JP2003287100A - Linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear actuator performing highly accurate driving while retaining reliability. <P>SOLUTION: A pivot angle of a link member 19 with respect to an axis of a nut 16 is set within 10 degrees (more preferably within 5 degrees and most preferably 0 degree) in a position where driving force F applied to a driven point by the link member 19 is maximum (a state shown in Fig. 1(a)) in a range that the nut 16 and a bracket 18 are movable. This allows a direction of the driving force F to be a direction along the axis of the nut 16 by reducing the pivot angle θ when the driving force F is large, and its radial component is reduced. In contrast, as shown in Fig. 1(b), when the driving force F is small, although the radial component of the driving force F increases, as the driving force F itself decreases, moment received by the bracket 18 is resultingly reduced in total. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear actuator, for example, a power window of an automobile, a wire winding mechanism of an electric parking brake device, a caliper pushing mechanism of an electric disc brake device, and a cam phase in a valve timing varying device of an engine. The present invention relates to a linear actuator using an electric motor as a power source, which can be used in a conversion mechanism, other industrial winches, hoists, cranes, various positioning devices, and the like.

[0002]

2. Description of the Related Art For example, there is known an electric parking brake drive device that reduces the burden on a driver by operating a parking brake of a vehicle by using the power of an electric motor. As such an electric parking brake drive device,
It has been proposed that an electric motor rotates a pulley to wind up a wire to operate a parking brake, and then rewinds the wire to release the parking brake (see JP 2001-106060 A).

[0003]

The electric parking brake drive device disclosed in the above publication uses the worm gear and the worm hole to decelerate the power from the electric motor and transmit it to the parking brake. When power transmission is performed using a worm gear and a worm wheel, a large reduction ratio can be achieved, and by appropriately designing the twist angle of the worm, it is possible to prevent the power from the parking brake from being transmitted to the electric motor side. There is.

However, reversing the above advantages, the worm gear and the worm hole have the drawback of low transmission efficiency, and therefore the power of the electric motor must be increased in order to operate the parking brake. Therefore, there is a problem that the electric motor becomes large and power cannot be saved. One measure to solve such a problem is to use a ball screw mechanism capable of converting the rotational force of the electric motor in the axial direction. The ball screw mechanism can convert the rotational force into the axial force with low friction and high efficiency by the balls rolling in the spiral groove formed between the screw shaft and the nut.

However, one problem of the ball screw mechanism is that the screw shaft has to be advanced and retracted in terms of the structure, so that the supporting rigidity in the radial direction becomes low. For example, when a lever or the like is driven by a linear actuator, the lever pivots about a single point, so the driven point driven by the linear actuator draws an arc. Therefore, if only one end of the screw shaft is directly pivotally attached to the driven point of the lever, a large moment force is applied from the lever according to the advance / retreat of the screw shaft, which causes a gap between the screw shaft and the nut. The balls in the spiral groove are strongly pressed, and as a result, the life is shortened. In response to such problems, a long hole is formed in the lever, and depending on the forward and backward movement of the screw shaft,
A configuration in which one end of the screw shaft is moved along the long hole is also conceivable. According to this configuration, the moment force applied to the screw shaft can be suppressed to a low level, but the connecting portion between the relatively moving elongated hole and the screw shaft is easily worn, and rattling is likely to occur, resulting in high positional accuracy. It can be said that it is difficult to drive.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a linear actuator that can drive with high accuracy while maintaining reliability.

[0007]

A linear actuator according to a first aspect of the present invention is a linear actuator for driving a driven member in which a driven point draws a curve.
A screw shaft connected to the output shaft of the electric motor; a nut member arranged around the screw shaft; and a ball rolling in a spiral groove formed between the screw shaft and the nut member. A nut member and a pivotable link member that connects the driven point of the driven member to each other, and within the movable range of the nut member, the link member is moved to the driven point. The pivot angle of the link member with respect to the axis of the nut member is within 10 degrees at the position where the applied driving force is maximum.

The linear actuator of the second invention is
In a linear actuator for driving a driven member in which a driven point draws a curve, an electric motor, a nut connected to an output shaft of the electric motor, a screw shaft member arranged in the nut, and the screw shaft member And a ball that rolls in a spiral groove formed between the nut, the screw shaft member, and a pivotable link member that connects a driven point of the driven member, Within a range in which the screw shaft member can move, the pivot angle of the link member with respect to the axis of the screw shaft member is 10 degrees or less at a position where the driving force applied from the link member to the driven point is maximum. Is characterized in that.

[0009]

According to the linear actuator of the first aspect of the present invention, the nut member that advances and retracts in response to the rotation of the electric motor and the driven point of the driven member are connected by the link member that is pivotable. Therefore, even when the driven point moves in a curved line, the link member pivotally connects the driven point and the pivot point of the link member to the nut member. Since the driving force is applied only along the direction in which the line extends, the moment force received by the nut member can be suppressed low. However, if the angle formed by the line connecting the driven point and the pivot point of the link member and the axis of the nut member (referred to as the pivot angle) increases, the axis of the nut member with respect to the driving force is increased. The radial component increases, and as a result, the moment force received by the nut member may increase. Therefore, within the movable range of the nut member, the pivot angle of the link member with respect to the axis of the nut member is 10 degrees or less at a position where the driving force applied from the link member to the driven point is maximum. Therefore, by reducing the pivot angle in the range where the driving force is large,
The direction of the driving force is brought closer to the direction along the axis of the nut member to reduce its radial component, while in the range where the driving force is small, the driving force itself increases even if the radial component of the driving force increases. By utilizing the reduction, the total moment force received by the nut member can be reduced as a result.

According to the linear actuator of the second aspect of the present invention, the screw shaft member that moves forward and backward according to the rotation of the electric motor and the driven point of the driven member are connected by the link member that is pivotable. Therefore, even when the driven point moves in a curved line, the link member pivots so that the screw shaft member has the driven point and the pivot point of the link member. Since the driving force is applied only along the extending direction of the connected line, the moment force received by the screw shaft member can be suppressed low. However, if the angle formed by the line connecting the driven point and the pivot point of the link member and the axis of the screw shaft member (referred to as the pivot angle) becomes large, the screw shaft member in the driving force will have a large angle. The radial component with respect to the axis increases, and as a result, the moment force received by the screw shaft member may increase. Therefore, within the movable range of the screw shaft member, the pivot angle of the link member with respect to the axis of the screw shaft member is 10 at a position where the driving force applied from the link member to the driven point is maximum. Within a range of a large driving force, by making the pivot angle small,
The direction of the driving force is brought closer to the direction along the axis of the screw shaft to reduce its radial component, while in the range where the driving force is small, the driving force itself increases even if the radial component of the driving force increases. By utilizing the reduction, the total moment force received by the screw shaft member can be reduced as a result.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a front view of the linear actuator according to the first embodiment, and FIG.
The nut member is shown in the most retracted state, as shown in FIG.
Shows the state where the nut member is most pushed out.

In FIG. 1, an output shaft (not shown) of an electric motor 11 mounted on a housing 10 is a reducer of a reducer (not shown) (for example, a double-row planetary gear reducer) housed in the housing 10. It is connected to the input shaft. The speed reducer decelerates the rotational force of the electric motor 11, and outputs the speed from the speed reducer output shaft 12 to the outside in that state.

A male serration portion 12a is formed on the outer circumference of the reduction gear output shaft 12, and a female serration portion 12a is formed at the end portion (right end in FIG. 1) of the screw shaft 13 extending coaxially with the reduction gear output shaft 12. Serrations 13a are formed, and both serration parts 12 are formed.
By engaging a and 13a, the speed reducer output shaft 1
2 and the screw shaft 13 are connected so as to rotate integrally.

In FIG. 1, the cylindrical portion 1 is provided on the outer periphery of the right end of the screw shaft 13.
3b is formed and is rotatably supported by the bearing 14 with respect to the housing 10. Retaining ring 15 is cylindrical portion 1
The bearing 14 is attached to the bearing 3 in order to position the bearing 14 in the axial direction.

A screw groove 13c (only a part of which is shown) is formed on the outer peripheral surface of the screw shaft 13 excluding the cylindrical portion 13b.
A thread groove 16a (only part of which is shown) is formed on the inner peripheral surface of the nut 16 so as to face the thread groove 13c.
A large number of balls 17 are rotatably arranged in the spiral space formed by 16a. In addition, nut 1
A tube 16b for returning the ball 17 from one end of the nut 16 to the other end is provided on the outer periphery of the nut 6. Nut 16
The screw shaft 13 and the balls 17 form a ball screw mechanism BS.

The nut 16 has a cylindrical portion 16c at the left end in FIG.
And the cylindrical portion 16c has a circumferential groove 16d. A bracket 18 is attached so as to sandwich the cylindrical portion 16c. The right end claw portion 18a of the bracket 18 in FIG. 1 engages the circumferential groove 16d by caulking, so that the bracket 18 and the nut 16 are integrated. A circular hole 18b is formed near the left end of the bracket 18 in FIG.
Are formed. The nut 16 and the bracket 18 form a nut member.

The link member 19 has an elongated hole (may be two circular holes) 19a, and is pivotally attached to the bracket 18 by a pin 20 inserted into the elongated hole 19a and the circular hole 18b. Has been. The pivot point is the center of the pin 20. The link member 19 is pivotally attached to the lever member 21 by a pin 22 inserted into the elongated hole 19a and the circular hole 21a of the lever member 21. The center of the pin 22 is the driven point. The lever member 21, which is a driven member, is pivotable around the point P, that is, the driven point moves in an arc. In the present embodiment, the spring S is used as an example of the driven object, but this may be, for example, the caliper drive unit of the parking brake device.

Next, the operation of this embodiment will be described. If the driver performs an operation for operating the parking brake device from the state shown in FIG. 1B,
Electric power is supplied to the electric motor 11 from a power source (not shown), an output shaft (not shown) rotates, and the rotational force is output to the reducer output shaft 12 via a reducer (not shown). The screw shaft 13 rotates together with the speed reducer output shaft 12, but the nut 16
Since the lever member 21 is held in the rotationally non-driving state by the link member 19 and the bracket 18, the rotational displacement of the screw shaft 13 is converted into the axial displacement of the nut 16. At this time, the ball 17 allows such conversion to be performed with low friction.

When the nut 16 moves to the right in FIG. 1 (also referred to as displacement), the bracket 18 and the link member 1
A driving force is applied to the driven point of the lever member 21 via 9, the lever member 21 rotates to the state shown in FIG. 1A, and the operation of closing the caliper of the parking brake device is performed, for example. It will be. When the driver performs a releasing operation to release the parking brake device, the electric motor 11 rotates in the reverse direction, the nut 16 moves to the left in the same manner, and the lever member 21 is moved via the bracket 18 and the link member 19. , The state shown in FIG. 1B is turned, and the operation of opening the caliper of the parking brake device is performed.

According to the linear actuator of the present embodiment, the bracket 18 that moves forward and backward in response to the rotation of the electric motor 11 and the driven point of the lever member 21 are connected by the pivotable link member 19. Therefore, even when the driven point moves along a curved line (here, an arc), the link member 19 pivotally connects the driven point and the pivot point of the link member 19 to the bracket 18. Since the driving force F is applied only along the direction in which the line extends, the moment force received by the bracket 18 can be suppressed low. However, if the angle θ (referred to as a pivot angle) formed by the line connecting the driven point and the pivot point of the link member and the axis of the nut 16 increases, the nut 16 at the driving force F increases.
The radial component with respect to the axis line becomes larger, and as a result, the moment force received by the bracket 18 may increase. Therefore, within the movable range of the nut 16 and the bracket 18, at a position where the driving force F applied from the link member 19 to the driven point is maximum (state shown in FIG. 1A), the nut 16 and the axis of the nut 16 are By setting the pivot angle of the link member 19 within 10 degrees (more preferably within 5 degrees, most preferably 0 degree), the pivot angle θ is reduced when the driving force F is large, Driving force F
The direction of is set to be the direction along the axis of the nut 16, and its radial component can be reduced. On the other hand, as shown in FIG. 1B, when the driving force F is small, the radial component of the driving force F increases but the driving force F increases.
Since the size of the bracket 18 itself becomes small, as a result, the moment force received by the bracket 18 can be reduced in total.

FIG. 2 shows the amount of displacement of the nut 16 and the driving force F.
FIG. 6 is a diagram showing a relationship with a moment force M received by the bracket 18; When the horizontal axis is 0, the state is shown in FIG. 1B, and when the horizontal axis is 1, the state is shown in FIG. As is clear from FIG. 2, the driving force F is
Although it increases linearly according to the displacement amount of, the moment force M becomes zero in both the state shown in FIG. 1 (a) and the state shown in FIG. 1 (b), thus reducing the bending moment force received by the nut 16. be able to.

FIG. 3 is a front view of the linear actuator according to the second embodiment, and FIG. 3 (a) shows a state in which the nut member is retracted by half of one stroke.
FIG.3 (b) shows the state where the nut member was pushed out most.

In FIG. 3, the nut 1 is attached to the output shaft 112 of the electric motor 111 attached to the housing 110.
16 is attached and is designed to rotate integrally. A screw shaft 113 is arranged inside the nut 116 so as to penetrate therethrough. A cylindrical portion 116c of the nut 116 arranged on the left end side in FIG. 3 is rotatably supported by the bearing 114 with respect to the housing 110.

On the right half outer peripheral surface of the screw shaft 113 in FIG.
A thread groove 113c (only a part of which is shown) is formed, while a thread groove 116a (only a part of which is shown) is formed on the inner peripheral surface of the nut 116 so as to face the thread groove 113c.
In the spiral space formed by 3c and 116a,
A large number of balls 117 are rotatably arranged. Further, a ball 117 is attached to the outer periphery of the nut 116.
A tube 116b for returning from one end of 16 to the other end is provided. The nut 116, the screw shaft 113, and the ball 1
A ball screw mechanism BS is constructed with 17.

The screw shaft 113 has a round shaft 11 in the left half in FIG.
3a, and has a peripheral groove 113b near the end. The outer peripheral surface of the round shaft 113a is sealed in the inner hole 110a of the housing 110 via a seal 115.

A bracket 118 is attached so as to hold the left end side of the screw shaft 113 in FIG. The bracket 118a at the right end in FIG. 3 of the bracket 118 is engaged with the circumferential groove 113b by caulking, so that the bracket 118
And the nut 116 are integrated. Bracket 11
8, a circular hole 118b is formed near the left end in FIG. The screw shaft 113 and the bracket 118 form a screw shaft member.

The link member 119 has an elongated hole (may be two circular holes) 119a. The elongated hole 119a and the circular hole 1
18b and the pin 120 inserted into the bracket 1
It is pivotally attached to 18. The pivot point is the center of the pin 120. Also, the link member 119
Is the long hole 119a and the circular hole 121a of the lever member 121.
It is pivotally attached to the lever member 121 by a pin 122 inserted in and. The center of the pin 122 is the driven point. The L-shaped lever member 121, which is a driven member, is pivotable around the point P, that is, the driven point moves in an arc. In the present embodiment, the triangular spring S is used as an example of the driven object.

Next, the operation of this embodiment will be described. From the state shown in FIG. 3B, when the electric power is supplied to the electric motor 111 from the power source (not shown) and the output shaft 112 rotates, the nut 116 rotates integrally, but the screw shaft 113
Is held in a rotationally non-driving state by the link member 119 and the bracket 118 with respect to the lever member 121, the rotational displacement of the nut 116 is converted into the axial displacement of the screw shaft 113. At this time, the ball 11
According to No. 7, such conversion is performed with low friction.

When the screw shaft 113 moves to the right in FIG. 3 up to 1/2 of one stroke (movable range), the driving force is applied to the driven point of the lever member 121 via the bracket 118 and the link member 119. Is given to the lever member 12
1 rotates to the state shown in FIG. 3A, but at this time, the drive portion 121b of the lever member 121 rides on the apex of the triangular spring S and deforms it. That is, FIG. 3 (a)
The state shown in FIG.
Is the position. After that, when the screw shaft 113 moves to the right in FIG. 3, the drive portion 121b of the lever member 121 passes over the apex of the triangular spring S, and the deformation returns.

According to the linear actuator of the present embodiment, the bracket 118 that moves forward and backward according to the rotation of the electric motor 111 and the driven point of the lever member 121 are connected by the pivotable link member 119. Therefore, even if the driven point moves along a curved line (here, an arc), the link member 119 pivots to move the bracket 1
Since the driving force F is applied to 18 only along the direction in which the line connecting the driven point and the pivot point of the link member 119 extends, the moment force received by the bracket 118 can be kept low. it can. However, if the angle θ (referred to as a pivot angle) formed by the line connecting the driven point and the pivot point of the link member and the axis of the screw shaft 113 becomes large, the axis of the screw shaft 113 with respect to the driving force F is increased. The radial component increases, and as a result, the moment force received by the bracket 118 may increase. Therefore, the screw shaft 113
In the range in which the bracket 118 can move, the screw shaft 113 is at a position where the driving force F applied from the link member 119 to the driven point is maximum (state shown in FIG. 3A).
The pivot angle of the link member 119 with respect to the axis of 10 is within 10 degrees (more preferably within 5 degrees, most preferably 0 degrees).
Therefore, when the driving force F is large, the pivot angle θ is reduced so that the direction of the driving force F can be changed.
The direction along the axis of 16 can be used to reduce the radial component. On the other hand, FIG.
As shown in (b) (or the state where the screw shaft 113 is most retracted), when the driving force F is small, the radial component of the driving force F increases, but the driving force F itself decreases. Therefore, as a result, the moment force received by the bracket 118 can be reduced in total.

FIG. 4 is a diagram showing the relationship between the amount of displacement of the screw shaft 113 and the driving force F and the moment force M received by the bracket 118. When the horizontal axis is 0, the state is shown in FIG. 3B, and when the horizontal axis is 1/2, the state is shown in FIG. As is clear from FIG. 4, the driving force F linearly increases from 0 to 1/2 of the displacement of the screw shaft 113,
When it is 1/2, it becomes maximum and the displacement amount linearly decreases from 1/2 to 1, but the moment force M is as shown in FIG.
In both the state shown in FIG. 3 and the state shown in FIG. 3B, the bending moment force received by the screw shaft 113 can be reduced. The driving force actually generated in the linear actuator rarely changes linearly as shown in FIGS. 1 and 3, but it often changes in accordance with the stroke, so if it is known that the driving force becomes maximum. ,
As shown in FIGS. 1A and 3A, the nut member or the screw shaft member and the driven member may be positioned.

Although the present invention has been described above with reference to the exemplary embodiments, the present invention should not be construed as being limited to the above-described exemplary embodiments, but it goes without saying that appropriate modifications and improvements are possible. is there.

[0033]

According to the linear actuator of the first aspect of the present invention, the nut member that moves forward and backward according to the rotation of the electric motor and the link member that can pivot the driven point of the driven member are used. Since they are connected, even when the driven point moves in a curved line, the link member pivots, so that the nut member has the driven point and the pivot point of the link member. Since the driving force is applied only along the extending direction of the joined line, the moment force received by the nut member can be suppressed low. However, if the angle formed by the line connecting the driven point and the pivot point of the link member and the axis of the nut member (referred to as the pivot angle) increases, the axis of the nut member with respect to the driving force is increased. The radial component increases, and as a result, the moment force received by the nut member may increase. Therefore, within the movable range of the nut member, the pivot angle of the link member with respect to the axis of the nut member is 10 degrees or less at a position where the driving force applied from the link member to the driven point is maximum. Therefore, by reducing the pivot angle in the range where the driving force is large,
The direction of the driving force is brought closer to the direction along the axis of the nut member to reduce its radial component, while in the range where the driving force is small, the driving force itself increases even if the radial component of the driving force increases. By utilizing the reduction, the total moment force received by the nut member can be reduced as a result.

According to the linear actuator of the second aspect of the present invention, the screw shaft member that moves forward and backward according to the rotation of the electric motor and the driven point of the driven member are connected by the link member that is pivotable. Therefore, even when the driven point moves in a curved line, the link member pivots so that the screw shaft member has the driven point and the pivot point of the link member. Since the driving force is applied only along the extending direction of the connected line, the moment force received by the screw shaft member can be suppressed low. However, if the angle formed by the line connecting the driven point and the pivot point of the link member and the axis of the screw shaft member (referred to as the pivot angle) becomes large, the screw shaft member in the driving force will have a large angle. The radial component with respect to the axis increases, and as a result, the moment force received by the screw shaft member may increase. Therefore, within the movable range of the screw shaft member, the pivot angle of the link member with respect to the axis of the screw shaft member is 10 at a position where the driving force applied from the link member to the driven point is maximum. Within a range of a large driving force, by making the pivot angle small,
The direction of the driving force is brought closer to the direction along the axis of the screw shaft to reduce its radial component, while in the range where the driving force is small, the driving force itself increases even if the radial component of the driving force increases. By utilizing the reduction, the total moment force received by the screw shaft member can be reduced as a result.

[Brief description of drawings]

FIG. 1 is a front view of a linear actuator according to a first embodiment.

FIG. 2 is a diagram showing a relationship between a displacement amount of a nut 16 and a driving force F and a moment force M received by a bracket 18.

FIG. 3 is a front view of a linear actuator according to a second embodiment.

FIG. 4 is a diagram showing a relationship between a displacement amount of a screw shaft 113 and a driving force F and a moment force M received by a bracket 118.

[Explanation of symbols]

11,111 Electric motor 13,113 screw shaft 16,116 nuts 17,117 balls 18,118 bracket 19,119 Link member 21,121 Lever member

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3J062 AA02 AA27 AB22 AB27 AC07                       AC08 AC09 BA14 BA16 CB02                       CB15 CB18 CB23 CB27 CB32                       CB45                 5H607 AA00 BB01 BB14 CC03 DD19                       EE52

Claims (2)

[Claims] 1. A linear actuator for driving a driven member in which a driven point draws a curve, comprising: an electric motor, a screw shaft connected to an output shaft of the electric motor, and a nut arranged around the screw shaft. A member, a ball rolling in a spiral groove formed between the screw shaft and the nut member, a pivotable link member connecting the nut member and a driven point of the driven member And, in a range in which the nut member is movable, at a position where the driving force applied from the link member to the driven point is maximum, the pivot angle of the link member with respect to the axis of the nut member. Is a linear actuator characterized by being within 10 degrees. 2. A linear actuator for driving a driven member whose driven point draws a curve, comprising: an electric motor, a nut coupled to an output shaft of the electric motor, and a screw shaft member arranged in the nut. A ball that rolls in a spiral groove formed between the screw shaft member and the nut; and a pivotable link member that connects the screw shaft member and a driven point of the driven member. And a pivotal movement of the link member with respect to the axis of the screw shaft member at a position where the driving force applied from the link member to the driven point is maximum within a range in which the screw shaft member is movable. A linear actuator characterized in that the angle is within 10 degrees.