JPH02225856A - Linear actuator - Google Patents

Abstract

PURPOSE:To enable mass production at a low price and the high accuracy less than micron by forming a rod member, which one end elastically abuts to a cam plate side surface, to perform a linear motion with the other end thereof in the axial direction with the rotation of the cam plate formed with an involute curve. CONSTITUTION:A rod member 6 which shaft core 12 coincides with a contact line 13 of one point on a circumference in a base 10 is supported so that one end thereof always and elastically abuts to profile on a normal of an involute curve forming a cam plate in a side surface of a cam plate 5. Some parallel supporting springs 14 such as springs in spiral or spider-feet-shape are located in the predetermined places of the rod member 6 to support the rod member 6 reciprocatably. Further, a member having a small friction coefficient such as a ball 15 is fitted to the cam plate 5 abutting part of the rod member 6. The cam plate 5 is formed with a certain involute curve 11 like this, and the rod member 6 is supported by the cam plate 5 reciprocatably in a certain relation. Consequently, the predetermined effect that a moving length of the rod member 6 abutting to the cam plate 5 is in proportion to a rotary angle of the cam plate 5 is displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a linear actuator that obtains linear motion from the rotational motion of a rotational drive means such as a motor.

2. Description of the Related Art Linear actuators, which obtain linear motion from the rotational motion of rotational drive means such as motors, are widely used in automatic machine tools and the like. In conventional linear actuators, a reduction gear is provided on the output shaft of the motor, and a screw/nut mechanism or a ball/screw mechanism is provided on the output shaft of the reduction gear so that the rod member moves linearly. There is.

Problems to be Solved by the Invention In the above-mentioned conventional linear actuator, when precision of microns or less is required, the threaded portion is required to have high precision. Due to the precision of the processing of this screw mechanism,
The entire device is extremely expensive, and it is difficult to process, so mass production is not possible.

Accordingly, an object of the present invention is to provide a linear actuator that does not require a screw mechanism, can be manufactured at low cost, and has high accuracy of less than microns.

Means for Solving the Problems In order to achieve the object, the present invention provides a linear system that obtains linear motion from the rotational motion of a rotational drive means such as a motor.
The actuator is composed of a cam plate of a fixed shape rotated by a shaft connected to an output shaft of a rotational drive means, and a rod member arranged to be in constant contact with the cam plate and reciprocated in the axial direction. The cam plate is formed by an involute curve obtained from a base circle with a constant radius, and the rod member has an axis that coincides with a tangent to a point on the circumference of the base circle, and one end of which is connected to the cam. Provided is a linear actuator characterized in that the actuator is supported so as to resiliently abut and follow the side surface of a plate, and the other end of the rod member moves linearly in the axial direction of the rod member by rotation of the cam plate. .

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. In FIGS. 1 and 2, the linear actuator l according to the present invention includes a motor 2 as a rotational drive source, a reducer 3 connected to its output shaft, and a shaft 4 of the reducer 3. A cam plate 5, which is an important component of the present invention, is connected and rotated by a speed reducer 3. In the present invention, the cam plate 5 is provided with a rod member 6 which is disposed in constant contact with the rod member 6 and is reciprocated in the axial direction. Incidentally, it is preferable that the motor 2 is provided with a feedback control circuit 7 including a position sensor, so that the precise position can also be controlled electronically.

In the present invention, the cam plate 5 is formed into a certain shape.

Further, the rod member 6 has a side surface 8 which becomes the cam surface of the cam plate 5.
The cam plate 5 is supported so as to elastically abut against and follow the cam plate 5, and is caused to reciprocate or move linearly in the axial direction by the rotation of the cam plate 5. In particular, as shown in detail in FIG. 5, the cam plate 5 has an involute curve 11 obtained from a base circle 10 of a constant radius.
formed by. Moreover, the rod member 6 has its axis 12
coincides with a tangent line 13 at a point on the circumference of the base circle 9, and one end thereof always elastically abuts and follows the normal line of the involute curve forming the cam plate 5 on the side surface of the cam plate 5. is supported by Therefore, the rod member 6 is provided with a spiral spring as shown in FIGS. 3 and 4 (FIG. 3).
It is preferable that several parallel support springs 14, such as springs or spider-like springs (see FIG. 4), be arranged at predetermined locations (see FIG. 1) to support the bar member 6 in a reciprocating manner. Furthermore, as shown in FIGS. 1 and 2, it is preferable to attach a member having a low coefficient of friction, such as a ball 15, to the portion of the rod member 6 that comes into contact with the cam plate 5.

As mentioned above, the cam plate 5 has a constant involute curve 1
1, and a rod member 6 is also supported by the cam plate 5 formed of this involute curve so as to be able to reciprocate in a fixed relationship. As a result, the predetermined effect that the moving length of the rod member 6 in contact with the cam plate 5 is proportional to the rotation angle of the cam plate 5 is achieved. This point will be explained with reference to FIG.

In Fig. 5, the radius of the base circle 10 forming the involute curve 11 is r, the rotation center is ○, the starting point of the involute curve 11 is A, and point B is rotated by an angle θ (radian) from the point to the point. Let it be a point on the circumference of the base circle 10 at the time. The tangent at this point B is the tangent 13 described above, and if the intersection of this tangent and the impolicoat curve 11 is C, then the tip (ball 15) of the rod member 6 will be in contact with this point C. In this state, it will be proven that the length of linear movement of the rod member 6 in contact with the cam plate 5 is proportional to the rotation angle of the cam plate 5.

First, line segment BC = circular arc AB = rXθ, and since the radius `` is constant, it can be seen that line segment BC is proportional to the rotation angle θ (radians).

Next, the angle CBO is always a right angle (π/2), and at this point C, the rod member 6 has its axis 12 coincident with the tangent 13 of a point B on the circumference of the base circle 9, and its tip Since the rod member 6 is supported so as to always elastically abut and follow the normal line of the involute curve 10, the axis 12 of the rod member 6 is on the extension line of the line segment BC, and as a result, the rod member 6 As a whole, it can be seen that the movement length of the line segment BC is proportional to the rotation angle θ.

In addition, in a linear actuator, the rod member 6 moves back and forth, and most commonly, the effective angle of θ is set to 0 to π radians (180 degrees), and the rod member 6 is moved back and forth within the rotation angle range of π to 2π. be. But apart from this, the angle is 0 to π
The rod member 6 can be reciprocated by performing normal rotation and reverse rotation in the range of radians, and can also be reciprocated with the moving length of the rod member 6 being changed in the range of rotation angles π to 2π. That is, a second base circle I6 with a short radius is set outside the base circle 10 as shown by the broken line of the 5th rgJ, and another involute curve 17 (broken line) is set at the rotation angle π to 2π of the cam plate 5. It is formed in a portion corresponding to the range of .pi. to 2.pi. and reciprocates by performing normal rotation and reverse rotation within this angle range of .pi. to 2.pi. According to this, when the rotation angle is used at O to π radians, the amount of movement becomes long, and when the rotation angle is used at π to 2π radians, the moving length of the rod member 6 can be shortened.

The shape of the cam plate 5 shown in FIG.
Involute curves 10 and 17 formed by 6
Please understand that this is based on the following.

Further, the maximum moving length of the rod member 6 is determined by the radius of the base circle. This is because the line segment BC determines the moving length of the rod member, and the line segment BC is the product of the radius r and the rotation angle θ, so if θ is 0 to π radians, the maximum length of the line segment BC is This is because the length is rxπ. In other words, if the maximum movement length is determined, the radius r of the base circle can be determined. The actual design would involve determining the maximum travel length and determining the radius of the base circle.

Effects of the Invention According to the linear actuator of the present invention, a cam plate of a fixed shape is rotated by a shaft connected to an output shaft of a rotary drive means, and a cam plate is arranged so as to be in constant contact with the cam plate and reciprocates in the axial direction. It consists of a rod member that can be moved,
The cam plate is formed by an involute curve obtained from a base circle of a constant radius, and the axis of the rod member coincides with a tangent to a point on the circumference of the base circle, and one end thereof is The rod member is supported so as to elastically abut and follow the side surface of the cam plate, and the other end of the rod member moves linearly in the axial direction of the rod member as the cam plate rotates, so no screw mechanism is required. It is not used, and its accuracy is determined by the accuracy of machining the cam plate, and machining with an involute curve is not so difficult, so high precision of microns or less can be achieved.

According to the linear actuator of the present invention, the rod member can be moved by a length proportional to the rotation of the cam plate and, in turn, the shaft. is directly proportional, and its control is not only extremely simple, but also much more accurate.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a linear actuator according to the present invention, FIG. 2 is a front view of a linear actuator according to the present invention, and FIGS. 3 and 4 are for linearly moving a rod member. FIG. 5 is a front view showing an example of a parallel spring, and FIG. 5 is an explanatory diagram showing the relationship between the movement of the cam plate and the rod member of the linear actuator according to the present invention. Explanation of symbols 1... Linear actuator 2... Motor 3... Reduction gear 4... Shaft 5... Cam plate 6... Rod member 7... Control Circuit 10... Base circle 11... Involute curve 12... Axis core 13... Tangent line 14... Parallel spring I5... Ball

Claims (1)

[Claims] A linear actuator that obtains linear motion from the rotational motion of a rotational drive means such as a motor includes a cam plate of a certain shape that is rotated by a shaft connected to the output shaft of the rotational drive means, and a cam plate arranged so as to be in constant contact with the cam plate. The cam plate is formed by an involute curve obtained from a base circle with a constant radius, and the axis of the rod member is located at the circumference of the base circle. It corresponds to a tangent line at one point on the top, and one end is supported so as to elastically contact and follow the side surface of the cam plate, and as the cam plate rotates, the other end of the bar member becomes straight in the axial direction of the bar member. A linear actuator characterized by movement.