ROLLER SCREW AND METHOD OF CIRCULATING ROLLERS IN ROLLER SCREW

• US 20100282011A1
• Filed: 11/14/2008
• Published: 11/11/2010
• Est. Priority Date: 11/30/2007
• Status: Active Grant

• Current Assignee: THK Company Limited
• Original Assignee: THK Company Limited
• Inventors: Miura, Tetsuya, Yoshida, Akimasa, Nishimura, Kentaro, Sakuyama, Takashi, Miyahara, Soshi, Todoroki, Yusuke
• Granted Patent: US 8,739,646 B2
• Time in Patent Office: Days
• US Class Current: 74/424.82
• CPC Class Codes: F16H 2025/2271 with means for guiding circulating rollers
• CPC Class Codes: F16H 25/2247 with rollers
• CPC Class Codes: Y10T 74/19749 Recirculating rolling elements
• CPC Class Codes: Y10T 74/19772 Rolling element deflector

Abstract

There is provided a roller screw in which a twisted amount of an unloaded return path is reduced.

The roller screw has a screw shaft 1 having a spiral roller-rolling surface is on an outer peripheral surface thereof; a nut 2 having a spiral loaded roller-rolling surface 2a on an inner peripheral surface thereof, the spiral loaded roller-rolling surface being opposed to the roller-rolling surface is of the screw shaft 1; a circulation member 7 arranged in the nut 2 and formed to have an unloaded return path 8 connecting one end and the other end of the loaded roller-rolling surface 2a, whose turn number is less than one, of the nut 2; and a plurality of rollers 4 arranged in a one-turn roller circulation path composed by a loaded roller-rolling path 6 and the unloaded return path 8. The circulation member 7 guides the rollers which have moved and arrived at the one end of the loaded roller-rolling path 6 having less than one turn, to the unloaded return path 8, and then returns the rollers to the other end of the loaded roller-rolling path 6 having less than one turn. The number of turns of the loaded roller-rolling path 6 is set to be less than one turn, whereby the rollers 4 which have arrived at one end of the loaded roller-rolling path 6 can be transferred to the other end of the loaded roller-rolling path 6 without changing their attitudes.

Claims

1. A roller screw comprising:

a screw shaft having a spiral roller-rolling surface on an outer peripheral surface thereof;

a nut having a spiral loaded roller-rolling surface on an inner peripheral surface thereof, the loaded roller-rolling surface being opposed to the roller-rolling surface of the screw shaft;

a circulation member arranged in the nut and formed to have an unloaded return path connecting one end and the other end of the loaded roller-rolling surface, whose turn number is less than one, of the nut; and

a plurality of rollers arranged in a one-turn roller circulation path composed by a loaded roller-rolling path having less than one turn between the roller-rolling surface of the screw shaft and the loaded roller-rolling surface of the nut and an unloaded return path of the circulation member,

wherein the circulation member is formed to guide the rollers which have rolled and arrived at one end of the loaded roller-rolling path of less than one turn to the unloaded return path and to return the rollers to the other end of the loaded roller-rolling path of less than one turn, when the screw shaft is relatively rotated to the nut.

2. The roller screw of claim 1, wherein the unloaded return path of the circulation member has a cross section closed to enclose the rollers, and the circulation member has scooping-up portions arranged at both ends of the unloaded return path in a length direction thereof, the scooping-up portions scooping up the rollers which have moved in the loaded roller-rolling path into the unloaded return path.

3. The roller screw of claim 2, wherein the unloaded return path of the circulation member has the cross section which is square in conformity with a shape of a side surface of each of the rollers and which is twisted so as to rotate attitudes of the rollers which move along the unloaded return path, and the circulation member is a member formed by combining two split members split at a position of a diagonal line of the unloaded return path of which section is square.

4. The roller screw of any one of claims 1 to 3, wherein the number of turns of the loaded roller-rolling path having less than one turn is over 0.5 turns.

5. The roller screw of claim 4, wherein the nut has a placing hole which has a shape corresponding to a shape of the circulation member, which is through from an outer peripheral surface of the nut to an inner peripheral surface thereof, and which extends in a long and thin form from one of both ends of the loaded roller-rolling surface of less than one turn to the other end thereof, and the circulation member is placed in the placing hole of the nut.

6. A method of circulating rollers in a roller screw, guiding the rollers which have moved and arrived at one of ends of a loaded roller-rolling path having less than one turn, into an unloaded return path of the circulation member, wherein the loaded roller-rolling path is formed between a spiral roller-rolling surface on an outer peripheral surface of the screw shaft and a spiral loaded roller-rolling surface on an inner peripheral surface of a nut, and returning the rollers to the other end of the loaded roller-rolling path having less than one turn.