The scope of the variator in technology is large, it is also used to optimize the mode of movement of the car. This is a device that changes the gear ratio from the engine to the transmission.
In the automotive industry, it can be used to effectively select the gear ratio (engine-transmission). How to repair a variator with your own hands, its advantages and disadvantages are revealed in this article.
CVT, its application, positive factors
Cars produced with a variator, are economical, since the engine runs almost constantly in optimal mode, fewer toxic gases are emitted into the air, better acceleration of the car.
It is provided with a smooth gear ratio and a smooth set of auto travel, no jerks. Transmission units last longer than in a manual gearbox. When comparing a variator with an automatic transmission, their design is simpler, which allows you to do repairs yourself.
Despite all the positive qualities, this device is not an ideal gearbox, the reason for this is its frictional work. This is when the torque is transmitted by friction, and has limits, if they are exceeded, the belt will begin to slip, with a high wear rate.
It is undesirable to often use a variator on a car at maximum loads, you should not use a “sports” driving mode on these cars, with frequent jerks, braking. Its ideal and long-term operation is when the car is operated in a calm driving, smoothly.
How the variator works
Used on modern cars two types of variators:
- V-belt transmission.
- Torah transfer.
The V-belt transmission consists of 2 pulleys, between which a specially made belt is stretched. The first pulley is connected to the engine of the car (driver), the second pulley (driven) is connected to the driving wheels of the car. Sliding pulleys are used, they consist of 2 halves, when they approach, the belt is pushed out, and when they move apart, it fails. There is a synchronous change in the radii of rotation, with an increase on one pulley, a decrease is made on the other pulley. This achieves gear ratio smoothness.
When the radius of the drive pulley is smaller and the driven pulley is larger, it is a downshift. If the belt rotates along a large radius on the drive pulley and a small one on the driven pulley, this is an overdrive.
Despite its simplicity, the use of the variator in cars began recently, this was facilitated by the invention of a special belt. A simple belt is not suitable for these purposes.
V-belt drive
V-belt drive belt made from 2 metal strips, on which plates are strung, made of metal having a special shape. When the belt links are pressed against each other, there is a transfer of force by pushing their drive pulley.
Important! The drive pulley, connected to the engine, pushes the metal belt links sandwiched between its disks, and they push the adjacent links to the driven pulley. This belt is pushing, which thus allowed to transfer large forces and apply it on cars.
In some technical self-propelled machines chain drive is used instead of a V-belt, there are no differences in the principle of operation, except for one, the chain transmits pulling force and power through the ends of the axes of the chain links, made in a beveled form.
Torah variators
For greater torque transmission, torus variators are used, compared to V-belt drives. For them, the shortcomings that exist in V-belt transmissions remain, the force in both one and second gear occurs with the help of friction.
The cost of a torus variator is higher than that of a V-belt, this is due to the details of its design, made of high-strength steel, and it is used in its maintenance special friction lubricant.
For a better understanding of the issue, let's look at what it consists of practical variator design:
From the above material, it can be seen that the variator can be considered as a type of automatic transmission and it's not easy to fix it yourself, for this you need to have the skills and know its design:
- The clutch function on a car with a CVT is performed by a clutch package; a torque converter can be used instead. Clutches are easier to use, they are smaller in size, but the torque converter has a better smooth shifting, it is operated longer, its parameters are better at the moment of acceleration of the car.
- The planetary gear drives the vehicle backwards.
- The control system includes: control unit, hydraulic pulley interaction system, sensors. It works on the principle of collecting data (engine speed, what is the speed of the car, in what position is the “gas” pedal) and determining the best gear ratio for them.
- The hydraulic pump provides the necessary pressure in the hydraulic system, as well as lubrication of the variator design elements. The system maintains pressure proportional to the torque, when it is greater, the discs are compressed more strongly, the belts do not slip.
On the example of an automatic transmission of a Nissan car, you can consider in more detail the repair of the variator with your own hands. The problem arises when the car is moving at a speed of 50-60 km / h, the variator starts to make an unpleasant noise, this is a common disease for this brand of car.
Tools needed to repair the variator:
- Impact screwdriver, not electric, powerful.
- Clamps 6 pieces.
- Hammer.
- A set of keys 10-14.
- Prepare a container for small spare parts.
In the process of disassembling the variator, we place all the parts on the working surface in the sequence of their removal, this will help when assembling the device.
Actions in order:
- We unscrew the bolts from the cover of the dispenser, there are 6 of them.
- Use a screwdriver to hook on the edges of the dispenser and remove it.
- We see a tapered bearing, which must be removed and placed in a container in which there are already 6 bolts.
- Let's turn the variator over.
- We take out in this position part of its body and shaft.
- To remove the cover, we tap it with a hammer, remove the cover, this is 50% of the work.
- The gears open, remove them, put them in another container.
- We unscrew the available screws of the pump, remove the gear with the pump chain.
- Access to the oil pump has been opened. We remove it carefully, by the tip of the shaft in an upward movement, the pump moves away.
- The shaft is removed. On the other side of the box everything is removed.
- Turn the variator over again and remove the cover with a screwdriver.
- Access to the variator nodes is opened, these are two shafts and a belt. The nodes are visually inspected from all sides in good light.
- You can tighten the belts with clamps, then remove the pulleys with the belt from the variator housing.
- On the working surface, remove the pulleys from the belt. The bearing opens, if you pull on its ring, you can feel an uneven play, which is the cause of the noise.
- Replace bearing and reassemble in reverse order.
Thus, with his own hands was eliminated noise in automatic transmission, it should be noted that all components are washed with gasoline during disassembly, and when elements that require special lubrication are assembled, they must be lubricated.
The use of a variator in machine tools
Machine equipment is equipped with a variator in cases where it is necessary to change the speed of rotation of the workpiece. In industrial versions of lathes several pulleys are provided, and rearranging the belt between them, this is inconvenient, such an operation requires stopping the machine equipment.
An alternative for the operation of machine tools is a home-made variator for the machine. Its disadvantage is belt slippage, but this also protects the engine when a workpiece wedge occurs. Experts, having examined a home-made variator, came to the conclusion that with the existing shortcomings, it increases work productivity, it is not necessary to turn off the machine, and the speed is smoothly regulated.
Consider what the machine variator consists of, and how you can make it yourself when you have a lathe at home.
Necessary operations:
- We make cones, you can use hardwood. They are cut with an electric jigsaw, with an angle of inclination equal to the angle of the cone.
- Wooden cones must be planted on metal rods as deep as possible to fix them with screws.
- With the help of rollers, a guide is made, which allows the belt to move along the cones and fix at the desired speed. If there are no rollers, bearings of the correct size are used for this operation.
- With the help of a threaded rod and a rotating screw, the guide moves along the cones.
The best model can be assembled using round belts. At home, for your own lathe, such a variator helps a lot in your work.
The CVT transmission is gaining more and more these days, and there is a fairly simple explanation for this. First of all, this is the simplicity of the design. But, nevertheless, the service and repair of the variator requires certain knowledge and skills. The gearbox consists of various components and systems that, if used improperly, can fail and it will be difficult to repair them.
Many variator malfunctions are the result of non-compliance with the basic rules of operation and maintenance:
- non-compliance with the timing of fluid replacement;
- non-compliance with the terms of filter replacement;
- the use of low quality lubricants;
- driving mistakes;
- driving at top speed;
- frequent sudden braking;
- driving on bad roads.
To avoid many troubles with the variator box and then not repair, follow these simple maintenance rules:
- every thirty thousand km. mileage change oil;
- change the filter elements in time;
- after seventy thousand km. mileage, change the stepper motor and shaft sensors.
Do not forget that the diagnosis of the variator is much cheaper than repairs, even with your own hands, even at the service station.
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CVT diagnostics
In the event of a malfunction concerning the electronic part, the message “Service required” will light up on the display located on the dashboard.
If the temperature of the liquid rises above the norm, it will light up - Slow down.
In order to accurately establish the breakdown and fix it with your own hands, you need special diagnostics carried out using special equipment. For many breakdowns, a special code is provided, according to which the following are installed:
- sensor malfunctions (temperature, pulley speed, pressure, line, pulley pressure);
- ECU malfunctions;
- malfunctions of the stepper motor, valves, line;
- decrease or increase in pressure in the pulley.
When you carry out diagnostics, do not forget that the probable cause of the problem may be not only the breakdown of some node. Often, wiring or defects in a connector can be damaged. Also, the problem may be a malfunction of the gearbox control unit.
In some situations, when malfunctions are detected, the gear control system can be automatically transferred to a special mode. This mode differs from the usual one by a special fixed gear ratio.
Malfunctions of the mechanical part of the boxes cannot be established only with the help of electronic diagnostics. In this situation, there is a need for a whole range of measures:
- it is necessary to check the state of the working fluid;
- identify all symptoms of a malfunction;
- analysis of all ECU data;
- road testing.
CVT repair
In the operation of variator boxes, failures and breakdowns of a different plan sometimes occur. Very often there are noises and squeaks of various types. In this case, it may be necessary to disassemble the gearbox. This process is not so complicated and with a detailed study of the material, you can handle it yourself.
Tools
- a set of keys;
- Screwdriver Set;
- ordinary hammer;
- clamps;
- containers for parts;
- large desktop.
Stages
Before proceeding with disassembly, it is worthwhile to prepare in advance special containers for the parts to be removed. To make it easier to assemble later, arrange the containers in the order of disassembly. If you are doing this work for the first time and are not sure that you can remember the disassembly order, then this whole process can be captured on the camera. Parts can also be marked.
It is better to repair in a well-lit and ventilated area.
Now that the variator has been disassembled, it is necessary to check all its components and systems. Pay special attention to the condition of the bearings, pay attention to whether the play is increased. Look at the condition of the belt and see if its tension has loosened. Inspect the gears, hydraulic block and other parts for defects. The most common problem that results in noise in the variator box is high bearing wear. In this case, nothing will help, except for replacement, you can do it yourself.
It is very important to identify the malfunction in the variator box in time and fix it. This will avoid more serious breakdowns, which will be quite difficult to repair, and it costs much less.
Video "Repair of CVTs"
In this video, the automaster will tell in detail and show how you can repair CVT gearboxes with your own hands. It costs much less than going to the service station.
I have a lot of articles about automatic transmissions (I especially love the regular automatic transmission). However, I consider the CVT or CVT to be the second most common, a lot of cars are produced with just such a transmission. When you choose a new car (or even a used one), you will definitely have such a choice what to take - a CVT transmission, a torque converter or a robotic one? If the usual “machine” has been studied “up and down” (if problems arise, then they are all known), everything is clear with the robot (yet you should not look in his direction). Then the third type seems to be reliable, but few people know what it is, what is the principle of its operation, the main pros and cons. That is, it is such a "dark horse". Today I will try to reveal the topic in simple language, tell you what to be afraid of and what not ...
The problems of this automatic transmission are very similar to the usual "torque converter" despite the difference in designs (we already have them). In the end, I will try to tell you in the video version how to extend its service life so that it runs for a long time and without problems. However, to begin with, the definition
Definition
CVT - CVT - CVT (Continuously Variable Transmission - continuously variable transmission) - a type of automatic transmission that smoothly transfers torque from the engine to the wheels (or other propellers, such as ship propellers), does not have gears, but can automatically change the gear ratio according to a given program or in manual mode.
It should be noted that this box, unlike its counterparts, automatic transmission and ROBOT, does not have variable gears, that is, there are no usual shocks when changing gear ratios, the speed set here is clear and even, the efficiency (according to the characteristics, not significantly but more), due to its structure
Principle of operation
As you understood from above, there are no gears here, and the change in gear ratio (increase or decrease) goes smoothly, to “set values”. Of course, there is a software component here that allows you to create "steps", but they are made programmatically, for manual control, for example, in mud or snow (when you need maximum traction and speed is not important). And the box itself is stepless - which allows you to transfer forces from the power unit to the wheels more accurately.
At the moment, there are two main structures of the variator:
- These are clinomeric . They are used on 95% of cars equipped with such a transmission.
- Toroid . Due to the more complex structure and settings, they are practically not used now.
Because clinomeric this is now the most common type (it is installed on a large number of NISSAN, AUDI, INFINITY, etc.) let's start with it
So, here the gear ratio is transmitted from one pulley ( leading - it is connected with the power unit), another ( slave - connected with the drives and further with the wheels) by means of a special belt.
The change in the number occurs due to a change in the diameter of the pulleys. They are not “cast”, but are made collapsible, namely from two halves of a conical shape (planted on a shaft), which can diverge and converge. As it becomes clear, the diameter at the point of contact between the pulley and the belt is constantly changing depending on the load and speed.
In simple words, everything happens like this: - when the car “starts”, it needs maximum effort to move. In order for the load on the motor to be minimal, the drive shaft must be of the smallest diameter (the cones are bred at the point of contact). The slave in its case should be of the maximum size (its cones, on the contrary, are reduced). Thus, the master must make several revolutions in order to shift the slave by only one (maximum number) - this greatly reduces the force on the power unit, and it is easier for him to work.
After the speed increases, the gear ratio should change down - this is necessary in order to reduce traction, but increase the speed on the driven shaft. The opposite happens - the cones of the driving pulley begin to converge (the diameter grows), and the driven pulley - to diverge (decreases).
With the maximum size of the drive shaft and the minimum size of the driven shaft, the first one will make one revolution, but the second one should make several (therefore, its rotation speed is maximum), but in this situation, the load on the motor is much greater.
As you understand, by changing the diameters of the two shafts and the belt drive between them, the desired gear ratio is achieved
Now a small animation, look
Toroid type variator has a completely different way of working. Here, the force is transmitted using special rollers that are sandwiched between the shafts, they have a toroidal shape (hence the name) and are located on the same axis
In order to change the gear ratio in such a design, you need to change the position of the rollers. For maximum traction, you need to turn the roller clamps towards the driven shaft, in this position the contact diameter of the roller and shaft will be minimal, and that of the driven shaft will be maximum.
When picking up speed, you need to decrease the number and increase rotation, the rollers are retracted to the other side (of the drive shaft), while the diameters change in the opposite direction.
I think this is understandable, will no longer focus on this.
Variator device
It makes sense to talk about the operation of the clinomeric CVT gearbox (because the colleague is now practically not for sale).
The box is mounted on the engine (either longitudinally or transversely). In order to smoothly connect it to the motor and turn it off at the right moments (neutral mode), a clutch system is provided.
Now many manufacturers have gone to a torque converter, a similar one is installed on a classic automatic transmission. However, other manufacturers may use other types - centrifugal, electromagnetic or multi-disc (wet versions). The use of a torque converter is due to high performance and high performance, including durability.
Now about the variator device itself. It is quite difficult to describe it, yet it is not a simple construction, but I will try:
- Shafts with variable cones. I will not talk about this again (the principle was told above). It should be noted that due to the large loads, the surfaces of the variator cones are made of high-strength steels.
- Belt or chain. Designed to connect two shafts. A belt can be called a stretch, all because it consists of special metal bands interconnected by special shaped parts that look like a butterfly and give a special wedge-like shape. He works with the side parts, which, due to the forces of friction, he contacts with the wedges of the pulleys. This transfers torque from one shaft to another. It is worth noting that other manufacturers, such as AUDI, use a chain mechanism, it has a large number of small links and provides small bending radii. It no longer works on the side surface, but on the end surface. Both the chain and the belt are designed for high loads, but they do not tolerate high overheating (they can be deformed)
- Oil. Yes, do not be surprised, the lubrication inside is also an important component and high demands are placed on it, usually it goes here , which is loaded into the machine. It is needed not only for lubrication, but also for pressurizing the pump in order to push or move the cones
- Oil pump. Just pressurizes the system.
- Hydroblock. He directs the supply of oil to the desired channels, that is, either into one cone (shaft) or another. By the way, slippage and other kicks, and jolts can be associated with it.
- Filter. There can be many of them, both in the valve body itself and outside it. They trap dirt and small metal particles from the belt and cones, preventing them from clogging fine channels.
- Radiator. On a CVT gearbox, it is MANDATORY! Remember, this transmission overheats very quickly during slippage and high loads, so an external radiator block is needed to cool the oil. Some on SUVs who like to climb in the mud and skid (for example, Mitsubishi Outlander) put additional radiators to remove excessive heat
- Well, and the last is the variator control unit. This is an electronic device that works in tandem with the computer, receiving the necessary commands from it. It instructs the electronics and shafts to adopt a particular configuration that corresponds to a given speed and load.
This device in a nutshell, in order to understand the general principle of operation. It is worth noting that initially the variator did not have reverse rotation, that is, backward movement. Therefore, a planetary gear was introduced into the design, which allows this to be done. However, this greatly complicated the design.
A few words about oil and filters
I can not keep silent and not speak about this point in more detail. The oil in the CVT is also a very important component in the operation of the entire device as a whole, just like the oil filter itself. Many manufacturers, official dealers can assure you that it is filled here for the entire service life. THIS IS EXTREMELY INCORRECT!
Oil and filter are consumables and many manufacturers say that you need to change them every 60,000 km, and in difficult conditions (which are our Russian realities - frost, snow, heat, rain, mud and traffic jams in megacities) it is worth changing even more often, Personally, I would advise after 40,000 km.
WHAT WILL HAPPEN IF YOU DO NOT CHANGE? The oil wears out and often burns (due to high mileage), forming deposits inside that can clog various channels and filters. The main filter can also become clogged with deposits, metal dust and other “work products”. As a result, the pressure drops from the oil pump to the valve body lines and the cones themselves, which are reduced on the shafts. The variator begins to slip, kick, or even enter emergency mode.
Today, the CVT transmission is very popular, which is primarily due to the simplicity of the design. However, in order to repair the variator, you must have some knowledge and skills. This is due to the fact that this device includes various systems and components, the misuse of which can lead to their failure. There are no big differences when repairing a Nissan, Honda, Mitsubishi or Tayota variator.
Most often, breakdowns of a continuously variable transmission occur as a result of non-compliance with the main rules of maintenance and operation:
- - Violation of the timing of updating the transmission;
- - Driving in bad road conditions;
- — Violation of the terms of filter change;
- — Frequent sharp braking;
- — Use of low-quality lubricants;
- — Riding at maximum speed;
- - Wrong driving.
In order to protect the CVT from possible malfunctions, the following maintenance should be observed:
- - Oil change every 30,000 - 40,000 km and;
- - Replacement of shaft sensors and stepper motor after 70,000 km of run;
- — Timely replacement of filter components.
Keep in mind that repairs are more expensive than diagnosing them.
CVT diagnostics
If a certain malfunction really happened to the electronic part, a notice should appear on the monitor located on the dashboard " Service required". On the same monitor, “Slow down” should be displayed if the temperature of the liquid has exceeded the norm. For self-diagnosis, you can use the program from Google Play CVTz50 and adapter ELM327
To accurately identify problems and fix them yourself, special diagnostics are required, which is performed using special equipment. Many faults have their own code, through which they are detected:
- — Malfunctions of sensors;
- — Reduced or increased pressure in the pulley;
- - ECU malfunctions;
- - Breakage of the stepper motor, line and valves.
When performing diagnostics, it should be remembered that the cause of a variator malfunction is not only a breakdown of a particular node. Often the cause of the failure of the CVT gearbox is damage to the wiring or some kind of connector. Or the cause may be a malfunction of the variator control unit.
There are also situations in which, in the event of a malfunction, the variator control system is automatically transferred to a special mode. The difference between the special mode and the usual mode is the presence of a fixed gear ratio.
If the failure of the CVT is concentrated in the mechanical part, then a number of measures will need to be taken to identify it:
- — Checking the condition of the oil;
- — Test while driving;
- — Establishment of signs of a problem;
- — Analysis of ECU data.
CVT repair
The normal functioning of the CVT can be disrupted as a result of various malfunctions and failures. Often there is a howl of the bearing, a creak and extraneous noise. As a rule, in such cases, disassembly of the variator is required.
Among the tools that are needed to disassemble a continuously variable gearbox are:
- - A set of keys;
- - Large desktop;
- - Screwdriver Set;
- - Containers in which the parts will lie;
- - Ordinary hammer;
- - Clamps.
Disassembly assembly variator
First, prepare containers for spare parts (you can place them in order of disassembly for convenience). To be sure to remember the order of disassembly, film the procedure on camera or mark the parts.
It is desirable that the room be ventilated and well lit:
- - Unscrew the cover bolts and remove it;
- - Remove the shaft and part of the housing;
- - Unscrew the rest of the bolts;
- - Remove the second part of the cover and gear;
- - Unscrew the screws of the pump housing;
- - Remove the gear and pump chain;
- - Remove the oil pump cover and remove the shaft;
- - Turn the variator over and remove the last cover with a screwdriver;
- - Pull the belt with clamps;
- - Remove the belt pulleys;
- - Release the pulleys from the belt.
After completing the disassembly of the variator, check each system and assembly. First of all, inspect the condition of the bearings and the size of the play (whether it has increased). Inspect the condition of the belt and its tension, gears, hydraulic unit and other spare parts.
If noise is heard in the transmission, this means that there is increased bearing wear. This malfunction is eliminated by replacing the bearings, which you can do yourself.
Conclusion
It is necessary to detect and eliminate in a timely manner. Otherwise, it will lead to more serious problems and, accordingly, more money spent. We recommend not to take risks, but to use the services of an authorized dealer or a low-profile company that repairs this gearbox.
