RU2700562C1 - Linear actuator and linear actuating mechanism - Google Patents

Abstract

FIELD: machine building.SUBSTANCE: linear actuator comprises engine with output shaft and housing accommodating screw mechanism and ball mechanism to compensate for undesirable load. Screw mechanism includes a lead screw, a nut interacting with it and a retractable rod concentrically located around at least part of the lead screw and connected to the specified nut. Screw mechanism is connected to the motor so that rotation of its output shaft causes axial movement of the nut and sliding rod relative to the housing. In the linear actuating mechanism rotation of the lead screw causes axial movement of the nut and the sliding rod relative to the body. Ball-type mechanism for compensation of undesirable load is formed by at least two longitudinal guide grooves on inner surface of housing, at least, two response longitudinal guide grooves on outer surface of sliding rod and ball separator with, at least, two rows of cells arranged opposite said guide grooves. Balls rolling the surfaces of said guide grooves are arranged in cells with possibility of free rotation.EFFECT: higher reliability of devices.4 cl, 15 dwg

Description

The invention relates to general mechanical engineering, namely, to gears for communicating reciprocating motion using a screw mechanism.

The prior art designs of linear actuators with helical gears that convert the rotation of the motor shaft into linear motion and are used as devices for linear movement or positioning of an object due to the axial force of pushing / pulling the retractable rod.

A typical retractable linear actuator comprises an electric motor whose shaft is connected to a helical gear that converts rotational motion into linear movement of the stem and consists of a spindle and a drive nut held in rotation so that rotation of the spindle by the motor causes the drive nut to move linearly along the spindle screw. The drive nut is connected to the extension rod, and rotation of the lead screw linearly moves the extension rod along the axis of the screw in the forward and reverse directions, depending on the direction of rotation of the motor shaft.

The actuator motor can be located parallel, perpendicular or coaxial (in one line) with respect to the axis of stem extension, which is determined by the design and type of connection of the motor shaft and the screw (coupling connection, gear, worm, belt drive, etc.).

The linear actuator housing, usually made in the form of a hollow cylinder or a profile pipe, accommodates a helical gear and a rod extended along its longitudinal axis and made in the form of a hollow cylinder, inside of which there is a lead screw.

A coupling, head or plug is mounted on the free end of the slide rod to connect to an object to be actuated.

The force of the rod of the linear actuator is directed along the axis of its extension / retraction, and in most designs of linear actuators the direction of action of the load on the rod should coincide with the axis of the rod, which is usually achieved by using external guides to align, stabilize and support the actuated object. The load, the direction of which deviates from the specified axis, exposes the actuator mechanisms to the effects of the moments created by it and is undesirable. Particularly undesirable loads are the cantilever load, which generates torque about the axis of extension of the rod, and the radial (lateral) load, which creates bending moment. Exceeding the permissible values of unwanted loads can impede the operation of the linear actuator mechanisms and disable them.

These restrictions hinder the use of linear actuators in various operations with unsecured unsupported objects, objects with an insufficiently fixed installation, objects exposed to external loads and other objects that create undesirable loads, in particular cantilever and radial loads, or a combination of these loads on the actuator rod.

The prior art design of a linear actuator with a side load compensation mechanism located inside the casing and containing at least one rail attached to the casing along the axis of the screw (stem extension), pre-loaded to a known side load for at least , on one roller attached to the drive nut of the linear actuator (see patent US6145395, class F16H25 / 20, publ. 14.11.2000). In the preferred embodiment disclosed in the patent description, the side load compensation mechanism comprises two pairs of rails located on both sides of the extension rod along the axis of the screw, and the drive nut is provided with several pairs of rollers mounted by shafts along the axial movement direction of the drive nut in such a way that each roller is located between one of the pairs of rails. Additionally, a sleeve (or plain bearing) is installed between the sliding rod and the housing, which sums the load at the end of the actuator and compensates for the load provided by the preloaded rails.

A disadvantage of the described actuator design with a side load compensation mechanism is the dependence of the side load compensation efficiency on its direction of action. The claimed work of the side load compensation mechanism is performed with maximum efficiency when the side load is directed perpendicular to the axes of the roller shafts. As the direction of action of the lateral load changes, the operation of the mechanism changes. A load whose direction of action parallel to the axes of the roller shafts is absorbed only by a part of the mechanism - the sleeve (or sliding bearing), in which in this case there will be jamming and increased wear.

A linear actuator is also known from the technical field, comprising a motor with an output shaft and a housing, inside of which there is a screw mechanism and a ball mechanism for compensating for unwanted loads, the screw mechanism including a lead screw, a nut interacting with it and a retractable rod concentrically located around at least parts of the lead screw and connected to the specified nut, while the screw mechanism is connected to the engine so that the rotation of its output shaft causes axial movement of Menus and retractable rod relative to the housing (see. Patent No. CN105051424, kl.F16H25 / 24, publ. 06.04.2018).

In the above technical solution, a ball sleeve is used as a ball mechanism to compensate for unwanted loads.

The used ball sleeve as a ball mechanism for compensating for unwanted load does not ensure the reliability of the linear actuator and, in addition, leads to an increase in the dimensions and weight of the linear actuator as a whole.

The technical problem is the creation of a linear actuator and a linear actuator, the design of which provides the ability to compensate for unwanted loads, the direction of which does not coincide with the axis of the actuator rod.

The technical result consists in simplifying the design of a linear actuator, increasing the reliability of the device, reducing the size and weight.

In the part of the linear actuator, the problem posed is solved, and the technical result is achieved by developing a linear actuator, characterized by the presence of an engine with an output shaft and a housing, inside of which there is a screw mechanism and a ball mechanism for compensating for undesirable loads, and the screw mechanism includes a lead screw interacting with a nut and a retractable rod concentrically arranged around at least a portion of the lead screw and connected to the specified nut, while the screw mechanism the ism is connected to the engine in such a way that the rotation of its output shaft causes axial movement of the nut and the sliding rod relative to the housing, the ball mechanism for compensating for undesirable load is formed by at least two longitudinal guide grooves on the inner surface of the housing, at least two reciprocal longitudinal guides grooves on the outer surface of the sliding rod and a ball cage with at least two rows of cells made opposite these guide grooves, in With the possibility of free rotation there are balls rolling around the surfaces of these guide grooves. The ball compensation mechanism for the unwanted load is preferably provided with at least one spring, which prevents the ball cage from slipping under its own weight when the linear actuator is inclined.

In the part of the actuator, the problem is solved, and the technical result is achieved by the fact that the linear actuator contains a housing, inside which there is a screw mechanism and a ball mechanism for compensating for undesirable loads, and the screw mechanism includes a lead screw, a nut interacting with it and a retractable rod, located concentrically around at least a part of the screw and connected to the specified nut, while the rotation of the screw leads to axial movement of ha ki and extendable rod relative to the housing, the ball mechanism for compensating for unwanted loads is formed by at least two longitudinal guide grooves on the inner surface of the housing, at least two reciprocal longitudinal guide grooves on the outer surface of the extendable rod and a ball cage with at least two rows of cells made opposite these guide grooves, in which balls are rotatably placed that run around the surfaces of these guides grooves. The ball compensation mechanism for the unwanted load is preferably provided with at least one spring, which prevents the ball cage from slipping under its own weight when the linear actuator is inclined.

Next, one of the many possible embodiments of the invention will be described in more detail with reference to the accompanying drawings, in which:

figure 1 shows a perspective view of a linear actuator in accordance with the present invention;

figure 2 - axonometric view of the linear actuator of figure 1 in a partially disassembled form;

figure 3 is a perspective view of a linear actuator with a cutout in the housing and with a cutout in a ball cage located inside the housing;

figure 4 is a cross-sectional view along the line aa in figure 3;

figure 5 is a view in longitudinal section of a linear actuator shown in figure 3 and made along the line BB in figure 4;

figure 6 is a view in longitudinal section of a linear actuator shown in figure 3 and made along the line CC in figure 4;

Fig.7 is an exploded perspective view of a linear actuator;

on Fig is a perspective view of a screw mechanism removed from the housing;

figure 9 is an axonometric view of the screw mechanism in disassembled form with a cutout in the retractable rod;

figure 10 is a perspective view of the connection of a ball nut with a sliding rod;

figure 11 is an axonometric view of the lead screw with limiter disassembled;

on Fig - schematic representation of a linear actuator with a sliding rod in two extreme positions;

13 is a schematic illustration of a linear actuator in an inclined position when the front end portion of the extension rod is higher than the rear end portion;

on Fig - schematic representation of a linear actuator in an inclined position when the front end part of the extension rod is below the rear end part;

on Fig is a schematic axonometric view of the installation of the springs supporting the separator with balls.

Figure 1-2 shows the proposed linear actuator comprising an electric motor 16, a coupling 15 with a clutch housing 14 and a linear actuator 10 comprising a housing 11 having a rear end portion close to the electric motor and an opposite front end portion remote from it located in it a screw mechanism and a mechanism for compensating for unwanted loads.

The electric motor 16, being a source of rotational power, transmits torque to the screw mechanism, for which the output shaft of the electric motor 16 is connected via a clutch 15 to the end portion 22a of the lead screw 22.

The connection of the motor shaft with the screw mechanism of the linear actuator can be performed by any mechanical means of transmitting rotational motion (flexible or rigid coupling, belt drive, gear transmission, worm gear, etc.), including with reduction and with various mutual configurations of arrangement electric motor and linear actuator (in particular, the direct nozzle of the working body of the driven mechanism on the shaft).

The housing 11 is made in the form of a profile pipe with longitudinal ball guide grooves on the inner surface of a circular cross-section.

The longitudinal ball guide groove (hereinafter referred to as the "guide groove") is an element of the ball mechanism for compensating for unwanted load (hereinafter referred to as the "compensation mechanism")

As shown in FIGS. 3-6, the screw mechanism located inside the housing 11 comprises a nut 23 cooperating with a lead screw 22 and a retractable rod 21 connected to the nut 23 for axial movement with it.

In the described embodiment of the present invention, as best seen in FIG. 4, four guide grooves 31 are made on the inner surface of the housing 11, and four counter guide grooves 32 are made on the outer surface of the slide rod 21. The guide grooves 31 and 32 are spaced at equal intervals along the circumference of the transverse sections of the inner surface of the housing 11 and the outer surface of the slide rod 21, respectively. The guide grooves 31 and 32 are concave in cross section and face each other in each pair.

Retractable rod 21 is made in the form of a profile pipe, the outer contour of the cross section of which contains the guide grooves 32, and the inner contour repeats the outlines of the outer contour.

The dimensions of the outer contour of the cross section of the nut 23 are made under the inner contour of the cross section of the extension rod 21 and, as can be seen in Figs. 7-8, the nut 23 covering the spindle 22 is connected to the extension rod 21 through mating surfaces with screws 28 attached to the rear end part.

A connecting element (not shown) is mounted at the front end portion of the slide rod 21 to connect to an object to be actuated.

The ends of the end parts of the housing 11 are closed by covers 12 and 13. In the rear cover 12 of the housing 11, a bearing 17 is mounted with the outer ring fastened by an internal nut 19.

The lead screw 22 is mounted in the bearing 17 with the rear end portion 22a with the inner ring fastened with a slotted nut 18. The double row angular contact ball bearing 17 supports the lead screw 22 with the possibility of rotation, keeping it from axial displacement.

The front end portion 22b of the lead screw 22 has a smooth surface and is rotatably mounted with a lock washer 25 into the guide sleeve 24 (see FIGS. 5, 6, 9, 11).

The outer surface of the guide sleeve 24, similarly to the nut 23, is adjacent to the inner surface of the slide rod 21, but with a small clearance that does not prevent the axial movement of the slide rod 21 relative to the lead screw 22, maintaining alignment between the lead screw 22 and the slide rod 21 along a common longitudinal axis. The contact surfaces of the guide sleeve 24 comprise a sliding layer.

Thus, the screw 22 rotates inside the extension rod 21 when the latter together with the nut 23 moves along the longitudinal axis.

The guide sleeve 24 also acts as a limiter to the movement of the nut 23. To mitigate the impact of possible contact with the nut 23, a damping washer 26 is made on the side of the sleeve 24 facing the nut 23, made of an elastic material, such as rubber or the like.

For the same purpose, a damping washer 27 is installed between the back cover 12 and the nut 23.

In a screw mechanism, both a sliding helical gear and a rolling helical gear (ball screw or roller screw) can be used. Figure 10 shows the connection of a cylindrical ball nut 43 with an external thread with a sliding rod 41. For this, the rear end part of the sliding rod 41 is made with an internal thread, into which a nut 43 is screwed, followed by fixing with screws 44. The ball screw of the ball screw 42 is made with a treadmill for balls.

The compensation mechanism, in addition to the above four guide grooves 31, made on the inner surface of the housing 11 and the reciprocal guide grooves 32, made on the outer surface of the slide rod 21, contains a ball cage 33 with four rows of cells in which the balls 34 are located (one row for each pair mating guide grooves 31, 32).

A ball cage 33 with balls 34 is concentrically located between the inner surface of the housing 11 and the outer surface of the extension rod 21 so that each ball is between two guide grooves 31 and 32 and in contact with the concave surface of each of them. Balls 34 are placed in the separator 33 in such a way that each ball can rotate freely in the cell of the separator 33, so that when the sliding rod 21 is moved relative to the housing 11, the balls 34 roll along the guide grooves 31 and 32, entraining the separator 33. The required number of balls 34 is determined based on the load on the slide rod 21. The stroke of the separator 33 with balls 34 is limited by the cover 13 of the housing 11 on one side and the protruding heads of the screws 28 securing the nut 23 to the rear end of the slide rod 21 on the other hand (see Fig. 6, 7 and 8 )

The radius of curvature of the guide grooves 31 and 32 is close to the radius of the balls 34, which blocks the rotation of the sliding rod 21 relative to the housing 11, without interfering with its axial movement.

The proposed device works as follows.

The electric motor 16, connected with the possibility of changing the direction of rotation of the output shaft, when voltage is applied, rotates the spindle 22.

The nut 23 is kept from rotation (since it is connected to the sliding rod 21, the rotation of which is blocked relative to the housing 11) moves with the sliding rod 21 either in the direction of the end part of the housing 11 close to the electric motor or in the opposite direction, depending on the direction of rotation of the screw screw 22.

The rotation of the lead screw 22 and the linear movement of the extension rod 21 continues until the motor 16 is turned off. The limit positions of the extension rod 21 are controlled by limit switches (not shown).

Both during the movement of the extension rod 21 and during the stop, the compensation mechanism supports the extension rod 21 with many balls 34 of the separator 33 in the guide grooves 31 and 32 on the inner surface of the housing 11 and the outer surface of the extension rod 21, holding the extension rod 21 and the entire screw mechanism from displacement relative to the line of the longitudinal arrangement of the linear actuator nodes and blocking rotation around the longitudinal axis when an undesirable load is applied to the connecting element in the front end part of the extension zhnogo rod 21, thus not interfering with its axial movement when axial force.

In addition, as follows from the present description, in addition to its main function, the compensation mechanism performs the function of the counter-rotation mechanism provided for in most linear actuator designs, namely, it keeps the nut 23 from rotating relative to the housing 11 during rotation of the spindle 22.

In the process of extension / retraction of the extension rod 21, the balls 34 due to friction engagement with the surfaces of the guide grooves 31 and 32 roll, moving in the direction of movement of the extension rod 21. The linear distance of the movement of the balls 34 will be less than the linear distance traveled by the outer surface of the extension rod 21 relative to casing 11. As you know, when the ball rolls between a moving and a stationary plate, the speed of movement of the center of the ball is half the speed of movement of the moving plate. Thus, with respect to the fixed plate, the movable plate moves twice as much as the center of the ball rolling between them.

Thus, the separator 33 with the balls 34, moving simultaneously with the sliding rod 21 and in the same direction, passes a distance half as small for each time interval. On Fig shows a linear actuator 10 with a sliding rod 21 in two extreme positions, in the extreme retracted position (top), and in the extreme extended position (bottom), as well as the position of the separator 33 with balls 34 corresponding to the extreme positions of the sliding rod 21. As you can see, the retractable rod 21 extends from the extreme retracted position “catches up” the separator 33 with the rear end part and the distance S of the movement of the nut 23 with the retractable rod 21 corresponds to the linear distance C traveled by the rolling balls 34 and the separator m 33. When moving in the opposite direction, the sliding rod 21 retracts “running away” from the rear end of the separator 33. When the balls 34 roll without slipping, each intermediate position of the sliding rod 21 corresponds to the position of the separator 33, and in general, the operating range of the linear movement of the rod corresponds to the operating range linear displacement of the separator.

The lengths of the lead screw 22 and the separator 33 relative to the length of the housing 11 are designed so that in the extreme extended position of the rod 21, the separator 33 with balls 34 can be placed between the limiting nut 23 movement on the surface of the guide sleeve 24 and the cover 13.

The separator with balls is held in each position due to the frictional adhesion of the balls 34 with the surfaces of the guide grooves 31 and 32.

In many applications, the linear actuator has an inclined position, or changes the angle relative to the horizontal plane during the stem extension / retraction process, which, in positions close to vertical, can cause weakening of the contacting surfaces (balls 34 and guide grooves 31 and 32) the contact of the balls 34 with the surfaces of the guide grooves 31 and 32 (in particular, when an undesirable load is absent, or its action weakens or changes its direction), and therefore calling separator 33 with balls 34 under its own weight.

With this arrangement of the linear actuator, when the front end part of the extension rod 21 is higher than the rear end part, the separator 33 with balls 34 can slide in the direction of the rear end part of the extension rod 21 (see Fig. 13).

With this arrangement of the linear actuator, when the front end portion of the extension rod 21 is lower than the rear end portion, the cage 33 with balls 34 can slide in the direction of the front end portion of the extension rod 21 (see FIG. 14). The sliding direction of the separator 33 with the balls 34 is shown by the arrow.

To prevent the separator 33 from sliding with the balls 34 under its own weight when the linear actuator is inclined between the separator 33 and the elements restricting its linear movement, support compression springs 35 and 36 can be installed (see Fig. 15).

A spring 35 may be installed between the separator 33 and the screws 28 in the rear end portion of the extension rod 21 when using the linear actuator in an inclined position when the front end portion of the extension rod 21 is above the rear end portion. The spring 35 at one end abuts against the rear end of the separator 33, and the other end against the protruding heads of the screws 28.

A spring 36 may be installed between the separator 33 and the front end portion of the extension rod 21 when using the linear actuator in an inclined position when the front end portion of the extension rod 21 is below the rear end portion. The spring 36 at one end abuts against the front end of the separator 33, and the other end against the inner wall of the cover 13 of the housing 11.

Thanks to the proposed design, both during axial movement of the extension rod relative to the linear actuator body and during stopping the movement, the action of the moments created by the undesirable load on the extension rod is transmitted through the balls to the body, designed for their perception and compensation. A ball mechanism to compensate for unwanted loads keeps the retractable rod and the entire screw mechanism from shifting relative to the line of longitudinal arrangement of the linear actuator nodes and blocks rotation relative to the housing, without interfering with the axial force transmission. The mechanical gears of the linear actuator, perceiving the axial load, are isolated from the action of the moments created by the unwanted load. At the same time, the efficiency of the moment compensation mechanism does not depend on the direction of action of the unwanted load that creates them, and friction losses are minimized (a rolling ball transfers the load through the contact point). In addition, the absence in any position of the device of the interaction of the sliding surfaces of the contacting parts, perceiving and transmitting undesirable load, excludes the possibility of binding (jamming) or increased wear rate of the rubbing surfaces. Thus, the present invention can significantly improve the reliability of the linear actuator and linear actuator.

Claims (4)

1. A linear actuator, characterized by the presence of an engine with an output shaft and a housing, inside of which there is a screw mechanism and a ball mechanism to compensate for unwanted loads, and the screw mechanism includes a lead screw, a nut interacting with it and a retractable rod concentrically located around at least , parts of the lead screw and connected to the specified nut, while the screw mechanism is connected to the engine so that the rotation of its output shaft causes axial movement of the nut and extendable about the rod relative to the housing, said ball mechanism for compensating for unwanted loads is formed by at least two longitudinal guide grooves on the inner surface of the housing, at least two reciprocal longitudinal guide grooves on the outer surface of the sliding rod and a ball cage with at least two in rows of cells made opposite said guide grooves, in which balls are rotatably disposed that run around the surfaces of these guide grooves AVOK. 2. The linear actuator according to claim 1, characterized in that the ball load compensation mechanism is provided with at least one spring that prevents the ball cage from slipping under its own weight when the linear actuator is inclined. 3. A linear actuator, characterized by the presence of a housing, inside which there is a screw mechanism and a ball mechanism for load compensation, and the screw mechanism includes a lead screw, a nut interacting with it and a retractable rod concentrically located around at least part of the lead screw and connected to the specified nut, while the rotation of the lead screw causes axial movement of the nut and extension rod relative to the housing, while the ball load compensation mechanism is formed, at least two longitudinal guide grooves on the inner surface of the housing, at least two reciprocal longitudinal guide grooves on the outer surface of the slide rod and a ball cage with at least two rows of cells made opposite these guide grooves, in which free rotation placed balls running around the surface of these guide grooves. 4. The linear actuator according to claim 3, characterized in that the ball load compensation mechanism is provided with at least one spring that prevents the ball cage from slipping under its own weight when the linear actuator is inclined.

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