JP2011079077A - Gear and method for forming tooth form of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear allowing a trajectory of a contact point to be a smooth continuous curve when gears are engaged with each other, stably supplying a fluid, reducing noise during operation, allowing an enclosed space not to be formed when the gears are engaged with each other, preventing the fluid from pressing a gear structure so as not to damage a mechanical organization, and also to provide a method for forming the tooth form of the same. <P>SOLUTION: The gear (30) is formed by the method for forming the tooth form (40) of the gear (30), which includes modifying a reference rack (15) using a third-order curve (21); allowing the third-order curve (21) and the basic tooth form (16) of the reference rack (15) to contact with each other at the middle point of the dedendum part (19) of the basic tooth form (16), a middle point of a tooth surface (17), and a middle point of a tooth tip (18); forming a modified basic tooth form (22) by the third-order curve (21); obtaining a modified rack by duplicating the modified basic tooth form (22); and creating the tooth form (40) of the gear (30) using the modified rack. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a gear, in particular a gear having a continuous curve with a smooth locus of contact points of the gear, and the present invention further modifies the tooth profile of the reference rack using a method of forming the tooth profile of the gear, particularly a cubic curve. The present invention also relates to a method for creating a gear tooth profile using a correction rack.

  As shown in FIG. 1, a conventional rotary gear pump 1 includes a pump body 2 and a driving gear 3 and a driven gear 4 installed inside the pump body 2. When the drive gear 3 rotates in a certain direction, the driven gear 4 meshed with the drive gear 3 rotates in the opposite direction, thereby sending the fluid to be transported along the space between the gear teeth, and It can be discharged from the output end 5.

  In the gear, the tooth profile of the tooth portion can be created using a rack. FIG. 2 shows two mutually engaged involute gears 6 in the rotary gear pump 1. The tooth profile of the involute gear 6 includes an involute curve 8, a fillet fillet portion 9, and a tip circle 10.

  When the two involute gears 6 mesh with each other and interlock, the contact point 7 between the two gears can be connected to form a locus 11 of the contact point. As shown in FIG. 2, the locus 11 of the contact point formed by the involute gear 6 is a non-smooth continuous curve, and includes two straight line portions and two arc line portions. The straight part is formed by two involute gears 6 in contact with the involute curve 8 part of the tooth part, and the arc line part is formed by the tip circle 10 and the root fillet part 9 of the two involute gears 6 being mutually connected. It is formed when meshing. Since the tangent line where the straight line part and the arc line part of the locus 11 of the contact point are connected is not continuous, a smooth continuous curve cannot be formed. The above-mentioned locus of the contact point is not “smooth” means that the first derivative of the contact curve, that is, the tangent line of the contact curve is not continuous.

  In the rotary gear pump 1 that transports the fluid, the locus 11 of the contact point where the tangent line is not continuous causes an unstable pressure with ripples to be output to the output end 5 at the time of pumping, and during the operation of the two involute gears 6. Increase noise. In addition, because it cannot provide accurate, stable, and quantitative output, it has an impact on industries that require high precision, high quality, and high stability output, such as medical pumps. It is enormous.

  Many rotary gear pumps are also used for transporting fluids, especially for incompressible liquids. FIG. 3 shows a diagram of the meshed state when the two gears of FIG. 2 mesh and rotate. When two gears mesh with each other, when an encapsulated space 14 (encapsulation) is formed between the tooth tip 12 and the tooth root 13 of each of the two gears, that is, when the two involute gears 6 mesh with each other, two single gears are at a moment. Point contact may occur, and an accommodation space may be created between the two contact points, and the liquid in the sealed space 14 may not be discharged. That is, at the next moment when the two gears mesh with each other, the liquid in the sealed space 14 does not have compressibility, so that the gears that are completely in close contact with each other are pressed and the mechanical structure is damaged. In addition, considerable noise is generated.

  The object of the present invention is a continuous curve in which the locus of the contact point when the gears of the present invention mesh with each other is a smooth continuous curve. Therefore, the gear can stably supply fluid and reduce noise during operation. And providing a method for forming the tooth profile of the gear.

  Another object of the present invention is to form a gear and tooth form of the gear that does not form a sealed space when the gears of the present invention mesh with each other, and fluid does not compress the gear structure and damage the mechanical structure. It is to provide a method.

  In order to achieve the above-mentioned object, a method for forming a tooth profile of a gear according to the present invention obtains a reference rack based on a module of a gear to be created, and the basic tooth profile of the reference rack is a tooth surface, a tooth tip portion, a tooth root portion. And correcting the basic tooth profile of the reference rack using a cubic curve to obtain a corrected basic tooth profile, of which the cubic curve and the basic tooth profile are the midpoint of the root portion and the tooth surface A point, a step of contacting at the middle point of the tooth tip part, a step of obtaining a coefficient of the cubic curve based on the contact point, and displaying the pressure angle, total tooth depth, and tooth thickness as parameters; , Obtaining a correction rack by duplicating the above-mentioned correction basic tooth profile, and generating a gear tooth profile using the correction rack.

  In the gear of the present invention, the tooth profile of the gear is created by the above-described correction rack. The locus of the contact point of the gear set produced by the present invention is a smooth continuous curve, so that the noise during the operation of the gear can be greatly reduced and a stable output with little ripple can be obtained.

It is sectional drawing which shows the conventional rotary gear pump. It is the schematic when two involute gear sets of the conventional rotary gear pump mesh. It is the elements on larger scale which show a meshing state when the conventional gear set meshes. It is a flowchart of the formation method of the gearwheel of this invention. It is the schematic of the reference | standard rack used at step a of this invention. It is the schematic which correct | amends the basic tooth profile of FIG. 5 using a cubic curve, and forms a correction basic tooth profile. It is the schematic which shows the tolerance of this tooth profile in the tooth profile of the gear of this invention. It is the schematic which shows the locus | trajectory of the smooth continuous contact point when the gear set of this invention meshes | engages mutually. It is the elements on larger scale which show that there is no sealed space at the time of the action | operation of the gear set of this invention. It is the elements on larger scale which show that there is no sealed space at the time of the action | operation of the gear set of this invention. It is the elements on larger scale which show that there is no sealed space at the time of the action | operation of the gear set of this invention. It is the elements on larger scale which show that there is no sealed space at the time of the action | operation of the gear set of this invention.

  The following examples or description are only used to depict and interpret the essence of the invention and do not limit the invention. Detailed description and technical contents of the present invention will be described below in combination with the drawings.

As shown in the flowchart of FIG. 4, the method for forming a gear tooth profile provided by the present invention includes the following steps.
Get a reference rack based on the gear module you want to create.
Using the cubic curve, the basic tooth profile of the reference rack in step a is corrected to obtain the corrected basic tooth profile.
A correction rack is obtained by duplicating the correction basic tooth profile of step b described above, and a gear tooth profile is created using the correction rack.
Below, each step is explained in detail.

Step a in FIG. 4 obtains a reference rack based on the module m to be created. The module m is defined by the number of teeth n, the pitch circle diameter Pd, and the twist angle βp as in the following equation (1).
(1)

  Based on the module, it is possible to obtain a reference rack used to create a gear tooth profile. As shown in FIG. 5, the reference rack 15 includes a plurality of basic tooth profiles 16, and the basic tooth profile 16 includes a tooth surface 17, a tooth tip portion 18, and a tooth root portion 19.

  FIG. 6 shows the correction of the reference rack using the cubic curve in step b described above. The broken line shown in FIG. 6 represents the basic tooth profile 16 of the reference rack 15 in step a. In step b, the basic tooth profile 16 is corrected using the cubic curve 21 to obtain a corrected basic tooth profile 22. First, a rectangular coordinate (Xr, Yr) is established and the cubic curve 21 is drawn. The coordinate origin Or of the rectangular coordinate is located at the center of the tooth thickness Sw on the pitch line 20, and the pitch line 20 is co-located with the coordinate Xr axis. Is a line. The tooth depth of the reference rack 15 is h (same as the tooth depth h of the gear to be created), and the pressure angle is α.

The modified basic tooth profile 22 can be drawn using a cubic curve 21. For convenience of display, the cubic curve 21 is divided into a curved portion 21a on the Xr axis and a curved portion 21b on the Xr axis. It defines like Formula (2) and Formula (3).
(2)

(3)

Each basic tooth profile 16 of the reference rack 15 is in the middle point of the tooth root portion 19 having the coordinates (0, h / 2) in the basic tooth profile 16 and in the tooth surface 17 having the coordinates (Sw / 2, 0). The point and coordinates are in contact with the cubic curve 21 at three points including the midpoint of the tooth tip portion 18 with (Sw, -h / 2). For this reason, the coefficients of the equations (2) and (3) describing the cubic curve 21 can be solved by the following equations (4) and (5), respectively, by the three contacts described above. The modified basic tooth profile 22 can be obtained by mirroring the curve 21.
(4)

(5)

Among them, the above-mentioned tooth thickness Sw can be calculated from the above-mentioned module m, and the formula is as the following formula (6).
(6)

If the outer diameter Od and the root diameter Rd of the gear to be created are known, the pitch circle diameter Pd and the total tooth h can be calculated by the following equations (7) and (8), respectively. The pitch circle diameter Pd is an average number of the outer diameter Od and the root diameter Rd. The module m can be calculated by the equation (1) by combining the pitch angle Pd with the predetermined twist angle βp and the number of teeth n.
(7)
(8)

  In addition, the tooth thickness Sw on the pitch line 20 of the reference rack 15 can be obtained by Expression (6). The cubic thickness 21 can be obtained by substituting the tooth thickness Sw, total tooth h and pressure angle α into the equations (4) and (5), respectively, and the modified basic tooth profile 22 can be obtained by mirroring the cubic curve. Can do. In step c, the modified basic tooth profile 22 is duplicated to obtain a complete modified rack, and a gear tooth profile 40 is created using the modified rack. Since it is a well-known technique to create the gear tooth profile 40 using a rack, description thereof is omitted here. FIG. 7 illustrates that the tooth profile 40 of the gear created by the present invention can tolerate a tolerance range T of about 5% of the total tooth h.

  The method for forming a tooth profile of a gear according to the present invention can be applied to the formation of a tooth profile of a helical gear.

  The present invention also provides a gear 30. The gear tooth profile 40 is formed using the method described above and includes a tooth portion 31 that meshes with at least one corresponding gear, and the locus 32 of the contact point of the gear 30 is a smooth continuous curve. And As shown in FIG. 8, the gear 30 can be used in a rotary gear pump. In the above embodiment, it is best that the pressure angle α of the reference rack 15 is between 22 ° and 28 °, and the total tooth h of the gear is 1.5 times or less that of the module m. For this reason, when the two gears 30 mesh with each other, the sealed space 14 is not formed.

  Taking the gear 30 including the seven teeth in FIG. 8 as an example, the gear set formed using the present invention has a smooth continuous curve of the locus 32 of the contact point during rotation, and the output pressure during pumping is A phenomenon that causes ripples can be avoided.

  Tables 1 to 12 attached at the end of the description of the embodiment of the present specification show parameter examples of gears having 1 to 12 teeth. When these gears mesh with each other, the sealed space 14 is not generated. Among them, in the above table, the coordinate origin is located on the center of the pitch circle of the gear, and the coordinates (X, Y) are the coordinates of the gear. Describe the tooth profile. Taking the gear with seven teeth in Table 7 as an example, FIGS. 9A to 9D show an operating state in which the sealed space 14 is not generated when the gear meshes.

  Furthermore, the gear that forms the tooth profile using the present invention may be a helical gear. These gears can be applied to rotary gear pumps, or are better used for transporting liquids, for example, external gear pumps of helical gear sets or rotary positive displacement gear pumps.

  The above description is the best embodiment of the present invention, and does not limit the scope of protection of the patent of the present invention. All changes and modifications that have the same effect using the description and drawings of the present invention are all described. It is included in the scope of rights protection of the present invention.

DESCRIPTION OF SYMBOLS 1 Rotary gear pump 2 Pump main body 3 Drive gear 4 Driven gear 5 Output end 6 Involute gear 8 Involute curve 9 Root fillet part 10 Tooth tip circle 11 Trace of contact point 12 Tooth tip 13 Tooth base 14 Sealing space 15 Standard rack 16 basic tooth profile 17 tooth surface 18 tooth tip 19 tooth base 20 pitch line 21 cubic curve 21a, 21b curve portion 22 modified basic tooth profile 30 gear 31 tooth portion 32 contact point locus 40 tooth profile

Claims (2)

A method of forming a gear tooth profile,
A. The reference rack (15) is acquired based on the gear module to be created, and the basic tooth profile (16) of the reference rack (15) is the tooth surface (17), the tooth tip part (18), the tooth root part (19 )
B. Using the cubic curve (21), the basic tooth profile (16) of the reference rack (15) in step A is corrected to obtain the corrected basic tooth profile (22), of which the cubic curve (21) and the basic tooth profile are obtained. (16) are in contact with each other at the three points of contact between the midpoint of the tooth root (19), the midpoint of the tooth surface (17), and the midpoint of the tooth tip (18), and the cubic curve (21) And the pressure angle, total tooth depth, and tooth thickness can be displayed as parameters, of which the pressure angle is between 22 and 28 degrees, and the total tooth depth is the module. Less than 1.5 times,
C. The correction basic tooth profile (22) of Step B is duplicated to obtain a correction rack, and the gear tooth profile (40) is created using the correction rack.
A method for forming a gear tooth profile, comprising the steps of:   A gear comprising at least one tooth (31), wherein the tooth profile (40) of the tooth (31) is formed by the method according to claim 1.