Many models of MAZ vehicles are equipped with a clutch release actuator with a pneumatic booster, an important role in the operation of which is played by the actuator actuation valve. Learn all about the MAZ clutch actuator valves, their types and designs, as well as the selection, replacement and maintenance of this part from the article.
What is the MAZ clutch actuator actuator actuator valve
The MAZ clutch actuator actuator actuation valve (clutch booster valve, KUS) is a pneumatic valve that provides the supply and bleed of compressed air from the pneumatic cylinder of the clutch booster when the clutch is engaged and disengaged.
MAZ trucks of the 500 family models (both early and later 5335, 5549), more modern MAZ-5336, 5337, 5551, and the current MAZ-5432, 6303 and some others are equipped with a double-plate clutch, which requires considerable effort. Direct control of such a clutch from the pedal would be too tedious for the driver and would significantly impair the ability to drive the car, therefore, an additional unit is introduced into the clutch release drive (PVA) of these truck models - a pneumatic booster.
Structurally, a PVA with a pneumatic booster consists of a lever drive connected to the pedal, a pneumatic cylinder and an intermediate component - the KUS. The cylinder is fixed on the frame of the car (through the bracket), its rod is connected through a two-arm lever to the clutch release fork roller. The KUS rod is connected to the opposite arm of the lever, and the KUS body is connected to the clutch pedal through a system of rods and levers by means of a rod.
The LCU is both the power component of the lever PVA and the sensitive component of the amplifier cylinder control. The input signal of the CRU is the position and direction of movement of the clutch pedal: when you press it, the LCU supplies air to the cylinder, ensuring that the amplifier is turned on (that is, it disengages the clutch), when it is released, the LCU bleeds air from the cylinder into the atmosphere, ensuring that the amplifier is turned off (that is, the clutch is engaged). Therefore, the KUS is a critical part for the operation of the clutch, if it malfunctions, it is necessary to repair or completely replace it. To make repairs correctly, it is necessary to obtain basic information about the existing types of valves, their structure and some features.
The general structure and principle of operation of MAZ valves for engaging the clutch actuator
On all MAZ vehicles, KUS that are fundamentally identical in design are used. The basis of the design is a cylindrical body assembled from three cast parts - the body itself and two end covers. Covers usually have a flange design, they are attached to the body with screws, gaskets must be used for sealing. In the front cover of the case, a rod of increased length is rigidly installed, at the end of which there is a fork for attaching to the intermediate two-arm clutch drive lever.
The body is divided into two cavities, each of which has threaded channels for connecting hoses. In the front cavity there is a valve, in the normal position of the spring pressed to its seat (in its role is the collar between the cavities). The channel in the front cavity is the supply - through it compressed air is supplied to the valve from the corresponding receiver of the car's pneumatic system.
In the rear cavity of the case there is a hollow rod coming out of the back cover, and carrying a fork for attaching to the two-arm lever of the clutch fork roller. The rod has a cavity that communicates with the atmosphere. A thread is cut on the rod, on which the adjusting nut is located along with its locknut. The channel in the rear cavity is discharge, a hose is attached to it, which provides compressed air to the amplifier cylinder, as well as the exhaust of air from the cylinder back to the KUS when the pedal is released.
The functioning of the KUS and the entire PVA with a pneumatic booster is quite simple. When the clutch pedal is released, the valve is closed, so the PVA is inactive - the clutch is engaged. When the pedal is pressed, the KUS, along with the rest of the components, shifts until the gap between the adjusting nut on the stem and the rear cover of the housing is selected. In this case, the stem rests on the valve and lifts it - as a result, air from the front cavity of the valve flows into the rear cavity and enters the clutch booster cylinder through the hose. Under the influence of compressed air, the cylinder piston shifts and ensures the rotation of the clutch fork roller - it raises the pressure plate and disengages the clutch. When the pedal is released, the above processes occur in the reverse order, the valve closes and the air from the amplifier cylinder through the rear cavity of the KUS and the cavity in its rod is vented into the atmosphere, the force from the fork is removed and the clutch is re-engaged.
Clutch release drive device MAZ
The design of the MAZ clutch release booster valve
The dimensions of the valve and the cross-section of all holes are selected so that the air supply to the cylinder of the PVA amplifier is carried out quickly, and the air is vented into the atmosphere with a slight deceleration. This achieves a smooth engagement of the clutch and a reduction in the wear rate of all rubbing parts.
Nomenclature and applicability of MAZ valves for clutch actuator activation
Several basic models of KUS are used on MAZ trucks:
- Cat. number 5335-1602741 - for MAZ-5336, 5337, 54323, 5434, 5516, 5551, 6303, 64255. Supplied without hoses, adjusting nuts and forks;
- Cat. number 5336-1602738 - for MAZ-5336 and 5337 vehicles of various modifications. It has a shortened stem of 145 mm, comes complete with hoses;
- Cat. number 54323-1602738 - has a short rod of 80 mm, comes complete with hoses;
- Cat. number 5551-1602738 - for MAZ-5337, 54323, 5551 vehicles. It has a stem of 325 mm, comes complete with hoses;
- Cat. Number 63031-1602738 - has a stem of 235 mm, comes complete with hoses.
The valves differ in the design and dimensions of the body, the length of the stems/rods and the length of the hoses. Parts are supplied to the market in various configurations - without hoses and with hoses, in the second case, rubber hoses with protection in the form of a twisted spring and with standard connecting fittings with union nuts are used.
Issues of selection, replacement and maintenance of the MAZ valve for the inclusion of the clutch actuator
KUS is a pneumatic unit, which is additionally subjected to mechanical loads and the effects of negative environmental factors. All this leads to gradual wear of the valve and can cause various malfunctions - damage to the valve, air leaks through the seals, deformation of the rod and rod, damage to the body, "subsidence" of the springs, etc.
For replacement, it is necessary to take a valve of the same type and model that was installed on the car earlier, or it is recommended as an acceptable analogue by the manufacturer. Here it should be borne in mind that valves of various types have different characteristics and dimensions, so the "non-native" part may not only not fall into place, but also not ensure the normal operation of the clutch drive.
When buying a valve, you also need to take into account its equipment, if necessary, you may need to purchase additional hoses, plugs and fasteners. To avoid unnecessary costs and loss of time, it is necessary to immediately check the condition of the parts in the drive, fasteners and hoses.
Replacing the valve must be carried out in accordance with the instructions for repairing the car, but usually this operation comes down to simply dismantling the old part and installing a new one, while the air should be bleed from the pneumatic system. Then it is necessary to adjust the valve using the nut on its stem - the distance between it and the back cover of the KUS body should be 3.5±0.2 mm. Subsequently, all routine maintenance of the valve is reduced to its external inspection and adjustment of the specified clearance.
If the KUS is selected and installed correctly, then the operation of the clutch drive of the Minsk truck will be reliable and confident in any operating conditions.
Clutch release actuator valves MAZ
Post time: Jul-11-2023