JP4969385B2 - CVT actuator - Google Patents

Description

The present invention is used in, for example, an actuator such as a sheave drive mechanism of a V-belt type continuously variable transmission of an automobile, and a ball screw in which a spiral thread groove on which a large number of balls roll is formed. and sunk into the inner diameter side of the screw shaft are connected by a ball circulation groove for returning from the downstream side to the upstream side, to a actuator of the continuously variable transmission equipped with a the ball screw of so-called axis circulation type.

  A ball screw has a ball screw shaft composed of a ball screw shaft having a spiral thread groove formed on the outer periphery, a ball screw nut having a spiral thread groove formed in a cylindrical surface, and both opposing screw grooves. It is a mechanical element that is composed of a large number of balls that are rotatably accommodated in the road, and converts the rotation of the ball screw shaft or ball screw nut into translational motion in the axial direction.

  Conventionally, in order to prevent a large number of balls contained in the respective screw grooves from being pulled out regardless of the expansion and contraction movement of the screw shaft and the nut, the ball screw has a screw groove of the screw shaft and a screw groove of the nut. Both ends of the ball rolling path constituted by the above are connected in communication to form a closed loop, and the ball is infinitely circulated in the closed loop.

Such a ball screw has various ball circulation mechanisms, for example, various types called a return tube, an end plate, or a piece type. Such a ball screw has, for example, a V as shown in FIG. It is used in the sheave drive mechanism 51 of the belt type continuously variable transmission 50. The sheave drive mechanism 51 is mounted on the outer periphery of the primary sheave shaft 52 so as to be movable by spline fitting, and is also freely rotatable via a bearing 55 around the slider 54 to which the movable sheave 53 is fixed. , And the relative movement in the axial direction with respect to the slider 54 is restricted, so that the rotary sheave 53 is connected to the movable sheave 53 of the primary sheave 56 so as to be rotatable and integrally movable in the axial direction. Nut) 57, a reciprocating gear 58 fixed to the rotary slide member 57, a feed guide cylinder (screw shaft) 59 disposed concentrically inside the rotary slide member 57, a feed guide cylinder 59, and the rotary slide member 57. The outer periphery of the rotary slide member 57 from the fixed side end of the feed guide tube 59. And a bottomed cylindrical outer member 61 and an oil seal 63 provided between the rotary slide member 57 and the outer member 61 so as to seal the internal space 62 of the ball screw mechanism 60. .

  The feed guide cylinder 59 moves the rotary slide member 57 in the axial direction of the primary sheave shaft 52 according to the rotation direction and the rotation amount of the reciprocating gear 58 via a ball screw mechanism 60 that is screwed to the rotary slide member 57. The outer member 61 through which the primary sheave shaft 52 passes is bolted to a support member 64 that rotatably supports the other end of the primary sheave shaft 52 in a crankcase (not shown). The sheave drive mechanism 51 moves and adjusts the movable sheave 53 in the axial direction according to the rotation input to the reciprocating gear 58 from an electric motor (not shown) via the speed reduction mechanism.

In general, the ball screw seal is preferably disposed in an opening in an annular space formed between the nut and the screw shaft. However, a spiral screw groove is formed over the entire area of the screw shaft. Therefore, the seal needs to be disposed corresponding to the spiral thread groove. That is, the inner peripheral surface of the seal is formed in accordance with the shape of the screw groove, and the assembly needs to be mounted with the phase matched. However, like the oil seal 63 described above, the rotation constituting the ball screw mechanism 60 is performed. The outer member 61 is provided separately from the slide member 57, and by mounting on the outer member 61, the shape of the oil seal 63 can be simplified and the cost can be reduced, and the number of assembly steps of the oil seal 63 can be reduced. (For example, refer to Patent Document 1).
JP 2007-71255 A

  However, in such a conventional ball screw mechanism 60, an outer member 61, which is a separate member, is required to seal the internal space 62 of the ball screw mechanism 60, which not only hinders downsizing, but also the oil seal 63 rotates and slides. Since it is arranged at a position far from the opening of the annular space formed between the member (nut) 57 and the feed guide cylinder (screw shaft) 59, the grease filled in the ball screw mechanism 60 The effect of preventing leakage is halved.

The present invention has been made in view of such conventional problems, aims to provide with downsized, the actuator of the continuously variable transmission having a ball screws which aimed at sealing of effectively seal And

According to an aspect of an invention of claim 1 of the present invention, the distance between the movable sheave and the fixed sheave is changed appropriately, the diameter of the V-belt passed over in the sieve is adjusted steplessly The actuator of the continuously variable transmission is mounted on the outer periphery of the sheave shaft so as to be movable in the axial direction. comprising a gear, a linked ball Lumpur screw on the slider, the ball screw, a cylindrical nut with a helical screw groove is formed on the inner periphery, is inserted into the nut, the the outer periphery A screw shaft having a plurality of screw grooves having the same lead angle as the lead angle of the screw groove, and a plurality of balls accommodated in a freely rollable manner between the two screw grooves, and the axial direction of the screw shaft Between adjacent screw grooves The land portion is provided with a ball circulation groove in which the plurality of screw grooves are individually closed loops. The ball circulation groove sinks the ball downstream of the screw groove to the inner diameter side, and overcomes the land portion of the nut. The seal is attached to the opening of the annular space formed between the nut and the screw shaft, and the seal extends in a bifurcated shape toward the inner diameter side. A radial lip is integrally formed, is slidably contacted with the outer peripheral surface of the screw shaft, and the screw shaft of the ball screw is connected to the outer periphery of the slider so as not to rotate and to be movable in the axial direction. but by the relative movement in the axial direction with respect to the sheave shaft is restricted, with respect to the movable sheave, rotatably, and is configured to immovably in the axial direction, the fixing bolt the nut, which is fastened to the flange portion Through and is fixed to the gear.

As described above, in the actuator of the continuously variable transmission, the outer periphery of the sheave shaft is mounted so as to be movable in the axial direction. And a ball screw connected to the slider. The ball screw is inserted into the cylindrical nut having a spiral thread groove on the inner periphery, and the screw groove is disposed on the outer periphery. A screw shaft having a plurality of screw grooves formed with the same lead angle as the lead angle, and a plurality of balls accommodated in a freely rollable manner between the two screw grooves, and adjacent to each other in the axial direction of the screw shaft A ball circulation groove having the plurality of screw grooves individually as closed loops is provided in the land portion existing between the two and the ball circulation groove. Over the club The seal is attached to the opening of the annular space formed between the nut and the screw shaft, and the seal is integrated with a radial lip that is bifurcated on the inner diameter side. The ball screw screw shaft is connected to the outer periphery of the slider so as to be non-rotatable and movable in the axial direction, and the nut is relative to the slider in the axial direction. By restricting the movement, the movable sheave is configured to be rotatable and non-movable in the axial direction, and this nut is fixed to the gear via a fixing bolt fastened to the flange portion. It is possible to provide an actuator for a continuously variable transmission that is compact and has improved sealing performance.

An actuator of a continuously variable transmission according to the present invention is an actuator of a continuously variable transmission in which a distance between a movable sheave and a fixed sheave is appropriately changed and a diameter of a V-belt stretched over the sheave is continuously adjusted. The slider is mounted on the outer periphery of the sheave shaft so as to be movable in the axial direction. and a ball Lumpur screw, the ball screw, a cylindrical nut with a helical screw groove is formed on the inner periphery, is inserted into the nut, the screw groove on the outer peripheral lead angle identical to the A screw shaft in which a plurality of screw grooves each having a lead angle are formed; and a plurality of balls that are rotatably accommodated between the two screw grooves; and between adjacent screw grooves in the axial direction of the screw shaft. In the existing land part, A ball circulation groove is provided in which a plurality of screw grooves are individually closed loops, and the ball circulation groove sinks the ball downstream of the screw groove to the inner diameter side and moves over the land portion of the nut to the upstream side. A seal is attached to the opening of the annular space formed between the nut and the screw shaft, and a radial lip extending in a bifurcated shape on the inner diameter side is integrated. The ball screw screw shaft is connected to the outer periphery of the slider in a non-rotatable and axially movable manner, and the nut is connected to the sheave shaft. By restricting the relative movement in the axial direction with respect to the movable sheave, the movable sheave is configured to be rotatable and non-movable in the axial direction. The nut is connected to the gear via a fixing bolt fastened to the flange portion. Because it is fixed, the downsized, it is possible to provide an actuator of the continuously variable transmission with improved sealability.

  A cylindrical nut having a helical thread groove formed on the inner periphery, and a screw shaft that is inserted into the nut and has a plurality of thread grooves having the same lead angle as the lead angle of the thread groove on the outer periphery. And a plurality of balls accommodated in a freely rollable manner between the two screw grooves, and the plurality of screw grooves are individually formed in land portions existing between adjacent screw grooves in the axial direction of the screw shaft. A ball circulation groove serving as a closed loop is provided, and this ball circulation groove is substantially S-shaped so that the ball downstream of the screw groove is sunk to the inner diameter side, gets over the land portion of the nut and returns to the upstream side. The screw groove is formed of a limited or two closed spiral groove, and a seal is attached to the opening of the annular space formed between the nut and the screw shaft. Radius in which the seal is formed to extend in a forked shape on the inner diameter side It has a lip integrally and are in sliding contact with the outer peripheral surface of the screw shaft.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of a main part showing an embodiment of an actuator of a continuously variable transmission to which a ball screw according to the present invention is applied, FIG. 2 is an enlarged view of a main part of FIG. 1, and FIG. 4 is a conceptual diagram showing a ball screw, FIG. 4 is a cross-sectional view of FIG. 3, FIG. 5 is an explanatory view showing a machining state of a screw groove in the screw shaft of FIG. 3, and FIG. (B) is an enlarged cross-sectional view showing a machining process of the screw groove, FIG. 7 (a) is an enlarged cross-sectional view of the screw groove made of a gothic arc shape on the screw shaft, b)-(d) is an expanded sectional view which shows the manufacturing process of a thread groove.

An actuator 1 of a continuously variable transmission shown in FIG. 1 is mounted on the outer periphery of a sheave shaft (main shaft) 2 so as to be movable in the axial direction via a spline 3, and a slider having a movable sheave (not shown) fixed thereto. 4 and a cylindrical screw shaft 6 which is connected to the outer periphery of the slider 4 via a rolling bearing 5 so as not to rotate and to be movable in the axial direction, and to the screw shaft 6 via a plurality of balls 7. The ball screw 9 including the nut 8 configured to be rotatable with respect to the movable sheave and not movable in the axial direction, and the sheave shaft 2 , are fitted and restricted relative to the sheave shaft 2 in the axial direction. A gear 11 is rotatably provided on the outer periphery via a rolling bearing 10. The nut 8 is fixed to the gear 11 via a fixing bolt 12 fastened to the flange portion 8 b and rotates integrally with the gear 11. Reference numeral 13 denotes a rotation stop member that is engaged with a case (not shown) via the fixing bolt 12 with the screw shaft 6 and restricts the rotation of the screw shaft 6.

  When a rotational force from a drive motor (not shown) is input to the gear 11, the nut 8 rotates and the screw shaft 6 starts moving in the axial direction (left direction in the figure) (indicated by a two-dot chain line in the figure). . Along with this, the movable sheave is driven in the axial direction via the slider 4. At this time, the distance between the movable sheave and the fixed sheave (not shown) is appropriately changed in accordance with the amount of movement of the screw shaft 6, and the diameter of the V-belt spanned over the sheave is adjusted steplessly.

  As shown in FIGS. 3 and 4, in the ball screw 9 in the present embodiment, the screw grooves 6 a and 6 b of the screw shaft 6 are constituted by two or three closed (here, two) closed spiral grooves. It is composed of a shaft circulation type, and includes a cylindrical nut 8, a screw shaft 6 inserted in the nut 8, a large number of balls 7 accommodated between the screw shaft 6 and the nut 8, and these balls 7. A retainer ring 14 that is held in a circumferentially equidistant manner and a seal 15 that will be described later are provided. The cage ring 14 is attached in a state where it is positioned so as to be substantially immovable in the axial direction with respect to the screw shaft 6 and is relatively rotatable.

  The nut 8 is made of case-hardened steel such as SCM415 or SCM420, and a spiral thread groove 8a is formed on the inner periphery thereof. On the other hand, the screw shaft 6 is made of medium carbon steel such as S55C or case-hardened steel such as SCM415, and a plurality (two turns here) of thread grooves 6a and 6b that are not continuous in the axial direction are formed on the outer periphery. Yes. The thread groove 8a of the nut 8 and the thread grooves 6a and 6b of the screw shaft 6 are set to the same lead angle θ. The thread grooves 8a, 6a, and 6b are formed in a so-called gothic arc shape in which two arcs having a curvature radius slightly larger than the radius of the ball 7 are combined. Of course, the thread grooves 8a, 6a and 6b may have a circular arc shape which has a radius of curvature slightly larger than the radius of the ball 7 and makes an angular contact with the ball 7 in addition to the gothic arc shape.

  The plurality of thread grooves 6a and 6b are closed loops, and the balls 7 respectively accommodated in the thread grooves 6a and 6b are independently configured to endlessly circulate. That is, as shown in FIG. 3, a ball circulation groove 17 in which a plurality of screw grooves 6 a and 6 b are individually closed loops in a land portion 16 existing between screw grooves 6 a and 6 b adjacent in the axial direction of the screw shaft 6. , 18 are provided.

  The ball circulation grooves 17 and 18 individually connect the upstream side and the downstream side of the thread grooves 6a and 6b. The balls 7 downstream of the thread grooves 6a and 6b are sunk into the inner diameter side, and nuts It is formed in a substantially S shape meandering so as to get over the eight land portions 19 and return to the upstream side. Therefore, the depth of the ball circulation grooves 17 and 18 is set to such a depth that the ball 7 can get over the land portion 19 of the screw groove 8a in the nut 8 in the ball circulation grooves 17 and 18 (see FIG. 4).

  FIG. 5 shows a processed state of the thread grooves 6 a and 6 b in the screw shaft 6. A raw material bar-shaped workpiece W (6) is gripped by a spindle chuck 20 of a lathe and turned by a ball end mill 21 while being rotated synchronously in a predetermined direction. The ball end mill 21 is supported so as to be movable forward and backward in the radial direction and movable in the axial direction, and is positioned by NC control. Turning of the thread grooves 6a and 6b is performed by so-called point cutting. That is, as shown in FIG. 6A, when the thread groove 6a (6b) has a circular arc shape, the ball end mill 21 having the same nose radius R2 as the groove curvature radius R1 of the thread groove 6a is used. As shown in (b), the ball end mill 21 is fed in the radial direction to form the thread groove 6a having a predetermined shape.

  On the other hand, as shown in FIG. 7, when the thread groove 6a (6b) has a Gothic arc shape, the ball end mill 21 has a nose radius R4 smaller than the groove curvature radius R3 of the thread groove 6a. As shown in (d) to (d), the ball end mill 21 is moved a plurality of times by the effective length of the thread groove 6a, and the thread groove 6a having a predetermined shape is formed by overlapping a plurality of trajectories of the ball end mill 21. .

  By setting the nose radius R4 of the ball end mill 21 close to the groove curvature radius R3 of the thread groove 6a, the rough shape of the thread groove 6a can be obtained without moving the ball end mill 21 in the axial direction, and the processing time Can be shortened.

  Moreover, in this embodiment, after completing the shaping | molding process of the some thread groove 6a, 6b by point cutting, the hardened layer of the range of 55-62HRC is formed in the surface by heat processing. The heat treatment may be carburization quenching or quenching by high frequency induction heating, but it is preferable to use induction hardening that can suppress the grain boundary oxide layer on the surface layer and that can locally heat and set the hardened layer depth relatively easily. .

Further, finish processing (not shown) by shot peening is performed in order to remove scale and surface grain boundary oxide layers adhering to the screw grooves 6a, 6b and the like by heat treatment. In this shot peening, the particle size of the steel beads was 20 to 100 μm, the injection time was about 90 seconds, the injection pressure was 1 to 3 kg / cm ² , and the distance between the injection nozzle and the surface of the workpiece was about 140 mm. Thereby, the durability of the ball screw 9 can be improved.

  Here, as shown in an enlarged view in FIG. 2, the ball screw 9 is provided with a seal 15 in an opening of an annular space formed between the nut 8 and the screw shaft 6. The seal 15 is made of an elastic member such as nitrile rubber, and has a base 23 fitted in an annular groove 22 formed on the inner periphery of one end of the nut 8, and a radial lip 24 extending in a forked shape from the base 23 toward the inner diameter side, 25. And these radial lips 24 and 25 are slidably contacted with the outer peripheral surface of the screw shaft 6 via a predetermined shimiro. By using such a seal 15 having the bifurcated radial lips 24, 25, the grease enclosed in the ball screw 9 leaks to the outside, and foreign matters such as rainwater and dust enter the inside from the outside. Can be effectively prevented.

  In this embodiment, since the screw grooves 6a and 6b of the screw shaft 6 are constituted by two limited closed spiral grooves, a sliding lip for a cylindrical surface using the land portion 16 of the screw shaft 6 is used. A seal 15 can be arranged. Therefore, it is not necessary to arrange the seal 15 corresponding to the spiral thread groove and to form the inner peripheral surface of the seal 15 in accordance with the shape of the thread groove, and the shape of the seal 15 is simplified. The number of assembly steps of the seal 15 can be reduced, and the cost can be reduced. Further, unlike the conventional case, there is no need for a separate outer member for covering the ball screw, and it is possible to achieve compactness, and it is not necessary to dispose the seal 15 at a position far away from the screw grooves 6a and 6b. In particular, it is possible to provide a ball screw 9 that prevents leakage of grease and improves the sealing performance of the seal 15.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

The actuator of the continuously variable transmission according to the present invention can be applied to the actuator of the continuously variable transmission of an automobile equipped with axial circulation type ball screw.

It is principal part sectional drawing which shows one Embodiment of the actuator of the continuously variable transmission to which the ball screw which concerns on this invention was applied. It is a principal part enlarged view of FIG. It is a conceptual diagram which shows the ball screw of FIG. It is a cross-sectional view of FIG. It is explanatory drawing which shows the processing state of the thread groove in the screw shaft of FIG. (A) is an expanded sectional view of the thread groove which consists of the circular arc shape in a screw shaft. (B) is an expanded sectional view which shows the manufacturing process of a screw groove same as the above. (A) is an expanded sectional view of the thread groove which consists of a Gothic arc shape in a screw axis. (B)-(d) is an expanded sectional view which shows the manufacturing process of a screw groove same as the above. It is principal part sectional drawing which shows the sheave drive mechanism of the conventional V belt type continuously variable transmission.

Explanation of symbols

1 .... Actuator of continuously variable transmission 2 .... Sheave shaft 3 .... Spline 4 .... .... Sliders 5, 10 ... Rolling bearings 6 ... Screw shafts 6a, 6b, 8a ... Screw grooves 7 ... ... Ball 8 ... Nut 8b ... Flange 9 ... Ball screw 11 ............ Gear 12 ............ Fixing bolt 13 ............ Rotation stop member 14 ............ Hold Ring 15 ... Seal 16, 19 ... Land 17 and 18 ... Ball circulation groove 20 ... Spindle chuck 21 End mill 22 ... annular groove 23 ... base 24, 25 ... radial lip 50 ... V Belt type continuously variable transmission 51 ... Sheave drive mechanism 52 ... Primary sheave shaft 53 ... Movable sheave 54 ... ... Slider 55 ... Bearing 56 ... Primary sheave 57 ... Rotating slide member 58 ··········· Reciprocating gear 59 ································································ Ball screw mechanism 61 Outer member 62... Internal space 63... Oil seal 64... Support members R 1, R 3. Curvature of the ... screw groove radius R2, R4 ······· nose radius W ··········· rod-like work θ ··········· lead angle of the ball end mill

Claims (1)

In the actuator of the continuously variable transmission, the interval between the movable sheave and the fixed sheave is appropriately changed, and the diameter of the V-belt spanned over the sheave is adjusted steplessly.
A slider which is mounted on the outer periphery of the sheave shaft so as to be movable in the axial direction, and the movable sheave is fixed;
A gear rotatably supported on the outer periphery of the sheave shaft via a rolling bearing;
And a concatenated ball Lumpur screw on the slider,
This ball screw has a cylindrical nut with a spiral thread groove formed on the inner periphery;
A screw shaft that is inserted into the nut and has a plurality of screw grooves formed on the outer periphery with the same lead angle as the lead angle of the screw groove;
A plurality of balls accommodated in a freely rollable manner between the both screw grooves,
A ball circulation groove having the plurality of screw grooves individually as closed loops is provided in a land portion existing between adjacent screw grooves in the axial direction of the screw shaft, and the ball circulation groove is disposed downstream of the screw groove. It is formed in a substantially S shape so as to sink the ball to the inner diameter side, get over the land portion of the nut and return to the upstream side, and in the opening of the annular space formed between the nut and the screw shaft A seal is mounted, and this seal integrally has a radial lip extending in a forked shape on the inner diameter side, and is in sliding contact with the outer peripheral surface of the screw shaft.
Screw shaft of the ball screw, to disable rotation on an outer periphery of the slider, and while being movably connected in the axial direction,
The nut is configured to be rotatable and non-movable in the axial direction with respect to the movable sheave by restricting the relative movement in the axial direction with respect to the sheave shaft , and the nut is fastened to the flange portion. An actuator for a continuously variable transmission, which is fixed to the gear via a fixing bolt.

Images