JP5657502B2 - Transmission gear provided with a convex portion having a stopper function near the dog clutch teeth - Google Patents

Description

The present invention relates to a gear for a manual automobile transmission, and more particularly to a transmission gear in which a convex portion having a stopper function is formed in the vicinity of a dog clutch tooth during a shift operation. Specifically, in a gear for a transmission used in a manual transmission, a convex portion slightly projecting from the tooth bottom surface is formed over the entire circumference in the tooth row of the dog clutch tooth, so that these convex portions can be formed during a shift operation. The present invention relates to a transmission gear in which a mating sleeve tooth is brought into contact with a portion to provide a stopper function.

In the dog clutch teeth of a transmission gear used for a manual transmission, it is necessary to stop the counterpart sleeve teeth somewhere during the shift operation, and the following three methods are adopted as the stoppers. The first is a method in which a mating sleeve tooth is brought into contact with a tooth end face of a speed tooth such as a helical tooth of a transmission gear. The second is a method in which the sleeve teeth are brought into contact with the end surfaces of the dog clutch teeth of the transmission gear. The third is a method of providing a stopper function on the lever for shifting the sleeve teeth. First, a method of bringing the mating sleeve tooth into contact with the end face of the first speed tooth will be described with reference to FIG. The left side of the figure is a transmission gear W, and the right side of the figure is a mating sleeve tooth S and a lever R that shifts it in the direction of arrow A. On the outer periphery of the transmission gear W on the left side, a tooth row of helical teeth 1 of speed teeth is provided, and a tooth root surface 4 of the dog clutch tooth 2 is formed in a donut shape at the upper end. Then, on the inner diameter side, a tooth row of the dog clutch tooth 2 that meshes with the mating sleeve tooth S rises from the surface of the tooth base surface 4. On the other hand, the left end of the right sleeve tooth S has an end face S1, and when the sleeve tooth S is shifted in the direction of arrow A by the lever R, the end face S1 of the mating sleeve tooth S is the left transmission gear W. It stops in contact with the tooth root surface 4.

Of these three methods, a method of bringing the sleeve teeth S into contact with the end surfaces of the second dog clutch teeth is often employed, and will be described with reference to FIG. Similarly, the left side of the figure is the transmission gear W, and the right side of the figure is the mating sleeve tooth S. Similarly, on the outer periphery of the transmission gear W on the left side, a tooth row of helical teeth 1 of speed teeth is provided, and on the inner diameter side, a tooth row of dog clutch teeth 2 that fits with a mating sleeve tooth S is provided. It is done. And the flange 8 is formed in a donut shape inside the upper end surface of the tooth row of the dog clutch tooth 2. On the other hand, the left end of the right sleeve tooth S has an end surface S2, and when the sleeve tooth S is shifted in the direction of arrow A by the lever R, the end surface S2 of the sleeve tooth S is the flange 8 of the left transmission gear W. Stops in contact with. At this time, while the sleeve teeth S move unconstrained without the center, only a slight width of the end surface S2 of the sleeve teeth S abuts against the surface of the flange 8, so that the sleeve teeth S swing and become caught on the surface of the flange 8. It may happen that the sag becomes too shallow. Therefore, in order to prevent such disengagement, the variation in the diameter dimension of the bottom surface of the dog clutch tooth 2 must be suppressed, and here, the diameter dimension of the bottom surface is defined as a small dog diameter d. In other words, in relation to the catch with the sleeve tooth S, the dimensional tolerance of the small dog diameter d that constitutes the bottom surface 9 of the dog clutch tooth 2 needs to be 0.15 to 0.20 mm. Since the mating sleeve tooth moves unconstrained without a center, it protrudes when the dimensional tolerance of the small dog diameter d is rough, and thus interferes with the sleeve tooth. For this reason, the mating sleeve teeth do not fit with the dog clutch teeth. When the other sleeve tooth is brought into contact with the end face of the speed tooth S of the first method, the dimensional tolerance of the small dog diameter d can be loosened from about 1.0 to about 0.8 mm. In the gear W for transmission, a tooth row of the helical tooth 1 on the outer peripheral side and a tooth row of the dog clutch tooth 2 on the inner diameter side are formed by hot forging, and at the same time a tooth bottom surface 9 of the dog clutch tooth 2 is formed. Only by this hot forging process, it is very difficult to make the dimensional tolerance of the small dog diameter d of the bottom surface of the dog clutch tooth 2 from 0.15 to 0.20 mm. Therefore, the dimensional tolerance of the small dog diameter d is reduced from 0.15 to 0.20 mm by performing a cold coining molding in the subsequent process. At that time, the smaller the tolerance of the dog small diameter d is, the more the coining molding load needs to be increased, and the cold die die is damaged.

By the way, dog clutch teeth are generally cut by machining. However, since gear cutting by machining is time consuming and increases manufacturing costs, it has been proposed to reduce costs by forming the speed teeth together with forging and omitting the dog clutch tooth surface finishing. ing. This proposal has a structure in which dog clutch teeth provided on one side of a transmission gear are integrally formed by cold forging. That is, since the dog clutch teeth are integrally formed by cold forging, it is not necessary to finish the tooth surface, and there is an advantage that the cost can be reduced. In addition, since the overall rigidity of the dog clutch teeth can be balanced, the durability can be improved and the transmission function of the transmission can be stabilized over a long period of time (see Patent Document 1).

On the other hand, regarding transmission gears, the present applicants have made the following proposals regarding a non-sinking helical monoblock, and this proposal is a gear in which the inner dog clutch teeth do not sink from the upper end surface of the outer helical teeth. There is a gear product obtained by integrally forging a dog clutch tooth and a helical tooth side by side (see, for example, Patent Document 2). On the other hand, the following proposals regarding sinking monoblocks by forging are made. In other words, the chamfer of the inner dog clutch tooth is a gear block (hereinafter referred to as a sinking helical monoblock) that sank from the tooth end surface of the outer helical tooth in the axial direction (see, for example, Patent Document 3).

Japanese Patent Application Laid-Open No. 08-31675 JP 05-187521 A JP 2002-2227969 A

As described above, as represented by patent documents, the conventional dog clutch teeth have the following problems.

The manual transmission needs to have a function of stopping the mating sleeve teeth during the shift operation. For this reason, many methods are employed in which the sleeve teeth are brought into contact with the end surfaces of the dog clutch teeth of the transmission gear. In this case, there is a case where the mating sleeve teeth swing and the hooks become shallow from the flange surfaces of the dog clutch teeth. In order to prevent this, it is necessary to increase the accuracy by narrowing the tolerance of the dog small diameter on the bottom surface of the dog clutch tooth. For this purpose, since the coining molding load is increased, the service life of the cold die die is reduced because the cold coining die die is damaged. In addition, when the dog clutch teeth are subjected to reverse taper processing, the clearance with the spline punch is reduced and the life of the spline punch is unavoidably reduced because the dog small diameter is sufficiently stretched. Therefore, it has been difficult to mass-produce dog clutch teeth by forging.

Accordingly, the present invention has been made paying attention to the above-mentioned problems, and while making the tolerance of the small diameter of the dog constituting the tooth bottom surface of the dog clutch tooth rough, the other sleeve tooth is stopped during the shift operation. It has a function. For this purpose, there is provided a manual transmission transmission gear in which a convex portion slightly protruding from the bottom surface of the dog clutch tooth is provided so that a sleeve tooth on the other side is brought into contact with the convex portion during a shift operation. For the purpose.

The mainstream of transmission gears is machining of tooth surfaces by machining. Therefore, in order to facilitate machining, it is usual to simplify the shape around the dog clutch teeth. However, in recent years, it has become possible to form various shapes by forging as the forging technology advances. Therefore, the inventor of the present application pays attention to intentionally disposing a convex part slightly protruding from the bottom of the tooth in the dog clutch tooth row, and as a result of trial manufacture, the knowledge that a smooth shift operation can be performed in the manual transmission. Got. Gear for a transmission of the present application invention has embodied based on such findings, the invention of claim 1, cone toward the inner side to the outer peripheral side, the flange, the dog clutch teeth, tooth surfaces of the dentition And a helical dentition in this order are integrally formed concentrically by hot forging and cold forging, respectively, the flange is provided in contact with the outer peripheral surface of the cone, and the cone is axially provided on the inner periphery. The shaft hole penetrates and protrudes upward in the axial direction from the upper surface of the flange, and the tooth bottom surface of the dog clutch tooth row is provided in parallel with the axial direction downward from the peripheral end of the upper surface of the flange. The root surface is in contact with the root surface and is provided at a right angle in the axial direction, and is provided lower than the top surface of the flange , and protrudes from the bottom surface toward the outer periphery near the top surface of the flange at the bottom surface. Established A gear for a transmission characterized that you have the convex portion is provided to fulfill Sutopa function is abutted against the end face of the sleeve teeth. According to a second aspect of the present invention, in addition to the feature of the first aspect, the gear for a transmission is characterized in that the convex portions are provided between the dog clutch teeth in the dog clutch tooth row. According to a third aspect of the present invention, in addition to the feature according to the first aspect, the tip of the chamfer of the dog clutch tooth row is lower in the axial direction than the tooth end surface of the helical tooth row. is there.

Even if the tolerance of the small dog diameter constituting the tooth bottom surface of the dog clutch tooth in the transmission gear is rough, it is possible to provide a function of stopping the mating sleeve tooth during the shift operation. And since the tolerance of the small diameter of the dog can be made rough, it is not necessary to increase the load at the time of coining molding, and the die die is not crushed and the life of the die is extended. As a result, a gear for a transmission in which dog clutch teeth are integrally formed by forging can be mass-produced.

It is a perspective view of the gear for transmission of a present Example. It is a manufacturing process figure same as the above. It is sectional drawing of the convex part formed in the flange part in the hot forging process same as the above. FIG. 4 is a cross-sectional view of a convex portion coiningly formed on a tooth bottom surface in the cold forging step. It is an arrangement plan of the convex part formed in the dog clutch tooth row same as the above. It is sectional drawing explaining the stopper function of a convex part same as the above. It is sectional drawing explaining the stopper function in a prior art example. It is sectional drawing explaining another stopper function 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 perspective view of a transmission gear according to the present embodiment. FIG. 2 is a manufacturing process diagram. FIG. 3 is a sectional view of a convex portion formed on the flange portion in the hot forging step. FIG. 4 is a cross-sectional view of a convex portion coiningly formed on the tooth bottom surface in the cold forging process. FIG. 5 is an arrangement view of convex portions formed on the dog clutch tooth row. FIG. 6 is a cross-sectional view for explaining the stopper function of the convex portion.

The present applicant has already developed a sinking helical monoblock in which the inner dog clutch teeth are sunk from the end surfaces of the outer helical teeth in the axial direction. The transmission gear according to the present embodiment will be described with reference to FIG. 1 by taking the sinking helical monoblock as an example. In this figure, a perspective view of a single cone type transmission gear W is shown, and a tooth row of helical teeth 1 in which tooth teeth are twisted in the axial direction is formed on the outer periphery, and a shaft is formed on the inner periphery. A tooth row of dog clutch teeth 2 having a reverse taper is formed in the direction. Between these tooth rows, a root surface 4 sank from the outer helical tooth 1 is formed concentrically, and a root 24 of the dog clutch tooth 2 is formed on this surface. A frustoconical cone 5 protrudes coaxially on the inner peripheral side of the dog clutch tooth 2, and the shaft hole 3 penetrates the inner periphery in the axial direction. The frustoconical peripheral surface of the cone 5 is finished as a friction surface by performing cold forging after turning, heat treatment, and then grinding. As described above, the dentition of the outer helical teeth 1, the root surface 4, the dentition of the inner dog clutch teeth 2, and the inner peripheral cone 5 are integrated on the same axis by hot forging and cold forging. While being molded, the cone 5 protrudes above the chamfer 23 of the dog clutch tooth 2, and the root surface 4 sinks from the tooth end surface 14 of the helical tooth 1 between the helical tooth 1 and the dog clutch tooth 2. It is provided in a concentric circle shape. Here, the outer peripheral surface of the cone 5 may be a cylindrical surface in addition to the conical surface. These tooth bottom surfaces 9 of the dog clutch tooth row are formed on the outer peripheral surface where the donut-shaped flange 8 descends at a right angle, and the tooth row of the dog clutch tooth 2 is formed on this tooth bottom surface 9. In dog clutch tooth 2, the name of each part of a gear is defined as follows. The dog clutch tooth 2 is formed on the tooth tip surface 21 in the tooth trace direction, the tooth surfaces 22 and 22 on the left and right sides thereof, the chamfer 23 having a sharp tip, the root 24 of the dog clutch tooth 2 rising from the tooth base surface 4, and the tooth base 9 It is comprised from the root base 25 formed. On the other hand, the outer peripheral helical tooth 1 includes a tooth tip surface 11 in the direction of the tooth trace, tooth surfaces 12 and 12 on the left and right sides thereof, a tooth bottom surface 13 that raises these teeth, and tooth end surfaces 14 and 14 and upper and lower tooth end surfaces 14 and 14 and the tooth root 16. Composed. The configuration of the transmission gear W is summarized below. A cone 5 protrudes in a cylindrical shape in the axial direction from the inner peripheral side, and a flange 8 is formed concentrically at the base of the outer periphery. The outer periphery of the flange 8 descends perpendicularly in the axial direction and forms a concentric and cylindrical surface as a tooth bottom surface 9. Is done. Near the top surface of the flange 8 of the bottom surface 9, a convex portion 91 is formed to protrude slightly from the bottom surface 9 toward the outer periphery between the tooth rows of each dog clutch tooth 2. A concentric tooth root surface 4 is formed by sinking at a root of the bottom surface 9 of the cylindrical surface at a right angle to the tooth bottom surface 9, and a tooth root 24 of the dog clutch tooth 2 is formed on the surface of the tooth root surface 4. Then, the tip of the chamfer 23 the tip of the dog clutch teeth 2 is pointed, lower than the tooth end surface 14 of the outer periphery of the side helical tooth 1 in the axial direction. The feature of the present embodiment is that a convex portion 91 is formed to protrude slightly to the outer periphery between the tooth rows of each dog clutch tooth 2 near the top surface of the flange 8 of the bottom surface 9 which is a cylindrical surface.

The manufacturing process of the transmission gear of the present embodiment will be described based on the process diagram of FIG. 2 by taking a sinking helical monoblock as an example. 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 material W1 is heated to 1150 ° C., for example, and subjected to hot forging to obtain a disk-shaped material W2 having a protruding portion W21 protruding downward. Next, as shown in step (3), hot forging is applied to the portion of the large diameter portion D1 in the upper stage of the material W2 to roughly form the rough helical tooth 10 twisted in the axial direction, and at the same time, the lower diameter portion of the lower stage. A cone 50 is formed at the portion D2, and a rough tooth base surface 40 is formed concentrically between the outer rough helical tooth 10 and the inner peripheral cone 50. In addition, an inner diameter portion W31 having a circular cross section is formed on the inner periphery of the cone 50, and a raw material W3 having a disc-shaped protruding burr-shaped burr W32 is obtained on the outer periphery of the upper surface by the formation of the outer helical helical teeth 10. . At this time, a flat flange 80 is formed in a donut shape at the bottom of the cone 50. Here, the external teeth may be spur teeth in addition to helical teeth, and the same applies to the following description. Next, as shown in step (4), the tooth base surface 4 that is recessed on the outer periphery of the cone 50 is similarly finished by hot forging, and at the same time, the rough dog clutch teeth 20 with the roots standing on the bottom surface are straight. A material W4 formed in a shape is obtained. At this time, on the surface of the flange 80, convex portions 81 are formed so as to protrude between the respective rough dog clutch teeth of the dentition of the rough dog clutch teeth 20, and details thereof will be described later with reference to FIG. It is a feature of this embodiment that the convex portions 81 are formed over the entire circumference of the dentition of the rough dog clutch teeth 20. At the same time, the root surface 90 of the dentition of the dog clutch rough tooth 20 is formed. Next, as shown in step (5), the burr W32 on the upper surface of the material W4 is turned and removed, and the medium burr is punched out to obtain the material W5 through which the rough shaft hole 30 passes. Next, in step (6), the material W5 is subjected to normalizing heat treatment, shot blasting treatment, and bonderite treatment for applying a lubricant to obtain the material W6. Next, in the step (7), the rough helical teeth 10 on the outer periphery are formed by cold ironing so that the inclination of the tooth surface is straight. On the other hand, the rough dog-clutch teeth 20 on the inner periphery are subjected to coining or sizing treatment to obtain a material W7 having a tooth surface formed straight and a chamfer formed on the tooth tip. At this time, a flat flange 80 is formed in a donut shape at the bottom of the cone 50. In the next step (8), the outer rough helical teeth are subjected to crowning by cold ironing, and the chamfering is applied to the ridge line portion of the tooth end surface to complete the helical tooth 1. Finally, in the step (9), the rough dog clutch teeth formed straight in the step (7) are cold coined so as to become narrower from the chamfer toward the root of the teeth, and the dog clutch teeth having a reverse taper shape are formed. 2 is completed. At this time, the tooth bottom surface 9 of the dentition of the dog clutch tooth 2 is finished. At the same time, on the tooth bottom surface 9 of the dentition of the dog clutch tooth 2, a convex portion 91 is formed so as to protrude between the dog clutch teeth, and this will be described in detail later with reference to FIG. It is a feature of the present embodiment that the convex portion 91 is formed over the entire circumference of the dentition of the dog clutch tooth 2. In summary, the steps (2), (3), (4) and (5) are hot forging, and the steps (7), (8) and (9) are cold ironing or cold coining. Cold forging by forming.

Here, the details of the step (4) will be supplemented with reference to FIG. In this step, the rough dog clutch teeth 20 are formed in a straight shape in the axial direction by hot forging. At the same time, a convex portion 81 that slightly protrudes in the axial direction from the surface of the flange 80 so as to be positioned between the teeth of the rough dog clutch teeth 20 near the rough dog clutch teeth 20 of the flange 80 has an entire circumference. Formed. This convex part 81 becomes a coining allowance in the subsequent cold forging process.

Next, the details of the step (9) will be supplemented with reference to FIG. In this step, cold ironing is performed to complete the dog clutch tooth 2 having an inversely tapered shape in the axial direction. In this step (9), cold coining forging is applied to the convex portion 81 formed in the step (4) and slightly protruding from the surface of the flange 80 in the axial direction. At this time, the convex portion 81 can be pushed and moved to the tooth bottom surface 9 only by applying a small load. As a result, a convex portion 91 is formed near the upper surface of the flange 8 of the bottom surface 9 between the teeth of the dog clutch tooth 2 with a slight protrusion from the surface of the bottom surface 9 toward the outer periphery. The Here, since the convex portion 91 is disposed below the minimum meshing involute diameter (TIF diameter) determined by the relationship with the mating sleeve tooth S, the dog clutch tooth 2 does not interfere with the sleeve tooth S. Will fit together.

Through the above steps, the convex portion 91 is formed so as to slightly protrude from the surface of the tooth bottom surface 9 toward the outer periphery. This state will be described with reference to the plan view shown in FIG. In FIG. 5A, the convex portion 91 is formed over the entire circumference between the tooth rows on the bottom surface 9 of the dog clutch tooth 2, and details of the helical teeth on the outer periphery are omitted. This symbol B portion is enlarged and shown in FIG. A tooth row of the dog clutch teeth 2 is formed on the surface of the tooth bottom surface 9, and a convex portion 91 is formed between the adjacent dog clutch teeth 2 over the entire circumference. The protruding end face S2 of the mating sleeve tooth S may be formed over the entire circumference or may be formed at intervals of 120 degrees. Therefore, the convex portion 91 is formed over the entire circumference of the tooth row on the dog clutch tooth 2 side so that either can be used.

The dog clutch teeth in the transmission gear of the present embodiment are configured as described above, and the operation of the convex portions formed on the teeth of the dog clutch teeth will be described below.

The dog clutch teeth of the transmission gear used in the manual transmission must have a function of stopping the mating sleeve teeth during the shift operation, and the operation of the convex portion 91 of the present embodiment with reference to FIG. explain. The left side of FIG. 4A is a transmission gear W, and the right side is a mating sleeve tooth S. On the outer periphery of the transmission gear W on the left side, a tooth row of helical teeth 1 of speed teeth is provided, and on the inner diameter side, a row of dog clutch teeth 2 that meshes with a mating sleeve tooth is provided. The upper surface of the tooth row of the dog clutch teeth 2 is formed on the inner diameter side, and the surface of the flange 8 is formed in a donut shape. FIG. 2B is a sectional view showing a portion of the convex portion 91 formed between the dog clutch teeth 2. The left end of the right sleeve tooth S has an end surface S2, and when the sleeve tooth S shifts in the direction of arrow A, the end surface S2 of the sleeve tooth S abuts against the convex portion 91 of the left dog clutch tooth 2 and stops. . At this time, since the convex portion 91 protrudes from the bottom surface 9 of the dog clutch tooth 2 while the sleeve tooth S moves without being restrained without the center, the end surface S2 of the sleeve tooth S always comes into contact with the convex portion 91. . Thus, the convex part 91 formed between the dog clutch teeth 2 has a function of stopping the mating sleeve teeth during the shift operation. If the convex portion 91 is not provided, the function of stopping the sleeve tooth S is that a slight width of the end surface S2 of the sleeve tooth S hits the surface of the flange 8, so that the sleeve tooth S that moves without the center swings and the flange 8 The hook becomes shallow and comes off. Therefore, in order to prevent this, it is necessary to increase the accuracy of the dimensional tolerance of the small dog diameter d constituting the tooth bottom surface of the dog clutch tooth 2 from 0.15 to 0.20 mm because of the hooking with the sleeve tooth S. The life is shortened because the cold coining die is loaded. In the present embodiment, since the convex portion 91 slightly protruding from the bottom surface 9 of the dog clutch tooth 2 is provided, it is not necessary to increase the accuracy of the dimensional tolerance of the small dog diameter d. The convex portion 81 formed by hot forging is pushed and moved by performing cold coining to form the convex portion 91. At that time, since the coining molding load can be reduced, the cold die is not loaded. In addition, since a sufficient clearance can be secured in a portion related to the reverse taper forming of the dog clutch tooth 2 while providing a stopper function for the sleeve tooth S on the other side, the influence of the life of the spline punch is small. In this way, the dog clutch teeth were formed in a mass production manner by forging.

Further, in this embodiment, the sinking helical monoblock gear is formed by forging so that the dog clutch tooth chamfer sinks below the end surface of the outer helical tooth, so that the total length of the transmission gear in the axial direction can be shortened. As a result, the transmission gearbox can be made compact. That is, if the root of the dog clutch tooth is formed on the sinked tooth root surface, the effective length of the transmission gear can be obtained, and the total length of the transmission gear can be reduced by about 15 mm to 20 mm.

A Arrow B Symbol d Dog Small Diameter R Lever S Sleeve Teeth, S1 End, S2 End W Transmission Gears W1, W2, W3, W4, W5, W6, W7, W8 Material W21 Convex, W31 Inner Diameter, W32 End burr, W33 Medium burr 1 Helical tooth, 10 Rough helical tooth 11 Tooth surface, 12 Tooth surface, 13 Tooth bottom surface, 14 Tooth end surface, 16 Tooth base 2 Dog clutch tooth, 20 Rough dog clutch tooth 21 Tooth surface 22 Tooth Surface 23 Chamfer, 24 Tooth root, 25 Tooth root 3 Axle hole, 30 Rough shaft hole 4 Tooth surface, 40 Rough tooth root surface 5 Cone, 50 Rough cone 8 Flange, 81 Convex part 9 Tooth base, 91 Convex part

Claims (3)

Cone toward the inner side to the outer peripheral side, the flange, the dog clutch teeth, tooth surfaces and the helical teeth of the dentition is integrally formed concentrically with each hot forging and cold forging in this order,
The flange is provided in contact with the outer peripheral surface of the cone,
The cone has an axial hole extending through the inner periphery, and protrudes upward in the axial direction from the upper surface of the flange.
The bottom surface of the dog clutch tooth row is provided in parallel with the axial direction downward from the peripheral end of the top surface of the flange,
The root surface is in contact with the tooth bottom surface, provided at a right angle in the axial direction, and lower than the top surface of the flange,
The upper surface side of the said flange in the tooth bottom, from said root surface protrudes in the outer peripheral direction, the transmission characterized that you have the convex portion is provided to fulfill Sutopa function is abutted against the end face of the sleeve teeth Gears. The transmission gear according to claim 1, wherein the convex portions are provided at all positions between the dog clutch teeth in the dog clutch tooth row. The transmission gear according to claim 1, wherein a front end of the chamfer of the dog clutch tooth row is lower in an axial direction than a tooth end surface of the helical tooth row.

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