Such a section in mechanics as machine parts is passed by all students of technical specialties. The main points are focused on the gears, which are of several types. Spur gears, helical gears, as well as chevron gears - they are all used in almost all industries.
What functions does gearing perform?
Before talking about what a cylindrical chevron transmission is, it is necessary to understand the general provisions. Gearing is used to transmit rotational motion between shafts. So in direct contact is a pair of gear teeth and wheels. The gear ratio varies depending on the size of the gear and the number of teeth on it.
Changing angular velocities and moments are the main functions of any gear transmission, including a chevron one. Widespread use in various industries requires constant development and improvement of transmission technical characteristics. As a result, new types of gearing appear, high-strength tooth alloys, etc. are used.
Chevron gears and everything about them
As we have already figured out, this type of gearing refers to gears. Let's define a little with the design features of this transmission. From the classic gear, we have significant differences. Firstly, the crown consists of teeth pointing in different directions. Accordingly, on one side of the crown, they have a slope in one, from the opposite - in the other direction.
We can safely say that chevron gears have a huge number of advantages. For example, the absence of axial load on the bearing, which allows to extend the service life of the node. In addition, this type of gear allows you to significantly increase the angle of inclination of the teeth, which is approximately equal to 25-40 degrees. While in a regular helical wheel, the limit is 18 degrees.
Of course, there are some nuances. Firstly, the high complexity and high cost of manufacturing a chevron. Since this type of gearing is used to transmit high power and speed in the absence of axial loads, the manufacturing accuracy must be very high, and therefore 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 gear.
Chevron Wheel Benefits
It should be noted that all mechanical gears have common advantages and disadvantages. This also applies to chevron gearing. Consider the strengths. Firstly, high smoothness, which is achieved due to the large angle of inclination of the teeth. Consequently, the dimensions will be much smaller compared to the helical gear. This allows you to slightly reduce the weight of the product, as well as the size of the node as a whole.
Durability in compliance with operating standards (regular lubrication, rejection, absence of overheating and mechanical damage) is about 40,000 hours. Accordingly, the reliability of this node will be very high. This is also due to the lack of axial loads on the bearing. As a result, there is no overheating of the shaft and bearings.
High efficiency (97-98%) is another strength of chevron wheels. This indicator is often a determining factor when choosing the type of transmission in a particular node, as it allows to achieve minimal losses during operation. The constant gear ratio is also an important factor, which, although not highlighted, still takes place. Such advantages of chevron transmission play an important role when operating in heavily loaded machine components.
A bit about the flaws
Like any other type of gear, this one has several disadvantages. First of all, as noted above, the complexity of manufacturing. The cost of a chevron wheel is quite high, although it is durable. Often in production, when a node fails, it is important to replace it as soon as possible. In this case, helical and spur wheels, which are easy to manufacture, are perfect. As for the chevron, then not everything is so simple. The mounting accuracy should also be high, therefore, the amount of time spent on installing the part increases.
Noise during work - is it so important?
Another disadvantage is the noise at high speeds. Although attributing it exclusively to the chevron transmission would be foolish, because this applies to the entire section. A pair of metal teeth engaged at high speed is always a loud noise, which, although suppressed with the help of special grease and casings, is not completely. It was also said about the floating shaft, which is necessary for the correct operation of the unit, and this increases the complexity of the design. The manufacture of a chevron transmission is carefully monitored at all stages, so there are few defective products, although a few years ago the situation was more sad.
About tooth profile
As with all gears, one or another type of tooth can be used in the chevron. A preliminary calculation of the chevron transmission is carried out. The following tooth types are used:
- screw one direction;
- screw different directions;
- involute;
- non-involute.
The applicability of one type or another depends directly on what needs to be achieved during operation of the unit. For example, if the site is designed to shift the center of the profile, an involute tooth is used. In addition, there are three options for the location of the gear to the wheel: close, extended and normal. By changing the distance to the center of the profile, you can achieve one or another position, which is necessary to increase smoothness, increase speed, etc.
It is also worthwhile to pay special attention to the fact that an incorrectly selected tooth type in one case or another will lead to such consequences as: a decrease in the resource of the unit, increased noise, overheating of the bearing, etc. Therefore, the most crucial step is precisely the theoretical calculation of the transmission.
Chevron wheels spread
As noted above, mechanical gears are used in many industries. Having considered chevron gears, the advantages and disadvantages of which clearly demonstrate their expediency, we can say about uniqueness. Nevertheless, the commissioning of chevrons everywhere cannot be called expedient, due to the high cost and complexity of the design.
But despite this, one cannot do without them at metallurgical enterprises. There, chevron transmission is used on rolling mills, cutting machines and other equipment. This is due to the fact that the chevron wheel can be:
- low-speed;
- medium speed
- high-speed;
- high-speed.
The type of work depends on the peripheral speed. Most often, chevron transmission is used at high peripheral speeds (more than 30 m / s). The automotive industry is another industry where it is quite difficult to manage without using this mechanical transmission. The same applies to the chemical as well as the food industry.
Production material
Almost all gears undergo intensive wear. For this reason, it is necessary to use high-strength alloys that would cope with work in difficult conditions. The chevron wheel or gear itself is made of steel, but the teeth should preferably be bronze. But if you use bronze in its pure form, then it is too expensive. For this simple reason, the teeth are smelted from high alloy steel with bronze spraying.
It often happens that the assembly undergoes premature wear. This happens for various reasons:
- beating in transmission;
- overheating of the wheel and gear;
- insufficient lubrication.
In most such cases, it is not replaced with a new one, but is repaired by welding teeth. This method is used in almost all mechanical gears, if possible and appropriate.
To summarize
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, overheating of the unit is excluded, which is the most common cause of the failure of the latter.
At the same time, the high costs of manufacturing a chevron wheel and gears do not allow the use of this unit everywhere. The same applies to the time for the installation of a chevron transmission, as well as the highly qualified specialists involved in the installation and commissioning of the unit.