Method for preventing automobile safety belt from being stuck and accumulated at D ring
1. A method for preventing the jamming and accumulation of a vehicle safety belt at a D ring is characterized in that:
need to satisfy the formula
Wherein, mu1Is the circumferential friction coefficient of the braid and the D ring, mu2The axial friction coefficient of the woven belts and the D ring is shown, alpha is the included angle of the two woven belts in an XZ plane and is alpha, and beta is the wrap angle of the woven belts and the D ring.
2. The method of claim 1, further comprising the step of:
s1, acquiring an outlet position of a safety belt retractor according to a vehicle body structure, wherein a D ring comprises a height regulator space coordinate; obtaining R point information of the seat according to the type selection of the seat, and adjusting the travel range; acquiring the sliding friction coefficient of the safety belt in the D ring;
s2, acquiring a space angle of the safety belt bypassing the D ring according to the safety belt path; the projection of the angle on the XZ plane of the coordinate system of the whole vehicle is the included angle alpha of the planes of the two woven belts, and the projection on the YZ plane is the wrap angle beta of the safety belt and the D ring;
step 3, establishing a stress analysis model of the safety belt and the D ring in the collision process;
FSis the tension of the webbing between the ring D and the shoulder of the occupant, FRIs the tension force of the mesh belt between the D ring and the coiler, FPWebbing tension between retractor and D-ring, f, when the belt is pre-tightenedcAxial friction of the webbing with the D-ring, fhThe axial friction force between the woven belt and the D ring is adopted. At the initial moment, the resultant force of the shoulder strap force and the retractor force actsThe line passes through the fixed point of the D ring and is in counter-force balance with the fixed point;
FR＝FS
when the safety belt is pre-tightened, the mesh belt slides to the coiler along the D ring, and at the moment
FP＝FS+fc
fcThe friction force of the ribbon in the sliding direction is obtained by Euler's formula
Wherein mu1The circumferential friction coefficient of the mesh belt and the D ring is shown; the ribbon is not piled up and the following condition is satisfied
S4, checking the arrangement of the safety belt according to the friction coefficient of the ring D in the step S1 and the space angle of the safety belt in the step S3; when the included angle of the woven belt satisfies the following relation in the XZ plane projection alpha, the safety belt is not piled up at the D ring position:
and S5, if the parameters do not meet the detection formula, repeating the step S1, adjusting the fixed position of the safety belt retractor, the height adjustment position of the D ring, the seat stroke and the like, and rechecking until the detection requirements are met.
Background
The safety belt is an important component of a safety restraint system of an automobile and generally comprises a retractor, a D ring, a safety belt and a fixing point of the safety belt. The seat belt type automobile seat cushion has the functions of keeping a passenger in a correct sitting position and restraining the passenger from moving through the seat belt during the automobile collision process, so that the injury of the passenger is reduced. This requires that the seat belt be fitted with components that directly affect the wearing posture of the seat belt, such as the seat R point, the seat belt fixing point, and the D-ring position, during the design process, so that the seat belt reaches the optimum stressed state, thereby protecting the safety of the occupant. However, in the actual design process, it is found that when the relationship is matched beyond a certain range, the safety belt is locked at the D ring and cannot slide normally along the D ring, so that the partial function of the safety belt is disabled or even the safety belt is cut off.
In order to solve the above problem, there is a need for a system that can assess the inherent relationship between the position of the belt and seat R point, belt anchor point and D-ring during a collision and the belt sticking in the D-ring. The invention reasonably analyzes the accumulation phenomenon of the woven belt at the D ring in the collision process of the safety belt. A stress analysis model of the D ring is established, and a reasonable arrangement boundary calculation method of key points of the safety belt is provided.
Disclosure of Invention
The invention mainly aims to provide a design method for arranging key points of a safety belt, which ensures that the safety belt can normally pass through a D ring and avoids the failure or abnormity of other functions caused by the clamping stagnation of the safety belt; analyzing the safety belt tension, the friction force along the circumferential direction and the friction force along the axial direction born by the D ring in the working state of the safety belt by combining the circumferential friction coefficient and the axial friction coefficient of the D ring, and establishing a safety belt mechanical model in the working state; through stress analysis, a spatial arrangement angle boundary of the safety belt without clamping stagnation is obtained, and the design purpose of the arrangement positions of the safety belt key points and the seat R points is achieved.
In order to realize the purpose of the invention, the invention adopts the following technical scheme:
a method for preventing a vehicle safety belt from being stuck and accumulated at a D ring,
need to satisfy the formula
Wherein, mu1Is the circumferential friction coefficient of the braid and the D ring, mu2The axial friction coefficient of the woven belts and the D ring is shown, alpha is the included angle of the two woven belts in an XZ plane and is alpha, and beta is the wrap angle of the woven belts and the D ring.
The method comprises the following steps:
s1, acquiring an outlet position of a safety belt retractor according to a vehicle body structure, wherein a D ring comprises a height regulator space coordinate; obtaining R point information of the seat according to the type selection of the seat, and adjusting the travel range; acquiring the sliding friction coefficient of the safety belt in the D ring;
s2, acquiring a space angle of the safety belt bypassing the D ring according to the safety belt path; the projection of the angle on the XZ plane of the coordinate system of the whole vehicle is the included angle alpha of the planes of the two woven belts, and the projection on the YZ plane is the wrap angle beta of the safety belt and the D ring;
step 3, establishing a stress analysis model of the safety belt and the D ring in the collision process;
FSis the tension of the webbing between the ring D and the shoulder of the occupant, FRIs the tension force of the mesh belt between the D ring and the coiler, FPWebbing tension between retractor and D-ring, f, when the belt is pre-tightenedcAxial friction of the webbing with the D-ring, fhThe axial friction force between the woven belt and the D ring is adopted. At the initial moment, the resultant force action line of the shoulder strap force and the retractor force passes through the fixed point of the D ring and is in counter-force balance with the fixed point;
FR＝FS
when the safety belt is pre-tightened, the mesh belt slides to the coiler along the D ring, and at the moment
FP＝FS+fc
fcFor the webbing in the sliding directionThe friction force of (A) is obtained by Euler's formula
Wherein mu1The circumferential friction coefficient of the mesh belt and the D ring is shown; the ribbon is not piled up and the following condition is satisfied
S4, checking the arrangement of the safety belt according to the friction coefficient of the ring D in the step S1 and the space angle of the safety belt in the step S3; when the included angle of the woven belt satisfies the following relation in the XZ plane projection alpha, the safety belt is not piled up at the D ring position:
and S5, if the parameters do not meet the detection formula, repeating the step 1, adjusting the fixed position of the safety belt retractor, the height adjustment position of the D ring, the seat stroke and the like, and checking again until the detection requirements are met.
The invention has the beneficial effects that:
1. according to the invention, the problems of accumulation and jamming of the safety belt at the position of the D ring in the vehicle collision process can be greatly improved by reasonably matching the key angles alpha and beta on the safety belt path and the friction coefficient at the D ring, so that the safety of passengers is guaranteed.
2. The implementation of the invention can rapidly inspect the fixed point of the safety belt retractor, the height adjustment fixing and adjusting range of the D ring, the R point of the seat and the stroke adjusting range by the inspection method in the initial stage of the arrangement of the automobile safety belt, thereby avoiding the changes of peripheral structures, interior decorations and the like caused by the problem of ribbon clamping in the later stage, greatly reducing the risk of the arrangement of the safety belt and shortening the development period.
Drawings
Figure 1 is an analysis of the force exerted by the harness at the ring D of the XZ plane;
fig. 2 is a force analysis of the harness at the YZ plane D loop.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1: refer to fig. 1-2.
A method for preventing a vehicle safety belt from being stuck and accumulated at a D ring,
need to satisfy the formula
Wherein, mu1The circumferential friction coefficient of the webbing with the D-ring, i.e. the friction coefficient between the webbing and the surface of the D-ring when the seat belt is normally pulled out, is2The axial friction coefficient of the mesh belt and the D ring, namely the friction coefficient of the safety belt sliding back and forth relative to the D ring; alpha is the included angle of the two woven belts in the XZ plane and beta is the wrap angle of the woven belts and the D ring.
The detailed design method comprises the following steps:
the invention mainly aims to provide a design method for arranging key points of a safety belt, so that the safety belt can normally pass through a D ring, and the failure or abnormity of other functions caused by the clamping stagnation of the safety belt is avoided.
The design principle is that the space angle and the position relation of the winding path of the safety belt are obtained according to the position information of key points on the winding path of the safety belt, the R point information of the seat and the wearing relation of the safety belt and a passenger; analyzing the safety belt tension, the friction force along the circumferential direction and the friction force along the axial direction born by the D ring in the working state of the safety belt by combining the circumferential friction coefficient and the axial friction coefficient of the D ring, and establishing a safety belt mechanical model in the working state; through stress analysis, a spatial arrangement angle boundary of the safety belt without clamping stagnation is obtained, and the design purpose of the arrangement positions of the safety belt key points and the seat R points is achieved.
The key points of the safety belt comprise a retractor, a fixed point of a D ring on a vehicle body and a contact point of the safety belt and the D ring; the position of the R point of the seat relates to the contact position of the safety belt and the shoulder of the passenger, and can be obtained by winding the safety belt by a simulation method; the spatial path and the angle of the safety belt from the retractor to the shoulder of the dummy can be acquired through the safety belt fixing point and the contact point of the safety belt and the shoulder of the passenger; analyzing the stress state of the safety belt during working, and when the woven belts on the two sides of the D ring are tensioned and slide along the circumferential direction of the D ring, if the component force of the resultant force of the two woven belts in the axial direction of the D ring is larger than the axial friction force, the woven belts move relatively along the axial direction of the D ring, so that the clamping stagnation of the safety belt is easily caused; on the contrary, if the resultant force of the woven belts is smaller than the axial friction force, the woven belts are not blocked.
The stress analysis process is as follows:
s1, acquiring an outlet position of a safety belt retractor according to a vehicle body structure, wherein a D ring comprises a height regulator space coordinate; obtaining R point information of the seat according to the type selection of the seat, and adjusting the travel range; acquiring the sliding friction coefficient of the safety belt in the D ring;
s2, acquiring a space angle of the safety belt bypassing the D ring according to the safety belt path; the projection of the angle on the XZ plane of the coordinate system of the whole vehicle is the included angle alpha of the planes of the two woven belts, and the projection on the YZ plane is the wrap angle beta of the safety belt and the D ring;
step 3, selecting the maximum working condition of the alpha angle, and establishing a stress analysis model of the safety belt and the D ring in the collision process;
FSis the tension of the webbing between the ring D and the shoulder of the occupant, FRIs the tension force of the mesh belt between the D ring and the coiler, FPWebbing tension between retractor and D-ring, f, when the belt is pre-tightenedcAxial friction of the webbing with the D-ring, fhThe axial friction force between the woven belt and the D ring is adopted. At the initial moment, the resultant force action line of the shoulder strap force and the retractor force passes through the fixed point of the D ring and is in counter-force balance with the fixed point;
FR＝FS
when the safety belt is pre-tightened, the mesh belt slides to the coiler along the D ring, and at the moment
FP＝FS+fc
fcThe friction force of the ribbon in the sliding direction is obtained by Euler's formula
Wherein mu1The circumferential friction coefficient of the woven belt and the D ring is shown. At the moment, the resultant force direction of the shoulder strap force and the retractor force changes, and the D ring is subjected to the pulling force component of the braid and the axial friction force f along the D ringhAnd (4) acting. When the resultant force of the tension of the woven belts along the axial direction is smaller than the friction force, the woven belts do not slide relatively, and the woven belts do not have the accumulation phenomenon; when the resultant tension force is larger than the friction force, the two parts slide relatively to each other, so that the braid is easy to accumulate, and therefore, the condition that the braid is not accumulated can be met
S4, checking the arrangement of the safety belt according to the friction coefficient of the ring D in the step S1 and the space angle of the safety belt in the step S3; when the included angle of the woven belt meets the following relation in the XZ plane projection alpha, the safety belt can not be stacked at the position of the D ring.
Friction force f along D ring axial directionhIs related to positive pressure and friction coefficient, wherein the positive pressure is N ═ FSBeta, the D-ring is designed with anti-slip features to increase its axial friction coefficient, and the D-ring axial motion friction coefficient is set as mu2. Alpha is related to the positions of the retractor, the D ring fixing point and the R point of the seat, and the alpha angle can be changed by adjusting the positions of all key points. Therefore, the angle α, which is to satisfy the following equation, is evaluated as a control parameter for preventing the webbing from being accumulated
Wherein, mu1，μ2The friction coefficient of the ring D is constant; beta is spatially related to the Y direction of the vehicle and can be taken as a constant; according to the formula, the angle range of alpha can be determined, and the safety belt retractor fixing point, the D ring fixing point and the seat R point position are designed according to the angle range.
And S5, if the parameters do not meet the detection formula, repeating the step 1, adjusting the fixed position of the safety belt retractor, the height adjustment position of the D ring, the seat stroke and the like, and checking again until the detection requirements are met.
In the actual design process, the problems of accumulation and clamping stagnation of the safety belt at the position of the D ring in the vehicle collision process can be greatly improved by reasonably matching the key angles alpha and beta on the safety belt path and the friction coefficient at the position of the D ring, and the safety of passengers is guaranteed.
Examples of the applications
The existing safety belt is only arranged by considering the strength of a connecting piece and the wearing comfort of a passenger, and the problem that the woven belt is clamped in a D ring in the collision process of the safety belt is ignored. Research shows that the force value of the safety belt of the chest of the passenger can be increased by 600 plus 1000N due to the webbing accumulation at the D ring position, and the designed protection effect on the chest of the passenger cannot be achieved. And the safety belt arrangement is usually inspected through a tool sliding table experiment, so that the detection period is long, and the experiment cost is high. The safety belt stacking detection method and the safety belt stacking detection device can detect the stacking of the safety belt on the D ring at the initial design stage, and greatly reduce the safety belt arrangement risk.
In the case, the projection alpha of the spatial arrangement angle of the safety belt of a certain vehicle type on the XZ plane is 66.5 degrees, and the wrap angle beta of the safety belt on the D ring is 123.3 degrees. The belt angle check α in the actual layout state should be less than 59.8 °. The basic scheme is applied to carry out tooling experiments. After the test, the webbing was heavily accumulated at the D-ring position, and the shoulder belt was increased by about 600N from the design value. The D-ring anchor position was adjusted up to a reduced angle of α to 61.9 °, and slight stacking still occurred. The alpha angle continues to decrease to 57.7 deg.. Test experiments showed that no pile of seat belt was formed at the D-ring position.
TABLE 1D Ring fixation Point adjustment and test results
It should be understood that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the modifications or equivalent substitutions can be made on the specific embodiments of the present invention without departing from the spirit and scope of the present invention, and all modifications or equivalent substitutions should be covered in the claims of the present invention.
