Principle Analysis of Support Frame The support frame is a space combination mechanism consisting of four main flexible sections with the same configuration. One of the configurations is used as a research object to analyze and a part of the support frame is shown. Dividing the rectangle into eight individual members The four-bar ABCD is a four-bar flexible bi-stable mechanism, where CD is a flexible bar member. When the flexible mechanism is in the first stable state, set the value of position S to s1, and the top of the canopy is in the contraction state; set the value of position S to be s2 when the flexible mechanism starts to move until the second steady state. Shi Peng Ding is in the maximum shade condition.
Therefore, the zooming of the canopy is mainly achieved through the function of the support frame mechanism to achieve an increase or decrease in the distance l2 from the point F to the centerline IO. Since the top configuration of the canopy is rectangular, when designing the support frame, the dimension of the flexible mechanism in the width direction of the rectangle should be smaller than the dimension of the flexible mechanism in the direction of the length of the rectangle, wherein the mechanism IEO should be smaller than the dimension of the mechanism IHO in order to realize the canopy The normal zoom. The compliant mechanism has a variability characteristic and its equivalent topological change map.
The structural design of the car awning is based on the above principle analysis, and the size of the mechanism is designed according to the actual application requirements. At present, the general automobile body length is about 4300 mm, the width is about 1700 mm, and the height is about 1700 mm. Then the maximum length of the sides of the rectangle formed by the canopy unfolding under the maximum area is: LAB=LDC=4400mm, LAD=LBC=1800mm.
The structural design of the awning canopy is divided into 3 layers, one is the sliding sub-layer indicated by the thick line, and the other two hinged mechanical layers are hinged, as shown by the dotted line. The thickness of each member is 3mm. The material has good toughness, rigidity and chemical stability.
1) The calculation of the dimensions of the two sets of components rotating in opposite directions. It can be seen that the rectangular schematic diagram of the blackboard is divided into eight components, and in the equal division method, there are three types of rods: rods on the AB side, rods on the BC side, and rods on the corners. With the data given above, it is easy to calculate that the length of the component corresponding to E and G is 2200mm, and the length of the component corresponding to H and F is 900mm. For the bar at the corner, the symmetry and the four corners are the same size. Take point A as an example to calculate the schematic diagram of the components at the corner of the blackboard.
Point A is the hinge point of the two sets of mechanisms, and e and h are the hinge points in the same mechanism and adjacent bars. It is easy to know: LAe = 1/2 × LAB = 1100mm, LAh = 1/2 × LAD = 425mm. The length of the rod at this critical point has been determined. 2) Analysis of the dimensions of the sliding secondary mechanism components.
Sliding a certain slide slider - chute, mainly reflected in the length of the T, resulting in changes in the distance between the two axis. When the front end of the slider is fully in contact with the bottom of the chute, the initial state of the top is set at this time, which is also the smallest state of the top of the tent. At this time, T>R is ensured, otherwise the axis of the slider also slides into the chute. Go in, so that the shaft will not be able to pass out. When the top of the canopy is retracted to the maximum state, it is necessary to ensure that the entire slider cannot be dislodged from the chute, so the T<L slider is guaranteed.
The roof can be enlarged to the maximum state from the minimum area state. Because each rod is limited by the specific structure and transmission angle in the movement process, there may be interference between the various components, and the actual determination of the scaling factor is more complicated. Therefore, the scalar multiple from the minimum state to the maximum state is set to m.
Let R and S be constants. When Punto is the minimum area, then L slider=T1+l selects a T1 value. At this time, ensure that T1>R:|O1O2|1=T1+l+S=2LAecos= 2200cos(1) is the angle between the dashed line and the thick solid line; when the top is the largest area, then T2<l:|O1O2|2=T2+l+S=m×|O1O2|1 ≈2200mm(2) By selecting equations (1), (2), selecting a certain value of T, combined with two constraints, the actual dimensions of the corresponding rod can be determined.
For example, when the support frame is in the first stable state, the distance from the point F to the center line IO is: In the second steady state, the analysis of the structural dimensions of the support frame takes as an example. Because the canopy and support brackets are scaled at the same time, the zoom ratio is m, so the dimension design requires:. And location. When the top of the canopy is scaled to the maximum area, at this time, the support frame is guaranteed to reach the second steady state, and the dimensional design requirements: Then. In the same way, the other structural dimensions of the support frame mechanism are determined in order.
Conclusion Inspired by the characteristics of combinational deflation of the metamorphosis mechanism, by changing the number of rods to achieve the idea of ​​changing the size of the mechanism and using the construction method of the plane tensor mechanism, a brief overview of the principle design of an automobile awning is presented. thought. Not only does the transforming mechanism have a high institutional theoretical value, but it also has a very wide range of application prospects. In particular, the research on the combination features of high folding and stretching will create more practical institutions. At present, research on the metamorphosis mechanism is still in its infancy. With further research on the metamorphosis mechanism, more discoveries will be made and applications will be made in more and wider fields.
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