JP6716931B2 - Rack shaft for steering device and manufacturing method thereof - Google Patents

Description

The present invention is applied to, for example, an electric power steering device for a vehicle, and relates to a rack shaft for a steering device that transmits a steering force and a steering assist force by meshing with both pinion shafts of a steering system and a steering assist system, and a manufacturing method thereof. ..

Conventionally, an electric power steering apparatus for a vehicle includes a rack shaft having a first rack tooth to which a steering force of a steering wheel is transmitted and a second rack tooth to which a steering assist force for assisting the steering force is transmitted. There is one used. In manufacturing such a rack shaft, a rack shaft composed of three members connected to each other has been proposed.

The rack shaft described in Patent Document 1 has a first member having first rack teeth to which a steering force of a steering wheel is transmitted, and a second rack tooth to which a steering assist force for assisting the steering force is transmitted. A second member and an intermediate member having one end connected to the first member and the other end connected to the second member. At the time of manufacturing this rack shaft, the first member is sandwiched between the first tooth flank side support die and the first back face side support die, and the second tooth flank side support die and the second back face side support die are held. The second member is sandwiched by the intermediate member and the intermediate member is rotated while the relative angle between the first rack tooth and the second rack tooth is adjusted and held, and one end surface of the intermediate member is attached to one end surface of the intermediate member by friction welding. And the end face of the second member is joined to the other end face of the intermediate member.

JP, 2014-46803, A

However, when the first member and the second member are frictionally pressure-contacted with the intermediate member, a torsional stress that is considerably larger than the torsional stress that acts when used as an electric power steering device is applied to each member. The rigidity of each member must be high enough to withstand friction welding. Further, the manufacturing apparatus including the pressure welding machine becomes large in scale. Furthermore, due to various conditions at the time of friction welding, variations in the total length of the rack shaft are likely to occur.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a first member having first rack teeth to which a steering force of a steering wheel is transmitted and a second member to which a steering assist force is transmitted. The second member having the rack teeth and the intermediate member arranged between the first member and the second member keep the relative angle between the first rack teeth and the second rack teeth at a predetermined angle. At the same time, it is an object of the present invention to provide a rack shaft for a steering device in which the respective members can be connected to each other without frictionally pressing each other and a manufacturing method thereof.

In order to achieve the above object, the present invention provides a first member having first rack teeth to which a steering force of a steering wheel is transmitted, and a second rack to which a steering assist force for assisting the steering force is transmitted. A second member having teeth, a first screw portion disposed between the first member and the second member, and threadedly coupled to the first member at one end side, and the second member A rack shaft for a steering device, comprising: an intermediate member having a second screw portion that is screw-coupled to the other end side thereof, and the first screw portion and the second screw portion have a reverse screw relationship with each other. provide.

In order to achieve the above object, the present invention provides a first member having first rack teeth to which a steering force of a steering wheel is transmitted, and a second rack tooth to which a steering assist force for assisting the steering force is transmitted. And a second member having a first screw portion disposed between the first member and the second member and threadedly coupled to the first member, and having a screw on the second member. Preparing a rack shaft component including an intermediate member having a second threaded portion to be joined on the other end side and in which the first threaded portion and the second threaded portion have a reverse threaded relationship to each other. And a step of screwing the first screw portion of the intermediate member to the first member and a screw connection of the second screw portion to the second member, the first rack tooth and the first rack tooth. A rack shaft for a steering device, comprising the step of adjusting the total length of the rack shaft to a predetermined length by rotating the intermediate member with the relative angle of the two rack teeth fixed at a predetermined angle. A method of manufacturing the same is provided.

Advantageous Effects of Invention According to the rack shaft for a steering device and the method for manufacturing the same according to the present invention, while maintaining the relative angle between the first rack tooth and the second rack tooth at a predetermined angle, it is intermediate between the first member and the second member. It is possible to join the members without friction welding.

1 is an overall configuration diagram schematically showing a steering device according to an embodiment of the present invention. FIG. 6 is a vertical cross-sectional view of an adjustment jig for explaining a method of adjusting the total length of the rack shaft. 2A is a sectional view taken along line AA of FIG. 2, and FIG. 2B is a sectional view taken along line BB of FIG. (A)-(c) is explanatory drawing explaining the adjustment method of the full length of a rack shaft.

[Embodiment]
FIG. 1 is an overall configuration diagram schematically showing a steering device according to an embodiment of the present invention. The steering device 1 is mounted on a vehicle and steers front wheels, which are steered wheels, in response to a steering operation by a driver. In FIG. 1, the left side of the drawing corresponds to the right side of the vehicle, and the right side of the drawing corresponds to the left side of the vehicle. The letter "R" in the reference numerals in FIG. 1 indicates the right side of the vehicle, and the letter "L" indicates the left side of the vehicle.

The steering device 1 includes a steering wheel 101 rotated by a driver, a column shaft 102 having the steering wheel 101 fixed at one end, and an intermediate shaft (intermediate shaft) connected to the column shaft 102 via a universal joint 111. ) 103, a first pinion shaft 104 connected to the intermediate shaft 103 via a universal joint 112, a rack shaft 2 as a rack shaft that meshes with the first pinion shaft 104, and a driver's operation of the steering wheel 101. The steering assist device 10 generates a steering assist force for assisting.

The universal joints 111 and 112 are cardan joints, for example. The column shaft 102, the intermediate shaft 103, and the first pinion shaft 104 configure the steering shaft 100 connected to the steering wheel 101. On the outer peripheral surface of the first pinion shaft 104, pinion teeth 104a composed of oblique teeth are formed.

The steering assist device 10 includes a steering torque sensor 121 that detects a steering torque on the first pinion shaft 104 of the steering shaft 100, and a control device 13 that outputs a motor current according to the steering torque and the vehicle speed detected by the steering torque sensor 121. The electric motor 130 that generates a steering assist force by the motor current output from the control device 13, the reduction mechanism 14 that reduces the rotation of the output shaft 131 of the electric motor 130, and the electric motor 130 that is reduced by the reduction mechanism 14. The second pinion shaft 12 as a pinion shaft that rotates by torque is provided.

The reduction mechanism 14 includes a worm 132 as a drive gear that is connected to the output shaft 131 of the electric motor 130 so as to rotate integrally with the output shaft 131, and a worm wheel 140 as a reduction gear that meshes with the worm 132. The worm wheel 140 rotates together with the second pinion shaft 12 of the steering assist device 10 and applies a steering assist force to the second pinion shaft 12. On the outer peripheral surface of the second pinion shaft 12, pinion teeth 12a composed of oblique teeth are formed.

Left and right tie rods 16L and 16R are connected to both ends of the rack shaft 2 via ball joints 15L and 15R, respectively. The left and right tie rods 16L and 16R are connected to the left and right front wheels 17L and 17R, respectively. When the rack shaft 2 moves back and forth in the vehicle width direction (left and right direction), the left and right tie rods 16L and 16R swing with respect to the rack shaft 2, and the left and right front wheels 17L and 17R are steered.

The rack shaft 2 includes a first rack tooth 3a meshing with a pinion tooth 104a formed on the first pinion shaft 104 of the steering shaft 100 and a pinion tooth 12a formed on a second pinion shaft 12 of the steering assist device 10. Second rack teeth 4a that mesh with each other are formed. The rack shaft 2 steers the left and right front wheels 17L and 17R by axial movement of the first and second pinion shafts 104 and 12 as the rack shaft 2 rotates.

(Rack shaft configuration)
The rack shaft 2 includes a first rack shaft 3 arranged on the right front wheel 17R side, a second rack shaft 4 arranged on the left front wheel 17L side, a first rack shaft 3 and a second rack shaft. An intermediate member 5 arranged between the shaft 4 and the first rack shaft 3 and the second rack shaft 4, and a first screw shaft 52 of the intermediate member 5 for the first rack shaft 3 which will be described later. A first lock nut 6 for fixing the screwed position of the second rack shaft 4, and a second lock nut 7 for fixing the screwed position of a second screw shaft 53, which will be described later, of the intermediate member 5 with respect to the second rack shaft 4. The first rack shaft 3 is an aspect of the "first member" of the present invention. The second rack shaft 4 is an aspect of the "second member" of the present invention.

The first rack shaft 3 is formed with a first rack tooth 3a that meshes with a pinion tooth 104a formed on the first pinion shaft 104 in a part in the longitudinal direction. The first rack shaft 3 is formed by, for example, rounding a carbon steel round bar into a flat portion at a portion corresponding to the first rack tooth 3a, and then performing a gear cutting process to form the first rack tooth 3a. The end surface on the side of the intermediate member 5 is threaded to form the screw hole 3b, and then the first rack tooth 3a is further heat-treated.

The second rack shaft 4 is formed with a second rack tooth 4a that meshes with a pinion tooth 12a formed on the second pinion shaft 12 of the steering assist device 10 in a part in the longitudinal direction. The second rack shaft 4 is formed, for example, by forging a portion corresponding to the second rack tooth 4a on a round bar made of carbon steel into a flat shape and then performing a gear cutting process to form the second rack tooth 4a. Then, the end surface on the side of the intermediate member 5 is threaded to form the screw hole 4b, and then the second rack tooth 4a is further heat-treated.

The total length of the rack shaft 2 in the longitudinal direction and the relative angle θ (see FIG. 3B) in the cross section of the second rack tooth 4a with respect to the first rack tooth 3a differ depending on the vehicle type. Therefore, in the present embodiment, the rack shaft 2 is divided into three parts, that is, the first rack shaft 3, the second rack shaft 4, and the intermediate member 5, and at least the first rack shaft 3 and the second rack shaft 4 are formed. Is shared, and the total length and relative angle θ according to the vehicle type can be adjusted by the intermediate member 5, the first lock nut 6, and the second lock nut 7.

The intermediate member 5 has a cylindrical main body portion 51, a first screw shaft 52 screwed to the first rack shaft 3, and a second screw shaft 53 screwed to the second rack shaft 4. .. The first screw shaft 52 is on one end side (first rack shaft 3 side) in the longitudinal direction of the main body 51, and the second screw shaft 53 is the other end side (second rack side in the longitudinal direction of the main body 51. The rack shaft 4 side). The first screw shaft 52 and the second screw shaft 53 have a reverse screw relationship with each other. In the present embodiment, the first screw shaft 52 is a right screw and the second screw shaft 53 is a left screw. It is a screw. The first screw shaft 52 is an aspect of the "first screw portion" of the present invention. The second screw shaft 53 is an aspect of the "second screw portion" of the present invention.

A right-handed screw hole 3b into which the first screw shaft 52 of the intermediate member 5 is screwed is formed at the end of the first rack shaft 3 on the intermediate member 5 side. A left-handed screw hole 4b into which the second screw shaft 53 of the intermediate member 5 is screwed is formed at the end of the second rack shaft 4 side on the intermediate member 5 side.

The first screw shaft 52 and the second screw shaft 53 may be screws whose rotation directions when screwing are opposite to each other, and therefore, for example, the first screw shaft 52 is a left-hand screw and the second screw shaft 53 is a second screw shaft. The shaft 53 may be a right-hand screw. If the intermediate members 5 are screwed in directions opposite to each other when the intermediate members 5 are screwed in, the first members of the first screw shaft 52 and the second screw shaft 53, which are male screws, are replaced with “first screw shafts”. A female screw (screw hole) may be formed as the “screw portion” and the “second screw portion”, and a male screw (screw shaft) may be formed on the first rack shaft 3 and the second rack shaft 4. Alternatively, a female screw may be formed at one end of the intermediate member 5 and a male screw may be formed at the other end, and the screw portions of the first rack shaft 3 and the second rack shaft 4 may be screwed together.

In the present embodiment, the first lock nut 6 is screwed onto the first screw shaft 52 and abuts on the axial end face of the first rack shaft 3, and the second lock nut 7 is connected to the second screw shaft 52. It is screwed to 53 and abuts on the axial end surface of the second rack shaft 4. The first lock nut 6 fixes the screwing position of the first screw shaft 52, and the second lock nut 7 fixes the screwing position of the second screw shaft 53. The outer diameters of the first lock nut 6 and the second lock nut 7 are equal to or less than the outer diameters of the first rack shaft 3 and the second rack shaft 4 so as not to hinder the axial movement of the rack shaft 2. Is preferred.

(Jig for adjusting rack shaft)
Next, the configuration of the adjustment jig for the rack shaft 2 will be described with reference to FIGS. 2 and 3. FIG. 2 is a vertical cross-sectional view of an adjustment jig for explaining a method for adjusting the total length of the rack shaft 2, FIG. 3A is a cross-sectional view taken along the line AA of FIG. 2 is a sectional view taken along line BB of FIG. The configuration of the adjusting jig shown in FIGS. 2 and 3 is shown as an example, and in a state where the relative angle between the first rack tooth 3a and the second rack tooth 4a is fixed to a predetermined angle, As long as the total length of the rack shaft 2 can be adjusted to a predetermined length by rotating the intermediate member 5, the rack shaft 2 can be appropriately modified and implemented.

As shown in FIG. 2, the adjustment jig 200 includes a base member 210, a first tooth side support member 220, a first back side support member 230, and a second tooth side support member 240. , And a second back side support member 250.

The base member 210 has a rectangular shape whose long side is along the longitudinal direction of the rack shaft 2, and a T-shaped groove 211 having a T-shaped cross section is formed on the upper surface thereof along the longitudinal direction.

As shown in FIG. 3A, the first tooth flank support member 220 is formed on a rectangular main body portion 221 and a surface of the main body portion 221 on the first back surface side support member 230 side. First rack teeth 222 that mesh with the first rack teeth 3 a of the rack shaft 3 and restrict the movement of the first rack shaft 3 in the axial direction and the rotation direction, and the through hole 224 formed in the main body portion 221. And a bolt 223 through which The first rack teeth 222 may be omitted in the first tooth flank support member 220. In this case, the lower surface (the surface facing the first rack shaft 3) of the main body portion 221 abuts on the tooth top surface of the first rack tooth 3a, so that the first rack shaft 3 moves toward the first tooth surface side. The support member 220 is non-rotatably supported.

As shown in FIG. 3A, the first backside support member 230 has a T-shaped bottom portion 231 having a T-shaped cross section that slidably fits into the T-groove 211 of the base member 210, and the first rack. A V-shaped groove 232 for receiving the shaft 3 and a screw hole 233 into which the bolt 223 is screwed are provided.

As shown in FIG. 3B, the second tooth side support member 240 is formed on a rectangular main body portion 241 and a surface of the main body portion 241 on the second rear surface side support member 250 side. Second rack teeth 242 that mesh with the second rack teeth 4a of the rack shaft 4 and restrict movement of the second rack shaft 4 in the axial direction and the rotation direction, and a through hole 244 formed in the main body 241. And a bolt 243 through which The second rack teeth 242 may be omitted in the second tooth flank support member 240. In this case, the lower surface (the surface facing the second rack shaft 4) of the main body portion 241 abuts on the tooth top surface of the second rack tooth 4a, so that the second rack shaft 4 is on the second tooth surface side. The support member 240 is non-rotatably supported.

As shown in FIG. 3B, the second back side support member 250 has a T-shaped bottom portion 251 having a T-shaped cross section and slidably fitted into the T-groove 211 of the base member 210, and the first rack. The V groove 252 for receiving the shaft 2 and the screw hole 253 into which the bolt 243 is screwed are provided.

In the present embodiment, the V groove 232 of the first back surface side support member 230 is formed without being inclined with respect to the bottom surface 231a of the T-shaped bottom portion 231, and the V groove 252 of the second back surface side support member 250 has the T shape. The bottom portion 251 is formed to be inclined with respect to the bottom surface 251a. In FIG. 3B, the second rack teeth 4a are tilted in the left rotation direction, but may be tilted in the right rotation direction. Moreover, it is not necessary to incline like the first rack teeth 3a.

(Operation of adjustment jig)
4A to 4C are views for explaining a method of adjusting the total length of the rack shaft 2. 4A to 4C, the adjustment jig 200 is not shown.

First, as shown in FIG. 4A, the first rack shaft 3, the second rack shaft 4, the intermediate member 5, the first lock nut 6, and the second lock nut 7 are prepared.

Next, as shown in FIG. 4( b ), the first lock nut 6 is screwed onto the first screw shaft 52 of the intermediate member 5, and the tip of the first screw shaft 52 is attached to the first rack shaft. 3 is screwed into the screw hole 3b. Next, the second lock nut 7 is screwed onto the second screw shaft 53 of the intermediate member 5, and the tip end portion of the second screw shaft 53 is screwed into the screw hole 4b of the second rack shaft 4.

Next, as shown in FIGS. 2 and 3, the peripheral surface of the first rack shaft 3 other than the first rack teeth 3a contacts the V groove 232 of the first rear support member 230, and the second rack The first rack shaft 3 and the second rack shaft 4 are respectively attached to the first rear surface so that the peripheral surface of the shaft 4 other than the second rack teeth 4a contacts the V groove 252 of the second rear surface side support member 250. It is arranged on the side supporting member 230 and the second back side supporting member 250.

Next, as shown in FIGS. 2 and 3, the first rack teeth 222 of the first tooth flank support member 220 are meshed with the first rack teeth 3 a of the first rack shaft 3 to form the first rack teeth 222. The tooth side support member 220 is fixed to the first back side support member 230 with the bolt 223. Similarly, the second rack teeth 242 of the second tooth flank support member 240 are meshed with the second rack teeth 4a of the second rack shaft 4, and the second tooth flank support member 240 is bolted. It is fixed to the second back side support member 250 at 243. The method of fixing the first tooth flank side support member 220 to the first back surface side support member 230 does not need to be the bolt fastening by the bolt 223, and may be the chuck fastening, for example. Similarly, the fixing of the second tooth flank side support member 240 to the second back surface side support member 250 does not have to be bolt fastening with the bolt 243, and may be chuck fastening, for example.

Next, the intermediate member 5 is rotated in a direction in which the first screw shaft 52 and the second screw shaft 53 of the intermediate member 5 are screwed into the first rack shaft 3 and the second rack shaft 4, respectively. As a result, the first screw shaft 52 of the intermediate member 5 is screwed to the first rack shaft 3, and the second screw shaft 53 of the intermediate member 5 is screwed to the second rack shaft 4. The total length of 2 is shortened. As a result, with the relative angle between the first rack tooth 3a and the second rack tooth 4a fixed at a predetermined angle, the intermediate member 5 is rotated to adjust the total length of the rack shaft 2 to a predetermined length.

When the total length of the rack shaft 2 reaches the target value, the rotation of the intermediate member 5 is stopped, the first lock nut 6 and the second lock nut 7 are rotated, and the first rack shaft 3 and the second rack nut are rotated, respectively. The rack shaft 2 is moved to the shaft 4 side and tightened to fix the entire length of the rack shaft 2. A gauge corresponding to the target value of the total length of the rack shaft 2 may be used to determine whether or not the total length of the rack shaft 2 has reached the target value.

When the adjustment of the total length of the rack shaft 2 is completed, the bolt 223 is loosened to remove the first tooth side support member 220 from the first back side support member 230, and the bolt 243 is loosened to support the second tooth side support. The member 240 is removed from the second back side support member 250, and the rack shaft 2 having the adjusted overall length is taken out from the adjustment jig 200. As described above, the rack shaft 2 whose total length is adjusted is manufactured.

When it is desired to change the relative angle of the second rack teeth 4a of the second rack shaft 4 with respect to the first rack teeth 3a of the first rack shaft 3, a second relative angle different from that of the present embodiment is used. The back side support member 250 may be prepared. In this case, it is possible to share other components of the adjustment jig 200 other than the second back surface side support member 250.

Further, when it is necessary to adjust the total length of the rack shaft 2 beyond the adjustment range of the screw shafts 52 and 53 of the intermediate member 5, the screw hole 3b of the first rack shaft 3, and the screw hole 4b of the second rack shaft 4. May be prepared by preparing several kinds of the main body 51 of the intermediate member 5 having different longitudinal directions.

(Operation and Effect of Embodiment)
According to the present embodiment described above, the following actions and effects can be obtained.

(1) The first rack shaft 3, the second rack shaft 4, and the intermediate member 5 are assembled and set in the adjusting jig 200, and the intermediate member 5 is rotated to easily increase the total length of the rack shaft 2. And it can be adjusted reliably. In addition, the manufacturing apparatus can be simplified as compared with the case where the first rack shaft 3 and the second rack shaft 4 and the intermediate member 5 are friction-welded to each other.

(2) The length of the rack shaft 2 is within a range in which the screw shafts 52 and 53 of the intermediate member 5 are screwed into the screw holes 3b of the first rack shaft 3 and the screw holes 4b of the second rack shaft 4. It is possible to easily deal with a plurality of vehicle models having different types.

(3) The screwing position of the first screw shaft 52 is fixed by the first lock nut 6, and the screwing position of the second screw shaft 53 is fixed by the second lock nut 7. The first rack shaft 3 and the second rack shaft 4 can be easily fixed. Further, when it is found that the total length of the rack shaft 2 is not the specified value after the first lock nut 6 and the second lock nut 7 are tightened, the readjustment can be easily performed.

(4) It is necessary to adjust the total length of the rack shaft 2 beyond the adjustment range of the screw shafts 52 and 53 of the intermediate member 5, the screw hole 3b of the first rack shaft 3, and the screw hole 4b of the second rack shaft 4. In this case, since it is only necessary to prepare several kinds of the main body 51 of the intermediate member 5 having different longitudinal directions, at least the first rack shaft 3 and the second rack shaft 4 can be shared.

(5) When changing the relative angle of the second rack teeth 4a of the second rack shaft 4 to the first rack teeth 3a of the first rack shaft 3, replace the second back side support member 250. Therefore, the adjustment jig 200 can share at least the base member 210, the first tooth side support member 220, the first back side support member 230, and the second tooth side support member 240. it can.

(6) Even if one of the first rack tooth 3a and the second rack tooth 4a becomes defective in dimension after cutting and heat treatment of the first rack tooth 3a and the second rack tooth 4a, the dimension becomes defective. Since the first rack shaft 3 or the second rack shaft 4 on the one side may be manufactured, the yield can be improved as compared with the conventional rack shaft which is not divided into three.

(Appendix)
Although the present invention has been described above based on the above-described embodiments, the above-described embodiments do not limit the invention according to the claims. Further, it should be noted that not all the combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

Further, the present invention can be appropriately modified and implemented without departing from the spirit of the present invention. For example, in the above embodiment, the case where the screwing position of the first screw shaft 52 is fixed by the first lock nut 6 and the screwing position of the second screw shaft 53 is fixed by the second lock nut 7 will be described. However, the present invention is not limited to this, and these screwed positions may be fixed by caulking or welding the screw shaft, for example. However, in this case, it becomes difficult to readjust the entire length of the rack shaft 2.

DESCRIPTION OF SYMBOLS 1... Steering device 2... Rack shaft 3... 1st rack shaft (1st member) 3a... 1st rack tooth 4... 2nd rack shaft (2nd member) 4a... 2nd rack tooth 5... Intermediate member 52... First screw shaft (first screw portion)
53... 2nd screw shaft (2nd screw part) 6... 1st lock nut 7... 2nd lock nut

Claims (4)

A first member having first rack teeth to which the steering force of the steering wheel is transmitted;
A second member having second rack teeth to which the steering assisting force for assisting the steering force is transmitted;
A second screw part that is disposed between the first member and the second member, has a first screw part that is screwed to the first member on one end side, and that is screwed to the second member. An intermediate member having the other end side,
The first screw portion and the second screw portion are in a reverse screw relationship with each other,
Rack shaft for steering device. A first lock nut for fixing the screwed position of the first screw portion, and a second lock nut for fixing the screwed position of the second screw portion,
A rack shaft for the steering device according to claim 1. A first member having first rack teeth to which a steering force of a steering wheel is transmitted, a second member having second rack teeth to which a steering assist force for assisting the steering force is transmitted, and the first member, A first screw portion that is disposed between the second member and screwed to the first member is provided on one end side, and a second screw portion that is screwed to the second member is provided on the other end side. And a step of preparing a component of the rack shaft including an intermediate member in which the first screw portion and the second screw portion are in a reverse thread relationship with each other,
Screwing the first screw portion of the intermediate member to the first member, and screwing the second screw portion to the second member;
Adjusting the relative length of the first rack tooth and the second rack tooth to a predetermined angle by rotating the intermediate member so that the total length of the rack shaft is adjusted to a predetermined length. ,
And a method for manufacturing a rack shaft for a steering device including the same. The method further includes the step of fixing the screw-in positions of the first screw portion and the second screw portion with lock nuts, respectively.
A method for manufacturing a rack shaft for a steering device according to claim 3.

Images