JP2014098438A - Double helical gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double helical gear in which a pair of helical teeth having right and left twisting directions opposite to each other are integrally formed by a cold forging from an annular coarse material, a mold structure is properly modified to eliminate a phase shift in a tooth facing direction and improve a dedendum strength with high accuracy.SOLUTION: This invention relates to a double helical gear in which a pair of helical teeth having opposite right and left twisting directions are formed on the same axis of an outer peripheral surface of a cylindrical coarse material and an interface area is arranged between the pair of helical teeth, the interface area is constituted by a groove or a rib.

Description

  A YAMABA gear is a gear that combines a pair of helical teeth whose torsional directions are opposite to each other on the same axis, and transmits power between parallel axes, which is relatively used mainly in gear devices of various industrial machines. It is a large gear. Yamaba gear is also called a helibone gear or double helical gear. When a normal helical gear is used for an industrial machine or the like, a stopper is provided to stop the thrust force, so that a large space of the machine is required. On the other hand, if the YAMABA gear is used, the thrust force is canceled out, so that a stopper is not required and the industrial machine or the like can be a small space. Mainly, YAMABA gears are used in parallel cardan gears for railway vehicle drive systems, gear pump type extruders that are plasticized and extruded while mixing elastomers such as gear pump type rubber, synthetic rubber or natural rubber, and planetary gears for planetary gears. Applied. A YAMABA gear is a gear in which a pair of helical gears whose left and right twist directions are opposite to each other are combined on the same peripheral surface side by side to cancel the axial thrust force. No thrust load is generated, so in principle it is an ideal gear that can achieve quietness, but in reality it is difficult to cut a pair of helical teeth with opposite left and right twist directions by machining . Therefore, the Yamaba gear of the present invention relates to an integrated gear in which a pair of helical teeth whose left and right twist directions are opposite to each other are combined on the same axis, and a pair of helical teeth whose left and right twist directions are opposite is formed by forging. If anything, it is a small gear.

Conventional Yamaba gears are manufactured by an integral method or an assembly method. FIG. 9 shows an example of use of the integrated yamaba gear. Here, the Yamaba gears W10 and W10 mesh between the upper and lower parallel axes S1 and S2. In the integral system, a clearance groove for a tool blade is provided in the center portion for gear cutting by gear shaper processing. The YAMABA gear W10 in the upper part of the figure is composed of a pair of helical teeth 1 and 2 whose left and right twist directions are opposite to each other and a groove 4 therebetween. In other words, the Yamaba gear W10 is formed by mechanically cutting a pair of helical teeth 1 and 2 having a twisted direction opposite to the left and right in the axial direction of the integral cylindrical coarse material, and preventing the gear shaper blade from escaping or interfering therebetween. The groove 4 is provided.
On the other hand, the assembly method is a method in which helical teeth with opposite twist directions are separately formed on each cylindrical material by hobbing, and a pair of helical teeth with opposite twist directions on the same axis are combined. is there. That is, a pair of helical teeth whose directions of twisting are opposite to each other are individually formed in each cylindrical material, and these are combined on the same axis by shrink fitting or the like.

The following proposals have been made for Yamaba gears. The YAMABA gear is not used for automobile transmissions and its applications are not many. For example, it is used for a transmission path from a prime mover of a railway vehicle. An example of an assembly-type large YAMABA gear used in a hanging railway vehicle drive device is shown below. A single gear boss is fitted to the inner diameter of a pair of helical gears with different twisting directions to the left and right to allow a small diameter difference to be slidable to form a yamaba gear. This is a structure in which a disc-shaped plate spring is attached, and the outer diameter side of this plate spring is screwed to a toothed wheel and the inner diameter side is screwed to a gear boss with a bolt (see Patent Document 1).
Similarly, an application example of the YAMABA gear is shown, and there is an example in which the YAMABA gears of the YAMABA gear inserted from the outside of the housing are easily meshed with each other. Specifically, a first YAMABA gear on the drive side that is disposed outside the housing and attached to the drive shaft, a second YAMABA gear on the driven side that is disposed inside the housing, and a side wall of the housing A built-in hole for holding the drive shaft of the first yamaba gear formed, and a bearing member that is fitted in the built-in hole without any gap and holds the drive shaft of the first yamaba gear; In the assembly structure of a YAMABA gear in which the first YAMABA gear inserted from the outside of the housing is engaged with the second YAMABA gear inside the housing, and the gears are coupled, the second YAMABA gear inside the housing is rotated in the direction of its rotation axis. The first yamaba gear is moved upward and inserted into the mounting hole, the first yamaba gear is moved downward and meshed with the second yamaba gear, and the first and second They are moved inwardly of the housing in a double-helical state in which gears are engaged, in which as assembled fitted the bearing member embedded within the bore of the housing side wall (see Patent Document 2).
In addition, the present applicant (hereinafter referred to as the applicant) has made the following proposals regarding the integrated Yamaba gear. That is, the YAMABA gear can be integrally formed by forging means, and recessed portions of the same diameter are provided facing the opposing surfaces of the die and the punch, and the inclined directions are opposite to each other on the inner peripheral surface of the recessed portions. In this molding method, a material is placed in a forging die composed of a die having a helical tooth profile forming die and a punch, and a tooth profile is formed by projecting from the periphery of the material into each helical tooth profile forming die. In addition, a concave portion having the same diameter is provided facing the opposing surfaces of the die and the punch, respectively, and a helical tooth profile forming tooth mold having opposite inclination directions is formed on the inner peripheral surface of both concave portions, and at least the die The forming device configured to rotatably support each helical tooth profile forming tooth portion of the punch, and the material is restrained by the forging die, and the punch is moved from the upper die and the lower die to the center of the material corresponding to the shaft hole. This is a method in which a tooth profile is formed by being pushed into each helical tooth profile forming tooth mold around the material (see Patent Document 3).

Japanese Utility Model Publication No. 61-10039 JP 2007-132436 A JP-A-5-277618

  As described above, as represented by patent documents, the conventional YAMABA gear has the following problems.

  The assembly-type YAMABA gear is formed with a pair of helical teeth whose left and right twist directions are opposite to each other, and then combined, so that the tooth phase shifts and tooth thickness variations occur, resulting in high accuracy gears. Absent. In addition, when a pair of helical teeth whose left and right twist directions are opposite to each other are combined to manufacture an integral type YAMABA gear, the number of processes increases and the cost increases significantly. On the other hand, it is difficult to obtain a highly accurate assembly method of Patent Document 1 as well. In addition, according to the method of integrally forming a yamaba gear by forging means in Patent Document 3, a lot of ingenuity is required in the mold to obtain a yamaba gear in which the tooth trace phases of a pair of helical teeth twisted in the left-right direction coincide And practical application is difficult.

  Accordingly, the present invention has been made paying attention to the above problems, and is based on integrally forming a pair of helical teeth having opposite twist directions by cold forging. In the present invention, a pair of helical teeth with opposite left and right twist directions are integrally formed by cold forging from an annular rough material, and the die structure is devised to increase the phase without causing a phase shift in the tooth trace direction. An object of the present invention is to provide a YAMABA gear with high accuracy and improved tooth root strength.

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 the fact that a tooth profile with a good tooth profile can be obtained by cold forging, and there is no phase shift in the tooth trace direction of the helical tooth by devising a mold, and The present inventors have found that the strength of the gear is excellent by utilizing the fiber flow (hereinafter referred to as fiber flow) formed by cold forging as it is. The YAMABA gear of the invention of the present application is embodied based on such knowledge, and the invention of claim 1 is characterized in that a pair of helical teeth whose directions of twisting are reversed to the left and right are arranged on the same axis on the outer peripheral surface of the cylindrical coarse material. A yamaba gear formed and provided with a boundary region between the pair of helical teeth, wherein the boundary region is constituted by a groove or a rib.
The invention according to claim 2 is the YAMABA gear which is characterized in that, in addition to the feature of claim 1, the rib is connected over the entire circumference of the end face on the boundary region side of the pair of helical teeth.
According to a third aspect of the present invention, in addition to the feature of the first aspect, the width of the groove is less than 3 mm.
The invention according to claim 4 is the yamaba gear characterized in that, in addition to the feature of claim 1, the helical teeth have a crowning or end relief tooth profile along the tooth trace.
In the present invention, the tooth profile in the tooth trace direction is referred to as a helical tooth regardless of whether or not the tooth profile is bulged. In particular, when a bulge is provided in the tooth profile in the tooth trace direction, it is referred to as a crowned or end-relieved helical tooth.

  According to the present invention, a pair of helical teeth whose twist directions are opposite to each other by cold forging are integrally formed on the same axis, so that an integrated Yamaba gear in which the phases of the left and right tooth traces coincide can be obtained. It was. The Yamaba gear of the present invention has two forms, and is a method of providing a rib between a pair of helical teeth whose left and right twist directions are opposite, or a method of providing a groove between a pair of left and right helical teeth. In the conventional integrated type YAMABA gear, a tool blade escape groove is provided between a pair of helical teeth whose left and right twist directions are opposite to each other for gear cutting with a gear shaper blade. This groove required a groove width dimension of 4 mm or more due to a stroke due to gear shaper processing. In the method of providing the groove of the present invention, the groove width dimension can be reduced to less than 3 mm or about 2 mm. As a result, the overall axial length of the YAMABA gear can be shortened, so that it is possible to reduce the weight and size. On the other hand, since ribs are formed over the entire circumference of the dentition, the strength is reinforced by the ribs, and the bending fatigue resistance is improved at the divided portions of the upper and lower helical teeth. In addition, since the helical tooth of the present invention has a tooth profile formed by forging, the fiber flow along the tooth profile is densely formed inside the tooth profile, and as a result, the surface pressure fatigue strength of the helical tooth is improved and the tooth root is also formed. The bending fatigue strength at is improved.

It is a figure of the annular | circular shaped rough material which shape | molds the Yamaba gear of Example 1 by cold forging. It is a figure which shows the state which the metal mold | die before starting shaping | molding of an annular | circular crude material same as the above. It is a figure which shows the state which an upper and lower metal mold | die closes and starts shaping | molding same as the above. It is a figure which shows the state which shaping | molding and gear cutting completed as above. It is a figure which shows the implementation form which gear cutting was completed from the annular | circular shaped rough material by cold forging same as the above. It is sectional drawing of the YAMABA gear which has a rib same as the above. It is a figure which shows the state of the fiber flow produced in the case of cold forging same as the above. It is sectional drawing of the yamaba gear which has a groove | channel of Example 2. FIG. It is a figure which shows the yamaba gear by a prior art example.

  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 diagram of an annular coarse material formed by cold forging the Yamaba gear of the first embodiment. FIG. 2 is a view showing a state in which the mold before the annular coarse material is molded is opened. FIG. 3 is a diagram showing a state in which the upper and lower molds are closed and molding is started. FIG. 4 is a diagram illustrating a state in which molding and gear cutting have been completed. FIG. 5 is a diagram showing an embodiment in which gear cutting is completed by cold forging from an annular coarse material. FIG. 6 is a cross-sectional view of a yamaba gear having ribs. FIG. 7 is a diagram showing a state of fiber flow that occurs during cold forging.

  The main steps of the manufacturing process of the YAMABA gear of this embodiment will be described. First, a cylindrical material suitable for a Yamaba gear is cut into a predetermined axial length, for example, a rough material cut by a billet shear is obtained. In this case, a steel material suitable for the Yamaba gear, such as SC steel, SCR steel, SCM steel, SNC steel, SNCM steel, etc., can be used as the material of the rough material. Next, the cut coarse material is heated to 1200 ° C., for example, and subjected to hot forging to form an annular shape with a hole passing through the center, and then an annular coarse material W1 that is machined on the inner and outer periphery is obtained. This is shown in FIG. Alternatively, an annular coarse material W1 in which a hole penetrates the center is obtained by a method of punching a hole in the cut coarse material by cold forging. Next, in order to form a pair of helical teeth whose directions of twisting are opposite to each other on the outer periphery of the coarse material W1, the coarse material W1 is set in the mold apparatus shown in FIG. In addition, there is a use of the small gear which uses resin as a material of a coarse material.

  Here, the configuration of the mold will be described with reference to FIG. 2 for details of forming a pair of helical teeth in opposite directions by cold forging. The mold is configured separately on the upper ram side and the lower bed side. The upper ram side includes an outer upper punch P1, an inner center mandrel P2, and a die mold Q1 surrounding the upper punch P1 from the outside. The lower ram side includes an outer die mold Q2, a lower punch P3 on the inner peripheral side, a lower punch P4 on the inner central portion, and a push-up ejector P5 on the lower side. On the inner circumference of the upper ram side die mold Q1, a helical tooth tooth mold T1 is provided. On the other hand, on the inner circumference of the lower bed side die mold Q2, the tooth trace is opposite to the tooth mold T1. A twisted helical tooth type T2 was provided. The die Q1 on the upper ram side is configured to be rotatable (not shown) in order to take out the formed coarse material. The lower bed side has a fixed structure for both the die Q2 and the lower punch P3.

  In order for the Yamaba gear of the present embodiment to form a pair of helical teeth in opposite directions, it is important that the upper and lower helical teeth prevent a phase shift in the tooth trace direction. For this purpose, some mechanism for preventing phase shift is necessary, but is omitted.

  Next, a procedure for forming helical teeth by cold forging will be described with reference to FIG. The pin P2 is lowered by hydraulic pressure or the like to press down and pressurize the die Q1 until the upper ram is lowered and contacts the upper surface of the die Q2. In this way, a contact pressure is generated between the die Q1 and the die Q2, and the upper and lower sides are closed. In this state, by lowering the upper punch P1, the annular coarse material W1 placed on the lower punch P3 is pressurized and plastically deformed into the coarse material W2 (FIG. 4). During this time, the upper helical tooth 1 is formed by the tooth mold T1 provided on the inner periphery of the die mold Q1. At the same time, the lower helical teeth 2 are twisted in the opposite direction by the tooth mold T2 provided on the inner periphery of the die mold Q2. Next, with the outer dies Q1 and Q2 closed, the upper ram moves backward and the inner upper punch P1 moves backward first. When the molding is completed, the coarse material W2 is taken out by raising the ejector P5.

  The pair of helical teeth twisted in the left and right directions using the mold shown in FIG. 2 is completed, and the detailed shape of the coarse material W2 is shown in FIG. 5 as a cross-sectional view. A pair of helical teeth 1 and 2 having tooth traces twisted in the opposite directions on the outer periphery are formed vertically, and the rough shaft hole 30 penetrates through the center. A coarse rib 50 is formed at the boundary between the upper and lower helical teeth 1 and 2 so as to protrude from the tip surface of the helical tooth in the outer radial direction, and the formation of this rib is a feature of this embodiment. The present rough material W2 is characterized in that a surplus wall is formed in addition to the rough ribs 50 while a meat flow caused by pressurization flows with a low load. That is, on the outer peripheral side of the rough shaft hole 30, the surpluses 60 and 60 are filled in the vertical direction and formed. Further, the back surfaces of the upper and lower helical teeth 1 and 2 are filled in the vertical direction to form the surplus thickness 70 and 70. Later, these surplus parts are scraped off.

  Next, the rough material W2 shown in FIG. 5 is machined to obtain a yamaba gear W100, which is shown in FIG. That is, the shaft hole 3 penetrating vertically is provided by grinding the inner diameter or chamfering the inner periphery of the upper and lower ends. Then, at the boundary between the upper and lower helical teeth 1 and 2, the rib 5 is provided by scraping the outer peripheral front end surface of the coarse rib 50 projecting radially outward from the tooth tip surface. The excess meat 60, 60, 70, 70 that protrudes outward in the vertical direction is also scraped off. In the figure (a), the yamaba gear W100 is shown with sectional drawing. In FIG. 5B, a symbol OA arrow view is shown, and the relationship between the rib and the helical tooth is understood. Although a part of the helical tooth circumferential row is shown, the rib 5 is disposed between the circumferential rows of the helical teeth 1. In this figure, the tooth tip diameter of the helical tooth 2 and the outer diameter of the rib 5 are flush with each other, but the tip of the rib 5 may be recessed from the tooth tip surfaces of the helical teeth 1 and 2, and its detailed shape Is shown as a partially enlarged view E in FIG. The tip of the rib 5 has a recess D that is recessed inward from the tooth tip surfaces of the helical teeth 1 and 2. Or the front-end | tip part of the rib 5 may protrude from the tooth tip surface of the helical teeth 1 and 2. FIG.

  The YAMABA gear according to this embodiment is configured as described above, and its operation will be described below.

  In the present embodiment, as described above, a rib is provided between a pair of helical teeth twisted in the left and right direction by cold forging. During forging, the coarse material W2 is crushed by the punch P1 from above, while the coarse material W2 is crushed by the punch P3 from below (see FIGS. 3 and 4). At this time, a forging flow is formed inside the helical tooth, and the state thereof is schematically shown in FIG. FIG. 6A shows a state in which the flow of meat flows F1 and F2 is generated from the vertical direction when the rough material W2 is crushed from the vertical direction by the vertical punch. From the mold structure, a gap is provided at the boundary between the upper and lower helical teeth 1 and 2, and the outer end of this space is not provided with a closing portion. The coarse ribs 50 are formed by filling the gaps between the upper and lower helical teeth as they flow as the meat flows F1 and F while being pressed by the upper and lower punches as the meat flows F1 and F. FIG. 6B schematically shows a fiber flow formation state in the tooth profile as a view taken along arrow B-B ′ in FIG. In the present embodiment, since the outer tip of the gap is not closed, the meat flows F1 and F2 are joined while being pressurized by the upper and lower punches, and the rough ribs 50 are formed by filling the boundaries of the upper and lower helical teeth. Further, in this embodiment, since the surplus is consciously pushed out to the outer peripheral side of the gap, the meat flow is filled and stretched to the tip portion. Normally, the fork of the meat flow is not provided in the forging, but the cold forging of the present embodiment was able to prevent the lack of thickness by filling the meat flow to the tip portion by intentionally providing the escape path. If a closed portion is provided at the outer tip of the rib gap, an air pool is formed at the tip, the meat flow does not fill, and a lack of thickness occurs. By such a procedure, the rough rib 50 could be stretched to the tip corner portion without causing a lack of thickness. Here, the formation of the fiber flow in the present embodiment will be described with reference to FIG. The fiber flow is densely and evenly formed in the surface layer portion of the tooth surface along the tooth profile center line C in the vertical direction and on the left and right sides of the tooth profile center line C, and the fiber flow is closely spaced to the inside of the tooth profile. Therefore, the internal structure of the tooth profile is equalized as a whole, the surface pressure fatigue strength of the helical tooth is improved, and the bending fatigue strength at the tooth base is improved. In addition to this, in this embodiment, a rib is formed over the entire circumference of the dentition, so that the strength is strengthened by this rib, and the bending fatigue strength is further improved in the divided portion of the upper and lower helical teeth.

  A second embodiment of the present invention will be described with reference to FIG. The same figure (a) shows the Yamaba gear W200 obtained by processing the rough material W2 shown in FIG. FIG. 4B shows the crowning tooth profile corrected in the direction of the tooth trace, and FIG. 5C shows double crowning corrected in the direction of the tooth trace. The YAMABA gear W200 shown in FIG. 8A is obtained by providing a shaft hole 3 penetrating up and down by grinding the shaft hole and both ends thereof after turning and carburizing, or by chamfering the inner periphery of the shaft hole. It is done. Then, at the boundary between the upper and lower helical teeth 1 and 2, the coarse rib 50 shown in FIG. The greater the thickness of the coarse rib 50, the easier it is to fill the meat flow during forging. Therefore, although it is easier to manufacture if the width dimension of the groove 4 is increased, it has been confirmed through trial and error that the width of the groove 4 can be reduced to less than 3 mm or 2 mm.

  The YAMABA gear according to this embodiment is configured as described above, and its operation will be described below.

  In the conventional YAMABA gear, a groove is provided at the boundary between the pair of helical teeth in order to cut the pair of helical teeth and prevent interference between the tool blades. Normal gear cutting is performed by hobbing or gear shaper, but especially in the case of a gear shaper, a margin for the stroke of the tool blade is required to prevent blade interference. Usually, the width dimension of the groove that becomes the allowance for the tool blade is required to be 4 mm or more. In this embodiment, the groove is formed by removing the boss generated during forging, but the width of the groove can be any size, and the maximum can be reduced from less than 3 mm to the minimum of 2 mm. In the case of the present embodiment, since the groove width dimension in the case of gear cutting by conventional machining is smaller than 4 mm, there is an effect that the entire length of the YAMABA gear in the axial direction can be reduced and the weight can be reduced. Next, the tooth profile corrected in the tooth trace direction can be applied to the helical teeth 1 and 2 of the second embodiment. The helical tooth subjected to crowning in FIG. 8B has a bulge amount L of about 5 μm in the center along the tooth trace direction, and both end portions of the tooth width escape and become thin. Alternatively, in the double crowning of FIG. 8C, the bulge amounts L1 and L2 are about 5 μ at two locations along the tooth trace, and both end portions of each tooth width escape and become thin. Further, in FIGS. 8B and 8C, it is also conceivable that the tooth profile in the tooth trace direction is an end relief and the helical tooth is formed by appropriately releasing both ends of the tooth width. In the case of FIG. 8C, the ratio of the length in the tooth trace direction when the both ends of the tooth width are released is, for example, the ratio of the lengths G1, G2, and G3 from the end to the center is considered as 1 to 3 to 2. It is done. By selecting the tooth profile shown in FIGS. 8B and 8C, the variation in the processing accuracy of the helical teeth or the variation in the assembling accuracy between the meshing gears can be absorbed, so that the contact between the meshing gears can be prevented. it can. As a result, vibration is reduced and noise generation is suppressed. In the same way, it is of course possible to make the tooth profile in the tooth trace direction into a helical tooth with crowning or end relief as well in the Yamaba gear provided with the ribs of Example 1.

  Since the tooth shape of the Yamaba gear of the present invention is completed by cold forging, the forged surface is not scraped off by machining such as hobbing, shaving, etc., and the internal fiber flow is maintained as it is to improve the durability of the gear. Can be improved. Since it is not necessary to perform machining for removing burrs generated by machining, machining costs can be reduced. Therefore, the YAMABA gear of the present invention is not limited to special applications such as a resin kneader, but can be applied to various machine devices such as machine tools, cargo handling construction machines, and robots.

S1, S2 Parallel axis W1 Circular coarse material W2 Helical tooth coarse material W10, W100, W200 Yamaba gear P1 Upper punch, P2 Pin P3 Lower punch, P4 Ejector, P5 Knockout pin Q1 Die type, Q2 Lower die type T1, T2 Teeth Type C Cotter pin D Recess F Fiber flow F1, F2 Meat flow
L, L1, L2 Swelling amount 1, 2 Helical tooth 3 Shaft hole, 30 Coarse shaft hole 4 Groove 5 Rib, 50 Coarse rib 60, 70 Extra portion 11 Tooth surface, 12 Tooth surface, 16 Tooth base

Claims (4)

On the outer peripheral surface of the cylindrical coarse material, a pair of helical teeth whose torsional directions are opposite to each other are formed on the same axis, and a YAMABA gear provided with a boundary region between the pair of helical teeth,
The boundary area is formed of a groove or a rib.   2. The YAMABA gear according to claim 1, wherein the rib is connected over the entire circumference of the end surface on the boundary region side of the pair of helical teeth.   2. The YAMABA gear according to claim 1, wherein the width of the groove is less than 3 mm.   The YAMABA gear according to claim 1, wherein the helical teeth are crowned or end-relieved along a tooth trace direction.

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