Planetary roller screw with gear transmission

Abstract

The present invention relates to a planetary roller screw of gear transmission mode, wherein the roller has threads, ring teeth, gears and optical axes in sequence from the middle to the outside, and the inner hole of the nut has three main structures in the axial direction: an inner gear ring mounting structure located at both ends of the nut, a ring tooth structure symmetrically distributed at both ends of the nut, and an avoidance step hole in the middle section of the nut; the rollers are evenly distributed around the screw, the middle thread meshes with the thread of the screw but not with the nut, the ring teeth at both ends of the roller mesh with the ring teeth at both ends of the nut, the outer gear meshes with the gear of the inner gear ring installed in the inner gear ring mounting structure of the nut, and the optical axes at both ends match the evenly distributed circular holes on the planet carrier. The planetary roller screw has a constant lead, and the thread processing of the nut is cancelled, and only the ring teeth are processed at both ends of the nut to bear the axial load, and the gears at both ends of the roller ensure the transmission ratio of the roller and the nut, and avoid the lead uncertainty caused by the mutual sliding of the two.

Description

Technical Field

[0001] The present invention relates to a planetary screw drive mechanism for converting rotational motion into linear motion, and particularly to a planetary roller screw for heavy-duty high-speed transmission. Background Art

[0002] Compared with ball screws, roller screws have the characteristics of stronger load-bearing capacity, higher speed, higher precision, longer service life, and lower maintenance cost, thus becoming one of the most critical basic components in precision mechanical equipment such as aviation machinery, numerical control machine tools, precision instruments, and meters, and have been quite widely used.

[0003] In addition to the screw, nut, and rollers, the planetary roller screw also includes parts such as an internal gear ring, a planetary carrier, and a retaining ring. According to the relative motion forms between the rollers and the nut and the screw during the transmission process, the planetary roller screw can generally be divided into three types: standard type, nut type, and circulating type. Among them, in the standard type, the rollers and the nut are axially relatively stationary, in the nut type, the rollers and the screw are axially relatively stationary, and in the circulating type, the rollers move periodically back and forth axially relative to the nut.

[0004] During the specific motion process, the roller threads mesh with the screw threads and the nut threads respectively to transmit power. When the screw rotates, the nut moves axially along the screw, the rollers rotate and make planetary motion around the screw while maintaining the same axial moving speed as the nut. Through the above motion, rotational motion is converted into linear motion.

[0005] In the prior art, for standard and nut-type planetary roller screws, the middle section of the roller is a threaded structure and the two ends are gear structures. The roller threads mesh with the threaded structures of the screw and the nut respectively. The gear structure at the roller shaft end meshes with the internal gear ring fixed on the nut. In the circulating-type planetary roller screw, the roller has a pure ring gear structure and the nut has a threaded structure, and there are defects such as high noise during the transmission process. In other forms of planetary roller screws, the roller has a ring gear structure and the nut also has a pure ring gear structure, but in the transmission process, there is a defect of uncertain lead in principle. Summary of the Invention

[0006] In order to optimize the structure and transmission mode of the planetary roller screw, and reduce the difficulty in processing, manufacturing and assembling the planetary roller screw, the present invention provides a planetary roller screw with a gear transmission mode. This planetary roller screw has a constant lead, and the thread machining of the nut is cancelled. Only ring teeth are machined at both ends of the nut to bear the axial load. The gears at both ends of the roller ensure the transmission ratio between the roller and the nut, avoiding the uncertainty of the lead caused by the mutual sliding of the two. The thread on the roller only meshes with the screw, greatly reducing the assembly difficulty, increasing the assembly convenience, and avoiding assembly problems caused by the thread phase and gear phase. The thread meshing only exists between the screw and the roller, and the ring meshing only exists between the nut and the roller. Therefore, the degree of freedom of parameter design is greatly increased during the design process of the thread parameters and related structure parameters.

[0007] To achieve the above object, the technical solution of the present invention is: a planetary roller screw with a gear transmission mode, including a screw, a nut, a roller, an internal gear ring, a fixed pin shaft, a planetary carrier, and a retaining ring. The middle of the roller is successively outward with a thread, a ring tooth, a gear, and a smooth shaft. The inner hole of the nut mainly has three structures axially: an internal gear ring installation structure at both ends of the nut, a ring tooth structure symmetrically distributed at both ends of the nut, and an avoidance stepped hole in the middle section of the nut. The rollers are evenly distributed around the screw. The middle thread meshes with the thread of the screw and does not mesh with the nut. The ring teeth at both ends of the roller mesh with the ring teeth at both ends of the nut, and the outer gears mesh with the gears of the internal gear ring installed in the internal gear ring installation structure of the nut. The smooth shafts at both ends cooperate with the circular holes evenly distributed on the planetary carrier.

[0008] Further, the internal gear ring is installed within the internal gear ring installation structure of the nut and is axially fixed with a fixed pin shaft 5.

[0009] Further, the left and right planetary carriers are installed at the installation positions of the internal gear ring, and the retaining ring is installed within the groove of the internal gear ring 4 for axially fixing the planetary carrier.

[0010] Further, the thread of the roller is a single-start thread, and the pitch of the thread is the same as the pitch of the thread of the screw.

[0011] Further, the outer diameter of the ring tooth of the roller is smaller than the bottom diameter of the thread to avoid interference with the screw thread, and is used to bear the axial force and part of the possible radial force.

[0012] Further, the ratio of the diameter of the ring tooth of the roller to the diameter of the ring tooth of the nut is the same as the ratio of the number of teeth of the roller to the number of teeth of the internal gear ring on the nut.

[0013] Further, the thread of the screw is a multi-start thread.

[0014] Further, when the lead screw rotates, the nut moves along the axis of the lead screw. The roller rotates on its own axis and makes a planetary motion around the lead screw, and maintains the same axial movement speed as the nut, converting the rotational motion into a linear motion.

[0015] Further, the planetary roller screw with the gear drive mode is also provided with a preloading structure, and the preloading structure is a locking preloading structure or an elastic disc spring preloading structure.

[0016] Further, the locking preloading structure is composed of an adjusting gasket, a locking screw and nut. The adjusting gasket is placed between two half nuts, and the two half nuts are connected by the locking screw and nut. A preloading force is applied to this planetary roller screw through the locking screw and nut, making the contact of the ring teeth more tight, reducing the transmission clearance and ensuring the smoothness of the transmission.

[0017] The beneficial effects of the present invention are as follows:

[0018] The present invention provides a planetary roller screw with a new transmission mode. A gear, ring teeth and thread structure are designed on the roller, and the nut is designed as a structure with ring teeth at both ends and a hollow in the middle. The roller thread only contacts the lead screw thread and does not contact the nut. The planetary motion of the roller is formed by the ring teeth and gears at both ends of the roller. This kind of planetary motion is significantly different from the conventional planetary roller screw. Under this transmission mode, through the design of specific transmission ratio and thread parameters, the constant lead of this planetary roller screw is realized. The planetary roller screw obtained by this invention has great advantages in processing, manufacturing, assembly, etc., and reduces the difficulty in the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a three-dimensional schematic diagram of the composition of the planetary roller screw with the gear drive mode;

[0020] Figure 2 is a three-dimensional schematic diagram of the roller structure;

[0021] Figure 3 is a planar schematic diagram of the roller structure;

[0022] Figure 4 is a three-dimensional schematic diagram of the nut structure;

[0023] Figure 5 is a three-dimensional schematic diagram of the lead screw structure;

[0024] Figure 6 is a three-dimensional schematic diagram of the composition of the preloaded planetary roller screw. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be further described below in conjunction with the drawings and embodiments.

[0026] As Figure 1As shown in the figure, a planetary roller screw with a gear drive includes parts such as a screw 1, a nut 2, rollers 3, an internal gear ring 4, fixed pin shafts 5, a planetary carrier 6, a retaining ring 7, etc.

[0027] As Figure 2 , as shown in Figure 3, the middle of the roller 3 is successively outward with a thread 3-1, a ring gear 3-2, a gear 3-3, and a smooth shaft 3-4. The middle of the roller 3 is a threaded structure, and this thread is generally a single-start thread, and the pitch of the thread is the same as the pitch of the thread of the screw 1; the outside of the thread is a ring gear structure, and the outer diameter of the ring gear 3-2 is generally smaller than the bottom diameter of the thread 3-1 to avoid interference with the screw thread, and it is mainly used to bear the axial force and part of the possible radial force. To prevent the mutual sliding between the ring gear 3-2 of the roller 3 and the ring gear of the nut, the diameter ratio of the two is generally the same as the ratio of the number of teeth of the roller 3 to the number of teeth of the internal gear ring 4 on the nut 2; the outside of the ring gear 3-2 is a gear structure, and the transmission ratio of this gear 3-3 needs to be specially designed to meet the constant lead; the outermost sides at both ends of the roller 3 are smooth shaft structures, which are mainly used for the installation of the planetary carrier.

[0028] As Figure 4 , as shown in the figure, the inner hole of the nut 2 mainly has three structures axially: the internal gear ring installation structure 2-1 at both ends of the nut 2, the ring gear structures 2-2 symmetrically distributed at both ends of the nut, and the relief stepped hole 2-3 in the middle section of the nut.

[0029] As Figure 5 , as shown in the figure, the shaft end of the screw 1 can be designed into any structure during actual application, and the thread of the screw 1 is a multi-start thread. To achieve the constant lead of this planetary roller screw, a specific relationship should be satisfied among the nominal diameter, number of starts of the thread of the screw 1, the thread and number of teeth of the roller, and the number of teeth of the internal gear ring.

[0030] As Figure 1 , as shown in the figure, the rollers 3 are evenly distributed around the screw 1. The middle thread meshes with the thread of the screw 1 and does not mesh with the nut. The ring gears 3-2 at both ends of the roller 3 mesh with the ring gears at both ends of the nut 2, and the outer gears 3-3 mesh with the gears of the internal gear ring 4 installed in the internal gear ring installation structure 2-1 of the nut 2. The smooth shafts 3-4 at both ends cooperate with the circular holes evenly distributed on the planetary carrier 6 to avoid mutual collision and friction between the rollers and improve the force state. The internal gear ring 4 is installed within the installation position of the nut 2 and is axially fixed by a fixed pin shaft 5. The installation positions of the left and right planetary carriers 6 for installing the internal gear ring 4, and the retaining ring 7 is installed in the groove of the internal gear ring 4, which is mainly used for the axial position fixation of the planetary carrier 6.

[0031] During the specific movement process, the roller thread meshes with the lead screw thread. The rotation of the lead screw drives the rotation of the roller. The roller gear meshes with the internal gear ring, enabling the planetary motion of the roller to conform to a specific law to meet the constant lead condition. The roller ring gear meshes with the ring gear of the nut to bear the corresponding axial force. Finally, when the lead screw rotates, the nut moves along the axis of the lead screw. The roller rotates on its own axis and makes a planetary motion around the lead screw while maintaining the same axial movement speed as the nut. Through the above-mentioned motion, the rotational motion is converted into a linear motion.

[0032] In addition to the above structural forms, the planetary roller screw can also be designed into a preloaded structural form during actual application. The preloaded structural form can generally reduce the possibility of the planetary roller screw slipping. For example Figure 6 , in addition to parts such as the lead screw 1, nut 2, roller 3, planetary carrier 6, and retaining ring 7, the new planetary roller screw with a preloaded structure also includes parts such as an adjusting shim 8 and a locking screw nut 9. By using the adjusting shim 8 and the locking screw nut 9, a certain preload force can be applied to the planetary roller screw, making the contact of the ring teeth closer, reducing the transmission clearance, and ensuring the smoothness of the transmission. In addition to this form of preloaded structure, there can also be structural forms such as elastic disc spring preloading.

Claims

1. A planetary roller screw with a gear transmission, comprising a screw, a nut, a roller, an inner gear ring, characterized in that: The middle of the roller is arranged outward in sequence as a thread, a ring tooth, a gear and an optical axis. The inner hole of the nut has three structures in the axial direction, including an inner gear ring mounting structure located at both ends of the nut, a ring tooth structure symmetrically distributed at both ends of the nut and an avoidance step hole in the middle section of the nut. The rollers are evenly distributed around the lead screw, the middle thread is meshed with the thread of the lead screw but not with the nut, the ring teeth at both ends of the roller are meshed with the ring teeth at both ends of the nut, the outer gear of the roller is meshed with the gear of the inner gear ring installed in the inner gear ring mounting structure of the nut, and the optical axis at both ends of the roller is matched and connected with the circular holes evenly distributed on the planetary carrier. The outer diameter of the ring tooth of the roller is smaller than the bottom diameter of the middle thread of the roller to avoid interference with the lead screw thread, and is used to bear axial force and part of the radial force. The ratio of the diameter of the ring tooth of the roller to the ring tooth of the nut is the same as the ratio of the number of teeth of the roller to the number of teeth of the inner gear ring on the nut.

2. The planetary roller screw with gear transmission according to claim 1, characterized in that: The inner gear ring is installed in the inner gear ring installation structure of the nut and is axially fixed by a fixed shaft pin.

3. The planetary roller screw with gear transmission according to claim 1, characterized in that: The left and right planet carriers are installed at the mounting position of the inner gear ring, and a retaining ring is installed in the groove of the inner gear ring to fix the axial position of the planet carrier.

4. The planetary roller screw with gear transmission according to claim 1, characterized in that: The thread of the roller is a single-start thread, and the pitch of the thread is the same as the pitch of the lead screw thread.

5. The planetary roller screw with gear transmission according to claim 1, characterized in that: The thread of the lead screw is a multi-start thread.

6. The planetary roller screw with gear transmission according to claim 1, characterized in that: When the lead screw rotates, the nut moves along the lead screw axis, and the roller rotates while performing planetary motion around the lead screw, maintaining the same axial movement speed as the nut, thereby converting the rotational motion into linear motion.

7. The planetary roller screw with gear transmission according to claim 1, characterized in that: The planetary roller screw of the gear transmission method is also provided with a locking pre-tightening structure, which is composed of an adjusting gasket and a locking screw nut. The adjusting gasket is placed between two nuts, and the two nuts are connected by a locking screw nut. A pre-tightening force is applied to the planetary roller screw by the locking screw nut, so that the contact between the nut and the ring teeth of the roller is tighter, the transmission clearance is reduced, and the transmission stability is ensured.

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