JP6314348B2 - Method for manufacturing power steering device - Google Patents

Description

  The present invention relates to a power steering apparatus.

  As this type of technique, a technique described in Patent Document 1 below is disclosed. Patent Document 1 discloses an electric power steering device that transmits driving force of an electric motor to a ball screw mechanism to apply assist force to a rack shaft.

JP 2013-06517 A

In the technique described in Patent Document 1, a ball screw groove is cut to the end of the rack shaft (steering shaft), and the rack shaft is cantilevered by a double row angular ball bearing via a ball screw mechanism. . For this reason, the rack shaft tends to be inclined and good shaft support cannot be performed.
The present invention focuses on the above-described problems, and an object of the present invention is to provide a method for manufacturing a power steering device that enables good support of the steered shaft.

In order to achieve the above object, in a method for manufacturing a power steering apparatus according to an embodiment of the present invention, the power steering apparatus is in a housing, and a sliding bearing that pivotally supports the steered shaft so as to be movable in the axial direction in the housing. When located at one axial end side than the turning shaft side ball screw groove of the steering shaft has a sliding surface which is axially supported by the sliding bearing, the method includes turning the base material of the steered shaft The process of grinding the surface of the area where the shaft side ball screw groove is formed and the area where the sliding surface is formed at once, and after the grinding process, the steered shaft side ball screw groove is cut into a spiral groove shape And a process .

Therefore, it is possible to provide a manufacturing method of a power steering apparatus which allows a good journalled of the steered shaft. By grinding the surface of the region where the steered shaft side ball screw groove is formed and the region where the sliding surface is formed in the base material of the steered shaft at once, the tooth tip surface of the steered shaft side ball screw groove and The sliding surface can be formed at a time.

1 is a front view of a power steering device according to Embodiment 1. FIG. 1 is a cross-sectional view of a power steering device of Embodiment 1. FIG. FIG. 3 is a perspective view showing a state in which a nut is inserted into the steered shaft according to the first embodiment. FIG. 3 is a perspective view showing a state in which a nut is inserted into the steered shaft according to the first embodiment.

[Example 1]
A power steering device 1 according to a first embodiment will be described. The power steering device 1 according to the first embodiment applies an assist force to the driver's steering force by transmitting the driving force of the electric motor 40 to the steered shaft 10 via the ball screw mechanism 26.
[Configuration of power steering system]
FIG. 1 is a front view of the power steering apparatus 1. FIG. FIG. 2 is a sectional view in the axial direction of the power steering apparatus 1.
The power steering apparatus 1 includes a steering mechanism 2 that transmits rotation of a steering wheel steered by a driver to a steered shaft 10 that steers steered wheels, and an assist mechanism 3 that applies assist force to the steered shaft 10. Have.

Each component of the power steering device 1 is accommodated in a housing 30 including a first housing 31, a second housing 32, and a motor housing 33.
The steered shaft 10 is accommodated in a first housing 31 and a second housing 32, and is pivotally supported on the second housing 32 by an end bush 34.
The steering mechanism 2 includes a steering input shaft 80 connected to the steering wheel, and a pinion 81 that rotates integrally with the steering input shaft 80. The pinion 81 meshes with a rack formed on the outer periphery of the steered shaft 10.
The assist mechanism 3 includes an electric motor 40 and a ball screw mechanism 26 that transmits the output of the electric motor 40 to the steered shaft 10.
The output of the electric motor 40 is controlled by a motor controller in accordance with the steering torque and the steering amount input to the steering wheel by the driver. A cylindrical input pulley 35 is provided on the output rotation shaft 40a of the electric motor 40 so as to rotate integrally.
The ball screw mechanism 26 includes a nut 20 and an output pulley 27. The appearance of the output pulley 27 is a cylindrical member, and is fixed to the nut 20 so as to be integrally rotatable. A cylindrical input pulley 35 is fixed to the drive shaft 40a of the electric motor 40 so as to rotate integrally.

A belt 28 is wound between the input pulley 35 and the output pulley 27. The driving force of the electric motor 40 is transmitted to the nut 20 via the input pulley 35, the belt 28, and the output pulley 27. The outer diameter of the input pulley 35 is smaller than the outer diameter of the output pulley 27.
The nut 20 is formed in an annular shape so as to surround the steered shaft 10, and is provided so as to be rotatable with respect to the steered shaft 10. A groove is spirally formed on the inner periphery of the nut 20, and this groove forms a nut-side ball screw groove 21. The steered shaft 10 is formed by connecting two members, a rack forming portion 10a and a thread groove forming portion 10b. The aforementioned rack is formed on the outer periphery of the rack forming portion 10a. A spiral groove is formed on the outer periphery of the thread groove forming portion 10b, and this groove constitutes the steered shaft side ball screw groove 11.
In a state where the nut 20 is inserted into the steered shaft 10, a ball circulation groove 12 is formed by the nut-side ball screw groove 21 and the steered shaft-side ball screw groove 11. The ball circulation groove 12 is filled with a plurality of balls 22 made of metal. When the nut 20 rotates, the ball 22 moves in the ball circulation groove 12 so that the steered shaft 10 moves in the longitudinal direction with respect to the nut 20.
The surface of the steered shaft 10 on the one end side in the axial direction from the steered shaft side ball screw groove 11 is smoothly surfaced to constitute a sliding surface 13. The aforementioned end bush 34 pivotally supports the sliding surface 13. The sliding surface 13 is provided in a range that can slide with the end bush 34 in the entire movable range in the axial direction of the steered shaft 10.

[Configuration of nut]
The nut 20 is rotatably supported on the first housing 31 by a bearing 24. The bearing 24 has an outer race 24a and an inner race 24b. A ball 24c is provided between the outer race 24a and the inner race 24b. The inner race 24b is formed integrally with the nut 20 on one axial end side (steering mechanism 2 side) of the nut 20.
FIG. 3 is a perspective view of the steered shaft 10 with the nut 20 inserted. FIG. 4 is an exploded view of the ball tube 23 from the view of FIG.
Connection passages 20b and 20c connected to the ball circulation groove 12 are formed on the outer periphery of the main body 20a of the nut 20. The ball 22 is filled into the ball circulation groove 12 from the connection passages 20b and 20c. A ball tube 23 connecting the connection passages 20b and 20c is inserted into the connection passages 20b and 20c. A tube clip 25 is covered near the center of the ball tube 23. Bolt holes 25 a through which the bolts 29 pass are formed at both ends of the tube clip 25. Bolt holes 20c into which bolts 29 are inserted are formed in the main body portion 20a of the nut 20.
After the ball 22 is filled in the ball circulation groove 12, the ball tube 23 filled with the ball 22 is inserted into the connection passages 20b and 20c. The ball tube 23 is held on the nut 20 by fixing the tube clip 25 to the nut 20 with a bolt 29 while the ball clip 23 is covered with the tube clip 25.

[Action]
The steered shaft 10 is desired to have an outer diameter that is as uniform as possible over the entire axial direction in order to avoid stress concentration. Under such conditions, when the steered shaft ball screw groove 11 is formed by rolling, the steered shaft side ball screw groove 11 extends over the entire axial direction of the thread groove forming portion 10b of the steered shaft 10. Will be formed.
When the steered shaft side ball screw groove 11 is formed up to the end of the thread groove forming portion 10b, the bearing that supports the steered shaft 10 with respect to the housing 30 contacts the steered shaft side ball screw groove 11. It will be. Therefore, when the steered shaft 10 moves in the axial direction, the bearing is easily damaged by the step of the steered shaft side ball screw groove 11. In addition, vibration and noise are generated by the step. Further, since only the mountain portion of the steered shaft side ball screw groove 11 comes into contact with the bearing, the steered shaft 10 itself is easily damaged.
In order to suppress the occurrence of these problems, the clearance between the steered shaft 10 and the bearing can be increased, and the load can be received by the bearing only when a large force acts on the steered shaft. However, in this solution, the steered shaft 10 cannot be supported firmly, and the steered shaft 10 is rattled.

Therefore, in Example 1, the steered shaft side ball screw groove 11 is formed by cutting. Unlike the rolling process, the cutting process can partially form the ball screw groove even if the outer diameter of the steered shaft 10 is uniform in the entire axial direction. As a result, it is possible to form a smooth surface-treated slide surface 13 in which no screw groove is cut, at one end side of the steered shaft side ball screw groove 11 of the steered shaft 10. The end bush 34 pivotally supports the steered shaft 10 on the sliding surface 13.
As a result, the portion where the end bushing 34, which is a sliding bearing, contacts the steered shaft 10 can be the sliding surface 13 having a smooth surface. Therefore, vibration and noise can be suppressed, and damage to the end bush 34 and the steered shaft 10 can be suppressed. Further, since the clearance between the steered shaft 10 and the end bush 34 can be reduced, the rattling of the steered shaft 10 can be suppressed.

Further, in Example 1, the sliding surface 13 is provided in a range in which the sliding surface 13 can slide with the end bush 34 in the entire movable range in the axial direction of the steered shaft 10.
Thereby, since the end bush 34 does not contact the steered shaft side ball screw groove 11, damage to the end bush can be suppressed.
In Example 1, the outer diameter of the base material of the steered shaft 10 in the region where the steered shaft side ball screw groove 11 is formed and the outer surface of the base material of the steered shaft 10 in the region where the sliding surface 13 is formed. The diameter was the same.
If the portion where the steered shaft side ball screw groove 11 is formed has a large diameter and the portion where the slide surface 13 is formed has a small diameter, the slip surface 13 is provided at the end of the steered shaft 10 by rolling. It is possible to form the steered shaft side ball screw groove 11. However, the diameter of the region where the steered shaft side ball screw groove 11 of the steered shaft 10 is formed is different from the diameter of the region where the sliding surface 13 is formed. For this reason, a portion where stress concentrates on the steered shaft 10 occurs, and the steered shaft 10 may be damaged. In addition, since the strength of the portion where the steered shaft side ball screw groove 11 is formed and the strength of the portion where the sliding surface 13 is formed are different, there is a possibility that bending occurring when quenching is increased. Further, although the tie rod is connected to the end portion of the sliding surface 13, the outer diameter of the connecting portion becomes small, and there is a possibility that the strength of the connecting portion cannot be ensured. In addition, workability during connection work may be deteriorated.

On the other hand, in Example 1, the diameter of the steered shaft 10 can be made substantially uniform over the entire axial direction. For this reason, stress concentration can be suppressed and damage to the steered shaft 10 can be suppressed. In addition, bending during quenching can be suppressed. Moreover, the outer diameter of the part which connects a tie rod is securable. For this reason, the intensity | strength of a connection part with a tie rod is securable. Furthermore, workability at the time of connection work can be improved.
In Example 1, the region where the steered shaft side ball screw groove 11 is formed is heat-treated by induction hardening.
In the induction hardening, heat treatment can be performed by inserting the steered shaft 10 into a cylindrical apparatus. Thereby, even in the case of the elongated steered shaft 10, the heat treatment can be partially performed only on the formation region of the steered shaft side ball screw groove 11, and the heat treatment work efficiency can be improved.
Further, in Example 1, before the turning shaft side ball screw groove 11 is cut on the turning shaft 10, the surface of the formation region of the ball screw groove 11 and the formation region of the sliding surface 13 is ground. .
Thereby, the tooth tip surface of the steered shaft side ball screw groove 11 and the surface of the sliding surface 13 can be ground at a time, and the outer diameter dimension of the entire axial direction of the steered shaft 10 can be adjusted. .

〔effect〕
(1) When the steered shaft 10 that steers the steered wheels with the rotation of the steering wheel and the longitudinal direction of the steered shaft 10 is the first axial direction, within a predetermined range of the first axial direction of the steered shaft 10 A steered shaft side ball screw groove 11 provided on the outer peripheral side of the steered shaft 10 and formed into a spiral groove shape by cutting, and a main body portion 20a formed in an annular shape so as to surround the steered shaft 10 A nut 20 that is rotatably provided to the steered shaft 10, and is provided on the inner peripheral side of the nut 20, has a spiral groove shape, and has a spiral shape together with the ball screw groove 11 on the steered shaft side. When the rotation axis of the nut-side ball screw groove 21 and the nut 20 constituting the ball circulation groove 12 is the second axial direction and the direction around the rotation axis of the nut 20 is the circumferential direction, the nut 20 in the second axial direction Open to the outside of the nut in the circumferential direction predetermined range of the end surface or the outer peripheral surface of the nut 20 A connection passage 20b, 20c (ball insertion passage) formed so as to communicate with the ball screw groove 21 and a ball tube 23 (sealing) provided in the nut 20 and sealing the opening to the outside of the connection passage 20b, 20c Member), a plurality of balls 22 which are inserted into the nut 20 through the connection passages 20b and 20c, and are movably provided in the ball circulation groove 12, and the steered shaft 10 and the nut 20 are accommodated. A housing 30, an end bush 34 (slide bearing) that is provided in the housing 30 and supports the steered shaft 10 so as to be movable in the first axial direction in the housing 30, and a steered shaft-side ball screw of the steered shaft 10 The sliding surface 13 provided on one end side in the first axial direction than the groove 11 and pivotally supported by the end bush 34 and the nut 20 are rotationally driven, and the rotation of the nut 20 is converted into the axial motion of the steered shaft 10. An electric motor 40 for applying a steering force to the steered shaft 10 by It was made to have.
Therefore, vibration and noise can be suppressed, and damage to the end bush 34 and the steered shaft 10 can be suppressed. Further, rattling of the steered shaft 10 can be suppressed.

(2) The sliding surface 13 is formed on the end bush 34 in the entire area where the steered shaft 10 slides.
Therefore, damage to the end bush can be suppressed.
(3) The outer diameter of the base material of the steered shaft 10 in the region where the steered shaft side ball screw groove 11 is formed and the outer diameter of the base material of the steered shaft 10 in the region where the sliding surface 13 is formed are the same diameter. It was.
Therefore, stress concentration can be suppressed and damage to the steered shaft 10 can be suppressed. Further, bending during quenching can be suppressed. Moreover, the strength of the connecting portion with the tie rod can be ensured. Furthermore, workability at the time of connection work can be improved.
(4) The formation region of the turning shaft side ball screw groove 11 of the turning shaft 10 was heat-treated by induction hardening.
Therefore, heat treatment can be partially performed only on the formation region of the steered shaft side ball screw groove 11, and heat treatment efficiency can be improved.
(5) Before cutting the steered shaft side ball screw groove 11, the surface of the steered shaft side ball screw groove 11 forming region and the surface of the sliding surface 13 forming region is ground.
Therefore, the tooth tip surface of the steered shaft side ball screw groove 11 and the surface of the sliding surface 13 can be ground at once, and the outer diameter dimension of the entire steered shaft 10 in the axial direction can be adjusted.

[Other embodiments]
As described above, the present invention has been described based on the first embodiment. However, the specific configuration of each invention is not limited to the first embodiment, and even if there is a design change or the like without departing from the gist of the present invention. Are included in the present invention.
In the first embodiment, the balls 22 are filled into the ball circulation groove 12 from the connection passages 20b and 20c of the nut 20. A hole penetrating the ball circulation groove 12 from the axial side surface of the nut 20 may be formed, and the ball 22 may be filled from this hole. In this case, it is necessary to seal the hole filling the ball 22.
In the first embodiment, it is described that the steered shaft side ball screw groove 11 is formed by cutting, but the cutting includes grinding.

[Technical thought other than claims]
Further, technical ideas other than the claims that can be grasped from the above-described embodiment will be described below.
(A) In the power steering device according to claim 1,
The power steering device according to claim 1, wherein the sliding surface is formed in an entire area where the turning shaft slides on the sliding bearing.
(B) In the power steering device according to claim 1,
The power steering apparatus, wherein the turning shaft side ball screw groove forming region of the turning shaft is heat-treated by induction hardening.

10 Steering shaft
11 Steering shaft side ball screw groove
12 Ball circulation groove
13 Sliding surface
20 nuts
20a body
20b, 20c Connection passage (ball insertion passage)
21 Nut side ball screw groove
22 balls
23 Ball tube (sealing material)
30 Housing
34 End bush (slide bearing)
40 Electric motor

Claims (3)

A method of manufacturing a power steering device,
The power steering device is
A steered shaft that steers steered wheels as the steering wheel rotates,
When the longitudinal direction of the steering shaft and the first axial direction, is in the outer periphery of the steering shaft in the first axial direction in a predetermined range of the steering shaft, the steering shaft having a spiral groove shape Side ball screw groove,
A body portion of an annular surrounding the steering shaft, and the nut is rotatable relative to said steering shaft,
A nut-side ball screw groove that is on the inner peripheral side of the nut, has a spiral groove shape, and forms a spiral ball circulation groove together with the steered shaft-side ball screw groove;
A plurality of balls capable of moving the ball circulation groove,
A housing for housing the steered shaft and the nut;
A slide bearing which is in the housing and pivotally supports the steered shaft so as to be movable in the first axial direction in the housing;
A sliding surface which is on one end side in the first axial direction of the steered shaft side ball screw groove of the steered shaft and is pivotally supported by the slide bearing;
An electric motor that rotates the nut and applies a steering force to the steered shaft by converting the rotation of the nut into an axial motion of the steered shaft;
I have a,
The manufacturing method includes:
Grinding the surface of the region where the steered shaft side ball screw groove is formed and the region where the sliding surface is formed in the base material of the steered shaft at a time;
After the grinding process, cutting the steered shaft side ball screw groove into the spiral groove shape;
Having
A method for manufacturing a power steering apparatus. In the method of manufacturing a power steering device according to claim 1,
The outer diameter of the base material of the steered shaft in the region where the steered shaft side ball screw groove is formed and the outer diameter of the base material of the steered shaft in the region where the sliding surface is formed are the same diameter , A method for manufacturing a power steering apparatus. In the method of manufacturing a power steering device according to claim 1 or 2 ,
The power steering device is
When the rotation axis of the nut is the second axial direction and the direction around the rotation axis of the nut is the circumferential direction, the end surface in the second axial direction of the nut or the predetermined circumferential range of the outer peripheral surface of the nut And having a ball insertion passage that opens to the outside of the nut and communicates with the nut-side ball screw groove,
The manufacturing method includes:
Inserting a plurality of balls into the nut through the ball insertion path,
Sealing the outside opening of the ball insertion passage with a sealing member ;
A method for manufacturing a power steering apparatus.

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