JP2016032845A - Spur gear or helical gear, and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of cutting down exceeding a base circle on a gear having a small number of teeth.SOLUTION: A spur gear 1 or helical gear is produced. First, using a reference tooth shape of a cutter corresponding to a dimension of a gear to be produced, a production calculation of the gear is performed, a tooth form of the gear to be produced is determined, then distance P in a radial direction in which, cutting down of a tooth bottom generated by the cutter exceeds the base circle and corrodes an involute curve, is calculated. Next, setting a gear module as m, R0 is calculated using a radius formula R0=7*P*m. Then, a cutter to which a radius equal to or more than R0 is multiplied, is generated on a tip part of the cutter tooth of the cutter to be used for cutting production of the gear, and using the cutter to which the R is multiplied, cutting production of the gear is performed.SELECTED DRAWING: Figure 1

Description

The present invention relates to a spur gear or a helical gear, and a method for manufacturing these gears. In particular, the present invention relates to a spur gear or a helical gear having a relatively small number of teeth and an involute tooth profile.

Spur gears and helical gears are used in various gear transmission mechanisms. Such a gear is manufactured by cutting a metal material or injection molding a resin.

When the number of gear teeth is reduced, when the tooth of the gear is created by a cutter tooth such as a rack cutter, the tip of the cutter cuts the tooth root of the gear, causing a so-called lowering, and an involute curve continuous from the tooth tip is generated. , It breaks off the base circle. FIG. 8 shows a state in which the gear 9 is cut down by the cutting created by the cutter 2. Further, FIG. 7 shows a state where an involute curve of the tooth profile is created toward the tooth tip from a position Q that is cut down and separated from the basic circle by a distance P radially outward.

In order to prevent this devaluation, it is known that the gear is created by moving the reference pitch line of the cutter away from the pitch circle of the gear by a predetermined shift amount v.
Patent Document 1 discloses a technology for suppressing gear noise by setting a dislocation coefficient to a specific value.

Japanese Patent Laid-Open No. 10-47458

When gears with a small number of teeth are cut down beyond the basic circle, the involute curve is shortened and the meshing length is reduced, which adversely affects gear transmission accuracy and noise.
Although it is possible to prevent the lowering by dislocation, there are cases where the required amount of dislocation cannot be obtained or there is a case where it is not desired to increase the amount of dislocation.
An object of the present invention is to suppress the occurrence of gear gears having a small number of teeth by means different from dislocation.

As a result of earnest study, the inventor found that when a gear was created using a cutter having a predetermined radius at the tip of the cutter tooth, the undercut did not reach the outside of the basic circle, The present invention has been completed.

The present invention is a method for manufacturing a spur gear or a helical gear, which performs a creation calculation of a gear using a reference tooth profile shape of a cutter corresponding to the specifications of the gear to be created, and uses a cutter with a reference tooth profile shape. Determine the tooth profile of the gear to be created, calculate the radial distance P at which the gear tooth bottom depressing caused by the cutter exceeds the basic circle of the gear and erodes the involute curve, and the gear module is m. = 7 * P * m R0 is calculated, and a cutter with a radius of R0 or more is created on the tip of the cutter tooth of the cutter used for cutting generation of the gear, and using the cutter with the radius, A method for producing a spur gear or a helical gear that performs cutting of a gear (first invention).
Using the gear manufactured by the manufacturing method of the first invention as a die-sculpting electrode, an injection molding die is manufactured by die-sinking electric discharge machining, and a resin gear is manufactured by performing resin injection molding using the injection molding die. You may make it like (2nd invention).

Further, the present invention is a method for generating tooth profile data of a spur gear or a helical gear, using a reference tooth profile shape of a cutter corresponding to the specifications of the gear to be created, and performing gear creation calculation, The tooth profile of the gear created by the cutter having the reference tooth profile is obtained, the radial distance P at which the undercut of the gear root generated by the cutter exceeds the basic circle of the gear and erodes the involute curve is calculated, and the gear module R0 is calculated by the formula R0 = 7 * P * m, and the tooth profile data of the cutter is created by multiplying the tip of the cutter tooth of the reference tooth profile of the cutter with a radius of R0 or more. This is a method for generating tooth profile data of a spur gear or a helical gear by performing the creation calculation of the gear using the tooth profile data of the cutter (third invention).
Using the tooth profile data generated by the method of the third invention as data for wire electric discharge machining, wire electric discharge machining is performed to produce an injection mold, and resin injection molding is performed using the injection mold. You may make it manufacture a gear manufacturing (4th invention).

Further, the present invention is a spur gear or a helical gear with a pressure angle of 14.5 °, where x is a dislocation coefficient and z is the number of teeth, and x <(26−z) / 32 is satisfied. This is a gear in which an involute curve is realized (5th invention).
Alternatively, the present invention is a spur gear or a helical gear having a pressure angle of 20 °, wherein the displacement coefficient is x and the number of teeth is z, satisfying x <(14−z) / 17, and the involute extending from the tooth tip to the basic circle. A gear having a curved line (sixth invention).

According to the first aspect of the present invention, it is possible to surely cut and create a gear in which an involute curve is realized from the basic circle to the tooth tip. Further, according to the second invention, it is possible to manufacture an injection mold using the gear cut and created by the first invention, and to injection-mold a resin gear in which an involute curve is realized from the basic circle to the tooth tip.

Further, according to the third aspect of the present invention, tooth profile data in which an involute curve is realized from the basic circle to the tooth tip can be generated even with a gear having specifications that cause a devaluation. (3) An injection mold is manufactured using the tooth profile data obtained in the invention, and a resin gear with an involute curve realized from the basic circle to the tooth tip can be injection molded.

According to the gears of the fifth and sixth inventions, an involute curve is realized on the teeth of the gear from the tip to the basic circle, and the transmission accuracy of the gear and the deterioration of noise are suppressed.

The top view of the spur gear of 1st Embodiment. The enlarged view which shows the tooth profile of the spur gear of 1st Embodiment. The figure which shows the cutter reference tooth profile shape which has not applied the round. The figure which shows the cutter shape which hung the cutter tooth tip. The schematic diagram which showed a mode that the spur gear of 1st Embodiment was cut and created with the cutter which applied the round. The graph which shows the relationship between R and P * m in an Example and a comparative example. The enlarged view which shows the tooth profile which the lowering produced beyond the basic circle in the conventional spur gear. The schematic diagram which showed a mode that a cut-down occurred beyond a basic circle in the conventional cutting creation.

Hereinafter, an embodiment of the present invention will be described with a spur gear as an example with reference to the drawings. The present invention is not limited to the individual embodiments shown below, and can be carried out by changing the form.

In FIG. 1, the front view of the spur gear 1 of 1st Embodiment of this invention is shown. The spur gear 1 is a spur gear that includes a shaft portion 14 at the center, a disc-shaped web 13 around the shaft portion 14, and teeth 10, 10 provided along the circumferential direction around the web. Here, the specific configuration of the shaft portion 14 and the web 13 can be appropriately changed based on a known technique, and is not particularly limited.

The material constituting the spur gear 1 is not particularly limited, and the spur gear 1 is formed of metal, synthetic resin, wood, or the like. The spur gear 1 can be manufactured by cutting and creating a raw material preformed in a disk shape with a cutter. Here, the cutter is a cutter for performing generation gear cutting of a spur gear or a helical gear, such as a hob cutter, a pinion cutter, or a rack cutter. When the spur gear 1 is manufactured from a synthetic resin, the spur gear 1 may be manufactured by injection molding using an injection mold having a predetermined cavity shape, as will be described later.

The teeth 10 and 10 of the spur gear 1 are formed to have an involute tooth profile. As shown in the enlarged view of the tooth profile of the tooth 10 in FIG. 2, the tooth 10 of the spur gear 1 has a tooth profile extending from the tooth tip 11 toward the tooth base 12 toward the radially inner side from the tooth tip 11. The involute curve is formed up to a position exceeding the basic circle B. FIG. 2 shows a section I where the tooth profile is an involute curved surface. In other words, in the teeth 10 and 10 of the gear 1, an involute curve is realized from the tooth tip to the basic circle.

The section I in which the tooth surface is an involute curve tooth surface reaches at least the basic circle B. Preferably, the section I reaches the inside of the base circle B in the radial direction.

The spur gear 1 has specific tooth specifications. The pressure angle α of the spur gear 1 is 20 °. The number of teeth of the gear and the dislocation coefficient are given so as to satisfy the relational expression x <(14−z) / 17 (hereinafter referred to as “relational expression 1”) where z is the number of teeth and x is the dislocation coefficient. It has been.
In the present embodiment, the number of teeth z = 8 and the dislocation coefficient x = 0.1 are given. The tooth specifications of the spur gear 1 of this embodiment satisfy the relational expression 1.

When the number of teeth and the dislocation coefficient satisfying the relational expression 1 are given, the conventional method for creating an involute gear using a cutter having a standard tooth profile, as in the gear tooth profile shown in FIG. The round-down occurs to the outer portion, and the involute curve is not realized from the basic circle like the spur gear 1 to the tooth tip. However, by adopting the tooth creation method as described in detail below, even if the tooth specifications satisfy the relational expression 1 and undercut according to the prior art, it extends from the tooth tip to the basic circle. Teeth with an involute curve can be created.

The spur gear 1 has an involute curve of the teeth 10 and 10 extending from the tooth tip to the base circle, so that the meshing of the gear is good and the transmission accuracy and noise of the gear are prevented from deteriorating.

Hereinafter, a manufacturing method for cutting and generating the spur gear 1 will be described. Cutting creation as used here refers to the involute tooth profile obtained by gear cutting with a gear cutter (hob cutter, pinion cutter, rack cutter, etc.) using the raw material (material) of the gear preformed into a disk shape. It means to form. Note that gears can be created by the same procedure when grinding and creating with a gear grinder instead of cutting with a cutter.

To create the tooth profile of the spur gear 1, the “calculation step” for calculating the degree of devaluation when creating with a cutter shape without a rounded tooth tip of the cutter, and the degree of devaluation obtained in the calculation step Accordingly, the size of the radius to be applied to the tooth tip of the cutter is obtained, and the “cutter production step” for producing a cutter with a radius applied to the cutter tooth tip, and the gear cutting by using the obtained cutter with the radius. It is performed including a “cutting creation step” for performing raw. Hereinafter, each step will be described sequentially.

First, the “calculation step” will be described. This step is not performed by actually creating a gear by cutting, but by a calculation using CAD or a gear creation program. The tooth profile of the cutter 2 used for calculation in this step is a tooth profile of a reference tooth profile shape that is not rounded. That is, in this calculation step, calculation is performed by simulating the case where cutting is performed by the conventional technique. FIG. 3 shows the tooth profile of the cutter 2 used in the calculation step. The tooth profile of the cutter 2 is defined so that a predetermined pressure angle and module can be realized. The tooth tip of the tooth profile of the cutter 2 is not substantially rounded.

The tooth profile data of the gear is created by moving the cutter 2 that is not rounded by the creation calculation along a specific locus. In the creation calculation at this step, the envelope shape of the peripheral shape of the cutter tooth profile is calculated and the gear tooth profile data is calculated as in the conventional cutting creation technique shown in FIG. And if it is a gear of the specification which satisfy | fills the relational expression 1, the tooth profile data in which rounding down exceeded the basic circle will be obtained.

Next, using the gear tooth profile data calculated by the above-described creation calculation, as shown in FIG. 7, an amount P indicating the degree of devaluation to be generated is obtained. This amount P is calculated as the radial distance P at which the gear root 92 undercut caused by the reference tooth profile cutter that is not radiused erodes the involute curve beyond the gear base circle B. In other words, in the calculated tooth 90, the tooth surface on which the involute curve is realized from the tooth tip 91 toward the tooth root continues for a predetermined length. On the outside of the circle B, the involute curve portion is interrupted, and the radially inner portion thereof becomes a root surface formed by erosion at the tooth tip of the cutter. A distance P between the point Q where the curved surface of the involute curve and the tooth bottom surface and the base circle B are separated in the radial direction is obtained as a distance P.

Next, the “cutter manufacturing step” will be described. In this step, a cutter for cutting and generating a gear is manufactured. When the distance P indicating the degree of devaluation is obtained by the above calculation, the minimum radius that should be attached to the tooth tip of the cutter that actually cuts and generates the gear based on the following formula (hereinafter referred to as “R formula”): Is calculated. Here, m is a tooth module.
R0 = 7 * P * m (R formula)

When R0 is obtained, the tooth profile of the cutter 3 that actually cuts and creates the gear is defined. The tooth profile of the cutter 3 used for cutting creation is shown in FIG. First, the tooth profile of the cutter 3 is defined so that a predetermined pressure angle and module can be realized. This shape itself is the same as the reference tooth profile shape. Then, the tooth tip portion 31 of the tooth of the cutter 3 is rounded with a radius R equal to or greater than R0 obtained earlier. In accordance with the rounded tooth profile, a cutter 3 for actually creating a cutting is manufactured. About manufacture of a cutter, what is necessary is just to perform by a well-known method.

When the cutter 3 is obtained, a gear cutting machine is used to perform a “cutting creation step” of the gear using the cutter 3 with a rounded tooth tip. In this cutting creation step, as shown in FIG. 5, the cutter teeth move relative to the gears, and the teeth 10 of the gear 1 are created. At this time, since the radius R of the predetermined size is attached to the tooth tip of the cutter tooth, it is prevented that the tooth tip of the cutter tooth scoops out the involute curved surface to the outside beyond the basic circle B. Is done. As a result, a spur gear 1 in which an involute curve is realized from the tooth tip to the basic circle as shown in FIGS. 1 and 2 is obtained by this cutting creation step.

Further, if the spur gear 1 can be cut and created, for example, the tooth portion of the spur gear 1 is cut and created by using a copper material, and the obtained tooth portion is used as a die-sculpting electrode for die-sinking electric discharge machining, and an injection mold Can be manufactured. If an injection mold can be manufactured, the spur gear 1 can be mass-produced by resin injection molding.

The present invention is not limited to the above embodiment, and can be implemented with various modifications. Other embodiments of the present invention will be described below. However, in the following description, portions different from the above embodiment will be mainly described, and detailed descriptions of the same portions will be omitted. Further, the embodiments described below can be implemented by combining some of them or replacing some of them.

In the description of the above embodiment, the spur gear has been described. However, the helical gear also satisfies the relational expression 1 through the creation process including the same calculation step, cutter manufacturing step, and cutting creation step, while satisfying the relational expression 1. A helical gear with an involute curve realized over the basic circle can be obtained.

The cutting creation process described above can also be applied to creation calculation of tooth profile data. According to the “calculation step” for calculating the degree P of the devaluation when created with a reference tooth profile cutter shape without a rounded tooth tip of the cutter, and the degree P of the devaluation obtained in the calculation step, the areal calculation formula Thus, the same process is performed until the step of obtaining the minimum radius R0 to be applied to the tooth tip of the cutter. Then, the tooth profile of the cutter is specified so that a predetermined pressure angle and module can be realized, and the radius of R0 or more obtained according to the radius calculation formula is applied to the tooth tip portion of the tooth profile of the cutter, and this is the tooth profile of the cutter tooth profile. Data. The tooth profile data of the gear can be obtained by performing the creation calculation of the gear as shown in FIG. 5 using the cutter tooth profile data.

By the above-described creation calculation process, tooth profile data of the spur gear 1 in which the involute curve is realized from the tooth tip to the basic circle while satisfying the relational expression 1 is obtained. It can be manufactured by electric discharge machining. Alternatively, by using the tooth profile data, wire electric discharge machining is performed to manufacture an injection mold, and a resin is injection molded by the mold, whereby the spur gear 1 can be mass-produced.

In the description of the above embodiment, the gear has a pressure angle of 20 ° and satisfies the relational expression 1. However, the pressure angle of the gear may be 14.5 °. When the pressure angle is 14.5 °, the condition for occurrence of devaluation changes. Therefore, instead of the relational expression 1, the following relational expression 2: x <(26−z) / 32 is used. In the prior art, in the case of a tooth specification that satisfies this equation, a devaluation exceeding the basic circle occurs.

Even if the pressure angle of the gear is 14.5 °, the calculation of the distance P indicating the degree of devaluation is similarly performed by generating calculation using a cutter having a reference tooth profile. The minimum radius R0 that should be attached to the tooth tip of the cutter may be determined by the same radius calculation formula (R0 = 7 * P * m). For example, similarly, it is possible to obtain a gear in which an involute curve is realized from the tooth tip to the basic circle while satisfying the relational expression 2.

Note that the pressure angle may be another angle. In this case, if a devaluation exceeding the basic circle occurs in the calculation step, R0 is calculated using the R calculation formula according to the degree P of the devaluation. The same processing may be performed.

Examples are shown below.
Tables 1 and 2 show the specifications of the gears of Examples 1 to 9 which are embodiments of the invention. Table 1 shows an example with a pressure angle of 20 °, and Table 2 shows an example with a pressure angle of 14.5 °. In each embodiment, a predetermined number of teeth z, a module m, and a dislocation coefficient x are given. In the table, in each example, the devaluation amount P exceeding the basic circle created by the cutter that is not multiplied by the devaluation amount calculation step, and the minimum deduction R0 calculated by the R calculation formula are shown. Yes. Further, in each example, the size R of the tip radius applied to the tip of the tooth of the cutter creating the gear, which is set to be equal to or higher than R0, is shown in the table.

In these examples, in any of the examples, there was no occurrence of rounding down beyond the basic circle (to the outside of the basic circle), and the tooth of the gear realized an involute curve from the tooth tip to the basic circle. .

Tables 1 and 2 show comparative examples corresponding to the respective examples. In the example and the comparative example, the numbers of the examples are the same (for example, in the example 1 and the comparative example 1), and the number of teeth z, the module m, and the dislocation coefficient x are common. The presence or absence of the radius of the tip of the cutter and the size of the radius are different. Specifically, in contrast to the examples, in the comparative example, there is no radius at the tip of the cutter when creating the tooth (indicated in the table as R = 0), and the radius calculation is performed for the corresponding example. A radius smaller than R0 calculated by the equation is applied.
As shown in Table 1 and Table 2, in both comparative examples, as in the prior art, a devaluation occurs due to the tip of the cutter, and the devaluation exceeds the basic circle (to the outside of the basic circle). It was.

FIG. 6 is a graph showing the relationship between R and P * m in these examples and comparative examples. The product P * m of P and module m calculated through the calculation step is plotted on the horizontal axis, and the radius R of the cutter tooth tip is plotted on the vertical axis for each example and comparative example. Examples are indicated by white circles and comparative examples by black circles. The diagonal line in the figure is a straight line representing the R calculation formula R0 = 7 * P * m. That is, in an embodiment in which a radius that is larger than R0 calculated by the radius calculation formula is multiplied by the tip of the cutter, rounding down exceeding the basic circle does not occur, and R0 calculated by the radius calculation formula does not occur. In the comparative example in which only a small radius is applied or no radius is applied, it can be confirmed that the devaluation occurs beyond the base circle.

The gear according to the present invention can be used for various transmission mechanisms and has high industrial utility value.

1 Gear 10 Tooth 11 Tooth tip 12 Tooth root 13 Web 14 Shaft B Basic circle I Section where involute curve is realized 2 Cutter (reference tooth profile, no radius)
3 Cutter (Rug on the cutter teeth)
9 gear 90 tooth 91 tooth tip 92 tooth base

Claims (6)

A method of manufacturing a spur gear or a helical gear,
Using the reference tooth profile of the cutter corresponding to the specifications of the gear to be created, the gear creation is calculated, the tooth profile of the gear created by the cutter of the reference tooth profile is obtained, and the gear teeth generated by the cutter Calculating the radial distance P at which the bottom devaluation erodes the involute curve beyond the base circle of the gear;
R0 is calculated by the equation R0 = 7 * P * m, where m is the gear module.
Create a cutter with a radius of R0 or more on the tip of the cutter tooth of the cutter used for gear cutting creation,
Using the rounded cutter, create the cutting of the gear,
A method of manufacturing a spur gear or a helical gear. A gear manufactured by the manufacturing method according to claim 1 is used as a die-sculpting electrode, an injection molding die is manufactured by die-sinking electric discharge machining, and resin injection molding is performed by the injection molding die. How to manufacture. A method for generating tooth profile data of a spur gear or a helical gear,
Using the reference tooth profile of the cutter corresponding to the specifications of the gear to be created, the gear creation is calculated, the tooth profile of the gear created by the cutter of the reference tooth profile is obtained, and the gear teeth generated by the cutter Calculating the radial distance P at which the bottom devaluation erodes the involute curve beyond the base circle of the gear;
R0 is calculated by the equation R0 = 7 * P * m, where m is the gear module.
Create the tooth profile data of the cutter with the radius of R0 or more applied to the tip of the cutter tooth of the standard tooth profile of the cutter,
Using the tooth profile data of the cutter that has been rounded, perform the creation calculation of the gear,
A method for generating tooth profile data of a spur gear or a helical gear. The tooth profile data generated by the method according to claim 3 is used as data for wire electric discharge machining, wire electric discharge machining is performed to produce an injection mold, and resin injection molding is performed using the injection mold. A method of manufacturing a resin gear. A spur gear or a helical gear with a pressure angle of 14.5 °,
X <(26−z) / 32 is satisfied, where x is the dislocation coefficient and z is the number of teeth.
A gear that realizes an involute curve from the tooth tip to the base circle. A spur gear or a helical gear with a pressure angle of 20 °,
X <(14-z) / 17 is satisfied, where x is the dislocation coefficient and z is the number of teeth.
A gear that realizes an involute curve from the tooth tip to the base circle.

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