JP5701177B2 - Internal spline gear with special missing teeth - Google Patents

Description

The present invention relates to an internal spline gear in which spline teeth are formed on an inner peripheral surface of a cylindrical portion. Specifically, the input side shaft and the output side shaft arranged in series on the same shaft center are coupled via spline teeth, and the spline fitting structure used for a vehicle power transmission device, a rotating shaft of a general mechanical device, or the like. The present invention relates to a long-shaft internal spline gear that is a body and has special internal teeth formed by forging on the inner peripheral surface of a cylindrical portion. The spline fitting structure includes a shaft having an outer spline formed on the outer peripheral surface and a joint member having an inner spline formed on the inner peripheral surface. Then, the shaft is fitted into the joint member by press-fitting to enable power transmission between them. Generally, key coupling or spline coupling is applied as a power transmission device between the input side shaft and the output side shaft. In the power transmission device using the key, there is a problem that the rotational balance is lost or stress is concentrated on the key part. On the other hand, the spline teeth form key-like irregularities on the shaft directly over the entire circumference at equal intervals, so that the coupling force becomes strong, and a large torque can be transmitted to withstand heavy loads. Further, since there is no eccentricity between the shaft and the boss, it is advantageous when there is a centripetal force during rotation and rotation balance is required. Therefore, spline coupling is adopted in a power transmission device. For example, in an automobile in which a propeller shaft is divided into front and rear shafts, an inner spline portion and an outer spline portion that are press-fitted to each other are formed on the front and rear shafts. . Also, in a power transmission system such as an automobile transmission or a differential, in many cases, an input side shaft and an output side shaft arranged in series on the same axis are coupled via a spline. By the way, if the runout of the inner and outer splines with respect to the shaft center of each axis is out of specification, vibration and noise are generated when the vehicle travels and the comfort of the vehicle is impaired. Therefore, it is essential to improve the accuracy of the tooth profile.

In the inner spline teeth in which the spline portion is formed on the inner peripheral surface of the cylindrical portion, the spline teeth are arranged at equal pitch intervals over the entire inner periphery, and these spline teeth are usually cut by machining. An example of the inner spline teeth is shown as a partial sectional view in FIG. The cylindrical portion 1 stands upright with respect to the flat flange 3 extending outward, and the shaft hole 5 passes through the center thereof. Then, a circumferential row of the inner spline teeth 2 is formed concentrically at a portion expanded in diameter along the shaft hole 5, and the regular teeth 21 are arranged. Such internal spline teeth cannot be cut with a hob cutter, but can be cut with a pinion cutter. In the case of a pinion cutter, it is possible to cut gears while rotating and revolving the cutter, and to cut teeth with missing teeth. However, the number of teeth of the workpiece is limited because the number of pinion cutters, which is smaller than the number of teeth of the inner spline teeth that are the workpiece, is not used. Further, when generating or cutting internal teeth with a pinion cutter, if interference or trimming occurs, the tool may be damaged due to escape interference when the pinion cutter escapes from the internal spline teeth. Thus, there is a problem in cutting the internal spline teeth having regular teeth or missing teeth by machining.

Therefore, attempts have been made to form inner spline teeth by forging and to provide missing teeth in the circumferential row, as shown in FIG. The overall configuration is shown in part (a) as a partial cross-section, and the inner spline teeth W have a flange 3 that extends upward, a cylindrical portion 1 that stands up below and projects downward, and a shaft hole 5 passes through the inside. . Near the flange 3 of the shaft hole 5, a circumferential row of the inner spline teeth 2 is formed in the axial direction in a portion that is slightly larger in inner diameter. A chamfered portion 23 having an inclined surface is provided at the lower part of the circumferential row of the inner spline teeth 2, and a stepped portion 24 serving as a dented hole is provided at the lower portion thereof. 22 is formed. A peripheral row of regular teeth 21 of the inner spline teeth 2 is formed by forging, and at the same time, missing teeth 22 are also formed. During the formation of spline teeth by forging, the portion of the missing tooth 22 in the circumferential row of the regular teeth 21 has a difference in thickness volume from the adjacent regular teeth 21, so that forging pressure is applied. At this time, the meat flow is disturbed, and the surplus thickness 25 protrudes from the portion of the step portion 24 below the inner spline teeth 2. The details of this state are shown in a partial cross-section in FIG. 4B, and the periphery is composed of a chamfered portion 23 below the missing tooth 22 and a stepped portion 24 therebelow. You can see that it is being pushed out. Further, this state is shown in a perspective view of FIG. This extra thickness 25 is likely to occur when the axial length L of the step portion 24 below the circumferential row of the inner spline teeth 2 is short. For this purpose, the axial length L of the stepped portion 24 must be extended and enlarged, and the effective length of the inner spline teeth 2 must be reduced accordingly, so that the power transmission strength is reduced. . On the other hand, in order to keep the power transmission strength above a certain value, the predetermined effective length of the inner spline teeth 2 must be secured. Accompany. In addition, other defects occur when the missing teeth 22 are formed. The state is shown in FIG. 15, and the portion indicated by the arrow XX in FIG. 14 is enlarged in order to enlarge the defective portion. In FIG. 1A, which is a partial perspective view around the inner spline teeth 2, a circumferential row of the inner spline teeth 2 is shown at the center of the cylindrical portion 1. A missing tooth 22 sandwiched between the right and left regular teeth 21 in the circumferential row of the spline teeth 2 is formed in the axial direction, a wound 26 is generated at the root of the regular tooth 21, and a surplus thickness 25 is formed below the wound 26. It protruded. The state of occurrence of this scratch is shown in an enlarged perspective view in FIG. It can be seen that scratches 26 and 26 are generated in the lower part in the axial direction S on the missing tooth 22 side of the tooth surfaces of the right and left regular teeth 21 and 21. Further, FIG. 3C shows the situation of the occurrence of scratches as a partial cross-sectional view of the lower part in the axial direction S on the left and right sides of the missing tooth 22. Scratches 26 and 26 are generated in the lower part in the axial direction S of the right and left regular teeth 21 and 21 at the center missing tooth 22. The mechanism of the generation of this flaw is that when the peripheral row of the inner spline teeth 2 is forged, the portion of the missing tooth 22 is strongly pressed, and is pulled by this to pressurize the right and left adjacent regular teeth 21, 21. The balance is lost, and scratches occur on the tooth surfaces of the regular teeth 21 and 21 adjacent to the left and right. These flaws become fatal defects as internal spline teeth, while the mold is damaged with the occurrence of these flaws.

By the way, the following proposals have been made regarding the inner spline teeth. That is, it is an object of the present invention to provide an internal spline gear and a method of manufacturing the same that can eliminate the deburring process and reduce the processing cost, and have a cylindrical portion provided with a through hole, and an inner periphery of the cylindrical portion. In the inner spline gear having a spline portion in which crest portions provided along the axial direction on the surface and trough portions provided between the crest portions are alternately provided, on one end portion side of the cylindrical portion, A ring-shaped remaining portion having an inner diameter dimension that is the same or smaller than the inner diameter dimension of the peak portion and having a substantially circular inner peripheral surface shape is provided, and the valley portion is open on the other end side in the axial direction. And an inner spline gear that is closed by the ring-shaped remaining portion on the one end side. The main spline gear has the spline portion on the inner peripheral surface of the cylindrical portion and the ring-shaped remaining portion. Moreover, the one end part side of the trough part of a spline part is closed by the said ring-shaped remaining part. In the main spline gear, the trough portion of the spline portion is not provided to penetrate both ends, but one end portion side is closed. By adopting such a structure, when the inner spline gear is manufactured, it is not necessary to open the valley on the one end side, so that the generation of burrs can be prevented and the deburring process is unnecessary. Become. Therefore, the processing cost can also be reduced. (For example, refer to Patent Document 1).

JP 2004-34037 A

As described above, the conventional inner spline member has the following problems.

Problems when the inner spline teeth are formed by machining are as follows. When using a pinion cutter as a tool, it is possible to cut gears while rotating and revolving the cutter. In this case, the pinion has fewer cutters than the number of spline teeth on the workpiece. Since a cutter must be used, the number of teeth on the workpiece is limited. Further, when generating or cutting internal teeth with a pinion cutter, when interference or trimming occurs, there is a risk of damage to the tool due to escape interference when the pinion cutter escapes from the internal spline teeth. On the other hand, problems when the inner spline teeth are formed by forging are as follows. During the formation of spline teeth by forging, the missing tooth part in the circumferential row of regular teeth is disturbed by the forged meat flow when pressure is applied due to the volume difference from the adjacent regular teeth, and the inner spline A surplus portion is generated at the stepped portion below the teeth. This surplus is likely to occur when the axial length of the step portion below the circumferential row of the inner spline teeth is short. Therefore, the axial length of the stepped portion must be extended and enlarged, and the effective length of the inner spline tooth portion must be reduced accordingly, and as a result, the power transmission strength decreases. On the other hand, in order to ensure the strength of power transmission, the axial length of the inner spline teeth must be ensured, which involves a design change such as increasing the total axial length of the inner spline gear. In addition, defects occur when forming missing teeth. When forging the circumferential row of inner spline teeth, the missing tooth part is strongly pressurized, and this causes the pressure balance in the right and left adjacent normal teeth to be lost, causing damage to the tooth surface of the right and left adjacent normal teeth. Produce. These flaws are fatal defects as internal spline teeth, while the mold is damaged with the occurrence of these flaws.

Therefore, the present invention has been made paying attention to the problems as described above, and is basically based on finishing by forming a peripheral row of inner spline teeth by forming by cold forging. To do. By combining the mold technology for forming the special tooth shape developed by the applicant and the molding technology by forging, the inventor of the present application can install a spline member having a special shape missing tooth in the regular periodical row of the inner spline teeth. The technology for forging formation was completed. The invention of the present application integrally forms the outer spline teeth and the inner spline teeth by hot forging and cold forging, and does not cause a defect such as a surplus or a flaw at the root of the inner spline teeth and is later machined. An object of the present invention is to provide a long-axis spline member that does not require gear cutting. The object of the present invention is to improve the strength of the spline teeth by eliminating the machining of the inner spline teeth, leaving a fiber structure called fiber flow by forging, and at all of the tooth tip, tooth surface and tooth bottom. An object of the present invention is to provide a spline member whose strength is improved by performing full R chamfering on the ridgeline.

In recent years, with the advance of forging technology, it has become possible to form variously shaped gears by forging and omit machining. Therefore, the inventors of the present application pay attention to equalizing the forged meat flow around the inner spline teeth, and make use of the fiber flow formed by hot forging as it is, and the gear cutting after cold forging. A prototype spline member without processing was found to have excellent tooth durability. Further, the inventors of the present application form the chamfered portion by forging at each ridge line portion at the intersection of the root surface, the tooth surface and the tip surface of the inner spline teeth and the end surface in the axial direction of the gear. As a result of further research and development after focusing on the technical idea of the above, it is not necessary to perform machining to remove burrs caused by conventional hobbing, so strength reduction is prevented and machining costs are reduced. The present invention that achieves the above-described object has been achieved. The internal spline gear of the present invention is embodied on the basis of such knowledge, and the invention of claim 1 is formed by forging in an internal spline gear provided with a plurality of missing teeth in the circumferential row of regular teeth. Thus, the inner spline gear is configured to evenly distribute the forged meat flow, and is provided with a protrusion at the center of the inner periphery of the missing tooth.

According to the invention of the present application, it becomes possible to simultaneously form the missing teeth in the regular periodical row of the inner spline teeth by cold forging. Therefore, the following effects can be obtained. By reducing the difference in these geometric cross-sectional dimensions between the left and right regular teeth of the missing tooth, it is possible to equalize the forged meat flow. The difference in pressure balance between the adjacent regular teeth is reduced. As a result, it has been confirmed that there is no surplus in the root of the missing tooth, or no flaw in the tooth surface of the regular tooth. In addition, since the outer spline teeth and the inner spline teeth are integrally formed by hot forging and cold forging, there is no need to machine the root of the teeth after that, and the fiber flow by forging may be cut. The strength of the gear can be improved, and at this time, the fiber flow remains densely formed inside the teeth of the full R chamfered portion, so that the bending strength at the tooth base is improved. In addition, all ridges formed by intersecting the tooth surface, tooth tip surface, tooth bottom surface or tooth end surface remain cold forged, and full R chamfered portions without corners are applied to prevent strength reduction. In particular, since the full R chamfered portion that is still cold forged is also applied to the ridge line portion of the tooth bottom surface, there is an effect of avoiding stress concentration without causing a step. In addition, since gear cutting is not required, the material yield is improved and the manufacturing cost can be reduced.

Example 1 of the present invention is shown and is a manufacturing process diagram of an inner spline tooth having a missing tooth. It is sectional drawing of the metal mold | die which concerns on the forging of the inner spline tooth | gear which has a missing tooth same as the above. It is a figure of the counter punch which forms an internal spline tooth | gear which has a missing tooth same as the above by forging. It is a perspective view which shows an example of an inner spline tooth | gear which has an outer spline tooth | gear on the outer periphery and an inner spline tooth | gear on the inner side same as the above. FIG. 3 is an enlarged view of a circumferential row of inner spline teeth having a missing tooth in FIG. It is a partial cross section enlarged view of a missing tooth same as the above. It is a partial cross-sectional enlarged view of the missing tooth of another shape same as the above. It is a partial cross-sectional enlarged view of the missing tooth of another shape same as the above. It is a partial cross-sectional enlarged view of the missing tooth of another shape same as the above. It is a partial cross-sectional enlarged view of the missing tooth of another shape same as the above. It is a schematic diagram which shows distribution of the fiber flow in forging same as the above. It is a perspective view which shows the detail of the chamfering in the tooth end surface site | part in an inner spline tooth | gear same as the above. It is a partially cutaway sectional view of an inner spline tooth according to a conventional example. It is explanatory drawing which shows the defect of the internal spline tooth | gear which has a missing tooth same as the above. It is another defect figure of the inner spline tooth | gear which has a missing tooth same as the above.

Embodiments of the present invention will be specifically described below based on examples of the present invention illustrated in the accompanying drawings.

The present embodiment will be described with reference to FIGS. FIG. 1 is a manufacturing process diagram of an inner spline tooth having a missing tooth. FIG. 2 is a perspective view showing an example of inner spline teeth having outer spline teeth on the outer periphery and inner spline teeth on the inner side. FIG. 3 is an enlarged view of a circumferential row of inner spline teeth having a missing tooth. FIG. 4 is a cross-sectional view of a mold for forging inner spline teeth having missing teeth. FIG. 5 is a view of a counter punch for forming inner spline teeth having missing teeth by forging. FIG. 6 is an enlarged partial sectional view of a missing tooth. 7, 8, and 9 are enlarged partial cross-sectional views of other shapes of missing teeth. FIG. 10 is an enlarged partial cross-sectional view of another shape of a missing tooth. FIG. 11 is a schematic diagram showing a fiber flow distribution in forging. FIG. 12 is a perspective view showing details of chamfering at a tooth end surface portion of the inner spline tooth.

The manufacturing process of the transmission gear of the present embodiment will be described based on the process diagram of FIG. First, as shown in step (1), a material W1 is obtained by cutting a cylindrical material suitable for a transmission gear into a predetermined axial length by, for example, a billet shear. In this case, a steel material suitable for a transmission gear, for example, SC steel, SCR steel, SCM steel, SNC steel, SNCM steel, or the like can be used as the material of the material. Next, as shown in step (2), the raw material W1 is heated to, for example, 1150 ° C. and subjected to hot forging to form a convex portion W22 on the lower side, and a large diameter portion D1 in the middle portion and a small diameter in the lower portion A material W2 having a part D2 is obtained. Next, as shown in the step (3) by hot forging, a recess W31 is formed on the upper surface of the material W2 and flattened to enlarge the flange W32 to the diameter D3, and the cylindrical portion W32 to the lower side to the diameter D4. The diameter is reduced and extended downward to obtain a material W3. Next, as shown in the step (4) by hot forging, after removing the burr W34 on the outer periphery of the cylindrical portion W32, the recess W31 on the upper surface of the material W3 is further pressed deeply to form a recess W41 having an inner diameter d1. Further, it is flattened and the flange W42 is enlarged to the diameter D5, and the cylindrical portion W43 is reduced to the diameter D6 downward and extended downward. In this step, the outer spline rough teeth 40 are formed at the portion of the flange W42 having the diameter D5. In addition, the upper surface portion protrudes into a disk shape to the outer periphery to form a bowl-shaped burr W46 to obtain W4. Next, as shown in step (5), the burr W46 on the upper surface of the material W4 is removed by hot forging to obtain a material W5 having a flange W51. Next, in step (6), rough machining is performed to scrape off the upper surface A of the flange W51 of the material W5, and further through the central recess, the material W6 having the shaft hole 5 with the inner diameter d2 is obtained. Next, in step (7), the outer spline rough teeth 40 on the outer periphery are formed into the outer spline rough teeth 41 by cold sizing, and the material W6 having the outer spline teeth whose trapezoidal shape or involute is obtained. On the other hand, the rough dog-clutch teeth 20 on the inner circumference obtain a material W7 having a tooth surface formed straight by coining molding and a chamfer formed on the tooth tip. In the next step (8), the inner diameter d1 of the dent W41 formed in the step (4) is expanded to the inner diameter d3 by performing pilot hole machining, and a hole is formed that matches the diameter of the inner spline teeth in the subsequent step. Material W8 is obtained. Finally, in step (9), the outer spline teeth 4 are formed by subjecting the outer spline rough teeth 41 formed in step (7) to finish sizing by cold forging, while the inner spline teeth 2 are formed inside. After being subjected to extrusion molding by cold forging, it is finished by sizing molding. In summary, the steps (2), (3), (4) and (5) are hot forging, the steps (6) and (8) are machining, and the steps (7), ( 9) is cold forging.

Details of forming the inner spline teeth in the above-described step (9) will be described below with reference to FIG. The left half of the figure shows a state where the material W8 is set in a mold, and the right half of the figure shows a state where spline teeth are formed on the material W8. Next, this metal mold | die is divided into figure (a), (b), (c) from the top, and the structure of an up-down direction is demonstrated. The right half figure (a) shows the upper punch P2 incorporated in the upper ram A, the second stage figure (b) shows the outer die Q1, the inner die Q2 is set in the assembled die, A tooth mold T4 for forming outer spline teeth on the inner periphery is provided. A punch P2 fixed to the lower ram B is shown at the center of the die Q2, and a tooth die T2 for forming inner spline teeth is provided on the outer periphery of the upper end. In the third figure (c), a lower ram B that supports the die Q1, die Q2, etc., and an ejector P5 are provided so as to penetrate the center of the lower ram B.

As shown in the left half of the figure, the material W8 is set by aligning the outer spline rough teeth 41 of the material W8 with the tooth pattern T4 of the die Q2. Next, as shown in the right half of the figure, when the upper ram A is lowered in the direction of the arrow C, the upper punch P2 fixed thereto is also lowered. At the same time, the outer spline teeth 4 are formed by the cold finish sizing of the outer spline rough teeth 41 of the material W8 by the tooth mold T4 on the inner periphery of the die Q2 while pushing the material W8 downward by the descending upper punch P2. . On the other hand, the inner spline teeth 4 are formed coaxially with the outer spline teeth 4 by cold forging at the inner periphery of the material W8 while pushing the material W8 downward by the upper punch P2. When the inner and outer spline teeth are formed and the inner spline gear W is completed, it is pushed upward by the ejector P5 to complete the molding.

In the step (9), the shape of the upper punch used when forming the inner spline teeth by cold forging will be described with reference to FIG. FIG. 4A shows a side view and FIG. 2B shows a plan view. As shown in FIG. 5A, the punch P2 is a long-axis object, and has a tooth mold T2 that forms internal spline teeth at the tip of the long-axis shaft. As shown in the plan view of FIG. 2B, the tooth mold T2 is provided with tooth molds T22 for forming three missing teeth at equal pitches in the circumferential row of the tooth mold T21 for forming regular teeth.

FIG. 4 shows the detailed shape of the inner spline gear W that has been subjected to final finishing in this way. FIG. 1A shows a cross-sectional view, in which a cylindrical portion 1 stands upright with respect to a flat flange 3 that spreads outward, and a shaft hole 5 passes through this central portion. Then, a circumferential row of inner spline teeth 2 is formed concentrically at a portion expanded in diameter along the shaft hole 5, and an outer spline circumferential row 4 is formed on the outer periphery of the flange 3 concentrically therewith. A plan view of FIG. 4A is shown in FIG. 4B. A circumferential row of inner spline teeth 2 is formed concentrically on the outer side of the shaft hole 5 in the center, and concentrically with this, on the outer periphery of the flange 3. It can be seen that the outer spline circumferential row 4 is formed. In the circumferential row of the inner spline teeth 2, three teeth 22 having enlarged tooth gap widths are formed at an equal pitch. The formation of the missing teeth 22 is best in terms of geometry since there is only one heart in the case of three places. For this reason, since it is easy to pick up the heart when forming the missing teeth 22 by forging, the applied pressure is evenly applied to the tooth portion, which is preferable in terms of manufacturing method.

FIG. 5 shows an enlarged cross section of the circumferential row of the inner spline teeth 2 in FIG. Three missing teeth 22 are provided at equal pitch intervals between the circumferential rows of regular teeth 21 formed on the inner peripheral surface of the shaft hole 5. In addition, the formation of the missing tooth 22 may be 4, 5 or 6 places. On the contrary, it is bad when the missing tooth 22 is formed at two places, and is worst when it is formed at one place. The missing teeth thus formed serve as a passage for oil in the spline fitting structure with the outer spline teeth.

The inner spline gear W according to the present embodiment is configured as described above, and by forming the missing teeth, the forged meat flow in each section of the inner spline teeth is equalized, and the forged meat flow bottleneck is alleviated. Details will be described below.

In the case where the dimension of the outer diameter D0 of the inner spline gear W cannot be increased by design, four types of missing tooth shapes shown in FIGS. 6, 7, 8 and 9 are conceivable. Is constant. First, FIG. 6 shows an example in which a protrusion is provided in the tooth gap of the missing tooth, and the protrusion 221 is provided at the center of the tooth gap width G22 in the missing tooth 22. The tip of the protrusion 221 is retracted from the tip diameter D8 of the inner spline tooth 2. As described above, by providing the protrusion in the tooth gap of the missing tooth, the difference in the geometric volume in the cross-sectional thickness volume or the cross-sectional portion between the missing tooth and the right and left regular teeth is alleviated. Specifically, a missing tooth 22 is formed between the regular teeth 21 and 21, and a protrusion 221 is provided in the missing tooth 22. The idea of providing the protrusion 221 is that the protrusion 221 is retracted by the dimension H1 from the tooth tip diameter D8 and the width of the protrusion 221 is increased to be thick, whereby the virtual area indicated by a two-dot chain line lacking the cross-sectional area of the protrusion 221. The cross sectional area of the regular tooth 210 is equal. That is, by providing the protrusion 221 in the tooth gap of the missing tooth 22, the tooth gap widths G 21, 21 of the regular teeth 21, 21 adjacent to the left and right of the missing tooth 22 and the left and right tooth gap widths g 22, g 22 of the protrusion 221 are determined. Geometric dimensional differences between them are reduced. In this way, by making the cross section between the missing tooth and the right and left regular teeth as uniform as possible, during cold forging in step (9), the missing tooth and the right and left regular teeth The pressure balance between them is equalized. As a result, it was confirmed that there was no surplus on the bottom of the missing tooth or no flaw on the tooth surface of the regular tooth.

Next, FIG. 7 shows an example in which protrusions are similarly provided between the tooth gaps of the missing teeth, the root diameter of the missing teeth is reduced, and the tooth height of the protrusions is reduced. That is, the protrusion 222 is provided in the tooth gap of the missing tooth 22, and the root diameter D72 of the missing tooth 22 in this figure is smaller than the root diameter D7 in FIG. 6, and the dimension H2 in this figure is the dimension H1 in FIG. Greater than. The idea of providing the protrusion 222 is that the protrusion 222 is retracted by the dimension H2 from the tooth tip diameter D8, the width of the protrusion 221 is enlarged, and the tooth root diameter D72 of the protrusion 221 is smaller than the tooth root diameter D7. By doing so, the cross-sectional area of the virtual regular tooth 210 indicated by the two-dot chain line of the protrusion 222 is made equal. Thus, by providing a protrusion in the tooth gap of the missing tooth, the thickness volume or dimensional difference of the cross section between the missing tooth and the right and left regular teeth is geometrically relieved. In this way, by making the cross section between the missing tooth and the right and left regular teeth as uniform as possible, during cold forging, the pressure balance between the missing tooth and the right and left regular teeth Are equalized. As a result, it was confirmed that there was no surplus on the bottom of the missing tooth or no flaw on the tooth surface of the regular tooth.

Next, FIG. 8 shows an example in which the tooth gap width of the missing tooth is reduced without providing a protrusion in the tooth gap of the missing tooth. That is, the tooth gap width G223 in this figure is smaller than the tooth gap width G22 in FIG. In addition, the tooth tip diameter D8 and the tooth root diameter D7 in this figure are the same as FIG. The concept of this missing tooth is to make the cross-sectional area of the virtual normal tooth 210 indicated by the broken two-dot chain line to the cross-sectional area of the left and right parts Y8 and Y8 by making the tooth gap width G223 smaller than the tooth gap width G22 of FIG. It is in the place where it allocated. In this way, by reducing the gap width of the missing tooth, the thickness volume or dimensional difference of the cross section between the missing tooth and the right and left regular teeth is geometrically relieved. In this way, by making the cross section between the missing tooth and the right and left regular teeth as uniform as possible, during cold forging, the pressure balance between the missing tooth and the right and left regular teeth Are equalized. As a result, it was confirmed that there was no surplus on the bottom of the missing tooth or no flaw on the tooth surface of the regular tooth.

Finally, FIG. 9 shows an example in which protrusions are provided between the tooth gaps of the missing teeth and the tooth gap width of the missing teeth is reduced. That is, the tooth gap width G224 in this figure is smaller than the tooth gap width G22 in FIG. The concept of this missing tooth is that the tooth gap width G224 is made smaller than the tooth gap width G22 in FIG. 6 so that the cross-sectional integral of the virtual normal tooth 210 indicated by the broken two-dot chain line is the step area of the left and right middle part Y9. It is in the place allocated to the cross-sectional areas of the left and right parts Y91 and 91. Thus, by reducing the tooth gap width of the missing tooth and reducing the tooth height, the difference in the thickness volume or the geometric dimension of the cross section between the right and left regular teeth is alleviated. In this way, by making the cross section between the missing tooth and the right and left regular teeth as uniform as possible, during cold forging, the pressure balance between the missing tooth and the right and left regular teeth Are equalized. As a result, it was confirmed that there was no surplus on the bottom of the missing tooth or no flaw on the tooth surface of the regular tooth.

6, 7, 8, and 9, the difference in pressure balance between the missing tooth and the right and left regular teeth is reduced, and the forged meat flow in the missing tooth and regular tooth is equalized. The In consideration of forgeability, the case of FIG. 8 is best because the forged meat flow is equalized, and then the cases of FIGS. 9, 7 and 6 are preferred.

Unlike the case where the outer dimension of the inner spline gear W is fixed as shown in FIGS. 6, 7, 8, and 9, the case where the outer dimension of the inner spline gear W can be expanded by design is shown in FIG. The shape is considered, and a protrusion is provided outside the outline of the missing tooth. In FIG. 8, the tooth gap width of the missing tooth is the same as that in FIG. 6 without providing a protrusion in the tooth gap of the missing tooth. That is, the protruding edge 230 is provided outside the outer diameter D0 in this figure, and this thickness N1 is provided. In this way, by increasing the volume of the outline of the missing tooth, the difference in geometric dimension in the cross section of the thick volume or tooth profile that backs up the tooth gap between the right and left regular teeth is alleviated. The concept of this missing tooth is that the cross-sectional integral of the virtual regular tooth 210 indicated by the broken two-dot chain line is assigned to the cross-sectional area of the protruding edge 230 protruding outward. By reducing the geometric difference between the missing tooth and the right and left regular teeth in this way, the difference in pressure balance between the missing tooth and the right and left regular teeth is reduced, and the missing tooth, Forged meat flow in regular teeth is equalized. As a result, it was confirmed that there was no surplus on the bottom of the missing tooth or no flaw on the tooth surface of the regular tooth. 10 is most ideal because the forged meat flow is more uniform than in the case of FIGS. 6, 7, 8 and 9 in consideration of forgeability. However, since the outer dimension of the inner spline gear W has to be enlarged in design, it involves a significant design change around the spline teeth.

Since the inner spline teeth are formed by cold forging by sizing or extrusion, a flow of a fiber structure called a fiber flow is continuously formed along the tooth profile. Since the tooth groove of the inner spline teeth is not machined after forging, the fiber flow is not cut, and a gear having excellent bending fatigue strength and excellent durability can be obtained. The formation of this fiber flow will be described with reference to FIG. Inside the inner spline teeth formed by cold forging, a metal macro structure called fiber flow is formed in a fiber structure, and FIG. (A) schematically shows the distribution of fiber flow in the tooth form. A fiber flow F, which is a flow of the fiber structure, is formed in multiple layers along the hot forged tooth profile from the root to the outside. On the other hand, FIG. (B) schematically shows a state in which a flat forging material is cut by hobbing for comparison, and the fiber flow F is cut by the machined surface M at the tooth surface and the tooth bottom of the tooth profile. According to the present embodiment, since the tooth profile is still cold forging, the fiber flow F is not cut and a gear excellent in bending of the tooth root can be obtained. In other words, since the machining process after forging can be omitted, the productivity is high, and the fiber flow F is not cut, so that a gear having high mechanical strength can be obtained.

A part of the circumferential row of the inner spline teeth is shown in FIG. 12 as a perspective view in the direction of arrow K in FIG. The inner spline teeth formed in the present embodiment have a constant curvature radius R chamfer 112 having no corners on all ridges intersecting the tooth tip surface 11, tooth surface 12, tooth bottom surface 13 or tooth end surface 14. 121 and 131 are formed. Furthermore, R chamfers are similarly formed on all ridge lines in the tooth trace direction. In this way, a full R chamfered portion having a constant curvature radius without any corners is applied to all of the ridge lines. Since these full R chamfered portions are formed by a cold forging die, the degree of curvature radius can be given a degree of freedom. For example, it is possible to design the mold such that the chamfered portion of the chamfered portion of the tooth tip surface 11 is small, the chamfered portion of the tooth bottom surface 13 is large, and the chamfered portion of the ridge line portion between them has a gradually increased radius of curvature. . In this way, continuously changing the radius of curvature of the full R chamfered portion in the ridge line portion enables the die design to have an optimum shape in terms of strength because a cold forging die is used. . In the case of the conventional method in which machining is performed after forging, it is difficult to control the radius of curvature of the full R chamfered portion to an optimum size depending on the portion in the chamfered portion. Moreover, about the shape of these full R chamfering parts, a level | step difference can be eliminated in any site | part of a tooth tip surface, a tooth surface, and a tooth bottom by a cold forging die.

The inner spline teeth having the special missing teeth of the present invention can be applied as all machine elements for joint fitting. In automobiles, the range of application is wide as well as power transmission systems such as transmissions, propeller shafts, and differentials, as well as fitting fitting parts for driving a small load oil pump. In addition, the inner spline tooth of the long shaft object having a special missing tooth according to the present invention can be applied to various machine devices such as a machine tool, a cargo handling construction machine, and a robot. For example, in the case of an oil pump drive, the passage of oil is reduced, but an appropriate amount of oil can be sent. Therefore, the present invention having a protrusion in a groove of a missing tooth is effective as a gear for use in a metering pump.

A Upper ram, B Lower ram C, K Arrow D1 Large diameter part, D2 Small diameter part D3, D4, D5, D6 Outer diameter D0 Outer diameter, D7, D72 Tooth root diameter, D8 Tooth tip diameter d1, d2, d3 Inner diameter G21 , G22, G222, G223, G224 Tooth groove width F Fiber flow, M Machined surface P1 Upper punch, P2 Punch, P5 Ejector Q1, Q2 Dies T2, T21, T22 Tooth type L Thickness H1, H2, H4 Dimensions NI Thickness p Pressurizing force S Axial direction W Internal spline gear W1, W2, W3, W4, W5, W6, W7, W8 Material W22 Convex part, W31 Concave part, W32 Flange, W33 Cylindrical part, W34 Burr W41 Concave part W42 Flange, W43 Cylindrical part, W46 Burr W51 Flange 1 Cylindrical part 2 Inner spline tooth 21 Regular tooth, 22 Missing tooth, 23 Flank, 24 Stepped part, 25 Extra thickness, 26 Scratch 210 Temporary Regular teeth 221, 222, 223, 224 protrusions 230 projecting edge 3 flange 4 outside the spline teeth 41 outer splines Araha 5 holes 11 tooth crest 12 tooth surface 13 tooth bottom 14 tooth end face

Claims (1)

In the internal spline gear provided with multiple missing teeth in the circumferential row of regular teeth,
An internal spline gear that uniformly distributes the forged meat flow by molding by forging so that the cross section between the missing tooth and the regular tooth adjacent to the regular tooth is an equal thickness shape,
An internal spline gear characterized in that a protrusion is provided at the center of the inner periphery of the missing tooth.

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