BG66144B1 - A cylindrical straight gear transmission with external meshing - Google Patents

Abstract

The cylindrical straight gear transmission with external meshing finds application in transmission boxes, reducers, gear hydro machines, compressors, and others. By it may be transferred continuous rotational motion from one gear to another in case of small number of teeth. The transmission contains a driving (1) and a driven (2) gear with parallel axes of rotation and small number of straight teeth with nonsymmetrical profiles. The teeth have a concave (4) and a convex (3) side and are profiled by three different curves. The first one (MN), outlining the concave side (4), is an equidistant curve of an elongated epicycloid. By the second (KL), which is an evolvent curve, is profiled the convex side (3), while by the third (LM) is shaped the top of the tooth (5) as a circular arc. The concave tooth profile (4) of one of the gears is a wrapper of the relative positions, which occupy the top round profile (5) of the other gear during their turn, and the evolvent profiles (3) of the driving and driven gear are with increased length what provides for their uninterrupted meshing with a ratio of face overlapping larger than one.

Description

Technical field

The invention relates to cylindrical gears with external gearing, which will find application in mechanical engineering as a non-reverse gear train for the transmission of continuous rotational motion between parallel shafts with a small number of teeth in different types of drives, gearboxes, gears, gears, gears compressors, fans and more.

BACKGROUND OF THE INVENTION

The known gearing is a cylindrical gear with external gearing (1) formed by a leading and driven wheel with symmetrical involute teeth, in which the axes of rotation of the two wheels are parallel. In addition, the diameters of the tips of the teeth are selected such that the coefficient of overlap in the gear is in the range from 1.03 to 1.2. As a result, the transmission of movement from the guide wheel to the drive wheel is carried out without interruption, and when a tooth pair emerges from engagement, the next tooth pair is already engaging.

Typical of the known gearing gear is that it cannot be used to transmit continuous rotational motion from the drive wheel to the drive wheel if the gears have two, three, four or five teeth. With this small number of teeth, the coefficient of frontal overlap of the known involute gear with symmetrical engagement is less than one, and when a tooth pair emerges from the engagement, the subsequent tooth pair has not yet engaged.

Also known is a special gear used in Ruth's compressors (2) formed by two identical wheels with two or three symmetrical teeth. The latter may have a cycloid or involute profile. In this case, too, because of the low coefficient of frontal overlap, which most often takes the value 0.5, the leading gear wheel is not able to continuously transmit motion to the guide gear. Therefore, a second drive tooth of the gear unit is mounted outside the compressor housing to the drive shaft and the drive shaft, at which the overlap ratio is greater than 1.

This special two or three-tooth gearbox has a complicated compressor structure, resulting from its low overlap ratio and the need for a second drive gear to provide continuous transmission between the drive and the drive shaft of the compressor.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a cylindrical gearing with external gearing formed by two identical or different wheels with two, three, four or five teeth having such a geometric shape that allows the rotational motion of one wheel to be transmitted smoothly and without interruption on the other wheel, in which the coefficient of frontal overlap of the gear in the working direction of travel is greater than one.

The problem is solved by a cylindrical spur gear with external gearing, which contains guide and drive gears with parallel axes of rotation and a small number of straight teeth, on which the contact side profiles of one joint of the teeth of the two wheels are involute curves. According to the invention, the opposite side profiles form asymmetrical teeth of the driving and driving wheels with the concave and convex side, the concave side being an equilateral curve of the elongated epicycloid and the convex side containing the involute profile and at the same time shaped as an arc of a circle that touches seamlessly at the outermost points of the various opposing tooth profiles. In this case, the concave tooth profile of one wheel is a shell of the relative positions occupied by the tip circular profile of the other gear wheel as they are rotated, and the involute profiles of the guide and drive wheels are of extended length, ensuring their continuous engagement with a coefficient of coefficient from one.

In one embodiment, the gear wheels are the same and have two, three,

66144 Bl four or five teeth.

In another embodiment, the center of the circle profiled by the tip of the asymmetrical tooth lies in a straight line passing through the outermost point of the convex involute profile as tangent to the main circle of the gear wheel on which the starting point of the involute profile is located.

The advantage of the gear according to the invention stems from the particular geometric shape of the contacting teeth, whereby a coefficient of overlapping in the working direction of the teeth is obtained by lengthening the profiles on one side of the teeth and properly shaping the other side and the tips of the teeth. movement larger than one when engaging wheels with two, three, four and five teeth. As a result, at the time of engagement, a pair of elongated profiles was attached, the preceding pair of profiles of the same species had not yet emerged from the engagement, and it was possible to transmit a continuous rotational motion from one gear wheel to the other with a small number of teeth.

Explanation of the annexed figures

Figure 1 shows a planar representation of a toothless gear engagement formed by two identical two-tooth wheels;

Figure 2 is a view explaining the geometric shape of the profiles of the asymmetrical tooth;

Figure 3 shows the sequential positions that occupy the gears of two teeth in the gearing process;

Figure 4 shows the gearless gearing of a gear formed by two identical three-wheeled wheels.

Examples of carrying out the invention

The cylindrical gearing with external gearing consists of two gears 1 and 2 with outer teeth having parallel axes of rotation, one of which is leading and the other is driven. Both gear wheels have the same or different small number of teeth. Each of the wheels has asymmetrical teeth on which the working side 3 is convex and the non-working side of 4 is concave. The geometric shape of each tooth is obtained from three serially connected curves. The first curve shaping the convex side 3 of the tooth is the involute curve KL, starting from the point K lying on the base circle having radius r _b and ending at the point L. The involute curve is obtained as a trajectory of point L from line 7, when it rolls without sliding along the main circle 8. With the second curve is profiled the tip 5 of the tooth in the section from point L to point M. This curve LM is an arc of a circle with center O _p and radius r _p , providing its smooth binding to the lateral profiles of the tooth. The third MN curve forming the concave side 4 of the tooth is the equilateral curve of the elongated epicycloid. It is obtained as a wrapping curve of the relative positions occupied by the arc LM from the tip 5 of the tooth of one wheel in the plane of the other wheel while performing a synchronous rotation simulating their engagement. The tooth thus formed with three different curves 3,4 and 5 is asymmetrical with respect to the radial straight line 6, representing the symmetry of the tooth, if the lateral profiles 3 and 4 are two equally convex involutes. Each of the gears is characterized by four concentric circles: apex, internal, primary and initial. The top circle of radius d _and passes through the tops of the teeth and the inner circle having a radius r _p is tangent to the bottoms of the gullets. The main circle of radius _b is used to construct the involute profile, and the initial circles tangent to the engagement pole P represent the centroids of the wheels 1 and 2 in the gearbox with wheelbase a _w .

In one embodiment, the gears 1 and 2 of the gear unit are the same and have two, three, four or five teeth.

In another embodiment, the center O _p of the circle, profiled by the tip 5 of the asymmetrical tooth, lies on a straight line 7 tangential to the main circle 8 of the gear, passing through the outermost point L of the involute profile 3.

Application of the invention

The action of the cylindrical gearing with external gearing is as follows. At

66144 Bl rotation of the drive gear 1 with an angular velocity of omega] in the indicated direction, owing to the contact between the engaged gear profiles 3, the drive gear 2 is rotated in the opposite direction with an angular velocity of the omega ₂ , 5 in which the ratio between the angular velocities of the ratio of the number of teeth of the two wheels. In the process of gear engagement, the contact points kj, k ₂ , kj, k ₄ , k ₅ , etc. between the involute 10 profiles lie on the engagement line AB, obtained as a common tangent to the two main circles of the engaged wheels. In this case, the adhesion between the involute profiles begins at point A and ends at point B. The geometry 15 of the gearbox is selected such that, as a result of the elongation of the involute profiles 3 on wheels with a small number of asymmetrical teeth, the length of the engagement line AB is 8. As a consequence, when engaging a pair of involuntary profiles, the previous tooth pair of the same species has not yet emerged from the engagement, which guarantees a coefficient of frontal adhesion. ditching greater than 25 units in the working direction of travel. In the actual engagement of the lateral involute profiles, the circular tips 5 of the teeth of one wheel smoothly bypass the concave profile 4 of the teeth of the other wheel with a guaranteed lateral clearance. In the non-operating direction of movement, a gear ratio of less than one is less than one, which is why asymmetrical gearing is applicable to non-reversible gears.

Claims (3)

1. Cylindrical gearing with external gearing, containing guide and guide gears with 40 parallel gears and a small number of straight teeth, to which the contact side profiles on one side of the teeth of the two wheels are involute curves, characterized by that the opposite lateral profiles (3 and 4) form asymmetrical teeth of the leading (1) and the driven (2) wheel with concave and convex side, the concave side (4) being an equilateral curve of the elongated epicycloid (MN) and the convex side (3) contains the event profile (KL) and at the same time the tips (5) of the teeth are profiled with a third curve (LM), shaped like an arc of a circle, touching smoothly at the extreme outer points (L and M) of the different opposing profiles (3 and 4) of the teeth, at which is the concave gear profile (4) of one wheel (1 or 2) being a shell of the relative positions occupied by the top circular profile (5) of the other gear wheel (2 or 1) as they are rotated, and the involute profiles (3) of the leading (1) and the steerable (2) wheel are of extended length, ensuring their continuous engagement by a factor of but overlap greater than one. Cylindrical outer gear gearbox according to claim 1, characterized in that the gears (1 and 2) of the gearbox are the same and have two, three, four or five teeth. Cylindrical gear outer gear engagement according to claim 1, characterized in that the center (O _p ) of the circle, profiled by the tip (5) of the asymmetrical tooth, lies in a straight line (7) passing through the end outer point (L ) of the convex involute profile (3) as tangent to the main circle (8) of the gear wheel (1 or 2), on which the starting point (K) of the involute profile (3) is located.