JP2007263268A - Actuator for continuously variable transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size and power consumption of an electric motor, in an actuator for a continuously variable transmission, in which a moving screw body of a ball screw mechanism receives rotating power transmitted from an electric motor side and moves in an axial direction, and a movable sheave receives driving power in the axial direction of the movable screw body and moves in the axial direction. <P>SOLUTION: An intermediate shaft 9, which is only allowed to be rotated with respect to the movable sheave 3, is inserted into a cylinder inner peripheral face 5a of a housing 5. A double rows of balls 16a, 16b are held, by means of a cage 17, in a wedge space formed between an outer periphery of the intermediate shaft 9 and the cylinder inner peripheral face 5a. Normally, the balls are engaged with the wedge space by urging the double rows of balls 16a, 16b, so that the intermediate shaft 9 is locked to both sides in the axial direction with respect to reverse input in the axial direction from a movable sheave 3 side. The cage 17 can be moved integrally with a screw shaft 14 of the ball screw mechanism 6 so that the cage can be engaged with the intermediate shaft 9 in the axial direction. Therefore, when the screw shaft 14 is moved by the drive of the electric motor 4, the intermediate shaft 9 and the movable sheave 3 are integrally moved through the cage 17. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an actuator that moves a movable sheave constituting a pulley in a pair with a fixed sheave of a continuously variable transmission in an axial direction.

  As this type of transmission, there is a belt type continuously variable transmission that is employed in a drive system of an automobile. As a conventional belt-type continuously variable transmission, for example, a belt in which a transmission belt is wound between a driving side V-groove pulley and a driven side V-groove pulley connected to an output shaft that transmits power to wheels. is there.

  The main drive side V-groove pulley is composed of a fixed sheave and a movable sheave. The fixed sheave is constrained in the axial direction, and rotational torque is transmitted from an input shaft that is rotated according to the rotational speed of the engine. The movable sheave is movable in the axial direction. When the movable sheave moves in the axial direction, the groove width of the main drive side V-groove pulley changes steplessly, and the transmission belt winding diameter changes accordingly, thereby changing the transmission ratio steplessly.

  Conventionally, as an actuator for moving the movable sheave in the axial direction, an electric motor and a ball screw mechanism are provided, and the moving screw body of the ball screw mechanism receives the rotational power transmitted from the electric motor side in the axial direction. And the movable sheave is configured to move in the axial direction in response to the axial thrust of the moving screw body.

  For example, the screw shaft of the ball screw mechanism is disposed on the same axis as the main drive side V-groove pulley, and is provided so as to restrain axial and rotational motion with respect to the housing. The nut of the ball screw mechanism is provided so as to receive the rotational power transmitted from the electric motor side. A ball interposed between the spiral groove on the inner periphery of the nut and the spiral groove on the outer periphery of the screw shaft converts rotational power into axial propulsive force, thereby moving the nut in the axial direction relative to the housing. The movable sheave can move integrally in the axial direction via the nut and a bearing. When the nut receives the rotational power transmitted from the electric motor and moves in the axial direction, the movable sheave is moved in the axial direction in response to the axial movement of the nut (see, for example, Patent Document 1).

Japanese Patent No. 2744038

  However, the movable sheave is always pushed to the side away from the fixed sheave due to the axial reaction force from the belt. For this reason, the nut of the ball screw mechanism is also pushed, and the rotational power is transmitted to the electric motor side by the good reversible conversion property of the ball, and it becomes a reverse input to the motor shaft. Therefore, in order to maintain the distance between the movable sheave and the fixed sheave, the balance between the axial reaction force of the movable sheave is always achieved by generating a holding torque in the electric motor, which increases the size and consumption of the electric motor. This has led to an increase in power.

  Accordingly, an object of the present invention is that the moving screw body of the ball screw mechanism receives the rotational power transmitted from the electric motor side and is sent in the axial direction, and the movable sheave receives the axial propulsive force of the moving screw body to In an actuator for a continuously variable transmission that moves in a direction, it is possible to reduce the size and power consumption of an electric motor.

  To achieve the above object, the present invention comprises a movable sheave that constitutes a pulley in a pair with a fixed sheave, an electric motor, and a ball screw mechanism, and the moving screw body of the ball screw mechanism is from the electric motor side. In the continuously variable transmission actuator in which the movable sheave moves in the axial direction by receiving the transmitted rotational power and the movable sheave moves in the axial direction by receiving the axial driving force of the moving screw body, the movable sheave and the bearing are interposed. A stationary shaft that is connected to the movable sheave and is capable of moving integrally with the movable sheave in the axial direction, and a cylindrical inner peripheral surface having the same center as the axis of the central shaft, and the intermediate shaft is inserted into the inner peripheral surface of the cylinder. And a cage that is provided so as to be movable integrally with the moving screw body in the axial direction, and that equally distributes double rows of balls in the circumferential direction between the outer periphery of the central shaft and the inner peripheral surface of the cylinder, A pair of axial directions is provided on the outer periphery of the central shaft. A conical engagement surface is formed so as to be continuous on the small diameter side, and the pocket of the cage is formed in the double row in a wedge space formed between the pair of engagement surfaces and the cylindrical inner peripheral surface. The double rows of balls are urged in a direction to engage with the wedge space by an elastic member interposed therebetween, and the cage that moves integrally with the moving screw body includes The configuration is such that the ball on the rear side in the moving direction is pushed to release the engagement with the wedge space and engage with the middle shaft in the axial direction.

An actuator for a continuously variable transmission according to the present invention includes a movable sheave constituting a pulley in pair with a fixed sheave, an electric motor, and a ball screw mechanism, and a moving screw body of the ball screw mechanism is transmitted from the electric motor side. In the continuously variable transmission actuator in which the movable sheave is moved in the axial direction by receiving the rotational power and the movable sheave is moved in the axial direction by receiving the axial propulsive force of the moving screw body, It has a central shaft that is connected and can move integrally with the movable sheave in the axial direction, and a cylindrical inner peripheral surface that is provided at the same center as the axis of the central shaft, and the central shaft is inserted inside the cylindrical inner peripheral surface. A stationary member, and a cage that is provided so as to be capable of moving integrally with the moving screw body in the axial direction, and equally distributes double rows of balls in the circumferential direction between the outer periphery of the central shaft and the inner peripheral surface of the cylinder. On the outer periphery of the central shaft A pair of conical engagement surfaces in the axial direction are formed so as to be continuous on the small diameter side, and the pocket of the cage is a wedge space formed between the pair of engagement surfaces and the cylindrical inner peripheral surface The double-row balls are held in the double-row balls, and the double-row balls are urged in a direction to engage with the wedge space by an elastic member interposed between them. Between the stationary member, the axial reaction force of the movable sheave transmitted through the bearing locks the axial reaction of the movable sheave transmitted to the intermediate shaft. A linear clutch is provided for transmission to the stationary member side. For this reason, the axial reaction force of the movable sheave does not reach the ball screw mechanism.
Therefore, it is not necessary to balance the axial reaction force of the movable sheave by generating a holding torque in the electric motor, and the electric motor can be reduced in size and power consumption compared to the conventional example.

  Here, in a state where the electric motor is stopped and the middle shaft is stopped with respect to the axial movement, the double row balls are engaged with the wedge space by the urging force of the elastic member. That is, when the movable sheave tries to move in the axial direction, the middle shaft that can move integrally with the movable sheave in the axial direction also moves in the axial direction, but is instantly locked by the engagement of the ball. Therefore, when the linear clutch is engaged as described above, generation of vibration can be prevented, and fine movement wear of the pair of engagement surfaces can be prevented.

  Further, in the continuously variable transmission actuator according to the present invention, the cage that moves integrally with the moving screw body releases the engagement with the wedge space by pushing the ball on the rear side in the moving direction, and the intermediate shaft and the shaft By adopting a configuration that engages in the direction, the cage that moves integrally with the moving screw body that receives the rotational power on the electric motor side releases the engagement of the ball on the side that prevents the movement of the center shaft. Then, it engages with the middle shaft and transmits axial propulsive force to the middle shaft. For this reason, the movable sheave can be moved by driving the electric motor.

Specifically, an engaging portion that is axially opposed to each other is provided on the inner periphery of the cage and the outer periphery of the middle shaft, and an axis that is larger than the axial pocket clearance of the pocket between both engaging portions. A configuration in which a directional gap is provided can be employed.
According to this configuration, while the cage and the middle shaft are engaged, and the ball on the opposite side to the moving direction tries to engage the wedge space while the middle shaft and the cage are moving together. The cage does not allow it to hit first, and the ball opposite to the moving direction and the wedge space are not repeatedly engaged and disengaged, resulting in lower vibration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The best embodiment of the present invention will be described below with reference to the accompanying drawings.
As schematically shown in FIG. 1, the continuously variable transmission actuator according to this embodiment is applied to a belt-type continuously variable transmission, and fixes a driving side V-groove pulley around which a transmission belt 1 is wound. A movable sheave 3 configured as a pair with the sheave 2, an electric motor 4, a housing 5 to which the electric motor 4 is fixed, and a ball screw mechanism 6 attached in the housing 5 are provided.

  The fixed sheave 2 is constrained in the axial direction with respect to the housing 5, and the shaft portion 2a is supported on the housing 5 by a bearing 7a on one end side and on the fixed side by a bearing 7b that makes a pair with the bearing 7a. It is supported. Rotational torque is transmitted to the shaft portion 2a from an input shaft (not shown) that is rotated according to the rotational speed of an engine (not shown).

  The movable sheave 3 is arranged coaxially with the fixed sheave 2, and its inner peripheral portion 3a is fitted to the shaft portion 2a of the fixed sheave 2 so as to be slidable in the axial direction by a ball spline. Thereby, the movable sheave 3 can move in the axial direction with respect to the fixed sheave 2 and can rotate integrally.

  The housing 5 has a cylindrical inner peripheral surface 5a provided at the same center as the axis of the movable sheave 3, and this cylindrical portion is detachable. An inner shaft 9 connected via a bearing 8 fitted to the inner peripheral portion 3a of the movable sheave 3 is inserted inside the cylindrical inner peripheral surface 5a. The shaft portion 2 a of the fixed sheave 2 is inserted through the inner periphery of the middle shaft 9. The movable sheave 3 and the middle shaft 9 are in a connected state in which the movable sheave 3 is only allowed to rotate relative to the middle shaft 9 by the intervention of the bearing 8, and the three and the nine are moved integrally in the axial direction. The middle shaft 9 itself is not rotated.

  In the electric motor 4, the motor shaft is disposed in parallel with the axis of the fixed sheave 2 and is fixed to the housing 5. A drive gear 4 a provided on the motor shaft of the electric motor 4 meshes with an intermediate gear 11 that is rotatably supported by a pair of bearings 10 a and 10 b with respect to the housing 5.

  The nut 12 of the ball screw mechanism 6 is composed of an annular body disposed coaxially with the fixed sheave 2, has a spiral groove on the inner periphery thereof, and has a driven gear 12a on the outer periphery thereof. The nut 12 is attached to the housing 5 via a pair of bearings 13 a and 13 b, and the axial movement is restricted with respect to the housing 5.

  The screw shaft 14 of the ball screw mechanism 6 has a spiral groove corresponding to the spiral groove of the nut 12 on the outer periphery thereof.

  The driven gear 12a meshes with the intermediate gear 11, and receives rotational power transmitted by the drive gear 4a through the intermediate gear 11 when the electric motor 4 rotates. A ball 15 interposed between the screw shaft 14 and the spiral groove of the nut 12 converts the rotational power into an axial propulsive force, whereby the screw shaft 14 moves in the axial direction with respect to the housing 5.

  The screw shaft 14 is integral with a cage 17 that holds double-row balls 16 a and 16 b between the outer periphery of the middle shaft 9 and the cylindrical inner peripheral surface 5 a of the housing 5. Note that the cage 17 and the screw shaft 14 may be provided separately and connected directly or via an intermediate member.

  The cage 17 has a cup shape into which the middle shaft 9 is inserted from the tip side. A pair of conical engagement surfaces 18a and 18b in the axial direction is formed on the outer periphery of the insertion portion of the middle shaft 9 into the cage 17. Is formed to be continuous on the small diameter side.

  As shown in FIG. 2, the retainer 17 has pockets 17a in which the double rows of balls 16a and 16b are equally arranged in the circumferential direction. As shown in FIG. 1, the pocket 17a has the pair of engaging surfaces. The double row balls 16a and 16b are held in a wedge space formed between 18a and 18b and the cylindrical inner peripheral surface 5a.

  FIG. 3A is an enlarged view of the pocket 17a in a state where the electric motor 4 and the movable sheave 3 are stopped with the cage 17 as the center. As shown in FIG. 3A, the double rows of balls 16a and 16b held in the pocket 17a are urged in an orientation to engage with the wedge space by an elastic member 19 interposed therebetween.

  The convex engaging portion 20 a that protrudes to the inner periphery of the cage 17 is fitted into a concave engaging portion 20 b provided on the outer periphery of the middle shaft 9. In this embodiment, the convex engaging portion 20 a is made of a transmission member press-fitted to the cage 17, and the concave engaging portion 20 b is made of a concave hole formed on the outer periphery of the middle shaft 9.

  The convex engaging portion 20a and the concave engaging portion 20b are always engaged in the rotational direction and the radial direction, and are provided so as to face each other in the axial direction, and between the engaging portions 20a and 20b, An axial gap δb larger than the axial pocket gap δa of the pocket 17a is provided.

  Here, from the state of FIG. 3A, the electric motor 4 rotates forward or backward, the nut 12 receives the rotational power transmitted through the intermediate gear 11 by the driven gear 12a, and the screw shaft 14 In the drawing, when moved to the right in the axial direction, the retainer 17 also moves to the right in the axial direction together with the screw shaft 14.

  Then, as shown in FIG. 3B, when the cage 17 has moved the distance of δb / 2, it has already moved the distance of the axial pocket gap δa / 2 and is the rear side in the integral movement direction. The ball 16a is pushed to release the engagement with the wedge space. Further, when the retainer 17 moves in the same direction, the convex engaging portion 20a and the concave engaging portion 20b are engaged in the axial direction, so that axial propulsive force is transmitted to the intermediate shaft 9, and the intermediate shaft 9 is movable. The sheave 3 is integrally moved to the right in the axial direction by the connection via the bearing 8.

  Here, while the cage 17 and the middle shaft 9 are integrally moving, even if the ball 16a on the rear side in the integral movement direction tries to engage with the wedge space, the cage 17 hits first to allow it. First, the integral movement of the middle shaft 9 and the movable sheave 3 continues. Accordingly, the ball 16a on the rear side in the integral movement direction and the wedge space are not repeatedly engaged / disengaged, and vibration input to the screw shaft 14 is prevented. In addition, when the electric motor 4 is rotated reversely to the above, the series of operations described above are only reversed and the description thereof is omitted. 1, the state in which the movable sheave 3, the middle shaft 9, and the screw shaft 14 are located on the rightmost side in the axial direction is indicated by a solid line, and the state that is located on the leftmost side in the axial direction is indicated by a one-dot chain line.

  On the other hand, in the above configuration, when the movable sheave 3 is rotated and the electric motor 4 is stopped, the middle shaft 9 itself is not rotating, and the double-row balls 16a and 16b are engaged with the wedge space. Therefore, even if the movable sheave 3 and the middle shaft 9 try to move together in the axial direction, the middle shaft 9 is instantly locked in the axial direction. That is, the movable sheave 3 and the middle shaft 9 do not move in the axial direction.

  Therefore, in this embodiment, it is not necessary to generate a holding torque in the electric motor 4 to prevent the nut 12 from rotating, and the electric motor 4 can be reduced in size and power consumption can be reduced.

  The pair of engaging surfaces 18a and 18b only need to form a wedge space between which the double-row balls 16a and 16b can engage with the cylindrical inner peripheral surface 5a, and have a tapered curved surface. It is also possible.

  In this embodiment, the screw shaft 14 can be a fixed side, and the nut 12 can be a moving side that receives the rotational power of the electric motor 4.

Schematic longitudinal sectional view of an actuator for continuously variable transmission according to an embodiment The expanded fragmentary sectional view in the arrow line of the holder | retainer of FIG. (A) Operational diagram showing the double-row balls and wedge spaces in FIG. 1 with the electric motor and movable sheave stopped, (b) the cage from the state in FIG. 3 (a) in the direction of the arrow in the figure. Action diagram showing the state when moved

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission belt 2 Fixed sheave 2a Shaft part 3 Movable sheave 3a Inner peripheral part 4 Electric motor 4a Drive gear 5 Housing (stationary member)
5a Cylindrical inner peripheral surface 6 Ball screw mechanism 7a, 7b Bearing 8 Bearing 9 Middle shaft 10a, 10b Bearing 11 Intermediate gear 12 Nut 12a Driven gear 13a, 13b Bearing 14 Screw shaft (moving screw body)
15 balls 16a and 16b double row balls 17 cages 18a and 18b a pair of engaging surfaces 19 elastic member 20a convex engaging portion 20b concave engaging portion

Claims (2)

A movable sheave that constitutes a pulley in a pair with a fixed sheave, an electric motor, and a ball screw mechanism, and the moving screw body of the ball screw mechanism moves in the axial direction by receiving the rotational power transmitted from the electric motor side In the continuously variable transmission actuator in which the movable sheave moves in the axial direction in response to the axial driving force of the moving screw body,
A middle shaft that is connected to the movable sheave via a bearing and is movable integrally with the movable sheave in the axial direction;
A stationary member having a cylindrical inner circumferential surface having the same center as the axis of the middle shaft, and the middle shaft inserted into the inner circumferential surface of the cylinder;
A cage that is provided so as to be integrally movable in the axial direction with the moving screw body, and that equally distributes double rows of balls in the circumferential direction between the outer periphery of the central shaft and the inner peripheral surface of the cylinder;
A pair of conical engagement surfaces in the axial direction are formed on the outer periphery of the middle shaft so as to be continuous on the small diameter side, and the pocket of the cage is between the pair of engagement surfaces and the inner peripheral surface of the cylinder. The double row balls are held in the wedge space formed in the double row ball, and the double row balls are urged to engage with the wedge space by an elastic member interposed therebetween,
The continuously variable transmission characterized in that the cage that moves integrally with the moving screw body pushes a ball on the rear side in the moving direction to release the engagement with the wedge space and engages with the middle shaft in the axial direction. Actuator for machine.   Engagement portions facing each other in the axial direction are provided on the inner periphery of the cage and the outer periphery of the middle shaft, and an axial clearance larger than the axial pocket clearance of the pocket is provided between the engagement portions. The continuously variable transmission actuator according to claim 1.

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