1 Virtual prototype assembly establishes the solid model of each component, according to the structural characteristics of the physical prototype of the scroll compressor, correctly describes the positional relationship and motion relationship between the components, so as to determine the relative spatial position of the component in the virtual environment. Perform the assembly work of the virtual prototype.

In the virtual assembly process, a model based on component features is used, and the combination of parts, components, and subassemblies to the total assembly is a technical route. According to the characteristics of the virtual prototype, the total assembly of the scroll compressor can be decomposed into two sub-assemblies of the moving part and the static part. Each component in the moving component sub-assembly is characterized by motion, mainly including the moving disk assembly, the cross slip ring and the crankshaft assembly; the components in the static component sub-assembly are characterized by static, mainly by the static disk assembly, the anchor bolt and the machine. Body components and other components.

Optimization of the assembly structure can be achieved by modifying the characteristics of the individual parts in the virtual prototype's total assembly. Establish an exploded view of the assembly to visually observe the positional relationship between the components. According to the management features, technical features, material features, precision features, shape features, and assembly features, detailed information of the virtual prototype can be queried.

2 Motion Simulation The main work of Pro /Engineer motion simulation is to complete assembly and define connections, add drivers, motion simulation and result playback analysis.

2. 1 Definition Constraints The constraints of moving parts in a virtual assembly are changed from placement type to connection type. Pro/Engineer provides 8 connection types to choose from: rigid, pin, sliding rod, cylinder, plane, ball, Welding, bearing, choose the options to set different modes of motion, degrees of freedom and constraints. Depending on the type of connection, the system will display the corresponding constraints.

The five key constraints need to be defined: (1) The crankshaft and the pulley are connected by a pin; (2) the eccentric shaft sleeve and the bracket body are connected by a pin; (3) the connection relationship between the cross slip ring and the bracket body is a sliding rod; 4) It indicates that the coupling relationship between the eccentric shaft and the movable scroll bearing is a pin; (5) the cross slip ring is connected with the sliding rod of the movable scroll; the other fixed parts are assembled in the same manner as in the virtual assembly. In the definition of (3) and (5), the pin connection of the movable scroll and the eccentric sleeve assembly should be defined to define its coupling with the sliding rod of the cross slip ring.

2. 2 Motion Simulation Defining the Motion Source The motion of the mechanism can be defined by adding a drive to the original, ie the servo motor, and setting the time and motion increments. The driver (servo motor) is the power source for the motion of the mechanism, and the driver is placed on the connecting shaft of the crankshaft and the pulley (ie, the middle (1) connection), and the type of motion of the driver is defined as a rotary motion. In the tab of the contour, define this drive as a uniform rotation motion, the mode selection constant, and the A value is set to 50.

Defining Motion Analysis In the Motion Analysis dialog box, you can set the execution time of the servo motor defined above and the number of frames of the animated screen, the frame rate, and the minimum time interval between the two screens. After defining these, the next step is to define the locking elements. Motion simulation can be performed when all of the above definitions are completed.

Motion Playback Click the Mechanism playback option in the Menu Manager to demonstrate, save, restore, delete or export the results of motion simulations, as well as perform interference checks. After analyzing the motion analysis defined in the previous section, you can demonstrate the playback result through the animation dialog box and output the result in the M PG format file through the capture dialog box.

3 Simulation results analysis Using Pro/Engineer's own mechanism analysis function to realize the motion simulation of the virtual prototype of the scroll compressor, verify the rationality of the design, and provide the basis for optimizing the design. Through the motion simulation, it is possible to analyze the mutual meshing condition of the spiral tooth profile of the scroll compressor and the fixed scroll of the scroll compressor, observe the motion track of the orbiting scroll, whether there is interference in the mechanism motion, and whether the scroll tooth is in the working process. The crescent-shaped volume chamber can be formed to realize the compression of the gas, and the rationality of the movement process of the moving component composed of the crankshaft, the dynamic balance iron, the movable scroll and the pulley is analyzed, and whether the motion law of the cross slip ring is correct or the like.

(1) Vortex type line meshing

The meshing process of the wraps. Two involute scrolls of the same shape but with an angular phase difference of 180, one of which is a fixed scroll, and the other is a scroll that is driven by an eccentric shaft and whose axis revolves around the axis of the fixed scroll. After assembly, a number of crescent-shaped closed cavities are formed between the two scrolls. The shape and shape of these crescent-shaped air cavities change with the rotation of the eccentric shaft. The gas enters the suction chamber from the suction port and is successively taken into the crescent-shaped air chamber that communicates with the suction chamber. As these peripheral crescent-shaped air chambers are closed and no longer communicate with the suction chamber, their closed volume is gradually transferred to the center of the fixed scroll and shrinks, and the gas is continuously compressed and the pressure is increased. Since the dynamic and static vortex continuously forms a closed cavity, the inhalation, compression, and exhaust processes are continuously performed. There is no interference phenomenon during the meshing process, and the working characteristics of the wraps conform to the physical prototype of the scroll compressor.

(2) Movement law of crankshaft components

On the crank pin of the shaft head, the dynamic balance iron heat fitting is fixed at the corresponding position of the crankshaft, and the position is determined by the mass of the crank pin, the radius of gyration and the structure of the crankshaft. During the crankshaft rotation, both the crank pin and the large balance iron rotate around the centerline of the crankshaft as shown.

(3) Movement law of anti-rotation mechanism An anti-rotation mechanism is arranged between the movable scroll and the bracket body, and a cross slip ring is selected for design. A pair of rectangular convex keys on the cross slip ring cooperate with a pair of key grooves on the back surface of the movable scroll, and the other pair of rectangular convex keys cooperate with a pair of key grooves on the bracket body. The convex key can only reciprocate in the keyway. When the crank pin rotates the movable scroll, the rotation of the scroll is restricted. The crankshaft drives the center of the base of the movable scroll to make a radius around the center of the base of the fixed scroll. The circular orbital motion, the upper and lower limit positions during the movement of the cross slip ring are as shown.

4 Conclusions (1) The mechanism analysis module Pro/M echan ism realizes the motion simulation of the scroll compressor. It can be seen from the simulation results that the spiral tooth profile of the scroll and the static disk of the scroll compressor are mutually meshed and reasonable, and there is no interference phenomenon. In the process of motion, a crescent-shaped volume cavity can be formed, which can realize gas compression; crankshaft components The law of motion is correct, the motion law of each part meets the requirements; the design of the cross-slip ring of the anti-autobiographic mechanism is reasonable, and the motion law conforms to the actual working characteristics.

(2) Virtual design of scroll compressor was carried out by Pro/Engineer, including 3D modeling, virtual assembly and motion simulation of components. The obtained virtual prototype is consistent with the physical prototype, and the virtual design method has a strong technical advantage in the design process of the scroll compressor.

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