JP7419962B2 - Steering device manufacturing method and steering device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a steering device for steering steerable wheels of a vehicle, and a steering device.

Conventionally, in vehicle steering devices, an endless belt is looped between a drive pulley driven by an electric motor and a driven pulley that has a larger diameter than the drive pulley, and a ball screw nut that rotates together with the driven pulley is rotated. Some vehicles steer the steered wheels of a vehicle by rotating the steered shaft relative to a rudder shaft (rack shaft) and moving the steered shaft forward and backward.

Patent Document 1 discloses that a cylindrical sleeve is attached to the opening of a housing that accommodates a driving pulley, and an endless belt (toothed belt) is wound between an assembly mandrel guided by this sleeve and a driven pulley. An assembly method is described in which a drive pulley and an endless belt are engaged by pushing an assembly mandrel axially by a drive pulley (pinion).

German Publication DE 10 2007 019 258 A1

In the assembly method described in Patent Document 1, it is necessary to seal the opening of the housing with some kind of sealing member after the drive pulley and the endless belt are engaged, resulting in an increase in the number of parts and the number of assembly steps.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for manufacturing a steering device and a steering device that can suppress an increase in the number of parts and assembly man-hours even though an endless belt is wound around a driven pulley and a drive pulley. purpose.

In order to achieve the above object, the present invention provides a steering shaft for steering steering wheels of a vehicle, a ball screw nut that is screwed onto the steering shaft via a plurality of balls, and an integrated body with the ball screw nut. a rotating driven pulley, a driving pulley rotationally driven by an electric motor, an endless belt wrapped around the driven pulley and the driving pulley, and a first housing member housing at least a portion of the ball screw nut; A bearing rotatably supports the driven pulley and the ball screw nut with respect to the first housing member, and an insertion hole that accommodates the drive pulley and the endless belt and allows the drive pulley to be inserted therethrough. a first step of assembling the driven pulley, the ball screw nut, and the bearing to the first housing member; a second step of causing a member to temporarily hold a jig so that the endless belt is wound between the jig and the driven pulley; and fastening the first housing member and the second housing member. and a fourth step of removing the jig, inserting the drive pulley into the second housing member through the insertion hole, and arranging the drive pulley inside the endless belt. In the second step, the jig is temporarily held by fitting into the first housing member along a direction parallel to the steering axis, and in the fourth step, the jig is temporarily held in the first housing member in a direction parallel to the steering axis. A method for manufacturing a steering device is provided , in which the steering device is taken out from the second housing member through the insertion hole .

Further, in order to achieve the above object, the present invention provides a steering shaft for steering steering wheels of a vehicle, a ball screw nut screwed onto the steering shaft via a plurality of balls, and the ball screw nut. a driven pulley that rotates integrally with the driven pulley, a driving pulley that is rotationally driven by an electric motor, an endless belt that is wound around the driven pulley and the driving pulley, and a first housing member that houses at least a portion of the ball screw nut. a bearing that rotatably supports the driven pulley and the ball screw nut with respect to the first housing member; and an insertion hole that accommodates the drive pulley and the endless belt and allows the drive pulley to be inserted therethrough. a second housing member having a hole formed therein, the first housing member having the endless belt wrapped around the driven pulley on a surface facing the insertion hole; A steering device is provided, which includes a first holding part for temporarily holding a holding jig, and the jig includes a second holding part that engages with the first holding part.

According to the method for manufacturing a steering device and the steering device according to the present invention, it is possible to suppress increases in the number of parts and assembly man-hours even though an endless belt is used that is wound around the driven pulley and the drive pulley.

1 is a schematic diagram showing the configuration of a steering device according to an embodiment of the present invention. FIG. 3 is a sectional view showing a steering assist device of the steering device. FIG. 3 is a configuration diagram of the first housing member viewed from the second housing member side. FIG. 3 is a configuration diagram of the second housing member viewed from the first housing member side. FIG. 3 is a cross-sectional view showing the steps for assembling the steering device. FIG. 3 is a cross-sectional view showing the steps for assembling the steering device. FIG. 3 is a cross-sectional view showing the steps for assembling the steering device.

[Embodiment]
Embodiments of the present invention will be described with reference to the drawings. The embodiments described below are shown as preferred specific examples for carrying out the present invention, and some portions specifically illustrate various technical matters that are technically preferable. However, the technical scope of the present invention is not limited to this specific embodiment.

(Configuration of steering device)
FIG. 1 is a schematic diagram showing the overall configuration of a steering device according to an embodiment of the present invention. This steering device 1 is mounted on a vehicle and steers left and right front wheels, which are steerable wheels, in response to a steering operation by a driver. FIG. 1 shows the steering device viewed from the front of the vehicle, with the left side of the drawing corresponding to the right side of the vehicle, and the right side of the drawing corresponding to the left side of the vehicle. Note that the letter "R" in the reference numeral 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 shaft 11 connected to a steering wheel 10 that is steered by a driver, a rack shaft 2 as a steering shaft that moves forward and backward along the width direction of the vehicle by the steering operation of the steering wheel 10, and a rack shaft 11 that is connected to a steering wheel 10 that is steered by a driver. The steering wheel includes a housing 12 including a first housing member 3 and a second housing member 4, and a steering assist device 13 that generates a steering assist force in accordance with the steering torque applied to the steering wheel 10. The first housing member 3 and the second housing member 4 are bolted together using a plurality of bolts 121.

The steering shaft 11 includes a column shaft 111 to which the steering wheel 10 is fixed at one end, an intermediate shaft 113 connected to the column shaft 111 via a universal joint 112, and a universal joint to the intermediate shaft 113. It has a pinion shaft 115 connected via a pinion shaft 114. The universal joints 112, 114 are made of, for example, cardan joints.

A pinion tooth portion 115a is formed at the tip of the pinion shaft 115, and the rack tooth portion 2a of the rack shaft 2 is meshed with the pinion tooth portion 115a. Further, the pinion shaft 115 includes a torsion bar 115b having flexibility to be twisted by steering torque applied to the steering wheel 10. A torque sensor 110 is arranged around the torsion bar 115b to detect steering torque based on the twisting of the torsion bar 115b.

An outer ball screw groove 21 is spirally formed on the outer circumferential surface of the rack shaft 2 at the end opposite to the end on which the rack teeth 2a are formed. The rack shaft 2 receives a steering assist force from the steering assist device 13 through the outer circumferential ball screw groove 21 .

The steering device 1 also includes ball joints 14L and 14R attached to both ends of the rack shaft 2 protruding from the housing 12, and left and right wheels that are swingably connected to the rack shaft 2 by the ball joints 14L and 14R. It has tie rods 15L, 15R, and bellows 16L, 16R having an accordion structure arranged between both ends of the housing 12 and the tie rods 15L, 15R. By moving along the vehicle width direction, the rack shaft 2 steers the left and right front wheels via the ball joints 14L, 14R and the left and right tie rods 15L, 15R.

The steering assist device 13 includes an electric motor 51 that is a drive source, and a controller 52 that controls the electric motor 51. In this embodiment, an electric motor 51 and a controller 52 are integrated to form an MCU (Motor Controller Unit) 5. The controller 52 is supplied with power from the vehicle's battery through a power line 521 and receives a signal indicating the detected value of the torque sensor 110 through a signal line 522 . The controller 52 controls the electric motor 51 based on information such as steering torque and vehicle speed detected by the torque sensor 110. The electric motor 51 is attached to a motor attachment flange 43 provided on the second housing member 4 with a plurality of bolts 122.

FIG. 2 is a sectional view showing the steering assist device 13. FIG. 3A is a configuration diagram of the first housing member 3 viewed from the second housing member 4 side. FIG. 3B is a configuration diagram of the second housing member 4 viewed from the first housing member 3 side. Hereinafter, the direction parallel to the central axis of the rack shaft 2 will be referred to as the axial direction.

The steering assist device 13 includes a ball screw nut 61 that is screwed onto the rack shaft 2 via a plurality of balls 20, a driven pulley 62 that rotates integrally with the ball screw nut 61, and a drive pulley 53 that is rotationally driven by an electric motor 51. , an endless belt 7 that is wound around a driven pulley 62 and a driving pulley 53, and a bearing 8 that rotatably supports the ball screw nut 61 and the driven pulley 62 with respect to the first housing member 3.

An inner ball screw groove 611 is spirally formed on the inner peripheral surface of the ball screw nut 61, and a plurality of balls are formed between the inner ball screw groove 611 and the outer ball screw groove 21 of the rack shaft 2. 20 are arranged. A circulation path 610 is formed in the ball screw nut 61, and the plurality of balls 20 circulate endlessly through the circulation path 610. A driven pulley 62 is fixed to the ball screw nut 61 with a plurality of bolts 63. When the driven pulley 62 rotates together with the ball screw nut 61, the rack shaft 2 moves forward and backward in the vehicle width direction.

In this embodiment, the bearing 8 is a double row ball bearing of the DAC (double angular contact) type, and between a pair of inner rings 81, 81, an outer ring 82, and a pair of inner rings 81, 81 and outer ring 82. It has a plurality of spherical rolling elements 83 arranged in the same direction, and a pair of cages 84, 84 that hold the spherical rolling elements 83. The pair of inner rings 81, 81 are fixed to the outer periphery of the ball screw nut 61 by a lock nut 64 screwed onto the ball screw nut 41, and are given an axial preload.

The first housing member 3 includes a small-diameter cylindrical portion 31 that forms an accommodation space 301 that accommodates the rack shaft 2, and a large-diameter cylindrical portion 32 that forms an accommodation space 302 that accommodates a part of the ball screw nut 61 together with the bearing 8. , a wall portion 33 protruding radially outward from the large diameter cylindrical portion 32, a first protrusion 34 protruding axially from the large diameter cylindrical portion 32, and a plurality of holes for fastening to the second housing member 4. It integrally has a fastening flange 35 (shown in FIG. 3A). The wall portion 33 protrudes radially outward from a portion of the large diameter cylinder portion 32 in the circumferential direction, and faces the drive pulley 53 in the axial direction. The first protrusion 34 has an arcuate shape when viewed from the second housing member 4 side. Each of the plurality of fastening flanges 35 is formed with a bolt hole 350 through which the bolt 121 (shown in FIG. 1) is inserted.

In this embodiment, the entire driven pulley 62 is exposed in the axial direction from the large diameter cylindrical portion 32 of the first housing member 3, so that the endless belt 7 can be hung around the driven pulley 62 when assembling the steering device 1. It makes turning work easier. However, it is sufficient that at least a portion of the driven pulley 62 is exposed to the outside of the first housing member 3.

The drive pulley 53 is fixed to a motor shaft 511 of the electric motor 51. The outer diameter of the drive pulley 53 is smaller than the outer diameter of the driven pulley 62, and the rotation of the drive pulley 53 is decelerated by the endless belt 7 and transmitted to the driven pulley 62. A plurality of teeth 71 that mesh with the driving pulley 53 and the driven pulley 62 are provided on the inner surface of the endless belt 7 . The rotation axes of the drive pulley 53 and the motor shaft 511 are parallel to the central axis of the rack shaft 2.

The second housing member 4 includes a small-diameter cylindrical portion 41 that forms an accommodation space 401 that accommodates the rack shaft 2, a peripheral wall portion 42 that forms an accommodation space 402 that accommodates the driven pulley 62, and an accommodation space 403 that accommodates the drive pulley 53. For fastening the motor mounting flange 43 to which the electric motor 51 is attached, the second protrusion 44 protruding in the axial direction from the motor mounting flange 43 toward the first housing member 41, and the first housing member 3. It integrally has a plurality of fastening flanges 45 (shown in FIG. 3B). The endless belt 7 is housed in the peripheral wall 42 across the housing spaces 402 and 403. Bolt holes 450 are formed in each of the plurality of fastening flanges 45.

The second protrusion 44 has an arcuate shape when viewed from the first housing member 3 side, and is provided between an accommodation space 402 that accommodates the driven pulley 62 and an accommodation space 403 that accommodates the drive pulley 53. . Further, the second protrusion 44 has an inner tip surface 44a that sandwiches the outer ring 82 of the bearing 8 between it and a stepped surface 32a formed on the large diameter cylindrical portion 32 of the first housing member 3; It has an outer tip surface 44b that comes into contact with the tip surface 34a of the first protrusion 34. Note that an elastic body such as a disc spring that elastically allows the outer ring 82 to move in the axial direction with respect to the first housing member 3 may be arranged between the step surface 32a and the inner end surface 44a and the outer ring 82.

The motor mounting flange 43 is formed with an insertion hole 430 through which the drive pulley 53 can be inserted. The insertion hole 430 has a circular shape when viewed from the first housing member 3 side, and its inner diameter is larger than the outer diameter of the drive pulley 53. An accommodation space 403 that accommodates the drive pulley 53 in the second housing member 4 is closed by the wall portion 33 of the first housing member 3 .

The wall portion 33 is provided with a first holding portion for temporarily holding a jig 9, which will be described later, on a surface 33a of the inner surface of the first housing member 3 and facing the insertion hole 430. In this embodiment, this first holding portion is a recess 330 formed by recessing in the axial direction from the surface 33a. The recess 330 is a blind hole formed at a position facing the end surface of the drive pulley 53 in the axial direction, and does not penetrate to the back surface 33b, which is the outer surface of the first housing member 3. In FIG. 3A, the jig 9 and the endless belt 7 are illustrated by imaginary lines (two-dot chain lines).

(Manufacturing method of steering device)
Next, a method for manufacturing the steering device 1 will be explained. The method for manufacturing the steering device 1 includes a first step of assembling the driven pulley 62, ball screw nut 61, and bearing 8 to the first housing member 3, temporarily holding the jig 9 on the first housing member 3, and attaching the jig 9 to the first housing member 3. a second step in which the endless belt 7 is placed around the driven pulley 62; a third step in which the first housing member 3 and the second housing member 4 are fastened together; and a third step in which the jig 9 is removed. A fourth step of inserting the drive pulley 53 into the second housing member 4 through the insertion hole 430 of the motor mounting flange 43 and arranging the drive pulley 53 inside the endless belt 7; and separating the drive pulley 53 from the driven pulley 62. and a fifth step of applying tension to the endless belt 7.

FIG. 4A shows how a ball screw nut 61 to which a driven pulley 62 is fixed by a plurality of bolts 63 is assembled to the first housing member 3 via a bearing 8, and a jig 9 is held on the wall 33 of the first housing member 3. FIG. The vertical direction in FIG. 4A indicates the vertical direction. The driven pulley 62 is arranged so that its entirety projects upward from the first housing member 3.

The jig 9 has a cylindrical main body 91 and a convex part 92 as a second holding part that is fitted into the recess 330 of the wall 33 . It is temporarily held perpendicular to 33a. That is, the jig 9 is temporarily held by fitting into the first housing member 3 along a direction parallel to the rack shaft 2 .

FIG. 4B is a sectional view showing a state in which the endless belt 7 is stretched between the jig 9 and the driven pulley 62. By being passed around the jig 9, the endless belt 7 is supported without coming into contact with the large-diameter cylindrical portion 32 of the first housing member 3, as shown in FIG. 3A.

FIG. 4C shows a state in which the second housing member 4 is assembled on the first housing member 3 in a predetermined positional relationship, that is, the axes of both small diameter cylindrical parts 31 and 41 are aligned, and a housing space 403 is formed. It is a sectional view showing a state where parts are assembled so that they fit together. At this time, since the endless belt 7 is wrapped around the jig 9, the endless belt 7 is not caught between the first housing member 3 and the second housing member 4, and the endless belt 7 is not caught between the first housing member 3 and the second housing member 4. 2 and the housing member 4 can be bolted together. After this, the first housing member 3 and the second housing member 4 are fastened together using a plurality of bolts 121 (shown in FIG. 1).

In the fourth step, after achieving the state shown in FIG. 4C, the jig 9 is taken out from the second housing member 4 through the insertion hole 430 of the motor mounting flange 43 and driven into the second housing member 4 through the insertion hole 430. The pulley 53 is inserted and the driving pulley 53 is arranged inside the endless belt 7. In this state, the endless belt 7 has slack, and the drive pulley 53 can be easily placed inside the endless belt 7.

The drive pulley 53 is inserted into the second housing member 4 through the insertion hole 430 while being fixed to the motor shaft 511 of the electric motor 51 . Thereafter, the steering device 1 is assembled by attaching the electric motor 51 to the motor attachment flange 43 of the second housing member 4 with a plurality of bolts 122 (shown in FIG. 1). As shown in FIG. 3B, the motor mounting flange 43 has a first bolt insertion hole 431 and a second bolt insertion hole 432 formed therein. The first bolt insertion hole 431 and the second bolt insertion hole 432 penetrate the motor mounting flange 43 in the axial direction.

The first bolt insertion hole 431 is a circular through hole having an inner diameter corresponding to the outer diameter of the bolt 122. The second bolt insertion hole 432 is an arc-shaped through hole that is long in the circumferential direction with the first bolt insertion hole 431 at its center, and the bolt 122 is inserted into the first bolt insertion hole 431 and the second bolt insertion hole 432, respectively. In this state, it is possible to swing the electric motor 51 around the first bolt insertion hole 43. FIG. 3B shows the contours of the drive pulley 53 when the bolt 122 inserted into the second bolt insertion hole 432 is located at one end in the longitudinal direction of the second bolt insertion hole 432 and when the bolt 122 is located at the other end in the longitudinal direction. It is shown by a virtual line (two-dot chain line).

The electric motor 51 is provided with a plurality of mounting flanges 512 (shown in FIG. 1) into which a plurality of bolts 122 are threaded, respectively. In this embodiment, two mounting flanges 512 are provided to protrude from the outer circumferential surface at the axial end of the electric motor 51, corresponding to the first bolt insertion hole 431 and the second bolt insertion hole 432, and are provided in FIG. Here, one of the mounting flanges 512 is illustrated.

When attaching the electric motor 51 to the motor mounting flange 43, the bolts 122 inserted through the first bolt insertion holes 431 and the second bolt insertion holes 432 are loosely screwed into the mounting flange 511 of the electric motor 51, The electric motor 51 is swung around the first bolt insertion hole 43 to separate the drive pulley 53 from the driven pulley 62 and apply tension to the endless belt 7. Then, the bolts 122 are tightened while applying tension to the endless belt 7.

As a result, the electric motor 51 is fixed to the motor mounting flange 43 as shown in FIG. 2 while the endless belt 7 is under tension. By applying tension to the endless belt 7, the teeth of the plurality of teeth 71 of the endless belt 7 are prevented from skipping when the driving pulley 53 and the driven pulley 62 rotate.

(Effects of embodiment)
According to the embodiment described above, when the first housing member 3 and the second housing member 4 are assembled and fastened, the endless belt 7 is sandwiched between the first housing member 3 and the second housing member 4. Therefore, it is possible to prevent the assembly from being difficult and from damaging the endless belt 7. Furthermore, as there is no need to seal the opening of the housing with some kind of sealing member after the drive pulley and the endless belt are engaged, as described in Patent Document 1, for example, the number of parts and the number of assembly steps can be increased. It becomes possible to suppress this.

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

Moreover, the present invention can be implemented with appropriate modifications by omitting some configurations, or adding or replacing configurations, without departing from the spirit thereof. For example, in the above embodiment, a case has been described in which the jig 9 is provided with the convex portion 92 and the wall portion 33 of the first housing member 3 is formed with the recess 330. , a convex portion provided on the wall portion 33 may be fitted into this concave portion.

1...Steering device 2...Rack shaft (steering shaft)
3...First housing member 330...Recessed portion (first holding portion)
33a...Front surface 33b...Back surface 4...Second housing member 43...Motor mounting flange 430...Through hole 51...Electric motor 53...Drive pulley 61...Ball screw nut 62...Followed pulley 7...Endless belt 8...Bearing 9...Jig 92 ...Convex part (second holding part)

Claims (5)

A steering shaft for steering the steering wheels of a vehicle;
a ball screw nut that is screwed onto the steered shaft through a plurality of balls;
a driven pulley that rotates integrally with the ball screw nut;
a drive pulley rotationally driven by an electric motor;
an endless belt wrapped around the driven pulley and the driving pulley;
a first housing member that accommodates at least a portion of the ball screw nut;
a bearing rotatably supporting the driven pulley and the ball screw nut with respect to the first housing member;
a second housing member that accommodates the drive pulley and the endless belt and is formed with an insertion hole through which the drive pulley can be inserted;
A method for manufacturing a steering device comprising:
a first step of assembling the driven pulley, the ball screw nut, and the bearing to the first housing member;
a second step of causing the first housing member to temporarily hold a jig so that the endless belt is wound between the jig and the driven pulley;
a third step of fastening the first housing member and the second housing member;
a fourth step of removing the jig and inserting the drive pulley into the second housing member from the insertion hole, and arranging the drive pulley inside the endless belt;
has
In the second step, the jig is temporarily held by fitting into the first housing member along a direction parallel to the steering axis;
in the fourth step, taking the jig out of the second housing member from the insertion hole;
A method for manufacturing a steering device. In the second step, at least a portion of the driven pulley is exposed in the axial direction from the first housing member.
A method for manufacturing a steering device according to claim 1 . A steering shaft for steering the steering wheels of a vehicle;
a ball screw nut that is screwed onto the steered shaft through a plurality of balls;
a driven pulley that rotates integrally with the ball screw nut;
a drive pulley rotationally driven by an electric motor;
an endless belt wrapped around the driven pulley and the driving pulley;
a first housing member that accommodates at least a portion of the ball screw nut;
a bearing rotatably supporting the driven pulley and the ball screw nut with respect to the first housing member;
a second housing member that accommodates the drive pulley and the endless belt and is formed with an insertion hole through which the drive pulley can be inserted;
A steering device comprising:
The first housing member includes, on a surface facing the insertion hole, a first holding part for temporarily holding a jig for holding the endless belt around the driven pulley;
The jig includes a second holding part that engages with the first holding part.
Steering device. The first holding part is a recess that is depressed from the front surface and does not penetrate to the back surface, and the second holding part is a convex part that fits into the recess.
Steering device according to claim 3 At least a portion of the driven pulley is exposed from the first housing member before the second housing member is assembled.
Steering device according to claim 3 or 4

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