JP2001278075A - Center take-off type power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent batter of a rack shaft in a center take-off type power steering device. SOLUTION: In the center take-off type power steering device 10, a connecting member 42 for connecting right and left tie rods 41A, 41B to the rack shaft 16 is provided with a slider 44 reciprocating in sliding contact with a window-like part 43 of a housing 11A, and the slider 44 is interference-fitted with interference in the sliding orthogonal direction of the window-like part 43.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a center take-off type power steering device such as an electric power steering device and a hydraulic power steering device.

[0002]

2. Description of the Related Art Generally, in a power steering device,
The rack shaft is supported by the housing so as to be linearly movable, the input shaft is rotatably supported by the housing, the pinion connected to the input shaft is meshed with the rack shaft, and the force generated by the steering assist force generating device is controlled by the rack shaft. And the steering force can be assisted. In the power steering apparatus described in Japanese Patent Application Laid-Open No. H11-222140, a connecting member for connecting left and right tie rods to an intermediate portion of the rack shaft is provided on a window-like portion formed on a side wall of the housing. It is provided to be able to reciprocate. FIG. 8 shows a connecting member 4 for connecting the left and right tie rod mounting members 1 to the rack shaft 3 inside the housing 2. The connecting member 4 is fixed to the rack shaft 3 together with the mounting member 1 by bolts 5. A slider 4A of the connecting member 4 is arranged reciprocally in the window 2A of the housing 2.

[0003]

However, the prior art has the following problems. The rack of the rack shaft meshing with the pinion connected to the input shaft is inclined in the axial direction of the rack shaft. For this reason, when the steering force applied to the input shaft is transmitted from the pinion to the rack shaft, not only the axial thrust but also the rotational force is applied to the rack shaft by the steering force applied by the pinion. Therefore, when the direction of the steering force applied to the input shaft is switched left and right, the direction of the rotational force applied to the rack shaft changes, and the rack shaft rotates in the rotational direction.

When a steering reaction force from a wheel is transmitted to a rack shaft via a tie rod, the axial reaction force acting on the rack shaft rotates the rack shaft due to the engagement between the inclined rack and the pinion. It can be turned in the direction. Also, the rack shaft may roll in the rotation direction by transmitting the vibration force from the wheel to the rack shaft via the tie rod.

As described above, when the rack shaft falls,
Normal engagement between the rack and the pinion is disturbed, and the transmission efficiency of the steering force from the pinion to the rack deteriorates, the durability of the rack shaft and the pinion deteriorates, and abnormal noise may occur around the rack shaft. .

In FIG. 8, when the slider 4A of the connecting member 4 fixed to the rack shaft 3 reciprocates in the window 2A of the housing 2, the slider 4A slides on the window 2A. In the prior art, since the slider 4A is fitted into the window-like portion 2A with a gap, this gap g (see FIG.
In the range of (B)), play occurs, and it is impossible to prevent the rack shaft 3 from falling.

An object of the present invention is to prevent a rack shaft from rolling over in a center take-off type power steering device.

[0008]

According to the first aspect of the present invention, a rack shaft is supported by a housing so as to be linearly movable, an input shaft is rotatably supported by a housing, and a pinion connected to the input shaft is mounted on a rack shaft. And a connecting member for connecting the left and right tie rods to the rack shaft is formed on a side wall of the housing, so that the steering force can be assisted by applying the generated force of the steering assist force generating device to the rack shaft. In a center take-off type power steering device provided reciprocally on a window-shaped portion, the connecting member includes a slider reciprocating in sliding contact with a window-shaped portion of the housing, and the slider is moved in a direction perpendicular to the window-shaped portion. It is designed to be tightly fitted with an interference.

According to a second aspect of the present invention, in the first aspect of the present invention, the slide surface of the slider that is in sliding contact with the window-like portion is made convex.

[0010]

According to the first aspect of the present invention, the following operations are provided. A slider of a connecting member for connecting the left and right tie rods to the rack shaft is tightly fitted to the window-like portion of the housing in a sliding orthogonal direction with a tight allowance. Therefore, the slider of the connecting member fixed to the rack shaft engages with the window-like portion of the housing in the rotation direction of the rack shaft, thereby preventing the slide. As a result, the normal engagement between the rack and the pinion can be secured, so that the steering force transmission efficiency from the pinion to the rack is improved, and the durability of the rack shaft and the pinion is improved,
Generation of abnormal noise around the rack axis can also be prevented.

By adjusting the interference of the connecting member to the slider, even at a low temperature at which the slider contracts,
The amount of the thermal deformation is absorbed by the elastic deformation of the slider, so that the play can be avoided, and the rack shaft can be reliably prevented from rolling.

According to the second aspect of the present invention, the following operations are provided. Since the sliding surface that slides on the window-like portion of the slider is made convex, the contact area between the slider and the window-like portion can be reduced, the sliding resistance can be reduced, and smooth steering can be achieved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partially cutaway front view of a power steering device, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, and FIG. 3 is an enlarged view of a main part of FIG. 4 is a side view of FIG. 2, FIG. 5 is a cross-sectional view taken along the line VV of FIG. 3, FIG. 6 is an enlarged view of a main part of FIG. 5, FIG.
(B) is a cross-sectional view along the line BB, (C) is a cross-sectional view along the line CC, and FIG. 8 is a schematic view showing a conventional example.

As shown in FIGS. 1 and 2, a center take-off type electric power steering apparatus 10 includes a housing 1 fixed to a body frame or the like by a bracket (not shown).
1 (first to third housings 11A to 11C). An output shaft 14 is connected to an input shaft 12 to which a steering wheel is coupled via a torsion bar 13, a pinion 15 is provided on the output shaft 14, and a rack shaft 16 having a rack 16 </ b> A meshed with the pinion 15 is provided. It is supported on the first housing 11A so as to be movable left and right. A steering torque detecting device 17 is provided between the input shaft 12 and the output shaft 14.
Is provided. The input shaft 12 and the output shaft 14 are
It is supported by the housing 11 via A, 14A and 14B.

As shown in FIG. 2, the steering torque detecting device 17 includes two detecting coils 17A and 17B surrounding a cylindrical core 17C engaged with the input shaft 12 and the output shaft 14, respectively.
It is provided on the housing 11C. The core 17C is provided with a vertical groove 17E that engages with the guide pin 17D of the output shaft 14, is movable only in the axial direction, and has a spiral groove 17G that engages with the slider pin 17F of the input shaft 12. As a result, when the steering torque applied to the steering wheel is applied to the input shaft 12 and a relative displacement in the rotational direction occurs between the input shaft 12 and the output shaft 14 due to the elastic torsional deformation of the torsion bar 13, the input shaft 12 Output shaft 1
4 displaces the core 17C in the axial direction, and the detection coil 1 due to the displacement of the core 17C.
The inductance of the detection coils 17A and 17B changes due to magnetic changes around 7A and 17B. That is, when the core 17C moves toward the input shaft 12, the inductance of the detection coil 17A closer to the core 17C increases,
The inductance of the detection coil 17B away from the core 17C decreases, and the change in the inductance enables the detection of the steering torque.

As shown in FIG. 2, a rack guide 19 is built in a cylinder portion 18 provided at a portion of the first housing 11A opposite to the pinion 15 with one end of the rack shaft 16 interposed therebetween. (Bush 19
A) is repelled toward the rack shaft 16 by a spring 21 supported on the back surface by a cap 20 attached to the cylinder portion 18, pressing the rack 16 A of the rack shaft 16 against the pinion 15, and connecting one end of the rack shaft 16. It is slidably supported. The other end of the rack shaft 16 is supported by a bearing 22.

The second housing 11B includes an electric motor 30
(Steering assist force generator). Electric motor 3
A worm gear 31 is connected to the output shaft 0 via a clutch, and a worm wheel 32 meshing with the worm gear 31 is fixed to an intermediate portion of the output shaft 14. The torque generated by the electric motor 30 is applied to the rack shaft 16 through meshing between the worm gear 31 and the worm wheel 32 and meshing between the pinion 15 and the rack 16 </ b> A, and assists a steering force applied to the input shaft 12 by the driver.

However, the power steering device 10
It is a center take-off type, as shown in FIGS.
A connecting member 42 for connecting the left and right tie rods 41A and 41B to an intermediate portion of the rack shaft 16 can reciprocate on a window 43 formed on a side wall of the first housing 11A. As shown in FIG. 7, the connecting member 42 is an assembly of a slider 44 inserted slidably into the window 43 and collars 45, 45 press-fitted into two positions in the longitudinal direction of the slider 44, respectively. .

The left and right tie rods 41A, 41B are provided with mounting portions 46 as shown in FIGS. Mounting part 46
Is formed by press-fitting a mount 48 into a flange 47 formed at the end of each of the tie rods 41A and 41B. The mount 48 includes an inner cylinder 48B and an outer cylinder 48 inside and outside the rubber cylinder 48A.
C is baked. Thereby, the left and right bolts 5
1A and 51B are inserted into each of two longitudinal positions of one mounting plate 52, and are mounted around the housing 11A via the mount 48 and the washer 53 provided on the mounting portion 46 of the tie rods 41A and 41B. Boot holder 5 placed
4 and two through the collar 45 of the connecting member 42, the mounting plate 52,
Mount 48 of tie rods 41A and 41B, washer 53,
Attachment seats 55A, 55B provided with the boot holder 54 and the connecting member 42 at two positions in the longitudinal direction of the rack shaft 16, respectively.
To conclude. One end of the left and right dust boots 56A, 56B is attached to both ends of the boot holder 54, and the other end of the dust boots 56A, 56B is attached to the housing 11A.

At this time, in the power steering device 10, in order to prevent the rack shaft 16 from falling, the slider 44 of the connecting member 42 fastened to the rack shaft 16 as described above is made of urethane resin, plastic resin or the like. The slider 44 is made of an elastic material, and the slider 44 is tightly fitted to the window 43 of the housing 11A (for example, made of an aluminum alloy) with a margin in a direction perpendicular to the sliding direction (FIG. 6). The slider 44 has two slide surfaces 44A, 44A provided at the center between the collars 45, 45 press-fitted at two positions in the longitudinal direction. The slide surfaces 44A, 44A are arc-shaped surfaces projecting outward, and the width of the two slide surfaces 44A, 44A. H is given an interference against the width W of the window 43 (FIG. 4).

Therefore, in the power steering device 10, when signals from the steering torque detecting device 17, the vehicle speed sensor, and the like are input, the power supply to the electric motor 30 is determined by the control device (ECU). The electric motor 30 is driven by an external drive device including a power supply based on the power supply. The rotational torque of the electric motor 30 is controlled by the rack shaft 16 as described above.
And the steering assist force transmitted to the rack shaft 16 is transmitted to the left and right wheels via the left and right tie rods 41A and 41B, and assists the driver's steering force.

Therefore, according to the present embodiment, the following operations are provided. The slider 44 of the connecting member 42 for connecting the left and right tie rods 41A, 41B to the rack shaft 16 is
A is tightly fitted to the window-like portion 43 of FIG. Therefore, the connecting member 42 fixed to the rack shaft 16
The slider 44 engages with the window-like portion 43 of the housing 11A in the rotation direction of the rack shaft 16 to prevent rolling. As a result, normal engagement between the rack 16A and the pinion 15 can be ensured, so that the steering force transmission efficiency from the pinion 15 to the rack 16A is improved, the durability of the rack shaft 16 and the pinion 15 is improved, and the rack shaft 1
The generation of abnormal noise in six turns can also be prevented.

By adjusting the interference of the connecting member 42 to the slider 44, even when the slider 44 contracts at a low temperature, the amount of thermal deformation can be absorbed by the elastic deformation of the slider 44, and the occurrence of the backlash can be avoided. Rack shaft 16
Falling can be reliably prevented.

Since the slide surface 44A of the slider 44 which is in sliding contact with the window 43 is made convex, the contact area between the slider 44 and the window 43 can be reduced to reduce the sliding resistance.
Steering can be smoothly performed.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and the design can be changed within the scope of the present invention. The present invention is also included in the present invention. For example, the present invention is not limited to the electric power steering device, and can be applied to a hydraulic power steering device in which the steering assist force generating device is configured by a hydraulic pump and a power cylinder.

[0026]

As described above, according to the present invention, it is possible to prevent the rack shaft from rolling over in the center take-off type power steering device.

[Brief description of the drawings]

FIG. 1 is a front view showing a power steering apparatus with a part thereof cut away.

FIG. 2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is an enlarged view of a main part of FIG. 1;

FIG. 4 is a side view of FIG. 2;

FIG. 5 is a sectional view taken along line VV of FIG. 3;

FIG. 6 is an enlarged view of a main part of FIG. 5;

FIG. 7 shows a connecting member, (A) is a side view,
(B) is a sectional view along the line BB, and (C) is a sectional view along the line CC.

FIG. 8 is a schematic diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 10 electric power steering device 11, 11A housing 12 input shaft 15 pinion 16 rack shaft 30 electric motor (steering assist force generating device) 41A, 41B tie rod 42 connecting member 43 window 44 slider 44A sliding surface

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshitaka Tsuboi 112-1 Hagadai, Haga-cho, Haga-gun, Tochigi Prefecture F-term in Showa Tochigi Development Center Co., Ltd. 3D033 CA02 JB03

Claims (2)

[Claims] 1. A rack shaft is supported by a housing so as to be linearly movable, an input shaft is rotatably supported by a housing, a pinion connected to the input shaft is meshed with the rack shaft, and a steering assist force generating device is generated. A connecting member for connecting left and right tie rods to the rack shaft by applying force to the rack shaft to assist the steering force;
A center take-off type power steering device provided reciprocally on a window-like portion formed on a side wall of a housing, wherein the connecting member includes a slider which reciprocates by sliding on a window-like portion of the housing. A center take-off type power steering device, which is tightly fitted to a shape portion with a margin in a direction perpendicular to sliding. 2. The center take-off type power steering device according to claim 1, wherein a slide surface which slides on a window-like portion of the slider has a convex shape.