Screw mechanism

Abstract

To obtain a small-lead screw mechanism having a simple structure, and easy in the setting of an operation condition.SOLUTION: A screw mechanism K comprises: an input shaft A1 rotating around a rotation axial core X; an intermediate shaft A2 arranged coaxial with the input shaft A1, and screwed to the input shaft A1 via a first screw part s1; an output shaft A3 arranged coaxial with the input shaft A1, and screwed with the intermediate shaft A2 via a second screw part s2 being a reverse screw which is reverse to the first screw part s1; and an intermediate rotating body pivoted to one of the input shaft A1, the intermediate shaft A2 and the output shaft A3, screwed with the other two shafts which are not pivoted, relatively rotating the input shaft A1 and the output shaft A3, and relatively linearly moving the input shaft A1 and the output shaft A3 in parallel with the rotation axial core X with respect to the intermediate shaft A2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a screw mechanism having other gear elements or screw elements between an input shaft and an output shaft, and having high efficiency and a small lead.

Background Art

[0002] Conventionally, as such a screw mechanism, there is, for example, one shown in Patent Document 1 (see

[0007] ,

[0027] and the drawings).

[0003] This screw mechanism has a sun shaft, a planet shaft, and a ring shaft that rotate coaxially, and each has a first planetary gear mechanism having helical sun gears, helical planet gears, and helical ring gears that cooperate with each other, and a second planetary screw mechanism having screw-shaped sun gears, screw-shaped planet gears, and screw-shaped ring gears.

[0004] According to this configuration, when the sun shaft and the ring shaft are relatively rotated, the sun shaft provided with helical sun gears having different tooth number ratios or the ring shaft provided with helical ring gears moves linearly along the rotation axis. Conversely, when the sun shaft and the ring shaft are relatively linearly moved along the rotation axis, the sun shaft provided with helical sun gears having different tooth number ratios or the ring shaft provided with helical ring gears relatively rotates. Therefore, it is possible to perform motion conversion between rotational motion and linear motion between the sun shaft and the ring shaft.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the conventional screw mechanism described above, in order to cause the sun axis and the ring axis to rotate relative to each other or move linearly under the desired conditions, it is necessary to match the number of teeth of each helical gear constituting the first planetary gear mechanism with the pitch of each screw gear constituting the second planetary screw mechanism.

[0007] However, in this screw mechanism, the screw-fit structure between the screw-shaped planetary gear and the screw-shaped ring gear is configured so that the planetary axis and the ring axis do not move relative to each other along the direction of extension of the rotation axis. Therefore, the rotation ratio between the planetary axis and the ring axis is limited, and the degree of freedom in setting appropriate relative movement conditions between the solar axis and the ring axis is reduced.

[0008] Furthermore, the screw mechanism becomes more complex, requiring a mechanism to hold the planetary axis so that it does not move linearly relative to the ring axis, which increases processing time and manufacturing costs.

[0009] Thus, the conventional screw mechanisms described above have various problems that need to be solved, and there was a need for a screw mechanism with a simple structure and easy setting of operating conditions, and with a small lead. [Means for solving the problem]

[0010] (Feature composition) The characteristic configuration of the screw mechanism according to the present invention is, An input shaft that rotates around the axis of rotation, An intermediate shaft is arranged coaxially with the input shaft and is screwed to the input shaft via a first threaded portion, An output shaft is arranged coaxially with the input shaft and is screwed to the intermediate shaft via a first threaded portion and a second threaded portion which is a reverse thread. It is supported by any one of the input shaft, the intermediate shaft, and the output shaft, A planetary gear system is provided, which meshes with two other unsupported shafts to rotate the input shaft and the output shaft relative to each other, and also causes the input shaft and the output shaft to move in a relative linear motion parallel to the rotation axis with respect to the intermediate shaft. The output shaft is positioned on the outermost side, and the planetary gear is pivotally supported on the output shaft and meshes with the outer surface of the input shaft and the outer surface of the intermediate shaft. It's at a single point.

[0011] (effect) The screw mechanism of this structure is arranged such that the input shaft and the output shaft rotate relative to each other, and the intermediate shaft is screwed to the input shaft and the output shaft. The planetary gear is supported by one of the input shaft, the intermediate shaft, and the output shaft, and these three shafts rotate relative to each other. The first screw part and the second screw part are reverse screws. When the input shaft and the output shaft rotate with respect to the intermediate shaft, the input shaft and the output shaft perform relative linear motion parallel to the rotation axis with respect to the intermediate shaft respectively.

[0012] In this structure, by appropriately setting the pitches of the first screw part and the second screw part, the screwing distances of the input shaft and the output shaft with respect to the intermediate shaft can be set. For example, even when the input shaft is rotationally driven relatively quickly, the screwing distance of the output shaft with respect to the input shaft can be set small. In this case, the first screw part and the second screw part may have a normal lead angle.

[0013] Thus, with this structure, by combining screws with a normal lead angle with less overall frictional loss, a simple structure can be obtained, the operating conditions can be easily set, and a small-lead screw mechanism can be obtained. At that time, since the input shaft, the intermediate shaft, and the output shaft perform relative linear motion parallel to the rotation axis, it is easy to set the conditions of each gear and each screw. Also, it is not necessary to fix the intermediate shaft so as not to move in the direction parallel to the rotation axis, the overall structure is simplified, the number of parts and the assembly man-hours are reduced, and cost reduction becomes possible.

[0014]

[0015]

[0016]

[0017] <匡

[0018]

[0019]

[0020]

[0021]

[0022] With this configuration, the planetary gear can be rotatably supported, for example, on a shaft portion provided on the end face of the output shaft, and the planetary gear can be arranged outside the input shaft and the intermediate shaft. In this case, the planetary gear can have a meshing portion with respect to the input shaft and a meshing portion with respect to the intermediate shaft. By setting the number of teeth of these meshing portions, etc., the setting range of the rotation conditions of each shaft becomes larger. Therefore, it becomes easier to obtain an optimal screw mechanism according to the part to be used.

Brief Description of the Drawings

[0023] [Figure 1] Perspective view showing the constituent members of the screw mechanism according to the first embodiment [Figure 2] Cross-sectional view showing the screw mechanism according to the first embodiment [Figure 3] Cross-sectional view showing the screw mechanism according to the second embodiment

Mode for Carrying Out the Invention

[0024] 〔First Embodiment〕 (Overview) The present invention obtains a screw mechanism K having an extremely small lead angle by combining screw portions having a normal lead angle. FIGS. 1 and 2 show a first embodiment of the screw mechanism K.

[0025] The screw mechanism K receives the driving rotation from a motor or the like (not shown) by the input shaft A1, forms a small lead angle by a combination of various gears inside the screw mechanism K, and outputs the significantly decelerated driving rotation from the output shaft A3 to the driving target.

[0026] More specifically, the screw mechanism K has a three-layer structure with the rotation axis X as the coaxial center, and includes an input shaft A1, an intermediate shaft A2, and an output shaft A3 in order from the center side.

[0027] (Input Shaft) The input shaft A1 is pivotally supported at one end by the housing 1 via a bearing (not shown). A first gear g1, for example, made of a spur gear, is formed in one region along the longitudinal direction, and a first male screw s11, made of a male thread, is formed in the other region adjacent to it. The first gear g1 may be made of a helical gear or the like in addition to a spur gear. The lead angle of the first male screw s11 can be a general one.

[0028] (Intermediate axis) The intermediate shaft A2 is a cylindrical member and has multiple window sections 3 along the direction of rotation in a part of its wall 2. A planetary gear gp, which acts as an intermediate rotating body, is inserted into and pivotally supported in each window section 3. This planetary gear gp meshes with the first gear g1 of the input shaft A1 and the second gear g2 of the output shaft A3, which will be described later. Each planetary gear gp is pivotally supported by a pin member 4 driven in from one side of the intermediate shaft A2.

[0029] In the region of the intermediate shaft A2 opposite to the area where the window portion 3 is provided, an intermediate female thread s12 is formed on the inner surface, and an intermediate male thread s21 is formed on the outer surface. The intermediate female thread s12 engages with the first male thread s11 to form the first threaded portion s1. The intermediate male thread s21 engages with the second female thread s22 (described later) to form the second threaded portion s2. This intermediate shaft A2 is movable in a direction parallel to the rotation axis X relative to the input shaft A1 and output shaft A3. Therefore, the configuration of the screw mechanism K is simplified, and the number of parts and assembly steps are reduced.

[0030] In this configuration, by using a planetary gear gp supported on the intermediate shaft A2 as the intermediate rotating body, the input shaft A1 and the output shaft A3 can be reliably rotated relative to each other without slippage. Therefore, the screw advance distance of the output shaft A3 based on the rotational drive of the input shaft A1 can be precisely set.

[0031] Furthermore, by using planetary gears gp, the input shaft A1 and the output shaft A3 can be meshed with spur gears, resulting in extremely low rotational resistance between them. Thus, a smoothly operating screw mechanism K can be obtained.

[0032] Furthermore, the strength of the cylindrical structure of the intermediate shaft A2 can be utilized, and a simple assembly method can be adopted, which involves simply inserting the input shaft A1 into the intermediate shaft A2. Therefore, a rational and inexpensive screw mechanism K can be obtained.

[0033] (Output axis) The output shaft A3 is also a cylindrical member and is extrapolated onto the intermediate shaft A2. One region of its inner surface is equipped with a second gear g2 as internal teeth that mesh with the planetary gear gp. Also, in the region of the inner surface adjacent to the second gear g2, a second female thread s22 is formed that screws into the intermediate male thread s21. The second threaded portion s2 is formed by the intermediate male thread s21 and the second female thread s22. The lead angle of the second threaded portion s2 is also typical. The first threaded portion s1 and the second threaded portion s2 are formed in a reverse thread relationship, and the screw mechanism K operates as follows.

[0034] When the input shaft A1 rotates in one direction, the intermediate shaft A2 rotates faster than the input shaft A1, while rotating the planetary gear gp. Also, since the output shaft A3, which has an internal gear second gear g2, rotates via the planetary gear gp, the output shaft A3 always rotates slower than the intermediate shaft A2. In other words, the speed of rotation along the same direction is in the order of input shaft A1, intermediate shaft A2, and output shaft A3.

[0035] At this time, due to the effect of the first threaded portion s1, the intermediate shaft A2 rotates relative to the input shaft A1 and moves to one side along the rotation axis X of the input shaft A1. Also, the output shaft A3 rotates relative to the intermediate shaft A2 due to the second threaded portion s2, which is a reverse thread, and therefore moves in the opposite direction to the movement of the intermediate shaft A2. The input shaft A1 and the output shaft A3 move linearly in the same direction relative to the intermediate shaft A2, but the input shaft A1 and the output shaft A3 rarely maintain the same absolute position or the same relative position along the direction of the rotation axis X, and move relative to each other in one direction or the other. The absolute rotation direction and rotation speed of the output shaft A3 can be appropriately set by the configuration of each gear and each threaded portion.

[0036] In this way, by combining screw sections with normal lead angles, it is possible to simplify the overall structure while obtaining a screw mechanism K with a particularly small lead. Generally, screw sections with small lead angles have high friction losses, but with this configuration, a highly efficient screw mechanism K can be obtained by combining it with screws with normal lead angles that have low overall friction losses.

[0037] [First Example] For example, if the number of teeth on the first gear g1 is 30, the number of teeth on the second gear g2 is 60, the lead of the first threaded section s1 is 1.25, and the lead of the second threaded section s2 is 1.75, then when the rotational speed of the input shaft A1 is 1, the rotational speed of the output shaft A3 will be 0.33. Also, the total lead of the output shaft A3 will be 0.25.

[0038] [Second Embodiment] Figure 3 shows a different configuration of the screw mechanism K. Here, the planetary gear gp, which is an intermediate rotating body, is pivotally supported on the outermost output shaft A3. The output shaft A3 is cylindrical, and the planetary gear gp is pivotally supported in each of the multiple window sections 3 formed along the direction of rotation. The planetary gear gp is composed of two stages: a first-stage gear gp1 and a second-stage gear gp2. The first-stage gear gp1 meshes with the first gear g1 of the input shaft A1, and the second-stage gear gp2 meshes with the second gear g2 of the intermediate shaft A2.

[0039] A first threaded portion s1 is formed between the outer surface of the input shaft A1 and the inner surface of the intermediate shaft A2, and a second threaded portion s2 is formed between the outer surface of the intermediate shaft A2 and the inner surface of the output shaft A3.

[0040] [Second Example] In this configuration, for example, if the number of teeth of the first gear g1 is 30, the number of teeth of the first stage gear gp1 is 30, the number of teeth of the second stage gear gp2 is 15, the number of teeth of the second gear g2 is 45, the lead of the first threaded portion s1 is 1.25, and the lead of the second threaded portion s2 is 1.75, then when the rotational speed of the input shaft A1 is 1, the rotational speed of the output shaft A3 will be 0.33, and the total lead of the output shaft A3 will be 0.25.

[0041] Even with this configuration, by appropriately setting the lead of each gear and screw, a screw mechanism K with a large reduction ratio and small lead can be obtained while using gears and screw parts of a normal configuration.

[0042] [Other Embodiments] In the embodiments described above, the intermediate rotating body is constructed using planetary gears gp, but instead, friction-contacting roller members can be used. However, in this case, it may be necessary to generate excessive pressing force between the input shaft A1 and the output shaft A3, for example, in order to reduce slippage of the roller members, which could increase the rotational resistance of each shaft. Furthermore, deformation and wear of the roller members are more likely to occur. Nevertheless, since the configuration of the roller members is simple, a simple and low-cost screw mechanism K can be obtained overall. [Industrial applicability]

[0043] The screw mechanism of the present invention has a coaxial design for the input shaft and output shaft, a large reduction ratio from the input shaft to the output shaft, and an extremely small lead, making it widely applicable to various types of machinery. [Explanation of Symbols]

[0044] 2 wall 3 Window section A1 Input Axis A2 intermediate shaft A3 output axis GP Planetary Gear K screw mechanism s1 First threaded section s2 Second threaded section X Rotation axis

Claims

[Claim 1] An input shaft that rotates around the axis of rotation, An intermediate shaft is arranged coaxially with the input shaft and is screwed to the input shaft via a first threaded portion, An output shaft is arranged coaxially with the input shaft and is screwed to the intermediate shaft via a first threaded portion and a second threaded portion which is a reverse thread. The system comprises a planetary gear that is pivotally supported on one of the input shaft, the intermediate shaft, and the output shaft, and meshes with the other two unsupported shafts, thereby causing the input shaft and the output shaft to rotate relative to each other, and causing the input shaft and the output shaft to move in a relative linear motion parallel to the rotation axis with respect to the intermediate shaft, A screw mechanism in which the output shaft is positioned on the outermost side, and the planetary gear is pivotally supported on the output shaft and meshes with the outer surface of the input shaft and the outer surface of the intermediate shaft.

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