hypoid oil. Application conditions.
Hypoid is the transmission of torque by means of the meshing of two gears that have an oblique or curved tooth shape. Such gears successfully solve the problem of increased transmission noise and can work for a long service life, provided that a special oil for hypoid gears is used to lubricate the working surfaces of the teeth.
The area of engagement between the teeth of the gears of a hypoid gear is limited by the minimum contact patch. But at the same time, all the effort is concentrated at one point, which leads to a significant increase in the specific pressure in this place. As a result, seizures may appear, creating a danger of destruction of the gears. To prevent this from happening, oils are used that make it possible to maintain a strong film at the point of contact of the teeth, thanks to which the gears contact each other with minimal friction.
Overview of oils for hypoid gearboxes
Hypoid gears are used today in the main gears and gearboxes of most modern cars. Many motorists know TAD-17 oil, which is widely used for transmissions of domestic cars. But with the advent of foreign cars in the expanses of the post-Soviet states, the range of transmission lubricating fluids began to expand.
The main characteristic of oils is viscosity. Currently, domestic manufacturers have switched to the SAE classification, which is used throughout the world. It provides for seven viscosity classes: 4 winter and 3 summer. Winter classes are additionally designated with the letter W (SAE70W, SAE75W, SAE80W, SAE85W). No letter is added to summer classes (SAE90, SAE140, SAE250). However, in most cases, seasonal oils do not have time to develop their resource, and their use is unprofitable. Therefore, all-weather materials, in the designation of which there is a double marking, have become more widespread, for example SAE80W-90.
In addition to the viscosity class, oils are divided according to API performance into 6 classes: GL-1, GL-2, GL-3, GL-4, GL-5, GL-6. The higher the API grade, the more additives the oil contains to help hypoid gears work. For hypoid gears of passenger cars, only lubricants of the GL-4, GL-5, GL-6 class can be used.
What criteria should a good oil meet?
It is impossible to answer this question unambiguously. A good oil is one that meets the operating conditions of a particular unit. The selection criteria are determined by the manufacturer. There are many brands of cars in the world. Even more modifications. Each has its own design features and requires the use of a lubricant of a certain class. The hypoid gear of one car in its design and working conditions can differ significantly from the working pair of another car similar in purpose. Many factors come into play here, such as torque, rotational speed, axle offset, impact load, etc. And if GL-4 oil is the best option for one gear, then it may be completely unsuitable for another. Therefore, to ensure the trouble-free operation of the car, you must strictly follow the manufacturer's instructions.
A hypoid gear (gear) transmission differs from a conventional one, with straight or oblique teeth, in that its teeth are curved. They are curved along a special geometric curve - a hyperboloid, as can be seen in the figure. Hence the name: hypoid - short for.
There are two main features of the hypoid gear. Firstly, it can only be used in nodes with intersecting gear axes. It makes no sense to try to build a hypoid gear with parallel shafts: it will immediately jam.
Secondly, the axes of the shafts must be additionally offset relative to each other, otherwise jamming again. The amount of displacement must be exactly matched to the mathematical parameters of the hypoid, this is the so-called hypoid displacement.
Benefits of a hypoid gear
For the first time in the automotive industry, the engineers of the American company Packard used the hypoid main gear in 1926. What did it give?
The main gear transmits torque from the propeller shaft to the drive wheel differential. It is always performed by lowering in order to coordinate the engine speed with those necessary for the wheels and at the same time increase the torque on them.
First, the driveshaft has moved down by the amount of hypoid displacement. This made it possible to reduce the height of its tunnel in the cabin and at the same time lower the center of gravity of the car, thereby improving its stability.
Second, the hypoid gear transmits the moment more smoothly than the helical gear, not to mention. Finally, a hypoid gear is less noisy and can transmit more torque than a regular gear. As the engineers say, it has a large load capacity.
All this, taken together, increases both the comfort of the car and its durability. Therefore, the hypoid main gear is an indispensable attribute of cars of a fairly high class, such as, for example, the Lexus Infiniti.
Her flaws
However, the hypoid gear also has significant drawbacks, in addition to the complexity of manufacturing and, accordingly, the high cost. When the gears rotate, due to the fact that the teeth are bent, a force acting along the axis of the small drive gear occurs. As a result, the hypoid gear is very sensitive to wear, the quality of workmanship not only of gears, but also of all its parts, especially bearings. With its inaccurate adjustment, it easily jams, especially when changing the direction of rotation, when reverse gear is engaged.
Every cloud has a silver lining: the tendency of the hypoid gear to jam is used in the central (interaxle) self-locking differentials of the Thorsen type. They are used in vehicles with full automatic drive (4WD).
The teeth of a hypoid gear fit more closely together than a conventional gear, so it is also very contaminant in the oil. The oil in the crankcase of the hypoid gear should only be filled with special hypoid oil, with antiwear and extreme pressure additives. And you need to fill in a strictly defined amount.
Application of hypoid gear at present
However, all the shortcomings of the "hypoid" are more than compensated by its advantages, and technologically they are quite surmountable. With the development of the automotive industry and the general culture of production, the hypoid also moved into the transmission of consumer class cars. Now it can already be seen in budget Chinese cars.
Today, the hypoid gear is widely used. It is equipped with cars, tractors, diesel locomotives, machine tools for light and heavy industry.
Did you know?A passenger car was equipped with a hypoid gear in 1926 by the American company Packard.
What is a hypoid gear and its purpose in a car
A hypoid gear is a helical gear driven by crossed bevel gears. In a car, it is needed to change the direction of the torque and change its magnitude, which improves the performance of the final drive. With the development of the automotive industry, the type of hypoid gears is gaining great popularity and is used not only in executive class cars, but also in budget cars. In any case, these are machines with rear-wheel drive, where the engine and final drive are parallel to the movement, and torque is transmitted to the drive axle at a right angle. 
How does a hypoid gear reducer work?
Let's figure out how the hypoid gear works and what it gives in the operation of the machine. In this transmission, the moment of force is transmitted from the engine through the clutch, gearbox and universal joint to the axis of the hypoid drive gear transmission. The axis of the drive gear is installed parallel to the axes of the input shaft of the engine and the secondary shaft of the gearbox. Due to the curved shape of the teeth of the gears of this gear, the transmitted moment of force is of greater importance than, for example, in a bevel gear. This improves the dynamic and mechanical performance of the machine.
Important!In hypoid gears, for the lubrication of its elements, special fluids are used that have high quality and properties (antiwear and extreme pressure additives) that enable long-term trouble-free operation.
Benefits of using a hypoid gear in a car
The first advantage is the location of the cardan shaft. It lowered significantly, which reduced the size of its channel in the cabin, evenly distributed the car's center of gravity and increased its stability. Secondly, the smooth transmission of torque, which improved the driving characteristics of the car.
No less significant fact is less load and noise level. These indicators are due to the fact that a larger number of teeth participate in the hypoid type of engagement, in comparison with the same bevel gear.
All these factors increase the durability of the machine, not to mention the comfort of movement. Therefore, the hypoid type of transmission is an integral part of high-class cars such as Infiniti.
Interesting! The decision to launch a new class of prestige vehicles in the company "Nissanwas adopted in 1985. The car was namedInfiniti”, in translation - infinity, infinity.
Hypoid gear in a car: are there any disadvantages
TO shortcomings Hypoid transmission refers to the possibility of seizing along the contact line due to friction. To reduce such probabilities, the final drive gears undergo special processing during the manufacturing process.
In addition to the difficulty in manufacturing, there is an effort when the gears rotate in the way that their teeth are curved, this force is transmitted to the axis. These moments make the hypoid gear susceptible to wear.
This transmission is demanding on the quality of not only gears, but also of its other elements. If it is carelessly adjusted, it jams, especially when changing the direction of rotation or engaging reverse gear.
Attention! If you are stuck on a country road, for example, in a rut, you need to pull out a sat down car only in forward gear, otherwise the gear teeth may break.
A lot of motorists are interested in the question: what is hypoid oil, how does it differ from ordinary transmission oil? If you look at the hypoid composition, you can find a mixture of used and substandard oil, which is suitable for steering gearboxes, as well as some transmission units.
To improve the quality of such lubricants, a slight modification is carried out. Special additives are added to the composition, thanks to which the hypoid grease receives excellent extreme pressure characteristics.
These transmission fluids are classified as GL-5. They can be used in the transmission of vehicles equipped with drive axles with hypoid gears. Such lubricating mixtures are widely used in helicopter gearboxes and car cardan shafts.
Characteristics
In order for the hypoid mechanisms to work properly, they must be lubricated with a component that contains approximately 4% sulfur. It protects metals from seizing, but at the same time leads to rapid oxidation. To neutralize this process, unique additives are added.
MOLYVAN L improves the protective properties of the lubricant when parts are subjected to increased contact loads. This property of the additive made it possible to use it in gearboxes equipped with hypoid gears as protection against increased wear. In transmission fluids, the concentration of this additive sometimes exceeds 5%. The grease does not freeze at a temperature of minus 30.
Time does not stand still. Today, many new modifications of oils have appeared for working in high-speed hypoid mechanisms. Additive VIR-1 contains both phosphorus and sulfur. This allows you to add it to a variety of types of gear oils. Tests have shown that it improves the quality of lubricant mixtures designed to improve the operation of hyperboloid gears.
All vehicles with hypoid gearboxes usually use an all-weather lube that performs well in moderate climates. Hypoid motor oils help to reduce wear on the surface of the part. In principle, their properties are not much different from the characteristics of conventional transmission, the only difference is the viscosity coefficient.
What oils can be used in hypoid gears
In modern cars, gearboxes with hyperboloid gears are required. Almost all car owners are familiar with TAD-17 lubricant. It is constantly poured into the transmission of domestic cars. After the appearance of foreign cars in Russia, the list of transmission fluids began to increase rapidly.
The main characteristic of such motor oils was their viscosity. Today, domestic manufacturers of consumables have begun to use the SAE classification used in the modern world. It includes several viscosity groups:
- Summer - 3.
- Winter - 4.
To distinguish winter oils from summer oils, the letter W is added to their name, for example:
- SAE70W,
- SAE75W,
- SAE80W.
This letter is absent in the compositions for the summer period: SAE90, SAE140, SAE250. Seasonal options are designed for long-term use, but at the end of a certain period they have to be changed, although the resource has not been completely exhausted. Therefore, their use is considered unprofitable. Today, all-weather ones have become more popular, the designation of which has a double marking - SAE80W-90.
According to the API standard, gear oils are divided into classes depending on their performance (GL 1-6). The amount of additives contained in them, which improve the operation of the gearbox, depends on the value of the figure.
For passenger cars equipped with a hyperboloid screw gear, transmission oils GL-4/5/6 are used.
In order for your car to drive, it is not enough to fill in gasoline and press the gas pedal, it is important to constantly monitor the health of all the organs of the “iron horse”. After all, a machine is a complex mechanism in which only the correct interaction of all the cogs and "gears" forms a single whole, which will work like a clock.
One of such important components of the smooth operation of the automotive body is a hypoid gear, similar to the type of gear used. There are two more types of gears: bevel and cylindrical. We will focus on the hypoid gear.
First, let's deal with the name. Why hypoid? It's short for hyperboloid. The fact is that the teeth of such a transmission are curvilinear and move along a geometric figure - a hyperboloid.
The hypoid gear was invented almost 90 years ago - in 1926. Its main task was to reduce the center of mass in passenger cars. Later, having found out that this type of transmission has many more advantages, they began to use it on trucks, such as - 133 G and ZIL - 433100 (instead of a double gear).
How does a hypoid gear differ from the other two types?
Main. Pay attention to two points: the shaft axes must be shifted in accordance with special mathematical calculations, plus a hypoid gear can only be used in nodes in which the gear axes intersect. If these two rules are not followed, the transmission will immediately jam.
Benefits of a hypoid gear
What are its advantages compared to the other two types of transmissions? Among the main masters, its almost silent operation is distinguished (due to the fact that several teeth are simultaneously engaged) and greater strength (the average diameter of the gear is increased) compared to the canonical gear.
This is achieved due to the arrangement of gears: not intersecting, but crossing. In addition, the load experienced by one tooth is reduced, thanks to which the operation of all gears is more reliable and durable.
Cars in which a hypoid gear is used are distinguished, among other things, by stability and smoothness. These characteristics for motorists play an almost paramount role when choosing an “iron horse”, and are always under special control of automobile concerns, which are constantly improving in the direction of improving not only the “brain” of the car, but also driving comfort.
Therefore, you can most often observe a hypoid gear in executive cars. Such as Infiniti, Lexus, etc. Moreover, the teeth of the hypoid gear are more resistant to fatigue when compared with the bevel gear. But where there are pluses, there are also minuses.
Flaws
Let's look at the disadvantages of using such a gear in a gearbox. The disadvantages of using a hypoid gear can be written down, firstly, its high cost. The reason here is that it is not so easy to make it. However, the hypoid gear is already being actively introduced even in budget cars from the Middle Kingdom, so there is still a moot point about the high cost. Another of the minuses is a high probability of seizing gears. This is possible due to sliding along the line of contact.
The cause of the seizure, of course, is treated. Drivers are advised to use only gear oils, which, as it were, envelop the gears with a special film and prevent jamming. Improper adjustment and poor quality of “consumables” can lead to jamming. It is interesting that the developers of all-wheel drive cars turned this disadvantage of this type of transmission into a virtue and successfully use it.
Plus, the hypoid gear is famous for the fact that it quickly becomes unusable. Coupled with the relative high cost, this can often be a deciding factor for auto manufacturers. And hypoid gear they prefer cheaper options.
And yet, if you are lucky enough to become the owner of a car with a hypoid gear, know that you have acquired a reliable “horse” that, with proper care and periodic monitoring, will work for your joy.
In general, smooth roads to you!
