JP4530279B2 - Coarse gear design method - Google Patents

Description

  The present invention relates to a method for designing a coarse gear when a desired gear is formed by sizing after forming a coarse gear by forging.

  Conventionally, gears have been used as power transmission means in many applications. There are various types of gears such as a spur gear W102a as shown in FIG. 2A and a bevel gear W102b as shown in FIG. In many cases, the gear W102 has a tooth profile formed by cutting using a gear cutter or the like. However, the cutting has a problem that the processing time is long and the productivity is low. Therefore, in recent years, a rough sizing gear W101 that approximates the desired gear W102 is formed from a raw material through a plurality of forging processes, and then finish sizing is performed to form the gear W102.

  Here, when designing the gear W102, as shown in FIG. 6A, the normal tooth profile G101, which is the tooth profile of the gear W102, is set based on the involute tooth profile, and as shown in FIG. The coarse tooth profile G104 of the previous coarse gear W101 was set to a shape obtained by adding a predetermined amount of sizing allowance by sizing to the tooth surface of the regular tooth profile G101 indicated by a two-dot chain line.

  In the coarse gear design method, since the coarse tooth profile G104 adds a predetermined amount of sizing allowance almost uniformly to the regular tooth profile G101, it is considered that sizing can be performed in a well-balanced manner over the entire tooth surface. However, with respect to the vicinity of the tooth tip G104b of the rough tooth profile G104, if the sizing process is performed with the same sizing allowance as the vicinity of the center of the tooth surface, the sizing allowance is small in the vicinity of the tooth tip G104b, leading to the occurrence of a lack of thickness and the like. The accuracy of G101 may decrease.

  Therefore, it is conceivable to increase the sizing allowance in advance by adding surplus in the vicinity of the tooth tip G104b in order to suppress the lack of thickness in the vicinity of the tooth tip G104b of the rough tooth profile G104. However, when the sizing allowance increases only in the vicinity of the tooth tip G104b, a load burden is applied only to a part of the sizing mold, and the life of the sizing mold may be reduced.

  Accordingly, an object of the present invention is to provide a method for designing a coarse gear that suppresses a decrease in accuracy of a regular tooth profile and increases the life of a sizing die.

  The present invention forms a temporary tooth shape by moving a positive tooth shape, which is a tooth shape of a desired gear, to the outer diameter side of the gear by a predetermined amount, connects the root side of the temporary tooth shape to the tooth bottom of the positive tooth shape, It is characterized in that the connected intermediate tooth profile is set to a shape in which the tooth tip side of the intermediate tooth profile is cut out so as to be the same as the regular tooth profile.

  According to the coarse gear design method of the present invention, a positive tooth shape, which is a desired tooth shape of the gear, is moved by a predetermined amount to the outer diameter side of the gear to form a temporary tooth shape, and the root side of the temporary tooth shape is a positive tooth shape. In addition to connecting to the root of the tooth, the intermediate tooth profile with the root connected to the tooth root of the intermediate tooth profile is set to the same shape as the normal tooth profile, so that the tooth root side is cut from the tooth root to the tooth tip. Ideally, the sizing allowance can be set so as to increase, so that no thinning occurs near the tooth tip in the sizing process. Further, no load is applied to only a part of the sizing mold, and the life of the sizing mold can be increased.

  A method of designing a coarse gear with an ideal sizing allowance was realized.

  1 to 5 show an embodiment of a method for designing a coarse gear according to the present invention. FIG. 1 is an explanatory view showing the method for designing a coarse gear, FIG. 2 is a sectional plan view showing the coarse gear and the gear, and FIG. Is a partial sectional plan view showing a state before the sizing process is performed on the rough gear by forging, FIG. 4 is a partial sectional plan view showing a state after the sizing process is performed on the rough gear, and FIG. It is a cross-sectional top view showing a gearwheel.

  First, the gear will be described. This gear W2 is a spur gear W2a as shown in FIG. 2A, and has a plurality of tooth shapes (normal teeth) G1 extending in the axial direction on the outer peripheral side and a center hole 12 penetrating on the inner peripheral side. The regular tooth profile G1 of the gear W2 is an involute tooth profile as shown in FIG. 1A, and is formed such that the tooth thickness gradually decreases from the root G1a to the tooth tip G1b.

  When the spur gear W2a is formed by forging, a coarse gear W1 ((a) in FIG. 2) that approximates the desired gear W2 is formed from the raw material through a plurality of forging steps. Thereafter, the sizing margin provided in the tooth profile (coarse tooth profile) G4 of the coarse gear W1 is corrected by finishing sizing to form the desired spur gear W2a.

  Here, a design method of the coarse gear W1 before the sizing process will be described with reference to FIG.

  First, the operator determines the specifications of the spur gear W2a, for example, the number of teeth, the module, the pressure angle, the tooth depth, the tooth width, the reference pitch circle diameter, and the like using a microcomputer or the like and designs the spur gear W2a. At this time, the positive tooth profile G1, which is the tooth profile of the spur gear W2a, is an involute tooth profile as shown in FIG. In the first step, this regular tooth profile G1 is set to a predetermined amount P toward the outer diameter side of the spur gear W2a. In this case, P = 1/15 of the tooth depth, and is moved by the predetermined amount P to set the temporary tooth profile G2 (in FIG. B) Solid line) is formed. Subsequently, in the second step, the tooth root G2a side of the temporary tooth profile G2 is connected to the tooth root G1a of the normal tooth profile G1, and the tooth depth is "the tooth depth of the normal tooth shape G1 + predetermined amount P" (see FIG. 1). (C) solid line). Thereafter, in the third step, the tooth shape of the intermediate tooth profile G3 is set to a shape obtained by cutting the tooth tip G3b side of the intermediate tooth profile G3 so that the tooth profile of the intermediate tooth profile G3 is the same as that of the regular tooth profile G1, and the coarse tooth profile G4 of the coarse gear W1 is designed. .

  According to the design of the coarse gear W1 as described above, the sizing margin is set so as to gradually increase from the root G4a to the tooth tip G4b.

  Next, the sizing process for actually forming the spur gear W2a from the coarse gear W1 will be described.

  FIG. 3 shows a sizing device 31 before sizing processing, and includes a movable die 41 and a fixed die 51. In the fixed mold 51, a die 52 having a sizing tooth mold 53 for forming a positive tooth shape G1 on the inner periphery thereof and a die holder 54 disposed on the outer peripheral side of the die 52 are fixed together by shrink fitting, and the die 52 is fixed. A counter pin 55 that is movable in the axial direction is disposed on the inner peripheral side of the counter. The movable die 41 is provided with a punch 42 along the axis of the fixed die 51. The movable mold 41 can advance and retreat with respect to the fixed mold 51.

  When the spur gear W2a is formed by the sizing device 31, the coarse gear W1 is placed on the counter pin 55 of the fixed die 51 while the movable die 41 is waiting on the upper side, and then the movable die 41 is lowered. After the punch 42 comes into contact with the coarse gear W1, the coarse gear W1 is pushed downward integrally with the counter pin 55, and as shown in FIG. 4, sizing the coarse tooth profile G4 of the coarse gear W1 following the sizing tooth profile 53 of the die 52. Processing is applied. That is, in the coarse tooth profile G4 of the coarse gear W1, the sizing margin is small on the tooth bottom G4a side, and the sizing margin gradually increases toward the tooth tip G4b. Insufficient thickness is not generated near the tooth tip G1b. Thereafter, the movable die 41 is retracted upward, the counter pin 55 is raised, and the spur gear W2a is removed from the die 52, and the sizing process is completed.

  Therefore, according to the design method of the coarse gear W1, the sizing allowance can be set so as to gradually increase from the tooth bottom G4a toward the tooth tip G4b, so that the design becomes easy.

  In addition, when sizing is performed on the coarse gear W1 designed as described above, it is possible to suppress the occurrence of the thinning in the vicinity of the tooth tip G1b.

  Further, since the sizing allowance of the coarse gear W1 gradually increases, the load load on the sizing die also changes gradually, so that the excessive load is not increased only in a part.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the present invention. For example, although the spur gear W2a is taken up as the gear W2 in the above embodiment, the gear W2 is not limited to the spur gear W2a, and can be used with various gears W2 such as a bevel gear W2b as shown in FIG. it can.

It is explanatory drawing showing the design method of the coarse gear of the Example of this invention. It is a cross-sectional top view showing a coarse gear and a gear. It is a fragmentary sectional top view showing the state before performing a sizing process by forging to a rough gear. It is a fragmentary sectional top view showing the state after giving sizing processing to a rough gear by forge. It is a section top view showing other gears. It is explanatory drawing showing the design method of the conventional coarse gearwheel.

Explanation of symbols

G1 Positive tooth profile G1a (Regular tooth shape) Tooth base G2 Temporary tooth shape G2a (Primary tooth shape) Tooth base G3 Intermediate tooth shape G3b (Intermediate tooth shape) Tooth tip P Predetermined amount W1 Coarse gear W2 Gear

Claims (1)

  In the coarse gear design method of forming the desired gear (W2) by sizing after forming the coarse gear (W1) by forging, the gear tooth (G1), which is the tooth profile of the desired gear (W2), is changed to the gear ( W2) is moved to the outer diameter side by a predetermined amount (P) to form a temporary tooth profile (G2), and the tooth root (G2a) side of the temporary tooth profile (G2) is connected to the tooth root (G1a) of the normal tooth profile (G1). At the same time, the tooth shape of the intermediate tooth profile (G3) with the root (G1a) connected to the tooth profile of the normal tooth profile (G1) is cut off on the tooth tip (G3b) side of the intermediate tooth profile (G3). Coarse gear design method characterized by setting.

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