JP6421975B2 - Rack shaft manufacturing method, rack shaft and milling machine - Google Patents

Description

  The present invention relates to a method for manufacturing a rack shaft, a rack shaft, and a milling machine.

Patent Document 1 proposes a technique for processing a second tooth portion after joining a first bar having a first tooth portion and a second bar on which a second tooth portion is not formed.
Patent Document 2 proposes a technique of cutting the second rack teeth of the workpiece with the first rack teeth as a reference after hot working of the first rack teeth of the workpiece.

JP 2014-124767 A JP 2002-15442 A

As a stage before cutting the second rack teeth with, for example, a broaching machine, there is a roughing process of machining the second milling surface for machining the second rack teeth with a milling machine.
However, there is a problem in that the phase accuracy around the center axis of the workpiece is not good between the second milling surface for processing the second rack teeth processed in the roughing process and the first rack teeth.
The objective of this invention is providing the rack shaft manufactured by the manufacturing method and milling machine of the rack shaft which can rough-process the 2nd milling surface for 2nd rack tooth processing accurately, and the said manufacturing method.

  According to the first aspect of the present invention, rough machining is performed for roughing the second milling surface (FP2) for machining the second rack tooth on a workpiece having the first milling surface (FP1) before or after machining the first rack teeth. A method of manufacturing a rack shaft (6) including a process (step S6), wherein a center axis (WC) of a workpiece coincides with a reference axis (BC) as a preparation process (step S5) before the roughing process. The workpiece is temporarily clamped between the receiving portion (52a) that receives the back surface (4a) of the first milling surface of the workpiece and the flat pressing portion (54a) that contacts the first milling surface. Temporary clamping step (step S53) for positioning at a reference phase around the axis, and chuck part (73) having a chuck center (CC) that coincides with the reference axis along the end (W1) of the temporarily clamped workpiece. A chucking process for chucking (step S54), a temporary clamp releasing process for releasing the temporary clamp for the chucked workpiece (step S55), and the chuck portion being rotated by a predetermined angle around the chuck center with the temporary clamp released. And a phase adjusting step (step S56) for adjusting the workpiece to a desired phase, thereby providing a method of manufacturing a rack shaft.

In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in embodiment mentioned later, this does not mean that this invention should be limited to those embodiment as a matter of course. The same applies hereinafter.
As in claim 2, in claim 1, as the preparation step, both side portions (101) sandwiching the second milling surface machining scheduled portion (100) of the workpiece adjusted to a desired phase in the position adjustment step in the circumferential direction. , 102) may further include a main clamping step (step S57) in which the main clamping is performed.

A third aspect of the present invention provides a rack shaft manufactured by the method for manufacturing a rack shaft according to the first or second aspect.
The invention of claim 4 includes a base (41), a table (43) supported by the base and capable of adjusting the position in the X-axis direction and Y-axis direction orthogonal to each other, and the Z-axis orthogonal to the X-axis and Y-axis. A tool head (80) including a spindle (81) driven to rotate about a rotation center (K) along the axis and supported by the base, and a center axis (WC) of a workpiece fixed to the table is an X axis or a Y axis A first fixed clamp (52) having a receiving portion (52a) for receiving the back surface (4a) of the first milling surface of the workpiece so as to coincide with a reference axis (BC) along the line, and facing the first fixed clamp, A first movable clamp (54) having a flat pressing portion (54a) which is supported by a table so as to be movable back and forth in the Z-axis direction and abuts against the first milling surface, and the first movable clamp is the first fixed A temporary clamping device (50) for temporarily clamping the workpiece with the receiving portion and the pressing portion so as to position the workpiece at a reference phase so as to position the workpiece at a reference phase. A chuck device main body (72) supported and a chuck center (CC) coinciding with the reference axis line are supported by the chuck device main body so as to be rotatable around the chuck center and chuck the end (W1) of the workpiece. A chuck device (73) including a chuck part (73) and a rotation drive mechanism (74) for rotating the chuck part around the chuck center so as to adjust the workpiece chucked by the chuck part to a desired rotational phase. 70). And a milling machine (40) comprising:

  As in claim 5, in claim 4, a second fixed clamp (62) fixed to the table and received so that a center axis of the workpiece coincides with the reference axis, and a second movable clamp facing the second fixed clamp The clamp device (60) further including a clamp (63) and an advancing / retracting drive mechanism (64) for advancing / retreating the second movable clamp with respect to the second fixed clamp, and a workpiece adjusted to a desired phase Both side portions (101, 102) sandwiching the second milling surface machining scheduled portion (100) in the circumferential direction are configured to be clamped between the second fixed clamp and the second movable clamp. May be.

  According to the method of manufacturing the rack shaft of the first aspect of the invention, the workpiece is temporarily clamped so as to position the workpiece at the reference phase by pressing the first milling surface with the flat pressing portion (temporary clamping step). Next, the end of the workpiece is chucked with a chuck portion having a chuck center coincident with the reference axis (chuck process), and then the temporary clamp is released (temporary clamp release process). Next, the workpiece is adjusted to a desired phase by rotating the chuck portion around the chuck center by a predetermined angle (phase adjustment step). After such a pre-process, rough machining of the second milling surface for machining the second rack teeth is performed. Therefore, rough machining with high accuracy can be performed.

According to the rack shaft manufacturing method of the second aspect of the present invention, the both side portions sandwiching the second milling surface machining scheduled portion of the workpiece, which has been adjusted to a desired phase through the phase adjustment step, in the circumferential direction are finally clamped. . Therefore, when the second milling surface is processed in the subsequent roughing step, rough processing with high accuracy can be performed.
According to the rack shaft of the invention of claim 3, a rack shaft with high dimensional accuracy can be realized.

  According to the milling machine of the fourth aspect of the present invention, in the state where the back surface of the first milling surface of the workpiece is received by the receiving portion of the first fixed clamp so that the center axis of the workpiece coincides with the reference axis, The first movable clamp is driven to the first fixed clamp portion side, and the workpiece is temporarily clamped between the receiving portion of the first fixed clamp and the pressing portion of the first movable clamp. At the time of temporary clamping, the flat pressing portion of the first movable clamp presses the first milling surface, thereby correcting the phase of the workpiece and positioning the workpiece at the reference phase.

  Next, after chucking the end portion of the workpiece by the chuck portion of the chuck device, the temporary clamp by the temporary clamp device is released. In this state, the workpiece is positioned at a desired rotation phase by rotating the chuck portion around the reference axis by a predetermined angle by the rotation drive mechanism. Thereafter, rough machining of the flat second milling surface for machining the second rack teeth is performed. Therefore, rough machining with high accuracy can be performed.

  According to the milling machine of the fifth aspect of the present invention, both side portions sandwiching the second milling surface processing scheduled portion of the workpiece adjusted to a desired phase in the circumferential direction are the second fixed clamp and the second movable clamp of the present clamping device. This is clamped between. Therefore, when machining the second milling surface in the subsequent roughing process, it is possible to perform roughing with high accuracy.

It is a mimetic diagram of a steering device to which a rack shaft manufactured by a manufacturing method of one embodiment of the present invention was applied. It is a schematic front view of a rack shaft. 3A and 3B are cross-sectional views of the rack shaft. FIG. 3A corresponds to a cross-sectional view taken along line 3A-3A in FIG. FIG. 3B corresponds to a cross-sectional view taken along line 3B-3B in FIG. It is a flowchart which shows schematically the flow of the manufacturing method of a rack shaft. It is a schematic front view of a milling machine. It is a schematic side view of a milling machine. It is a schematic perspective view of a temporary clamping device, a main clamping device, a chuck device, and the like arranged on a table of a milling machine. 8A and 8B are schematic views showing the operation of the temporary clamping device. FIG. 8A shows a state before temporary clamping, and FIG. 8B shows a state after temporary clamping. 9A and 9B are schematic views showing the operation of the present clamping device. FIG. 9A shows a state before the main clamping, and FIG. 9B shows a state after the main clamping. It is a flowchart which shows the content of the preparation process as a pre-process of a 2nd milling surface process. 11A to 11D are process diagrams. FIG. 11A shows a process of setting the work on the milling machine, FIG. 11B shows a process of positioning the work in the axial direction, and FIG. 11C shows a temporary clamping process of positioning the work in the reference phase. FIG. 11 (d) shows the chucking process. 12A to 12D are process diagrams. 12A shows a temporary clamp release process, FIG. 12B shows a phase adjustment process, FIG. 12C shows this clamp process, and FIG. 12D rough-processes the second milling surface. The roughing process to be performed is shown. It is a flowchart which shows roughly the flow of the manufacturing method of the rack shaft of another embodiment of this invention.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a steering apparatus 1 to which a rack shaft 6 manufactured by a manufacturing method according to an embodiment of the present invention is applied. FIG. 2 is a schematic front view of the rack shaft 6. 3A is a cross-sectional view of the rack shaft 6 cut along the line 3A-3A in FIG. 2, and FIG. 3B is a rack cut along the line 3B-3B in FIG. It is sectional drawing of the axis | shaft 6. FIG.

  As shown in FIG. 1, the steering device 1 includes a steering mechanism 2 including a rack and pinion mechanism. The steered mechanism 2 is inserted through a rack housing 3 fixed to the vehicle body, and a rack shaft 6 serving as a steered shaft having first rack teeth 4 and second rack teeth 5 is engaged with the first rack teeth 4. A first pinion shaft 8 having one pinion 7 and a second pinion shaft 10 having a second pinion 9 meshing with the second rack teeth 5 are provided.

The steering device 1 is a dual pinion type steering device. The first pinion shaft 8 is for assist force transmission, and the second pinion shaft 10 is for manual steering force transmission.
As shown in FIG. 2, the first rack teeth 4 and the second rack teeth 5 are spaced apart in the axial direction J. As shown in FIGS. 3A and 3B, the first rack teeth 4 and the second rack teeth 5 are formed in phases different from each other in the circumferential direction. The back surface 4a of the first milling surface FP1 processed with the first rack teeth 4 shown in FIG. 3A and the back surface of the second milling surface FP2 processed with the second rack teeth 5 shown in FIG. 3B. 5 a forms a part of a cylindrical surface centered on the central axis RC of the rack shaft 6.

Referring again to FIG. 1, the steering device 1 includes steered wheels 15 connected to the first end 11 and the second end 12 in the axial direction J of the rack shaft 6 via tie rods 13 and knuckles 14, respectively. ing.
When the driver operates the steering member 18, the steering shaft 19, the universal joint 20, the intermediate shaft 21, the universal joint 22, the second pinion shaft 10, the rack shaft 6, and the tie rod 13 are generated by the manual steering force (steering torque). And the steered wheel 15 can be steered through the knuckle 14 sequentially.

In addition, the steering device 1 includes an assist mechanism 23. The assist mechanism 23 includes an electric motor 24 that generates a steering assist force, and a speed reduction mechanism 25 such as a worm gear mechanism that reduces the rotational output of the electric motor 24 and transmits it to the first pinion shaft 8.
The electric motor 24 includes a motor housing 26 fixed to the vehicle body and a rotary shaft 27 as an output shaft. The speed reduction mechanism 25 includes a drive gear 29 such as a worm shaft connected to the rotary shaft 27 via a joint 28 so as to be able to transmit torque, and a worm wheel meshed with the drive gear 29 and connected to the first pinion shaft 8 so as to be integrally rotatable. Etc. and a driven gear 30 such as the above.

A torque sensor 31 that detects a steering torque applied to the steering member 18 is disposed at any position on the path from the steering shaft 19 to the second pinion shaft 10.
The torque detection result of the torque sensor 31 is given to an ECU (Electronic Control Unit) 32. The ECU 32 controls the drive of the electric motor 24 via a built-in drive circuit based on a torque detection result, a vehicle speed detection result given from a vehicle speed sensor (not shown), and the like. The output rotation of the electric motor 24 is decelerated via the speed reduction mechanism 25 and transmitted to the first pinion shaft 8 and converted into a linear motion of the rack shaft 6 to assist steering.

FIG. 4 is a flowchart schematically showing the flow of the method for manufacturing the rack shaft 6. In FIG. 4, the workpiece corresponds to the workpiece W at each processing stage in FIGS. 8, 9, 11, and 12 described later.
First, in step S1, a workpiece in the material stage (a round bar or a round bar having a two-sided width for positioning) is set on a milling machine, and then in step S2, using a milling machine, A first milling surface parallel to the axial direction of the workpiece is roughed (first milling surface roughing step).

Next, after setting the work on the broaching machine in step S3, in step S4, the first rack teeth are machined on the first milling surface using the broaching machine (first rack tooth machining process).
Next, in step S5, a preparatory process as a pre-process of step S6 (second milling surface roughing for roughing a second milling surface parallel to the workpiece axial direction) is performed.

Next, in step S6, a second milling surface is rough-processed on the workpiece using a milling machine (second milling surface roughing step).
Next, after setting the workpiece on the broaching machine in step S7, in step S8, the second rack teeth are machined on the second milling surface using the broaching machine (second rack tooth machining process).

  The preparation step is performed in a milling machine 40 as shown in FIGS. As shown in FIG. 5, the milling machine 40 includes a base 41 and a table 43 supported by the base 41 via a movement guide 42. Further, the milling machine 40 includes an end stopper 44, a temporary clamp device 50, a main clamp device 60, and a chuck device 70, which are disposed on the table 43.

The movement guide 42 is supported by the base 41 so as to be movable in the X axis direction (see FIG. 5) via a slide mechanism (not shown), and the table 43 is supported by the movement guide 42 in the Y axis direction via a slide mechanism (not shown). (Refer to FIG. 6). Thereby, the position of the table 43 can be adjusted in the X-axis direction and the Y-axis direction orthogonal to each other.
As shown in FIG. 5, the main clamping device 60 and the temporary clamping device 50 are disposed between the end stopper 44 and the chuck device 70 in the X-axis direction. The milling machine 40 sets a reference axis BC along the X axis.

  As shown in FIG. 6, the milling machine 40 includes a tool head 80. The tool head 80 is supported by a support arm 45 fixed on the base 41 so that its position can be adjusted in the Z-axis direction via a guide mechanism (not shown). The tool head 80 supports a spindle 81 having a rotation center K along a Z axis perpendicular to both the X axis and the Y axis so as to be rotatable around the rotation center K. An electric motor 82 that rotates the spindle 81 is mounted on the tool head 80. The spindle 81 includes a mechanism (not shown) for chucking the milling cutter 90.

FIG. 7 is a schematic perspective view of the temporary clamp device 50, the main clamp device 60, the chuck device 70, and the like disposed on the table 43.
As shown in FIG. 7, the temporary clamp device 50 includes a height adjustment table 51 fixed on the table 43 and a first fixed clamp 52 fixed on the height adjustment table 51. In addition, the temporary clamp device 50 includes a first movable clamp 54 supported by a support 53 fixed on the height adjustment stand 51 via a guide mechanism (not shown) so as to be able to advance and retract in the Z-axis direction, and a first movable clamp. And an advancing / retracting drive mechanism 55 for advancing / retreating 54 to / from the first fixed clamp 52 side.

As shown in FIG. 8B, the workpiece is clamped between the first fixed clamp 52 and the first movable clamp 54.
As shown in FIG. 7, the 1st fixed clamp 52 consists of V blocks. The 1st fixed clamp 52 is provided with the receiving part 52a which consists of V-grooves. As shown in FIGS. 8A and 8B, the receiving portion 52a has a first milling surface FP1 (first milling surface FP1) of the workpiece W such that the center axis WC of the workpiece W coincides with the reference axis BC along the X axis. The surface FP1 receives the back surface 4a of the rack teeth 4 already processed). The first milling surface FP1 corresponds to the crest portion of the first rack tooth 4 and includes a large number of flat surfaces in the same plane. The 1st movable clamp 54 is a board member which has the press part 54a which consists of a flat surface along XY plane.

As shown in FIG. 7, the advance / retreat drive mechanism 55 includes a main body 55a fixed to the support body 53, and a movable shaft 55b supported by the main body 55a and driven to advance and retreat in the Z-axis direction. The first movable clamp 54 is fixed to the end of the movable shaft 55b and moves integrally with the movable shaft 55b in the Z-axis direction.
The advance / retreat drive mechanism 55 may be a hydraulic mechanism such as a hydraulic cylinder, for example. In addition, although not shown, the advance / retreat drive mechanism 55 may be an electric mechanism that converts the rotation of the electric motor into an axial motion by a ball screw mechanism.

  As shown in FIG. 8B, the temporary clamping device 50 is configured such that the workpiece W is placed between the pressing portion 54 a of the first movable clamp 54 and the receiving portion 52 a of the first fixed clamp 52 lowered by the advance / retreat driving mechanism 55. Is temporarily clamped. At the time of temporary clamping, the pressing portion 54a formed of a flat surface presses the first milling surface FP1 (corresponding to the crest portion of the first rack tooth 4), thereby rotating around the center axis WC (reference axis BC) of the workpiece W. The position is corrected and the workpiece W is positioned at the reference phase.

  As shown in FIG. 7, the chuck device 70 includes a height adjusting table 71 fixed on the table 43, a chuck device main body 72 supported on the height adjusting table 71 so as to be movable in the X-axis direction, a chuck A chuck portion 73 supported by the apparatus main body 72 and a rotation drive mechanism 74 that rotationally drives the chuck portion 73 are provided. The chuck portion 73 has a chuck center CC that coincides with the reference axis BC.

The chuck portion 73 includes a plurality of chuck claws 73a [see FIG. 11D] arranged radially around the chuck center CC. The chuck portion 73 includes a bottom portion 73b [see FIG. 11B] in the X-axis direction.
The rotation drive mechanism 74 is composed of a servo motor. As shown in FIG. 7, the rotation drive mechanism 74 includes a main body 74a fixed to the chuck device main body 72, and a rotation shaft 74b supported by the main body 74a so as to be rotatable around the reference axis BC. A chuck portion 73 is attached to the rotary shaft 74b so as to be integrally rotatable. That is, the chuck portion 73 is supported by the chuck device main body 72 so as to be rotatable around the chuck center CC coinciding with the reference axis BC. The chuck portion 73 chucks one end W1 of the workpiece W.

The rotation drive mechanism 74 rotates the chuck portion 73 around the chuck center CC by a predetermined angle, so that the workpiece W chucked by the chuck portion 73 is adjusted to a desired rotation phase.
A linear drive mechanism 75 that moves the chuck device main body 72 in the X-axis direction is disposed on the height adjustment stand 71 of the chuck device 70. The linear drive mechanism 75 includes a main body 75a fixed on the height adjustment stand 71, and a movable shaft 75b supported by the main body 75a and driven to advance and retract in the X-axis direction.

The linear drive mechanism 75 may be a hydraulic mechanism such as a hydraulic cylinder. Further, although not shown, the linear drive mechanism 75 may be an electric mechanism that converts the rotation of the electric motor into an axial motion by a ball screw mechanism.
As shown in FIG. 7, the clamp device 60 includes a height adjustment table 61, a second fixed clamp 62 composed of a lateral V block fixed on the height adjustment table 61, a second fixed clamp 62 and a Y A second movable clamp 63 facing in the axial direction and an advance / retreat drive mechanism 64 that drives the second movable clamp 63 forward / backward with respect to the second fixed clamp 62 are provided.

The receiving portion 62a made of a V-shaped groove of the second fixed clamp 62 has a first receiving surface 621 formed of a flat surface along the XY plane and a flat surface inclined at an acute angle with respect to the first receiving surface 621 and parallel to the X-axis direction. And a second receiving surface 622.
The advance / retreat drive mechanism 64 includes a main body 64a fixed to the height adjustment base 61, and a movable shaft 64b supported by the main body 64a and driven to advance and retract in the Y-axis direction. The second movable clamp 63 is attached to the end of the movable shaft 64b so as to be movable together. The second movable clamp 63 includes a pressing portion 63a that is a flat surface that is inclined in the opposite direction with respect to the second receiving surface 622 and extends in the X-axis direction.

The advance / retreat drive mechanism 64 may be a hydraulic mechanism such as a hydraulic cylinder. Although not shown, the advance / retreat drive mechanism 64 may be an electric mechanism that converts the rotation of the electric motor into an axial motion by a ball screw mechanism.
As shown in FIGS. 9A and 9B, the clamp device 60 includes a second milling machine for the workpiece W between the receiving portion 62 a of the second fixed clamp 62 and the pressing portion 63 a of the second movable clamp 63. The both side portions 101 and 102 sandwiching the surface machining scheduled portion 100 in the circumferential direction are finally clamped.

Next, the preparation process of step S5 shown in FIG. 4 will be described in detail with reference to FIGS. The workpiece in FIG. 10 corresponds to the workpiece W at each processing stage in FIGS. 11 and 12.
The preparation process sequentially includes steps S51 to S57 shown in FIG. First, in step S51 of FIG. 10, the workpiece W is set on the milling machine 40 [see FIG. 11 (a)]. At this time, the temporary clamp device 50 and the main clamp device 60 are in an unclamped state, and the back surface 4a of the first rack tooth 4 of the workpiece W is the first clamp of the temporary clamp device 50 as shown in FIG. Received by a fixed clamp 52.

Further, as shown in FIG. 9A, the workpiece W is also received by the second fixed clamp 62 of the present clamp device 60. In a state where the workpiece W is received by both the fixed clamps 52 and 62, the center axis WC of the workpiece W coincides with the reference axis BC.
In the set state of the workpiece W shown in FIG. 11A, one end W1 (corresponding to the first end portion 11 of the rack shaft 6) of the workpiece W is spaced from the chuck portion 73 of the chuck device 70 in the X-axis direction. Opposite. Further, the other end W2 of the workpiece W (corresponding to the second end portion 12 of the rack shaft) is opposed to the end stopper 44 with an interval in the X-axis direction.

  Step S52 in FIG. 10 is a positioning process of the workpiece in the axial direction. That is, as shown in FIG. 11 (b), the chuck device main body 72 is moved to the workpiece W side in the X-axis direction by the linear drive mechanism 75 of the chuck device 70, and one end W 1 of the workpiece W is moved to the bottom 73 b of the chuck portion 73. The other end W2 of the workpiece W is brought into contact with the end stopper 44 for axial positioning. Thereby, the workpiece | work W is positioned to an axial direction (X-axis direction). At this time, the chuck portion 73 has not chucked the one end W1 of the workpiece W yet.

  Next, in the temporary clamping step of step S53 in FIG. 10, as shown in FIGS. 11 (c) and 8 (b), the pressing portion 54a composed of the flat surface of the first movable clamp 54 of the temporary clamping device 50 is a workpiece. The workpiece W is temporarily clamped between the first movable clamp 54 and the first fixed clamp 52 while pressing the first milling surface FP1 of W (corresponding to the crest portion of the first rack tooth 4). At the time of temporary clamping, the phase of the workpiece W is adjusted to a reference phase around the reference axis BC.

Next, in the chucking process of step S54 in FIG. 10, as shown in FIG. 11D, one end W1 of the temporarily clamped workpiece W is chucked by the chuck portion 73 having the chuck center CC that coincides with the reference axis BC. . That is, the outer periphery of the one end W1 of the workpiece W is chucked by the plurality of chuck claws 73a arranged radially.
Next, in the temporary clamp release process of step S55 of FIG. 10, the movable shaft 55b of the advance / retreat drive mechanism 55 of the temporary clamp device 50 is shortened as shown in FIG. When the clamp 54 is retracted (raised), the temporary clamp for the workpiece W in the chucked state is released, and the unclamped state is set.

  Next, in the phase adjustment step of step S56 in FIG. 10, as shown in FIG. 12B, the rotation drive mechanism 74 of the chuck device 70 rotates the rotation shaft 74b by a predetermined angle, and the chuck portion 73 is rotated around the chuck center CC. The workpiece W is adjusted to a desired phase by rotating it by a predetermined angle. The predetermined angle is an angle corresponding to the phase difference between the first rack teeth 4 and the second rack teeth 5 shown in FIGS.

Next, in the main clamping step of step S56 in FIG. 10, as shown in FIGS. 9B and 12C, the second movable clamp 63 of the main clamping device 60 advances and is shown in FIG. 9B. As described above, the both side portions 101 and 102 sandwiching the second milled surface machining scheduled portion 100 of the workpiece W adjusted in phase in the circumferential direction are finally clamped. Thereby, a preparation process is completed.
Thereafter, as shown in FIG. 12D, while the table 43 is fed in the X-axis direction, the milling cutter 90 attached to the spindle 81 of the tool head 80 causes the second milling surface machining scheduled portion 100 of the workpiece W to be The second milling surface FP2 is roughed (corresponding to step S6 in FIG. 4).

  According to the rack shaft manufacturing method of the present embodiment, the flat surface is received in a state where the back surface 4a of the first milling surface FP1 of the workpiece W is received by the receiving portion 52a so that the center axis WC of the workpiece W coincides with the reference axis BC. The workpiece W is temporarily clamped so as to position the workpiece W at the reference phase by pressing the first milling surface FP1 (corresponding to the crest portion of the first rack tooth 4) by the pressing portion 54a [temporary clamping step. See FIG. 8 (b) and FIG. 11 (c)].

Next, after one end W1 of the temporarily clamped workpiece W is chucked by the chuck portion 73 having the chuck center CC coinciding with the reference axis BC [Chucking process. FIG. 11 (d)], the temporary clamp is released [temporary clamp releasing step. See FIG. 12 (a)].
Next, the workpiece W is adjusted to a desired phase by rotating the chuck portion 73 by a predetermined angle around the chuck center CC [phase adjustment step. See FIG. 12 (b)]. After such a pre-process, rough machining of the flat second milling surface FP2 for second rack tooth machining (rough machining process of the second milling surface in step S6 in FIG. 4) is performed. Therefore, rough machining with high accuracy can be performed.

Further, according to the manufacturing method of the present embodiment, both side portions 101 and 102 sandwiching the second milling surface machining scheduled portion 100 of the workpiece W that has been adjusted to a desired phase through the phase adjustment step in the circumferential direction are the main clamps. [This clamping process. See FIG. 9 (b)]. Therefore, when the second milling surface FP2 is processed in the subsequent roughing process, rough processing with high accuracy can be performed.
Further, if the rack shaft 6 is manufactured by the manufacturing method of the present embodiment, the rack shaft 6 with high dimensional accuracy can be realized particularly with respect to the positional relationship between the first rack teeth 4 and the second rack teeth 5.

  Further, according to the milling machine 40 of the present embodiment, the back surface 4a of the first rack tooth 4 of the work W is fixed to the first fixed clamp 52 of the temporary clamp device 50 so that the center axis WC of the work W coincides with the reference axis BC. The first movable clamp 54 is driven to the first fixed clamp 52 side while being received by the receiving portion 52a, and between the receiving portion 52a of the first fixed clamp 52 and the flat pressing portion 54a of the first movable clamp 54. Then, the workpiece W is temporarily clamped. At the time of temporary clamping, the flat pressing portion 54a of the first movable clamp 54 presses the first milling surface FP1 (corresponding to the crest portion of the rack tooth 4), thereby correcting the phase of the workpiece W and using the workpiece W as a reference. Position to phase.

  Next, after chucking one end W <b> 1 of the workpiece W by the chuck portion 73 of the chuck device 70, the temporary clamp by the temporary clamp device 50 is released. In this state, the workpiece W is positioned at a desired rotational phase by rotating the chuck portion 73 around the chuck center CC (reference axis BC) by a predetermined angle by the rotation drive mechanism 74 of the chuck device 70. After that, rough machining is performed on the flat second milling surface FP2 for machining the second rack teeth. Therefore, rough machining with high accuracy can be performed.

  Further, according to the milling machine 40 of the present embodiment, as shown in FIG. 9B, both side portions 101 sandwiching the second milling surface machining scheduled portion 100 of the workpiece W adjusted to a desired phase in the circumferential direction, 102 is clamped between the second fixed clamp 62 and the second movable clamp 63 of the clamp device 60. Therefore, when the second milling surface FP2 is processed in the subsequent roughing process, rough processing with high accuracy can be performed.

  The present invention is not limited to the above embodiment. In FIG. 1, the first rack tooth 4 is for assist force transmission and the second rack tooth 5 is for manual steering force transmission. Instead, the first rack tooth 4 is for manual steering force transmission. The second rack teeth 5 may be used for assist force transmission. The left-right positional relationship between the first rack teeth 4 and the second rack teeth 5 may be reversed.

In FIG. 7, the arrangement positions of the second fixed clamp 62 and the second movable clamp 63 may be interchanged with respect to the Y-axis direction.
Further, the end stopper 44 may have a function of chucking the other end W2 of the workpiece W. Further, the reference axis BC may be set along the Y axis.
Further, instead of the process flow shown in FIG. 4, the process flow shown in FIG. 13 may be performed. Specifically, first, in step S11, a workpiece in the material stage (a round bar or a round bar having a two-sided width for positioning) is set on the milling machine, and then in step S12, the milling machine is set. The first milling surface parallel to the workpiece axial direction is rough-worked on the workpiece (first milling surface roughing step).

Next, in step S13, a preparatory step is performed as a pre-step of step S14 (second milling surface roughing for roughing the second milling surface parallel to the workpiece axial direction).
Next, in step S14, the milling machine is used to rough the second milling surface (second milling surface roughing process).

Next, after setting the work on the broaching machine in step S15, in step S16, the first rack teeth are machined on the first milling surface using the broaching machine (first rack tooth machining process).
Next, in step S17, the second rack teeth are processed on the second milling surface using a broaching machine (second rack tooth processing step).

In this case, the number of operations for removing the workpiece from the milling machine and attaching it to the broaching machine can be reduced, and the setup time can be shortened.
In addition, the present invention can be variously modified within the scope of the claims.

  DESCRIPTION OF SYMBOLS 1 ... Steering device, 4 ... 1st rack tooth | gear, 4a ... Back surface (1st milling surface), 5 ... 2nd rack tooth | gear, 6 ... Rack shaft, 7 ... 1st pinion, 8 ... 1st pinion shaft, 9 ... 2nd pinion, 10 ... 2nd pinion shaft, 40 ... milling machine, 41 ... base, 42 ... moving guide, 43 ... table, 44 ... end stopper, 45 ... support arm, 50 ... temporary clamping device, 51 ... height adjustment 52, first fixed clamp, 52a, receiving portion, 53, support, 54, first movable clamp, 54a, pressing portion, 55, forward / backward drive mechanism, 55a, main body, 55b, movable shaft, 60, main clamp Device: 61 ... Height adjustment stand, 62 ... Second fixed clamp, 62a ... Receiving portion, 621 ... First receiving surface, 622 ... Second receiving surface, 63 ... Second movable clamp, 63a ... Pressing portion, 64 ... Advancing and retreating Drive mechanism, 64a ... main body, 6 b: movable shaft, 70: chuck device, 71: height adjustment base, 72: chuck device main body, 73: chuck portion, 73a: chuck claw, 73b: bottom portion, 74: rotational drive mechanism, 74a: main body, 74b: rotation Axis, 75 ... linear drive mechanism, 75a ... main body, 75b ... movable shaft, 80 ... tool head, 81 ... spindle, 82 ... electric motor, 90 ... milling cutter, 100 ... second milling surface machining scheduled part, 101, 102 ... Both side portions (with the second milling surface machining target portion sandwiched in the circumferential direction), FP1... 1st milling surface, FP2... 2nd milling surface, K... (Spindle) rotation center, BC. , RC ... center axis of (rack axis), W ... work, W1 ... one end, W2 ... other end, WC ... center axis of (work)

Claims (5)

A rack shaft manufacturing method including a roughing step of roughing a second milling surface for processing a second rack tooth on a workpiece having a first milling surface before or after processing the first rack tooth,
As a preparation step before the roughing step,
The workpiece is temporarily clamped between the receiving portion that receives the back surface of the first milling surface of the workpiece and the flat pressing portion that contacts the first milling surface so that the center axis of the workpiece coincides with the reference axis line. A temporary clamping step for positioning to a reference phase around the reference axis;
A chucking step of chucking the end of the temporarily clamped workpiece with a chuck having a chuck center coinciding with the reference axis;
A temporary clamp releasing step for releasing the temporary clamp on the chucked workpiece;
And a phase adjusting step of adjusting the workpiece to a desired phase by rotating the chuck portion around the chuck center by a predetermined angle in a state where the temporary clamp is released.   2. The rack according to claim 1, further comprising a main clamping step in which both side portions sandwiching the second milling surface processing scheduled portion of the workpiece adjusted to a desired phase in the position adjusting step in the circumferential direction are finally clamped as the preparation step. Shaft manufacturing method.   A rack shaft manufactured by the method for manufacturing a rack shaft according to claim 1 or 2. Base and
A table supported by the base and adjustable in position in the X-axis direction and the Y-axis direction orthogonal to each other;
A tool head supported by the base including a spindle that is driven to rotate about a rotation center along a Z axis perpendicular to the X axis and the Y axis;
A first fixed clamp having a receiving portion that is fixed to the table and receives a back surface of the first milling surface of the workpiece such that a center axis of the workpiece coincides with a reference axis along the X-axis or the Y-axis; and the first fixed clamp; A first movable clamp that is opposed to and supported by the table so as to advance and retreat in the Z-axis direction and has a flat pressing portion that contacts the first milling surface, and a forward and backward drive that advances and retracts the first movable clamp toward and away from the first fixed clamp. A temporary clamping device that temporarily clamps the workpiece with the receiving portion and the pressing portion so as to position the workpiece at a reference phase.
A chuck device main body supported by the table, a chuck portion having a chuck center coinciding with the reference axis, and rotatably supported around the chuck center by the chuck device main body, and chucking an end of a workpiece; and the chuck A milling machine comprising: a chuck device including a rotation drive mechanism that rotates the chuck portion around the center of the chuck so as to adjust a workpiece chucked by the portion to a desired rotation phase. 5. The second fixed clamp fixed to the table and received so that a center axis of a workpiece coincides with the reference axis, a second movable clamp opposed to the second fixed clamp, and the second movable clamp The clamp device further including an advancing / retreating drive mechanism that advances / retreats with respect to the second fixed clamp;
Both side portions sandwiching the second milling surface machining scheduled portion of the workpiece adjusted to a desired phase in the circumferential direction are configured to be clamped between the second fixed clamp and the second movable clamp. Milling machine.

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