JP2001187579A - Power steering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently maintain the engaged state of a plurality of feed rings on the periphery of a steering shaft to perform stable transmission from a steering assist motor. SOLUTION: The engaging positions a1, a2 of two feed rings R1, R2 out of four feed rings R1-R4 engaged with a thread groove 20 on the outer periphery of a rack shaft 2 being held in a rotating cylinder 10 rotated by transmission from a steering assist motor, are set into radially opposed positions, and the engaging positions a3, a4 of two remaining feed rings R3,R 4 are set into positions radially opposed to each other and circumferentially shifted by a specified angle in relation to the first set of engaging positions a1, a2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering system in which the rotation of a steering assist motor is converted into a linear motion and transmitted to a steering shaft, and the steering shaft is moved in the axial direction to assist the steering. It relates to a taking device.

[0002]

2. Description of the Related Art An electric power steering apparatus (power steering apparatus) configured to drive an electric motor for assisting steering according to a steering operation and to transmit the rotational force of the motor to a steering mechanism to assist the steering. ) Has been put to practical use. Most power steering devices of this type are provided with a steering assist motor around a steering shaft (rack shaft in a rack and pinion steering mechanism) connected to steering wheels (generally, left and right front wheels). , The torque of the motor is directly transmitted to the steering shaft, and the steering shaft is moved in the axial direction to assist the steering.

In order to realize such a configuration, a motion conversion device for converting the rotation of the motor into the movement of the steering shaft in the axial length direction is required.
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. H10-209, a motion conversion device using a ball screw is used.

In this motion conversion device, a thread groove is formed on an outer periphery of a steering shaft, and a ball nut screwed into the thread groove via a number of balls is provided inside a housing supporting the steering shaft. Directional movement is constrained, the ball nut is rotated by transmitting the torque of a steering assist motor to the ball nut, and the screw groove is formed using the screwing of the screw groove accompanying this rotation. The structure is such that the steering shaft is moved in the axial direction, and high transmission efficiency can be obtained.In addition, the limited space around the steering shaft can be made compact by including a steering assist motor, and It can meet the demand for reducing installation space.

However, in such a ball screw type motion conversion device, high precision is required for forming a thread groove on the outer periphery of the steering shaft, and a screw between the steering shaft and the ball nut via the ball is required. It takes time to adjust the matching state,
There is a problem that a large number of steps are required for processing and assembly. In addition, during the operation, there is a problem that a plurality of balls rolling along the thread groove collide with each other, generating an unpleasant collision sound.

[0006] Under such circumstances, in the electric power steering device, high transmission efficiency equivalent to that of a ball screw type motion conversion device is obtained in order to transmit the rotation of the steering assist motor to the steering shaft. Therefore, in addition to being able to be configured compactly, there is a strong demand for a motion conversion device that has a small operation sound and a simple configuration.

[0007] As one of the motion conversion devices that can meet such a longing, there is a motion conversion device disclosed in Japanese Patent Application Laid-Open No. 59-9351. FIG. 7 is a perspective view schematically showing the configuration of the motion conversion device.

In this motion conversion device, two places separated by an appropriate length in the axial direction are supported by bearings B ₁ and B ₂ , and a screw shaft S movably supported in the axial direction and a screw shaft S A rotating cylinder 10 which coaxially surrounds the outer periphery of the screw shaft S, and which is eccentrically held inside the holding cylinder 10 by tilting the axis thereof inside the holding cylinder 10, and which is circumferentially inserted into a thread groove on the outer periphery of the screw shaft S. It is provided with a plurality (three in the figure) of feed rings R _{1 to} R ₃ which are engaged at different places. In this figure, the screw shaft S
Omitting the inclination of the feeding ring R ₁ to R ₃ for the axis,
Also, the screw groove on the outer periphery of the screw shaft S is omitted. Rolling bearings such as ball bearings and roller bearings are used as the feed rings R _{1 to} R ₃ , and the engagement with the thread groove on the outer periphery of the screw shaft S is performed by an engagement projection provided on the inner peripheral surface of the inner ring. Has been made through.

According to this configuration, when the rotary cylinder 10 rotates around the axis, the three feed rings R _{1 to} R ₃ held by the rotary cylinder 10 are connected to the thread groove on the outer periphery of the screw shaft S. , And the screw shaft S is connected to each of the feed rings R ₁ -R
It is pressed by the axial component of the frictional force acting on the engaging portion ₃ and is moved in the axial direction. Therefore, the rotating cylinder
The power steering device described above can be configured by rotating the screw 10 by a steering assist motor and using the screw shaft S as a steering shaft for steering.

At this time, since the rolling of each of the feed rings R _{1 to} R ₃ occurs through a rolling element such as a ball or a roller interposed between the inner ring and the outer ring, the above-described motion conversion is performed by a ball screw type. In addition to being performed at the same transmission efficiency as the motion conversion device, the rolling elements are held between the inner ring and the outer ring without changing the mutual position, and the generation of sound due to the collision between the rolling elements is reduced. A quiet operation is possible. The rotary cylinder 10
Is a simple configuration in which only was holding the ring R ₁ to R ₃ is sent to the inside (bearing), significant simplification of the construction is achieved as compared to the motion converter of the ball screw type.

[0011]

In [0008] Well above-described motion converter, engaged position a ₁ ~a ₃ of the three feed rings R ₁ to R ₃ on the peripheral surface of the screw shaft S is 2 setting the engagement position a _1, a ₃ of number of feed ring R _1, R _3, and the engagement position a ₂ of the remaining one of the feed rings R _2, at a position opposed to the radial direction of the screw shaft S And the screw shaft S is a ₁ ,
By the a ₃ and a ₂ are as supported from the opposite position. According to this configuration, for example, the feed rings R ₁ and R
_When these are pressed against the screw shaft S from the side of the respective engagement positions a ₁ and a ₃ in order to strengthen the engagement of the screw shaft ₃ , the bending of the screw shaft S due to this pressing is caused at the engagement position a ₂ . results to be bound by the feed ring R ₂ which engage, each feed rings R ₁ to R ₃ can be firmly engaged.

However, when such a motion conversion device is used in the above-described power steering device, the steering shaft serving as the screw shaft S has a reaction force from steering wheels connected to both ends thereof.
Since the external force is applied from various directions, the feed ring R ₁ engagement state of the to R ₃ are impaired, the transmission to the steering shaft from the steering assisting motor has a problem that it becomes impossible to stably.

FIG. 8 is an explanatory view of this problem. The engagement position a ₁ (and a ₃ ) of the feed ring R ₁ (and R ₃ ) is shown in FIG.
When the engaging position a ₂ of the feed ring R _2, is shown by respective triangles on axial section of the screw shaft S. With respect to such a screw shaft S, as shown by a white arrow in the drawing, the a ₁
When the pressing force P in a direction orthogonal to a straight line connecting the a ₂ (a ₁ -a ₂ lines) were added and, as shown by two-dot chain line in the figure, the screw in the direction of action of the pressing force P feed rings R ₁ in the axial S bends displaced, the engagement position a _1, a _2,
So that the engagement of R ₂ may be impaired.

In the above-described power steering apparatus, the pressing force P in the direction orthogonal to the line a ₁ -a ₂ accompanied by such bending displacement is steadily determined as a component of the external force applied to the steering shaft as the screw shaft S. The above-described transmission failure may always occur.

The present invention has been made in view of such circumstances, and it is possible to maintain the engagement state of the feed ring satisfactorily even when external force acts on the steering shaft from various directions. It is an object of the present invention to provide a power steering device capable of stably transmitting power from a motor for use to a steering shaft.

[0016]

SUMMARY OF THE INVENTION A power steering apparatus according to the present invention includes a steering shaft supported movably in an axial direction and having a thread groove formed on an outer peripheral surface thereof, and a coaxial outside of the steering shaft. A rotatable cylinder rotatably supported above and rotated by transmission from a steering assist motor, and an eccentric holding having an axis inclined at an angle substantially equal to the lead angle of the thread groove inside the rotatable cylinder. A feed ring engaged with the thread groove at one location in the circumferential direction, and the rotation of the rotary cylinder is converted into the movement of the steering shaft by the rolling of the feed ring guided by the thread groove. In a power steering apparatus configured to assist steering caused by this movement, two or more feed rings each having an engagement position with a thread groove on the outer periphery of the steering shaft set at a position facing the radial direction are provided. The first and second ring sets including 1 ring sets of the engaging position and the second ring set of engagement position, characterized in that is set to be shifted in the circumferential direction of the steering shaft.

In the present invention, for example, four feed rings are divided into two sets of two, and the engagement position between the two feed rings of the first set and the steering shaft is set to a position facing the radial direction. The engagement position between the two feed rings of the second set and the steering shaft is shifted by a predetermined angle in the same direction in the circumferential direction of the steering shaft with respect to the two sets of the first set, Within the set, they are set at positions facing each other in the radial direction. As a result, the steering shaft is supported at different circumferential positions by two ring sets each including two feed rings that engage at positions opposed to each other in the radial direction. Within
The pressing of one feed ring reinforces the engagement of the other feed ring, and the displacement of the steering shaft due to the acting force in the direction orthogonal to the engagement position of one set of feed rings is suppressed by the other set of feed rings. Thus, the engagement state of all the feed rings is favorably maintained.

In the power steering apparatus according to the second invention of the present invention, the two feed rings, each of which has an engagement position set at one half in one side in the axial section of the steering shaft, are provided. It is characterized in that at least one feed ring whose engagement position is set in the other half is sandwiched therebetween.

In the present invention, the feed ring engaged with one half of the steering shaft and the feed ring engaged with the other half of the same in the axial cross section of the steering shaft are located on the same side in the axial length direction of the steering shaft. As a result, the rotational moment does not act in the axial direction of the steering shaft due to the pressing force applied to the respective engagement positions.

Further, in the power steering apparatus according to a third aspect of the present invention, the feed ring includes a rolling bearing having an outer ring fitted and fixed to the rotary cylinder and an inner ring engaged with the screw groove. It is characterized by having been done.

In the present invention, a rolling device such as a ball bearing and a roller bearing is used as a feed ring to be engaged with the steering shaft, and a power steering device capable of quiet operation with low operation noise is simply constructed.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a partially cutaway front view showing a configuration of a main part of a power steering device according to the present invention, in which a rotation of a motor 3 for assisting steering is transmitted through a motion conversion device 1 to a rack shaft 2 serving as a steering shaft. And assists the steering by moving the rack shaft 2 in the axial direction.

The rack shaft 2 is supported inside a cylindrical rack housing 20 so as to be movable in the axial direction, and extends in the left-right direction of a vehicle body (not shown). Both ends of the protruding rack shaft 2 are connected to unillustrated steering wheels (generally left and right front wheels) via respective tie rods.

A pinion housing 21 is provided in the middle of the rack housing 20 so as to intersect the axis with the pinion housing 21. Inside the pinion housing 21, a pinion shaft 22 is rotatable around the axis. It is supported. In FIG. 1, the pinion shaft 22 has only a projecting end projecting upward from the pinion housing 21, and is connected to a steering wheel (steering wheel) (not shown) via the projecting end, and is operated in accordance with the operation of the steering wheel for steering. It is designed to rotate around an axis.

A pinion (not shown) is integrally formed below the pinion shaft 22 extending inside the pinion housing 21. Further, rack teeth 23 are formed on the rack shaft 2 supported in the rack housing 20 over an appropriate length including a crossing position with the pinion housing 21, and mesh with the pinion below the pinion shaft 22. It is. Thus, the rotation of the pinion shaft 22 accompanying the operation of the steering wheel is converted into the movement of the rack shaft 2 in the axial length direction by the meshing of the pinion and the rack teeth 23, and the rotation of the rack shaft 2 in the rack housing 20 is further performed. The movement is transmitted to left and right steering wheels via the tie rods, and a rack and pinion type steering mechanism is configured in which these wheels are steered according to the operation of the steering wheel.

The steering assist motor 3 for assisting the steering performed as described above has a cylindrical shape integrally formed by expanding the middle part of the rack housing 20 surrounding the rack shaft 2 over a suitable length. A motor housing 30 having a stator 31 fixed to the inner peripheral surface of the motor housing 30 and a rotor 32 coaxially arranged inside the stator 31;
It is configured as a phase brushless motor.

The rotor 32 is constituted by holding a magnetic pole 33 opposed to the outer periphery of a cylinder having an inner diameter larger than the outer diameter of the rack shaft 2 with a small gap on the inner surface of the stator 31. A pair of left and right ball bearings 34, 35 are rotatably supported around the axis of the motor housing 30, that is, coaxially with the rack shaft 2, and rotate in both forward and reverse directions in accordance with energization of the stator 31. It is made to do.

The rotation of the motor 3 generated as described above is converted into the movement of the rack shaft 2 in the axial direction by the operation of the movement conversion device 1 provided on one side of the rotor 32 as a rotating member and transmitted. It is so. FIG. 2 is an enlarged cross-sectional view of the vicinity of a component of the motion conversion device 1.

As shown in FIG.
And four feed rings R held inside the rotary cylinder 10.
And ₁ to R _4, is constituted by a screw groove 11 formed on the outer periphery of the rack shaft 2 in order to them engaged.
The rotary cylinder 10 is formed integrally with the middle part as an inner ring.
The point contact ball bearing 13 is rotatably supported by an extension of the motor housing 30 to the same side, and a connecting bracket 36 (see FIG. 1) at one end of the rotor 32 (supporting side of the ball bearing 35). And is coaxially connected to the rack shaft 2 in accordance with the rotation of the motor 3.

The feed rings R _{1 to} R held by the rotary cylinder 10
Reference numeral ₄ denotes a ball bearing for holding a number of balls between the outer ring and the inner ring. The ball bearing has an inner diameter larger than the outer diameter of the rack shaft 2 inserted therein. On the other hand, the eccentricity is maintained by tilting the axis. Also thread groove 11
Has a semi-circular cross section, over a predetermined length range including an inner portion of the rotary cylinder 10 is formed with a predetermined lead angle, an inner ring of each feed rings R ₁ to R ₄ An engaging projection having a semicircular cross section corresponding to the screw groove 11 on the outer periphery of the rack shaft 2 is provided on the inner peripheral surface of the rack shaft 2.

The inclination angles of the axes of the feed rings R _{1 to} R ₄ are equal to the lead angles of the thread grooves 11, and these are the circumferential positions at which the respective inclinations coincide with the inclination of the thread grooves 11. , The screw groove 11 is engaged via the engaging protrusion. Figure 3 is an operation explanatory view of the motion conversion apparatus 1, engagement between the rack shaft 2 and the single feed ring R ₁ is shown. Feeding ring R ₁ comprising using as illustrated ball bearing is partially fitted to the outer ring to the rotating cylinder 10 depicted, is held with a slope equal to the lead angle of the screw grooves 11, circumferential to the inner surface The provided engaging projection having a semicircular cross section is engaged with the screw groove 11 at a position where the inclination thereof coincides (a ₁ in the drawing).

According to this configuration, when the rotary cylinder 10 rotates around the axis, the feed ring R held by the rotary cylinder 10
₁ rolls while maintaining engagement with the screw groove 11, the rack shaft 2 by the rolling frictional force F along the thread groove 11 is applied to the engagement position a _1, the rack shaft 2 Is the frictional force F
Is pressed by the axial component force F ₁ of, as indicated by outline arrow in the figure, the direction of the pressing, i.e., so that the moved in the axial direction. The direction of this movement is determined according to the direction of rotation of the rotary cylinder 10, and the rotational motion of the rotary cylinder 10 in both the forward and reverse directions is converted to the linear motion of the rack shaft 2.

In order to stably perform the above-mentioned motion conversion, the four feed rings R _{1 to} R ₄ held by the rotary cylinder 10 are required.
It is important that each of them always maintain a good engagement state.
In the power steering device according to the present invention, the engagement positions a ₁ of the respective feed rings R _{1 to} R ₄ on the outer peripheral surface of the rack shaft 2.
~a ₄ is Yes set to as follows, and to keep a good engagement with the setting.

FIG. 4 is a perspective view showing the relationship between the engagement positions of the feed rings R _{1 to} R ₄ on the circumference of the rack shaft 2. In this figure, the rack shaft 2 is assumed to correspond to the screw shaft S of the motion conversion device shown in FIG.
The position is shown supported by bearings B ₁ and B ₂ , and each feed ring R _{1 to} R ₄ is shown in the same manner as in FIG. The illustration of the inclination of the rings R _{1 to} R ₄ and the illustration of the screw groove 11 formed on the outer periphery of the rack shaft 2 are omitted.

As shown in FIG. 4, four feed rings R ₁ -R
₄ is a first set of two feed rings R ₁ and R ₂ arranged on one side, and the other two feed rings R ₃ and R ₄ arranged on the other side.
As the second set, the engagement positions a ₁ , a ₂ of the first set of feed rings R ₁ , R ₂ are set such that they are opposed to each other in the radial direction of the rack shaft 2. The engagement positions a ₃ , a ₄ of the second set of feed rings R ₃ , R ₄ are located at positions opposed to each other in the radial direction of the rack shaft 2 between them, and the first set of feed rings R _1, R ₁ , R ₂ engagement position a ₁ ,
For a _2, it is set such that the position was shifted in the circumferential direction of the rack shaft 2.

FIG. 5 is an explanatory view of the setting state of the engagement position as described above. In the drawing, the four feed rings R ₁ to R ₁ are shown.
The engagement positions a _{1 to} a _{4 of} R ₄ are indicated by triangles on the circumference of the rack shaft 2 whose axial cross section is shown, respectively.
The engagement positions a ₁ and a ₂ of the feed rings R ₁ and R ₂ of
The engagement positions a ₃ , a _{4 of} the second set of feed rings R ₃ , R ₄ which are located at positions opposed to the rack shaft 2 in the radial direction and are shifted from the rack shaft 2 by a predetermined angle θ are also in the radial direction. It is in the position facing.

[0037] in FIG. 2, the engaging position a ₁ ~a ₄ of each feed rings R ₁ to R ₄ are, by ○ those on the front side of the figure, those on the back side, respectively illustrated by ● It is. Engagement positions a ₁ , a 1 of the first set of feed rings R ₁ , R _2
2 is set at a position in which one is on the front side and the other is on the back side and is opposed in the radial direction, and the engagement positions a ₃ and a _{3 of} the second pair of feed rings R ₃ and R ₄ are set. Similarly, ₄
One is on the front side, the other is on the back side, and is set at a position facing the radial direction. Further, the engagement positions a ₃ , a ₄ of the second set are the corresponding engagement positions of the first set. Joint position a ₂ , a
It is clear that the setting is made so as to be shifted in the same circumferential direction with respect to ₁ .

By setting the engagement positions a _{1 to} a ₄ as described above, the rack shaft 2 is set to have the same radius as the first pair of feed rings R ₁ and R ₂ engaged at the positions opposed in the radial direction. The second pair of feed rings R ₃ , R ₄ engaged with the positions facing each other in the direction makes the state supported at four different positions in the circumferential direction. According to this configuration, in order to strengthen the engagement of _one feed ring R ₁ of the first set, the feed ring R _{1 is used.}
Is pressed against the rack shaft 2 from the side of the engagement position a ₁ ,
The bending of the rack shaft 2 due to this pressing is restrained by the other feed ring R ₂ of the same set, and both feed rings R ₁ , R ₂
Can be firmly engaged. Such engagement reinforcement is similarly applied to the second set of feed rings R ₃ and R ₄ , and the engagement state of all the feed rings R _{1 to} R ₄ can be set well in the assembly stage. .

On the other hand, in the state of use of the motion conversion device 1 in which the feed rings R _{1 to} R ₄ are engaged as described above, the rack shaft 2 receives an external force such as a road surface reaction force applied to the traveling wheels as described above. Acting as a component of this external force, as shown by the white arrow in FIG. 5, with respect to a straight line connecting the engagement positions a ₁ and a ₂ of the first set of feed rings R ₁ and R ₂ . Although there is the pressing force P ₁ direction is applied perpendicular, in the motion conversion apparatus 1 according to the present invention, one of the feed ring to the second set of R ₃
The engagement position a _3, because is set to the direction facing the pressing force P _1, deflection displacement of the pressing force P ₁ of the working direction of the rack shaft 2 is suppressed by the feed ring R ₃ , The engagement of the first set of feed rings R ₁ , R ₂ is well maintained without any loss. The pressing force P
_With respect to the pressing force applied from the direction opposite to the direction ₁ , the other feed ring R _{4 of} the second set acts to suppress the bending displacement of the rack shaft 2, and maintains the engagement state similarly well. Can be.

Further, when the pressing force P ₂ in a direction perpendicular to the straight line connecting the second set of feed ring R _3, engagement of R ₄ position a _3, a ₄ are applied, the direction Rack shaft 2
Is suppressed by _one feed ring (R _{1 in the} figure) of the _first set, and the second set of feed rings R ₃ ,
Engagement of R ₄ is maintained without being impaired. Also in this case, the other feed ring (R _{2 in the} figure) of the first set suppresses the displacement of the rack shaft 2 against the pressing force acting from the direction opposite to the pressing force P ₂ . And the engagement state can be maintained satisfactorily similarly.

As described above, in the power steering apparatus according to the present invention, four feed rings R _{1 to} R with respect to the rack shaft 2 are provided.
₄ is maintained without being impaired by the pressing forces applied to the rack shaft 2 in various directions, so that the motion conversion from the rotary motion of the rotary cylinder 10 to the linear motion of the rack shaft 2 is performed. Can be performed stably. The feed rings R _{1 to} R ₄ are ball bearings provided with a large number of balls between an outer ring and an inner ring. The feed rings R _{1 to} R ₄ have a simple configuration fixed by being fitted into the rotary cylinder 10 as described above. Since they roll without changing their mutual positions and there is no danger of collision, the sound produced by the above-mentioned operation is small and a quiet operation is possible.

By the operation of the motion conversion device 1 described above, the rotation of the steering assist motor 3 is converted into the movement of the rack shaft 2 in the axial direction inside the rack housing 20, and this movement is converted into a tie rod (not shown). The steering is performed to the left and right steering wheels via the steering wheel, and the steering performed as described above in accordance with the operation of the steering wheel is assisted by the generated force of the motor 3. At this time, radial loads are generated on the rack shaft 2 in various directions. In the power steering device according to the present invention, four feed rings R ₁ provided in the motion conversion device 1 are provided.
To R engaged position a ₁ ~a ₄ of ₄ Yes set as described above, these engagement of the feed ring R ₁ to R ₄ is satisfactorily without also impaired under the action of the radial load Since the steering assist is maintained, the steering assist described above can be favorably performed.

Note that the deviation angle θ between the second set of engagement positions a ₃ and a ₄ with respect to the _first set of engagement positions a ₁ and a ₂ is 0.
The angle can be set as appropriate within the angle range of 90 ° to 90 °, but when θ = 0 °, the engagement positions of both sets are one in the circumferential direction as in the motion conversion device shown in FIGS. However, the displacement of the rack shaft 2 with respect to the pressing force in the direction orthogonal to these cannot be suppressed, and when θ = 90 °, the acting force on the engagement position of one set is reduced by the engagement force of the other set. Acts to weaken. Therefore, it is preferable that the deviation angle θ is set near 45 ° (about ± 10 °) which is an intermediate value between 0 ° and 90 °.

[0044] In the above embodiments, the feed rings R ₁ and R ₂ and the first set, there is a feed ring R ₃ and R ₄ as the second set, the feed ring R ₁ to R ₄ The grouping is not limited to this, and for example, the feed rings R ₁ and R
₄ may be changed to a first set, and the feed rings R ₂ and R ₃ may be changed to a second set.

However, even in this case, each feed ring R
_{1 to} R ₄ are two feed rings (in FIG. 3, feed rings R ₁ and R ₄ ) each of which has an engagement position set at one half in the axial cross section of the rack shaft 2. It is necessary to arrange at least one feed ring (the feed rings R ₂ and R ₃ in FIG. 1) between which the engagement position is set in the other half. This is because, in FIG. 3, when the feed rings R ₁ and R ₂ are engaged with one half of the rack shaft 2 and the feed rings R ₃ and R ₄ are engaged with the other half, The pressing force applied to the engagement position of the feed rings R _{1 to} R ₄ generates a rotational moment in the axial direction of the rack shaft 2, and the engagement state of each of the feed rings R _{1 to} R ₄ may not be maintained properly. This is because

Further, in the above embodiment, the configuration including the four feed rings R _{1 to} R ₄ has been described.
The power steering device according to the present invention may be configured to include five or more feed rings. In this case, the feed rings provided in excess of four are assembled into one of the two sets, and the engagement position is set so as to be circumferentially aligned with one of the two feed rings in the set. And said 2
Any of the sets does not belong, and the engagement position may be set separately from these.

FIG. 6 is a perspective view showing an example of setting an engagement position when _six feed rings R _{1 to} R ₆ are provided. The six feed rings R _{1 to} R ₆ are divided into two sets, and the engagement positions a ₁ , a ₂ , a ₃ of the first set of three R ₁ , R ₂ , R ₃ are determined by:
a _1, a ₃ and a ₂ are set so as to oppose each other in the radial direction, and the engagement position a of the second set of three R ₄ , R ₅ , R _6
4, a _5, a _6, together with the a a ₄ and a ₆ and a ₅ set to face in the radial direction, these are the first set of engagement positions a _1, a _2, a ₃ The positions are set so as to be shifted by the same angle in the circumferential direction with respect to each other. In this figure, the illustration of a rotary cylinder holding the feed rings R _{1 to} R ₆ is omitted.

Further, in the above embodiment, an example of application to a rack and pinion type power steering device for transmitting the rotation of the steering assist motor 3 to the rack shaft 2 to assist the steering has been described. Needless to say, the present invention can be applied to various types of power steering devices configured to transmit the rotation of a steering assist motor to a steering shaft that performs steering by moving in the axial direction.

[0049]

As described above in detail, in the power steering apparatus according to the present invention, the feed ring which is held by the rotating cylinder which is rotated by the transmission from the steering assist motor and engages with the thread groove on the outer periphery of the steering shaft. Are divided into two sets each including two or more, and the engagement positions of these feed rings with the steering shaft are set at positions facing the radial direction in each set, and the steering shaft is set between the two sets. , The engagement state of the feed ring with the steering shaft can be kept good against external forces applied in various directions, and the transmission from the steering assist motor to the steering shaft can be made high. It is possible to perform the operation stably with efficiency.

In the power steering apparatus according to the second aspect of the present invention, an engagement position is similarly set on the other half of the steering shaft between the two feed rings whose engagement positions are set on one half of the steering shaft. And a feed ring engaged with one half and a feed ring engaged with the other half.
Since it was arranged not to be concentrated on the same side in the axial direction of the steering shaft, no rotational moment was generated in the axial direction of the steering shaft due to the pressing force applied to the engagement position of each feed ring,
The transmission from the steering assisting motor to the steering shaft can be performed stably without a favorable engagement state being impaired.

Further, in the power steering apparatus according to the third aspect of the present invention, since a rolling bearing is used as the feed ring engaged with the steering shaft, a noise generated when the steering assist motor is transmitted to the steering shaft is suppressed. The present invention has an excellent effect, for example, it is possible to quietly transmit power with high efficiency.

[Brief description of the drawings]

FIG. 1 is a partially broken front view showing a configuration of a main part of a power steering device according to the present invention.

FIG. 2 is an enlarged sectional view of the vicinity of a component of the motion conversion device.

FIG. 3 is an operation explanatory diagram of the motion conversion device.

FIG. 4 is a perspective view showing an engagement relationship of a feed ring with a rack shaft.

FIG. 5 is an explanatory view of an engagement position of a feed ring.

FIG. 6 is a perspective view showing an example of setting an engagement position when six feed rings are provided.

FIG. 7 is a perspective view schematically showing a configuration of a conventional motion conversion device used in a power steering device.

FIG. 8 is an explanatory diagram of a problem of the conventional motion conversion device.

[Explanation of symbols]

1 motion converter 2 rack shaft 3 motor 10 rotating cylinder 11 the thread groove a ₁ ~a ₆ engaged position R ₁ to R ₆ feed ring

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Osamu Sano 3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka F-term (reference) 3D033 CA04

Claims (3)

[Claims] 1. A steering assist motor movably supported in an axial direction and having a thread groove formed on an outer peripheral surface thereof, and a motor for steering assistance supported coaxially and rotatably outside the steering shaft. A rotary cylinder that rotates by transmission from the rotary cylinder, and is held eccentrically inside the rotary cylinder with an axis inclined at an angle substantially equal to the lead angle of the screw groove, and is held eccentrically at one location in the circumferential direction. And a feed ring that engages with the feed ring, and converts the rotation of the rotary cylinder into movement of the steering shaft by rolling the feed ring with the screw groove as a guide, and assists in steering caused by this movement. A steering device, comprising first and second ring sets each including at least two feed rings each of which is set at a position where an engagement with a thread groove on the outer periphery of the steering shaft is radially opposed to each other; The engagement position of the first ring set and the engagement position of the second ring set And if the position is, the power steering apparatus, characterized in that is set to be shifted in the circumferential direction of the steering shaft. 2. A feed ring having an engagement position set on one side half in an axial cross section of the steering shaft, and an engagement position set on the other half between them. At least one
2. The power steering device according to claim 1, wherein said plurality of feed rings are arranged between said feed rings. 3. The power supply according to claim 1, wherein the feed ring is configured by a rolling bearing including an outer ring fitted and fixed to the rotary cylinder and an inner ring engaged with the screw groove. Steering gear.