CN101988570B - Design method of gears and racks for airplane slat actuators - Google Patents

Abstract

The invention relates to a design method for a rack and pinion used in an aircraft slat actuator, comprising the following steps: selecting a large tooth profile angle so that the number of gear teeth is small without undercutting, which is beneficial to the precise manufacture of the gear and the improvement of the tooth root Bending strength; select the gear with a small number of teeth to reduce the gear diameter; select the non-standard modulus of the gear, and make the rack and gear transmission ratio of all actuators in the whole machine the same or similar under the condition of satisfying the strength; use gears of different sizes For the rack actuator, gears and racks of different sizes are selected according to the position of the actuator to adapt to movement in a narrow space; the optimal rack/gear transmission ratio is selected to realize the synchronization of multiple rudder surfaces and multiple actuators Make a conical motion. The design method of the rack and pinion for the aircraft slat actuator of the present invention well solves the problem of the narrow space at the leading edge of the wing, can be widely used in regional airliners, mainline aircraft and small aircraft, and has the advantages of weight Light, simple structure, low cost and other advantages.

Description

Design Method of Rack and Pinion for Aircraft Slat Actuator

technical field

The invention relates to a design method of a rack and pinion for an aircraft slat actuator. the

Background technique

The aircraft has multiple (6-12) symmetrical slats, which are driven by more than 10 actuators. In addition to meeting the performance requirements of the slat movement and ensuring the synchronous movement of multiple actuators driving multiple rudder surfaces, the actuator also needs to be as small in size and light in weight as possible. the

The movement of the slat rudder surface is transmitted to the slat actuator by the power device (motor, gearbox) through the transmission rod system-torque tube, and the planetary gearbox with large transmission ratio: gear-rack, due to the The bar is embedded in the slide rail, and the rotation of the rack drives the movement of the rudder surface connected with the slide rail. the

The usual slat actuators are hydraulic actuators and ball screw pairs, which make linear reciprocating motions to drive the slat deflection. They are either located above the slat slide rail, or on the side of the slide rail, and also need to be connected with the slide rail connector (pulley frame). The actuator plus the connecting piece takes up a lot of space inside the wing, and it cannot be installed in the narrow area at the leading edge of the wing. the

Contents of the invention

The novel rack-and-pinion slat actuator provided by the present invention solves the above-mentioned space problem and has better motion performance. the

For this reason, the rack and pinion that is used for aircraft slat actuator among the present invention is designed like this:

1. Choose a large tooth profile angle, such as 22.5°～28°, increase the root size to improve the bending strength of the tooth root, so that the number of teeth of the gear is less than 17 teeth without undercutting. Preferably, a profile angle of 25° is selected. the

2. Select as few gear teeth z ₁ as possible, such as 10-15, to reduce the gear diameter. However, the number of teeth of the minimum gear should not produce undercutting, otherwise it will reduce the bending strength and cause trouble to manufacture. For a tooth profile angle of 25°, the minimum number of teeth without undercutting is 12. In order to adapt to the large load of the actuator and the internal meshing circle of the large-diameter rack, it is advantageous to use 12 or 13 teeth for the gear.

3. Select the pre-determined gear modulus m ₁ , and adopt the best non-standard gear modulus under the condition of satisfying the strength and load of the torque limiter. The gear modulus is advantageously between 2.5 and 4.5. For example, gear moduli are 4.2933, 2.8182, etc. In addition to meeting the bending strength of gears and racks, it is also conducive to adjusting the rack/gear transmission ratios of all actuators in the whole machine to keep the same or similar.

4. Initially determine the rack/gear transmission ratio to make it similar to the rack/gear transmission ratio of the adjacent slat wing actuators, so as to ensure that multiple rudder surfaces and multiple actuators perform synchronous conical motion. The initially determined transmission ratio The size is related to the speed of the motor, the transmission ratio of the reducer, the deflection angle of the slat and the retraction time, the space at the leading edge of the wing, the position of the slide rail, and the roller;

5. According to the initially determined rack/gear transmission ratio in step 4 and the number of gear teeth z ₁ selected in step 2, the number of round teeth in the rack can be obtained, and the number of round teeth in the rack can be rounded to z ₂ ;Thus determine the rack/gear transmission ratio i;

6. According to the rack/gear transmission ratio i determined in step 5, adjust the initial gear modulus m ₁ to the determined gear modulus m to obtain the gear pitch circle diameter d ₁ ;

7. According to the gear modulus m determined in step 6 and the number z ₂ of the internal meshing circle teeth of the rack determined in step 5, the pitch circle diameter d ₂ of the internal meshing circle of the rack is obtained;

8. When the gear modulus, rack/gear transmission ratio, and rack internal meshing circle are finally determined after multiple revisions and iterations, other parameters of the gear and rack can be determined according to the relevant external and internal meshing in the general gear mechanical design manual. Calculation of geometric dimensions of cylindrical gear transmission. the

Advantageously, the initial rack/pinion ratio is determined by a trade-off of the following three methods:

a. Determine the pitch circle radius of the rack according to the distance from the lower surface of the slide rail where the rack is located to the slat shaft. According to the minimum number of teeth of the gear that does not produce undercut determined by the tooth profile angle selected above and the above-mentioned preliminary gear model The product of the number (m ₁ ) determines the pitch radius of the gear, and divides the pitch radius of the rack by the pitch radius of the gear to obtain the initial rack/gear transmission ratio;

b. Determine the deflection speed (n ₂ ) of the rack according to the deflection angle of the rudder surface and the retraction time requirements. According to the predetermined planetary gear ratio of the slat actuator gearbox and the preset torque tube speed, it can be obtained output gear output speed (n ₁ ), then the initially determined rack/gear transmission ratio (i)=gear output speed (n ₁ )/rack deflection speed (n ₂ );

c. Preliminarily determine the rack/gear transmission ratio according to the ratio of the number of meshing round teeth in the rack to the number of teeth in the gear, and the number of round teeth in the rack is determined according to the radius of the slide rail at the location and the initial gear modulus;

Advantageously, the preset rack/gear transmission ratio is between 16 and 22, for example, the preset rack/gear transmission ratio is 18.846 or 18.833. the

The rack and pinion can be made of low-carbon alloy steel, which is processed by rough forging. It needs overall quenching, and the surface of the teeth is carburized. The surface hardness is HRC52-58. the

The rack and pinion actuator of the present invention has the following advantages:

1. According to the characteristic that the deflection of the slat is not large, the slat is directly driven by a rack and pinion actuator for rotary motion, and the pulley frame is omitted. Moreover, this movement is consistent with the motor output and the movement pattern of the transmission parts, and the rack and the slat movement have the same center and angle, which makes the whole movement simple and flexible. The actuator is small and light, and the speed, load, deflection, Time and other performance indicators have met the design and airworthiness requirements. the

2. The shape of the rack (curve, straight line, etc.) is designed to be similar to the track of the slide rail, so that the rack is embedded in the "∏"-shaped groove of the slide rail and connected to it (see Figure 1). Therefore, the rack does not need to take up extra space, and because the rack bears the load (torque) due to its large radius of curvature (300-530 mm), only a small height of the rack is required. (See Figure 2)

3. The gear diameter is small. Under the maximum load, the diameter of the gear is as small as 33.8 mm, which meets the requirement of extremely small space and is light in weight. (See Figure 3)

4. It solves the problem of narrow space at the leading edge of the wing, and can be widely used in regional airliners, mainline aircraft and small aircraft. It also has the advantages of light weight, simple structure, and low cost. the

Description of drawings

Figure 1 is a schematic diagram of the rack and pinion actuator of the slat wing;

Figure 2 is a schematic diagram of the rack embedded in the slide rail and the gear shaft fixed on the reinforcing rib;

Figure 3 is a schematic diagram of the connection between the gear/rack and the slide rail. the

Detailed ways

The present invention is described in further detail below in conjunction with embodiment. the

1. Calculation of rack and pinion of actuator (embodiment 1)

(1) Select tooth profile angle 25°;

(2) The number of gear teeth is selected to be 12 (also the minimum number of gear teeth without sound undercutting at a tooth profile angle of 25°);

(3) According to the tangential force acting on the rack, the initial modulus of the number of teeth is 2.8;

(4) Initially determine the rack/gear transmission ratio i calculation, and select the best rack/gear transmission ratio according to the following three methods;

a. It is known that the distance between the rotating shaft point of the actuator and the slide rail is 318.455; according to the modulus 2.8 initially obtained in step (2), the pitch circle radius of the gear is 2.8*12/2=16.8, then the transmission ratio i ₁ =318.455 /16.8=18.956;

b. According to the slat deflection angle of 20.855° in 17 seconds, calculate the rack deflection speed as: 17:20.855=60:x, then x=0.2044(rpm), according to the planetary gear ratio: 155.52:1, set The motor is decelerated by the gearbox until the torque tube speed is 550~650 (rpm), then the output speed of the gear can be calculated as: 600/155.52=3.858 (rpm). Here, the torque tube speed is set to 600 rpm, then i ₂ =3.858/0.2044 =18.8747;

c. According to the radius of the inner meshing circle of the rack 318.455 and the modulus of 2.8, the number of teeth of the inner meshing circle of the rack is 318.455*2/2.8=227.5. The number of rack teeth must be an integer, so the number of rack teeth is rounded to 226 or 228. Since the number of gear teeth is 12, the number of circular teeth in the rack is i ₃ =228/12=19 or I ₃ =226/12=18.8333

(5) Considering that the number of gear teeth of the adjacent actuator is 13, the rack/gear transmission ratio of this embodiment and the adjacent actuator should be close to other factors, comprehensive analysis, and finally take the rack/gear of this embodiment The transmission ratio is 18.8333, and the number of circular teeth in the rack is 226. the

(6) Select the modulus of the gear or rack:

According to the radius of the slide rail is the pitch circle radius of the rack and the number of teeth is 226, the modulus m can be obtained

m=318.455*2/226=2.818

The diameter of the pitch circle of the gear is

d ₁ =2.818*12=33.818 mm

(7) The pitch circle diameter of the inner meshing circle of the rack is d ₂ =2.818*226=636.91 mm.

(8) Other parameters of gears and racks can be calculated according to the geometric dimensions of external and internal meshing cylindrical gear transmission in the general gear mechanical design manual. the

For example: gear base circle diameter: d _b =d ₁ conα=33.818*con25°=30.65

Weekly festival: p=m∏=2.818*3.1414=8.854

Base circle pitch p _b =p*conα=8.024

Addendum height h _a ＝m*h _a ^* =2.818h _a ^* 1=2.818

root height $h_f=(h_a^{*}+c^{*})*m=(1+0.2)*2.818=3.38$

Tooth height: h=h _a +h _f =6.20

Addendum circle diameter: d _a =d+2h=33.818+2*2.818=39.454

Root circle diameter: d _f =d-2h _f =27.054

Center distance a=(d ₂ -d ₁ )/2=(636.91-33.818)/2=301.544

Gear ratio u=226/12=18.8333

Addendum pressure angle α _a =arccos(d _b ／d _a )=arcos(30.65/39.454)=39.03°

The calculation results are shown in Table 1. the

In the design of the rack, based on the deflection angle of the slat and the overtravel angle, a certain margin angle is required, so the central angle of 30° of the internal meshing circle of the rack is taken as the rack. the

The width of the rack should be 2 to 3 mm smaller than the width of the tooth groove of the slide rail to compensate for the deformation difference generated by the aerodynamic load on the slide rail and the rib plate. the

2. Calculation of the gear and the rack of the actuator (embodiment 2)

The actuator is located on the inner side of the slat near the fuselage. Compared with the outer actuator, the distance between the intersection point of the actuator and the rotating shaft and the slide rail is larger, and the load capacity is larger. A larger modulus should be adopted, the number of gear teeth should be increased, and iterative adjustments should be made to achieve a rack/gear transmission ratio similar to that of other actuators, so as to ensure the synchronous movement of multiple rudder surfaces and multiple actuators. Its calculation steps:

Select 13 gear teeth;

Preliminarily determine the rack/gear transmission ratio i ₁ of the actuator according to the rack and gear calculation method of the actuator 1, and make i ₁ close to i in the actuator 1;

According to the length of the actuator rack shaft from the radius of the slide rail is 525.935, the number of gear teeth is 13, and i=18.8333, the number of teeth (after rounding) of the internal meshing circle of the rack is calculated to be 245;

The rack/gear transmission ratio is i=245/13=18.8462,

The error of the two actuators i is Δ=(18.8462-18.8333)/18.8333=0.69%,

The gear/rack modulus is m=525.935*2/245=4.293,

Gear pitch circle diameter d ₁ =4.293*13=55.81 mm,

The pitch circle diameter of the inner meshing circle of the rack d ₂ =525.937*2=1051.87 mm,

Other gear and rack parameters can be calculated according to the geometric dimensions of external and internal meshing cylindrical gear transmission in the general gear machinery design manual. The calculation results are shown in Table 2. the

In the rack design, the overtravel angle can be considered based on the slat deflection angle, and a certain angle margin is required. Therefore, the central angle of 30° of the internal meshing circle of the rack is taken as the rack. the

The width of the rack should be 2 to 3 mm smaller than the width of the tooth groove of the slide rail to compensate for the deformation difference generated by the aerodynamic load on the slide rail and the rib plate. the

Table 1 Relevant geometric parameters of the pinion/rack actuator of Example 1

It should be understood that the embodiments of the present invention are intended to illustrate rather than limit the invention, and the invention is not limited to the details described herein. As long as they are within the scope of the spirit of the present invention, changes and modifications to the above-described embodiments will fall within the scope of the claims of the present invention. the

Table 2 Relevant geometric parameters of the pinion/rack actuator in Example 2. the

Claims (12)

1. A design method for a rack and pinion of an aircraft slat actuator, comprising the steps: (1) Select the tooth profile angle so that the number of gear teeth is small without undercutting; (2) select the number of gear teeth z ₁ ; (3) Initially determine the gear modulus m ₁ according to the tangential force acting on the rack; (4) Initially determine the rack/pinion transmission ratio so that it is similar to the rack/pinion transmission ratio of the adjacent slat actuator; (5) According to the rack/gear transmission ratio initially determined in the above step (4) and the number of gear teeth z ₁ selected in the step (2), the number of round teeth in the rack can be obtained, and the number of round teeth in the rack can be calculated as rounded to z ₂ ; thus determine the rack/gear ratio i; (6) According to the determined rack/gear transmission ratio i, adjust the initial gear modulus m ₁ to the determined gear modulus m to obtain the pitch circle diameter d ₁ of the gear; (7) According to the determined gear modulus m and the number z ₂ of the internal meshing circle of the rack, the pitch circle diameter d ₂ of the internal meshing circle of the rack is obtained; (8) Other parameters of the gear and rack can be calculated according to the number z ₁ of the gear teeth, the number z ₂ of the meshing round teeth in the rack and the determined gear modulus m. 2. The design method according to claim 1, wherein the step (4) initially determines the rack/gear transmission ratio in the following three ways: a. Determine the pitch circle radius of the rack according to the distance from the lower surface of the slide rail where the rack is located to the slat shaft. According to the minimum number of teeth of the gear that does not produce undercut determined by the tooth profile angle selected above and the above-mentioned preliminary gear model The product of the number _m1 determines the pitch radius of the gear, and divides the pitch radius of the rack by the pitch radius of the gear to obtain the initial rack/gear transmission ratio; b. Determine the deflection speed n ₂ of the rack according to the deflection angle of the rudder surface and the retraction time requirements, and calculate the gear according to the predetermined planetary gear ratio of the slat actuator gearbox and the preset torque tube speed output speed n ₁ , then the initially determined rack/gear transmission ratio i = gear output speed n ₁ / rack deflection speed n ₂ ; c. Preliminarily determine the rack/gear transmission ratio according to the ratio of the number of round teeth in the rack to the number of teeth in the gear. The number of round teeth in the rack is based on the radius of the slide rail at the position and the gear modulus initially determined in the above step (3). to make sure. 3. The design method according to claim 2, wherein the selected profile angle is between 22.5° and 28°. 4. The design method according to claim 3, characterized in that the selected number of teeth is 10-15. 5. The design method according to claim 4, characterized in that the selected number of teeth is 12 or 13. 6. The design method according to claim 5, characterized in that the preset gear modulus is between 2.5 and 4.5. 7. The design method according to claim 6, characterized in that the initially determined gear modulus is 4.2933. 8. The design method according to claim 6, characterized in that the initially determined gear modulus is 2.8182. 9. The design method according to claim 8, characterized in that the preset rack/gear transmission ratio is between 16-22. 10. The design method according to claim 9, characterized in that the initially determined rack/pinion transmission ratio is 18.846. 11. The design method according to claim 9, characterized in that the initially determined rack/pinion transmission ratio is 18.833. 12. The design method according to any one of claims 1 to 11, characterized in that the rack and pinion are made of low-carbon alloy steel, processed by rough forging, integrally quenched, carburized on the surface of the gear teeth, and the surface hardness is HRC52～ 58, the precision of the gear is 6 groups, and the rack is 7.