "rotation stopper and pull-out stopper" changed) [Table 6]

[0118] (Examples 1, 13 to 16, Comparative Examples 10 to 11) In a toothed pulley having a "rotation and slip-out prevention feature in the form of a large number of pinhole-shaped recesses uniformly distributed over the entire outer surface of the core metal that faces the teeth of the resin part, the average diameter was varied by 1.0 mm based on the toothed pulley of Example 1 (recesses depth 0.5 mm, spacing 5 mm, number of recesses 222) and compared. In Example 15, in which the average diameter of the recesses was increased to 3.0 mm compared to Example 1, the product was ranked A, equivalent to Example 1. However, when the average diameter of the recesses was increased to 3.5 mm (Example 16), after insert molding (injection molding), signs of abnormality (sink marks) were observed in the appearance of the outer surface of the tooth portion facing the recesses, and the manufacturing quality was at the barely passable level (rating c), resulting in a ranking of C. Furthermore, when the average diameter of the recesses became as large as 4.0 mm (Comparative Example 11), the outer surface of the tooth portion facing the recesses was sunken (depressed), resulting in an appearance abnormality, and the manufacturing quality was rated as d, resulting in rank D. On the other hand, in Example 14, in which the average diameter of the recesses was reduced to 0.5 mm, the anchor effect of the recesses was somewhat lost, and the bonding strength of the resin part to the core metal (at 120°C) was somewhat reduced (rating b), resulting in rank B. Moreover, when the average diameter of the recesses was reduced to 0.2 mm (Example 13), the anchor effect of the recesses was further weakened, and the bonding strength of the resin part to the core metal (at 120°C) was at the barely passable level (rating c), resulting in rank C. Furthermore, when the average diameter of the recesses was reduced to 0.1 mm (Comparative Example 10), the bonding strength (at 120° C.) of the resin portion to the core metal became too small (rating d), resulting in rank D.

[0119] (Comparison based on Example 4, with the average diameter of the "rotation stopper and pull-out stopper" changed) [Table 7]

[0120] (Examples 4, 17 to 20, Comparative Examples 12 to 13) In a toothed pulley having a "rotation and slip-out prevention feature in the form of a large number of pinhole-shaped recesses uniformly distributed over the entire outer surface of the core metal that faces the teeth of the resin part, the average diameter was varied by 1.0 mm based on the toothed pulley of Example 4 (recesses depth 0.8 mm, spacing 5 mm, number of recesses 222) and compared. In Example 19, in which the average diameter of the recesses was increased to 3.0 mm compared to Example 4, signs of abnormality (bulging) were observed in the appearance of the inner surface of the core bar facing the recesses, as in Example 1, and the result was ranked C. When the average diameter of the recesses was increased to 3.5 mm (Example 20), signs of abnormality (sink marks) were further observed in the appearance of the outer surface of the tooth portion facing the recesses after insert molding (injection molding), and the product was ranked C. Furthermore, when the average diameter of the recesses became as large as 4.0 mm (Comparative Example 13), an appearance abnormality occurred in which the outer surface of the tooth portion facing the recesses was sunken (dented), and the manufacturing quality was rated d, resulting in rank D. On the other hand, in Example 18, in which the average diameter of the recesses was reduced to 0.5 mm, it was ranked C, equivalent to Example 4. However, when the average diameter of the recesses was reduced to 0.2 mm (Example 17), the anchor effect of the recesses was weakened, and the bonding strength of the resin part to the core wire (at 120°C) was just barely passable (rating c), resulting in a rank C. Furthermore, when the average diameter of the recesses was reduced to 0.1 mm (Comparative Example 12), the bonding strength of the resin part to the core metal (at 120° C.) was too small (rating d), resulting in rank D.

[0121] (Summary of results in Tables 3 to 7) As in Examples 1 to 20, in terms of being able to ensure the specified (acceptable level) manufacturing quality, bonding strength of the resin part to the core wire (at 120°C), and productivity, a toothed pulley having a "rotation and slip-out prevention mechanism" in which a depth of 0.2 mm or more and less than half the thickness of the core wire [0.8 mm or less if the thickness of the core wire (outer peripheral portion) is 1.6 mm] and an average diameter (diameter when the cross section is replaced by a circle) of 0.2 mm or more and 3.5 mm or less are uniformly distributed over the entire outer peripheral surface facing the teeth of the resin part is a preferred embodiment. In addition, a toothed pulley having a "rotation and slip-out prevention feature" in which a depth of 0.2 mm or more and 1 / 3 or less of the core wire thickness [0.5 mm or less if the core wire thickness (outer peripheral portion) is 1.6 mm] and an average diameter (diameter when the cross section is replaced by a circle) of 0.5 mm or more and 3 mm or less are uniformly distributed over the entire outer peripheral surface facing the teeth portion of the resin part can be said to be the most suitable (balanced) embodiment.

[0122] (Effects obtained) From all of the above verification results (Tables 2 to 7), it was confirmed that the toothed pulleys of Examples 1 to 20 correspond to issues (1) to (3), and have a "rotation and slip-out prevention" in the form of a large number of uniformly distributed pinhole-shaped recesses, each with a depth of 0.2 mm or more and less than half the thickness of the core bar, and an average width of 0.2 mm or more and 3.5 mm or less, formed on the entire outer surface of the core bar facing the teeth portion of the resin portion, and are insert molded using the core bar as an insert member to produce a toothed pulley in which part of the resin portion is inserted into the large number of recesses and solidified, making it easy to ensure both the dimensional accuracy of the teeth portion and the bonding strength of the resin portion to the core bar while maintaining productivity. [Explanation of symbols]

[0123] 1 Toothed pulley 11 Core wire 111 Bottom plate 112 Mounting hole 113 Recess 12 Resin part 121 Teeth 122 Flange part 123 Bottom 124 Notch

Claims

1. A cylindrical core bar with a bottom, a resin portion including a tooth portion that is formed by insert molding on an outer side of the core metal, The core has a number of pinhole-like recesses formed dispersed on an outer peripheral surface facing the teeth, the pinhole-like recesses having a depth of 0.2 mm or more and a half or less of the thickness of the core and an average width, which is an average length along a direction perpendicular to the depth direction, of 0.2 mm or more and 3.5 mm or less, A toothed pulley, wherein a portion of the resin portion is solidified in a state where it fills the many recesses.

2. 2. The toothed pulley according to claim 1, wherein the depth of the recess is 0.2 mm or more and 1 / 3 or less of a thickness of the core metal, and the average width of the recess is 0.5 mm or more and 3 mm or less.

3. A method for manufacturing a toothed pulley including a cylindrical core bar with a bottom and a resin part including teeth that is formed by insert molding on an outer side of the core bar, comprising the steps of: a first pressing step of punching the plate material into a disk shape to form a disk-shaped blank material; a second pressing step of forming a plate-shaped core bar precursor by forming a plurality of pinhole-like recesses having a predetermined depth in a dispersed manner by plastic processing on a portion of the blank material corresponding to an outer peripheral surface facing the teeth portion of the core bar; a third pressing step of forming the core bar having a cylindrical shape with a bottom from the core bar precursor by drawing; a method for manufacturing a toothed pulley, the method including: placing the core bar in a mold as an insert member, filling the mold with a molten resin that constitutes the resin portion, and solidifying the resin so that the resin has filled the numerous recesses to form a toothed pulley.

4. In the second pressing step, The method for manufacturing a toothed pulley according to claim 3 , wherein the recess is formed by the plastic working so that a cross section along a direction perpendicular to a depth direction of the recess is circular.

Images