JP2006009870A - Planetary roller screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planetary roller screw device capable of preventing the advanced amount of a nut from changing even if a slip occurs at a contact part between a screw shaft and a planetary roller. <P>SOLUTION: In this device, where the effective diameter dn of the contact part between the annular groove of the nut and the annular projected line of the planetary roller is dn, the effective diameter of the contact part of the planetary roller is dr1, the effective diameter of the contact part of a screw shaft is ds, the effective diameter of a contact part between the roller screw shaft of the planetary roller and the shaft screw groove of the screw shaft is dr2, the number of the shaft screw grooves of the screw shaft is Js, and the number of the roller screw grooves of the planetary roller is Jr, and α=dn/dr2 and γ=dr2/dr1 are defined, the effective diameter ds of the contact part is ds=dr1 (α-γ-1) and the number Js of the shaft screw grooves of the screw shaft is Js=Jr α/γ. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a planetary roller screw device used for a feed mechanism of a mechanical device such as an injection molding machine or a press molding machine, an automobile actuator, or the like.

In the conventional planetary roller screw device, an annular groove is formed on the outer peripheral surface between a screw shaft having a single shaft screw groove formed on the outer peripheral surface and a nut having a plurality of circumferential annular grooves formed on the inner peripheral surface. A planetary roller is formed by forming a plurality of planetary rollers formed with parallel small annular ridges which are formed on the outer circumferential surface of the large annular ridges and meshing with the shaft screw grooves on the outer circumferential surface of the large annular ridges. The pitch of the small annular ridges is offset according to the number of screws, and the amount of advance of the nut per rotation of the screw shaft is less than the lead of the shaft screw groove (same as the pitch in the case of one screw), and the rotational movement is performed. It is converted into a linear motion (see, for example, Patent Document 1).
Japanese Examined Patent Publication No. 4-81654 (mainly page 3, right column, line 7-page 4, left column, line 14, FIG. 1)

However, in the above-described conventional technology, the amount of advance of the nut per one rotation of the screw shaft is different from that of the lead of the screw shaft. Therefore, when slip occurs at the contact portion between the screw shaft and the planetary roller, the slip ratio As a result, there is a problem that the amount of advance of the nut changes.
This change in the amount of advance of the nut requires a device for feedback control that makes accurate positioning difficult in positioning in a mechanical device, and in an automobile actuator, changes the conversion rate of driving torque to axial force, This can easily result in a loss of control system stability.

  The present invention has been made to solve the above-described problems, and provides a planetary roller screw device in which the amount of advance of the nut does not change even when slippage occurs in the contact portion between the screw shaft and the planetary roller. Objective.

In order to solve the above-described problems, the present invention provides a planetary roller screw device in which a screw shaft having a shaft screw groove formed on an outer peripheral surface, a nut having an annular groove formed on an inner peripheral surface, and the annular groove formed on an outer peripheral surface. A plurality of planetary rollers that form an annular ridge to be fitted, and have a roller screw groove in the same twist direction as the shaft screw groove that meshes with the shaft screw groove on the outer peripheral surface of the annular ridge, The effective diameter of the contact portion of the annular groove of the nut with the annular protrusion of the planetary roller is _dn, and the effective diameter of the contact portion of the annular protrusion of the planetary roller with the annular groove of the nut is _dr1 , The effective diameter of the contact portion of the shaft screw groove of the screw shaft with the roller screw groove of the planetary roller is d _S, and the effective diameter of the contact portion of the roller screw groove of the planetary roller with the shaft screw groove of the screw shaft is d. and _r2, the number of threads of the axial thread groove of the screw shaft and J _S, said Yu The number of threads of the roller screw groove of the roller and _{J r, α = d n /} d r1, when defining a γ = d _{r2 /} d _r1, a roller screw groove of the planetary rollers in the axial thread groove of the screw shaft D _S is d _S = d _r1 (α−γ−1), and the number of shaft thread grooves of the screw shaft is J _S , J _S = J _r · α / It is characterized by being γ.

  Thus, according to the present invention, the amount of advance of the nut does not change even when the screw shaft slips between the screw shaft and the planetary roller, and the amount of advance of the nut per one rotation of the screw shaft is reduced. It can be matched with the lead of the groove, and in the positioning in the mechanical device, accurate positioning can be performed without performing feedback control. In the actuator for automobiles, the conversion rate of driving torque to axial force is constant. The effect that the stability of the control system can be improved is obtained.

  Embodiments of a planetary roller screw device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a side sectional view showing a planetary roller screw device according to a first embodiment.
In FIG. 1, reference numeral 1 denotes a planetary roller screw device.
Reference numeral 2 denotes a screw shaft of the planetary roller screw device 1, which is a rod-shaped member made of a steel material such as alloy steel, and one or multiple shaft screw grooves 3 are spirally formed with a predetermined lead on the outer peripheral surface thereof. Is formed.

Reference numeral 4 denotes a nut of the planetary roller screw device 1, which is a cylindrical member made of alloy steel. A plurality of circumferential annular grooves 5 having a substantially trapezoidal cross-sectional shape are formed on the inner peripheral surface thereof. ing.
Reference numeral 6 denotes a planetary roller, which is a rod-shaped member made of a steel material such as an alloy steel, and has cylindrical shaft portions 7 formed at both ends, and an outer peripheral surface between both shaft portions 7 A circumferential annular ridge 8 having a substantially trapezoidal cross-sectional shape that fits into the annular groove 5 of the nut 4 is formed, and an axial thread groove 3 that meshes with the axial thread groove 3 on the outer circumferential surface of the annular ridge 8; One or multiple roller screw grooves 9 having the same twist direction are formed in a spiral shape.

Reference numeral 10 denotes a cage, which is an annular member made of a resin material, a steel plate or the like, and a plurality of fitting holes 11 with which the shaft portion 7 of the planetary roller 6 is fitted are provided at a predetermined angular pitch. The shaft portion 7 of the planetary roller 6 is held by the fitting hole 11, and a plurality of planetary rollers 6 are arranged at a predetermined angular pitch between the screw shaft 2 and the nut 4.
The roller screw grooves 9 and the annular protrusions 8 of the plurality of planetary rollers 6 held by the cage 9 are fitted in the shaft screw groove 3 of the screw shaft 2 and the annular groove 5 of the nut 4, and the screw shaft 2 is By rotating, the planetary roller 6 revolves while rotating around the screw shaft 2 to move the nut 4 in the axial direction. Thereby, rotational motion is converted into linear motion.

When the rotational motion of the screw shaft 2 is converted into the linear motion of the nut 4, the screw shaft 2 can be used even when slip occurs at the contact portion between the shaft screw groove 3 of the screw shaft 2 and the roller screw groove 9 of the planetary roller 6. A configuration for preventing a change in the amount of advance of the nut 4 that accompanies this rotation will be described below with reference to FIG.
The symbols used in FIG. 2 and the definitions of symbols used in the explanation are summarized below.

d _n : Effective diameter of the contact portion of the annular groove 5 of the nut 4 with the annular protrusion 8 of the planetary roller 6 d _r1 : Effective diameter of the contact portion of the annular protrusion 8 of the planetary roller 6 with the annular groove 5 of the nut 4 d _S : Effective diameter of the contact portion of the shaft screw groove 3 of the screw shaft 2 with the roller screw groove 9 of the planetary roller 6 d _r2 : Contact of the roller screw groove 9 of the planetary roller 6 with the shaft screw groove 3 of the screw shaft 2 Effective diameter of part O : Center of the planetary roller 6 d _C : Pitch circle diameter of the center O of the planetary roller 6 θ : Revolution angle of planetary roller 6 as seen from coordinate system stationary with nut 4 φ : Rotation angle of the planetary roller 6 as seen from the coordinate system rotating with the planetary roller A : Point B on d _{r2 at} the rotation angle φ of the planetary roller 6 B : Point on d _{r1 at} the rotation angle φ of the planetary roller 6 J _S : number of threads of the shaft screw groove 3 of the screw shaft 2 J _r : number of threads of the roller screw groove 9 of the planetary roller 6 P : Pitch between adjacent grooves of the shaft screw groove 3 and the roller screw groove 9 Note that the coordinate axes are the y direction and the z direction shown in FIG.

In order for the roller screw groove 9 and the annular protrusion 8 of the planetary roller 6 to fit in the shaft screw groove 3 of the screw shaft 2 and the annular groove 5 of the nut 4, the planetary roller 6 revolves while rotating.
d _C = d _S + d _r1 = d _n −d _r2 (1)
It is necessary to become
α = d _n / d _r1 (2)
γ = d _r2 / d _r1 (3)
The effective diameter d _S of the contact portion of the shaft thread groove 3 with the roller thread groove 9 is defined as
d _S = d _r1 (α−γ−1) (4)
It is necessary to.

  When the planetary roller 6 is revolving while rotating around the screw shaft 2, the revolution angle θ, the point A and the point B at the rotation angle φ, and the y coordinate of the center O of the planetary roller 6 are respectively

滑りを考慮しない場合に単位時間あたりねじ軸２が１回転すると仮定すると、その初期値は、

Assuming that the screw shaft 2 makes one rotation per unit time without considering the slip, the initial value is

ここで、ねじ軸２と遊星ローラ６との間のねじ軸２の滑り率をε_ｓｒ、遊星ローラ６とナット４との間の遊星ローラ６の滑り率をε_ｒｎとし、τ_ｓｒ、τ_ｒｎを

Here, the slip rate of the screw shaft 2 between the screw shaft 2 and the planetary roller 6 is ε _sr , the slip rate of the planetary roller 6 between the planetary roller 6 and the nut 4 is ε _rn, and τ _sr , τ _rn The

ここで、遊星ローラ６と共に回転する座標系におけるねじ軸２の自転数をＮ_ｓ、遊星ローラ６と共に回転する座標系における遊星ローラ６の自転数をＮ_ｒとすると、それぞれ

Here, rotation number N _s of the screw shaft 2 in a coordinate system rotating with the planetary roller 6 _and the rotation number of the planetary roller 6 and N _r in the coordinate system that rotates with the planetary roller 6, respectively

また、ねじ軸２と遊星ローラ６の相対移動距離、つまりねじ軸２の１回転あたりのナット４の進み量をＬ_ｓｒは、軸ねじ溝３とローラねじ溝９の捩れ方向が同じなので、

Further, the relative movement distance between the screw shaft 2 and the planetary roller 6, that is, the advance amount of the nut 4 per rotation of the screw shaft 2 is L _sr , because the twist direction of the shaft screw groove 3 and the roller screw groove 9 is the same.

ここで、遊星ローラ６とナット４との間に滑りがないと仮定すると、

Here, assuming that there is no slip between the planetary roller 6 and the nut 4,

であれば、ねじ軸２と遊星ローラ６との間のねじ軸６の滑りに関わらず、ナット４の進み量Ｌ_ｓｒは、
Ｌ_Ｓｒ＝ＰＪ_ｓ ・・・・・・（１９）
となり、ねじ軸６の滑りがあったとしてもねじ軸２の１回転あたりのナット４の進み量は常に軸ねじ溝３の１リード分となる。

If so, regardless of the sliding of the screw shaft 6 between the screw shaft 2 and the planetary roller 6, the advance amount L _sr of the nut 4 is
L _Sr = PJ _s (19)
Thus, even if the screw shaft 6 slips, the amount of advance of the nut 4 per rotation of the screw shaft 2 is always one lead of the shaft screw groove 3.

That is, if the conditions of the equations (4) and (18) are satisfied, the advance amount of the nut 4 per one rotation of the screw shaft 2 can always be matched with the lead of the screw shaft 2 regardless of the slip of the screw shaft 2. it can.
There are an infinite number of combinations that satisfy the expression (18). For example, when α = 5, γ = 5/6, J _r = 1, and J _s = 6, nuts per one rotation of the screw shaft 2 are obtained. 4 is 6 times the lead P of the shaft screw groove 3, that is, the pitch P of the shaft screw groove 3 and the roller screw groove 9, and α = 9/4, γ = 3/4, J _r = 1, J _s = If the combination is 3, the advance amount of the nut 4 per rotation of the screw shaft 2 is three times the pitch P of the shaft screw groove 3 or the like.

As described above, in this embodiment, the annular groove of the nut and the annular protrusion of the planetary roller are fitted, and the roller screw groove in the same twist direction as the shaft screw groove is fitted to the shaft screw groove,
α = d _n / d _r1 , γ = d _r2 / d _r1
Defined as
d _S = d _r1 (α−γ−1)
J _s = J _r · α / γ
By configuring the nut, screw shaft and planetary roller so as to satisfy the requirements, even if the screw shaft slips between the screw shaft and the planetary roller, the amount of advance of the nut does not change, and the screw The amount of advance of the nut per rotation of the shaft can be matched with the lead of the shaft thread groove.

  As a result, accurate positioning can be performed without performing feedback control in positioning in mechanical devices, and the stability of the control system is improved by maintaining a constant conversion rate of driving torque to axial force in automotive actuators. Can be made.

FIG. 3 is a side sectional view showing the planetary roller screw device according to the second embodiment.
In addition, the same code | symbol is attached | subjected to the part similar to the said Example 1, and the description is abbreviate | omitted.
In FIG. 3, reference numeral 21 denotes a planetary pinion gear, which is a small-diameter spur gear coaxial with the planetary roller 6 and provided adjacent to the inside of the shaft portion 7 on both sides thereof.
A ring gear 22 is an internal spur gear that meshes with the planetary pinion gear 21 of the planetary roller 6 held by the cage 10, and is between the cage 10 and the end surface of the annular ridge 8 of the planetary roller 6. It is arrange | positioned and it fits inside the nut 4 and the movement of the axial direction is restrict | limited.

Gear ratio between the ring gear 22 and the planetary pinion gears 21 is set such that the ratio of the effective diameter d _r1 of the annular projection 8 of the effective diameter d _n and the planetary roller 6 of the annular groove 5 of the nut 4, i.e. the same as the α Is done.
Thereby, slipping between the nut and the planetary roller can be reliably prevented, and the effect of the first embodiment can be made more reliable.

  In each of the above embodiments, the screw shaft of the planetary roller screw device is rotated to move the nut in the axial direction. However, the present invention is applied to a planetary roller screw device of the type that rotates the nut to move the screw shaft. Even if the invention is applied, the same effect can be obtained.

Side sectional view showing the planetary roller screw device of Embodiment 1 Explanatory drawing which shows the dimensional relationship of the planetary roller screw apparatus of Example 1. FIG. Side sectional view showing a planetary roller screw device of Embodiment 2

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Planetary roller screw apparatus 2 Screw shaft 3 Shaft thread groove 4 Nut 5 Annular groove 6 Planetary roller 7 Shaft part 8 Annular protrusion 9 Roller thread groove 10 Cage 11 Fitting hole 21 Planetary pinion gear 22 Ring gear

Claims (5)

A screw shaft having a shaft screw groove formed on the outer peripheral surface, a nut having an annular groove formed on the inner peripheral surface, an annular ridge that fits the annular groove formed on the outer peripheral surface, and an outer peripheral surface of the annular ridge A plurality of planetary rollers formed with roller screw grooves in the same twist direction as the shaft screw grooves meshing with the shaft screw grooves,
The planetary roller is revolved while rotating between the screw shaft and the nut, and the advance amount of the nut per one rotation of the screw shaft is matched with the lead of the shaft screw groove. Roller screw device. A screw shaft having a shaft screw groove formed on the outer peripheral surface, a nut having an annular groove formed on the inner peripheral surface, an annular ridge that fits the annular groove formed on the outer peripheral surface, and an outer peripheral surface of the annular ridge A plurality of planetary rollers formed with roller screw grooves in the same twist direction as the shaft screw grooves meshing with the shaft screw grooves,
The effective diameter of the contact portion of the annular groove of the nut with the annular protrusion of the planetary roller is _dn, and the effective diameter of the contact portion of the annular protrusion of the planetary roller with the annular groove of the nut is _dr1 , The effective diameter of the contact portion between the shaft screw groove of the screw shaft and the roller screw groove of the planetary roller is d _S, and the effective diameter of the contact portion of the roller screw groove of the planetary roller with the shaft screw groove of the screw shaft is defined as d _S. d _r2 , J _S is the number of shaft thread grooves of the screw shaft, J _r is the number of roller thread grooves of the planetary roller,
α = d _n / d _r1 , γ = d _r2 / d _r1
Defined as
D _S is an effective diameter of a contact portion between the shaft screw groove of the screw shaft and the roller screw groove of the planetary roller.
d _S = d _r1 (α−γ−1)
And J _S is the number of thread grooves in the screw shaft.
J _s = J _r · α / γ
A planetary roller screw device characterized by In claim 1 or claim 2,
A planetary roller screw device, wherein the screw shaft has a plurality of shaft screw grooves. In claim 1, claim 2 or claim 3,
A planetary roller screw device, wherein the planetary roller has a plurality of roller screw grooves. In claim 1 to claim 3 or claim 4,
A planetary pinion gear is provided on the planetary roller, and a ring gear that meshes with the planetary pinion gear is provided.
The gear ratio of the planetary pinion and the ring gear, and the effective diameter d _n of the contact portion between the annular ridge of the planetary rollers of the annular groove of the nut, an annular groove of said nut annular ridge of the planetary rollers A planetary roller screw device characterized by having a ratio to the effective diameter _dr1 of the contact portion.

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