JP7639648B2 - Shaft manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a shaft having a tapered flat knurled surface.

Shafts used in wiper devices include the output shaft of the wiper motor that is connected to the crank that constitutes the wiper link mechanism, and the pivot shaft that is connected to the wiper arm. Output shafts and pivot shafts are, for example, given a tapered flat knurl on their axial ends in order to connect them to the attached members such as the crank and wiper arm in a manner that prevents them from rotating relative to each other.

An example of a shaft having a connecting portion formed of a tapered flat knurl at the axial end is disclosed in, for example, Patent Document 1. Note that the pivot shaft and the knurl are described as the drive shaft and the serration, respectively, in Patent Document 1.

Patent No. 2614394

To create a tapered flat knurled connection at the axial end of a shaft, for example, a rolling die is placed at an angle against the intended location of the axial end of the shaft. The unevenness of the die bites into the intended location of the connection, causing plastic deformation and creating the unevenness of the knurl.

At this time, the material of the concave portion of the knurling moves to create a convex portion, which can cause a part of the convex portion to protrude further outward from the outer periphery of the shaft's main body at the boundary with the shaft's main body. In the subsequent shaft assembly process, when the shaft is inserted into a cylindrical bearing from the end side having the connecting portion, the part protruding from the outer periphery of the shaft's main body may come into contact with the bearing, which may damage the bearing or make it impossible to insert the bearing. This requires post-processing such as removing unnecessary parts that protrude from the outer periphery of the shaft's main body that may arise when the knurling is made, making shaft manufacturing cumbersome.

The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a method for manufacturing a shaft that can omit post-processing of a connecting portion that is to be formed with a knurl.

The shaft that solves the above problem is a shaft (23, 14, 15) for a wiper device that has a connecting portion (32) with a tapered flat knurl on the outer circumferential surface (32c) for attaching a workpiece (27, 18, 19) so that the workpiece cannot rotate relative to the shaft, and is configured with a recess (33) that is recessed radially inward between the large diameter portion of the connecting portion and the main body of the shaft so that the inclination of the outer circumferential surface of the connecting portion toward the outer circumferential surface (23b, 14b, 15b) of the main body of the shaft is a shape that is halfway inclined, and the large diameter portion (32b) of the connecting portion is positioned inside the outer circumferential surface of the main body of the shaft.

According to the above configuration, a recess is provided between the large diameter portion of the connecting portion and the main body of the shaft at the connecting portion of the shaft on which the knurling is to be made. By setting the recess to have a shape that is partway inclined on the outer circumferential surface of the connecting portion toward the outer circumferential surface of the main body of the shaft, the large diameter portion of the connecting portion is positioned inward from the outer circumferential surface of the main body of the shaft. In other words, no unnecessary portion protruding from the outer circumferential surface of the main body of the shaft is generated at the connecting portion, and post-processing such as cutting off the unnecessary portion can be omitted. In addition, since the recess can be made at the same time as the planned production site of the connecting portion where the knurling is to be made is pre-produced in the shaft material, the feared increase in the number of new processes for producing the recess is suppressed.

The method for manufacturing a shaft that solves the above problem is a shaft (23, 14, 15) for a wiper device that has a connecting portion (32) having a tapered flat knurl on its outer circumferential surface (32c) for attaching a mounting member (27, 18, 19) so that the mounting member cannot rotate relative to the shaft, and the inclination of the outer circumferential surface of the connecting portion toward the outer circumferential surface (23b, 14b, 15b) of the shaft body (23a, 14a, 15a) is a shape in the middle of the inclination, and the large diameter portion (32b) of the connecting portion is formed on the shaft. The method for manufacturing a shaft further includes a recess (33) formed by recessing the area between the large diameter portion of the connecting portion and the main body of the shaft radially inward so as to be located inside the outer circumferential surface of the main body of the shaft, and includes a first step of manufacturing the intended area (32α) of the connecting portion and the recess in the shaft material (36) for manufacturing the shaft, and a second step of performing tapered flat knurling on the intended area of the connecting portion.

According to the above configuration, a recess is provided between the large diameter portion of the connecting portion and the main body of the shaft so that no unnecessary portion protruding from the outer circumferential surface of the main body of the shaft is generated at the connecting portion where the knurling is to be made. In this case, the recess is made at the same time as the planned production site of the connecting portion where the knurling is to be made is made in advance in the shaft material, so the feared increase in the number of new processes for making the recess is suppressed.

1 is a diagram illustrating an overall configuration of a wiper device according to an embodiment; FIG. 4 is a diagram showing an assembled state of the shaft in the embodiment. FIG. 4 is an exploded view showing a state before the shaft is assembled in the embodiment. 11A to 11C are explanatory diagrams for explaining a manufacturing process of the shaft in the same embodiment. 11A to 11C are explanatory diagrams for explaining a manufacturing process of the shaft in the same embodiment. FIG. 11 is a configuration diagram showing an assembled state of a shaft in a comparative example. FIG. 11 is an exploded view showing a state before assembly of a shaft in a comparative example.

An embodiment of a shaft and a method for manufacturing the shaft will now be described.
[Overall configuration of wiper device]
The wiper device 10 of this embodiment shown in FIG. 1 is intended to wipe the windshield (not shown) of an automobile, and is installed on a mounting portion (not shown) on the vehicle body side below the windshield.

The wiper device 10 includes a pair of pivot holders 11, 12. The pivot holders 11, 12 are connected to each other by a connecting frame 13 to form an integral structure. The pivot holders 11, 12 each have an attachment portion 11a, 12a. The pivot holders 11, 12 are attached to an attachment portion on the vehicle body side by the attachment portion 11a, 12a.

Each pivot holder 11, 12 supports pivot shafts 14, 15 in a rotatable manner by inserting the pivot shafts 14, 15. A first end of a pivot lever 16, 17 is fixed to the base end of each pivot shaft 14, 15. Each pivot shaft 14, 15 rotates back and forth based on the swinging of each pivot lever 16, 17 within a predetermined angle range. The base end of a wiper arm 18, 19 is attached to the tip end of each pivot shaft 14, 15. Each wiper arm 18, 19 swings back and forth based on the swinging of each pivot shaft 14, 15, and the wiper blades (not shown) connected to the tip end of each wiper arm 18, 19 wipe the windshield back and forth.

The wiper motor 20, which is the drive source of the wiper device 10, is attached to the connecting frame 13. The wiper motor 20 is composed of a motor section 21 and a speed reducer section 22 assembled together. The wiper motor 20 reduces the rotational drive of the motor section 21 in the speed reducer section 22 and outputs it from the output shaft 23 provided in the speed reducer section 22. The wiper motor 20 is configured such that the axis L1 of the motor section 21 and the axis L2 of the output shaft 23 of the speed reducer section 22 are perpendicular to each other in a side view. The wiper motor 20 is arranged so that the axis L1 of the motor section 21 is aligned along the longitudinal direction of the connecting frame 13 and the axis L2 of the output shaft 23 is oriented in substantially the same direction as the pivot shafts 14 and 15. The housing 24 of the speed reducer section 22 is fixed to the connecting frame 13 using a fastening member 25 and a mounting plate 26. In addition to the mounting portions 11a, 12a of the pivot holders 11, 12 described above, the housing 24 of the speed reducer 22 is also provided with a mounting portion 20a for mounting the wiper motor 20 to a mounting portion on the vehicle body side.

A first end of a crank 27 is attached to the tip of the output shaft 23. A first end of a drive rod 28 is connected to a second end of the crank 27. A second end of the drive rod 28 is connected to a second end of the pivot lever 16. The second ends of the pivot levers 16, 17 are connected to each other by a link rod 29.

When the crank 27 rotates in one direction by driving the output shaft 23 of the wiper motor 20, the pivot lever 16 swings via the drive rod 28. When the pivot lever 16 swings, the pivot lever 17 also swings via the link rod 29. The pivot shafts 14 and 15 rotate together based on the synchronized swinging of the pivot levers 16 and 17, and the wiper arms 18 and 19 swing together to perform the wiping action of the wiper.

[Detailed configuration of output shaft]
As shown in Figures 2 and 3, the tip portion of the output shaft 23 in this embodiment is provided with a threaded portion 31, a connecting portion 32, and a recessed portion 33 in this order from the tip side, and the recessed portion 33 is adjacent to the main body portion 23a of the output shaft 23.

The threaded portion 31 is configured as a male screw with a thread formed on its outer circumferential surface 31a. After the crank 27, which is the member to be attached, is attached to the connecting portion 32 adjacent to the threaded portion 31, a nut 34 is attached to the threaded portion 31. By attaching the nut 34 to the threaded portion 31, the crank 27 is attached so that it is sandwiched between the connecting portion 32, which has a tapered shape (more specifically, a truncated cone shape), and the nut 34.

The connecting portion 32 is configured with a tapered flat knurling. That is, the connecting portion 32 is tapered with a small diameter portion 32a on the side where the threaded portion 31 is located and a large diameter portion 32b on the side where the recessed portion 33 is located. The small diameter portion 32a of the connecting portion 32 is approximately flush with the crank 27 in the attached state. The large diameter portion 32b of the connecting portion 32 is set to be smaller radially inward by a dimension D1 than the main body portion 23a of the output shaft 23. The taper angle θ1 of the connecting portion 32 is set to the same angle as the taper angle θ2 of the connecting hole 27a of the crank 27. The connecting portion 32 has triangular irregularities on its outer circumferential surface 32c, which are alternately configured at equal intervals in the circumferential direction. In addition, the knurling irregularities created on the outer circumferential surface 32c of the connecting portion 32 extend linearly along the axial direction when viewed from the side of the output shaft 23. The knurling grooves and protrusions of the connecting portion 32 are made continuously throughout the entire area from the small diameter portion 32a to the large diameter portion 32b. The method of making the knurling of the connecting portion 32 will be described later.

The connecting hole 27a of the crank 27, which connects to the connecting portion 32, also has a tapered flat knurling on the inner surface 27b. The crank 27 is attached so that the concave and convex knurling of its own connecting hole 27a and the connecting portion 32 of the output shaft 23 mesh with each other. In this case, the concave and convex knurling of the connecting portion 32 is completely created from the small diameter portion 32a to the large diameter portion 32b, so that the meshing with the connecting hole 27a of the crank 27 is deep and the connection between them is strong. In this way, the crank 27 is attached to the connecting portion 32 of the output shaft 23 so that it cannot rotate relative to it.

The recessed portion 33 is recessed from the outside to the inside in the radial direction of the output shaft 23 between the large diameter portion 32b of the connecting portion 32 where the knurling is made and the main body portion 23a of the output shaft 23. By providing the recessed portion 33 between the connecting portion 32 and the main body portion 23a of the output shaft 23, the large diameter portion 32b of the connecting portion 32 is located inward by a dimension D1 from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23 without changing the taper angle θ1 of the connecting portion 32. In other words, when the connecting portion 32 is knurled, plastic deformation occurs in which the convex portion rises, but even the convex portion of the large diameter portion 32b of the connecting portion 32, which has the largest diameter, does not protrude from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23. In addition, since the taper angle θ1 of the connecting portion 32 is not changed, the output shaft 23 is highly versatile.

Here, Figs. 6 and 7 show an output shaft 23x of a comparative example. The output shaft 23x does not have the recessed portion 33 of the output shaft 23 of this embodiment, and is provided with a threaded portion 31 and a connecting portion 32 in this order from the tip side, and the connecting portion 32 is adjacent to the main body portion 23a of the output shaft 23x. In other words, the output shaft 23x of the comparative example has a commonly used configuration. A tapered flat knurl is made on the connecting portion 32. The connecting portion 32 has the same taper angle θ1 as this embodiment.

In the comparative example, when the knurling is made for the connecting portion 32, a part of the knurling protruding portion may protrude further outward from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23x at the boundary with the main body portion 23a of the output shaft 23x. Therefore, post-processing such as cutting off the unnecessary portion 32x protruding from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23x at the connecting portion 32 is necessary. In other words, in the later assembly process of the output shaft 23x in the wiper motor 20, when the cylindrical bearing 35 fixed to the housing 24 is inserted from the tip side of the output shaft 23x, the unnecessary portion 32x hits the bearing 35. Incidentally, it is also possible to stop making the knurling concave portion before the boundary so that the unnecessary portion 32x does not protrude from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23 at the boundary with the main body portion 23a of the output shaft 23, thereby suppressing the rise of the protruding portion. However, in this case, the grooves of the knurling may not extend all the way through in the longitudinal direction, resulting in a shallow engagement of the crank 27 with the connecting part 32 at the end of the grooves.

In contrast to the above, the output shaft 23 of this embodiment shown in Figures 2 and 3 allocates a part of itself, which was the connecting portion 32 in the comparative example, to the recessed portion 33. In other words, when the taper angle θ1 of the connecting portion 32 is maintained, the inclination mode of the outer peripheral surface 32c of the connecting portion 32 toward the outer peripheral surface 23b of the main body portion 23a of the output shaft 23 becomes a shape in the middle of the inclination due to the setting of the recessed portion 33, and the outer diameter of the large diameter portion 32b is set to be smaller than that of the comparative example. Therefore, even if a knurl is made on the connecting portion 32, the convex portion of the large diameter portion 32b of the connecting portion 32 does not protrude from the outer peripheral surface 23b of the main body portion 23a of the output shaft 23. In other words, the dimensions of the recessed portion 33 are set so that the convex portion of the large diameter portion 32b of the connecting portion 32 does not protrude from the outer peripheral surface 23b of the main body portion 23a of the output shaft 23. In the output shaft 23 of this embodiment, even if the connecting portion 32 is knurled, no unnecessary portion protruding from the outer circumferential surface 23b of the main body 23a of the output shaft 23 is generated in the connecting portion 32. As a result, even if the bearing 35 fixed to the housing 24 is inserted from the tip side of the output shaft 23 in the subsequent assembly process of the output shaft 23, the output shaft 23 can be inserted without post-processing.

[Manufacturing of output shaft]
As shown in FIG. 4, when manufacturing the tip portion of the output shaft 23, a rod-shaped shaft material 36 for manufacturing the output shaft 23 is used.

In the first step, the tip end of the shaft material 36 is fabricated in a single step using turning, cold forging, and the like to fabricate the region 31α of the threaded portion 31, the region 32α of the connecting portion 32, and the recessed portion 33. The region 31α of the threaded portion 31 is fabricated in a cylindrical shape with a smooth outer circumferential surface 31a0. The region 32α of the connecting portion 32 is fabricated in a tapered shape with a smooth outer circumferential surface 32c0.

The taper angle θ0 of the planned preparation portion 32α of the connecting portion 32 is set to be smaller than the taper angle θ1 of the connecting portion 32 after the knurling is prepared as shown in FIG. 5. The planned preparation portion 32α of the connecting portion 32 is formed in a shape that is continuous with the recessed portion 33 without any steps. That is, the large diameter portion 32b0 of the planned preparation portion 32α of the connecting portion 32 is located inward from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23 by a dimension D0, which is larger than the dimension D1 of the large diameter portion 32b of the connecting portion 32 after the knurling is prepared as shown in FIG. 5.

Next, in the second step, as shown in Figures 4 and 5, the threaded portion 31 is created in the planned production area 31α. Note that the threaded portion 31 may be created after the knurling is created in the planned production area 32α of the connecting portion 32.

After or before the threaded portion 31 is made, a tapered flat knurling process is performed on the planned portion 32α of the connecting portion 32, and a knurl is made on the connecting portion 32. A known rolling die (not shown) is applied to the outer peripheral surface 32c0 of the planned portion 32α of the connecting portion 32 to perform the knurling process. Plastic deformation occurs on the outer peripheral surface 32c0 of the connecting portion 32, in which the material of the concave portion of the knurl moves to the convex portion, creating the unevenness of the knurl. After the knurling is made, the connecting portion 32 protrudes radially outward due to the rise of the convex portion of the knurl.

In this case, since the output shaft 23 of this embodiment is provided with a recessed portion 33 in advance, even the protruding portion of the large diameter portion 32b, which has the largest diameter of the connecting portion 32, does not protrude from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23. Therefore, no unnecessary portions are generated in the connecting portion 32 of this embodiment, and it is possible to omit the post-processing step of removing the unnecessary portions, which was performed in the comparative example. This simplifies the manufacturing process of the output shaft 23. In this manner, the output shaft 23 of this embodiment is manufactured.

[Effects of this embodiment]
The effects of this embodiment will be described.
(1) In the connecting portion 32 of the output shaft 23 on which the knurling is to be produced, a recess 33 is provided between the large diameter portion 32b of the connecting portion 32 and the main body portion 23a of the output shaft 23. The inclination of the outer circumferential surface 32c of the connecting portion 32 toward the outer circumferential surface 23b of the main body portion 23a of the output shaft 23 is set to a shape that is midway inclined by setting the recess 33, so that the large diameter portion 32b of the connecting portion 32 is positioned inward from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23. In other words, no unnecessary portion that protrudes from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23 is generated in the connecting portion 32, and post-processing such as cutting off the unnecessary portion can be omitted.

(2) The recess 33 is created at the same time that the planned portion 32α of the connecting portion 32 where the knurling is to be created is created in advance in the shaft material 36. This prevents the fear of an increase in the number of new processes required to create the recess 33 from occurring.

(3) The planned fabrication portion 32α of the connecting portion 32 and the recessed portion 33 are fabricated in a shape that is continuous and without any steps. In other words, the shape that spans the planned fabrication portion 32α of the connecting portion 32 and the recessed portion 33 is a relatively simple shape, which makes processing easy.

(4) The taper angle θ0 of the planned preparation portion 32α of the connecting portion 32 is set to be smaller than the taper angle θ1 of the connecting portion 32 after the knurling is prepared. In other words, the shape of the connecting portion 32 spanning the planned preparation portion 32α and the recessed portion 33 can be made relatively simple, while the knurling can be more appropriately prepared for the connecting portion 32.

[Example of change]
This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

The shapes of the output shaft 23 having the connecting portion 32 and the recessed portion 33 in the above embodiment, and the intended manufacturing portion 32α of the connecting portion 32 manufactured from the shaft material 36, are merely examples and may be changed as appropriate.

- In the above embodiment, application to the output shaft 23 was shown, but the tip portions of the pivot shafts 14, 15 shown in Figures 1 to 3 may also be manufactured using the same configuration and manufacturing process as the tip portion of the output shaft 23.

Specifically, the pivot shafts 14 and 15 are provided with a threaded portion 31, a connecting portion 32, and a recessed portion 33 in this order from the tip side, and each recessed portion 33 is adjacent to the main body portion 14a, 15a of each pivot shaft 14, 15. The connecting portion 32 of each pivot shaft 14, 15 has a tapered flat knurl on the outer circumferential surface 32c. The wiper arms 18, 19, which are the attached members, are attached to the connecting portion 32 of each pivot shaft 14, 15 so that they cannot rotate relative to each other. The wiper arms 18, 19 have connecting holes 18a, 19a on their inner circumferential surfaces 18b, 19b, which are also tapered flat knurls. The wiper arms 18, 19 are attached so that the knurled projections of their own connecting holes 18a, 19a and the connecting portion 32 of each pivot shaft 14, 15 mesh with each other.

The connecting portions 32 of the pivot shafts 14, 15 do not have unnecessary portions that protrude from the outer circumferential surfaces 14b, 15b of the main bodies 14a, 15a. Therefore, even in the case where the bearings 35 fixed to the pivot holders 11, 12 are inserted into the pivot shafts 14, 15 from their tip ends in the subsequent assembly process, the pivot shafts 14, 15 can be inserted without any post-processing. The pivot shafts 14, 15 also have the same effect as the output shaft 23 described above.

- The wiper device 10 in the above embodiment is configured to connect the output shaft 23 of the wiper motor 20 to the crank 27 of the link mechanism, but it may also be configured to directly connect the output shaft 23 of the wiper motor 20 to the wiper arm 18 (, 19).

- The wiper device 10 in the above embodiment is configured to perform a typical arc-shaped wiping action, but it may also be a wiper device incorporating a four-link mechanism to perform a non-arc-shaped wiping action. In that case, it may be applied to the shaft for mounting the wiper arm 18 (, 19) provided on the four-link mechanism.

[Additional Notes]
The technical ideas that can be understood from the above-described embodiment and modified examples will be described.
(A) A shaft having a connecting portion having a tapered flat knurling on its outer circumferential surface for mounting a workpiece so as to prevent the workpiece from rotating relative to the workpiece,
A shaft having a recess formed by recessing the area between the large diameter portion of the connecting part and the main body of the shaft radially inward so that the inclination pattern of the outer circumferential surface of the connecting part toward the outer circumferential surface of the main body of the shaft is an intermediate inclination shape and the large diameter portion of the connecting part is positioned inward from the outer circumferential surface of the main body of the shaft.

(B) A shaft having a connecting portion having a tapered flat knurling on its outer circumferential surface for mounting a workpiece so as to prevent the workpiece from rotating relative to the workpiece.
a recessed portion is further provided by recessing a portion between the large diameter portion of the connecting portion and the main body of the shaft radially inward so that the inclination of the outer circumferential surface of the connecting portion toward the outer circumferential surface of the main body of the shaft is an intermediate inclination shape and the large diameter portion of the connecting portion is located inward from the outer circumferential surface of the main body of the shaft,
a first step of forming a portion for forming the connecting portion and the recessed portion in a shaft material for producing the shaft;
A second step of performing a tapered flat knurling process on the portion to be manufactured of the connecting portion;
A method for manufacturing a shaft comprising:

The above shaft and shaft manufacturing method can be applied not only to wiper devices but also to shafts used for other devices, and the same effects can be obtained.

14, 15 pivot shaft (shaft), 14a, 15a main body, 14b, 15b outer circumferential surface, 18, 19 wiper arm (attached member), 23 output shaft (shaft), 23a main body, 23b outer circumferential surface, 27 crank (attached member), 32 connecting portion, 32b large diameter portion, 32c outer circumferential surface, 33 recessed portion

Claims (3)

A shaft (23, 14, 15) for a wiper device, comprising a connecting portion (32) having a tapered flat knurl on an outer circumferential surface (32c) for mounting a mounting member (27, 18, 19) such that the mounting member cannot rotate relative to the connecting portion,
a recess (33) is further provided by recessing a portion between the large diameter portion (32b) of the connecting portion and the main body portion of the shaft radially inward so that the inclination mode of the outer circumferential surface of the connecting portion toward the outer circumferential surface (23b, 14b, 15b) of the main body portion (23a, 14a , 15a) of the shaft is an intermediate inclination shape and the large diameter portion (32b) of the connecting portion is located inward from the outer circumferential surface of the main body portion of the shaft, and the shaft is configured such that the recess is adjacent to the main body portion of the shaft,
A first step of preparing a portion (32α) for preparing the connection portion and the recessed portion in a shaft material (36) for preparing the shaft;
A second step of performing a tapered flat knurling process on the portion to be manufactured of the connecting portion;
Equipped with
A method for manufacturing a shaft, wherein a taper angle (θ0) of a planned portion of the connecting portion to be created in the first step is set to be smaller than a taper angle (θ1) of the connecting portion after the knurling is created in the second step . The method for manufacturing a shaft according to claim 1 , wherein in the first step, the region where the connecting portion is to be manufactured and the recessed portion are manufactured to have a shape that is continuous without any step. 3. The method for manufacturing a shaft according to claim 1, wherein the shaft is provided with a threaded portion (31) consisting of a male screw, the connecting portion, and the recessed portion in this order from a tip end portion.

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