Method for producing a split step gear

Abstract

To achieve phase matching between a large diameter gear and a small diameter gear with required accuracy without depending on a method by fitting of a knock pin and a pin hole when manufacturing a stepped gear 3 by coaxially connecting the large diameter gear 1 and the small diameter gear 2 which are separate bodies.SOLUTION: Applying dummy reference 1d and 2d to the large-diameter and small-diameter gears, measuring an angle between a reference line Lr and a dummy reference line Ldr, the reference line Lr connecting a reference portion set based on a tooth profile in the large-diameter and small-diameter gears and a rotation axis, the dummy reference line Ldr connecting the dummy reference line and the rotation axis, calculating a target value of an angle between the dummy reference lines at which the angle between the reference lines in the large-diameter and small-diameter gears becomes the target value, coaxially arranging the large-diameter and small-diameter gears placed on a jig, and measuring an angle between the dummy reference lines of the large-diameter and small-diameter gears; Either the large diameter gear or the small diameter gear is rotated so that the angle between the dummy reference lines becomes the target value, and the large diameter gear and the small diameter gear are connected to each other.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a stepped gear in which a large-diameter gear and a small-diameter gear are formed coaxially, and more specifically to a method for manufacturing a stepped gear in which a large-diameter gear and a small-diameter gear that are formed separately are fitted together coaxially. [Background technology]

[0002] When a single gear having multiple tooth rows is used in vehicles such as automobiles and other machines, two such gears may be combined coaxially. For example, Patent Document 1 discloses a technique for assembling a combined double-helical gear by combining a pair of helical gears with teeth having different inclination directions coaxially. In this publication, to easily and accurately combine two helical gears in a predetermined phase, the two helical gears are supported concentrically between the opposing surfaces of first and second support plates, respectively. In this state, first and second positioning pieces at the tips of first and second plungers disposed between the first and second support plates are engaged with the outer peripheries of the two helical gears to appropriately regulate the phase of the pair of helical gears. In this state, the second support plate is moved toward the first support plate to couple the two helical gears. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2003-172432 Summary of the Invention [Problem to be solved by the invention]

[0004] Planetary gear mechanisms in vehicle transmissions, for example, often use "step gears" with a large-diameter gear and a small-diameter gear on the same axis, as shown in Figure 1(B). Such stepped gears allow for a gear ratio several times greater without increasing the number of components. The need for stepped gears has also increased with the popularity of 2K-H two-stage planetary reducers. A 2K-H two-stage planetary reducer is a planetary gear mechanism with two planetary gear stages. The teeth of the planetary gear meshing with the sun gear are different from the teeth of the planetary gear meshing with the ring gear, allowing for a gear ratio increase of one stage. While a single-stage 2K-H planetary gear has a gear ratio limit of around 10, a 2K-H two-stage planetary reducer can achieve a gear ratio of 20 to 30. In the case of a 2K-H type two-stage planetary reducer, the axial length of the planetary gear increases by the tooth width of the second stage, and machining of the two-stage planetary gear becomes more difficult.

[0005] "Step gears" like the one described above are manufactured by either making the large and small diameter gears as a single unit (integral type) or by making them separately and then combining them (separate type). In the case of an integrated type, the number of parts and machining processes are minimized, and there is no need to worry about the fastening strength between the large and small diameter gears. However, the tooth profile on the small diameter gear cannot be hobbed because the wall on the large diameter gear does not provide space for the tool to escape in the tooth trace direction. Therefore, the tooth profile of the small diameter gear can only be formed by shaping, which moves the tool back and forth in the axial direction, or by broaching, or by NC contour machining using a small diameter end mill. In the case of a separate type, the large and small diameter gears can be created separately by hobbing, allowing for quick and inexpensive gear production, but the separate gears must be joined within a phase error determined by the required fastening strength. Due to these differences in manufacturing methods, the "integral type" is suitable for manufacturing large gears with high maximum torque and long actuator shaft lengths, while the "separate type" is advantageous for small gears with low maximum torque and short actuator shaft lengths. Therefore, it is difficult to manufacture thin, small stepped gears used in flat actuators or the like without using the separate type.

[0006] When manufacturing a stepped gear as separate pieces, it is necessary to align the phase of the large-diameter gear and the small-diameter gear, i.e., to ensure that the angular difference around the rotation axis between the tooth rows of the large-diameter gear and the small-diameter gear, which are appropriately set, matches within a tolerance. (Depending on the application of the stepped gear, it is not necessary to align the phase of the first and second gears. However, for example, in a two-stage planetary gear of a planetary gear, which has multiple planetary gears, misalignment of the phases will cause the planetary gears to interfere with each other and not rotate.) Regarding this point, a well-known method for aligning the phase of gears is to form pin holes in the two gears and then place them on a jig with knock pins that fit into the pin holes. In this case, the knock pins on the jig are positioned so that the phase of the two gears will be the expected phase when the two gears are placed on the jig with their pin holes fitted to the knock pins. However, with this method, the smaller the gear diameter, the smaller the positional accuracy between the two pin holes and knock pins required for a certain "phasing" tolerance (angle tolerance) and the allowable error in the clearance between the knock pin and pin hole, so as the gear diameter becomes smaller, the processing costs increase and this method is not suitable for mass production.In fact, since it is difficult to form the pin holes and knock pins with a central axis error of 0.005 mm or less, it becomes difficult to achieve a phasing tolerance of 0.15° when the gear pitch diameter is less than 35 mm.

[0007] Therefore, it is possible to avoid the need for machining the above-mentioned knock pins and pin holes by holding the reference of each gear, for example, the tooth profile center axis of each gear, with a jig, adjusting the rotational position between the gears on the jig side, and then fitting the gears together.However, it is extremely difficult to visually identify the position of the reference, such as the tooth profile center axis, with the required accuracy and then apply a jig.To identify the position of the reference, such as the tooth profile center axis, with the required accuracy, it is necessary to use coordinate data measured by setting the gears on a tooth profile measuring machine or a 3D measuring machine.

[0008] In view of the above circumstances, an object of the present invention is to, when manufacturing a stepped gear by coaxially connecting or fitting separately formed large-diameter gears and small-diameter gears, to achieve phase alignment of the large-diameter gear and small-diameter gear that are connected or fitted to each other with the required accuracy without using a method of fitting knock pins with pin holes. [Means for solving the problem]

[0009] According to the present invention, the above problem is solved by a method for manufacturing a stepped gear by coaxially connecting a large diameter gear and a small diameter gear, providing a dummy reference, which is an optically recognizable mark, on a plane perpendicular to the rotation axis of each of the large diameter gear and the small diameter gear; measuring an angle between a reference line connecting a reference portion set based on a tooth profile of each of the large-diameter gear and the rotation axis and a dummy reference line connecting the dummy reference and the rotation axis, for each of the large-diameter gear and the small-diameter gear; calculating a target value of an angle between the dummy reference lines of the large-diameter gear and the small-diameter gear, the target value being an angle between the reference lines of the large-diameter gear and the small-diameter gear when the large-diameter gear and the small-diameter gear are arranged coaxially; a step of coaxially arranging the large diameter gear and the small diameter gear, each mounted on a jig; measuring an angle between the dummy reference lines of the large diameter gear and the small diameter gear; rotating one of the large-diameter gear and the small-diameter gear relative to the other about the rotation axis so that the angle between the dummy reference lines becomes the target value; connecting the large diameter gear and the small diameter gear; This is achieved by a method comprising:

[0010] In the above configuration, the "dummy reference" refers to a mark provided or formed on each surface of the large-diameter gear and the small-diameter gear, as described above. The dummy reference may be a mark of any shape that can be visually confirmed or recognized by camera, i.e., optically recognized, and may be provided at any location on a plane perpendicular to the rotation axis (provided that the large-diameter gear and the small-diameter gear are visible when they are arranged coaxially). Typically, the dummy reference may be a through or non-through circular hole, but is not limited to this. It is preferable that the inner diameter center of the dummy reference can be measured with a repeatability accuracy of ± several μm using a contact point of a three-dimensional measuring machine or a non-contact microscope. The "reference location set based on the tooth profile" refers to a location that serves as a reference for determining the phase difference between two gears. Since the phase difference between gears is usually determined by the difference in the angular position of the tooth profile, the reference location set based on the tooth profile may typically be the center point between the right tooth point and the left tooth point of the tooth profile, but is not limited to this. The points on the right and left teeth may be the intersections of the pitch circle diameter and the right or left tooth. The measurement of the angle between the reference line and the dummy reference line on each of the large-diameter gear and the small-diameter gear may be performed by any method. Typically, the positions of the rotation axis, dummy reference, and reference portion may be identified on an image of each gear taken under a microscope with a camera, and the angle may be calculated from the identified positions (each position may be identified by coordinates set on the image). The position of the rotation axis may be calculated by identifying the position of the outline of the inner opening of the gear through which the rotation axis extends on the image, and calculating the position as the center of that outline. Similarly, the position of the dummy reference may be calculated by identifying the position of the outline of the dummy reference on the image, and calculating the position as the center of that outline. If the outline of the inner opening of the gear and the outline of the dummy reference are circular, the positions of the centers can be calculated by selecting any three points on the outline, as described below, and using the equation of a circle from the coordinate values ​​of the positions of the three points. When the reference portion is the center point of the right tooth and the left tooth, its position may be calculated, for example, by identifying the intersections of a circle (pitch circle) drawn on the image at the position of the pitch radius of the gear from the rotation axis with the right tooth and the left tooth, and then calculating the position of the midpoint of those intersections.Once the positions of the rotation axis, dummy reference, and reference portion are identified, the angle between the reference line and the dummy reference line of each gear can be calculated from the identified positions using any method (the calculation may be performed using the coordinate values ​​of each position).

[0011] As described above, when the angles between the reference lines and the dummy reference lines of the large and small gears are known, the angle between the reference lines when the large and small gears are arranged coaxially can be obtained from the angle between the dummy reference lines. Therefore, if the angle between the reference lines when the phases of the large and small gears are as designed or expected is set as the target value of the angle between the reference lines of the large and small gears, the angle between the dummy reference lines of the large and small gears when the angle between the reference lines of the large and small gears becomes the target value can be set as the target value of the angle between the dummy reference lines.

[0012] Based on the above findings, in the present invention, as described above, first, the large-diameter gear and the small-diameter gear are placed on a jig and arranged coaxially. Then, the angle between the dummy reference lines of the large-diameter gear and the small-diameter gear is measured. This angle measurement may be performed by any method. Typically, as with the measurement of the angle between the reference line and the dummy reference line, the angle may be calculated from the identified positions of the dummy reference and the rotation axis on a microscopic image of each gear taken with a camera. Once the current angle between the dummy reference lines is obtained, one of the large-diameter gear and the small-diameter gear is rotated around the rotation axis relative to the other so that the angle between the dummy reference lines matches the target value. This causes the angle between the reference lines of the large-diameter gear and the small-diameter gear to match the target value, and the phases of the large-diameter gear and the small-diameter gear are set as designed or planned. Then, the large-diameter gear and the small-diameter gear are coupled together in this state. The gears may be coupled together in any manner. When the large diameter gear and the small diameter gear are configured so that the central portion of one of them protrudes in the direction of the rotation axis and fits into an opening in the central portion of the other, the gears may be connected to each other by pressing the protruding central portion of one into the opening in the central portion of the other.

[0013] In the above configuration, a dummy reference is provided for each of the large and small gears that combine to form a stepped gear. The large and small gears are then coaxially positioned, and the angles between the dummy reference lines connecting the dummy references and the rotation axes of the large and small gears are measured. One of the large and small gears is then rotated relative to the other so that the angle between the dummy reference lines reaches a target value that achieves the desired phase difference between the large and small gears. This configuration eliminates the need for highly accurate machining, such as forming knock pins in a jig that holds the gears and drilling holes in the gears to fit the pins, as is required in conventional gear phasing systems. The dummy references may be located anywhere on a plane perpendicular to the rotation axis, as long as their positions can be accurately determined. High accuracy is not required for their application. Thus, according to the configuration of the present invention, when a stepped gear is manufactured by coaxially connecting or fitting separately formed large-diameter gear and small-diameter gear, the phase alignment of the connected or fitted large-diameter gear and small-diameter gear can be achieved with the required precision, and since the method does not rely on fitting a knock pin with a pin hole, stepped gears with smaller diameters than before can also be manufactured.

[0014] In the above-described configuration of the present invention, the large gear and the small gear are each held in a jig and arranged coaxially. The jig used in the present invention may be configured so that the large gear and the small gear are arranged coaxially and rotatable relative to each other, with the connecting portion of the large gear held in the jig and the connecting portion of the small gear held in the jig abutting against each other. In other words, the jig used in the present invention may be configured so that the large gear and the small gear are arranged coaxially and can rotate relative to each other, so that the precise machining accuracy required for knock pins formed for phase alignment between the large gear and the small gear as in conventional cases is not required, and the jig is advantageously easy to manufacture. The jigs for the large and small gears may each have a circular opening in the center, and a single pin or bolt extending along the rotation axis may be inserted through the central openings of the large and small gears and the central openings of the respective jigs, thereby holding the large and small gears coaxially relative to the jigs. This facilitates coaxial alignment between the large and small gears, the small and large gears, and the large and small gears. Alternatively, one of the jigs holding the large and small gears may be coaxially mounted on a rotary table, and the other of the jigs may be held in a hand press. By rotating the rotary table relative to the hand press, the large and small gears may be rotated relative to the other about the rotation axis. The rotary table and the hand press may be existing devices. [Effects of the Invention]

[0015] Thus, in the method of the present invention, in the manufacture of a stepped gear in which separately formed large and small gears are coaxially connected or fitted together, the phase alignment of the large and small gears is performed by measuring the positions of dummy references provided on the large and small gears, and adjusting the rotational positions of the large and small gears based on those measurements. In this configuration, as already mentioned, there is no need for a process of forming knock pins in a jig, and therefore small-diameter stepped gears can be manufactured without being limited by the machining accuracy of the knock pins. In other words, the present invention can be said to be a method of assembling large and small gears so that the phase error between them approaches zero by effectively combining measurements and jigs.

[0016] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief explanation of the drawings]

[0017] [Figure 1] Fig. 1(A) is a schematic perspective view of a large-diameter gear and a small-diameter gear that constitute a stepped gear assembled by the method of this embodiment, and Fig. 1(B) is a schematic perspective view of the stepped gear assembled by the method of this embodiment. Fig. 1(C) is a diagram explaining the tooth profile center point that serves as a reference for phasing the large-diameter gear and the small-diameter gear, and Fig. 1(D) is a schematic partial plan view of the stepped gear, explaining that phasing is performed by adjusting the relative angular positions of the tooth profile center points of the large-diameter gear and the small-diameter gear. [Figure 2] Fig. 2(A) is a schematic plan view of a large-diameter gear that constitutes a stepped gear and has a dummy reference, and Fig. 2(B) is a partially enlarged view of Fig. 2. Figs. 1(C) and 1(D) are diagrams explaining how to identify the rotation axis Cc of the gear and the center of the dummy reference. [Figure 3] FIG. 3 is a schematic plan view of a large-diameter gear and a small-diameter gear arranged coaxially, and is a diagram illustrating the relationship between the angle between the reference lines of the large-diameter gear and the small-diameter gear and the angle between the dummy reference lines. [Figure 4]FIG. 4(A) is a schematic perspective view of a large-diameter gear to be assembled into a stepped gear by the method of this embodiment and a jig to hold it, and FIGS. 4(B) and 4(C) are a schematic plan view and vertical cross-sectional view of the large-diameter gear held in the jig. [Figure 5] 5(A) and (B) are schematic perspective views of a small gear to be assembled into a stepped gear by the method of this embodiment and a jig that holds it. (A) shows the gear side of the jig, and (B) shows the back of (A). Fig. 5(C) is a schematic vertical cross-sectional view of the small gear held in the jig. [Figure 6] 6(A) and 6(B) are a schematic vertical cross-sectional view and a perspective view showing a state in which a large diameter gear and a small diameter gear are coaxially arranged and held by a jig, respectively. [Figure 7] Fig. 7(A) is a schematic partial plan view of a large-diameter gear and a small-diameter gear arranged coaxially, and explains how to measure the angle between the dummy reference lines. Fig. 7(B) is a photograph of the exterior of a measuring machine equipped with a camera-equipped microscope that measures the angle between the dummy reference lines. [Figure 8] Fig. 8(A) is a schematic perspective view of a rotary table on which a large-diameter gear and a small-diameter gear are placed, each held coaxially in a jig. Figs. 8(B) and 8(C) are photographs of the exterior of an example rotary table and hand press that can be used in this embodiment. Figs. 8(D) and 8(E) are schematic vertical cross-sectional views of a large-diameter gear and a small-diameter gear that are held coaxially in a jig set between the rotary table and the hand press. Fig. 8(D) shows the state before the large-diameter gear and the small-diameter gear are joined, and Fig. 8(E) shows the state after the large-diameter gear and the small-diameter gear are joined. [Explanation of symbols]

[0018] 1...large diameter gear, 1a...inner opening of large diameter gear, 1b...thickening hole, 1d...dummy reference of large diameter gear, 1r...reference of large diameter gear (tooth profile center point), 2...small diameter gear, 2a...inner opening of small diameter gear, 2d...dummy reference of small diameter gear, 2p...central protrusion of small diameter gear, 2r...reference of small diameter gear (tooth profile center point), 3...step gear, 10...jig for large diameter gear, 10a...inner opening of jig for large diameter gear ,10p...Central protrusion of jig for large diameter gear, 11...Coaxial alignment pin, 12...Locating pin, 20...Jig for small diameter gear, 20a...Inner opening of jig for small diameter gear, 20m...Notch, 22...Locating pin, 23...Coaxial alignment bolt, 30...Rotary table, 30a...Rotating part, 31...Coaxial recess, 40...Hand press machine, 40a...Jig holding part of hand press machine, Cc...Rotation axis BEST MODE FOR CARRYING OUT THE INVENTION

[0019] The present invention will now be described in detail with reference to some preferred embodiments thereof with reference to the accompanying drawings, in which like reference numerals indicate like parts.

[0020] Forming and phasing stepped gears The method according to this embodiment is applied to the case where two gears, a large gear 1 and a small gear 2, which have different diameters, are coaxially connected as shown in Fig. 1(A) to form a stepped gear 3 as shown in Fig. 1(B). When forming such a stepped gear 3, typically, for example, a protrusion 2p coaxial with the rotation axis of the small gear 2 may be fitted into an inner opening 1a of the large gear 1, which is coaxial with the rotation axis. Note that, conversely to the illustrated example, a protrusion may be formed on the large gear 1, and this protrusion may be fitted into an opening formed in the small gear 2 (the hole 1b formed in the large gear 1 is a lightening hole).

[0021] As described above, when the large gear 1 and the small gear 2 are coaxially connected to form the stepped gear 3, as already mentioned, it may be required that the rotational positions of the tooth rows of the large gear 1 and the small gear 2 are aligned as designed, i.e., "phase alignment." For this reason, as shown in FIG. 1(C), for each of the large gear 1 and the small gear 2, if the reference position r of the tooth row is set to, for example, the center point r of the tooth profile (for example, the midpoint of the intersection points pL, pR of the pitch circle pc of the gear and the left tooth Lt and the right tooth Rt), and the tooth profile central axis, which is the line connecting the center point r to the rotation axis of the gear, is set to be the reference line (hereinafter referred to as the tooth row reference line), then, as shown in FIG. 1(D), when the large gear 1 and the small gear 2 are arranged coaxially, the tooth row reference lines (tooth profile central axes) 1t, 2t of the large gear 1 and the small gear 2 are adjusted in the rotational direction relative to the other so that they substantially coincide with each other, or so that the angle of the tooth row reference line is within an appropriately set tolerance.

[0022] As already mentioned, conventional methods for "aligning the phases" between the large-diameter gear 1 and the small-diameter gear 2 include drilling holes (pin holes) in each gear to allow pins to be inserted, forming knock pins in the pin holes of each gear, and then placing the two gears on a jig that holds the two gears so that the phases of the two gears are aligned when the gears are placed on the jig. However, with this method using knock pins, it becomes difficult to form the knock pins in accurate positions on the jig as the gear diameters become smaller. This makes it difficult to use this method for aligning the phases of small-diameter stepped gears. Furthermore, although the tooth row reference lines of the large-diameter gear 1 and the small-diameter gear 2 can be identified in images captured by a camera using a tooth profile measuring machine or a three-dimensional measuring machine, they cannot be identified visually. Therefore, it is not possible (or extremely difficult) to visually adjust the angular positions of the reference lines of the two gears to align the phases of the gears.

[0023] How to connect large and small diameter gears (a) Overview In view of the above, in this embodiment, as described in the Summary of the Invention, to align the phases of the large-diameter gear and the small-diameter gear, first, dummy references are provided or formed as optically recognizable marks, i.e., marks that can be visually or camera-visible from the outside, on a plane perpendicular to the rotation axes of the two coupled gears. Then, for each gear, the angle between a dummy reference line connecting the center point or representative point of the dummy reference to the rotation axis of the gear and a tooth row reference line serving as a reference for the tooth row, which may be, for example, the tooth profile central axis, is measured. By identifying the center point or representative point of the dummy reference, the position of the tooth row reference line can be determined. Furthermore, when the large-diameter gear and the small-diameter gear are arranged coaxially, the angle between the tooth row reference lines of the large-diameter gear and the small-diameter gear can be determined from the angle between the dummy reference lines of the large-diameter gear and the small-diameter gear, as described below. Thus, in this embodiment, when the large-diameter gear and the small-diameter gear are arranged coaxially to be connected to each other, the center points or representative points of the dummy reference lines of the large-diameter gear and the small-diameter gear are identified, and the angle between the dummy reference lines is measured. Then, one of the large-diameter gear and the small-diameter gear is rotated relative to the other so that the angle between the dummy reference lines becomes an angle that brings the angle between the tooth row reference lines of the large-diameter gear and the small-diameter gear within a predetermined tolerance (the target value of the angle between the dummy reference lines), i.e., so that the difference between the current angle between the dummy reference lines and the target value is eliminated. This achieves phase alignment between the large-diameter gear and the small-diameter gear. Then, the large-diameter gear and the small-diameter gear are connected in this state. Each step of this embodiment will be described in detail below.

[0024] (b) Attaching a dummy reference line and measuring the angle between the dummy reference line and the dental reference line As shown in FIG. 2(A), the dummy reference 1d is provided or formed on a plane perpendicular to the rotation axes of the two gears. Although not shown, a similar dummy reference 1d is provided or formed on the small-diameter gear. The dummy reference 1d may typically be a circular hole, as shown in the figure. However, as long as its center point or representative point can be identified using a camera image of a tooth profile measuring instrument or a three-dimensional measuring machine (described below), the dummy reference 1d may be provided or formed in any shape, size, or position. It may also be a through hole or a blind hole. Once such a dummy reference 1d is provided or formed, as shown in FIG. 2(B), the angle δ1 between the dummy reference line Ldr, which is a line connecting the center point or representative point 1dc of the dummy reference 1d to the rotation axis Cc of the gear, and the tooth reference line Lr, which may be the tooth profile central axis, can be measured to identify the center point or representative point 1dc of the dummy reference 1d, thereby determining the angular position of the tooth reference line Lr about the rotation axis Cc.

[0025] The rotation axis Cc of each gear, the center point or representative point 1dc of the dummy reference 1d, the reference portion 1r of the tooth row (in the case of a small diameter gear, the center point or representative point 2dc of the dummy reference 2d, and the reference portion 2r of the tooth row), and the angle δ1 between the dummy reference line Ldr and the tooth row reference line Lr (δ2 in the case of a small diameter gear) may be identified and measured using a microscope image captured by a camera such as a tooth profile measuring machine. In this case, the position of each point is identified by coordinates set in the image. More specifically, as shown in Figures 2(C) and (D), the position of the rotation axis Cc can be determined by selecting any three points x1, x2, and x3 on the circle XC of the inner opening of the gear, and calculating their coordinate values ​​as follows: Equation of a circle: (xa) 2 +(yb) 2 =c 2 …(1) and calculate (a, b). If the dummy reference 1d is circular, the center point 1dc can be determined by selecting three arbitrary points y1, y2, and y3 on the circle yc of the dummy reference 1d, substituting their coordinate values ​​into the equation of the circle, and calculating (a, b). The reference portion 1r of the tooth row, in the case of the tooth profile center point, can be determined as the midpoint by identifying the intersections of the pitch radius circle with the left tooth and the right tooth from the position of the rotation axis Cc (see FIG. 1(C)). The angle δ1 between the dummy reference line Ldr and the tooth row reference line Lr can be determined using the cosine theorem or similar from the coordinate values ​​of the rotation axis Cc, the center point or representative point 1dc of the dummy reference 1d, and the reference portion 1r of the tooth row. If the above measurements are performed using a camera-equipped microscope equipped on a tooth profile measuring instrument, the position and angle of each point can be determined with an accuracy of several microns.

[0026] (c) Relationship between the angle between the dummy reference lines and the angle between the dental reference lines As described above, when the angles δ1 and δ2 between the dummy reference line Ldr and the tooth row reference line Lr (the angle from the tooth row reference line Lr to the dummy reference line Ldr) of the large gear 1 and the small gear 2 are determined, when the large gear 1 and the small gear 2 are arranged coaxially, as shown in FIG. 3 (the angle value is positive in the counterclockwise direction), the angle Δr between the tooth row reference line from the small gear 2 to the large gear 1 can be calculated using the angle Δd between the dummy reference lines from the small gear 2 to the large gear 1, and the angles δ1 and δ2, as follows: Δr=Δd-δ1+δ2 …(2) Therefore, when the large gear 1 and the small gear 2 are arranged coaxially, if the large gear 1 or the small gear 2 is rotated so that the angle Δd between the dummy reference lines is an angle that makes Δr fall within an appropriate tolerance, the phase alignment between the large gear 1 and the small gear 2 can be achieved.

[0027] (d) Holding large diameter gear 1 and small diameter gear 2 with a jig When connecting the large gear 1 and the small gear 2, they are each held in a dedicated jig. Referring to Figures 4(A) to (C), the large gear 1 may be held on a jig 10 as shown. The jig 10 may be roughly disk-shaped and has a circular opening 10a in its center with the same diameter as the inner opening of the large gear 1. When the large gear 1 is placed on its upper surface, a positioning pin 12 that prevents angular displacement protrudes from the outer periphery toward the center and abuts against the outer periphery of the large gear 1. In addition, the bottom surface of the jig 10 is formed with a circular protrusion 10p that fits concentrically into the central opening of the rotating part 30a (see Figure 8) of the rotary table 30, which will be described later. When the large gear 1 is held by the jig 10, the large gear 1 is placed on the jig 10, and the coaxial alignment pin 11 is inserted through the opening 1a of the large gear 1 and the opening 10a of the jig 10, as shown in Figure 4(C), thereby coaxially aligning the large gear 1 and the jig 10. In this state, the positioning pin 12 abuts against the outer periphery of the large gear 1, restricting circumferential and horizontal movement of the large gear 1 relative to the jig 10. The coaxial alignment pin 11 is then removed.

[0028] 5(A) to 5(C), the jig 20 that holds the small gear 2 is a substantially disk-shaped member having an opening 20a at its center that has the same diameter as the inner opening 2a of the small gear 2. When the small gear 2 is placed coaxially on the jig 20, a positioning pin 22 that prevents angular displacement from the outer periphery protrudes toward the center and abuts against the outer periphery of the small gear 2. The jig 20 also has a notch 20m, which may be fan-shaped, so that a dummy reference on the small gear 2 can be seen from the outside while the small gear 2 is held. When the small gear 2 is held by the jig 20, the small gear 2 is placed on the jig 20, and a coaxial alignment bolt 23 (see FIG. 6(A)) is inserted from the opening 20a of the jig 20 to the opening 2a of the small gear 2, thereby coaxially aligning the small gear 2 and the jig 20. In this state, the positioning pin 22 abuts against the outer periphery of the small diameter gear 2, and circumferential and horizontal movements of the small diameter gear 2 relative to the jig 20 are restricted.

[0029] Thereafter, as shown in FIG. 6, jig 20 holding small gear 2 is placed on jig 10 holding large gear 1 so that protrusion 2p of small gear 2 abuts against opening 1a of large gear 1. At this point, the tip of coaxial alignment bolt 23 engages with the small diameter portion of opening 10a of jig 10, thereby achieving coaxial alignment between large gear 1 and small gear 2. Coaxial alignment bolt 23 may be a hexagon socket head bolt. At this point, dummy references 1d and 2d of large gear 1 and small gear 2 can be seen from above jig 20, as shown in FIG. 6(B).

[0030] (e) Measurement of the angle between the dummy reference lines As described above, when the large gear 1 and the small gear 2 are held on the jigs 10 and 20 and arranged coaxially, the angle Δd between the dummy reference lines of the large gear 1 and the small gear 2 is measured. This measurement can be performed using a camera-equipped microscope attached to a tooth profile measuring instrument (for example, the Keyence One-Shot 3D Profile Measuring Instrument VR-3200, FIG. 7(B)). In the measurement, as in the above, the positions of the rotation axes Cc of the large gear 1 and the small gear 2 and the center points or representative points 1dc and 2dc of the dummy reference lines of the large gear 1 and the small gear 2 are identified by coordinate values, as shown in FIG. 7(A), and the angle Δd between the dummy reference lines may be calculated from these coordinate values ​​using the cosine theorem or the like. Here, the target value Δrt of the angle Δr between the tooth row reference lines in the phase alignment between the large diameter gear 1 and the small diameter gear 2 is given by the following equation (2): Δdt=Δrt+δ1-δ2 …(3) Therefore, if one of the large gear 1 and the small gear 2 is rotated around the rotation axis relative to the other so as to eliminate the difference Δd-Δdt between the current angle between the dummy reference lines Δd and the target value Δdt, the angle Δr between the tooth row reference lines will become the target value Δrt, and phase alignment between the large gear 1 and the small gear 2 will be achieved.

[0031] (f) Phase alignment of large diameter gear 1 and small diameter gear 2 Thus, in phasing the large gear 1 and the small gear 2, one of the large gear 1 and the small gear 2 is rotated about the rotation axis relative to the other so that the current angle Δd between the dummy reference lines between the large gear 1 and the small gear 2 coincides with its target value Δdt. The rotation of the large gear 1 or the small gear 2 may be performed in any manner. In one manner of this embodiment, as shown in Figures 8(A) and 8(D), either the jig 10 for the large gear 1 or the jig 20 for the small gear 2 may be coaxially mounted on a rotating portion 30a of a general-purpose rotary table 30 (Figure 8(B)), and the other may be held by a holding portion 40a of a hand press machine 40 (Figure 8(C)). In this state, the rotating portion 30a of the rotary table 30 may be rotated so that the current angle Δd between the dummy reference lines coincides with its target value Δdt. In the illustrated example, a protrusion 10p on the underside of the jig 10 for the large-diameter gear 1 and a coaxial recess 31 in the central region of the top surface of the rotating part 30a of the rotary table 30 form a spigot-joint structure. When the protrusion 10p fits into the coaxial recess 31, the rotation axis of the rotating part 30a aligns with the rotation axis Cc of the large-diameter gear 1, thereby achieving coaxial alignment between the rotating part 30a and the large-diameter gear 1 and the small-diameter gear 2. Then, the rotating part 30a is rotated by the difference Δd-Δdt between the current angle between the dummy reference lines Δd and the target value Δdt, thereby achieving phase alignment between the large-diameter gear 1 and the small-diameter gear 2. For example, if the indexing accuracy of the rotary table's rotation is within 1 minute 30 seconds, the angle error in the rotational direction can be kept within 0.025°. As an example of an application of stepped gears, the phase tolerance of a two-stage planetary gear is 0.15° or less, so the above angle error is fully acceptable.

[0032] (g) Connection between large diameter gear 1 and small diameter gear 2 Thus, when the phases of the large gear 1 and the small gear 2 are aligned, the large gear 1 and the small gear 2 are connected together. In the illustrated example, as shown in Figure 8(E), the holding portion 40a of the hand press 40, which holds the small gear 2 via the jig 20, is driven in the direction P toward the large gear 1, and the protruding portion 2p of the small gear 2 is pressed into the opening 20a of the large gear 1, thereby connecting the large gear 1 and the small gear 2 together.

[0033] The phase of the gears after coupling can be confirmed by observing the dummy reference as described above and measuring the angle Δd between the dummy reference lines while the gears are held in the jigs 10 and 20 (this has the advantage that it can be confirmed without removing the gears from the jig. Previously, the phase of stepped gears could only be confirmed using a tooth profile measuring machine or a 3D measuring machine installed in a constant temperature room).

[0034] As described above, in the method of this embodiment, dummy reference lines 1d and 2d are applied to the large-diameter gear 1 and the small-diameter gear 2 to be connected, respectively, and the angle between the dummy reference line and the tooth row reference line is measured. Then, with the gears mounted coaxially on a jig, one gear is rotated relative to the other so that the angle Δd between the dummy reference lines becomes the target value, thereby achieving phase alignment between the gears. This configuration eliminates the need for a precise knock pin on the jig. Furthermore, as mentioned above, the dummy reference lines may be applied or formed at any position as long as they are visible from the outside, and there are no restrictions on their positioning, which is advantageous in that they are easy to process. Furthermore, by measuring with high precision the angle between the dummy reference line and the tooth row reference line of each gear and the angle between the dummy reference lines of the coaxially mounted gears, and then rotating one of the coaxially mounted gears with high precision relative to the other, it is possible to minimize phase errors.

[0035] The above description has been made in relation to the embodiments of the present invention, but it will be apparent that many modifications and changes will be readily apparent to those skilled in the art, and the present invention is not limited to the above-exemplified embodiments, but can be applied to various devices without departing from the concept of the present invention.

Claims

1. A method for manufacturing a stepped gear by coaxially connecting a large diameter gear and a small diameter gear, comprising the steps of: providing a dummy reference, which is an optically recognizable mark, on a plane perpendicular to the rotation axis of each of the large diameter gear and the small diameter gear; measuring an angle between a reference line connecting a reference portion set based on a tooth profile of each of the large-diameter gear and the rotation axis and a dummy reference line connecting the dummy reference and the rotation axis, for each of the large-diameter gear and the small-diameter gear; calculating a target value of an angle between the dummy reference lines of the large-diameter gear and the small-diameter gear, the target value being an angle between the reference lines of the large-diameter gear and the small-diameter gear when the large-diameter gear and the small-diameter gear are arranged coaxially; a step of coaxially arranging the large diameter gear and the small diameter gear, each mounted on a jig; measuring an angle between the dummy reference lines of the large diameter gear and the small diameter gear; rotating one of the large-diameter gear and the small-diameter gear relative to the other about the rotation axis so that the angle between the dummy reference lines becomes the target value; connecting the large diameter gear and the small diameter gear; A method comprising:

2. 2. The method of claim 1, wherein the jig is configured so that the large-diameter gear and the small-diameter gear are coaxially arranged so that one can rotate relative to the other with the connecting portion of the large-diameter gear held by the jig and the connecting portion of the small-diameter gear held by the jig abutting against each other.

3. 2. The method of claim 1, wherein the angle between the dummy reference lines of the large-diameter gear and the small-diameter gear placed on the jig is measured using a microscope image of the dummy reference lines of the large-diameter gear and the small-diameter gear photographed by a camera.

4. 2. The method of claim 1, wherein one of the jigs holding the large-diameter gear and the small-diameter gear is coaxially mounted on a rotary table, the other of the jigs is held by a hand press, and the rotary table is rotated relative to the hand press, thereby rotating one of the large-diameter gear and the small-diameter gear relative to the other about the rotation axis.

5. 2. The method of claim 1, wherein said large gear and said small gear are coaxially aligned using a bolt extending along said axis of rotation.

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