JP2021123205A - Steering device - Google Patents

Abstract

To provide an inexpensive electric power steering device.SOLUTION: A steering device 10 comprises a cylindrical follower pulley 17 fitted to a ball screw nut 14 and coupled via a toothed belt 18 to an electric motor 15 to transmit drive force to the ball screws nut. The follower pulley 17 has a flange 19 coupled to the toothed belt 18 in a large-diameter portion 17b in an axial direction and for preventing the toothed belt 18 from falling off a groove 17e circumferentially provided in a small-diameter portion 17c of an end of the large-diameter portion 17b. The flange 19 is reduced in the inside diameter of an inner peripheral portion 19a by plastic deformation caused by its being pressed in the axial direction and is fixed in position by the inner peripheral portion 19a entering the groove 17e.SELECTED DRAWING: Figure 3

Description

The present invention relates to a steering device.

Conventionally, for example, an electric power steering device disclosed in Patent Document 1 below has been known. This conventional electric power steering device includes a speed reduction device using a toothed belt. The speed reducer has a flange member that is inserted into a mounting hole provided in the pulley body of the toothed pulley to prevent the toothed belt from falling off the toothed pulley. The flange member is adapted so that the insertion end of the mounting shaft portion inserted into the mounting hole of the pulley body is crimped to the locking portion provided on the inner circumference of the mounting hole.

Japanese Unexamined Patent Publication No. 2013-226880

By the way, in the above-mentioned conventional electric power steering device, it is necessary to form a flange portion that prevents the cylindrical flange member from coming off by coming into contact with the toothed belt, and an insertion end that is crimped to the locking portion. There is. In this case, the flange portion and the insertion end extend outward in the radial direction with respect to the cylindrical mounting shaft portion.

Therefore, the shape of the flange member is complicated, and the number of steps for processing the flange portion and the insertion end is increased. Further, when caulking the insertion end extending outward in the radial direction to the locking portion formed on the inner peripheral surface of the pulley body, for example, the insertion end is once reduced in diameter and attached. Since it is necessary to insert it into the hole, extremely complicated processing is required. Therefore, there is a risk that the cost for manufacturing the flange member and the cost for manufacturing the electric power steering device will increase.

The present invention is to provide an inexpensive electric power steering device.

The steering device has a male thread groove, is housed inside a hollow housing, and is screwed via a male thread groove and a rolling element with a steering shaft that steers the left and right steering wheels by moving in the axial direction. A nut that is rotatably supported inside the housing, a drive source that generates a drive force, and a drive force that is fixed to the nut and connected to the drive source via a belt to generate the drive force. It includes a tubular pulley that transmits to the nut and a plate-shaped annular flange that is fixed to the outer peripheral surface at the axial end of the pulley and prevents the belt from falling off the pulley. A belt is wound around the central portion of the pulley in the axial direction, and a groove is formed along the circumferential direction on the outer peripheral surface at the end of the pulley in the axial direction. The flange is fixed by the inner peripheral portion entering the groove as the inner diameter of the inner peripheral portion is reduced.

According to this, the flange for preventing the belt from falling off can be formed into a plate-shaped annulus, and the shape can be extremely simple. Further, when fixing the flange to the pulley, it can be fixed only by undergoing a step of reducing the inner diameter of the inner peripheral portion of the flange with respect to the groove formed on the outer peripheral surface of the end portion in the axial direction of the pulley. can. Therefore, the cost of manufacturing the steering device can be reduced and the cost can be reduced.

It is an overall view which shows the structure of the steering device. It is sectional drawing which shows the structure of the steering device in detail. It is sectional drawing which shows the structure of the driven pulley and the flange. It is sectional drawing which shows the structure of the groove of the driven pulley in detail. It is a figure which shows the structure of a flange in detail. It is a figure for demonstrating the caulking position of a flange. It is sectional drawing for demonstrating the plastic deformation by the caulking process of a flange. It is a figure for demonstrating the caulking position and caulking processing of a flange which concerns on 1st alternative example. It is a figure for demonstrating the caulking position and caulking processing of the flange which concerns on 2nd alternative example. It is sectional drawing which shows the structure of the groove of the driven pulley which concerns on 3rd alternative example in detail. It is sectional drawing which shows the structure of the groove of the driven pulley which concerns on another example in detail. It is sectional drawing which shows the structure of the groove of the driven pulley which concerns on another example in detail. It is sectional drawing which shows the structure of the groove of the driven pulley which concerns on another example in detail. It is sectional drawing which shows the structure of the groove of the driven pulley which concerns on another example in detail. It is sectional drawing which shows the structure of the groove of the driven pulley which concerns on another example in detail. It is a figure which shows the structure of the flange which concerns on other another example. It is a figure for demonstrating the diameter expansion of a flange concerning another example.

(1. Configuration of steering device)
The configuration of the steering device 10 of this example will be described. As shown in FIG. 1, the steering device 10 includes steering shafts 11 connected to left and right front wheels FW1 and FW2 as left and right steering wheels to steer the left and right front wheels FW1 and FW2. Both ends of the steering shaft 11 are connected to the ball joint 12. The steering shaft 11 is connected to the left and right front wheels FW1 and FW2 via a link mechanism (for example, a tie rod, a knuckle, a hub carrier, etc.) connected to the ball joint 12.

Further, the steering shaft 11 is housed inside the hollow housing 13 so as to be displaceable in the axial direction. Then, the steering shaft 11 steers the left and right front wheels FW1 and FW2 (steering wheels) by moving relative to the housing 13 in the axial direction. The steering shaft 11 has a ball screw portion 11a on one end side in the axial direction.

As shown in FIG. 2, the ball screw portion 11a is screwed into the ball screw groove 11a1 as a male screw groove provided on one end side of the steering shaft 11 and the ball screw groove 11a1 and can rotate inside the housing 13. It is formed by a ball screw nut 14 which will be described later and is supported by the ball screw nut 14. The ball screw portion 11a has a rolling road 11a3 for rolling the ball 11a2 as a rolling element. On the turning road 11a3, a plurality of balls 11a2 roll while circulating.

Further, as shown in FIGS. 1 and 2, the steering device 10 includes an electric motor 15 as a drive source. The electric motor 15 generates a driving force by controlling the operation by the steering control device S. The steering control device S controls the operation of the electric motor 15 so as to generate a driving force according to the amount of rotation of the steering wheel H (steering shaft J) described later.

(2. Transmission mechanism of driving force from the electric motor 15 to the ball screw nut 14)
As shown in FIG. 1, the ball screw nut 14 is arranged coaxially with the ball screw groove 11a1 of the ball screw portion 11a provided on the steering shaft 11. As shown in FIG. 2, the ball screw nut 14 is adapted to transmit a driving force from the electric motor 15 via the drive pulley 16, the driven pulley 17, and the toothed belt 18. In addition to the above-mentioned elements, a gear or the like may be provided as the driving force transmission mechanism.

The drive pulley 16 is fixed to the rotating shaft of the electric motor 15. The driven pulley 17 is fixed (fitted) to the ball screw nut 14 by, for example, bolting. The toothed belt 18 is wound around the drive pulley 16 and the driven pulley 17. Further, flanges 19 for preventing the toothed belt 18 from falling off from the driven pulley 17 are fixed to the outer peripheral surfaces of both ends of the driven pulley 17 in the axial direction.

As shown in FIG. 2, tooth portions 16a are formed on the outer peripheral surface of the drive pulley 16. In this example, the tooth portion 16a is a tooth, but it can also be a flat tooth. Although not shown, flanges may be fixed to the outer peripheral surfaces of both ends of the drive pulley 16 in the axial direction.

The driven pulley 17 has a larger diameter than the drive pulley 16. A tooth portion 17a is formed on the outer peripheral surface of the driven pulley 17. In this example, the tooth portion 17a is a tooth, but it can also be a flat tooth. The driven pulley 17 is formed by sintering as described in detail later, and houses the ball screw nut 14 inside.

The toothed belt 18 is formed with a tooth portion 16a of the drive pulley 16 and a tooth portion 18a that meshes with the tooth portion 17a of the driven pulley 17 on the inner peripheral surface. As a result, when the driving force is transmitted from the electric motor 15 to the ball screw nut 14 via the drive pulley 16, the toothed belt 18, and the driven pulley 17, the ball screw nut 14 rotates relative to the ball screw groove 11a1 (turning road 11a3). do.

That is, when the ball screw nut 14 is rotated by the transmitted driving force, the ball 11a2 arranged between the ball screw groove 11a1 of the ball screw portion 11a and the ball screw nut 14 rolls along the rolling path 11a3. Then, the driving force of the electric motor 15 is converted into a force for moving the steering shaft 11 in the axial direction (axial force), in other words, a steering force for steering the left and right front wheels FW1 and FW2. In this case, the ball screw nut 14 reduces the rotational speed of the driving force transmitted from the electric motor 15, and converts the motion into a linear motion, while the ball screw groove 11a1 of the ball screw portion 11a, that is, the steering shaft 11 Communicate to. As a result, the ball screw nut 14 exerts torque on the steering shaft 11 at the ball screw portion 11a.

Further, on the other end side of the steering shaft 11, a rack screwed with a pinion G that rotates integrally with the steering shaft J as the steering shaft J connected to the steering wheel H rotated by the driver rotates. R is formed. That is, the steering device 10 includes a so-called rack and pinion mechanism, and transmits the rotation operation of the steering wheel H by the driver to the left and right front wheels FW1 and FW2 (steering wheels) via the steering shaft 11. It has become.

(3. Driven pulley 17)
The driven pulley 17 is a sintered body formed by sintering a powder material, and has a bottomed cylindrical shape. In addition, sintering is a process in which a powder material is filled in a mold and heated to a temperature equal to or lower than the melting point of the powder material to bond the powder materials to each other to form a part having a desired shape.

Here, as the powder material, various metal powder materials and resin powder materials can be used. As the metal powder material, iron-based powders such as forging material (curing material), rolled material, casting material, and raw material, aluminum material powder, zinc die-cast material powder, and the like can be used. can. Further, as the resin powder material, a thermoplastic resin, for example, a polyphenylene sulfide resin powder, a polyamide powder, a phenol-formaldehyde resin powder which is a thermosetting resin, or the like can be used. When a resin material is used, a reaction-molded product (phenol resin, etc.), which is a molded product obtained by reacting a liquid resin material in a mold to solidify it, or a heat-melted resin material is injection-molded (solid-molded). It may be an injection-molded product which is a molded product.

Since the driven pulley 17 formed by sintering is formed by solidifying the powder material without completely melting it, it has many pores and a low density. Therefore, for example, the driven pulley 17 formed by sintering is lighter than the driven pulley manufactured by completely melting and solidifying the powder material by casting, pressing, or the like.

However, due to the low density of the driven pulley 17, the driven pulley 17 is particularly vulnerable to deformation accompanied by bending, for example, partial bending deformation due to caulking. That is, although the extension characteristics of the driven pulley 17 are necessary and sufficient for transmitting the driving force via the toothed belt 18, forging or rolling material is used for local bending such as caulking. Is inferior to the extension characteristics of the driven pulley machined. As a result, it becomes difficult to secure the caulking strength when the flange 19 is fixed by caulking. The fixing of the flange 19 will be described in detail later.

(3-1. Configuration of driven pulley 17)
As shown in FIG. 3, the driven pulley 17 has a large diameter portion 17b as a central portion in which a tooth portion 17a that meshes with the tooth portion 18a of the toothed belt 18 is formed, and a large diameter portion 17b in the axial direction. It is provided with a small diameter portion 17c provided at an adjacent end portion. Further, the driven pulley 17 is adjacent to the step portion 17d standing in the radial direction at the boundary between the large diameter portion 17b and the small diameter portion 17c in the axial direction and in the circumferential direction of the small diameter portion 17c. A groove 17e formed along the groove 17e is provided. Further, in the driven pulley 17, a flange 19 having a plate-shaped annulus is assembled to the groove 17e.

(3-1-1. Shape of groove 17e)
As shown in FIG. 4, the groove 17e is connected to the large-diameter gutter side surface 17e1 as the first groove side surface connected to the step portion 17d and the large-diameter gutter side surface 17e1 and is connected to the large-diameter gutter side surface 17e1 and formed along the axis. 17e2 and a small-diameter gutter side surface 17e3 as a second groove side surface connected to the groove bottom surface 17e2 and erected along the radial direction are provided. Here, in this example, the length (width) of the groove bottom surface 17e2 in the axial direction is formed shorter (narrower) than the length (width) of the groove 17e on the open side in the axial direction. As shown in FIG. 4, the large-diameter gutter side surface 17e1 connects the connection position P1 with the step portion 17d having the same diameter as the small-diameter portion 17c and the connection position P2 with the groove bottom surface 17e2.

That is, the large-diameter gutter side surface 17e1 of this example is formed in a tapered shape in which the outer diameter decreases from the side of the step portion 17d toward the groove bottom surface 17e2. Therefore, the groove 17e of this example is formed so that the cross-sectional shape on the plane including the axis is substantially triangular. As a result, the cross-sectional area of the groove 17e, in other words, the volume in the circumferential direction, can be made smaller than, for example, when the cross-sectional shape is rectangular.

(4. Composition of flange 19)
The flange 19 is manufactured in a flat plate annular shape using low carbon steel (metal material), a thermoplastic resin (resin material), or the like, which is softer than the driven pulley 17 which is a sintered body. The flange 19 is manufactured by, for example, press working or injection molding. As shown in FIG. 5, the inner peripheral portion 19a of the flange 19 has an inner diameter larger than the outer diameter of the small diameter portion 17c of the driven pulley 17. Further, the outer peripheral portion 19b of the flange 19 has an outer diameter larger than the outer diameter of the large diameter portion 17b of the driven pulley 17, and more specifically, the outer diameter of the toothed belt 18 assembled to the large diameter portion 17b.

Further, the plate thickness of the flange 19 is set to be slightly smaller than the width of the groove 17e of the driven pulley 17 on the open end side. Then, the flange 19 is fixed to the groove 17e as described later in order to prevent the toothed belt 18 from falling off from the large diameter portion 17b of the driven pulley 17 with the transmission of the driving force.

(5. Fixing the flange 19)
As described above, since the driven pulley 17 is a sintered body formed by sintering, it is difficult to perform caulking to bend and deform a part of the small diameter portion 17c in order to fix the flange 19, for example. Therefore, in this example, a plurality of locations are pressed in the circumferential direction of the flange 19 by a caulking punch toward the driven pulley 17 and the axial direction of the flange 19, and a part of the flange 19 is inside in the radial direction with the pressing. Plastically deform toward the direction.

As a result, the plastically deformed portion of the flange 19 is made to enter the inside of the groove 17e, that is, a part of the flange 19 is filled (filled) inside the groove 17e, so that the flange 19 is made with respect to the driven pulley 17. Fix it. Here, in the following description, for fixing, the flange 19 does not move in the axial direction and the radial direction with respect to the driven pulley 17, and the flange 19 moves slightly in the axial direction and the radial direction with respect to the driven pulley 17. This includes a state in which the driven pulley 17 does not fall off.

Specifically, the flange 19 is fixed to the driven pulley 17 by a manufacturing method (manufacturing method of a steering device) including the following manufacturing steps. First, in the molding process, the sintered body is molded by sintering the powder material. In the case of a resin material, the resin material is filled in a mold and solidified in the molding process. The inner peripheral portion 19a of the flange 19 is set to be slightly larger than the outer diameter of the small diameter portion 17c of the driven pulley 17 and smaller than the outer diameter of the large diameter portion 17b of the driven pulley 17. Therefore, in the temporary assembly step of temporarily assembling the flange 19 to the driven pulley 17, as shown in FIG. 4, first, the small diameter portion 17c of the driven pulley 17 is inserted through the inner peripheral portion 19a of the flange 19, and the flange 19 is inserted. The driven pulley 17 is brought into contact with the step portion 17d.

Subsequently, in the fixing step of fixing the flange 19 to the driven pulley 17, a caulking punch is used to press the inner peripheral side of the flange 19 in contact with the step portion 17d along the axial direction. In this case, in this example, the caulking positions are set at a plurality of locations (12 locations) along the circumferential direction of the flange 19 and evenly along the circumferential direction, as shown by black circles in FIG. Therefore, in this example, for example, using a caulking punch in which three caulking claws are arranged at intervals of 120 degrees in the circumferential direction, the caulking punch is rotated by 30 degrees in the caulking process to press the flange 19 in the axial direction.

As a result, the inner peripheral side of the flange 19 is pressed axially with the stepped portion 17d of the driven pulley 17 by the caulking punch, and as shown in FIG. 7, a part of the inner peripheral portion 19a is inward in the radial direction. Plastically deforms toward. Then, the material on the inner peripheral side enters toward the groove 17e with the plastic deformation, so that the groove 17e is filled (filled) with the entered material. Here, the inner peripheral portion 19a of the flange 19 that has entered the groove 17e is in contact with at least three points of the large-diameter gutter side surface 17e1, the groove bottom surface 17e2, and the small-diameter gutter side surface 17e3 of the groove 17e, as shown by black circles in FIG. It is filled so that it does.

When the groove 17e is filled with a part of the material of the inner peripheral portion 19a of the flange 19, the flange 19 is fixed to the groove 17e. As a result, the flange 19 is fixed to the driven pulley 17, more specifically, the small diameter portion 17c of the driven pulley 17. Here, the flange 19 fixed to the groove 17e is arranged in a state of being in contact with (or in a state of being close to) the step portion 17d of the driven pulley 17. As a result, when the toothed belt 18 is attached to the large diameter portion 17b and rotates to transmit the driving force, the toothed belt 18 is oriented in the axial direction of the driven pulley 17, that is, in the axial direction of the ball screw nut 14. Even if the flange 19 moves relative to the other, the flange 19 restricts the relative movement of the toothed belt 18 in the axial direction. Therefore, the flange 19 can prevent the toothed belt 18 from falling off from the large diameter portion 17b of the driven pulley 17.

As can be understood from the above description, the flange 19 that prevents the toothed belt 18 from falling off can be formed into a plate-shaped annulus, and can have an extremely simple shape. When fixing the flange 19 to the driven pulley 17, the inner diameter of the inner peripheral portion 19a of the flange 19 is reduced with respect to the groove 17e formed on the outer peripheral surface of the small diameter portion 17c which is the end of the driven pulley 17. It can be fixed only by going through the process. Here, the step of reducing the inner diameter of the inner peripheral portion 19a can be a simple step of pressing the flange 19 along the axial direction to plastically deform it. Therefore, the cost of manufacturing the steering device 10 can be reduced and the cost can be reduced. Further, the volume of the groove 17e is reduced by forming the large diameter side groove side surface 17e1 into a tapered shape. Therefore, even if the pushing depth of the caulking punch is reduced, the material of the flange 19 enters the inside of the groove 17e and is filled (filled), and as a result, the rattling of the flange 19 can be removed.

(6. First alternative example)
In this example described above, the flange 19 is provided with caulking positions evenly at a plurality of locations (12 locations) along the circumferential direction of the flange 19, that is, the caulking positions are provided intermittently in the circumferential direction. bottom. Instead of this, as shown by the thick solid line in FIG. 8, the caulking position can be continuously set along the circumferential direction of the flange 19. In this case, for example, by using a roll caulking method or the like, caulking can be performed continuously along the circumferential direction of the flange 19.

In this way, when the flange 19 is continuously crimped in the circumferential direction, the inner peripheral side of the flange 19 can be plastically deformed inward in the radial direction substantially uniformly. Therefore, in the case of the first alternative example, since the inner peripheral portion 19a of the flange 19 uniformly enters the inside of the groove 17e, the flange 19 can be more firmly fixed to the driven pulley 17.

(7. Second alternative example)
In this example described above, the caulking positions are set at a plurality of locations (for example, 12 locations) evenly (for example, at intervals of 30 degrees) along the circumferential direction of the flange 19. However, the caulking position is not limited to being uniform in the circumferential direction, and as shown in FIG. 9, it can be set at unequal intervals in the circumferential direction.

In this case, for example, using a caulking punch in which the caulking claws D are evenly arranged in the circumferential direction as in this example described above, the caulking positions are provided at unequal intervals in the circumferential direction by arbitrarily changing the rotation angle. And the number of caulking positions can be increased or decreased as needed. This also gives the same effect as this example described above.

(8. Third alternative example)
In this example described above, as shown in FIG. 4, the diameter of the connection position P1 between the step portion 17d and the large diameter side groove side surface 17e1 of the groove 17e is set to be the same as the outer diameter of the small diameter portion 17c. Instead, as shown in FIG. 10, the diameter of the connection position P3 between the step portion 17d and the large diameter side groove side surface 17e1 of the groove 17e is larger than the outer diameter of the small diameter portion 17c and the outer diameter of the large diameter portion 17b. It is also possible to provide the diameter smaller than that.

In this case, in FIG. 10, in the inner peripheral portion 19a of the flange 19, a slope 19a1 parallel to the large-diameter gutter side surface 17e1 is provided on the surface of the flange 19 facing the step portion 17d in a state of being attached to the driven pulley 17. Is good. In this way, by setting the diameter of the connection position P3 to be larger than the outer diameter of the small diameter portion 17c and providing the slope 19a1 on the inner peripheral portion 19a of the flange 19, positioning (centering) when caulking the flange 19 is performed. ) Can be easily matched.

(9. Others)
In this example and each of the above-mentioned examples, the groove 17e is formed so that the cross-sectional shape is substantially triangular. The cross-sectional shape of the groove 17e is not limited to this, and for example, as shown in FIG. 11, it is possible to form the groove 17e so that the cross-sectional shape is rectangular. Further, regarding the cross-sectional shape of the groove 17e, for example, as shown in FIG. 12, the groove bottom surface 17e2 can be formed so as to be curved. Alternatively, the cross-sectional shape of the groove 17e can be formed to have an arc shape as shown in FIG. As described above, even when the shape of the groove 17e is changed, the same effect as that of this example described above can be obtained.

Further, in this example and each of the above-mentioned examples, the groove 17e is formed so that the large-diameter side groove side surface 17e1 of the groove 17e is connected to the step portion 17d. Instead, for example, as shown in FIGS. 14 and 15, the large-diameter gutter side surface 17e1 can be provided so as to be axially separated from the stepped portion 17d of the driven pulley 17. Specifically, as shown in FIG. 14, it is also possible to set the connection position P4 to be connected to the outer peripheral surface of the small diameter portion 17c and to provide the tapered large diameter gutter side surface 17e1. Further, as shown in FIG. 15, it is also possible to set the connection position P5 to be connected to the outer peripheral surface of the small diameter portion 17c and to provide the large diameter side groove side surface 17e1 standing upright in the radial direction. In this way, even when the groove 17e is provided so as to be separated from the step portion 17d in the axial direction, the flange 19 is plastically deformed so that a part of the inner peripheral portion 19a is inserted into the groove 17e to fill the groove 17e. By (filling), the same effect as that of this example described above can be obtained.

Further, the plate thickness of the flange 19 may be set larger than the width of the groove 17e of the driven pulley 17 on the open end side. Even with such a configuration, the flange 19 can be fixed by caulking a part of the material of the flange 19 into the inside of the groove 17e and filling (filling) the flange 19.

Further, in this example and each of the other examples described above, a part of the inner peripheral portion 19a is formed by pressing the inner peripheral side of the flange 19 arranged on the small diameter portion 17c of the driven pulley 17 in the axial direction to plastically deform the flange 19. The flange 19 is fixed by entering the inside of the groove 17e. That is, in this example and each of the above-mentioned examples, the inner peripheral side of the flange 19 is plastically deformed to reduce the diameter so that a part of the inner peripheral portion 19a enters (fills) the groove 17e. bottom.

Instead, for example, when the flange 19 is made of metal, it is possible to insert the inner peripheral portion 19a of the flange 19 into the groove 17e by using shrink fitting. Alternatively, when the flange 19 is a thermoplastic resin, the inner peripheral side of the flange 19 can be softened by heating to allow the inner peripheral portion 19a of the flange 19 to enter the groove 17e. In these cases, as shown in FIG. 16, in the initial state before fixing the flange 19 to the driven pulley 17, the inner diameter of the inner peripheral portion 19a is slightly smaller than the outer diameter of the small diameter portion 17c of the driven pulley 17. To manufacture.

Then, as shown in FIG. 17, when the metal flange 19 is shrink-fitted, the inner peripheral portion 19a is expanded in the radial direction from the outer diameter of the small diameter portion 17c by heating the flange 19. Then, the flange 19 is attached, and then the flange 19 is cooled to reduce the diameter. As a result, a part of the inner peripheral portion 19a of the metal flange 19 can be made to enter the groove 17e and fixed.

When the flange 19 made of thermoplastic resin is softened and fixed, the flange 19 is softened by heating and attached to the small diameter portion 17c, and then, if necessary, the inner peripheral side of the flange 19. Is further heated to melt a part of the inner peripheral portion 19a and enter the groove 17e. After that, the flange 19 of the thermoplastic resin can be fixed by cooling and solidifying the flange 19. Therefore, even in these cases, the same effects as those of this example and each example described above can be obtained.

10 ... Steering device, 11 ... Steering shaft, 11a ... Ball screw portion, 11a1 ... Ball screw groove (male screw groove), 11a2 ... Ball (rolling element), 11a3 ... Rolling road, 12 ... Ball joint, 13 ... Housing, 14 ... ball screw nut (nut), 15 ... electric motor (drive source), 16 ... drive pulley, 16a ... tooth part, 17 ... driven pulley (pulley), 17a ... tooth part, 17b ... large diameter part (center part), 17c ... Small diameter portion (end), 17d ... Stepped portion, 17e ... Groove, 17e1 ... Large diameter side groove side surface (first groove side surface), 17e2 ... Groove bottom surface, 17e3 ... Small diameter side groove side surface (second groove side surface), 18 ... Toothed belt (belt), 18a ... tooth part, 19 ... flange, 19a ... inner peripheral part, 19a1 ... slope, 19b ... outer peripheral part, D ... caulking claw, FW1, FW2 ... left and right front wheels, H ... steering wheel, J ... Steering shaft, G ... Pinion, R ... Rack, S ... Steering control device, P1 ... Connection position, P2 ... Connection position, P3 ... Connection position, P4 ... Connection position, P5 ... Connection position

Claims (11)

A steering shaft that has a male thread groove and is housed inside a hollow housing to steer the left and right steering wheels by moving in the axial direction.
A nut that is screwed into the male thread groove via a rolling element and is rotatably supported inside the housing.
The drive source that generates the driving force and
A tubular pulley that is fixed to the nut and is connected to the drive source via a belt to transmit the drive force generated by the drive source to the nut.
A flange of a plate-shaped annulus fixed to the outer peripheral surface at the axial end of the pulley to prevent the belt from falling off the pulley.
With
The belt is wound around the central portion of the pulley in the axial direction.
At the end of the pulley in the axial direction, a groove is formed along the circumferential direction on the outer peripheral surface.
The flange is a steering device fixed by the inner peripheral portion entering the groove as the inner diameter of the inner peripheral portion is reduced. The steering device according to claim 1, wherein the flange has a reduced inner diameter of the inner peripheral portion due to plastic deformation on the inner peripheral side including the inner peripheral portion. The steering device according to claim 2, wherein the plastic deformation is caused by caulking that presses the inner peripheral side along the axial direction of the flange. The steering device according to claim 3, wherein the caulking position for caulking is provided intermittently and at equal intervals along the circumferential direction on the inner peripheral side of the flange. The steering device according to claim 3, wherein the caulking position for caulking is intermittently and unequally spaced along the circumferential direction on the inner peripheral side of the flange. The steering device according to claim 3, wherein the caulking position for caulking is continuously provided along the circumferential direction on the inner peripheral side of the flange. The groove has a first groove side surface on the central portion side, a second groove side surface facing the first groove side surface, and a groove bottom surface connecting the first groove side surface and the second groove side surface. ,
The steering device according to any one of claims 1 to 6, wherein the side surface of the first groove is formed in a tapered shape toward the bottom surface of the groove. The pulley has a smaller outer diameter at the end than the outer diameter at the center.
One end of the first groove side surface is connected to a step portion erected in the radial direction at the boundary between the central portion and the end portion, and the outer diameter at the connection position between the step portion and the one end is the end portion. The steering device according to claim 7, wherein the steering device has an outer diameter or more and is smaller than the outer diameter of the central portion. The pulley is molded by filling a mold with a sintered body sintered by heating the powder material filled in the mold at a temperature equal to or lower than the melting point of the powder material, or by filling the mold with a liquid resin material and solidifying the molding. The steering device according to any one of claims 1 to 8, which is a body. The steering device according to claim 9, wherein the powder material is a metal powder material or a resin powder material. The steering device according to any one of claims 1-10, wherein the flange is formed in the plate-shaped annulus using a metal material or a resin material.

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