JP2012172716A - Method of manufacturing shaft with gear, shaft with gear and mixer tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a shaft with a gear whose durability is improved.SOLUTION: The manufacturing method of the shaft with the gear has a step of applying precision shot peening on at least a part of an outer circumferential walls (42b, 42d) in a shaft portion (42), a step of applying precision shot peening on inner circumferential walls (44b, 46b) of gear portions (44,46) which are formed with holes (44a, 46a) and have teeth faces (44e, 46e) on at least a part of the outer walls, and a step of fixing the shaft portion subjected to the precision shot peening and the gear portion by fitting in a state where the outer circumferential walls of the shaft portion are inserted through the holes of the gear portion.

Description

  The present invention relates to a geared shaft manufacturing method, and a geared shaft and a mixer tank manufactured by the manufacturing method.

  A mixer tank for stirring a solution is used in various industrial fields. The mixer tank is composed of a motor that generates power for stirring, a speed reducer for obtaining an appropriate rotational speed from the motor, and a tank that incorporates an impeller that is rotated by the power of the motor transmitted through the speed reducer. Is done. For example, in the production of a polymer material, a mixer tank is used in a polymerization step, an agglomeration after polymerization (aggregation of latex particles after emulsion polymerization), or the like in order to stir the raw materials (Patent Document 1, etc.) reference).

Japanese Patent Laid-Open No. 10-237181

  However, in the mixer tank according to the prior art, there is a problem that the shaft or gear inside the speed reducer breaks in a time significantly shorter than the durability time assumed at the time of design. Inside the reducer, a shaft with a gear fixed to the shaft by fitting or the like is used, but such a geared shaft may be damaged in an unexpected short time, making the mixer tank safe and stable. Is impeding normal driving.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a geared shaft manufacturing method with improved durability, and a geared shaft and a mixer tank manufactured by the manufacturing method. is there.

In order to solve the above problems, the geared shaft manufacturing method according to the present invention includes a step of performing precision shot peening on at least a part of the outer peripheral wall of the shaft portion;
A step of performing precision shot peening on the inner peripheral wall of the gear portion in which a hole is formed and having a tooth surface on at least a part of the outer wall;
Fixing the shaft portion to which the precision shot peening has been performed and the gear portion by fitting in a state where the outer peripheral wall of the shaft portion is inserted into the hole of the gear portion.

  The inventors of the present invention have conducted extensive analysis on the geared shaft used in the mixer tank according to the prior art, and as a result, the geared shaft is broken at the joint between the shaft portion and the gear portion. I found out that it was caused by fretting fatigue. Fretting fatigue is a phenomenon in which wear damage (fretting wear) occurs on the contact surface due to repeated stress caused by fretting, causing fatigue failure of the member and a significant decrease in life. Further, fretting is a phenomenon in which a relative slip having a small amplitude of about 1 μm to several tens of μm occurs due to an external load on the contact surfaces of two members that are in contact with each other at a certain contact surface pressure.

  The shaft with gear according to the prior art has a joint surface between the shaft portion and the gear portion even though the safety factor (margin factor) calculated from the torsional stress and bending stress during use exceeds 1.0. The shaft part outer peripheral wall 82d of a certain attaching part 82c caused damage considered to be fatigue failure. FIG. 7 is a photograph of a shaft portion outer peripheral wall 82d that is a joint surface with the gear portion after the geared shaft according to the prior art is incorporated in a reduction gear and used for a predetermined time.

  Here, it is known that damage due to fretting fatigue increases as the contact surface pressure of the joint surface due to fitting increases, but the damage state of the shaft outer peripheral wall 82d shown in FIG. It can be seen that this corresponds to the distribution of the contact surface pressure in the shaft outer peripheral wall 82d, which is the joint surface with the portion. That is, in the shaft outer peripheral wall 82d, the contact surface pressure is highest at both axial ends of the joint surface, and the contact surface pressure is minimum in the central portion. This is most noticeable at both axial ends of the shaft outer peripheral wall 82d of the mounting portion 82c, and is slight at the center portion. For this reason, it has been found that the damage that occurs in the geared shaft according to the prior art is due to fretting fatigue.

  In the geared shaft manufacturing method according to the present invention, the precision shot peening is applied to the joint surface between the gear portion and the shaft portion, and then the gear portion and the shaft portion after the precision shot peening are fixed by fitting. The geared shaft manufactured by such a manufacturing method has excellent durability performance because fretting fatigue that occurs at the joint between the shaft portion and the gear portion is suppressed.

  The fitting method is not particularly limited, and conventional methods such as interference fitting, intermediate fitting, and gap fitting can be used. When the gear portion and the shaft portion are interference-fitted, the gear portion and the shaft portion are fixed by shrink fitting or the like.

  Further, for example, in the method for manufacturing a geared shaft according to the present invention, the difference between the hardness of the shaft portion before performing precision shot peening and the hardness of the gear portion before performing precision shot peening is Vickers hardness. It may be within 160.

  By reducing the difference in hardness between the gear portion and the shaft portion, fretting fatigue occurring at the joint portion between the shaft portion and the gear portion is suppressed, and the geared shaft manufactured by the manufacturing method as described above is Better durability performance. The difference in hardness between the gear portion and the shaft portion is preferably smaller, and the hardness of the gear portion and the shaft portion may be substantially the same (including the same).

  Further, for example, in the method for manufacturing a geared shaft according to the present invention, the gear portion may be a bevel gear.

  Since the tooth surface of the bevel gear is inclined with respect to the axial direction, the shaft having the bevel gear has a problem in that it receives a force including an axial component and easily causes axial vibration that causes fretting fatigue. However, even shafts with bevel gears are manufactured by applying precision shot peening to the joint surface between the gear part and shaft part, and then fixing the gear part and shaft part after precision shot peening by fitting. As a result, good durability performance is achieved.

  The shaft with gear according to the present invention is manufactured by any one of the manufacturing methods described above.

A mixer tank according to the present invention includes a reduction gear having the above-described geared shaft,
A motor for transmitting power to the speed reducer;
And a tank that houses therein an impeller that rotates by receiving power transmitted from the speed reducer.

  As described above, after precision shot peening is performed on the joint surface between the gear part and the shaft part, the gear part and the shaft part after precision shot peening are fixed by fitting and manufactured. The mixer tank using the speed reducer with improved durability can realize safe and stable operation.

  According to the present invention, it is possible to provide a geared shaft manufacturing method and a geared shaft manufactured by the manufacturing method, which prevent a difficult-to-predictable damage caused by fretting fatigue and has a good durability performance. Moreover, the mixer tank using such a geared shaft can realize safe and stable operation.

FIG. 1 is a schematic view of a mixer tank according to an embodiment of the present invention. FIG. 2 is a diagram showing a main part of the speed reducer in the mixer tank shown in FIG. FIG. 3A is a diagram illustrating a second shaft portion that is prepared for manufacturing the second shaft. FIG. 3B is a diagram illustrating a B gear portion prepared for manufacturing the second shaft. FIG. 3C is a diagram illustrating a C gear portion prepared for manufacturing the second shaft. Drawing 3D is a figure showing the 2nd shaft after manufacture. FIG. 4 is a flowchart illustrating a method for manufacturing the second shaft. FIG. 5 is a conceptual diagram illustrating a method of each fatigue test according to the example. FIG. 6 is a graph showing the results of each fatigue test according to the example. FIG. 7 is an enlarged photograph of a joint portion between a shaft portion and a gear portion in a reduction gear shaft according to the prior art.

  Hereinafter, although the present invention is explained based on an embodiment shown in a drawing, the present invention is not limited to it. FIG. 1 is a schematic view of a mixer tank 10 according to an embodiment of the present invention. The mixer tank 10 includes a motor 12, which is a power source, a coupling 14, a speed reducer 16, a tank 22, and the like.

  The coupling 14 joins the output shaft of the motor 12 and the input shaft (first shaft 30 (see FIG. 2)) of the speed reducer 16, and the power generated by the motor 12 is decelerated via the coupling 14. Is transmitted to the machine 16. The reducer 16 decelerates the rotation by the motor 12 to a predetermined number of rotations and outputs it. As will be described later, the speed reducer 16 includes a gear portion having a tooth surface and a plurality of shafts having a shaft portion, and the number of teeth formed on the tooth surface of each gear portion and the like rotates while being transmitted through the shaft. It has been adjusted to reduce the number. Further, the speed reducer 16 changes the rotation direction of the shaft from the horizontal direction to the vertical direction.

  An impeller 20 for agitating the fluid charged into the tank 22 is housed inside the tank 22. The power decelerated to a predetermined rotational speed by the speed reducer 16 is transmitted to the impeller 20 via an output shaft 18 and the like joined to the output shaft (the fourth shaft 60 (see FIG. 2)) of the speed reducer 16. The impeller 20 rotates in the tank 22 and agitates the fluid existing in the tank 22.

  Although the use of the mixer tank 10 is not particularly limited, the mixer tank 10 shown in FIG. 1 is particularly preferably used in an agglomeration process performed for producing a high-concentration latex. In the production process of high-concentration latex, first, an emulsion polymerization process for performing emulsion polymerization is performed, and then an agglomeration process for performing solvent agglomeration for the purpose of increasing the concentration of latex is performed. The agglomeration process is not particularly limited. For example, in the case of acrylonitrile-butadiene rubber (nitrile rubber) latex, the latex produced in the polymerization process is stirred at a higher speed in the presence of butadiene than in the emulsion polymerization. To be implemented. In the agglomeration process, it is necessary to stir the fluid in the tank at a higher speed than the stirring during emulsion polymerization, so that the load on the shaft included in the speed reducer 16 tends to increase. Therefore, the speed reducer 16 of the mixer tank 10 needs to withstand a larger load than the speed reducer of the mixer tank used in the polymerization process.

  FIG. 2 is a diagram illustrating a main part of the speed reducer 16 and illustrates a configuration of a shaft included in the speed reducer 16. The speed reducer 16 includes a first shaft 30 that is an input shaft, a second shaft 40 that is connected to the first shaft 30 via a gear, and a second shaft 40 that is connected to the second shaft 40 via a gear. 3 shaft 50 and the 4th shaft 60 connected to the 3rd shaft 50 through the gear.

  The first shaft 30 includes a first shaft portion 32 that is rotatably supported by bearings 38 and 39, and an A gear portion 34 that is inserted through a part of the first shaft portion 32. The A gear portion 34 is fixed to the end portion of the first shaft portion 32 opposite to the coupling 14 side. The A gear portion 34 of the first shaft portion 32 is a bevel gear, and has a tooth surface that is inclined with respect to the axial direction of the first shaft portion 32.

  The A gear part 34 is formed with a through hole. The A gear part 34 is formed with respect to the first shaft part 32 with a part of the outer peripheral wall of the first shaft part 32 inserted through the through hole. It is fixed by an intermediate fit. Between the A gear portion 34 and the first shaft portion 32, a key for stopping rotation is inserted. The 1st axial part 32 is arrange | positioned along the horizontal direction, and the rotating shaft of the 1st shaft 30 is a horizontal direction.

  The second shaft 40 includes a second shaft portion 42 that is rotatably supported by bearings 48 and 49, a B gear portion 44 that is inserted through a part of the second shaft portion 42, and a second shaft portion 42. And a C gear portion 46 inserted by a part of the lower side. The B gear portion 44 of the second shaft 40 meshes with the A gear portion 34 of the first shaft 30, and the rotation of the first shaft 30 is brought into contact with the second shaft 40 via the A gear portion 34 and the B gear portion 44. Communicated.

  The B gear portion 44 is a bevel gear, and the rotation axis of the second shaft 40 is a vertical direction rotated 90 degrees with respect to the rotation axis of the first shaft 30. That is, the second shaft portion 42 of the second shaft 40 is disposed along the vertical direction. The B gear portion 44 is fixed to the second shaft portion 42 by an intermediate fit. Between the B gear portion 44 and the second shaft portion 42, a key or the like for preventing rotation is inserted.

  The C gear portion 46 is a helical gear. The C gear portion 46 is also fixed to the second shaft portion 42 by an intermediate fit, and a key or the like for preventing rotation is inserted between the C gear portion 46 and the second shaft portion 42. A method for manufacturing the second shaft 40 will be described in detail later.

  The third shaft 50 includes a third shaft portion 52 that is rotatably supported by bearings 58 and 59, and a D gear portion 54 that is inserted through a part of the upper side of the third shaft portion 52. The third shaft portion 52 has an E gear tooth surface 56 formed on a part of the outer peripheral wall on the lower side of the third shaft portion 52. A through hole is formed in the D gear portion 54, and the D gear portion 54 is in a state in which a part of the outer peripheral wall of the third shaft portion 52 is inserted through the through hole with respect to the third shaft portion 52. It is fixed by an intermediate fit. Between the D gear portion 54 and the third shaft portion 52, a key for stopping rotation, a snap ring for assisting fixing, and the like are installed.

  The D gear portion 54 of the third shaft 50 meshes with the C gear portion 46 of the second shaft 40, and the rotation of the second shaft 40 is brought into contact with the third shaft 50 via the C gear portion 46 and the D gear portion 54. Communicated. The number of teeth formed on the tooth surface of the D gear portion 54 is greater than the number of teeth formed on the tooth surface of the C gear portion 46, and the rotational speed of the third shaft 50 is greater than the rotational speed of the second shaft 40. Decrease.

  The D gear portion 54 is a helical gear, and the rotation shaft of the third shaft 50 is in the vertical direction, like the second shaft 40. That is, the third shaft portion 52 of the third shaft 50 is disposed along the vertical direction. Note that the C gear portion 46 and the D gear portion 54 may be spool gears. The E gear tooth surface 56 is a helical gear, like the D gear portion 54.

  The fourth shaft 60 includes a fourth shaft portion 62 that is rotatably supported by the bearings 68 and 69, and an F gear portion 64 that is inserted through a part of the upper side of the fourth shaft portion 62. A through hole is formed in the F gear part 64, and the F gear part 64 is in a state in which a part of the outer peripheral wall of the fourth shaft part 62 is inserted through the through hole with respect to the fourth shaft part 62. And fixed by an intermediate fit.

  The F gear portion 64 of the fourth shaft 60 meshes with the E gear tooth surface 56 of the third shaft 50, and the rotation of the third shaft 50 is performed via the E gear tooth surface 56 and the F gear portion 64. 60. The number of teeth on the tooth surface of the F gear portion 64 is larger than the number of teeth on the E gear tooth surface 56, and the number of rotations of the fourth shaft 60 is smaller than the number of rotations of the third shaft 50.

  The F gear portion 64 is a helical gear, and the rotation axis of the fourth shaft 60 is in the vertical direction, like the second shaft 40 and the third shaft 50. That is, the fourth shaft portion 62 of the fourth shaft 60 is disposed along the vertical direction. Note that the E gear tooth surface 56 and the F gear portion 64 may be spool gears.

  The fourth shaft portion 62 has a hollow cylindrical shape, and the output shaft 18 (see FIG. 1) is inserted into the fourth shaft portion 62. The output shaft 18 is connected to the fourth shaft portion 62, and the rotation of the fourth shaft 60 is transmitted to the impeller 20 (see FIG. 1) in the tank 22.

  3A to 3D are diagrams illustrating the components of the second shaft 40 included in the speed reducer 16 and the second shaft 40 after they are coupled. FIG. 4 is a flowchart illustrating a method for manufacturing the second shaft. A method for manufacturing the shafts 30, 40, 50, 60 included in the speed reducer 16 will be described below using the second shaft 40 as an example with reference to FIGS. 3A to 3D and FIG. 4.

  FIG. 3A is a diagram showing a second shaft portion 42 prepared for manufacturing the second shaft 40. The second shaft portion 42 shown in FIG. 3A is a second shaft before performing precision shot peening described later. Part 42. As shown in FIG. 3A, the second shaft portion 42 before the precision shot peening is applied to the B mounting portion outer peripheral wall 42b of the B mounting portion 42a through which the B gear portion 44 is inserted and the C mounting portion through which the C gear portion 46 is inserted. 42c and the C mounting portion outer peripheral wall 42d.

  The second shaft portion 42 before the precision shot peening is preferably made of a hard metal material such as carbon steel or chrome molybdenum steel, but is not particularly limited. Although the 2nd axial part 42 before precision shot peening construction is produced by cutting or grinding, for example, it is not limited in particular. The surface of the second shaft portion 42 before the precision shot peening may be polished with a polishing paper or a polishing cloth as necessary.

  FIG. 3B is a diagram showing a B gear portion 44 prepared for manufacturing the second shaft 40, and the B gear portion 44 shown in FIG. 3B is a B gear portion 44 before performing precision shot peening described later. is there. As shown in FIG. 3B, the B gear portion 44 is formed with a B gear through hole 44 a for inserting the B attachment portion outer peripheral wall 42 b of the second shaft portion 42. The B gear portion 44 has a B gear tooth surface 44e that meshes with the tooth surface of the A gear portion 34 shown in FIG.

  3C is a diagram showing a C gear portion 46 prepared for manufacturing the second shaft 40. The C gear portion 46 shown in FIG. 3C is a C gear portion 46 before performing precision shot peening described later. is there. Similar to the B gear portion 44, the C gear portion 46 is formed with a C gear through hole 46 a through which the C mounting portion outer peripheral wall 42 d of the second shaft portion 42 is inserted. The C gear portion 46 has a C gear tooth surface 46e that meshes with the tooth surface of the D gear portion 54 shown in FIG.

  The B gear portion 44 and the C gear portion 46 before the precision shot peening are preferably made of a hard metal material such as carbon steel or chrome molybdenum steel, but are not particularly limited. However, it is preferable that the difference between the hardness of the B gear portion 44 and the C gear portion 46 before the precision shot peening construction and the hardness of the second shaft portion 42 before the precision shot peening construction is 160 or less in terms of Vickers hardness. . By reducing the difference in hardness between the B gear portion 44 and the C gear portion 46 and the second shaft portion 42, fretting occurs at the joint portion between the B gear portion 44 and the C gear portion 46 and the second shaft portion 42. This is because fatigue is suppressed. In addition, the B gear part 44 and the C gear part 46 and the second shaft part 42 before the precision shot peening are manufactured from materials having the same composition and subjected to the same heat treatment. This is preferable from the viewpoint of suppressing the fretting fatigue by reducing the hardness difference.

  The B gear portion 44 and the C gear portion 46 are produced by, for example, cutting or grinding, but are not particularly limited. The B gear inner peripheral wall 44b and the C gear inner peripheral wall 46b, which are the wall surfaces of the gear through holes 44a and 46a and are the inner peripheral walls of the gear portions 44 and 46, are polished with polishing paper or polishing cloth as necessary. The

  FIG. 4 shows a process from the preparation of the second shaft portion 42, the B gear portion 44, and the C gear portion 46 shown in FIGS. 3A to 3C to the production of the second shaft 40 shown in FIG. 3D. . In step S001 shown in FIG. 4, the second shaft portion 42 shown in FIG. 3A is prepared, and precision shot peening is performed on the second shaft portion 42 before the precision shot peening operation. Here, precision shot peening means that 20 to 200 μm fine particles having a hardness equal to or higher than that of the metal are jetted on the surface of the metal at a jetting speed of 50 m / sec or more and locally raised to the recrystallization temperature. In this process, the strengthening of the heat treatment effect and the forging effect is instantaneously repeated, and the retained austenite of the metal surface layer is converted into martensite, recrystallized, and the structure is refined. As a result, a fine structure with high hardness and toughness is formed on the metal surface, and the internal compressive residual stress can be increased.

  Since precision shot peening strikes fine particles, compressive residual stress can be increased. In addition, the metal surface subjected to precision shot peening has a very fine carbide structure, and its surface area is large and strongly tied. Therefore, it is difficult for cracks to enter the metal surface, and even if it enters, it is difficult to spread. As a method for precision shot peening, WPC treatment (registered trademark of Fuji Machine Sales Co., Ltd. and Fuji Seisakusho Co., Ltd.) is preferably used.

  In the step of performing precision shot peening of the shaft portion shown in FIG. 4 (step S001), at least the B mounting portion outer peripheral wall 42b of the B mounting portion 42a and the C mounting portion outer peripheral wall 42d of the C mounting portion 42c in the second shaft portion 42 are applied. On the other hand, precision shot peening is applied. However, in the step of performing precision shot peening of the shaft portion (step S001), precision shot peening may be performed on the entire surface of the second shaft portion 42.

  In step S002 shown in FIG. 4, a B gear portion 44 shown in FIG. 3B and a C gear portion 46 shown in FIG. 3C are prepared, and a precision shot is applied to the B gear portion 44 and the C gear portion 46 before the precision shot peening operation. Apply peening. In the step of performing precision shot peening of the gear portion shown in FIG. 4 (step S002), precise shot peening is performed on the B gear inner peripheral wall 44b of the B gear portion 44 and the C gear inner peripheral wall 46b of the C gear portion 46. . However, in the step of performing precision shot peening of the gear portion (step S002), the entire surface of the B gear portion 44 and the C gear portion 46 may be subjected to precision shot peening. Further, the precision shot peening of the B gear portion 44 and the precision shot peening of the C gear portion 46 may be performed separately or collectively.

  Further, the step of performing precision shot peening of the gear portion (step S002) may be performed simultaneously with the step of performing precision shot peening of the shaft portion (step S001), or may be performed separately. Further, in the case where the step of performing precision shot peening of the gear portion (step S002) and the step of performing precision shot peening of the shaft portion (step S001) are performed separately, the order is not limited to the example shown in FIG. Either may be done first.

  As fine particles used in the step of performing precision shot peening (step S001 and step S002), for example, metal fine particles, ceramic beads, and the like can be used, and the particle size is usually 20 to 200 μm, preferably 40 to 100 μm. Use things. Moreover, the injection speed of the high-pressure air in the step of performing precision shot peening (step S001 and step S002) is usually 50 m / sec or more, preferably 150 m / sec or more, and the injection pressure is preferably 0.2 MPa or more. In the step of performing precision shot peening (step S001 and step S002), fine shot peening is performed using metal (for example, high speed steel) fine particles as a first stage, and then fine particles of ceramic beads as a second stage. Precision shot peening may be performed using

  In step 3 shown in FIG. 4, the second shaft portion 42, the B gear portion 44, and the C gear portion 46 that have been subjected to the precision shot peening in the step of performing the precision shot peening (step S001 and step S002) are intermediately fitted. The second shaft 40 shown in FIG. 3D is obtained by fixing. By the fitting step (step S003), the B gear portion 44 is fixed to the second shaft portion 42 in a state where the B attachment portion outer peripheral wall 42b of the second shaft portion 42 is inserted into the B gear through hole 44a. The In addition, the C gear portion 46 is fixed to the second shaft portion 42 in a state where the C attachment portion outer peripheral wall 42d of the second shaft portion 42 is inserted into the C gear through hole 46a. Note that a key or the like for rotation prevention is inserted between the B gear portion 44 and the C gear portion 46 and the second shaft portion 42 during intermediate fitting.

  As shown in FIG. 3D, in the second shaft 40, the outer peripheral walls 42b and 42d of the second shaft portion 42 and the inner peripheral walls 44b and 46b of the gear portions 44 and 46, which are both surfaces facing and contacting each other by intermediate fitting. However, all are precision shot peened. As described above, after the precision shot peening is performed in advance on the surface to be the joint surface by fitting, the geared shaft manufacturing method in which the shaft portion and the gear portion are fitted and fixed is described in the manufactured geared shaft. Fretting fatigue occurring at the joint between the shaft portion and the gear portion can be suppressed. Precision shot peening is thought to have the effect of modifying the surface of a metal material into a structure with strong bonding strength, and such precision shot peening has the effect of suppressing fretting fatigue. Conceivable.

  In the above description, the manufacturing method has been described by taking the second shaft 40 as an example, but the other shafts 30, 50, 60 shown in FIG. 2 can also be manufactured by the same manufacturing method. . That is, the fixing of the A gear portion 34 to the first shaft portion 32, the fixing of the D gear portion 54 to the third shaft portion 52, and the fixing of the F gear portion 64 to the fourth shaft portion 62 also become joint surfaces by fitting. By performing precision shot peening on the surface in advance, an effect of suppressing fretting fatigue can be obtained.

  Further, the speed reducer 16 having the second shaft 40 and the like manufactured by the above-described manufacturing method can transmit power safely and stably. Further, the mixer tank 10 using the speed reducer 16 can realize safe and stable operation even when operated under a heavy load condition such as in the agglomeration process.

  Note that the second shaft portion 42 of the second shaft 40 shown in FIG. 2 is supported by bearings 48 and 49 having a smaller inner diameter than the third shaft portion 52 of the third shaft 50, and the second shaft A load larger than that of the third shaft portion 52 is easily applied to the portion 42. Therefore, in the speed reducer 16, it is possible to ensure durability by using a geared shaft that is manufactured by performing precision shot peening on the joint surface between the shaft portion and the gear portion and then fixing by fitting. It is particularly effective from the viewpoint of

  Furthermore, the 2nd shaft 40 shown in FIG.2 and FIG.3 has the B gear part 44 which is a bevel gear. Since the tooth surface of the bevel gear is tilted with respect to the axial direction, the shaft having the bevel gear receives a force including an axial component, and is liable to generate axial vibration that causes fretting fatigue. . In addition, the rotation axis of the second shaft 40 is in the vertical direction, and there is a problem that axial vibration is likely to occur due to gravity. Furthermore, the normal direction of the tooth surface of the B gear portion 44 is inclined from the horizontal direction to the vertical direction, and receiving a force from below can also cause vibration. Therefore, as the second shaft 40, it is particularly effective to employ a geared shaft that is manufactured by performing precision shot peening on the joint surface between the shaft portion and the gear portion and then fixing by fitting.

  Further, in the reduction gear 16 shown in FIG. 2, since the first shaft 30 is located on the motor 12 side, the A gear portion 34 is also likely to concentrate a load such as a sudden load at the time of starting, similarly to the C gear portion 46. Part. Further, since the first shaft 30 also has a bevel gear like the second shaft 40, it tends to easily generate axial vibration. Therefore, as the first shaft 30, it is effective from the viewpoint of ensuring durability to employ a geared shaft that is manufactured by precision shot peening on the joint surface between the shaft portion and the gear portion and then fixed by fitting. Is.

EXAMPLES Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

  In the examples, a fretting fatigue test and a normal fatigue test were performed on a test piece made of S45C (JIS G 4051: 2005), which is a carbon steel generally used as a shaft portion of a geared shaft. The effectiveness of precision shot peening on the joint surface of the geared shaft was confirmed. In the examples, three types of evaluations were performed by changing the type of fatigue test and the presence or absence of precision shot peening for the test piece and the contact piece. Table 1 shows the evaluation conditions of Comparative Example 1, Example 1, and Reference Example 1 performed in this example.

(Comparative Example 1)
As shown in Table 1, Comparative Example 1 is a fretting fatigue test using a test piece 90 made of carbon steel S45C and not subjected to precision shot peening. FIG. 5A is a conceptual diagram showing a test method of a fretting fatigue test evaluated as Comparative Example 1. FIG.

  The fretting fatigue test evaluated as Comparative Example 1 is based on the Japan Society of Mechanical Engineers (JSME) fretting fatigue test method (revised version) (JSMES 015-2009). As shown in FIG. 5A, the fretting fatigue test according to Comparative Example 1 is performed on the parallel portion 90a formed at the central portion of the test piece 90 from the direction orthogonal to the direction of the repeated stress indicated by the arrow 95. In this state, the contact piece 92 is pressed. The contact piece 92 is pressed against the parallel portion 90 a by the pressing jig 94. Note that the surfaces of the test piece 90 and the contact piece 92 used in Comparative Example 1 are polished with polishing paper.

In the fretting fatigue test according to Comparative Example 1, repeated stress was applied along the direction indicated by the arrow 95, and the number of repeated stresses N required for the test piece 90 to undergo fatigue failure was measured. The frequency of repetitive stress was 3 Hz. The distortion of the pressing jig 94 was 100 μm. The cross-sectional area of the parallel part 90a of the test piece 90 was 150 mm ² , and the pressing force of the contact piece 92 was constant. Moreover, the maximum stress of the repetitive stress (one swing stress) in Comparative Example 1 was 250, 350, and 440 MPa. In Comparative Example 1, a total of three fretting fatigue tests were performed, one for each maximum stress.

Example 1
As shown in Table 1, in Example 1, a fretting fatigue test was performed under the same conditions as in Comparative Example 1 except that the surfaces of the test piece 90 and the contact piece 92 were subjected to precision shot peening. . That is, the test piece 90 and the contact piece 92 used in Example 1 were made of carbon steel S45C in the same manner as the test piece 90 and the contact piece 92 used in Comparative Example 1, and then the surface was further subjected to precision shot peening. It has been applied. The precision shot peening performed on the test piece 90 used in Example 1 is a two-stage precision shot peening. As the first stage, the precision shot peening is performed using fine particles of high-speed steel, and the second stage. As a result, precision shot peening was performed using fine particles of ceramic beads. The particle diameters of the fine particles used in each stage were all 50 μm, the high-pressure air injection speed in precision shot peening was 200 m / sec, and the high-pressure air injection pressure was 0.4 MPa.

  Also in the fretting fatigue test according to Example 1, as in Example 1, the number of repetitions N of stress required until the specimen 90 caused fatigue failure was measured. Evaluation conditions such as the shape of the test piece 90 and the contact piece 92 and the pressing force of the contact piece 92 are the same as those in Comparative Example 1. In addition, since the dimensional change by precision shot peening is about several μm at most, it is not taken into account when calculating the shapes of the test piece 90 and the contact piece 92. In addition, the maximum stress of the repetitive stress (one-way stress) in Example 1 is 250, 275, 300, 325, 350, and 440 MPa. In Example 1, each maximum stress is performed once, for a total of 6 frettings. A fatigue test was conducted.

(Reference Example 1)
As shown in Table 1, Reference Example 1 was a normal fatigue test (JIS Z 2273: 1978) using a test piece 90 similar to that used in Comparative Example 1. FIG. 5B is a conceptual diagram illustrating a test method of a normal fatigue test performed as Reference Example 1.

  The normal fatigue test carried out as Reference Example 1 was carried out as Comparative Example 1 except that the contact piece 92 (see FIG. 5A) used in the fretting fatigue test was not used. It was performed in the same manner as the fatigue test. The manufacturing method and shape of the test piece 90 used in Reference Example 1 are the same as those in Comparative Example 1. Further, in the normal fatigue test according to Reference Example 1, similar to the fretting fatigue test according to Comparative Example 1, repeated stress was applied in the direction indicated by the arrow 97 in FIG. The frequency of the repetitive stress was 3 Hz as in Comparative Example 1. In addition, the maximum stress of the repetitive stress (one swing stress) in Reference Example 1 is 250, 275, 300, 325, 350, and 440 MPa. In Reference Example 1, the maximum stress is once for each maximum stress, which is a total of 6 normal times. A fatigue test was conducted.

Evaluation Results FIG. 6 is a SN diagram showing evaluation results according to Comparative Example 1, Example 1, and Reference Example 1, respectively. Comparing Comparative Example 1 (solid line) and Reference Example 1 (dashed line), in the test using the test piece 90 not subjected to precision shot peening, the fretting fatigue test was more effective than the normal fatigue test. It can be seen that the number of repetitions N until breakage is extremely low. This shows that, at the joint surface of the material made of carbon steel S45C, the decrease in fatigue strength due to fretting fatigue can occur faster than the decrease in fatigue strength due to normal fatigue other than fretting fatigue. Yes.

  On the other hand, Example 1 (one-dot chain line) using the test piece 90 subjected to precision shot peening is a comparative example using the test piece 90 not subjected to precision shot peening although it is the same fretting fatigue test. In contrast to 1, the number of repetitions N until breakage was greatly improved. As a result, when fretting fatigue could occur at the joint surface of the material made of carbon steel S45C, it was confirmed that significant fatigue strength could be improved by applying precision shot peening to the joint surface. .

  In addition, the improvement in fatigue strength by precision shot peening is remarkable, and Example 1 (dashed line) has a larger number of repetitions N until failure occurs than Reference Example 1 (dashed line), which is a normal fatigue test. This is because the geared shaft, for which fretting fatigue was not assumed at the time of design, was almost designed by applying precision shot peening to the joint surface even when fretting fatigue was discovered afterwards. It is possible to manufacture a geared shaft having durability against fretting fatigue that is equal to or better than that of normal fatigue other than fretting fatigue for those that are not subjected to precision shot peening without modification. Represents.

DESCRIPTION OF SYMBOLS 10 ... Mixer tank 12 ... Motor 14 ... Coupling 16 ... Reduction gear 18 ... Output shaft 20 ... Impeller 22 ... Tank 30 ... 1st shaft 32 ... 1st shaft part 34 ... A gear part 38, 39, 48, 49, 58 , 59, 68, 69 ... Bearing (bearing part)
DESCRIPTION OF SYMBOLS 40 ... 2nd shaft 42 ... 2nd axial part 42a ... B attaching part 42b ... B attaching part outer peripheral wall 42c ... C attaching part 42d ... C attaching part outer peripheral wall 44 ... B gear part 44a ... B gear through-hole 44b ... B gear Inner peripheral wall 44e ... B gear tooth surface 46 ... C gear portion 46a ... C gear through hole 46b ... C gear inner peripheral wall 46e ... C gear tooth surface 50 ... Third shaft 52 ... Third shaft portion 54 ... D gear portion 56 ... E Gear tooth surface 60 ... 4th shaft 62 ... 4th shaft part 64 ... F gear part 90 ... Test piece 90a ... Parallel part 92 ... Contact piece 94 ... Pressing jig

Claims (5)

A step of performing precision shot peening on at least a part of the outer peripheral wall of the shaft portion;
A step of performing precision shot peening on the inner peripheral wall of the gear portion in which a hole is formed and having a tooth surface on at least a part of the outer wall;
Fixing the precision shot peened shaft portion and the gear portion in a state where the outer peripheral wall of the shaft portion is inserted into the hole of the gear portion by fitting; and
Manufacturing method of shaft with gear.   The difference in hardness between the shaft portion before precision shot peening and the gear portion before precision shot peening is within 160 in terms of Vickers hardness. Manufacturing method of shaft.   The method for manufacturing a geared shaft according to claim 1, wherein the gear portion is a bevel gear.   A geared shaft manufactured by the geared shaft manufacturing method according to any one of claims 1 to 3. A speed reducer having the geared shaft according to claim 4;
A motor for transmitting power to the speed reducer;
A mixer tank having an impeller that receives the power transmitted from the speed reducer and rotates.

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