How many types of solenoid valves are there in bus pneumatic systems?

In complex bus pneumatic systems-from air brakes and air suspension to bus door controls-solenoid valves are key electronic switches that control pneumatic functions. They convert electrical signals into precise pneumatic actions. For example, the dedicated TG2522-08W solenoid valve used in bus door systems.

 

Pneumatic solenoid valves are primarily classified based on three basic characteristics: port configuration, actuation method, and coil type. This constitutes the basic "language" of valve specifications.

Port Configuration (Channel/Location): Describes the number of gas lines (ports) and the switching status of valves. It is usually expressed as (number of ports)/2, where "2" usually refers to the location (e.g., 5/2 ports).

Drive method: refers to the movement mode of the internal mechanism of the valve. Direct-acting valves are driven solely by the magnetic force of an electromagnetic coil, while pilot-operated valves are driven by system air pressure, thus enabling the control of higher flow rates.

Coil type: Defines the electrical control logic. A single-coil valve will spring back to its default position after power is cut off (fail-safe). Dual-coil valves use electrical pulses for switching and remain in the last position until another coil is pulsed (bistable).

A practical example is the TG2522-08W valve, which clearly fits these classifications: it is a 5/2-way, dual-coil, direct-acting solenoid valve.

 

 

This classification is the most common method for identifying valve functions.

Two-way valve: the simplest single-circuit switch. They have one air inlet and one air outlet.

A three-way valve has one air inlet, one air outlet, and one exhaust outlet. They can pressurize and exhaust a single chamber, just like a simple single-acting cylinder.

Four-way/two-way valve: has four ports and two positions. They control double-acting cylinders by directing air to one side of the piston and expelling air from the other side, then reversing the airflow direction.

Five-way/two-way valve: the most common choice for precise control of double-acting cylinders. They have five ports: one pressure inlet (P), two cylinder ports (A and B), and two exhaust ports (EA and EB). This allows for independent control of the exhaust, enabling different extension and retraction speeds.

The TG2522-08W is a perfect example of a 5/2-way valve. In the bus door system, its interface is connected to both sides of the door lock cylinder. When one coil is energized, air extends out of the cylinder (opens the door); when the other coil is energized, air retracts into the cylinder (closes the door). These two independent exhaust channels ensure smooth operation.

 

 

The choice of which type of solenoid valve to use depends on the required airflow and response time.

Direct-acting solenoid valve: The solenoid valve core directly controls the opening or closing of the main valve orifice. They operate at pressures above 0 bar and have a fast response time, but due to the limited driving force of the solenoid valve, they are typically used for smaller flow rates.

Pilot-operated solenoid valve: A small, direct-acting pilot valve controls a larger main valve. They require a certain pilot pressure to operate, but can handle higher flow rates using relatively small, low-power solenoid valves.

For applications requiring fast and reliable response at medium flow rates, such as bus or truck door control, direct-acting solenoid valves are typically the preferred choice. The TG2522-08W adopts this direct-acting design, providing a fast response time (approximately 0.05 seconds), ensuring that the doors move immediately after the driver or passenger issues a command, thereby directly improving operational efficiency and safety.

 

 

This distinction determines the valve's behavior after power failure.

Single coil valve: This type of valve has a spring return function. When energized, the valve switches positions; when de-energized, the spring will spring it back to the default "rest" position. This provides fail-safe operation. For example, the valve controlling the air brake may have a spring-reset function to return it to the "exhaust" position to ensure safety.

Double coil valve: This type of valve does not have a spring. Each coil must be energized momentarily in order to switch the valve position. After switching, even if the power is cut off, the valve will remain (locked) in that position until the other coil is energized. This is called "bistable" or memory control.

The TG2522-08W uses a dual-coil solenoid valve. This is crucial for bus doors: a brief pulse is enough to open the door, and the door can remain open without a continuous power supply. The other pulse is used to close the car door. This design saves energy, reduces coil heat, and ensures that the doors remain in their previously set state, which is crucial for the passenger control system.

 

 

Simple 3/2-way and 4/2-way solenoid valves are widely used in buses due to their versatility in controlling numerous auxiliary functions. For example, a 3/2-way solenoid valve is used to operate the single-acting airbags of a dump truck bed, engage pneumatic switches, or control the pneumatic horn. The more common 4/2-way solenoid valve is used to control differential lock engagement, operate air suspension unloading valve, or control follower shaft position.

These simple solenoid valves can efficiently and economically handle most on/off or simple reciprocating motion functions. However, for systems that require independent control of extension and retraction-such as the smooth, speed-controlled opening and closing of large passenger doors-a 5/2-way solenoid valve like the TG2522-08W is required. Its independent exhaust outlet allows for the installation of a speed-controlled muffler, enabling technicians to fine-tune the movement of the doors to ensure safety and passenger comfort.

 

 

The world of pneumatic solenoid valves is clearly defined by classification: by their port size (two-way, three-way, five-way/two-way, etc.), actuation method (direct or pilot-operated), and coil logic (single or double coil). While simple three-way/two-way and four-way/two-way valves can handle many truck functions, specialized applications require precise specifications.

The TG2522-08W pneumatic solenoid valve is a prime example of this kind of precision engineering. As a direct-acting five-way/two-way dual-coil valve, it is designed for high-intensity, high-cycle control of passenger doors in Yutong, King Long, and Zhongtong buses. Its design ensures rapid response, reliable locking action, and the fine control required for passenger safety.

When maintenance or repair requires valve replacement, in order to restore system integrity and vehicle safety, selecting valves that are fully matched to these OEM specifications (port size (G1/4"), voltage (typically DC24V) and function) is non-negotiable.

 

 

location:

No. 9,Sanqiao Road, Fengdong New City, Xi'xian New District, Xi'an , Shaanxi,China

Moblie/whatsapp/wechat:

 +86 13310989421

Email:

laifeng@onodetruckparts.com