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Chevron transmission: advantages and disadvantages

Such a section in mechanics, like machine parts, is passed by all students of technical specialties. The main points are focused on gears, which are of several types. Straight, toothed, and chevron transfer - all of them are used practically in all industries.

What functions does the gearing

Before talking about what a cylindrical chevron transmission, you need to understand the general provisions. Gear engagement is used to transfer rotational motion between shafts. So a pair of gear teeth and wheels are in direct contact. The gear ratio varies depending on the size of the gear and the number of teeth on it.

The change in angular velocities and moments is the main function of any gear transmission, including chevron. A wide application in various industries requires constant development and improvement of technical characteristics of transmission. As a result, new types of gears appear, high-strength tooth alloys are used, etc.

Chevron gears and everything about them

As we have already figured out, this kind of engagement refers to the jagged. Let's define a little with the design features of this transmission. From the classical dentate we have significant differences. First, the crown consists of teeth directed in different directions. Accordingly, on one side of the crown, they have a slope to one, from the opposite side to the other.

We can safely say that chevron transfers have a huge number of advantages. For example, the absence of axial load on the bearing, which allows to extend the life of the unit. In addition, this type of transmission can significantly increase the angle of inclination of the teeth, which is approximately equal to 25-40 degrees. While in the usual helical wheel the limit is 18 degrees.

Of course, there are some nuances. First, the high complexity and high cost of making chevrons. Since this type of engagement is used to transfer high power and speed in the absence of axial loads, the manufacturing accuracy must be very high, and hence the cost of such a wheel is high. Secondly, the need to use a floating shaft in the structure. For this simple reason, engineers try to use helical gear, where possible, and only then use chevron.

Advantages of the chevron wheel

It should be noted that all mechanical transmissions have common advantages and disadvantages. This also applies to the chevron engagement. Consider the strengths. Firstly, high smoothness of the stroke, which is achieved due to the large angle of inclination of the teeth. Consequently, the dimensions will be much smaller than the helical wheel. This allows you to slightly reduce the weight of the product, as well as the size of the unit as a whole.

Durability at observance of norms of operation (regular greasing, culling, absence of an overheat and mechanical damages) makes an order of 40 000 hours. Accordingly, the reliability of this node will be very high. This is due to the lack of axial loads on the bearing. As a consequence, there is no overheating of the shaft and support.

High efficiency (97-98%) is another strong point of chevron wheels. This indicator is often the determining factor when choosing the type of transmission in a particular node, since it allows to achieve minimum losses during operation. The constant gear ratio is also an important factor, although it does not come to the fore, but still takes place. Such advantages of chevron transfer play an important role in the operation in heavy-loaded machine nodes.

A little about the shortcomings

Like any other type of gear, this one has several drawbacks. First of all, as noted above, the complexity of manufacturing. The cost of the chevron wheel is quite high, although it is durable. Often in the production of a failure of any node, it is important to replace it as soon as possible. In this case, helical and straight-toothed wheels that are easy to manufacture are excellent. As for the chevron, then everything is not so simple. The accuracy of the installation should also be high, hence the amount of time spent on the installation of the part increases.

Noise at work - is it important?

Another drawback - noise at high speeds. Although it would be foolish to attribute it exclusively to the chevron transmission, it's the whole section. A pair of metal teeth engaging at high speed is always a sonorous noise, which, though it is silenced with a special lubricant and covers, but not completely. It was also said about the floating shaft, which is necessary for the correct operation of the node, and this increases the complexity of the structure. Chevron transmission is carefully controlled at all stages, so there are few defective products, although a few years ago the situation was more sad.

About the tooth profile

As in all gearing, a chevron can use one or another type of tooth. Chevron transmission is calculated in advance. The following types of teeth are used:

  • Screw one direction;
  • Screw in different directions;
  • Involuntary;
  • Non-involuntary.

Applicability of a particular type depends directly on what needs to be achieved during the operation of the node. For example, if a node is designed to shift the center of the profile, use an involute tooth. In addition, there are three variants of pinion to wheel position: close, extended and normal. Changing the distance to the center of the profile, you can achieve this or that position, which is necessary to increase the smoothness, increase the speed, etc.

It is also worthwhile to focus on the fact that the incorrectly selected type of tooth in one way or another will lead to such consequences as: a decrease in the node's resource, increased noise, overheating of the bearing, and so on. Therefore, the most important stage is the theoretical calculation of the transmission.

Distribution of chevron wheels

As already noted above, mechanical transmission is used in many industries. Having considered the chevron transmissions, the advantages and disadvantages of which visually demonstrate their feasibility, one can say about uniqueness. Nevertheless, the commissioning of chevrons everywhere can not be called appropriate, which is due to the high cost and complexity of the design.

But despite this, one can not do without them at metallurgical enterprises. There chevron transfer is used on rolling mills, cutting machines and other equipment. The reason is that the chevron wheel can be:

  • Slow moving;
  • Medium speed;
  • High-speed;
  • High-speed.

The type of work depends on the circumferential speed. Chevron transmission is most often used at high circumferential speeds (more than 30 m / s). The automotive industry is another industry where it is rather difficult to do without using this mechanical transmission. The same applies to the chemical, as well as the food industry.

Material of manufacture

Virtually all gear drives are subject to heavy wear and tear. For this reason, it is necessary to use high-strength alloys, which would cope with work in difficult conditions. Directly the chevron wheel or pinion is made of steel, but the teeth should preferably be bronze. But if you use bronze in its pure form, it's too expensive. For this simple reason, the teeth are made of high-alloy steel with bronze spraying.

It often happens that the unit is exposed to premature wear. This happens for various reasons:

  • Beating in gear;
  • Overheating of the wheel and gear;
  • Insufficient amount of lubricant.

In most such cases, it is not changed to a new one, but is repaired by fusing the teeth. This method is used in almost all mechanical transmissions, if possible and appropriate.

Let's sum up the results

The main advantage of chevron transmission is the possibility of its use at high speeds. An important role is played by the fact that there is no axial load on the bearing. Accordingly, the node overheating is excluded, which is the most common cause of the last failure.

At the same time, the high costs of manufacturing the chevron wheel and gears do not allow the use of this node everywhere. The same applies to the time to install the chevron transmission, as well as the high qualification of specialists involved in the installation and commissioning of the unit.

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