Valve body / mechatronics

Genesis and application.

The valve body (also known as hydraulic controller or, in more recent developments, mechatronics) is a key component in the control system of automatic transmissions. Its history is closely linked to the evolution of the automatic transmission itself, which began to develop in the early 20th century.

The first automatic transmissions appeared in the 1930s. In 1939, General Motors introduced the Hydra-Matic transmission, considered to be the first mass-produced automatic transmission. By then, the valve body was already an integral part of the transmission, acting as a control for the flow of hydraulic oil.

In the following decades, automatic transmissions became more and more advanced. More gears were introduced and valve bodies became more complex. In the 1950s, valve bodies began to contain a greater number of valves that controlled the pressure of the hydraulic fluid in different parts of the transmission, allowing for smoother and more precise gear changes.

In the 1960s and 1970s, the first electronic components were introduced for automatic transmissions. Electronic control modules began to work in conjunction with valve blocks, enabling more precise and efficient control of gearbox operation. Valve blocks in this period became increasingly complex, containing more valves and more complicated hydraulic fluid flow channels.

In the 1980s and 1990s, the development of microprocessor technology led to even greater integration of electronics in automatic transmissions. Electronic control units (TCUs - Transmission Control Units) began to take over most of the control functions that had previously been performed by mechanical or pneumatic valves and adjusters. Valve bodies continued to play a key role, but their design had to be adapted to work with advanced electronic systems.

Today's automatic transmissions are complex systems in which valve body work with or are integrated into electronic control modules. A valve body integrated with the electronic control unit of an automatic transmission is called a mechatronics. Modern valve bodies and mechatronics have a number of sensors and precisely controlled solenoid valves, which are used to control the flow of transmission oil based on signals from the TCU. This makes it possible to achieve very smooth and fast gear changes, as well as reduced fuel consumption and greater reliability.

Construction and principle of operation.

The valve body is one of the most important components of an automatic transmission, responsible for controlling the flow of oil and thus controlling the gear shift. 

The valve body is usually made of cast aluminium for lightness and corrosion resistance. Some of the more heavily loaded components may be made of more robust metal alloys. The housing contains numerous channels and holes that direct the flow of oil to the appropriate locations inside the automatic transmission. Inside the valve body, there are numerous valves of various types - ball valves, spool valves, solenoid valves. These are responsible for opening and closing the hydraulic channels in response to oil pressure or electrical signals. Some valves have springs of varying size and strength that hold the valves in the required position or cause them to return to their original position when hydraulic pressure or current ceases. Each valve has a specific function, e.g. shift valves, pressure control valves, shut-off valves. Thanks to the solenoid valves controlled by the TCU, it is possible to precisely control the fluid pressure in the individual circuits. The individual sections of the hydraulic block are separated and sealed by, among other things, a so-called separation plate. This is one of the main components sealing the channels inside the valve body. Today's valve bodies and mechatronics are also equipped with filters of various designs, whose task is to catch any impurities in the oil. Newer design valve bodies as well as mechatronic units are equipped with a number of sensors such as input and output speed sensor, sensors for gear engaged and clutch engaged (DCT/DSG), oil pressure, oil temperature, etc.

The operation and control of today's valve bodies and mechatronics units is based on the use of input signals from a number of sensors that monitor the operating status of the automatic transmission, engine and driver requests. Based on these, the electronic transmission controller TCU sends control signals to the solenoid valves in order to engage the appropriate gear. Depending on the transmission type, the solenoid valves can manage other functions such as the control of individual clutches (DCT/DSG), activation of the Lock-up clutch in the torque converter, opening or closing of the oil cooling circuit or activation of the parking lock. By appropriately directing the oil flow through the various channels and valves, the pressure in the individual sections of the transmission changes. Changes in hydraulic pressure cause actuators (e.g. pistons, clutches, forks) to move, resulting in gear changes or activation of other functions. 

Remanufacturing process.

The valve body or mechatronics is disassembled and subjected to a preliminary cleaning. All components are visually inspected for visible damage such as cracks, wear or corrosion. If there is no such damage, the valve body/mechatronics is assembled with new seals and then tested on a special test bench. If the deviation from the required values is too great, the valve body or mechatronics is disassembled into its individual components for thorough verification. Valves, channels of the hydraulic body are thoroughly verified, and the tightness of individual hydraulic circuits is checked. If leakage is present, it can be restored after machining a hole in the housing and using an oversized control valve. Another way is to replace the damaged part of the housing or to use a complete, brand-new valve body/mechatronics. One of these solutions is required in the event of serious mechanical or electronic damage to the valve block/mechatronics.

Another type of damage is electrical/electronic faults. It is not uncommon to encounter problems with electronic components of the system such as sensors or the automatic transmission controller. In some cases, it is possible to replace or repair the faulty components. If this is not possible, the only solution is to replace the controller or the complete valve body/mechatronics with a brand new one. After replacing the controller with another one, we perform a software cloning operation, so that the next controller is immediately properly programmed and ready for operation.

The remanufactured valve body/mechatronics is pressure tested to check that all valves and channels are operating correctly under the correct hydraulic pressure. The test takes place under real operating conditions simulating different driving scenarios to ensure that it is operating correctly throughout the operational range.

Causes and types of damage

Symptoms that may indicate a defective valve body/mechatronics:

1. Lack of smooth gear changes - delays, jerks or gear changes that are too abrupt.
2. No gear change or limited gear change, no gears.
3. No response or delayed response when switching between P-R-N-D modes.
4. Jerks or bumps when switching between P-R-N-D modes.
5. Lack of power transmission - the engine revs up but the vehicle does not move.

The most common valve body/mechatronics failures are:

1. Damaged or worn valves, solenoid valves.
2. Leaking, worn or damaged seals.
3. Mechanical damage - scratches, cracks, deformation.
4. TCU software problems.
5. Problems with electronic components.