JP3841561B2 - Motion conversion device and power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motion conversion device used for motion conversion from rotational motion to linear motion, or from linear motion to rotational motion, and a power steering device using this device.
[0002]
[Prior art]
An electric power steering device that is configured to drive a steering assist electric motor in response to steering operation and transmit the rotational force of this motor to a steering mechanism to perform steering assist has been put into practical use. ing. Many of these types of power steering devices have a steering assist motor around a steering shaft (such as a rack shaft in a rack and pinion type steering mechanism) connected to steering wheels (generally, left and right front wheels). The rotational force of the motor is directly transmitted to the steering shaft, and the steering shaft is moved in the axial length direction to assist the steering.
[0003]
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 necessary. Conventionally, for example, JP-A-61-191468 As disclosed in the above, motion conversion devices using ball screws are widely used.
[0004]
In this motion conversion device, a screw groove is formed on the outer periphery of the steering shaft, and a ball nut that is screwed into the screw groove via a plurality of balls is moved in the axial direction inside a housing that supports the steering shaft. Rotate the ball nut by transmitting the rotational force of the steering assisting motor to the ball nut, and use the screwing of the screw groove accompanying this rotation to rotate the steering shaft on which the screw groove is formed. It is configured to move in the 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 between them, high transmission efficiency is obtained and the steering is performed. A limited space around the shaft, including a steering assist motor, can be compactly configured, and can meet the demand for a reduction in installation space.
[0006]
However, in the ball screw type motion converter as described above, there is a problem that high accuracy is required for forming the screw groove on the outer periphery of the steering shaft, and a great amount of processing steps are required. In this case, the adjustment of the screwed state via the ball requires a great deal of labor, and there is a problem that the number of assembling steps increases.
[0007]
In addition, a large number of balls that are screwed into the thread grooves are 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. There is a problem that the collision sound of each ball is inevitably generated with the circulation in the inside, and this collision sound is heard by the driver as an unpleasant noise.
[0008]
Under such circumstances, the electric power steering apparatus can solve the above-described problems in the ball screw type motion conversion apparatus and can be used for transmitting the rotation of the steering assist motor to the steering shaft. Realization of a novel motion conversion device that can obtain a high transmission efficiency equivalent to that of a screw-type motion conversion device and can be configured compactly is eagerly desired.
[0009]
As a motion conversion device that can meet such a longing, for example, there is a motion conversion device disclosed in Japanese Patent Publication No. 59-12898. The apparatus includes a moving shaft that is supported so as to be movable in the axial direction, a rotating cylinder that is rotatably supported around the axis, and that coaxially surrounds the outside of the moving shaft, and is eccentric to the inside of the rotating cylinder. And a plurality of feed rings in which a rotatable and rotatable inner ring is engaged with the peripheral surface of the moving shaft at one place in the circumferential direction. As the feed ring, a rolling bearing provided with a large 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.
[0010]
In Japanese Patent Laid-Open No. 59-9351, a thread groove is formed on the outer peripheral surface of the moving shaft, and an engagement protrusion provided on the inner ring of the feed ring is engaged with the thread groove, thereby engaging the both. A similar motion conversion device is disclosed in which
[0011]
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 in contact with the inner ring. It is moved in the axial direction by the action of the axial component force in the engaging portion, and the rotation of the rotating cylinder is converted into the axial movement of the moving shaft.
[0012]
At this time, the rolling of the feed ring occurs via a rolling element such as a ball or a roller interposed between the inner ring and the outer ring. Therefore, the motion conversion described above has a transmission efficiency substantially equivalent to that of the ball screw type motion converting device. It is made at. Moreover, since these rolling elements are hold | maintained without changing a mutual position between an inner ring | wheel and an outer ring | wheel, the collision of rolling elements does not generate | occur | produce and it can improve silence. Further, the rotating cylinder has a simple configuration in which a plurality of feed rings (bearings) are held inside thereof, and the configuration can be greatly simplified as compared with a ball screw type motion converter.
[0013]
[Problems to be solved by the invention]
However, even in the motion conversion device configured as described above, it is essential to adjust the engagement state between the feed ring and the moving shaft in order to perform a favorable motion conversion operation.
[0014]
In the motion conversion device disclosed in Japanese Patent Publication No. 59-12898, a plurality of feed rings 5 (only one shown) are arranged at the corresponding positions of the rotary cylinder 6 as shown in FIG. Is inserted into the mounting holes 60 formed through and having a width corresponding to the above, and the block-shaped pressing member 61 inserted from one side into each mounting hole 60 is brought into contact with the same half of the outer ring, The pressing members 61 are collectively restrained by the cylindrical springs 62 fitted on the rotary cylinder 6 so that the pressing members 61 are pulled out from the mounting holes 60, and the feed rings are arranged inside the contact positions of the pressing members 61. A mounting mode in which the inner ring 5 is engaged with the moving shaft 7 is employed.
[0015]
In this configuration, the engagement state between each of the plurality of feed rings 5 and the moving shaft 7 is determined by the accuracy of the dimension between the inner and outer surfaces of each of the separate pressing members 61 (X dimension in the drawing). When the adjustment is to be performed, it is necessary to adjust the dimensions of the pressing member 61 having an inner surface corresponding to the outer shape of the feed ring 5 and an outer surface corresponding to the outer shape of the rotary cylinder 6 and having an irregular cross section as shown in the drawing. However, there is a problem that it takes a lot of man-hours.
[0016]
Further, since the engagement 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 engagement strength. There is a problem that it is difficult to apply to a use that requires transmission of a large force between the rotating cylinder 6 and the moving shaft 7 as in the case of the taking device.
[0017]
Enhancing 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, but even in the configuration disclosed in this publication, In order to obtain an appropriate engagement state between the feed ring and the moving shaft, it is required to improve the processing and assembly accuracy of each member, including the dimension adjustment of the spacer that contacts one side of the feed ring, There is a problem of requiring a great amount of man-hours.
[0018]
The present invention has been made in view of such circumstances, and it is easy to adjust the engagement state in the assembled state, and the strong engagement between the feed ring held by the rotating cylinder and the moving shaft is achieved. A motion conversion device with a simple configuration that can be reliably realized and that can reliably perform motion conversion from the rotational motion of the rotating cylinder to the linear motion of the moving shaft, or the motion conversion opposite thereto, and using the same An object is to provide a power steering apparatus.
[0019]
[Means for Solving the Problems]
  The motion conversion device according to the first aspect of the present invention is supported so as to be movable in the axial length direction, and has a moving shaft having a thread groove formed on the outer peripheral surface thereof, and is supported so as to be rotatable about the axis. A rotating cylinder that coaxially surrounds the outside of the cylinder, and an inner ring that has an axis that is inclined at an angle substantially equal to the lead angle of the thread groove, is eccentrically held inside the rotating cylinder, and is rotatable with respect to the rotating cylinder And a feed ring engaged with the screw groove at one circumferential position, and the rotation of the rotary cylinder is moved by the rolling of the feed ring guided by the screw groove. In the motion conversion device configured to convert the movement of the moving shaft into the rotation of the rotating cylinder, three or more feed rings are juxtaposed in the axial length direction of the rotating cylinder. The two feed rings have circular openings corresponding to these axial cross-sectional shapesOn both end faces of the rotating cylinderHaveEccentric to the same side with respect to the axis of the rotating cylinderIn each separate mounting part formed,The entire outer peripheral surface is restrained and installed.The center feed ring has a slit-like opening corresponding to the side shape of the center feed ring, and is attached to a mounting portion formed on the middle peripheral wall of the rotating cylinder.Slit-shapedIt is mounted through an opening, and the engagement position of the central feed ring with the screw groove is opposite to the opening of the mounting portion of the central feed ring, and the thread groove of the feed ring on both sides The radial position of the central feed ring can be adjusted by a member whose position can be changed in the radial direction.
[0020]
  In the present invention, among the three or more feed rings held by the rotating cylinder, two feed rings positioned on both sides in the axial direction are provided with openings corresponding to the respective axial cross-sectional shapes.Hold on both end faces of the rotating cylinderFit into the formed mounting part, On each separate mounting partRestrain the entire outer surfaceFirmlyThe inner ring of these feed rings is fixed and engaged with the thread groove on the outer periphery of the moving shaft with high rigidity, while the central feed ring is formed with a slit-like opening at the corresponding position of the rotary cylinder To the circumferential position different from the feed rings on both sides.Engage with the thread on the outer periphery of the moving shaft.Adjust the engagement position with a member whose position can be changed in the radial direction.Supporting the feed rings on both sides engaged under high rigidityMake the engagement state appropriate.
[0021]
  The motion conversion device according to the second aspect of the present invention is the engagement position of the central feed ring with the thread groove.BeforeOf the feed rings on both sidesWith the thread grooveEngagement positionOpposite side ofIs set toAn adjustment screw for changing and adjusting the radial position of the central feed ring is attached to the peripheral wall of the rotary cylinder, and the adjustment screw is engaged with the central feed ring in the circumferential direction of the rotary cylinder. The tip position is provided at a position that coincides with the alignment position so that the position of the tip can be changed in the radial direction. The adjustment screw is operated to rotate and press the outer periphery of the central feed ring. By pressing the moving shaft toward the opening side of the mounting portion,Feed ring andSaidWith feed rings on both sidesSaidBatch adjustment of engagement with thread grooveI can do itIt is characterized by that.
[0022]
  In this invention, the movement axisOuter thread grooveTo optimize the engagement state withRotating adjustment screwWhen the center feed ring is pressed by operation, the engagement states of the feed rings on both sides whose engagement positions are set at different positions in the circumferential direction are collectively optimized, and the effort required for this adjustment is reduced. Reduced.
[0023]
Furthermore, the power steering apparatus according to the present invention is configured to transmit the rotational force of a motor driven in accordance with steering to the steering shaft, and to move the steering shaft in the axial direction to assist the steering. The motion conversion device according to the first invention or the second invention is used in the transmission system from the motor to the steering shaft.
[0024]
  In the present invention, the transmission system from the steering assisting motor to the steering shaft can be surely converted into motion while having a simple configuration, and the motion conversion device according to the present invention with low operating noise is used. Can be placed compactly around the steering shaft, including a power steering system with high quietness.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a partially broken front view showing a configuration of a main part of a power steering apparatus provided with a motion conversion apparatus according to the present invention.
[0026]
A rack shaft 2 as a moving shaft is supported in a cylindrical rack housing 20 extending in the left-right direction of a vehicle body (not shown) so as to be movable in the axial direction, on both sides of the rack housing 20. Both ends of the rack shaft 2 projecting from each other are connected to left and right steering wheels (not shown) via separate tie rods.
[0027]
A pinion housing 21 is connected to the middle portion of the rack housing 20 so as to cross the shaft center. A pinion shaft 22 is supported inside the pinion housing 21 so as to be rotatable about its axis. In FIG. 1, the pinion shaft 22 is shown only at the protruding end to the top of the pinion housing 21, and is connected to a steering wheel (not shown) via this protruding end, and in response to the operation of the steering wheel for steering. It is designed to rotate around its axis.
[0028]
A pinion (not shown) is integrally formed at the lower part of the pinion shaft 22 extending inside the pinion housing 21. A rack tooth (not shown) is formed on the rack shaft 2 supported in the rack housing 20 over an appropriate length including the crossing position with the pinion housing 21, and meshes with the pinion below the pinion shaft 22. I'm allowed. Thus, the rotation of the pinion shaft 22 due to the operation of the steering wheel is converted into the movement in the axial direction of the rack shaft 2 by the engagement of the pinion and the rack teeth, and the movement of the rack shaft 2 in the rack housing 20 is A rack and pinion type steering mechanism is configured which is transmitted to the left and right steering wheels via the tie rods, and is steered according to the operation of the steering wheel.
[0029]
The illustrated power steering apparatus is configured to assist the steering performed as described above with the rotational force of the electric motor. The steering assisting motor 3 includes a cylindrical motor housing 30 integrally formed by expanding a middle portion of the rack housing 20 surrounding the rack shaft 2 over an appropriate length. This is configured as a three-phase brushless motor including a stator 31 fixedly provided on the inner peripheral surface thereof and a rotor 32 disposed coaxially inside the stator 31.
[0030]
The rotor 32 is configured to hold a magnetic pole 33 facing the inner surface of the stator 31 with a slight gap on the outer periphery of a cylindrical body having an inner diameter larger than the outer diameter of the rack shaft 2. A pair of left and right ball bearings 34 and 35 are rotatably supported about the axis of the motor housing 30 and rotate in both forward and reverse directions in response to energization of the stator 31.
[0031]
The rotation of the motor 3 generated as described above is converted into an axial movement and transmitted to the rack shaft 2 by the operation of the motion conversion device 1 according to the present invention configured on one side of the rotor 32 as a rotating member. It is supposed to be.
[0032]
The motion conversion device 1 includes a rotating cylinder 10 that surrounds the outside of a rack shaft 2 as a moving shaft, and a plurality of (three in the figure) feed rings 11 that are held in the axial direction in the rotating cylinder 10. , 11... And a thread 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 portion as an inner ring. Are connected coaxially via a connecting bracket 36 and rotate about an axis in accordance with the rotation of the motor 3.
[0033]
FIG. 2 is a partially broken 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 an axis that is inclined with respect to this. On the inner peripheral surface of the inner ring of each feed ring 11, an engaging projection 11a having a semicircular shaft 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. Has been. Note that 13a in FIG. 2 is a portion constituting the inner ring of the four-point contact ball bearing 13, and a rail for ball rolling is provided.
[0034]
The inclination angle of the shaft center of the feed rings 11, 11... Is set to be substantially equal to the lead angle of the thread groove 12 formed on the outer periphery of the rack shaft 2. At a circumferential position that coincides with the inclination, the thread groove 12 is engaged via an engagement protrusion 11a provided around the inner ring. In addition, the two feed rings 11 and 11 at both ends of the rotary cylinder 10 and the one feed ring 11 at the center are attached with their inclination directions reversed, and the engagement position with the thread groove 12 is also as follows. As indicated by A and B in FIG. 3, the positions are opposed to each other in the radial direction, that is, the positions are shifted by approximately 180 ° in the circumferential direction.
[0035]
In the motion conversion device 1 configured as described above, the rotating cylinder 10 rotates around the axis in accordance with the rotation of the steering assisting motor 3, and the three feeds held inside the rotating cylinder 10 with this rotation. Rings 11, 11, and 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 via the engagement protrusion 11a provided on the inner peripheral surface of each of the feed rings 11, 11, 11. The roller shaft 2 rolls along the thread groove 12 while maintaining the engaged state, and the rack shaft 2 moves along the thread groove 12 at the engagement positions A and B of the feed rings 11 along with the rolling. The rack shaft 2 is pressed by the axial component of the force and moves in the axial length direction.
[0036]
By such an operation of the motion conversion device 1, the rotation of the steering assist motor 3 is converted into a movement in the axial direction of the rack shaft 2 inside the rack housing 20, and this movement is performed via a tie rod (not shown). Therefore, the steering performed as described above according to the operation of the steering wheel is assisted by the generated force of the motor 3.
[0037]
The motion conversion device 1 can be configured coaxially and compactly around the rack shaft 2 together with the motor 3 configured as described above. Further, 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 the motion converter.
[0038]
The feed rings 11, 11,... Are ball bearings having a large number of balls between the outer ring and the inner ring, and these balls roll without changing their position and may collide with each other. Therefore, the operation sound is smaller than that of a ball screw type motion conversion device, and a quiet operation is possible. As the feed ring 11, a roller bearing provided with a roller in place of the ball can be used as a rolling element between the inner ring and the outer ring.
[0039]
As described above, the motion conversion device 1 is an excellent device capable of realizing both a simple configuration and a quiet operation. However, the rotation of the rotary cylinder 10 is used to move the rack shaft 2 in the axial length direction as a moving shaft. In order to convert efficiently, an appropriate engagement state is obtained between the feed rings 11, 11, 11 mounted on the rotary cylinder 10 and the thread groove 12 formed on the peripheral surface of the rack shaft 2. Furthermore, it is important that adjustment work for optimizing the engagement state can be easily performed.
[0040]
In the present invention, the attachment of the feed rings 11, 11, and 11 to the rotary cylinder 10 is realized as shown below so that an appropriate engagement state can be reliably obtained and adjustment work for this can be easily performed. I have to.
[0041]
As shown in FIG. 2, a pair of mounting holes 14 and 15 as mounting portions for the feed rings 11 and 11 on both sides are provided at both ends of the rotating cylinder 10. It is formed with an axis that is inclined with respect to the center. 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 the lead angles of the thread grooves 12 formed in the rack shaft 2. Furthermore, they are decentered by a predetermined length in the same direction with respect to the axis of the rotary cylinder 10 in a plane orthogonal to the axial cross section where the inclination angle is maximum. FIG. 4 is an external perspective view showing the vicinity of the end of the rotary cylinder 10 with a part thereof broken, and the formation mode of the mounting hole 14 (or mounting hole 15) is clear in this figure.
[0042]
Thus, among the three feed rings 11, 11, 11 held by the rotary cylinder 10, the two feed rings 11, 11 on both sides are respectively connected to the mounting holes 14, 15 formed as described above at both ends. It is press-fitted through the opening of the part, and fixed to a state where one side is abutted against the bottom surface of each mounting hole 14, 15 by engagement with a retaining ring 16, 16 engaged with the inner surface of each mounting hole 14, 15 Has been.
[0043]
Since the mounting holes 14 and 15 are decentered by a predetermined length on the same side with respect to the axis of the rotating cylinder 10 and are formed with the aforementioned inclination, both sides mounted in the mounting holes 14 and 15 as described above. As shown in FIG. 3, the feed rings 11, 11 of the feed ring 11, 11 are aligned with the lead angle of the screw groove 12 as shown in FIG. 3 with respect to the screw groove 12 on the outer periphery of the rack shaft 2. In the circumferential position, 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 and 11 is fixed with the entire outer peripheral surface being restrained and fixed by being fitted into the mounting holes 14 and 15 having a circular cross section corresponding thereto. 11 and 11 can be firmly maintained in engagement with the thread groove 12 on the outer periphery of the rack shaft 2.
[0044]
On the other hand, among the three feed rings 11, 11, 11 held by the rotary cylinder 10, one central feed ring 11 is formed with a slit-like opening on the outer peripheral surface of the corresponding part of the rotary cylinder 10. It is attached to the mounting part 17 The shape of the slit-like opening 17a of the mounting portion 17 that appears on the outer periphery of the rotating cylinder 10 is shown in FIG. 4 and is formed at the end of the rotating cylinder 10 with respect to the axis of the rotating cylinder 10. It has a rectangular cross section inclined at substantially the same angle in a direction different from that of the mounting hole 14.
[0045]
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, and the center feed ring 11 is mounted along the inclination of the opening 17a from the outside of the rotating cylinder 10. It is designed to be pushed into the part 17 and mounted. FIG. 5 is an explanatory view of the mounting mode of the central feed ring 11, and the cross section of the rotary cylinder 10 at the position where the mounting portion 17 is formed is schematically shown in the same manner as FIG. 3.
[0046]
As shown in the figure, the mounting portion 17 is formed as a recess having a common axis with the rotary cylinder 10 and having a semicircular bottom surface corresponding to the outer diameter of the feed ring 11 on the opposite side of the opening 17a. Yes. A screw hole 18 that penetrates the peripheral wall of the rotating cylinder 10 on the same side in the radial direction is formed in the approximate center of the bottom surface of the mounting portion 17, and an adjusting screw 4 as an engagement adjusting means is formed in the screw hole 18. Are screwed together.
[0047]
The central feed ring 11 is pushed into the mounting portion 17 formed as described above through the opening 17a, and is mounted in a state where the outer periphery on the inner side is abutted against the bottom surface of the mounting portion 17. The engagement position B on the same side as the bottom surface, that is, the engagement position A of the feed rings 11 and 11 on both sides and the circumferential direction with respect to the thread groove 12 on the outer periphery of the rack shaft 2 inserted inside the rotary cylinder 10 in the state Are engaged with each other via engagement protrusions 11a provided around the inner ring.
[0048]
This engagement state is maintained by contact between the semicircular bottom surface of the mounting portion 17 and the outer ring on the same half portion of the feed ring 11, but the inner surface of the mounting portion 17 having an axial cross section as shown in FIG. It is difficult to finish the shape with high accuracy, and high processing accuracy is required to maintain good engagement at the engagement position B by this accuracy control. Further, when an engagement failure occurs in the engagement position B in this way, the engagement state of the feed rings 11 on both sides at the engagement position A cannot be maintained well.
[0049]
The tip of the adjustment 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, and this tip portion rotates the adjustment screw 4 from the outside of the rotary cylinder 10. By doing so, the protrusion length to the inner side of the mounting portion 17 can be increased. When the protruding length of the adjusting screw 4 is increased in this way, the feed ring 11 that comes into contact with the tip of the adjusting screw 4 is pressed in the axial length direction of the adjusting screw 4, that is, in the radial direction of the rotary cylinder 10. The engagement protrusion 11a on the inner surface is pressed against the thread groove 12 on the outer periphery of the rack shaft 2, and the engagement state of both at the engagement position B is strengthened.
[0050]
When the adjustment screw 4 is further rotated, the rack shaft 2 is pressed via the central feed ring 11 with which the adjustment screw 4 abuts, and the other half of the rack shaft 2 is displaced in the radial direction of the rotary cylinder 10. The thread groove 12 on the same side is pressed against the inner surfaces of the feed rings 11 and 11 mounted on both ends, and the engagement state of the both at the engagement position A is strengthened.
[0051]
Thus, by rotating the adjusting screw 4 as the engagement adjusting means, the three feed rings 11, 11, 11 held by the rotary cylinder 10 and the thread groove 12 formed on the peripheral surface of the rack shaft 2 are used. Are collectively adjusted. The adjustment screw 4 can be operated from the outside of the rotary cylinder 10, and engagement adjustment in a state where it is combined with the rack shaft 2 as a moving shaft is possible. As described above, the feed rings 11 and 11 on both sides are supported over the entire circumference in the respective mounting holes 14 and 15, and may be displaced due to the acting force during the engagement adjustment performed as described above. There is no such thing and reliable adjustment can be made.
[0052]
As described above, in the motion conversion device 1, the engagement state between the thread groove 12 on the outer periphery of the rack shaft 2 as a moving shaft and the plurality of feed rings 11, 11... Can be easily and reliably optimized. The rotation of the rotary cylinder 10 caused by the transmission from the motor 3 is efficiently converted into movement in the axial direction of the rack shaft 2 as a moving shaft.
[0053]
A coil spring 40 is incorporated at the tip of the adjustment screw 4 shown in the figure, and contact with the outer surface of the feed ring 11 occurs via the coil spring 40. With this configuration, it is possible to follow a disturbance such as the deflection of the rack shaft 2 and maintain an appropriate engagement state, and it is possible to perform motion conversion with high efficiency.
[0054]
In the above embodiment, 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 has three feed rings 11. The present invention can be similarly applied in the case of providing the above.
[0055]
6 and 7 show an embodiment of the motion conversion device 1 including four feed rings 11, wherein (a) is a side view and (b) is a front sectional view.
[0056]
In the motion conversion device 1 shown in these figures, of the four feed rings 11, 11..., The two feed rings 11, 11 located on both sides have openings corresponding to the axial cross sections on both end faces of the rotary cylinder 1. The two feed rings 11, 11 that are mounted in the mounting holes 14, 15 formed in the center and that are located in the center are slit-shaped openings 17 a, corresponding to these side surfaces, on the peripheral wall of the corresponding position of the rotary cylinder 1. It is mounted on a mounting portion 17 formed with 17a.
[0057]
In the motion conversion device 1 shown in FIG. 6, as shown in (b), the engagement position A of the two feed rings 11 and 11 at both ends and the engagement position B of the two center feed rings 11 and 11 are as follows. The phase is shifted by 180 ° in the circumferential direction, and an adjustment screw 4 as an engagement adjusting means is brought into contact with one or both of the two feed rings 11 and 11 at the center. Is rotated from the outside of the rotary cylinder 10 and the center feed rings 11, 11 are pressed to adjust the engagement state of the four feed rings 11, 11,.
[0058]
On the other hand, in the motion conversion device 1 shown in FIG. 7, as shown in FIG. 7B, the engagement positions of the four feed rings 11, 11,. In addition, adjustment screws 4 and 4 as engagement adjusting means are brought into contact with both of the two central feed rings 11 and 11, and these adjustment screws 4 are related to each other from the outside of the rotary cylinder 10. By rotating the two feed rings 11 and 11 in the respective directions, the engagement states of the four feed rings 11 can be adjusted at a time.
[0059]
In the above-described embodiment, the rack and pinion type power steering apparatus has been described as an application example for transmitting the rotation of the steering assisting motor 3 to the rack shaft 1 as a moving shaft. The motion conversion device 1 according to the invention is not limited to this, and various types of power steering devices that are configured to transmit the rotation of a steering assist motor to a steering shaft that performs steering by movement in the axial length direction. Needless to say, the present invention is not limited to the power steering apparatus, and can be applied to any transmission system that requires a motion conversion from a rotational motion to a linear motion or from a linear motion to a rotational motion.
[0060]
【The invention's effect】
  As described above in detail, in the motion conversion device according to the present invention, three or more feed rings are held on a rotating cylinder that rotates around an axis, and two feed rings positioned on both sides in the axial direction are connected to both ends of the rotating cylinder. The center feed ring is attached by fitting into the attachment part formed with a slit-like opening at the corresponding position of the rotary cylinder by fitting into the attachment part formed on the surface, and these inner rings are attached to the moving shaft. Since it is engaged with the thread groove formed on the outer periphery, the processing and assembly for mounting each feed ring can be performed easily, and the man-hours can be reduced, and the feeding on both sides with the entire outer periphery restrained. Central feed ring while ensuring rigidity with ringAdjust the position of engagement with the screw groove with a member whose position can be changed in the radial direction.The engagement state can be optimized, and a strong engagement between the feed ring held by the rotating cylinder and the thread groove on the outer periphery of the moving shaft is reliably realized. Motion conversion to linear motion or motion conversion opposite thereto can be reliably performed with high efficiency.
[0061]
  Also, the engagement position of the center feed ring and the engagement position of the feed rings on both sidesopposite sideSet to positionRotate the adjustment screwoperationdo itPress the center feed ringBecause it is configured to be a central feed ring andThe engagement state of the feed rings on both sides is optimized at once, and the labor required for this adjustment is reduced.
[0062]
Furthermore, in the power steering apparatus according to the present invention, since the motion conversion apparatus as described above is used to convert the rotation of the steering assist motor into the axial movement of the steering shaft, the transmission from the motor to the steering shaft. The system can be arranged compactly around the steering shaft, the transmission to the steering shaft can be reliably performed with high efficiency, and a quiet operation can be realized with a small operating noise. Has an excellent effect.
[Brief description of the drawings]
FIG. 1 is a partially broken front view showing a configuration of a main part of a power steering apparatus including a motion conversion device according to the present invention.
FIG. 2 is a partially broken side view showing the configuration of the motion conversion device.
3 is a cross-sectional view taken along line III-III in FIG.
FIG. 4 is a partially broken perspective view in the vicinity of an end of a rotating cylinder.
FIG. 5 is an explanatory view of a mounting mode of a central feed ring.
FIG. 6 is a diagram showing another embodiment of the motion conversion device according to the present invention.
FIG. 7 is a diagram 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]
1 motion converter
2 Rack shaft
3 Motor
4 Adjustment screw
10 Rotating cylinder
11 Feed ring
12 Thread groove
14 Mounting hole
15 Mounting hole
17 Mounting part

Claims (3)

A movable shaft that is supported so as to be movable in the axial length direction and has a thread groove formed on an outer peripheral surface thereof; a rotary cylinder that is rotatably supported around the shaft and coaxially surrounds the outside of the movable shaft; and An inner ring that is eccentrically held inside the rotating cylinder and has an axis inclined at an angle substantially equal to the lead angle of the thread groove, and an inner ring that is rotatable with respect to the rotating cylinder is formed in the thread groove at one place in the circumferential direction. A feed ring that is engaged, and by rotating the feed ring that guides the thread groove, the rotation of the rotary cylinder is changed to the movement of the movement axis, or the movement of the movement axis is changed to that of the rotation cylinder. In the motion conversion device configured to convert to rotation, three or more of the feed rings are juxtaposed in the axial length direction of the rotary cylinder, and the two feed rings on both sides correspond to these axial cross-sectional shapes. a circular opening which has both end faces of the rotary cylinder of the rotary cylinder Each separate mounting part formed eccentrically on the same side with respect to heart, Yes wearing constraining the entire surface of the outer peripheral surface, the center of the feed ring corresponds to the side shape of the central feed ring slit A mounting portion formed on the middle peripheral wall of the rotating cylinder through the slit-shaped opening, and the engagement position of the central feed ring with the thread groove is It is opposite to the opening of the mounting portion of the central feed ring, and is set at a position different from the engagement position with the thread groove of the feed rings on both sides, and the radial direction of the central feed ring A motion conversion device characterized in that the position can be adjusted by a member whose position can be changed in the radial direction.   The engagement position of the central feed ring with the screw groove is set on the opposite side of the engagement position of the feed ring on both sides with the screw groove, and the radial position of the central feed ring is changed. An adjustment screw for adjusting the position of the rotary cylinder is attached to the peripheral wall of the rotary cylinder, and the adjustment screw is positioned at a position that coincides with the engagement position of the central feed ring in the circumferential direction of the rotary cylinder. The adjustment screw is rotated so that the outer periphery of the central feed ring is pressed to rotate the moving shaft through the central feed ring and the opening of the mounting portion. 2. The motion conversion device according to claim 1, wherein the state of engagement between the central feed ring and the feed rings on both sides and the thread groove can be collectively adjusted by pressing toward the side.   In a power steering apparatus configured to transmit the rotational force of a motor driven in accordance with steering to a steering shaft and to assist the steering by moving the steering shaft in the axial direction, a transmission system from the motor to the steering shaft A power steering apparatus using the motion conversion apparatus according to claim 1 or 2.

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