Equipment is a wide range of parts in life, and it will be used in aviation, cargo, cars, etc. However, when the equipment is designed and processed, the number of speeds is necessary.
So why is 17? Instead of other figures? As for 17, it involves starting with the equipment treatment method.
When manufacturing speeds in this way, when the number of teeth is small, root cuts occur, which will affect the resistance of the manufactured equipment. What is the root cut is cut. Petrol petrol notice the red part of the figure:
When the jack point of the gear and the mesh line exceeds the limit point of the cutting gear, part of the root of the speed tooth is cut by the progressive opening of the speed tooth.
So, under what circumstances can the root cuts avoid? The answer is this 17 (when the upper upper coefficient of the tooth is 1, the pressure angle is 20 degrees).
First of all, the equipment can turn because a good transmission relationship is formed between the upper equipment and the lower gear. Take the gradual opening of the equipment, for example, the mesh between the two gears can play its role, and it is divided into two types: cylindrical and oblique cylindrical gears.
The standard right equipment is the top above the tooth, and the tooth height coefficient is 1.25, and the degree of the pressure angle of its pressure must reach 20 degrees.
If the number of teeth in the embryo is lower than a specific value, the root of the dental root will be dug, which is called the cut root. The 17 mentioned here are for the gears.
In addition, 17 is a quality of quality, that is to say that the number of coincidences of a certain tooth of the equipment and other gears is the least to a certain number of reasons, and this Will not be at this stage for a long time when it is stressed. Equipment is an instrument of precision. the long term.
But the problem is! There are still many gears that are less than 17 teeth on the market.
Some Internet users have pointed out that in fact, if a treatment method is changed, it is normal to make a standard to make a standard of less than 17. Of course, these gears are also easy to get stuck (due to the Interference of equipment, you cannot find the image, please compensate), so you cannot turn it. There are also many corresponding solutions. There is also a panoramic gear.
Another point of view of interest: everyone seems too raw in the book. Equipment of the treatment equipment. (There is no heating treatment of the R angle tool R is the clear part of the constraint concentration and it is easy to crack, and it is easy to wear or crack during the knife, It may not be 17 teeth.
You can see from the figure only when the knife with 0 corners on the top of the front knife is treated from the corner of 0, the transition curve from 15 to 18 teeth has not changed significantly.
This image must be painted with the Chengyi cruise fan in this image.
The purple extension curve of the purple extension of the part of the dental root in the above figure is the dental line of the root of the tooth after the root of the tooth is cut. This is determined by the relative movement of the other speed of speed tooth and the resistance reserve of the speed tooth root. The non-gradual opening of the tooth, a progressive opening tooth outline and a non-gradual open tooth tooth outline on a non-specific design are generally not satisfactory, that is to say interference).
From this image, we can see that the mesh line of these two gears has just wiped the maximum diameter circle of the transition curve of the two gears (Note: the purple part is a gradual opening tooth, the Yellow part is the cut root cut, and the mesh line, it is impossible to enter the basic circle, because under the basic circle cannot be gradually opened, the mesh point of the two equipment to any What position is on this line), that is to say that these two equipment can simply be in normally.
Some people say: first of all, this question is made of errors. Do with the number of teeth), but 17 teeth are in some way in some cases, there will be drawbacks of treatment.
Let’s talk about gradual opening. So why is it gradually opening? What is the difference between this line and the arc? As the figure below shows, it is a progressive opening (there is only a half-tooth gradually opened here).
Gradually open the line in one word, suppose that the line does not move with it. Its advantages are obvious.
When the two -wheeled rotation, the direction of the role of the point of contact (like M, M ‘) is constant on the same line, and this straight line and the two progressive contact surfaces (cut surfaces) remain vertical. , they, they, they “slipped” and “friction” will not be produced between them, which also objectively reduces the friction of the mesh of the equipment, which can not only improve the efficiency, but also prolong the duration of equipment life.
Of course, because the most application of the opening of major dental – gradual is not our only choice.
In addition, the “root cut”, as an engineer, we must not only consider the theoretical level which is not possible, the effect is good or bad, it is also the key to finding theoretical things. , tests, etc. awaiting links.
The treatment methods commonly used in equipment are generally divided into training method and as ventilation of the Chengcheng method. are cook me, one of which is very hard (knife), and the other is still in a state of embryo for the hair. to study.
The use of the Cheng fan method is widely used, but when the number of gear teeth is low, there will be the intersection of the upper line of the knife and the mesh line of the tool, which exceeds The situation of the mesh limit of the cutting equipment limit. is used in the gearbox and other heavy load opportunities, it is used. 8 dental gears.
17 is the limits calculated by the standard of equipment in my country. Variable position.
Of course, the content described here is not complete.
Conclusion: 17 teeth come from the treatment method and depend on the treatment method. phenomenon.
In addition, from this question and its answers, we can see the characteristics of mechanical discipline – theory and practice are very combined.
Point of view of the mechanical hydraulic forum: first of all, it is incorrect that the gear less than 17 teeth cannot be turned below.
The equipment refers to the mechanical elements with a continuous mesh and a power on the edge of the wheel.
Gradually open the gear and a cylindrical gear cylindrical gear / a cylindrical switch of oblique tooth, etc. 20 °. During the treatment of devices, it is generally treated by the Fancheng method, that is to say that the movement of the tool and the teeth during treatment is like a pair of rises that rise. For the treatment of standard gears, if the number of teeth is less than a certain value, the outline of the gradual opening of the root of the dental explosion will be dug. 2 * 1 / sin (20) ^ 2 (1 is the high coefficient from above the tooth, 20 is the pressure angle).
The 17 teeth here are for standard straight cylindrical gears. As indicated below, if the complete steps come out again.
Once the equipment is variable, the equipment can be returned without affecting.
In fact, the oblique equipment can also avoid cutting the root of the equipment or the minimum dental value of the root cut.
17 This number is calculated. This does not mean that a small 17 gears cannot be turned, but if less than 17 teeth are less than 17 years, it is easy to cut the speed root to cut a part of the open line treated during the treatment of The gear, that is to say the root cut, which weaken resistance to the gear. As for how to calculate, it is a mathematical problem.
Netizen’s point of view: if the number of speeds can be less than 17 is a question to consider. For standard gears, the number of teeth should not be less than 17 years old, why. Since when the number of teeth is less than 17, the gear cutting phenomenon occurs.
The So-Salled root cut means that when the Chengfa fan cuts the teeth, under certain conditions, the top of the tool cuts too much in the roots of the wheel teeth and cuts the root of the tooth too much.
Fan cheng
The Fan Cheng method (or exposure method) is a method of processing equipment using the geometric packaging principle. After giving the two gear gradients and the active wheel angle speed W1, the angle speed W2 of the mobile wheels can be obtained by the mesh of the two dental profiles, and the i12 = W1 / W2 = a value fixed can be obtained. Because in the mesh of the two teeth, the two laps are made of pure rolling during the pure rolling process of Tour 1 of the Tour 2, the contour of the tooth of the equipment 1 will occupy a series of relative positions and this series of Relative the positions will be in the relative position.
Cut
Recovery reasons: when the intersection of the upper line of the knife tooth and the mesh line exceeds the N1 mesh limit point, and the tool continues to move from the ⅱ position, cut the root of the root and cut part of the dental profile.
The consequences of cutting the roots: the equipment of the severe root cuts is generated, which weakens the flexion resistance of the wheel teeth on the one hand; transmission. Recovery reasons: when the intersection of the upper line of the knife tooth and the mesh line exceeds the N1 mesh limit point, and the tool continues to move from the ⅱ position, cut the root of the root and cut part of the dental profile.
For non -standard gears, the number of teeth is less than 17.
Daguang focuses on providing solutions such as precision CNC machining services (3-axis, 4-axis, 5-axis machining), CNC milling, 3D printing and rapid prototyping services.
