Eccentric lead screw shifting fork transmission structure

Abstract

The invention discloses an eccentric lead screw shifting fork transmission structure which comprises a lead screw, a lead screw nut, a shifting fork shaft, a trunnion, a first bearing, a second bearing, a third bearing and a fourth bearing. The lead screw nut is arranged on the outer surface of the middle of the lead screw in a sleeving mode. One end of the lead screw is connected with the first bearing, and the other end of the lead screw is connected with the second bearing; the middle part of the trunnion is connected with the lead screw nut; one end of the trunnion is located in one U-shaped groove of the shifting fork shaft, and the other end of the trunnion is located in the other U-shaped groove of the shifting fork shaft. One end of the shifting fork shaft is connected with the third bearing, and the other end of the shifting fork shaft is connected with the fourth bearing. The torque locking function is achieved under the condition that an electromagnetic lock is not added, and the structural and electrical complexity is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of aerospace equipment, and in particular relates to an eccentric lead screw fork transmission structure. Background Art

[0002] Nowadays, the demand for angle output servo mechanisms in aerospace equipment is becoming more and more obvious. The screw-type transmission is more and more widely used due to its transmission stiffness and input and output speed advantages. In airborne guidance, the zero-position locking capability of the air rudder is required. The current locking method mainly increases the zero-position locking torque of the servo rotation mechanism through an electromagnetic lock, which has the disadvantages of complex structure, complex electronic control, and large space occupation.

[0003] National invention patent CN10563419A is a modular parallel electromechanical actuator. The locking function is installed on the reducer housing through an electromagnetic lock to achieve torque locking function, which occupies a large space and is heavy;

[0004] National invention patent ZL201911043356.2 is a miniature fork-type four-position modular electric servo. The screw fork drive is a conventional fork drive, which fails to maximize the reduction ratio within the existing space. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and provide an eccentric screw fork transmission structure, by eccentrically setting the screw fork transmission of the servo actuator, thereby increasing the transmission ratio within the limited space of the servo mechanism, and at the same time increasing the locking torque value of the reverse transmission, thereby realizing the torque locking function without adding an electromagnetic lock.

[0006] The objective of the present invention is achieved through the following technical scheme: an eccentric screw fork transmission structure, comprising: a screw, a screw nut, a fork shaft, an ear shaft, a first bearing, a second bearing, a third bearing and a fourth bearing; wherein the screw nut is sleeved on the middle outer surface of the screw; one end of the screw is connected to the first bearing, and the other end of the screw is connected to the second bearing; the middle part of the ear shaft is connected to the screw nut; one end of the ear shaft is located in a U-shaped groove of the fork shaft, and the other end of the ear shaft is located in another U-shaped groove of the fork shaft; one end of the fork shaft is connected to the third bearing, and the other end of the fork shaft is connected to the fourth bearing.

[0007] In the above-mentioned eccentric screw fork transmission structure, the screw and the screw nut form a screw pair, and the rotation of the screw drives the screw nut to perform translational and linear motion, thereby converting the rotation into translational and linear motion.

[0008] In the above-mentioned eccentric screw fork transmission structure, the first bearing and the second bearing are both angular contact bearings.

[0009] In the above-mentioned eccentric screw fork transmission structure, the third bearing and the fourth bearing are both cylindrical roller bearings or needle roller bearings.

[0010] In the above eccentric screw fork transmission structure, the ear shaft rolls and slides in the U-shaped groove of the fork shaft during the movement.

[0011] In the above-mentioned eccentric screw fork transmission structure, the matching tolerance between the ear shaft and the fork shaft is H / g.

[0012] In the above-mentioned eccentric screw fork transmission structure, the surface hardness of both the ear shaft and the fork shaft is not less than HRC~HRC.

[0013] In the above-mentioned eccentric screw fork transmission structure, the center of the ear shaft deviates from the center of the screw nut.

[0014] In the above eccentric screw fork transmission structure, the output torque of the fork shaft is:

[0015] T = F*(R+e);

[0016] Wherein, T is the output torque of the fork shaft, F is the force applied to the ear shaft, R is the distance between the center of the screw nut and the center of the fork shaft, and e is the eccentricity between the ear shaft and the screw nut.

[0017] In the above eccentric screw fork transmission structure, the screw nut will generate a bending moment M=F·e relative to the screw.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention adopts an eccentric transmission design to improve the transmission reduction ratio in a limited space, which is conducive to realizing the miniaturization design of the product;

[0020] (2) The present invention increases the zero-position reverse self-locking capability, which can eliminate the electromagnetic lock structure, reduce the complexity of the structure and electrical, and facilitate the lightweighting of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0022] Figure 1is a schematic diagram of an eccentric screw fork transmission structure provided by an embodiment of the present invention;

[0023] Figure 2 is another schematic diagram of the eccentric screw fork transmission structure provided by an embodiment of the present invention;

[0024] Figure 3 is a schematic diagram of a non-eccentric structure provided by an embodiment of the present invention;

[0025] Figure 4 It is a force diagram of the eccentric screw fork transmission structure provided by an embodiment of the present invention;

[0026] Figure 5 This is a force diagram of a spiral transmission with a non-eccentric structure provided by an embodiment of the present invention;

[0027] Figure 6 A schematic diagram of the spiral transmission force of the eccentric screw fork transmission structure provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] Figure 1 is a schematic diagram of an eccentric screw fork transmission structure provided by an embodiment of the present invention; Figure 2 FIG. 2 is another schematic diagram of the eccentric screw fork transmission structure provided by an embodiment of the present invention. Figure 1 and Figure 2 As shown, the eccentric screw fork transmission structure includes: a screw 1, a screw nut 2, a fork shaft 3, an ear shaft 4, a first bearing 51, a second bearing 52, a third bearing 61 and a fourth bearing 62.

[0030] The lead screw nut 2 is sleeved on the middle outer surface of the lead screw 1; one end of the lead screw 1 is connected to the first bearing 51, and the other end of the lead screw 1 is connected to the second bearing 52; the middle of the ear shaft 4 is connected to the lead screw nut 2; one end of the ear shaft 4 is located in a U-shaped groove of the fork shaft 3, and the other end of the ear shaft 4 is located in another U-shaped groove of the fork shaft 3; one end of the fork shaft 3 is connected to the third bearing 61, and the other end of the fork shaft 3 is connected to the fourth bearing 62. The center of the ear shaft 4 deviates from the center of the lead screw nut 2.

[0031] The lead screw 1 and the lead screw nut 2 form a lead screw pair. The rotation of the lead screw 1 drives the lead screw nut 2 to translate and linearly move, thereby converting the rotation into translation and linear motion.

[0032] The first bearing 51 and the second bearing 52 are both angular contact bearings. The third bearing 61 and the fourth bearing 62 are both cylindrical roller bearings or needle roller bearings. During the movement, the ear shaft 4 rolls and slides in the U-shaped groove of the fork shaft 3.

[0033] The matching tolerance of the ear shaft 4 and the fork shaft 3 is H7 / g6. The surface hardness of the ear shaft 4 and the fork shaft 3 is not less than 56HRC-60HRC.

[0034] The output torque of the fork shaft 3 is:

[0035] T = F*(R+e);

[0036] Among them, T is the output torque of the fork shaft 3, F is the force applied to the ear shaft 4, R is the distance between the center of the screw nut 2 and the center of the fork shaft 3, and e is the eccentricity between the ear shaft 4 and the screw nut 2.

[0037] The screw nut 2 generates a bending moment M=F·e relative to the screw 1 .

[0038] Paired bearings (a first bearing 51 and a second bearing 52) are installed at both ends of the screw 1. The screw 1 and the screw nut 2 form a screw pair for spiral transmission, that is, the rotation of the screw 1 drives the screw nut 2 to move in a translational linear motion, thereby converting the rotation into a translational linear motion. An ear shaft 4 is arranged on the screw nut 2, and the two are of integrated design. When the screw nut 2 moves in a translational linear motion, the ear shaft 4 drives the fork shaft 3 to rotate, and then converts the translational linear motion into rotation, thereby outputting speed and torque through the fork shaft 3.

[0039] The bearings at both ends of the lead screw 1 are paired angular contact bearings, and the bearings (the third bearing and the fourth bearing) at both ends of the fork shaft 3 are supported by cylindrical roller bearings or needle bearings.

[0040] The fork shaft 3 is provided with a U-shaped groove, which cooperates with the ear shaft 4. During the movement, the ear shaft 4 rolls and slides in the U-shaped groove of the fork shaft 3. The recommended matching tolerance is H7 / g6, and the surface hardness of both is not less than 56HRC~60HRC;

[0041] like Figure 3 As shown, the center of the conventional non-eccentric screw pair fork transmission trunnion is set on the screw pair axis; Figure 4 As shown, the center of the ear shaft 4 of the present invention deviates from the center position of the screw nut, and is away from the center position of the fork shaft 3. When the eccentricity is e at the zero position shown in the figure, the output torque T=F*(R+e); Figure 3As shown, the output torque of the conventional non-eccentric screw pair fork transmission is T = F*R. Due to the existence of the eccentricity e, the reduction ratio increases, and a larger torque can be output under the same F condition, thereby providing a greater reverse self-locking ability.

[0042] The non-eccentric screw pair transmission simplifies the force according to the principle of screw transmission, simplifies the screw raceway into an inclined plane, and simplifies the screw nut into a slider, such as Figure 3 As shown in the figure, at the zero position, the force of the conventional non-eccentric screw pair fork transmission is as follows Figure 5 As shown in the figure, the friction force f = u·F·sina. Figure 4 As shown, due to the existence of the eccentricity e, the screw nut 2 will generate a bending moment M=F·e relative to the screw rod 1. The existence of the bending moment will cause the screw rod 1 and the screw nut 2 to generate the following Figure 6 The pressure Fm is shown, and the friction force f=u·(F·sina+Fm) at this time, so the force required to reversely drive the screw pair increases, thereby improving the reverse self-locking ability of the servo mechanism.

[0043] The eccentricity e should be set according to actual needs, generally 3% to 10% of R. The diameter of the screw 1 must meet the stiffness requirements, and the matching length of the screw nut 2 and the screw 1 should be increased as much as possible.

[0044] The eccentricity is generally taken as e = (3% ~ 10%) · R, which can not only meet the locking torque requirements, but also ensure that the screw 1 can withstand the corresponding bending moment, and has little effect on the efficiency of the forward transmission. When the preload torque of the screw pair is 0.1 ~ 0.2Nm, R = 30mm, e = 2mm, the measured locking torque is 40Nm.

[0045] The lead of the screw pair composed of the screw rod 1 and the screw nut 2 should be as small as possible to increase the zero-position self-locking capability.

[0046] This embodiment adopts an eccentric transmission design to improve the transmission reduction ratio in a limited space, which is conducive to the miniaturization of the product design; this embodiment increases the zero-position reverse self-locking capability, which can eliminate the electromagnetic lock structure, reduce the complexity of the structure and electrical, and is conducive to the lightweight of the product.

[0047] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. An eccentric screw fork transmission structure, characterized in that include: A lead screw (1), a lead screw nut (2), a shift fork shaft (3), a trunnion (4), a first bearing (51), a second bearing (52), a third bearing (61) and a fourth bearing (62); wherein, The lead screw nut (2) is sleeved on the middle outer surface of the lead screw (1); One end of the lead screw (1) is connected to the first bearing (51), and the other end of the lead screw (1) is connected to the second bearing (52); The middle part of the ear shaft (4) is connected to the lead screw nut (2); One end of the ear shaft (4) is located in a U-shaped groove of the fork shaft (3), and the other end of the ear shaft (4) is located in another U-shaped groove of the fork shaft (3); One end of the shift fork shaft (3) is connected to the third bearing (61), and the other end of the shift fork shaft (3) is connected to the fourth bearing (62).

2. The eccentric screw fork transmission structure according to claim 1, characterized in that: The lead screw (1) and the lead screw nut (2) form a lead screw pair, and the lead screw (1) rotates to drive the lead screw nut (2) to perform translational and linear motion, thereby converting the rotation into translational and linear motion.

3. The eccentric screw fork transmission structure according to claim 1, characterized in that: The first bearing (51) and the second bearing (52) are both angular contact bearings.

4. The eccentric screw fork transmission structure according to claim 1, characterized in that: The third bearing (61) and the fourth bearing (62) are both cylindrical roller bearings or needle roller bearings.

5. The eccentric screw fork transmission structure according to claim 1, characterized in that: During the movement, the ear shaft (4) both rolls and slides in the U-shaped groove of the fork shaft (3).

6. The eccentric screw fork transmission structure according to claim 5, characterized in that: The matching tolerance between the ear shaft (4) and the fork shaft (3) is H7 / g6.

7. The eccentric screw fork transmission structure according to claim 5, characterized in that: The surface hardness of both the ear shaft (4) and the fork shaft (3) is not less than 56HRC-60HRC.

8. The eccentric screw fork transmission structure according to claim 1, characterized in that: The center of the ear shaft (4) deviates from the center of the screw nut (2).

9. The eccentric screw fork transmission structure according to claim 1, characterized in that: The output torque of the shift fork shaft (3) is: T = F*(R+e); Wherein, T is the output torque of the fork shaft (3), F is the force applied to the ear shaft (4), R is the distance between the center of the screw nut (2) and the center of the fork shaft (3), and e is the eccentricity between the ear shaft (4) and the screw nut (2).

10. The eccentric screw fork transmission structure according to claim 9, characterized in that: The screw nut (2) generates a bending moment M=F·e relative to the screw (1).

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