JP2000046136A - Motion converter device and power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motion converter device of simple constitution capable of surely converting a motion between a rotary motion and a linear motion by realizing firm engagement between a feed ring held to a rotary cylinder and a moving shaft. SOLUTION: Two in both sides of three feed rings 11, 11, 11 held to a rotary cylinder 10 are fitted to respective mounting holes 14, 15 formed by having a circular opening in both end faces of the rotary cylinder 10, to be fixed with coming off locked by a lock ring 16. The feed ring 11 in the center is pressed in a mounting part formed by having a slit-shaped opening 17a in a peripheral wall in a concerned position of the rotary cylinder 10, to be engaged with a screw groove 12 in the external periphery of a rack shaft (moving shaft) 2 inserted on the axial center of the rotary cylinder 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motion conversion device used for converting a motion from a rotational motion to a linear motion or from a linear motion to a rotary motion, and a power steering device using the device.

[0002]

2. Description of the Related Art An electric power steering system (power steering) in which a steering assist electric motor is driven in accordance with a steering operation, and the rotational force of the motor is transmitted to a steering mechanism to perform the steering assist. The device 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, it is necessary to provide a motion conversion device for converting the rotation of the motor into the movement of the steering shaft in the axial direction. As disclosed in Japanese Patent No. 191468, a motion conversion device using a ball screw is widely used.

[0004] In this motion conversion device, while a thread groove is formed on the outer periphery of a steering shaft, a ball nut screwed into the thread groove via a large number of balls is axially provided inside a housing supporting the steering shaft in the axial direction. The ball nut is rotated by transmitting the torque of a steering assist motor to the ball nut, and utilizing the screw advance of the screw groove accompanying this rotation, the steering in which the screw groove is formed In this configuration, the shaft is moved in the axial direction.

[0005] In such a motion conversion device, since the motion conversion from the rotation of the ball nut to the axial movement of the steering shaft is performed with the rolling of the ball interposed therebetween, high transmission efficiency can be obtained. In addition, a limited space around the steering shaft can be made compact by including a steering assist motor, and can meet the demand for reducing the installation space.

However, the above-described ball screw type motion conversion device has a problem that a high precision is required for forming a thread groove on the outer periphery of the steering shaft and a large number of processing steps are required. A great deal of effort is required to adjust the screwing state via the ball between the steps, and there is a problem that the number of assembling steps is increased.

[0007] Also, a number of balls screwed into the screw groove are
It is configured to be circulated by a circulation mechanism attached to the ball nut, and there is a problem that the configuration of the ball nut is complicated.Furthermore, the collision sound of each ball is caused by the circulation in the circulation mechanism. Inevitably occur,
There is a problem that the driver hears the collision sound as an unpleasant noise.

Under such circumstances, the electric power steering apparatus can solve the above-mentioned problem in the ball screw type motion conversion apparatus in order to transmit the rotation of the steering assist motor to the steering shaft. At the same time, there is a strong demand for a novel motion conversion device that can achieve high transmission efficiency equivalent to that of a ball screw type motion conversion device and can be configured compactly.

As a motion conversion device that can meet such a longing, there is, for example, a motion conversion device disclosed in Japanese Patent Publication No. 59-12898. The apparatus includes a moving shaft movably supported in an axial direction, a rotating cylinder rotatably supported around the axis and coaxially surrounding the outside of the moving shaft, and an eccentric inside the rotating cylinder. It is provided with a plurality of feed rings in which a held and rotatable inner ring is engaged with the circumferential surface of the moving shaft at one position in the circumferential direction. As the feed ring, a rolling bearing having a number of rolling elements such as balls and rollers between an inner ring and an outer ring having an inner diameter sufficiently larger than the outer diameter of the moving shaft is used.

In Japanese Patent Application Laid-Open No. 59-9351, a screw groove is formed on the outer peripheral surface of a moving shaft, and an engaging projection provided around an inner ring of a feed ring is engaged with the screw groove. A similar motion conversion device is disclosed, in which engagement of the motion conversion device is enhanced.

In these motion conversion devices, when the rotating cylinder rotates around the axis, the feed ring held by the rotating cylinder rotates while maintaining the engagement between the inner ring and the moving shaft, and the moving shaft is The shaft is moved in the axial direction by the action of the axial component force at the engagement portion with the inner ring, and the rotation of the rotary cylinder is converted into the movement of the moving shaft in the axial direction.

At this time, since the rolling of the feed ring occurs through a rolling element such as a ball and a roller interposed between the inner ring and the outer ring, the above-described motion conversion is substantially equivalent to a ball screw type motion conversion device. Transmission efficiency. Further, since these rolling elements are held between the inner ring and the outer ring without changing their positions, collision between the rolling elements does not occur, and quietness can be improved. Further, the rotary cylinder has a simple configuration in which a plurality of feed rings (bearings) are held inside the rotary cylinder, and the configuration is greatly simplified as compared with a ball screw type motion conversion device.

[0013]

However, even in the motion converting apparatus constructed as described above, in order to perform a good motion converting operation, the engagement state between the feed ring and the moving shaft is adjusted. Is essential.

In the motion conversion device disclosed in Japanese Patent Publication No. 59-12898, a plurality of feed rings 5 (only one is shown)
As shown in FIG. 8, each of the mounting holes 60 has a width corresponding to the outer diameter of the feed ring 5 and is inserted into a corresponding one of the mounting holes 60 at one position. The block-shaped pressing member 61 inserted from above is brought into contact with the same half of the outer ring, and the pressing member 61 is pulled out of the mounting hole 60 from the cylindrical spring. A mounting mode is adopted in which the inner ring of the feed ring 5 is engaged with the moving shaft 7 inside the abutting position of each pressing member 61 by being collectively restrained by 62.

In this configuration, a plurality of feed rings 5
Is determined by the precision of the dimension (X dimension in the figure) between the inner and outer surfaces of each of the pressing members 61. When the engagement state is to be adjusted, the feed ring 5
A pressing member 61 having an inner surface corresponding to the outer shape of the rotary cylinder 6 and an outer surface corresponding to the outer shape of the rotary cylinder 6 and having an irregular cross section as shown in the figure.
Dimensional adjustment is required, and there is a problem that a large number of man-hours are required.

Further, since the engaging strength between the feed ring 5 and the moving shaft 7 depends on the spring force of the spring 62 elastically contacting the outer surface of the pressing member 61, it is difficult to obtain a sufficient engaging strength. Rotating cylinder 6 and moving shaft 7
There is a problem that it is difficult to apply to an application that requires transmission of a large force.

[0017] Enhancement of the engagement can be improved by forming a thread groove on the outer peripheral surface of the moving shaft as disclosed in the above-mentioned JP-A-59-9351. In order to obtain a proper engagement state between the feed ring and the moving shaft, it is necessary to improve the processing and assembling accuracy of each member, including dimensional adjustment of the spacer abutting on one side of the feed ring. There is a problem that it requires a lot of man-hours.

The present invention has been made in view of such circumstances, and it is easy to adjust an engagement state in an assembled state, and a strong connection between a feed ring held by a rotary cylinder and a moving shaft is provided. A motion conversion device having a simple configuration capable of reliably realizing the engagement and reliably performing the motion conversion from the rotary motion of the rotary cylinder to the linear motion of the moving shaft, or the reverse motion conversion, and the same. It is an object of the present invention to provide a power steering device using the same.

[0019]

According to a first aspect of the present invention, there is provided a motion conversion device which is supported movably in an axial direction and has a threaded groove formed on an outer peripheral surface thereof, and a movement shaft around the axis. A rotatable cylinder rotatably supported and coaxially surrounding the outside of the moving shaft, having an axis inclined at an angle substantially equal to the lead angle of the screw groove, eccentrically held inside the rotatable cylinder, A feed ring in which an inner ring rotatable with respect to the rotary cylinder is engaged with the screw groove at one location in a circumferential direction, and the rotation of the feed ring guided by the screw groove causes the rotation. In a motion conversion device configured to convert the rotation of a cylinder into movement of the moving shaft or the movement of the moving shaft into rotation of the rotating cylinder, the feed ring includes three feed rings in an axial direction of the rotating cylinder. The two feed rings on both sides are The center feed ring has a slit-shaped opening corresponding to these side shapes in each of the different mounting portions formed on both end surfaces of the rotary cylinder having a circular opening corresponding to the surface shape. It is characterized in that the rotary cylinder is mounted on each of different mounting portions formed on a peripheral wall in the middle of the rotary cylinder through respective openings.

In the present invention, 3
Of the one or more feed rings, two feed rings located on both sides in the axial direction are fitted and fixed to mounting portions formed on both end surfaces of the rotary cylinder having openings corresponding to the respective axial cross-sectional shapes, that is, The entire outer peripheral surface is restrained and fixed, and the inner ring of these feed rings is engaged with the thread groove on the outer periphery of the moving shaft with high rigidity, while the center feed ring is provided with a slit-shaped opening Attach to the mounting part formed with
By adjusting the position of the feed ring, the engagement state including the feed rings on both sides is optimized.

[0021] The motion conversion device according to the second invention of the present invention comprises:
The engagement position of the center feed ring with the screw groove is on the opposite side of the opening of the mounting portion, and is set at a position circumferentially different from the engagement position of the feed rings on both sides, and Attached to the peripheral wall of the cylinder, the outer periphery of the center feed ring is pressed toward the opening of each mounting portion, and the engagement state between these feed rings and the feed rings on both sides and the thread groove is collectively determined. The present invention is characterized in that it comprises an engagement adjusting means for performing the adjustment.

In the present invention, when the central feed ring is pressed by operating the engagement adjusting means so as to optimize the engagement state with the moving shaft, the engagement position is set at a position circumferentially different from the central feed ring. In addition, the engagement state of the feed rings on both sides is optimized at a time, and the labor required for this adjustment is reduced.

Further, the power steering apparatus according to the present invention transmits power of a motor driven in accordance with steering to a steering shaft, and moves the steering shaft in the axial direction to assist steering. In the steering device, a motion conversion device according to the first invention or the second invention is used in a transmission system from the motor to the steering shaft.

In the present invention, a power transmission system from the motor for assisting steering to the steering shaft uses the motion conversion device according to the present invention, which has a simple structure, ensures reliable motion conversion, and has a small operation sound. Accordingly, a power steering device that can be compactly arranged around the steering shaft including the motor and has high quietness is realized.

[0025]

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 provided with a motion conversion device according to the present invention.

The rack shaft 2 as a moving shaft is movably supported in the axial direction inside a cylindrical rack housing 20 extending in the left-right direction of the vehicle body (not shown). Both ends of the rack shaft 2 projecting from both sides of the rack shaft are connected to left and right steering wheels (not shown) via respective tie rods.

A pinion housing 21 is provided in the middle of the rack housing 20 with its axis intersecting. Inside the pinion housing 21, a pinion shaft 22 is rotatably supported around its axis. In FIG. 1, the pinion shaft 22 has only a protruding end projecting upward from the pinion housing 21. The pinion shaft 22 is connected to a steering wheel (steering wheel) (not shown) via the protruding end. It is designed to rotate around an axis.

A pinion (not shown) is integrally formed below a pinion shaft 22 extending inside the pinion housing 21. Further, rack teeth (not shown) 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. Let me do it. Thus, the rotation of the pinion shaft 22 due to the operation of the steering wheel,
The movement of the rack shaft 2 in the axial direction is converted by the engagement of the pinion and the rack teeth, and the movement of the rack shaft 2 in the rack housing 20 is transmitted to the left and right steering wheels via the tie rods. A rack and pinion type steering mechanism that is steered according to the operation of the steering wheel is configured.

The illustrated power steering device is configured to assist the steering performed as described above by the rotational force of the electric motor. The motor 3 for assisting steering is provided inside the cylindrical motor housing 30 integrally formed by expanding the middle part of the rack housing 20 surrounding the rack shaft 2 over an appropriate length and integrally forming the motor housing 30. And a rotor coaxially arranged inside the stator 31.
32 as a three-phase brushless motor.

The rotor 32 is constituted by holding a magnetic pole 33 opposed to the outer periphery of a cylindrical body 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. The motor bearing 30 is rotatably supported by a pair of left and right ball bearings 34 and 35 around the axis of the motor housing 30, and rotates in both forward and reverse directions in response to energization of the stator 31.

The rotation of the motor 3 generated as described above is converted into the axial movement of the rack shaft 2 by the operation of the motion conversion device 1 according to the present invention, which is provided on one side of the rotor 32 as a rotating member. To be communicated.

The motion conversion device 1 includes a rotating cylinder 10 surrounding the outside of a rack shaft 2 as a moving shaft, and a plurality (three in the figure) held inside the rotating cylinder 10 in the axial direction.
, And a screw groove 12 formed on the outer peripheral surface of the rack shaft 2 over a predetermined length range including the inside of the rotary cylinder 10. The rotary cylinder 10 is rotatably supported by an extension to the same side of the motor housing 30 via a four-point contact ball bearing 13 integrally formed with an intermediate part thereof as an inner ring. Are connected coaxially via a connection bracket 36 so that the motor 3 rotates about an axis in response to the rotation of the motor 3.

FIG. 2 is a partially cutaway side view showing the configuration of the motion conversion device 1, and FIG. 3 is a cross-sectional view taken along line III-III in FIG. As shown in FIG. 2, the feed rings 11, 11,... Held by the rotary cylinder 10 hold a large number of balls between the outer ring and the inner ring, and are sufficiently larger than the outer diameter of the rack shaft 2 inserted inside. It is a ball bearing having a large inner diameter, and is mounted inside the rotary cylinder 10 with a shaft center inclined with respect to this. On the inner peripheral surface of the inner race of each feed ring 11, an engaging projection 11a having a semicircular axial cross-sectional shape corresponding to the cross-section of the thread groove 12 formed on the outer periphery of the rack shaft 2 is provided around the entire circumference. Have been. Incidentally, 13a in FIG. 2 is the four-point contact ball bearing 13a.
And a rail for ball rolling is provided.

The inclination angles of the axes of the feed rings 11, 11,...
The lead angle of the screw groove 12 formed on the outer periphery of the rack shaft 2 is set substantially equal to the lead angle, and these are provided around the inner race at circumferential positions where their inclinations match the inclination of the screw groove 12. It is engaged with the screw groove 12 via the engaging projection 11a. Also, two feed rings at both ends of the rotary cylinder 10
11, 11 and one feed ring 11 at the center are mounted with their inclination directions reversed, and the engagement position with the screw groove 12 is also set in the radial direction as shown as A and B in FIG. , That is, a position shifted by about 180 ° in the circumferential direction.

In the motion conversion device 1 configured as described above, the rotary cylinder 10 rotates around the axis in accordance with the rotation of the steering assist motor 3, and is held inside the rotary cylinder 10 with this rotation. The three feed rings 11, 11, 11 rotate. At this time, the inner ring of each feed ring 11, 11, 11 is engaged with the thread groove 12 on the outer periphery of the rack shaft 2 through the engagement protrusion 11a provided on the inner peripheral surface of each feed ring. The roller is rolled along the thread groove 12 while maintaining the engaged state. With this rolling, the rack shaft 2 is placed along the thread groove 12 at the engagement positions A and B of each feed ring 11. The rack shaft 2 is pushed by the axial component of the force and moves in the axial direction.

By the operation of the motion conversion device 1 as described above,
The rotation of the steering assist motor 3 is converted into movement in the axial direction of the rack shaft 2 inside the rack housing 20, and this movement is transmitted to left and right steering wheels via tie rods (not shown). The steering performed as described above in response to the operation of the steering wheel is assisted by the generated force of the motor 3.

The motion converter 1 can be compactly formed coaxially around the rack shaft 2 together with the motor 3 configured as described above. Also, a plurality of feed rings 11, 11,... Are held inside the rotary cylinder 10 and a screw groove 12 is formed on the outer peripheral surface of the rack shaft 2 as a moving shaft. Significant simplification of the configuration is achieved compared to a motion converter.

The feed rings 11, 11,... Are ball bearings having a large number of balls between an outer ring and an inner ring. These balls roll without changing their positions and collide with each other. Since there is no danger of operation, the operation sound is smaller than that of a ball screw type motion conversion device, and a quiet operation becomes possible.
In addition, as the feed ring 11, as a rolling element between the inner ring and the outer ring, a roller bearing having rollers instead of the balls can be used.

As described above, the motion conversion device 1 is an excellent device that can realize both a simple configuration and a quiet operation. However, the motion conversion device 1 uses the rotation of the rotary cylinder 10 as a movement axis in the axial direction of the rack shaft 2. In order to efficiently convert the movement of the rack shaft 2, a proper engagement state between the feed rings 11, 11, 11 mounted on the rotary cylinder 10 and the thread grooves 12 formed on the peripheral surface of the rack shaft 2 is required. It is important that it is possible to obtain, and furthermore, it is possible to easily carry out the adjustment work for optimizing the engagement state.

In the present invention, the mounting of the feed rings 11, 11, 11 to the rotary cylinder 10 is realized as described below, and a proper engagement state is reliably obtained, and the adjustment work for this is easily performed. To be able to do it.

As shown in FIG. 2, a pair of mounting holes 1 as mounting portions for the feed rings 11 on both sides are formed at both ends of the rotary cylinder 10.
Reference numerals 4 and 15 each have an opening at each end face and are formed to have an axis inclined with respect to the axis of the rotary cylinder 10. These mounting holes 14 and 15 are circular holes having an inner diameter substantially equal to the outer diameter of the feed ring 11 to be mounted, and the respective inclination angles are determined by the lead angle of the thread groove 12 formed in the rack shaft 2. In a plane perpendicular to the axial cross section where the inclination angle is maximized, the rotary cylinder 10 is eccentric in the same direction with respect to the axis of the rotary cylinder 10 by a predetermined length. FIG. 4 is an external perspective view showing the vicinity of the end of the rotary cylinder 10 with a part thereof cut away, and the manner of forming the mounting holes 14 (or the mounting holes 15) is clear from this figure.

Thus, of the three feed rings 11, 11, 11 held by the rotary cylinder 10, the two feed rings 11, 11 on both sides are provided.
Are pressed into the mounting holes 14 and 15 formed as described above through the openings at both ends, and are engaged with the retaining rings 16 and 16 engaged with the inner surfaces of the mounting holes 14 and 15, respectively. Each of the mounting holes 14 and 15 is fixed in such a manner that one side thereof is in contact with the bottom surface.

The mounting holes 14, 15 are positioned with respect to the axis of the rotary cylinder 10.
The feed rings 11, 11 mounted on the mounting holes 14, 15 as described above are coaxial with the inside of the rotary cylinder 10 because they are eccentric by a predetermined length on the same side and formed with the above-mentioned inclination. As shown in FIG. 3, the screw groove 12 on the outer periphery of the rack shaft 2 located at
At the circumferential position where each inclination angle matches the lead angle of the thread groove 12, the engagement is performed at the engagement position A on the same side in the radial direction. At this time, each of the feed rings 11, 11 has a corresponding one of the mounting holes 14,
Since the entire outer peripheral surface is restrained and fixed by being fitted into 15, the engagement state between these feed rings 11, 11 and the thread groove 12 on the outer periphery of the rack shaft 2 can be firmly maintained. it can.

On the other hand, among the three feed rings 11, 11, 11 held by the rotary cylinder 10, one central feed ring 11 has a slit-shaped opening on the outer peripheral surface of a corresponding portion of the rotary cylinder 10. It is mounted on the mounting portion 17 formed in this way. The shape of the slit-shaped opening 17a of the mounting portion 17 appearing on the outer periphery of the rotary cylinder 10 is shown in FIG.
The rotary cylinder 10 has a rectangular cross section inclined at substantially the same angle in a different direction from the mounting hole 14 formed at the end of the rotary cylinder 10.

The size of the opening 17a of the mounting portion 17 corresponds to the side cross-sectional shape of the feed ring 11 to be mounted.
It is adapted to be pushed into the mounting portion 17 along the inclination of the mounting portion and mounted. FIG. 5 is an explanatory view of a mounting mode of the center feed ring 11, and similarly to FIG. 3, a cross section of the rotary cylinder 10 at a position where the mounting portion 17 is formed is schematically illustrated.

As shown in the figure, the mounting portion 17 has a common axis with the rotary cylinder 10 and has a semicircular bottom surface corresponding to the outer diameter of the feed ring 11 as a concave portion provided on the opposite side of the opening 17a. Is formed. At approximately the center of the bottom surface of the mounting portion 17, there is formed a screw hole 18 which penetrates the peripheral wall of the rotating cylinder 10 on the same side in the radial direction, and this screw hole 18 has an adjusting screw 4 as an engagement adjusting means. Is screwed.

The feed ring 11 at the center is pushed into the mounting portion 17 formed as described above through the opening 17a, and is mounted in such a state that the outer periphery on the inner rear side thereof is abutted against the bottom surface of the mounting portion 17. In this state, the engagement position B on the same side as the bottom surface, that is, the engagement position A of the feed rings 11 on both sides with respect to the thread groove 12 on the outer periphery of the rack shaft 2 inserted inside the rotary cylinder 10 in this state. And at positions different from each other in the circumferential direction, are engaged via engagement protrusions 11a provided on the inner race.

This engaged state is maintained by the contact between the semicircular bottom surface of the mounting portion 17 and the outer ring of the same half of the feed ring 11, but the mounting portion having an axial cross section as shown in FIG. It is difficult to finish the inner surface shape of 17 with high accuracy, and in order to maintain good engagement at the engagement position B by this accuracy management,
Requires high processing accuracy. Further, when the engagement failure occurs at the engagement position B in this manner, the engagement state of the feed rings 11 on both sides at the engagement position A cannot be maintained well.

The distal end of the adjusting screw 4 screwed into the screw hole 18 on the bottom surface of the mounting portion 17 faces the outer surface of the feed ring 11.
By rotating, the projecting length of the mounting portion 17 to the inside can be increased. When the projecting length of the adjusting screw 4 is increased in this way, the feed ring 11 abuts on the tip of the adjusting screw 4.
Is pressed in the axial direction of the adjusting screw 4, that is, in the radial direction of the rotary cylinder 10, and the engagement protrusion 11a on the inner surface of the feed ring 11 is pressed against the screw groove 12 on the outer periphery of the rack shaft 2, and the engagement position The state of engagement between the two in B is strengthened.

When the adjusting screw 4 is further rotated, the rack shaft 2 is pressed through the center feed ring 11 with which the adjusting screw 4 comes into contact, and the other half of the rack shaft 2 is moved in the radial direction of the rotary cylinder 10. And the screw grooves 12 on the same side are pressed against the inner surfaces of the feed rings 11, 11 mounted on both ends, and the engagement state of the two at the engagement position A is strengthened.

By rotating the adjusting screw 4 as the engagement adjusting means in this manner, the 3
The engagement between the two feed rings 11, 11, 11 and the thread groove 12 formed on the peripheral surface of the rack shaft 2 is adjusted collectively. The operation of the adjusting screw 4 can be performed from the outside of the rotary cylinder 10, and the engagement adjustment in a state where the adjusting screw 4 is combined with the rack shaft 2 as a moving shaft is possible. Feed rings 11, 11 on both sides
As described above, it is supported over the entire circumference inside the respective mounting holes 14 and 15, and there is no risk of displacement due to the action force at the time of the engagement adjustment performed as described above, and reliable adjustment can be performed. .

As described above, in the motion conversion device 1, the engagement between the thread groove 12 on the outer periphery of the rack shaft 2 as the moving shaft and the plurality of feed rings 11, 11,. The rotation of the rotary cylinder 10 generated by the transmission from the motor 3 is efficiently converted into the movement of the rack shaft 2 as the moving shaft in the axial direction.

A coil spring 40 is incorporated at the tip of the adjustment screw 4 shown in the figure, and the contact with the outer surface of the feed ring 11 is made to occur via the coil spring 40. With this configuration, an appropriate engagement state can be maintained by following disturbance such as bending of the rack shaft 2, and motion conversion can be performed with high efficiency.

In the embodiment described above, the configuration in which the three feed rings 11, 11, 11 are held inside the rotary cylinder 10 has been described. However, the motion conversion device 1 according to the present invention is
This is similarly applicable to a case where three or more feed rings 11 are provided.

FIGS. 6 and 7 show an embodiment of the motion conversion device 1 provided with four feed rings 11, wherein (a) is a side view and (b) is a front sectional view.

In the motion conversion device 1 shown in FIGS.
The two feed rings 11, 11 positioned on both sides of the feed rings 11, 11,... Are provided with mounting holes 14, 15 formed at both end surfaces of the rotary cylinder 1 with openings corresponding to their axial cross sections. And the two feed rings 11, 11 located in the center are
A mounting portion formed on the peripheral wall of the rotary cylinder 1 at a corresponding position with slit-shaped openings 17a, 17a corresponding to these side surfaces.
It is attached to 17.

In the motion converter 1 shown in FIG.
As shown in (b), the engagement position A of the two feed rings 11, 11 at both ends and the engagement position B of the two feed rings 11, 11 at the center.
Are set so as to be out of phase by 180 ° in the circumferential direction, and an adjusting screw 4 as engagement adjusting means is brought into contact with one or both of the two feed rings 11 and 11 at the center. By rotating the screw 4 from the outside of the rotary cylinder 10 and pressing the central feed rings 11, 11, the four feed rings 1
Adjustment of the engagement state of 1, 11,... Can be performed collectively.

On the other hand, in the motion conversion device 1 shown in FIG. 7, four feed rings 11, 11 are provided as shown in FIG.
Are set in the circumferential direction sequentially with a phase of 120 ° apart, and both of the two central feed rings 11, 11
Adjustment screws 4, 4 serving as engagement adjusting means are brought into contact with each other, and these adjustment screws 4 are rotated from the outside of the rotary cylinder 10 in relation to each other, and the two central feed rings 11, 11 are operated.
4 feed rings by pressing
Adjustment of the engagement state of 11, 11,... Can be performed collectively.

In the above-described embodiment, an example has been described in which the rack-and-pinion type power steering apparatus is applied to an application in which the rotation of the steering assist motor 3 is transmitted to the rack shaft 1 as a moving shaft. However, the motion conversion device 1 according to the present invention is not limited to this, and 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. It is needless to say that the present invention is applicable not only to a power steering device but also to a power transmission system requiring a motion conversion from a rotary motion to a linear motion or from a linear motion to a rotary motion. .

[0060]

As described in detail above, in the motion conversion device according to the present invention, the rotary cylinder rotating around the axis holds three or more feed rings, and the two feed rings located on both sides in the axial direction are provided. By inserting the feed ring at the center into the mounting portion formed with a slit-shaped opening at the corresponding position of the rotary cylinder by fitting into the mounting portions formed on both end surfaces of the rotary cylinder, these are mounted. Since the inner ring is engaged with the thread groove formed on the outer circumference of the moving shaft, processing and assembly for mounting each feed ring can be easily performed, reducing these man-hours and restricting the entire outer circumference. It is possible to optimize the engagement state by adjusting the position of the center feed ring while ensuring rigidity by the feed rings on both sides
Strong engagement between the feed ring held by the rotary cylinder and the thread groove on the outer periphery of the moving shaft is reliably realized, and the motion conversion from the rotary motion of the rotary cylinder to the linear motion of the moving shaft or vice versa. Can be reliably performed with high efficiency.

Further, since the engaging position of the center feed ring and the engaging positions of the feed rings on both sides are set at different positions in the circumferential direction, the center feed ring is pressed by the operation of the engagement adjusting means to engage. By performing the joint adjustment, the engagement state of the feed rings on both sides is optimized at once, and the labor required for this adjustment is reduced.

Further, in the power steering apparatus according to the present invention, the above-described motion conversion device is used for converting the rotation of the steering assist motor into the movement of the steering shaft in the longitudinal direction of the steering shaft. The transmission system to the steering shaft can be compactly arranged around the steering shaft, transmission to the steering shaft can be reliably performed with high efficiency, and a quiet device with small operation noise can be realized. The present invention has excellent effects.

[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 provided with a motion conversion device according to the present invention.

FIG. 2 is a partially cutaway side view showing the configuration of the motion conversion device.

FIG. 3 is a transverse sectional view taken along line III-III of FIG. 2;

FIG. 4 is a partially cutaway perspective view of the vicinity of an end of the rotary cylinder.

FIG. 5 is an explanatory view of a mounting mode of a center feed ring.

FIG. 6 is a view showing another embodiment of the motion conversion device according to the present invention.

FIG. 7 is a view showing another embodiment of the motion conversion device according to the present invention.

FIG. 8 is an explanatory view of an engagement state between a feed ring and a moving shaft in a conventional motion conversion device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motion conversion device 2 Rack axis 3 Motor 4 Adjustment screw 10 Rotating cylinder 11 Feed ring 12 Screw groove 14 Mounting hole 15 Mounting hole 17 Mounting part

Claims (3)

[Claims] 1. A movable shaft having a screw groove formed on an outer peripheral surface thereof movably supported in an axial length direction, and rotatably supported around the axis, coaxially surrounding the outside of the movable shaft. A rotating cylinder, having an axis inclined at an angle substantially equal to the lead angle of the thread groove, eccentrically held inside the rotating cylinder, and an inner ring rotatable with respect to the rotating cylinder at one location in a circumferential direction. And a feed ring engaged with the screw groove, and by rotating the feed ring with the screw groove serving as a guide, the rotation of the rotary cylinder is moved to the movement of the moving shaft or the movement of the moving shaft. In the motion conversion device configured to convert the rotation of the rotary cylinder into three or more, three or more feed rings are arranged side by side in the axial direction of the rotary cylinder, and two feed rings on both sides are Both end faces of the rotary cylinder having a circular opening corresponding to the axial cross-sectional shape In each of the different mounting portions formed in the center, the feed ring at the center has a slit-shaped opening corresponding to these side shapes, and in each of the different mounting portions formed in the middle peripheral wall of the rotary cylinder, A motion conversion device characterized by being mounted through respective openings. 2. An engagement position of the center feed ring with the screw groove is set on a side opposite to an opening of the mounting portion, and is different from an engagement position of the feed rings on both sides in a circumferential direction. It is attached to the peripheral wall of the rotary cylinder, and presses the outer periphery of the central feed ring toward the opening of each of the mounting portions, and engages these feed rings and the feed rings on both sides with the thread grooves. The motion conversion device according to claim 1, further comprising an engagement adjusting unit that adjusts the engagement state at a time. 3. A power steering apparatus configured to transmit a rotational force of a motor driven in accordance with steering to a steering shaft and to move the steering shaft in an axial direction to assist steering, wherein the steering is performed by the motor. A power steering device, wherein the motion conversion device according to claim 1 or 2 is used for a transmission system to a shaft.