JP2008309218A - Screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw device usable over a long period even when a relatively great axial load acts on a planetary roller and it operates thereon from one direction. <P>SOLUTION: In the screw device, the pitch of a roller side screw portion 6 formed on the outer peripheral face of the planetary roller is smaller than the pitch of a screw portion crossing the roller side screw portion 6 and meshing therewith, out of a shaft side screw portion 4 formed on the outer peripheral face of a screw shaft and a nut side screw portion 5 formed on the inner peripheral face of a nut. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a screw device used in an injection molding machine, a press molding machine, an automobile actuator, or the like as a mechanical element that converts rotational motion into linear motion, and in particular, a plurality of planetary rollers are provided between a screw shaft and a nut. The present invention relates to a screw device.

As a screw device having a plurality of planetary rollers between a screw shaft and a nut, one described in Patent Document 1 has been known. This type of screw device includes a screw shaft, a nut having an inner peripheral surface facing the outer peripheral surface of the screw shaft, and a plurality of planetary rollers provided between the screw shaft and the nut. On the outer peripheral surface of the planetary roller, a male screw (hereinafter referred to as “roller side screw portion”) is formed. This roller-side threaded part consists of a male thread formed on the outer peripheral surface of the screw shaft (hereinafter referred to as “shaft-side threaded part”) and a female thread formed on the inner peripheral surface of the nut (hereinafter referred to as “nut-side threaded part”). For example, if the absolute value of the lead angle of the roller side screw part is the same as the absolute value of the lead angle of the shaft side screw part and the twist direction of the roller side screw part is the same as the twist direction of the shaft side screw part, or a roller When the lead angle absolute value of the side screw portion is different from the lead angle absolute value of the shaft side screw portion, the roller side screw portion intersects the shaft side screw portion and meshes therewith. Also, when the lead angle absolute value of the roller side thread is the same as the absolute angle of the nut side thread, and the twist direction of the roller side thread is opposite to the twist direction of the nut side thread, or the lead of the roller side thread When the absolute angle value is different from the absolute value of the lead angle of the nut-side threaded portion, the roller-side threaded portion intersects and meshes with the nut-side threaded portion. Therefore, in such a screw device, the above-described cross engagement exists between the screw shaft and the planetary roller or between the nut and the planetary roller.
US Pat. No. 2,683,379

  However, in the above-described screw device, conventionally, as shown in FIG. 17, the pitch of the roller side screw portion 6 is the same as the pitch of the shaft side screw portion 4 and the nut side screw portion 5. For this reason, for example, cross engagement exists between the screw shaft and the planetary roller, and both the shaft-side screw portion formed on the outer peripheral surface of the screw shaft and the roller-side screw portion formed on the outer peripheral surface of the planetary roller are both. In the case of a right-hand thread, as shown in FIG. 18 (a), when an axial load in the direction indicated by the arrow acts on the screw shaft 1 and an axial load in the opposite direction acts on the planetary roller 3, the roller A force (counterclockwise force in the drawing) that causes the groove of the side screw portion 6 to coincide with the groove of the shaft-side screw portion 4 is generated on the planetary roller 3, so that the planetary roller 3 is moved against the screw shaft 1. Will have a tilt. When the planetary roller 3 is inclined with respect to the screw shaft 1, as shown in FIG. 19, the contact surface pressure between the screw shaft 1 and the planetary roller 3 is reduced at a portion on the left side of the central portion in the axial direction of the planetary roller 3. The cross-engagement point P of the shaft side screw portion 4 and the roller side screw portion 6 moves in the downward direction (the lower side in the figure), and the screw shaft 1 and the planetary roller at the portion on the right side of the center portion in the axial direction of the planetary roller 3. The cross meshing point P between the shaft side screw portion 4 and the roller side screw portion 6 moves in the direction in which the contact surface pressure with the roller 3 increases (upper side in the figure). As a result, the contact surface pressure between the screw shaft 1 and the planetary roller 3 decreases toward the left side in the figure. However, since the axial load received by the entire planetary roller does not change, the screw shaft 1 and the planetary roller 3 As shown in FIG. 20, the contact surface pressure increases toward the right side in the figure. For this reason, when there is a cross meshing between the screw shaft 1 and the planetary roller 3, the contact surface pressure non-uniformity as shown in FIG. 18B is between the screw shaft 1 and the planetary roller 3. When the axial load acting on the planetary roller is relatively large and the axial load acts on the planetary roller from one direction as in an injection molding machine, for example, the damage develops from one end of the planetary roller. There is a problem that the actual life of the screw device is shorter than the value calculated for the life of the screw device on the assumption that the load is uniformly distributed.

  In addition, when cross-engagement exists between the nut and the planetary roller, both the nut-side thread formed on the inner peripheral surface of the nut and the roller-side thread formed on the outer peripheral surface of the planetary roller are right-handed. As shown in FIG. 21A, when an axial load in the direction indicated by the arrow acts on the nut 2 and an axial load in the opposite direction acts on the planetary roller 3, The planetary roller 3 is inclined with respect to the nut 2 when a force (clockwise force in the figure) is generated on the planetary roller 3 so as to match the groove with the groove of the nut-side screw portion 5. . When the planetary roller 3 is inclined with respect to the nut 2, the nut-side screw portion 5 and the nut-side screw portion 5 are arranged in the direction in which the contact surface pressure between the nut 2 and the planetary roller 3 increases in the portion on the left side of the central portion in the axial direction of the planetary roller 3. The cross-engagement point with the roller-side threaded portion 6 moves, and the nut-side threaded portion 5 and the roller are moved in the direction in which the contact surface pressure between the nut 2 and the planetary roller 3 decreases at the right side of the axial center of the planetary roller 3. The intersection point with the side screw portion 6 moves. As a result, the contact surface pressure between the nut 2 and the planetary roller 3 decreases toward the right side in the figure, but the axial load received by the entire planetary roller does not change, so the contact surface between the nut 2 and the planetary roller 3 does not change. The pressure rises toward the left side in the figure. For this reason, when there is a cross-engagement between the nut 2 and the planetary roller 3, the contact surface pressure non-uniformity occurs between the nut 2 and the planetary roller 3 as shown in FIG. In the case where the axial load acting on the planetary roller is relatively large and the axial load acts on the planetary roller from one direction, such as an injection molding machine, the damage develops from one end of the planetary roller, and the load There is a problem that the actual life of the screw device becomes shorter than the value calculated for the life of the screw device on the assumption that is uniformly distributed.

  The present invention has been made by paying attention to the above-mentioned problems, and its purpose is to maintain a relatively long axial load acting on the planetary roller and for a long time even when the axial load acts on the planetary roller from one direction. It is to provide a screw device that can be used.

  In order to solve the above-mentioned problem, a screw device according to the first aspect of the present invention is a screw device comprising a plurality of planetary rollers between a screw shaft and a nut, and a roller formed on an outer peripheral surface of the planetary roller. The pitch of all or part of the side screw portion intersects the roller side screw portion of the shaft side screw portion formed on the outer peripheral surface of the screw shaft and the nut side screw portion formed on the inner peripheral surface of the nut. Thus, the pitch is smaller than the pitch of the threaded portions that mesh with each other.

The screw device according to a second aspect of the present invention is the screw device according to the first aspect, wherein a pitch of a screw portion that meshes with the shaft side screw portion and the nut side screw portion without intersecting the roller side screw portion is determined. The pitch is the same as the pitch of the roller side thread portion.
A screw device according to a third aspect of the present invention is the screw device according to the first aspect, wherein a pitch of a screw portion that meshes without intersecting the roller side screw portion of the shaft side screw portion and the nut side screw portion is determined. The pitch is the same as the pitch of the threaded portion that intersects and meshes with the roller side threaded portion.

  A screw device according to a fourth aspect of the present invention includes a plurality of planetary rollers between a screw shaft and a nut, and the planetary rollers are formed on an outer peripheral surface of the screw shaft and an inner peripheral surface of the nut. In the screw device having a small-diameter shaft portion that does not engage with the screw portion in the center portion, the shaft-side screw portion formed on the outer peripheral surface of the screw shaft and the nut-side screw portion formed on the inner peripheral surface of the nut. When the pitch of the threaded portion that intersects and meshes with the roller side threaded portion formed on the outer peripheral surface of the planetary roller is P, an integer multiple of the pitch is N, and a positive value smaller than the pitch of the threaded portion is Δx, The roller-side thread portion pitch is P, and the distance between the thread grooves of adjacent roller-side thread portions across the small-diameter shaft portion is P × N−ΔX.

The screw device according to a fifth aspect of the present invention is the screw device according to the fourth aspect, wherein a central portion of a screw portion that meshes with the shaft side screw portion and the nut side screw portion without intersecting the roller side screw portion. Is made smaller than the pitch of the roller side threaded portion.
The screw device according to a sixth aspect of the present invention is the screw device according to any one of the first to fifth aspects, wherein the nominal effective diameter of the shaft side screw portion is Ds, and the nominal effective diameter of the nut side screw portion is Dn, the nominal effective diameter of the roller side threaded portion Dr, the number of threads of the shaft side threaded portion Js, the number of threads of the nut side threaded portion Jn, the number of threads of the roller side threaded portion Jr, the shaft side The nominal lead of the screw portion is Ls, the nominal lead of the nut side screw portion is Ln, the nominal lead of the roller side screw portion is Lr, the nominal pitch of the shaft side screw portion is Ps, and the nominal pitch of the nut side screw portion is Pn, where the nominal pitch of the roller side thread portion is Pr, Dn = Ds + 2Dr, Jn / Jr = Dn / Dr, Jn = Js, Ls = Js × Ps, Lr = Jr × Pr, Ln = Jn × Pn A relationship is established, and the shaft-side screw portion is Meshes with crosses the over La-side thread portion, wherein the shaft-side thread portion of the lead is consistent with the amount of movement of the nut.

  A screw device according to a seventh aspect of the present invention is the screw device according to any one of the first to fifth aspects, wherein the nominal effective diameter of the shaft-side screw portion is Ds, and the nominal effective diameter of the nut-side screw portion is Dn, the nominal effective diameter of the roller side threaded portion Dr, the number of threads of the shaft side threaded portion Js, the number of threads of the nut side threaded portion Jn, the number of threads of the roller side threaded portion Jr, the shaft side The nominal lead of the screw portion is Ls, the nominal lead of the nut side screw portion is Ln, the nominal lead of the roller side screw portion is Lr, the nominal pitch of the shaft side screw portion is Ps, and the nominal pitch of the nut side screw portion is Pn, where the nominal pitch of the roller side thread portion is Pr, Dn = Ds + 2Dr, Js / Jr = Ds / Dr, Jn = Js, Ls = Js × Ps, Lr = Jr × Pr, Ln = Jn × Pn And the nut side threaded part It meshes with crosses the serial roller side thread portion, wherein the shaft-side thread portion of the lead is consistent with the amount of movement of the nut.

  The screw device according to an eighth aspect of the present invention is the screw device according to the first aspect, wherein the roller-side screw portion and the nut-side screw portion are annular grooves having a lead angle of zero, and the roller-side screw portion is the The shaft-side threaded portion intersects and meshes.

  According to the screw device according to the first to eighth aspects, even if the planetary roller is inclined, the contact surface pressure of the roller side screw portion is substantially uniform in the axial direction, so that the axial load acting on the planetary roller is relatively low. Even when a large and axial load acts on the planetary roller from one direction, it can be used over a long period of time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a screw device according to a first embodiment of the present invention, and FIG. 2 is a diagram showing a main part of the screw device according to the first embodiment, as shown in FIG. The screw device according to the first embodiment includes a screw shaft 1, a nut 2, and a plurality of planetary rollers 3.
The planetary roller 3 is provided between the screw shaft 1 and the nut 2, and the outer peripheral surface of each planetary roller 3 is provided on the outer peripheral surface of the screw shaft 1 and the inner periphery of the nut 2. A roller-side thread portion 6 is formed that meshes with both of the nut-side thread portions 5 formed on the surface. The planetary roller 3 has pinion gears 7 at both ends in the axial direction, and two internal gears 8 that mesh with the pinion gears 7 are fixed on the inner peripheral surface of the nut 2.

  Here, the nominal effective diameter of the shaft-side screw portion 4 is Ds, the nominal effective diameter of the nut-side screw portion 5 is Dn, the nominal effective diameter of the roller-side screw portion 6 is Dr, the number of threads of the shaft-side screw portion 4 is Js, The number of threads of the nut-side threaded portion 5 is Jn, the number of threads of the roller-side threaded portion 6 is Jr, the nominal lead of the shaft-side threaded portion 4 is Ls, the nominal lead of the nut-side threaded portion 5 is Ln, and the roller-side threaded portion 6 If the nominal lead is Lr, the nominal pitch of the shaft side screw portion 4 is Ps, the nominal pitch of the nut side screw portion 5 is Pn, and the nominal pitch of the roller side screw portion 6 is Pr, then Dn = Ds + 2Dr, Jn / Jr = Dn / Dr, Jn = Js, Ls = Js × Ps, Lr = Jr × Pr, and Ln = Jn × Pn.

Further, the roller side threaded portion 6 intersects and meshes with the shaft side threaded portion 4, and when the pitch of the shaft side threaded portion 4 is P and a positive value smaller than the pitch of the shaft side threaded portion 4 is ΔP, FIG. As shown in FIG. 4, the roller side screw portion 6 is formed on the outer peripheral surface of the planetary roller 3 with a pitch smaller than the pitch of the shaft side screw portion 4.
The nut-side threaded portion 5 meshes with the roller-side threaded portion 6 without intersecting. If the pitch of the roller-side threaded portion 6 is P−ΔP, as shown in FIG. It is formed on the inner peripheral surface of the nut 2 at the same pitch as the portion 5.

  If the pitch (P−ΔP) of the roller-side screw portion 6 is made smaller than the pitch (P) of the shaft-side screw portion 4 as in the first embodiment described above, the shaft-side screw portion 4 as shown in FIG. And the roller side thread portion 6 become weaker as they go to the right side in the figure. At this time, when the planetary roller 3 is not inclined with respect to the screw shaft 1, the contact surface pressure distribution between the shaft side screw portion 4 and the roller side screw portion 6 is a contact surface pressure distribution as shown in FIG. That is, the contact surface pressure distribution cancels the increase in surface pressure when the planetary roller 3 is tilted with respect to the screw shaft 1. Therefore, when the planetary roller 3 is inclined with respect to the screw shaft 1, the contact surface pressure distribution between the shaft side screw portion 4 and the roller side screw portion 6 becomes a contact surface pressure distribution as shown in FIG. Since uneven contact surface pressure due to the inclination of the planetary roller 3 is alleviated, the axial load acting on the planetary roller 3 is relatively large and even when the axial load acts on the planetary roller 3 from one direction, it is used for a long period of time. can do.

  In addition, as in the first embodiment described above, if the pitch of the roller side screw portion 6 that meshes without intersecting (in this case, the nut side screw portion 5) is the same pitch as the roller side screw portion 6, the planetary roller 3 is strengthened, the axial load acting on the planetary roller 3 is relatively large, and even when the axial load acts on the planetary roller 3 from one direction, it can be used for a longer period of time.

  In the first embodiment described above, the nut-side screw portion 5 has the same pitch as the roller-side screw portion 6, but the nut-side screw portion as in the second embodiment shown in FIG. The pitch of 5 may be the same as the pitch of the shaft-side screw portion 4 that intersects and meshes with the roller-side screw portion 6. In this case, it is preferable to take measures not to increase the inclination of the planetary roller 3 by reducing the backlash of the pinion gear 7 or increasing the meshing length of the pinion gear 7 and the internal gear 8.

Moreover, in 1st Embodiment mentioned above, although what made the whole pitch of the roller side screw part 6 smaller than the pitch of the axial side screw part 4, like 3rd Embodiment shown in FIG. The pitch of a part (for example, the central portion) of the roller side screw portion 6 may be made smaller than the pitch of the shaft side screw portion 4.
If the pitch of a part of the roller-side screw portion 6 is made smaller than the pitch of the shaft-side screw portion 4 as in the third embodiment, the screw shaft 1 when the planetary roller 3 is not inclined with respect to the screw shaft 1 and The contact surface pressure distribution with the planetary roller 3 is a contact surface pressure distribution as shown in FIG. 7, that is, a contact surface pressure distribution that cancels the increase in surface pressure when the planetary roller 3 is tilted with respect to the screw shaft 1. Similarly to the first embodiment, even when the axial load acting on the planetary roller 3 is relatively large and the axial load acts on the planetary roller 3 from one direction, it can be used for a long time.

FIG. 8 is a diagram showing a schematic configuration of a screw device according to the fourth embodiment of the present invention, and FIG. 9 is a diagram showing a main part of the screw device according to the fourth embodiment, as shown in FIG. The screw device according to the fourth embodiment includes a screw shaft 1, a nut 2, and a plurality of planetary rollers 3.
The planetary roller 3 is provided between the screw shaft 1 and the nut 2, and the outer peripheral surface of each planetary roller 3 is provided on the outer peripheral surface of the screw shaft 1 and the inner periphery of the nut 2. Roller-side threaded portions 6 that mesh with both nut-side threaded portions 5 formed on the surface are formed at the same pitch as the shaft-side threaded portion 4. The planetary roller 3 has pinion gears 7 at both ends in the axial direction, and two internal gears 8 that mesh with the pinion gears 7 are fixed on the inner peripheral surface of the nut 2. Further, the planetary roller 3 has a small-diameter shaft portion 3 a that does not engage with both the shaft-side screw portion 4 and the nut-side screw portion 5 in the central portion, and the roller of the shaft-side screw portion 4 and the nut-side screw portion 5 is a roller. Assuming that the pitch of the threaded portion (in this case, the shaft-side threaded portion 4) intersecting with the side threaded portion 6 is P, an integral multiple thereof is N, and a positive value smaller than the pitch P is ΔX, as shown in FIG. The distance between the thread grooves of the roller-side screw portions 6 adjacent to each other across the small-diameter shaft portion 3a is P × N−ΔX as shown in FIG.

The nut-side screw portion 5 is formed on the inner peripheral surface of the nut 2 at the same pitch as the roller-side screw portion 6, but as shown in FIG. 9, the pitch of the portion corresponding to the small diameter shaft portion 3a of the planetary roller 3 is P-ΔX.
As in the fourth embodiment described above, the roller-side screw portion 6 that intersects and meshes with the shaft-side screw portion 4 is formed on the outer peripheral surface of the planetary roller 3 at the same pitch as the pitch P of the shaft-side screw portion 4, When the distance between the thread grooves of the roller-side screw portions 6 adjacent to each other with the small-diameter shaft portion 3a interposed therebetween is P × N−ΔX, as shown in FIG. When the planetary roller 3 is inclined with respect to the screw shaft 1 when the contact surface pressure between the roller side screw portion 6 and the roller side screw portion 6 is lower than that on the left side in the drawing than the small diameter shaft portion 3a, Since the non-uniformity is alleviated, as in the first embodiment, the axial load acting on the planetary roller 3 is relatively large, and even when the axial load acts on the planetary roller 3 from one direction, it is used over a long period of time. be able to.

FIG. 11 is a diagram showing a schematic configuration of a screw device according to the fifth embodiment of the present invention, and FIG. 12 is a diagram showing a main part of the screw device according to the fifth embodiment, as shown in FIG. The screw device according to the fifth embodiment includes a screw shaft 1, a nut 2, and a plurality of planetary rollers 3.
The planetary roller 3 is provided between the screw shaft 1 and the nut 2, and the outer peripheral surface of each planetary roller 3 is provided on the outer peripheral surface of the screw shaft 1 and the inner periphery of the nut 2. A roller-side thread portion 6 is formed that meshes with both of the nut-side thread portions 5 formed on the surface. The planetary roller 3 has pinion gears 7 at both ends in the axial direction, and two external gears 9 that mesh with the pinion gears 7 are fixed on the outer peripheral surface of the screw shaft 1.

  Here, the nominal effective diameter of the shaft-side screw portion 4 is Ds, the nominal effective diameter of the nut-side screw portion 5 is Dn, the nominal effective diameter of the roller-side screw portion 6 is Dr, the number of threads of the shaft-side screw portion 4 is Js, The number of threads of the nut-side threaded portion 5 is Jn, the number of threads of the roller-side threaded portion 6 is Jr, the nominal lead of the shaft-side threaded portion 4 is Ls, the nominal lead of the nut-side threaded portion 5 is Ln, and the roller-side threaded portion 6 Assuming that the nominal lead is Lr, the nominal pitch of the shaft side screw portion 4 is Ps, the nominal pitch of the nut side screw portion 5 is Pn, and the nominal pitch of the roller side screw portion 6 is Pr, Dn = Ds + 2Dr, Js / Jr = Ds / Dr, Jn = Js, Ls = Js × Ps, Lr = Jr × Pr, and Ln = Jn × Pn.

Further, the roller side threaded portion 6 intersects and meshes with the nut side threaded portion 5, and when the pitch of the nut side threaded portion 5 is P and a positive value smaller than the pitch of the nut side threaded portion 5 is ΔP, FIG. As shown in FIG. 4, the roller-side screw portion 6 is formed on the outer peripheral surface of the planetary roller 3 with a pitch smaller than the pitch of the nut-side screw portion 5.
The screw-side screw portion 4 meshes with the roller-side screw portion 6 without intersecting, and the screw-side screw portion 4 has the same pitch as the roller-side screw portion 6 as shown in FIG. Is formed.

  If the pitch of the roller side screw portion 6 is made smaller than the pitch of the nut side screw portion 5 as in the fifth embodiment described above, the nut side screw portion 5 and the roller side screw portion 6 are, as shown in FIG. The mesh becomes weaker as it goes to the left in the figure. At this time, when the planetary roller 3 is not inclined with respect to the nut 2, the contact surface pressure distribution between the nut-side screw portion 5 and the roller-side screw portion 6 is a contact surface pressure distribution as shown in FIG. That is, the contact surface pressure distribution cancels the increase in surface pressure when the planetary roller 3 is tilted with respect to the nut 2. Therefore, when the planetary roller 3 is tilted with respect to the nut 2, the contact surface pressure distribution between the nut 2 and the roller side screw portion 6 becomes a contact surface pressure distribution as shown in FIG. Since unevenness of the contact surface pressure due to the inclination is alleviated, the axial load acting on the planetary roller 3 is relatively large, and even when the axial load acts on the planetary roller 3 from one direction, it can be used for a long time. .

  Further, as in the fifth embodiment described above, when the pitch of the shaft-side screw portion 4 that meshes without intersecting with the roller-side screw portion 6 is the same as the pitch of the roller-side screw portion 6, the inclination of the planetary roller 3 is increased. Therefore, even when the axial load acting on the planetary roller 3 is relatively large and the axial load acts on the planetary roller 3 from one direction, it can be used for a longer period of time.

  In the screw device shown in FIGS. 2, 9 and 17, Ds: 60 mm, Dr: 20 mm, Dn: 100 mm, Js: 5, Jr: 1, Jn: 5, Ps: 3 mm, Pr: 3 mm, Pn: 3 mm, planetary roller effective length: 120 mm, shaft side screw part shape: straight groove, roller side screw part shape: R groove (radius 39 mm), nut side screw part shape: straight groove, screw part nominal inclination angle: 40 ° , P: 3 mm, ΔP: 0.3 μm, small-diameter shaft length: 30 mm, ΔX: 15 μm, reference surface pressure 1.4 GPa, difference in cumulative lead accuracy between roller-side screw portion and shaft-side screw portion and screw FIG. 15 shows the result of examining the relationship with the part length, and FIG. 16 shows the result of examining the contact surface pressure ratio between the screw shaft and the planetary roller under the same conditions as described above.

  As shown in FIG. 15, in the conventional screw device, the difference in the cumulative lead between the planetary roller and the nut is 0 mm, whereas in the screw device according to the first embodiment shown in FIG. The cumulative lead gradually decreases with respect to the nominal lead 3 mm for each number of turns. Further, in the screw device according to the fourth embodiment shown in FIG. 9, since the machining lead is offset at the small diameter shaft portion of the planetary roller, the cumulative lead difference between the planetary roller and the nut suddenly becomes negative.

As shown in FIG. 16, in the conventional screw device, the contact surface pressure is 1.2 times or more the reference surface pressure at one end of the planetary roller, whereas the first embodiment shown in FIG. 2 and FIG. It can be seen that in the screw device according to the fourth embodiment shown in (4), the nonuniformity of the contact surface pressure is alleviated, and even the portion where the surface pressure is high is suppressed to 1.1 times or less of the reference surface pressure.
In the first to fifth embodiments described above, the roller side threaded portion formed on the outer peripheral surface of the planetary roller has a positive lead angle. However, the present invention is not limited to this example. As shown in Japanese Patent Laid-Open No. 51-98472, the present invention also relates to a screw device in which the roller-side screw portion and the nut-side screw portion are annular grooves with zero lead angle, and the roller-side screw portion intersects with the shaft-side screw portion. Can be applied.

It is a figure showing a schematic structure of a screw device concerning a 1st embodiment of the present invention. It is a figure which shows the principal part of the screw apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows typically the meshing | engagement of the shaft side thread part and roller side thread part of the screw apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the contact surface pressure distribution of the axial side thread part and roller side thread part of the screw apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows typically the axial side thread part and roller side thread part of the screw apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows typically the axial side thread part and roller side thread part of the screw apparatus which concerns on the 3rd Embodiment of this invention. It is a figure which shows the contact surface pressure distribution of the axial side thread part and roller side thread part of the screw | thread apparatus which concerns on the 3rd Embodiment of this invention. It is a figure which shows schematic structure of the screw apparatus which concerns on the 4th Embodiment of this invention. It is a figure which shows the principal part of the screw apparatus which concerns on the 4th Embodiment of this invention. It is a figure which shows the contact surface pressure distribution of the axial side thread part and roller side thread part of the screw | thread apparatus which concerns on the 5th Embodiment of this invention. It is a figure which shows schematic structure of the screw apparatus which concerns on the 5th Embodiment of this invention. It is a figure which shows the principal part of the screw apparatus which concerns on the 5th Embodiment of this invention. It is a figure which shows typically meshing | engagement of the nut side thread part and roller side thread part of the screw | thread apparatus which concerns on the 5th Embodiment of this invention. It is a figure which shows the contact surface pressure distribution of the nut side thread part and roller side thread part of the screw | thread apparatus which concerns on the 5th Embodiment of this invention. It is a figure which shows the relationship between the difference of the accumulation lead precision of the roller side thread part of a screw device, and a shaft side thread part, and a thread part length. It is a figure which shows the result of having calculated the contact surface pressure ratio of the roller side thread part of a screw apparatus, and a shaft side thread part. It is a figure which shows typically the meshing | engagement of the shaft side thread part of a conventional screw device, a nut side thread part, and a roller side thread part. It is a figure for demonstrating the inclination of a planetary roller in case the roller side thread part cross | intersects and meshes with the shaft side thread part. It is a figure which shows the meshing point of the shaft side thread part and roller side thread part when a planetary roller inclines with respect to a screw shaft. It is a figure which shows the contact surface pressure distribution of a screw shaft and a planetary roller when a planetary roller inclines with respect to a screw shaft. It is a figure for demonstrating the inclination of a planetary roller in case the roller side thread part cross | intersects and meshes with the nut side thread part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw shaft 2 Nut 3 Planetary roller 4 Shaft side thread part 5 Nut side thread part 6 Roller side thread part 7 Pinion gear 8 Internal gear 9 External gear

Claims (8)

In a screw device comprising a plurality of planetary rollers between a screw shaft and a nut,
The pitch of all or a part of the roller side threaded portion formed on the outer peripheral surface of the planetary roller is set to the shaft side threaded portion formed on the outer peripheral surface of the screw shaft and the nut side formed on the inner peripheral surface of the nut. A screw device characterized in that it is smaller than a pitch of screw portions that intersect and mesh with the roller side screw portion.   2. The screw device according to claim 1, wherein a pitch of a screw portion that meshes with the shaft side screw portion and the nut side screw portion without intersecting with the roller side screw portion is set to the same pitch as the pitch of the roller side screw portion. A screw device characterized by that.   2. The screw device according to claim 1, wherein among the shaft-side screw portion and the nut-side screw portion, a thread portion that meshes with the roller-side screw portion so as to mesh with each other without intersecting with the roller-side screw portion. A screw device characterized in that the pitch is the same as the pitch. A plurality of planetary rollers are provided between the screw shaft and the nut, and a small-diameter shaft portion in which the planetary roller does not engage with an outer peripheral surface of the screw shaft and a screw portion formed on the inner peripheral surface of the nut is a central portion. In the screw device having
Of the shaft-side screw portion formed on the outer peripheral surface of the screw shaft and the nut-side screw portion formed on the inner peripheral surface of the nut, the roller-side screw portion formed on the outer peripheral surface of the planetary roller intersects and meshes. When the pitch of the threaded portion is P, an integer multiple of the pitch is N, and a positive value smaller than the pitch of the threaded portion is ΔX, the pitch of the roller side threaded portion is P, and the small diameter shaft portion is sandwiched. A screw device characterized in that a distance between screw grooves of adjacent roller side screw portions is P × N−ΔX.   5. The screw device according to claim 4, wherein a pitch of a central portion of the shaft-side screw portion and the nut-side screw portion that meshes with each other without intersecting with the roller-side screw portion is smaller than a pitch of the roller-side screw portion. A screw device characterized by that.   The screw device according to any one of claims 1 to 5, wherein a nominal effective diameter of the shaft-side screw portion is Ds, a nominal effective diameter of the nut-side screw portion is Dn, and a nominal effective diameter of the roller-side screw portion is Dr, Js is the number of threads on the shaft side screw part, Jn is the number of threads on the nut side thread part, Jr is the number of threads on the roller side thread part, Ls is the nominal lead of the shaft side thread part, and the nut side thread is Ln is the nominal lead of the roller, Lr is the nominal lead of the roller side threaded portion, Ps is the nominal pitch of the shaft side threaded portion, Pn is the nominal pitch of the nut side threaded portion, and Pr is the nominal pitch of the roller side threaded portion. Where Dn = Ds + 2Dr, Jn / Jr = Dn / Dr, Jn = Js, Ls = Js × Ps, Lr = Jr × Pr, Ln = Jn × Pn, and the shaft side thread portion is When crossing and meshing with the roller side thread , The screw device, characterized in that the shaft-side thread portion of the lead is consistent with the amount of movement of the nut.   The screw device according to any one of claims 1 to 5, wherein a nominal effective diameter of the shaft-side screw portion is Ds, a nominal effective diameter of the nut-side screw portion is Dn, and a nominal effective diameter of the roller-side screw portion is Dr, Js is the number of threads on the shaft side screw part, Jn is the number of threads on the nut side thread part, Jr is the number of threads on the roller side thread part, Ls is the nominal lead of the shaft side thread part, and the nut side thread is Ln is the nominal lead of the roller, Lr is the nominal lead of the roller side threaded portion, Ps is the nominal pitch of the shaft side threaded portion, Pn is the nominal pitch of the nut side threaded portion, and Pr is the nominal pitch of the roller side threaded portion. Where Dn = Ds + 2Dr, Js / Jr = Ds / Dr, Jn = Js, Ls = Js × Ps, Lr = Jr × Pr, Ln = Jn × Pn, and the nut side threaded portion is Intersecting with the roller side thread Both screw device, characterized in that the shaft-side thread portion of the lead is consistent with the amount of movement of the nut.   2. The screw device according to claim 1, wherein the roller-side screw portion and the nut-side screw portion are annular grooves having a lead angle of zero, and the roller-side screw portion intersects and meshes with the shaft-side screw portion. And screw device.

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