Linear actuator

Abstract

FIELD: mechanical engineering.SUBSTANCE: linear actuator includes a housing, front and rear end pieces, a motor consisting of a stator and rotor, a screw, an extended nut, front, rear and additional rear bearings, a rotation sensor, and front and rear mounts. The stator is rigidly fixed in the housing. The rod passes through a spherical bearing mounted in the front end. The nut is installed on the rear bearings, between the outer and inner rings of which adjusting rings are installed, the left end of the inner ring of the rear bearing rests against the ledge of the nut, and the right end of the inner ring of the additional rear bearing is locked with a locking nut on the threaded section of the extended nut. The rear bearings are installed with their outer rings in the rear end section, with the right end of the outer ring of the additional rear bearing resting against the ledge of the rear end section, and the left end being locked with a locking screw on the threaded section of the rear end section. The magnetic circuit is rigidly fixed on the nut on the rear bearing side, and on the other side it is mounted in the inner ring of the front bearing. A cover is installed on the front end part, the front mount is installed on the rod.EFFECT: increased structural reliability and rigidity, reduced weight and size characteristics, elimination of backlash, and increased precision of the linear drive.7 cl, 3 dwg

Description

[0001] The invention relates to linear drive mechanisms.

[0002] A linear drive is known (US20180335113) comprising a motor comprising a rotor, a stator and a ball bearing, wherein the stator comprises a shaft portion and a spiral portion, the shaft portion and the spiral portion together comprise a receiving space, and the spiral portion comprises a first helical projection formed on its inner surface; a screw shaft coaxially connected to the rotor, wherein one end of the screw shaft comprises a second helical projection formed on its outer surface, and at least a part of the end of the screw shaft is located inside the rotor accommodating space; and a table fixed to the other end of the screw shaft, wherein the first helical projection of the helical portion of the rotor is in engagement with the second helical projection of the screw shaft, wherein when the rotor rotates, the rotor drives the screw shaft and the table connected to the screw shaft for linear movement forward or backward in the axial direction of the rotor.

[0003] The drive has the following disadvantages.

[0004] Limited scope of application. The drive can be used to move the table along a straight guide. However, it cannot be used for curved or rotary guides, as the linear drive will jam.

[0005] The drive cannot be used to drive other objects that do not have linear guides.

[0006] The closest to the proposed technical solution is a linear drive (US20100206103A), including a housing, a front end part, a rear end part, a motor consisting of a stator and a rotor, wherein the front end part and the rear end part are respectively fixed on two opposite ends of the housing, the rotor consists of a magnetic circuit with magnets attached to it, the stator is mounted on the housing through an element of the motor and is located between the magnets and an elongated nut, the elongated nut consists of a threaded sleeve and a support sleeve, the threaded sleeve is fixed on both sides in the support sleeve using the first end cover and the second end cover, there is a front bearing mounted with an inner ring on the first end cover and a rear bearing mounted with an inner ring on the second end cover, on the second end cover the inner ring of the rear bearing is fixed in an axial position with a shoulder and a retaining ring,the front bearing is mounted with its outer ring in the front end part, the rear bearing is mounted with its outer ring in the housing, on one side its outer ring rests against the ledge of the housing, on the other side it is fixed with a retaining ring in the same housing, while the elongated nut with internal thread is able to rotate relative to the housing, the rotor is fixedly mounted in the support sleeve, the rod interacts with the front end part with the ability to rotate and move linearly and has a front fastening in the form of a fork on the outside, on the inside the rod is attached to a screw with an external thread, with which it interacts with the internal thread of the elongated nut, there is a rotation sensor consisting of a rotating and a fixed part, the movable part of the rotation sensor is mounted on the elongated nut on the side of the rear bearing, the fixed part of the rotation sensor is mounted in the rear end part, on the rear end part there is a rear fastening in the form of a fork,the engine is controlled by an external control unit.,

[0007] The known technical solution has the following disadvantages.

[0008] Linear actuator overheating. During intensive operation, the linear actuator may overheat due to the stator being located in the gap between the rotor magnets and the rotor magnetic circuit. Only the end surface of the stator contacts the housing via an intermediate part (the motor element), which hinders heat dissipation from the stator. The heat dissipation problem is exacerbated by the fact that the stator is located in the enclosed internal volume of the linear actuator. If this volume is filled with air or another gas, overheating is possible due to low convection.

[0009] The increased radial dimensions of the linear actuator are determined by the presence of structural clearances between the rotor and housing and between the stator and the extended nut.

[0010] The piston rod may become jammed at the front end. The piston rod is long and thin, and therefore not a rigid structural element. When exposed to transverse forces, such as vibration, impact, or simply gravity, the piston rod will bend, potentially causing it to become jammed in the smooth bore of the front end.

[0011] Low linear travel accuracy.

[0012] The piston rod travels inaccurately from its fully extended to its fully retracted position. When the piston rod retracts, its extreme position is limited by the second end cap. When the piston rod extends, its position is limited by the screw end resting on a plastic part located inside the front end cap. This can lead to breakage of the plastic part. Due to the large number of parts affecting the long dimension chain, the actual piston rod travel will be determined with significant inaccuracy.

[0013] There are no backlash-eliminating devices for the linear actuator. The rear bearing is axially secured by shoulders and retaining rings, which require the bearing rings to be installed with clearance. Therefore, axial backlash is inevitable, affecting the accuracy of the piston rod's movement.

[0014] Potential linear actuator jamming. The front and rear mounts are fork- or eye-shaped. There are no unloading elements in the form of spherical bearings or Hooke hinges. Therefore, if the chassis or frame components of the vehicle and other elements that the linear actuator is supposed to move are imprecisely manufactured, jamming in the mounts will occur. Jamming occurs not because the mounts' rotation axes are not in parallel planes, but due to deformation of the linear actuator components and other attached parts.

[0015] It's impossible to calibrate and set the initial position of the piston rod before installing the linear actuator in the functional unit. If you calibrate the piston rod position in advance and set its initial (zero, home) position before installing it in a higher-level product, there's a high risk of accidentally rotating the piston rod around its axis, which will result in all settings being lost.

[0016] Low load capacity. In the axial position, the extended nut is held by only one rear bearing.

[0017] Low rigidity. When axial force is absorbed, the load is transferred from the piston rod to the screw, from the screw to the threaded tube, from the threaded tube to one of the end caps, from the end cap through the rear bearing to the housing, from the housing to the rear end piece and the rear mount. The force transmission involves a large number of components and joints between them. Therefore, the rigidity of the entire linear actuator will be low.

[0018] The length of the linear actuator cannot be adjusted.

[0019] The technical result is an increase in the reliability of the structure, rigidity, a reduction in weight and size characteristics, the elimination of backlash, and an increase in the operating accuracy of the linear drive.

[0020] The technical result is achieved by a linear drive including a housing, a front end portion, a rear end portion, wherein the front end portion and the rear end portion are respectively fixed on two opposite ends of the housing, a motor consisting of a stator and a rotor, a screw with an external thread interacting with the internal thread of an elongated nut, a front bearing mounted in the front end portion, a rotation sensor, the movable part of which is mounted on the elongated nut, and the fixed part is mounted in the rear end portion, a front mount and a rear mount, a rear bearing, wherein the stator with its outer cylindrical surface is fixedly fixed in the housing, the rod passes through a spherical bearing mounted in the front end portion, the elongated nut is mounted on the rear bearing and an additional rear bearing, between the outer and inner rings of which adjusting rings are installed,the left end of the inner ring of the rear bearing rests against the ledge of the extended nut, and the right end of the inner ring of the additional rear bearing is locked with a locking nut on the threaded section of the extended nut, the outer rings of the rear bearing and the additional rear bearing are installed in the rear end part, while the right end of the outer ring of the additional rear bearing rests against the ledge of the rear end part, and the left end of the outer ring of the rear bearing is locked with a locking screw on the threaded section of the rear end part, the magnetic circuit on the side of the rear bearing and the additional rear bearing is fixedly mounted on the extended nut, and on the other side it is installed in the inner ring of the front bearing, a cover is installed on the front end part, the front mount is installed on the rod.,

[0021] In one embodiment of the invention, the rotor consists of a magnetic circuit with magnets mounted on it,

[0022] In one embodiment of the invention, the rod is made integral with the screw.

[0023] In one embodiment of the invention, the front and rear fastenings are made in the form of Hooke hinges, the elements of which are crackers and pins.

[0024] In one embodiment of the invention, the lid has a profile opening.

[0025] In one embodiment of the invention, the front mount is mounted on the rod using a threaded connection and secured with a lock nut.

[0026] In one embodiment of the invention, a chamfer is made on the rod.

[0027] Figure 1 shows an axonometric view of a linear actuator.

[0028] Figure 2 shows a sectional view of a linear actuator passing through its axis.

[0029] Figure 3 shows a cross-sectional view of the linear actuator.

[0030] The linear drive includes a housing 1, a front end part 2, a rear end part 3. There is a motor consisting of a stator 4 and a rotor, the rotor consists of a magnetic circuit 5 with magnets 6 installed on it, the stator 4 with its outer cylindrical surface is fixedly fixed in the housing 1. The rod 7 is made in one piece with a screw 8 having an external thread 9. The rod passes through a spherical bearing 10 installed in the front end part 2. The screw 8 with an external thread 9 interacts with the internal thread 11 of an extended nut 12. The extended nut 12 is mounted on a rear bearing 13 and an additional rear bearing 14 between the outer and inner rings of which adjusting rings 15 are installed, the selection of the thickness of which provides the required clearance or preliminary axial tension.The left end of the rear bearing's inner race rests against the shoulder of the extended nut, and the right end of the additional rear bearing's inner race is locked with locking nut 16 on the extended nut's threaded section. The rear bearing and additional rear bearing are mounted with their outer races in the rear end section. The right end of the additional rear bearing's outer race rests against the shoulder of the rear end section, and the left end of the rear bearing's outer race is locked with locking screw 17 on the rear end section's threaded section. The magnetic circuit is fixedly mounted on the extended nut 12 on the rear bearing side, and on the other side it is mounted in the inner ring of the front bearing 18. The front 19 and rear 20 fastenings are made in the form of hook hinges, the elements of which are crackers 21 and pins 22. A chamfer 23 is made on the rod 7. A cover 24 having a profile hole 25 is mounted on the front end part.The front mount 19 is mounted on the rod 7 using a threaded connection, which is secured with a lock nut 26. The movable part of the rotation sensor 27 is mounted on an extended nut 12. The fixed part of the rotation sensor 28 is mounted in the rear end part 3.

[0031] The linear actuator works as follows.

[0032] An electric current is supplied to the stator 4 and the stator 4 causes the rotor to rotate, which consists of a magnetic circuit 5 and magnets 6. Since the magnetic circuit 5 is rigidly connected to the extended nut 12, and the magnetic circuit 5 is installed in the front bearing 18, and the extended nut 12 on the rear bearing 13 and the additional rear bearing 14, the extended nut 12 rotates around the axis of the linear drive, while in the axial position, the movement of the extended nut 12 is limited by the rear bearing 13 and the additional rear bearing and 14. The extended nut 12 with its internal thread 11 interacts with the external thread 9 of the screw 8. Since the housing 1 is fixed from axial rotation by means of the rear fastening 20 in the form of a hook hinge, just as the rod 7, made as a single piece with the screw 8, is fixed from axial rotation, the screw 8 with rod 7 receives axial movement relative to body 1.The rotor position is determined by a rotation sensor and the data is transmitted to an external control unit, which supplies the calculated value of electric current to the motor stator.

[0033] The stroke of the rod 7 is limited by resting the ends of the flat 23 of the rod against the edges of the profile hole 25 of the cover 24. The profile hole 25 provides a sufficient gap between the cover 24 and the surface of the rod 7 necessary to compensate for the inaccuracy of the linear drive, but does not allow the rod 7 to inadvertently rotate in an unattached linear drive.

[0034] Linear drive overheating is eliminated by securing the stator's outer cylindrical surface to a housing made of high-thermal-conductivity aluminum alloy. Large surface areas of the stator and housing facilitate heat transfer, while effective convective heat exchange with the surrounding air is possible on the outside. This prevents the linear drive from overheating.

[0035] Small radial dimensions are achieved by the fact that there is only one air gap between the stator and the rotor of the motor, and the magnetic circuit is located directly on the extended nut.

[0036] Elimination of the rod sticking in the front end part is achieved by installing a spherical bearing in the front end part, which compensates for the deformation of the rod when transverse forces occur, for example, during vibration, impacts or simply under the action of gravity.

[0037] Increasing the accuracy of the piston rod stroke from its fully extended to fully retracted position is achieved by reducing the number of structural elements involved in the dimensional chain. Thus, piston rod stroke is limited by the length of the piston rod flat and the thickness of the cap in the area of ​​the profile hole. Thus, piston rod stroke accuracy is determined by only two dimensions.

[0038] Axial play is eliminated or set to a minimum by selecting adjusting rings located between the rear bearing and the additional rear bearing.

[0039] Limited linear actuator jamming is eliminated by installing Hooke hinges (sliders and pins) on the front and rear mounts. Hooke hinges compensate for manufacturing inaccuracies and deformations, preventing the linear actuator rod and housing from rotating around their axes, ensuring jam-free operation.

[0040] The impossibility of calibrating and setting the initial position of the piston rod before installing the linear actuator into the functional unit is eliminated by the presence of a chamfer on the piston rod and a profile hole in the cover. This allows for pre-calibration of the piston rod position and the determination of its initial (zero, home) position before installation in a higher-level product, as the piston rod cannot be accidentally rotated. The profile hole ensures sufficient clearance between the cover and the piston rod surface to compensate for any inaccuracies in the linear actuator's operation, but prevents the piston rod from inadvertently rotating when the linear actuator is not attached.

[0041] Increased load capacity is achieved by installing an additional rear bearing in the rear end part.

[0042] Increased rigidity is achieved by making the piston rod and screw integral, eliminating any flexing between the piston rod and screw. When axial force is absorbed, the load from the piston rod / screw is transferred to the extended nut, which then transfers it directly through two rear bearings on the rear end. Reducing the number of parts and joints involved in force transmission, as well as eliminating the housing, which is typically made of light alloys with a low modulus of elasticity, results in increased rigidity of the linear actuator.

[0043] The drive has the ability to adjust the length by rotating the front mount along the mounting thread on the outer end of the rod and then fixing it with a lock nut.

Claims

1. A linear drive comprising a housing, a front end portion, a rear end portion, the front end portion and the rear end portion being respectively secured to two opposite ends of the housing, a motor consisting of a stator and a rotor, a screw whose external thread interacts with the internal thread of an elongated nut, a front bearing mounted in the front end portion, a rotation sensor whose movable portion is mounted on the elongated nut and whose fixed portion is mounted in the rear end portion, a front mount and a rear mount, a rear bearing characterized in that the stator is fixedly secured in the housing with its outer cylindrical surface, the rod passes through a spherical bearing mounted in the front end portion, the elongated nut is mounted on the rear bearing and an additional rear bearing, between the outer and inner rings of which adjusting rings are installed,the left end of the inner ring of the rear bearing rests against the ledge of the extended nut, and the right end of the inner ring of the additional rear bearing is locked with a locking nut on the threaded section of the extended nut, the outer rings of the rear bearing and the additional rear bearing are installed in the rear end part, while the right end of the outer ring of the additional rear bearing rests against the ledge of the rear end part, and the left end of the outer ring of the rear bearing is locked with a locking screw on the threaded section of the rear end part, the magnetic circuit on the side of the rear bearing and the additional rear bearing is fixedly mounted on the extended nut, and on the other side it is installed in the inner ring of the front bearing, a cover is installed on the front end part, the front mount is installed on the rod., 2. A linear drive according to paragraph 1, characterized in that the rotor consists of a magnetic circuit with magnets installed on it.

3. A linear drive according to paragraph 1, characterized in that the rod is made in one piece with the screw.

4. A linear drive according to paragraph 1, characterized in that the front and rear fastenings are made in the form of Hooke hinges, the elements of which are crackers and pins.

5. A linear drive according to item 1, characterized in that the cover has a profile hole.

6. A linear drive according to paragraph 1, characterized in that the front mount is installed on the rod using a threaded connection and secured with a lock nut.

7. A linear drive according to paragraph 1, characterized in that a chamfer is made on the rod.

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