JP2007120658A - Rotation-linear motion converting mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the occurrence of backlash due to the elongation of a roller in a rotation-linear motion converting mechanism which improves the meshing between a roller and a rod, facilitates the assembly and enables the handling of a large load. <P>SOLUTION: A rotation-linear motion converting mechanism which is equipped with a rod 1 containing a screw part in the outer peripheral surface, a holder member 3 provided to the outer peripheral side of the rod so as to be relatively rotated and relatively axially moved with respect to the rod, a roller 21 rotatably supported by a holder member, provided with an annular groove meshing with the screw part and arranged torsionally at a shaft angle more than a lead angle of the screw part with respect to a rod shaft, includes one-way roller thrust bearing 21e3 which rotatably supports the roller 21 and receives thrust load in the one-way direction of the roller shaft and the-other-way roller thrust bearing 21e4 which receives thrust load in the-other-way direction of the roller shaft. Both one-way roller thrust bearing and the-other-way roller thrust bearing are arranged only in one end 21c1 adjacent to an annular groove mounting part of the roller. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rotation / linear motion conversion mechanism that converts rotational torque and thrust force by converting the direction of motion between rotational motion and linear motion, and in particular, has a small backlash and maintains a good meshing state at all times. The present invention relates to a rotation / linear motion conversion mechanism that has good assemblability and can handle a large load.

  In a reciprocating linear motion mechanism comprising a rotating shaft and an elastic roller that is in rolling contact with the rotating shaft, a large thrust is generated with a small surface pressure by increasing the length of the contact arc between the rotating shaft and the elastic roller by elastic deformation. The structure which acquires force is proposed (for example, refer patent document 1).

The mechanism shown in Cited Document 1 is composed of a cylindrical rod, a cylindrical elastic roller arranged by twisting around the rod, and a holder that rotatably supports the roller. Is the one that moves directly. In this way, the mechanism shown in the cited document 1 is to transmit force between the rod and the roller, not the mesh between the screw and the annular groove, but friction between the two. In other words, it is similar to the mechanism of the present invention.
JP-A-6-174041

  In the prior art disclosed in Patent Document 1, the thrust bearing that receives the thrust load on the roller holder is configured to be provided at both ends of the roller. For this reason, depending on the direction of the thrust load, the position of the thrust bearing that receives the load from one direction or the other direction moves by the length of the roller. As a result, the thrust bearing on the side that does not receive a load has an axial gap inside the thrust bearing due to the elongation of the roller between the two thrust bearings (the amount of elongation of the roller corresponding to the length of the roller). Due to the action of the reversal force, there was a problem that rattling occurred in the operation of the rod.

  In order to solve the above-described problems, an object of the present invention is to provide a linear motion conversion mechanism that can reduce the occurrence of rattling due to elongation of a roller. It is another object of the present invention to provide a rotation / linear motion conversion mechanism that makes the roller and rod mesh well with each other, facilitates assembly of the apparatus, and can handle a heavy load.

In order to solve the above problems, the present invention mainly adopts the following configuration.
A rod having a threaded portion on the outer peripheral surface, a holder member provided on the outer peripheral side of the rod so as to be rotatable relative to the rod and movable relative to the rod, and rotatably supported by the holder member A rotary linear motion conversion mechanism comprising: an annular groove that engages with the screw portion on an outer peripheral surface, and a roller that is twisted and arranged at an axial angle equal to or greater than a lead angle of the screw portion with respect to a central axis of the rod. There,
A one-way roller thrust bearing that rotatably supports the roller and receives a thrust load in one direction of the roller shaft, and a two-way roller thrust bearing that receives a thrust load in the other direction of the roller shaft are provided. Both the direction roller thrust bearing and the other direction roller thrust bearing are arranged only at one end adjacent to the annular groove installation portion of the roller.

  Further, in the rotation / linear motion converting mechanism, a roller that operates integrally with a holder member fixed side raceway of both roller thrust bearings along the roller between the one-way roller thrust bearing and the other-direction roller thrust bearing. A radial bearing is interposed, a roller mounting screw for the holder member is provided on the outer ring of the roller radial bearing, and the roller mounting screw is adjusted in a state where the roller incorporated in the holder member is engaged with the rod. Thus, the axial position of the roller is changed and fixed.

  According to the present invention, it is possible to reduce the occurrence of rattling along with the elongation of the roller, so that the controllability is improved. Further, since the meshing state between the roller for transmitting the force and the rack is improved, the reliability can be improved and the loss of the meshing portion can be reduced, so that the reliability of the apparatus is improved and the efficiency is improved. In addition, the assemblability is improved, and there is an effect of reducing cost reduction and performance variation during mass production. Moreover, a large thrust can be generated.

  A configuration example in which the rotation / linear motion conversion mechanism according to the embodiment of the present invention is applied to a rack assist type electric power steering apparatus for an automobile will be described in detail below. As a configuration example of the first embodiment of the present invention, a type in which the rod side does not rotate is presented, and this configuration example will be described with reference to FIGS. 1 to 7, 15, and 16.

  FIG. 1 is a longitudinal sectional view of a rack assist mechanism in an electric power steering apparatus to which a rotation / linear motion conversion mechanism according to a first embodiment of the present invention is applied, and FIG. 2 is a view rotated 90 degrees from the viewpoint of FIG. It is a longitudinal cross-sectional view at the time (when it looks down from the upper part of FIG. 1), and is the figure which drawn the roller which comes to the near side. 3 is a side view of all the rollers, FIG. 4 is a side view of the roller / holder member subassembly, and FIG. 5 is a cross-sectional view of the subassembly shown in FIG.

  FIG. 6 is an enlarged cross-sectional view of the right roller bearing portion, which is an M portion shown in FIG. Here, although M part is also shown in FIG. 4, the cross section is different from the case of FIG. However, since the bearing portion and the roller are rotating bodies having the roller shaft as a rotation shaft, and the crossing angle of these two cross sections with respect to the roller shaft is substantially equal, the cross section of the bearing portion has a substantially equal shape (in contrast, The cross section of the holder part is different). Therefore, since FIG. 4 can be substantially described with reference to FIG. 6 (M portion in FIG. 1), a new view showing the M portion having the same cross section as FIG. 1 is omitted. FIG. 7 is an enlarged cross-sectional view of the left roller bearing portion, which is an N portion shown in FIG. Similarly to the M part, this is also an explanatory diagram of the N part in FIG. Here, FIGS. 6 and 7 are enlarged views of the roller 21, but the bearings of the other rollers 22 and 23 are the same, and thus illustration and description thereof are omitted.

  FIG. 15 is a diagram showing an arrangement of the rack assist mechanism to which the present embodiment is applied in the electric power steering apparatus, and FIG. 16 is a diagram for explaining the rotation / linear motion conversion operation according to the present embodiment.

  First, the configuration of the rotation / linear motion conversion mechanism according to the present embodiment will be described. First, a subassembly composed of the rollers 21, 22, 23 and the holder 3 shown in FIGS. 4 and 5 will be described. As can be seen from FIG. 3, the right roller ends 21c1 to 23c1 of these rollers are longer than the left roller ends 21c2 to 23c2. The lengths of the left and right end portions of the roller are different. As shown in FIG. 7 which is representative of the roller 21, only the radial bearing (hereinafter referred to as the left roller radial bearing 21f2) is installed at the left roller end portion. On the other hand, the end portion of the right roller receives a radial load (referred to as the right roller radial bearing 21f1 hereinafter) as shown in FIG. This is because a plurality of roller thrust bearings (hereinafter referred to as right roller thrust bearing 21e3 and left roller thrust bearing 21e4) are arranged. After the roller thrust bearing 21e is fixed by the thrust lock nut 21j, the roller thrust bearing 21e is disposed on the right holder end plate 3c with a screw (hereinafter referred to as a roller mounting screw 21m) provided on the outer periphery of the right roller radial bearing 21f1.

  As described above, since the thrust bearing that receives the thrust load in both the left and right directions is arranged at the roller end of one of the roller annular groove installation portions (right side in the present embodiment), both thrust bearings are provided on both sides of the roller annular groove installation portion. It becomes possible to shorten the space | interval of both thrust bearings rather. When pulled, the amount of elongation of the roller between the two thrust bearings becomes small.

  Here, when a thrust load is applied to the roller 21 from the left to the right (the thrust load is a load generated by the engagement state of the annular groove of the roller and the screw portion of the rod, and a load in the left direction and the right direction is generated). think of. At this time, since the left roller thrust bearing 21e4 receives the load, no load is applied to the right roller end portion 21c1, and there is no expansion / contraction deformation. For this reason, the other right roller thrust bearing 21e3 maintains a state in which a preload is applied by the thrust lock nut 21j.

  Next, consider a case where a thrust load is applied to the roller 21 from right to left. At this time, since the right roller thrust bearing 21e3 receives the load, a tensile load is applied to the right roller end portion 21c1, and elongation occurs. For this reason, in the left roller thrust bearing 21e4, the preload by the thrust lock nut 21j is reduced, and when the load is large, an axial gap is generated between the raceway and the rolling element. When an impact reversal load (thrust load from left to right) is applied from a state in which this gap is generated (thrust load from right to left), the elongation of the right roller end 21c1 is eliminated. Before (with a gap between the raceway and the rolling element), the roller impactively moves from left to right, and the left roller thrust bearing 21e4 shifts to a state where it receives force.

  Since the rod meshes with the roller, it means that the rod moves impactively in the direction of the impact load in the case of the reverse load. That is, rattling occurs in the movement of the rod. Further, in this embodiment, since the roller thrust bearing is a rolling bearing, there is a possibility that the rolling element is dropped from the raceway due to this gap. If this drop-off occurs, the original function of the bearing is impaired, and the operation of the highly efficient linear motion conversion mechanism becomes impossible. Occurs.

  As described above, as a measure for suppressing the gap in the thrust bearing that may cause various problems, an increase in the preload of the thrust bearing can be cited (for example, tightening by the thrust lock nut 21j is strengthened). However, an excessive increase in the preload increases the bearing coefficient of the thrust bearing, causing a negative effect of reducing the efficiency of the rotation / linear motion conversion mechanism.

  Therefore, as in this embodiment, by providing a thrust bearing corresponding to both directions at one end of the annular groove installing portion in the roller, the shaft of the two roller thrust bearing is independent of the length of the roller annular groove installing portion. Since the direction interval can be shortened, the elongation of the right roller end portion 21c1 can be reduced even with the same thrust load, and the axial clearance in the thrust bearing can be suppressed while maintaining the preload of the thrust bearing at an appropriate level. As described above, there is an effect that the rattling of the rod can be suppressed while maintaining a highly efficient operation.

  In this embodiment, the roller thrust bearing is a ball bearing in which the rolling element is a ball, but may be a line contact type rolling bearing having a roller or a needle as the rolling element. As a result, the capacity can be greatly increased. Furthermore, if a rolling bearing is used and a plain bearing made of a lubricant such as oil injected between the opposing surfaces and the opposing surfaces is used, a further increase in capacity can be realized.

  A pipe portion 3x extends on the right side of the right holder end plate 3c, and a rotor 5a, which is a component of the motor 5, is fixedly disposed on the pipe portion 3x in advance. Next, the roller left end portions 21c2 to 23c2 are inclined with respect to the center axis of the holder member, passed through the roller insertion hole 3y penetrating the left holder end plate 3b, and then fitted with the left roller radial bearings 21f2 to 23f2. .

  With this configuration and assembly procedure, when passing the roller left end through the roller insertion hole 3y (when assembling a plurality of rollers erected in different directions with respect to the right holder end plate 3c into the left holder end plate 3b ) Passes the cylinder (roller left end portion 21c2) of the inner diameter of the left roller radial bearing through the hole of the outer diameter of the left roller radial bearing. As a result, the large difference in diameter between the two allows holes to be passed, which has the effect of facilitating the assembly of this embodiment. Further, when such a procedure is not used, a means for inserting each roller from the outer peripheral side of the holder end plate can be considered. In this case, a means for closing the groove connected to the outer periphery essential as the insertion path is required. If the holder member is of a type that rotates as in this embodiment, it must resist the centrifugal force acting on the roller, and the means for closing the groove requires a more robust configuration.

  Thereafter, the bearing inner ring is fixed by the radial lock nuts 21k to 23k, and at the same time, the bearing outer ring is elastically supported via the preload ring springs 21k1 to 23k1 having high slidability in order to preload the left roller radial bearing 21f2. Here, the reason why the preload ring spring 21k1 has slidability is to reduce the friction loss due to the relative speed with the outer ring. In this way, the holder end plates 3b and 3c pivotally supported at both ends of the roller are connected by the holder connecting portion 3d to form the holder member 3. Here, since the holder connecting portion 3d of this embodiment is integrated with the left holder end plate 3b, there is an effect that the rigidity is high and the weight can be reduced.

  The holder connecting portion 3d and the right holder end plate 3c are fastened with a holder connecting screw 3g. Thereby, the central axis (hereinafter referred to as roller axis) 21d, 22d, 23d of the roller has an axial angle equal to or greater than the lead angle of the rod thread 1a relative to the central axis (hereinafter referred to as rod axis) 1d of the rod. Twist arranged. In this way, a sub-assembly of the roller and the holder member is manufactured. Here, all the roller bearings (mainly thrust bearings) of the subassembly have an outermost diameter equal to or larger than the diameter of the bottom of the annular groove of the roller (the outermost diameter of the thrust bearing is smaller than the bottom of the annular groove of the roller). Is protruding from the roller shaft). The reason why this is possible is that the roller shaft is twisted with respect to the rod shaft, so the installation location of the bearing is away from the closest point (point A shown in FIG. 2) of both shafts of the roller and rod. This is because the outermost diameter portion of the bearing and the peak portion of the rod do not come into contact with each other, and it is possible to install a bearing having a larger diameter. A bearing having a large outer diameter has an effect of increasing the force handled by the apparatus because the load capacity increases.

  When such an assembly is used as the rotation / linear motion conversion mechanism according to the present embodiment, the generated thrust increases. Of course, even if the diameter of the bearing is smaller than the diameter of the roller annular groove bottom, there is no problem in the operation of the apparatus.

  As shown in FIG. 3, the annular grooves provided in each roller are provided while shifting the arrangement position in the axial direction. In this embodiment, since the rollers are arranged at equal angular intervals around the rod 1, the annular groove 22b of the roller 22 is shifted to the right by P / 2 from the annular groove 21b of the roller 21, and the annular groove 23b of the roller 23 is Shift to the right by P from the annular groove 21b. The axial position of these annular grooves when assembling the mechanism is determined by the shift amount of each roller, the thickness of the roller thrust bearing, the length of the roller radial bearing, the axial position of the holder member where the thrust bearing is fixed, and the like. . For this reason, it is extremely difficult to cope with ensuring the positional accuracy in the axial direction when assembling the mechanism of the roller annular groove by increasing the precision of these related dimensions and positions due to overlapping errors.

  Therefore, in this embodiment, the roller and the holder are attached to the roller mounting screws 21m to 23m, and a roller slide mechanism capable of adjusting the axial position of the roller by turning the outer ring of the right roller radial bearing provided with the screw. Yes. As a result, there is an effect that the meshing state of the plurality of rollers and the rod can be improved. As will be described later, this adjustment is performed with the rod 1 screwed into the subassembly. After the adjustment, the C-shaped roller lock members 21n to 23n obtained by cutting out the rod side from the ring shape are caulked to fix the axial position of the roller. Further, without using the roller lock member 21n, an adhesive may be poured into the roller mounting screws 21m to 23m and fixed. As a result, the extremely difficult dimension management described above is not necessary, and there is a specific effect that the manufacturing cost can be greatly reduced. The holder member is also threaded corresponding to the mounting screw 21m provided on the outer ring of the right roller radial bearing 21f1. Alternatively, the roller mounting screw may be eliminated and a gap fit with a very small gap may be used as a roller slide mechanism, which may be fixed by adhesion or caulking.

  In addition, the roller lock member 21n is formed in a C shape by increasing the outer diameter of the roller thrust bearing to a position close to the outer diameter of the thread of the rod 1, maximizing the bearing load capacity, and the thrust load acting from the bearing race. This is to make the distance that the line is off as small as possible. The latter is for minimizing the thrust load reaction force and the torque generated by the thrust load, and to suppress the concentration of the load generated in each part of the bearing and the newly generated load in order to cancel it.

  Further, since the left roller radial bearings 21f2 to 23f2 are not fixed to the left holder end plate 3b, the roller can be moved in the axial direction of the roller, and a central bearing ring (roller mounting screw 21 provided as a fixing portion to the holder member is provided. Even if the outer ring is moved in the roller axis direction (by turning the center race), the preload of the left roller radial bearing is not affected. As a result, adjustment of the axial position of the roller can be performed only on the right holder end plate 3c side, and there is an effect that assembly is facilitated.

  Next, the left holder radial bearing 3f2 and the left holder thrust bearing 3e2 are mounted on the left holder end plate 3b of the sub-assembly of the rollers 21, 22, 23 and the holder member 3 (see FIGS. 4 and 5). Is inserted into the left casing 6a. At this time, a preload is applied to the left holder radial bearing 3f2 by the left leaf spring 3p. Thereafter, the right plate radial bearing 3f1 is inserted between the right holder end plate 3c and the left casing 6a after mounting the right leaf spring 3q for applying a preload. Further, the right holder thrust bearing 3e1 is mounted on the left casing 6a by caulking or bonding the bearing retainer 4. At this time, the bearing retainer 4 is fixed at a position where the holder member 3 rotates most smoothly. Thereby, the sub-assembly of the roller and the holder member is fixed to the left casing 6a in a rotatable state.

  Here, the left rack rod rail 9a is fixedly disposed in the narrowed portion of the left casing 6a. The inner diameter is set to be slightly larger than the outer diameter of the rod 1, and the central axis is set with high accuracy and coaxiality with the inner diameter on which the holder radial bearing is mounted. Of course, the left rack rod rail 9a may be the narrow portion itself of the left casing 6a.

  Next, the rod 1 is screwed into the sub-assembly of the roller, the holder member 3 and the left casing. At this time, the rotation of the holder member 3 may be fixed and the rod 1 may be rotated. Conversely, the rotation of the rod 1 may be fixed and the holder member 3 may be rotated. Thereby, the rod thread 1a and the roller annular grooves 21b to 23b are engaged with each other. At this time, since the position of the roller in the axial direction is not adjusted, there is a possibility that interference occurs at the meshing portion.

  As countermeasures, it is conceivable to make the sub-assembly shape of the holder member 3 and the rollers 21 to 23 uncertain, or to make rough position adjustment before this. As a specific method of the former, there is a method of loosening the holder connecting screw 3g and the thrust lock nuts 21j to 23j. On the other hand, as a specific method of the latter, before the rod 1 is screwed, it is possible to screw a dummy rod having a screw thread width smaller than a normal dimension while being the same lead as the rod screw. In addition, it is possible to roughly adjust the axial position of the roller. Then, by rotating the central race of each roller with respect to the holder member 3, the axial position of the roller is adjusted with a roller mounting screw.

  Next, the specific adjustment procedure will be described. (1) Restrain the rotation of the holder member 3. (2) While rotating the rod 1 while detecting the torque, the central track ring of one roller is rotated with respect to the holder member 3 so that the torque is minimized, and the axial position of the roller is set with the roller mounting screw. adjust. (3) Adjust the axial position of the other rollers in the same manner. (4) A constant thrust is applied to the rod in one direction, and the above steps (2) and (3) are performed again.

  Subsequently, thrust in the opposite direction to (5) and (4) is applied to the rod 1, and the rod 1 is turned in the same manner, and it is confirmed that the torque required for rotation is as small as that in (4). If it is larger, repeat from (4). (6) The position of each roller in the axial direction is fixed by the roller lock members 21n to 23n.

  In the above-described procedure, the positions of all the rollers were adjusted, but the last one need not be performed. In principle, the adjustment is possible, so that the assembly process can be shortened and the cost can be reduced. There is. Further, since (4) can be adjusted to some extent without performing it, there is an effect that the assembly process can be shortened and the cost can be reduced. On the other hand, if the subassembly shape of the holder member 3 and the rollers 21 to 23 is indeterminate prior to this adjustment, the uncertainty of the subassembly shape is resolved before proceeding to the stage (4). Therefore, the holder connecting screw 3g and the thrust lock nuts 21j to 23j are tightened. As a method for facilitating the adjustment of the roller position, which has been described in detail as described above, it is possible to make the rod screw thread and the roller annular thread easy to bend and to enlarge the appropriate range of the roller position. As a concrete plan, it is possible to make a crack at the top of a screw thread or an annular thread, or to insert an elastic body such as rubber or a corrugated spring into the crack.

  Next, the right casing 6b in which the stator 5b is press-fitted or shrink-fitted is put on the assembly so far from the right side, and both the casings 6a and 6b are connected by screwing or the like. As a result, the stator 5b and the rotor 5a face each other to form the motor 5. Similar to the left rack rod rail 9a in the left casing 6a, the right rod rail 9b is provided near the end of the right casing 6b. The inner diameter of the rod 1 is slightly larger than the outer diameter of the rod 1, and the surface finish is machined to such a level that the rod 1 is not damaged even if it is rubbed.

  Here, in the above assembly, grease is appropriately poured between the component parts. By the way, in order to cause the rotation / linear motion converting operation, a linear motion pair that prevents the rotation of the rod 1 that is the linear motion portion and permits only the linear motion is necessary. In the present embodiment, the rack that meshes with the pinion 103 of FIG. 15 and the pinion 103 provided on the rod 1 plays the role. In the case of a system without this, for example, in a steer-by-wire system, it is necessary to separately provide a linear motion pair such as a ball spline. In the case of a steering mechanism such as this time, even if the ball is omitted and the sliding pair is even, the speed of the linear motion part is small, so the efficiency drop is small. Therefore, when cost is important, a simple structure such as a spline joint may be used. This is generally the case when the required speed at the linear motion part is small in applications other than the steering mechanism.

  Next, the operation of this embodiment will be described with reference to FIG. FIG. 16 is a developed view of the outer peripheral surface of the rod 1 in order to explain the operation principle. Now consider only the case where the motor rotates from top to bottom in FIG. The holder member rotates around the rod shaft, and the three rollers held by the holder member rotate in the same manner as the motor. Therefore, in FIG. 16, the roller moves vertically from the top (A position) to the bottom (B position). The thick line in FIG. 16 shows the right rod thread flank when the roller is in the A position. Then, a case is considered in which the roller revolves by δ radians (rad) from the position A and moves on the circumference of the rod by δ · (rack shaft radius) to reach the position B.

  At this time, the position of the right roller annular groove surface does not move in the rod axis direction, but moves only in the vertical direction on the development view. Therefore, if the rod moves by δ ・ (rod shaft radius) ・ tan (rod screw lead angle) in the axial direction (left and right in the developed view), the right rod thread flank moves to the left and becomes the position of the broken line , Keep the roller annular groove and rod thread meshing. In this way, rotation / linear motion conversion occurs.

  Further, the rack movement amount M per rotation of the motor (hereinafter referred to as a mechanism pitch) is M = 2π · (rod shaft radius) · tan (rod screw lead angle), where δ is 2π. As is apparent from this equation, it is understood that the deceleration rate can be increased by reducing the rod screw lead angle. Further, the meshing portion is an annular groove surface on the roller side and a thread flank on the rod side, and meshes between surfaces having a small curvature. Therefore, since contact occurs over a wide range due to elastic deformation at the time of meshing, the maximum value of the generated stress (Hertz stress) is suppressed. For this reason, there is an effect that a load per meshing portion increases, and a large thrust can be generated while being compact.

  Further, at the meshing portion, a frictional force acts in a direction in which relative slip is eliminated, that is, a direction in which the sliding is performed integrally. This friction force causes the roller to rotate so that the roller annular groove rolls on a rail called a rod thread. What is important here is that even if the roller rotates, the roller groove does not move in the axial direction at the meshing portion. This is realized because the roller groove is not a screw but an annular groove. Thus, since the roller controls its own rotation speed so as to reduce the sum of friction at all meshing locations, the roller has an effect of reducing loss and increasing efficiency. Moreover, it becomes possible to use a commercially available thrust bearing or radial bearing, and there is an effect of cost reduction.

  Next, a rotation / linear motion conversion mechanism according to a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is an enlarged cross-sectional view of the right roller end portion (M portion) of FIG. 1 or FIG. 4 (representing the roller 21 as well as the other rollers 22 and 23). For the bearing that receives the left thrust load and the right thrust load of the roller, the holder fixing side bearing ring that is fixed to the holder member is integrated as the center side bearing ring 21e0, and is arranged on the right side and rotated together with the roller. The rotation-side right race ring 21e1 and the left-side rotation-side left race ring 21e2 are configured (the difference between the two becomes clear when the configuration of FIG. 6 showing the first embodiment is compared with the configuration of FIG. 8). ). Except for providing the roller mounting screw 21m on the outer periphery of the central bearing ring and the right roller radial bearing 21f1 on the inner periphery, it is the same as the first embodiment already described. Description is omitted.

  The second embodiment can be regarded as the limit in which the bearing rings of the thrust bearing on the side fixed to the holder member are back to back. Therefore, since the installation interval in the axial direction of both roller thrust bearings is extremely small, there is an effect that it is possible to further suppress the occurrence of rattling during an impact reversal load. Further, in the second embodiment, since a needle-type right roller radial bearing is also provided on the central raceway ring, the bearing group that pivotally supports the right end of the roller is compactly integrated, and the mechanism can be reduced in size. There is also.

  Next, a rotation / linear motion conversion mechanism according to a third embodiment of the present invention will be described with reference to FIG. FIG. 9 is an enlarged cross-sectional view of the left roller end portion (N portion) of the roller 21 of FIG. 1 or FIG. 4 (representing the roller 21 as well as the other rollers 22 and 23). Since the left roller radial bearing is the same as that of the first or second embodiment described above except that the left roller radial bearing is a needle or roller bearing, the description of the structure, operation, and effects of other parts is omitted. The structure shown in FIG. 9 eliminates the need for preload on the bearing, eliminates the need to press the spring against the outer ring with the radial lock nut 21k, and avoids the friction loss that has occurred there, thereby improving the performance.

  Even if this outer ring is fixed to the left holder end plate 3b by bonding or the like, relative movement in the axial direction is possible between the outer ring (needle) or between the inner ring (needle). Even if it is performed with the roller mounting screw 21m at the right end of the roller, no problem occurs. As a result, since the posture of the left roller radial bearing 21f2 is stabilized and the posture of the roller is also stabilized, for example, even if the operation direction of the apparatus is suddenly reversed, the bearing posture is not twisted in the roller insertion hole 3y. There is an effect that good rotation of the roller can be always maintained. The same effect can be obtained by fixing the outer ring not by adhesion but by a convex portion on the inner surface of the roller insertion hole or a lock member.

  Next, a rotation / linear motion conversion mechanism according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 10 is an enlarged cross-sectional view of the right roller end portion (M portion) of the roller 21 of FIG. 1 or FIG. 4 (representing the roller 21 as well as the other rollers 22 and 23). The center and left and right race rings 21e5, 21e6, 21e7 are the same as those in the first embodiment except that tapered roller bearings are installed and the dedicated radial bearings are eliminated. A description of the structure, operation, and effects of the portions is omitted. Since the roller thrust bearing is a roller bearing based on line contact, its capacity can be greatly increased without changing the dimensions of each part (especially without increasing the outer diameter), enabling the capacity of the device to be increased. Has the effect of

  In particular, when the configuration example shown in FIG. 10 is used as a rotation / linear motion conversion mechanism, there is an effect of enabling large thrust. Further, since the taper bearing is used, there is no need for a dedicated right roller radial bearing for receiving a radial load, the structure is simplified, and there is an effect that the size can be reduced. Furthermore, it is possible to add alignment, and in this case, there is an effect of alleviating problems caused by deterioration of the axial accuracy of the roller mounting screw 21m and the roller insertion hole 3y (see FIGS. 7 and 9).

  Next, a rotation / linear motion conversion mechanism according to a fifth embodiment of the present invention will be described with reference to FIGS. 2, 3, 11, 12 and 13. FIG. 2 is a longitudinal sectional view of a rack assist mechanism of an electric power steering apparatus to which the fifth embodiment of the present invention is applied, and also depicts a roller coming in front. FIG. 3 is a side view of all the rollers. 11 is a longitudinal sectional view of a roller holder coupling assembly in which the roller and the holder coupling member are integrated, FIG. 12 is a side view of the roller and holder member subassembly, and FIG. 13 is a transverse section of the same subassembly. FIG. Since it is the same as that of 1st thru | or 4th Embodiment except the structure of a revolution roller and a holder member, the description about the structure of another part, operation | movement, and an effect is abbreviate | omitted. Here, although three rollers 21 to 23 are installed, since their configurations are the same, the roller 21 will be described as a representative.

  In the first to fourth embodiments of the present invention, the roller is solid, whereas in the fifth embodiment, as shown in FIG. A hollow body with a through hole is formed, and a shaft fixed to the holder member (also used as the holder connecting portion 3m in the example of FIG. 11) is inserted into the hollow body. Since the roller needs to be rotatably supported with respect to the holder member, a bearing is disposed between the shaft and the roller. This shaft also serves as a holder connecting portion for connecting the both end plates 3b and 3c of the holder member 3 (hereinafter referred to as a roller built-in holder connecting portion 3m). When this embodiment is assembled, the roller 21 and the roller built-in holder are connected. The roller holder coupling assembly 210 in which the portion 3m and the associated roller bearings are integrated can be handled as one component. As a result, the assembly process of the roller bearing portion that requires adjustment and takes time can be assembled in parallel with the assembly process of the main body, and therefore there is an effect of improving the assemblability such as shortening the assembly time.

  In the fifth embodiment, a thrust bearing is disposed on the right side of the roller together with the right roller radial bearing 21f1 so as to receive a thrust load in both directions. This thrust bearing includes a rotation-side left race ring 21e2 and a rotation-side right race ring 21e1 that rotate together with the roller, a fixed-side central race ring 21e0 that is fixed to the roller built-in holder connecting portion 3m, and a thrust lock that applies an appropriate preload to them. It consists of a nut 21j. Thereby, the roller built-in holder connecting portion 3m becomes a member integrated with the holder fixing side race of the roller thrust bearing.

  Further, the rotation-side left race ring 21e2 is integrated with the outer ring of the right roller radial bearing 21f1, and has a compact configuration, contributing to downsizing. On the other hand, a left roller radial bearing 21f2 is arranged on the left side of the roller, and its outer ring is fixed to the roller by a radial lock nut 21k. Since the thrust bearings 21e and 21j are provided on one side rather than on both sides of the annular groove setting portion of the roller, the axial direction of both roller thrust bearings does not depend on the length of the annular roller groove setting portion as in the previous embodiments. Since the interval can be shortened, it is possible to suppress the axial clearance in the thrust bearing while maintaining the preload of the thrust bearing at an appropriate level. Thereby, there is an effect that it is possible to suppress the rattling of the rod while maintaining a highly efficient operation.

  The roller holder coupling assemblies 210, 220, and 230 assembled as described above are screwed into the right holder end plate 3c (see FIG. 12). Next, after inserting the left end portion of each roller assembly into the roller insertion hole 3y of the left holder end plate 3b, roller end plate connecting members 21s to 23s (22s and 23s are not shown) are inserted, and the roller built-in holder connection Screw in part 3m and fix. By this method, it is possible to fix a plurality of twisted shafts to the holder end plate as in the insertion of the left roller radial bearing in the first to fourth embodiments.

  In this state, the rod 1 is screwed and the roller built-in holder connecting portion 3m integrated with the roller fixed bearing ring of the roller thrust bearing is rotated to adjust the axial position of the roller, thereby adjusting the meshing state of the roller and the rod. To do. The detailed procedure is the same as that of the above-described embodiment. Thereafter, the roller holder coupling assemblies 210 to 230 and the right holder end plate 3c are fixed by the roller lock nut 21r. Thereafter, the outer diameters of the roller insertion hole 3y and the roller end plate connecting member are bonded. Of course, a structure that can be fixed by screws is also possible. The roller holder assembly is formed as described above. As a result, these roller shafts also serve as a holder connecting portion for connecting both the holder end plates 3b and 3c, and are therefore referred to as a roller built-in holder connecting portion 3f. In the present embodiment, since the other holder connecting portions are eliminated, at least the corresponding moment of inertia can be reduced.

  From the above, there is an effect that the response to the command is further improved and the controllability is improved. By the way, when a hole penetrating the inside of the roller is formed, there is a concern that the strength of the roller portion is lowered. However, if the thickness of the roller part is more than a certain level, the load at the bottom of the roller groove where the load is concentrated most hardly increases, and a decrease in the strength of the roller can be ignored. In the present embodiment, since the roller built-in holder connecting portion 3m having the necessary minimum diameter in strength is used as the holder connecting portion, there is a specific effect that the thickness of the roller portion can be set large and the roller strength can be secured. In short, in this embodiment, the center part of the roller, which is a useless part that does not contribute to improving the strength, is removed, and the holder connecting part essential for the rotation / linear motion conversion mechanism is passed through the hole to reduce the moment of inertia. It is. Here, in this embodiment, since the holder connecting portion is not provided other than the roller built-in holder connecting portion 3m, the interval between the rollers is increased. For this reason, it is possible to increase the number of rollers to be installed and to increase the thrust further.

  FIG. 14 shows an enlarged cross-sectional view (M portion shown in FIGS. 1 and 4) of the right roller bearing portion in the sixth embodiment of the present invention. As shown in FIG. 14, a roller roller bearing 21e9 (22e9, 23e9 is not shown) having a roller having substantially the same height and diameter as a rolling element and having a rolling surface at an angle of 45 degrees with respect to the rotation axis, You may provide instead of the bearing group of FIG.6, FIG.8, FIG.10. Here, the roller rolling elements to be installed are capable of receiving thrust loads and radial bearings in both directions by alternately changing their axial directions. As a result, since it receives a load by line contact, it can handle a large load and can receive a load in all directions with a single bearing, reducing the required dimensions in the axial direction and reducing the cost by reducing the number of parts. There is an effect.

  In the first to sixth embodiments of the present invention described above, the diameters of the rollers 21 to 23 are almost the same as the diameter of the rod 1, but as an embodiment of the present invention, as long as the strength permits, The diameter of the roller can be made smaller than the diameter of the rod. When the roller diameter is reduced, the number of rollers can be further increased, and this can cope with a case where a larger rack thrust is required. Conversely, the roller can be made thicker than the rod. In this case, since the shift of the meshing point locus after meshing between the roller and the rod becomes small in the meshing region in consideration of the elastic deformation at the meshing location, the generated slip becomes small and the meshing location becomes small. There is an effect that friction loss can be reduced.

  Also, the Young's modulus of both materials, the cross-sectional shape of both, and the number of rollers so that the axial rigidity of the rod and the axial rigidity of all rollers (sum of the axial rigidity of each installed roller) are approximately the same. May be determined. As a result, the elongation amount of the rod and the roller is approximately the same in each part, and the load at the meshing portion is almost equalized. Therefore, the reliability of the meshing portion is improved and the overall deformation amount (the elongation or contraction of the rod) Therefore, there is an effect that the operability of the apparatus is improved.

  As described above, the embodiment of the present invention mainly has the following configurations, functions and actions. That is, a rod having a threaded portion on the outer peripheral surface, a holder member provided on the outer peripheral side of the rod, provided to be rotatable relative to the rod and movable relative to the rod, and rotatably supported by the holder member And a roller having an annular groove that meshes with the threaded portion on the outer peripheral surface, and a roller that is twisted at an axial angle equal to or greater than the lead angle of the threaded portion with respect to the central axis of the rod. A roller bearing that rotatably supports the roller, and each roller thrust bearing that receives a thrust load in both directions in the axial direction thereof is arranged on one side of the roller annular groove installation portion, In addition, with this configuration, it is possible to improve controllability by suppressing rattling, improve reliability and efficiency, and generate large thrust.

It is a longitudinal cross-sectional view of the rack assist mechanism in the electric power steering device to which the rotation / linear motion conversion mechanism according to the first embodiment of the present invention is applied. It is a longitudinal cross-sectional view when the viewpoint of FIG. 1 is rotated 90 degrees (when looking down from the upper part of FIG. 1), and is a diagram depicting a roller coming to the near side. It is a side view of all the rollers in this embodiment. It is a side view (a part is sectional drawing and B1-B2-B3-B4 of FIG. 5) of the subassembly of the roller and holder member in 1st embodiment. It is a cross-sectional view (AA of FIG. 4) of the subassembly of the roller and holder member in 1st embodiment. It is an expanded sectional view (M section shown in Drawing 1 and Drawing 4) of the right roller bearing part in a first embodiment. It is an expanded sectional view (N section shown in Drawing 1 and Drawing 4) of the left roller bearing part in a first embodiment. It is an expanded sectional view (M section shown in Drawing 1 and Drawing 4) of the right roller bearing part in a second embodiment of the present invention. It is an expanded sectional view (N section shown in Drawing 1 and Drawing 4) of the left roller bearing part in a third embodiment of the present invention. It is an expanded sectional view (M section shown in Drawing 1 and Drawing 4) of the right roller bearing part in a 4th embodiment of the present invention. It is a longitudinal cross-sectional view of the roller holder coupling assembly in which the roller and the holder coupling member in the fifth embodiment of the present invention are integrated. It is a side view (a part is sectional drawing and BB of FIG. 13) of the subassembly of the roller and holder member in 5th embodiment. It is a cross-sectional view (AA of FIG. 12) of the roller and holder member subassembly in the fifth embodiment. It is an expanded sectional view (M section shown in Drawing 1 and Drawing 4) of a right roller bearing part in a 6th embodiment of the present invention. It is a figure which shows arrangement | positioning in the electric power steering apparatus of the rack assist mechanism to which the rotation linear motion conversion mechanism which concerns on embodiment of this invention was applied. It is a figure explaining operation | movement of the rotation linear motion conversion mechanism which concerns on embodiment of this invention.

Explanation of symbols

1: Rod 1a: Rod thread 1d: Rod shaft 21, 22, 23: Roller 21b, 22b, 23b: Roller groove (annular groove)
21d, 22d, 23d: Roller shaft 21e0, 22e0, 23e0: Fixed-side central raceway 21e1, 22e1, 23e1: Rotation-side right raceway 21e2, 22e2, 23e2: Rotation-side left raceway 21e3, 22e3, 23e3: Right roller thrust Bearings 21e4, 22e4, 23e4: Left roller thrust bearings 21e5, 22e5, 23e5: Fixed side central roller raceway 21e6, 22e6, 23e6: Rotation side right roller raceway 21e7, 22e7, 23e7: Rotation side left roller raceway 21e9, 22e9 23e9: Slider roller bearings 21f1, 22f1, 23f1: Right roller radial bearings 21f2, 22f2, 23f2: Left roller radial bearings 21m, 22m, 23m: Roller mounting screws 3: Holder member 3e1: Right holder thrust bearing 3e2: Left ho Dasurasuto bearing 3f1: right holder radial bearing 3f2: left holder radial bearings 3m: roller built holder connecting part 5: motor 6: casing 103: pinion 107: rack assist mechanism 210, 220, 230: roller holder coupling assembly

Claims (10)

A rod having a threaded portion on the outer peripheral surface, a holder member provided on the outer peripheral side of the rod so as to be rotatable relative to the rod and movable relative to the rod, and rotatably supported by the holder member A rotary linear motion conversion mechanism comprising: an annular groove that engages with the screw portion on an outer peripheral surface, and a roller that is twisted and arranged at an axial angle equal to or greater than a lead angle of the screw portion with respect to a central axis of the rod. There,
A one-way roller thrust bearing that rotatably supports the roller and receives a thrust load in one direction of the roller shaft; and a two-way roller thrust bearing that receives a thrust load in the other direction of the roller shaft;
The one-way roller thrust bearing and the other-direction roller thrust bearing are both arranged only at one end adjacent to the annular groove installation portion of the roller. In claim 1,
The one-way and other-direction roller thrust bearings include a holder member fixed side raceway, a roller fixed side raceway, and rolling elements between both raceways,
The rotary linear motion conversion mechanism, wherein the holder member fixed side bearing ring of the one-way roller thrust bearing and the holder member fixed side bearing ring of the other direction roller thrust bearing are arranged back to back. In claim 1 or 2,
The holder between the holder member and at least one of the holder member fixed side races of the roller thrust bearings in the one direction and the other direction, or a structure that operates integrally with the holder member fixed side races A rotation / linear motion conversion mechanism characterized in that a roller slide mechanism is provided that enables the roller incorporated in a member to be changed and fixed in a state where the roller is engaged with the rod. In claim 2,
Along with the roller between the one-way roller thrust bearing and the other-direction roller thrust bearing, operates integrally with at least one of the holder member fixed-side bearing rings of the both roller thrust bearings or the holder member fixed-side bearing ring Provide a roller mounting screw to the holder member in the structure to be
A rotation / linear motion conversion mechanism characterized by changing and fixing the axial position of the roller by adjusting the roller mounting screw in a state where the roller incorporated in the holder member is engaged with the rod. In claim 3 or 4,
The rotation / linear motion conversion mechanism according to claim 1, wherein the structure is an outer ring of a roller radial bearing that operates integrally with any one of the one-way roller thrust bearing and the other-direction roller thrust bearing. In claim 1,
The one-way and other-direction roller thrust bearings include a holder member fixed side raceway, a roller fixed side raceway, and rolling elements between both raceways,
The rotary linear motion conversion mechanism, wherein the holder member fixed side bearing ring of the one-way roller thrust bearing and the holder member fixed side bearing ring of the other direction roller thrust bearing are composed of the same common structure. In claim 1,
A roller end shaft is provided at the other end of the roller where the one-way roller thrust bearing and the other-direction roller thrust bearing are not disposed,
A radial bearing for supporting the roller in a radial manner is provided by an outer peripheral surface of the roller end shaft and an inner peripheral surface of a roller insertion hole provided in the holder member and inclined with respect to the rod central axis. Rotary linear motion conversion mechanism. In any one of claims 1 to 6,
The rotary linear motion conversion mechanism characterized in that an outer diameter of the roller thrust bearing or the roller bearing including the roller thrust bearing is equal to or larger than a diameter of a bottom portion of the roller annular groove. A rod having a threaded portion on the outer peripheral surface, a holder member provided on the outer peripheral side of the rod so as to be rotatable relative to the rod and movable relative to the rod, and rotatably supported by the holder member A rotary linear motion conversion mechanism comprising: an annular groove that engages with the screw portion on an outer peripheral surface, and a roller that is twisted and arranged at an axial angle equal to or greater than a lead angle of the screw portion with respect to a central axis of the rod. There,
A unidirectional roller bearing that rotatably supports the roller and receives a thrust load in one direction of the roller shaft; and a bidirectional roller bearing that receives a thrust load in the other direction of the roller shaft;
The one-way roller bearing and the other-direction roller bearing are both arranged only at one end adjacent to the annular groove setting portion of the roller,
The one-way roller bearing and the other-direction roller bearing are configured to perform a function of a radial bearing of the roller in addition to a thrust bearing function of the roller. In claim 1 or 9,
At least one of the one-way roller bearing and the other-direction roller bearing that plays the role of receiving the thrust load is a line contact type rolling bearing or a sliding bearing with a lubricant interposed therebetween. Dynamic conversion mechanism.

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