Flexible flow diversion system and control method
By using a flexible airflow system, flexible components and retractors are employed to adapt to different vehicle gaps and speeds, solving the problem of rigid side fairing structures and improving the vehicle's aerodynamic performance and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DONGFENG COMML VEHICLE CO LTD
- Filing Date
- 2023-10-31
- Publication Date
- 2026-05-12
AI Technical Summary
Existing side fairings are rigid or inflexible structures, which cannot accommodate the different gaps between the cab and cargo box in different vehicles. They are also prone to damage when the vehicle pitches or turns, and the fixed deflection angle cannot meet the deflection requirements at different vehicle speeds.
A flexible flow guiding system is adopted, including a first flow guiding unit set on the top of the cab and a second flow guiding unit located on both sides of it. Both are composed of flexible parts and retractors. The length and tension of the flexible parts are adjusted according to the vehicle speed by the control device to adapt to the flow guiding requirements under different gaps and vehicle speeds.
The flexible air deflector system achieves adaptability under different vehicle gaps and speeds, reduces wind resistance, avoids damage to the air deflector, and improves the vehicle's aerodynamic performance.
Smart Images
Figure CN117382755B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of vehicle airflow control devices, and in particular to a flexible airflow guiding system and control method. Background Technology
[0002] Currently, there are various types of trailers, and the gooseneck length of different trailers also varies. There are gaps of varying sizes between the trailer and the tractor, and between the cab of the cargo truck and the cargo box. When the gap is too large, it will have a significant negative impact on the fuel consumption of the train.
[0003] To address the above issues, various OEMs have introduced aerodynamic devices, such as side fairings, which are air deflectors installed behind the cab of trucks or tractor-trailers. Their main function is to guide the airflow between the vehicle body and the cargo box, effectively reducing air resistance at high speeds and thus lowering fuel consumption. However, the following problems still exist:
[0004] 1. Because different vehicles have different gaps between the cab and the cargo box, the side fairing is a rigid or inflexible structure and cannot adapt to and meet the different gap sizes. In addition, when the vehicle pitches or turns, if the difference between the width of the side fairing and the gap is small, the side fairing will be damaged because it is a rigid or inflexible structure.
[0005] Second, the installation angle or airflow angle of the side fairing is fixed, but the airflow requirements are different at low and high vehicle speeds and at different vehicle speeds. Summary of the Invention
[0006] This application provides a flexible airflow guiding system and control method to solve the problem that the side airflow guides in related technologies are rigid or inflexible structures, which cannot adapt to the different gaps between the cab and cargo box in different vehicles.
[0007] Firstly, a flexible flow guiding system is provided, comprising:
[0008] The first airflow deflector unit is designed to be installed on the top of the cab;
[0009] Two second flow guiding units are respectively located on both sides of the first flow guiding unit in the vehicle width direction and below the first flow guiding unit; the second flow guiding units and the first flow guiding unit enclose and form a flow guiding structure that covers the gap between the cab and the upper vehicle cargo box; wherein, both the second flow guiding unit and the first flow guiding unit include a flexible element and a retractor, the retractor is used to be installed on the cab, one end of the flexible element is wound inside the retractor, and the other end is used to connect to the vehicle cargo box;
[0010] A control device for controlling the winding or unwinding of the flexible component by the retractor according to the vehicle speed.
[0011] The system covers the gap between the cab and the cargo box; that is, the first and second flow guiding units have the same structure, only differing in size or installation position. The flexible components of the first flow guiding unit contact the top side of the second flow guiding unit on both sides in the vehicle width direction to form an integrated, U-shaped flow guiding structure that blocks the gap. The outer surface of the flow guiding structure connects the outer surfaces of the cab and the cargo box into a single unit. In use, the retractor is installed on the side of the cab opposite the cargo box, that is, on the side of the cargo box along the vehicle length direction. The flexible components connect to the top and side sides of the cargo box opposite the cab. When adapting to different vehicles, the control device controls the retractor to extend and retract the flexible components, and the length of the extended flexible components can be varied.
[0012] In some embodiments, the width of the flexible element gradually increases from the end connected to the cab to the end connected to the vehicle cargo box; the flexible element is made of an elastic material.
[0013] In some embodiments, the end of the flexible element that connects to the vehicle cargo box is detachably connected.
[0014] In some embodiments, the control device includes a retractor automatic control module, a vehicle speed acquisition module, and a tension force acquisition module;
[0015] The vehicle speed acquisition module sends the vehicle speed information to the retractor automatic control module.
[0016] The tension force acquisition module is used to detect the shaft load value of the retractor and send the shaft load value to the retractor automatic control module.
[0017] In some embodiments, the control device further includes a manual control knob for the retractor; the manual control knob for the retractor is located on the vehicle dashboard and is signal-connected to the retractor to control the retractor to wind up or unwind the flexible component; the tension force acquisition module is also used to send the shaft load value to the vehicle instrument panel.
[0018] In some embodiments, the automatic control module for the retractor, the tension acquisition module, and the vehicle speed acquisition module are all located on the retractor; or,
[0019] The automatic control module and tension acquisition module of the retractor are installed on the retractor, and the vehicle speed acquisition module is the vehicle ECU. The vehicle speed acquisition module is wirelessly connected to the automatic control module of the retractor.
[0020] In some embodiments, the retractor in the second flow guiding unit is vertically arranged;
[0021] The retractor in the first guide unit is set horizontally.
[0022] In some embodiments, the first guide unit further includes a first position adjustment device, which moves its corresponding retractor in the vehicle height direction;
[0023] The second guide unit also includes a second position adjustment device, which moves its corresponding retractor in the vehicle width direction.
[0024] In some embodiments, the first position adjustment device includes a vertically arranged first guide rail and a first lead screw structure. The first guide rail is provided with a vertically movable first slider. One end of the lead screw in the first lead screw structure passes through the first slider and is threadedly connected to the first slider. The other end is connected to a first drive motor.
[0025] The second position adjustment device includes a horizontally arranged second guide rail and a second lead screw structure. The second guide rail is provided with a vertically movable second slider. One end of the lead screw in the second lead screw structure passes through the second slider and is threadedly connected to the second slider. The other end is connected to a second drive motor.
[0026] Secondly, a control method for a flexible flow guiding system is provided, which includes the following steps:
[0027] Compare the vehicle speed with a set threshold;
[0028] If the vehicle speed is less than or equal to the set threshold, the retractor is controlled to release the flexible component so that the tension force of the retractor on the flexible component is changed to the design value.
[0029] If the vehicle speed exceeds the set threshold, the retractor is controlled to tighten the flexible component, so that the tension force of the retractor on the flexible component is changed to the design value two.
[0030] The beneficial effects of the technical solution provided in this application include:
[0031] This application provides a flexible airflow guiding system and control method. The first airflow guiding unit is located on the top of the cab, and two second airflow guiding units are located on either side of the first airflow guiding unit in the vehicle width direction, and below the first airflow guiding unit. Furthermore, the first and second airflow guiding units have the same structure, both including a flexible component and a retractor. The retractor is located on the cab, with one end of the flexible component wound inside the retractor and the other end connected to the vehicle cargo box. This structure covers the gap between the cab and the vehicle cargo box. When adapting to different vehicles, the retractor can adjust the size of the gap by extending and retracting the flexible component.
[0032] In addition, the retractor can adjust the tension of the flexible component, thereby changing the tension of the flexible component to meet the different airflow requirements of the vehicle at low and high speeds. Attached Figure Description
[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0034] Figure 1 This is a schematic diagram of the structure of the first flow guiding unit provided in an embodiment of this application;
[0035] Figure 2 A front view of the flexible airflow guiding system provided in this application embodiment when installed on a vehicle;
[0036] Figure 3 This is a top view of the flexible airflow system provided in this application embodiment when it is installed on a vehicle.
[0037] In the diagram: 1. Flexible component; 2. Retractor; 3. Automatic control module; 4. Vehicle speed acquisition module; 5. Hook; 6. Vehicle cargo box; 7. Driver's cab. Detailed Implementation
[0038] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0039] This application provides a flexible airflow guiding system and control method to solve the problem in related technologies where the side airflow guide is a rigid or hard structure and cannot adapt to the different gaps between the cab 7 and the cargo box in different vehicles.
[0040] Please see Figures 1-3 A flexible flow guidance system, comprising:
[0041] The first airflow guiding unit is installed on the top of the cab 7;
[0042] Two second flow guiding units are located on both sides of the first flow guiding unit in the vehicle width direction and below the first flow guiding unit; the second flow guiding units and the first flow guiding unit together form a flow guiding structure that covers the gap between the cab 7 and the vehicle cargo box 6; wherein, both the second flow guiding unit and the first flow guiding unit include a flexible element 1 and a retractor 2, the retractor 2 is used to be installed on the cab 7, one end of the flexible element 1 is wound up in the retractor 2, and the other end is used to connect to the vehicle cargo box 6;
[0043] A control device for controlling the winding device 2 to wind or unwind the flexible component 1 according to the vehicle speed.
[0044] With the above configuration, since the first airflow guiding unit is located on top of the cab 7, and the two second airflow guiding units are located on both sides of the first airflow guiding unit in the vehicle width direction, and below the first airflow guiding unit; furthermore, the first and second airflow guiding units have the same structure, both including a flexible component 1 and a retractor 2. The retractor 2 is installed on the cab 7, one end of the flexible component 1 is wound inside the retractor 2, and the other end is connected to the vehicle cargo box 6. This structure covers the gap between the cab 7 and the vehicle cargo box 6; that is to say, the first and second airflow guiding units have the same structure, only differing in size or installation position; specifically, it can be understood as:
[0045] The flexible component 1 of the first flow guiding unit contacts the side of the top of the second flow guiding unit on both sides in the vehicle width direction to form an overall U-shaped shielding gap flow guiding structure. The outer surface of the flow guiding structure connects the outer surfaces of the cab 7 and the vehicle cargo box 6 into a whole.
[0046] When in use, the retractor 2 is installed on the side of the cab 7 opposite to the vehicle cargo box 6, that is, on the side of the vehicle cargo box 6 along the length of the vehicle. The flexible part 1 is connected to the top and side edges of the side of the vehicle cargo box 6 opposite to the cab 7.
[0047] When adapting to different vehicles, the control device controls the retractor 2 to extend and retract the flexible component 1. The extended length of the flexible component 1 can vary, thus accommodating gaps of different sizes. Since the gaps differ, they are reflected in the distance between the cab 7 and the cargo box 6 along the vehicle's length direction. The structure of the retractor 2 can refer to the structure in CN 111152632A, but the specific dimensions of the retractor can be set accordingly as needed.
[0048] Furthermore, the airflow guiding structure described above has different airflow requirements at different vehicle speeds. By acquiring the vehicle speed, the control device can also adjust the tension of the flexible component 1 by controlling the retractor 2, thereby changing the tension of the flexible component 1 and meeting the different airflow guiding requirements of the vehicle at low and high speeds, thus achieving dynamic adjustment. This effect can be understood as: different speed ranges correspond to different tensions, and different tensions have different airflow guiding effects. Alternatively, it can simply distinguish between high and low speeds, with a set speed below a certain speed being considered low speed and a set speed above a certain speed being considered high speed, with low speed and high speed each corresponding to a different tension.
[0049] In some preferred embodiments, the gap provides full coverage, resulting in a well-defined flow-guiding structure with good transitional flow control. This addresses the issue that rigid or inflexible side fairings cannot accommodate gaps of varying sizes. Furthermore, during vehicle pitching or turning, if the difference between the width of the side fairing and the gap is small, the rigid or inflexible structure could damage the side fairing. The following design addresses this:
[0050] The width of the flexible component 1 gradually increases from the end connected to the cab 7 to the end connected to the cargo box 6 of the vehicle; the flexible component 1 is made of elastic material.
[0051] Among them, the width of the end of the flexible component 1 connected to the cab 7 is equal to the width of the top of the cab 7 in the vehicle width direction, and the width of the end of the flexible component 1 connected to the vehicle cargo box 6 is equal to the width of the corresponding side of the cab 7. That is to say, the top edge and the two sides of the side of the cab 7 opposite to the vehicle cargo box 6 are adapted to the width of the corresponding end of the flexible component 1; the top edge and the two sides of the side of the vehicle cargo box 6 opposite to the cab 7 are adapted to the width of the corresponding end of the flexible component 1.
[0052] The reason for the above settings is that the cross-sectional area of the vehicle cargo box 6 is generally larger than that of the cab 7. Therefore, the flexible part 1 is not horizontal or vertical after installation, but has a certain tilt angle. Thus, the change in width has a good connection transition effect. In addition, the flexible part 1 made of elastic material has the effect of stretching to a certain extent in all directions. There is no need to worry about the flexible part 1 being torn when the vehicle pitches or turns.
[0053] Furthermore, to facilitate the connection between the flexible component 1 and the vehicle cargo box 6, the end of the flexible component 1 connected to the vehicle cargo box 6 is detachable. That is, the flexible component 1 is provided with a hook 5, which can be connected to the vehicle cargo box 6 when the vehicle is moving.
[0054] In some preferred embodiments, the specific structure and function of the control device are described in detail:
[0055] The control device includes a retractor automatic control module 3, a vehicle speed acquisition module 4, and a tension acquisition module;
[0056] The vehicle speed acquisition module 4 sends the vehicle speed information to the retractor automatic control module 3; the tension force acquisition module is used to detect the shaft load value of the retractor 2 and send the shaft load value to the retractor automatic control module 3.
[0057] The system features an automatic control mode during operation. Specifically, the automatic control module 3 of the retractor acquires the vehicle speed and shaft load values through the vehicle speed acquisition module 4 and the tension acquisition module, respectively. When the vehicle speed is less than or equal to a set threshold, the retractor 2 is controlled to extend and retract the flexible component 1, thereby changing the tension force of the retractor 2 on the flexible component 1 to the design value one. If the vehicle speed is greater than the set threshold, the retractor 2 is controlled to tighten the flexible component 1, thereby changing the tension force of the retractor 2 on the flexible component 1 to the design value two. This achieves automatic control.
[0058] Of course, this system also has a manual control mode. To achieve this, the control device also includes a manual control knob for the retractor. The manual control knob for the retractor is located on the vehicle dashboard and is connected to the retractor 2 via a signal to control the retractor 2 to wind up or unwind the flexible component 1. The tension acquisition module is also used to send the shaft load value to the vehicle instrument panel.
[0059] In the manual adjustment compartment, the driver controls the operation of the retractor 2 by rotating the retractor control knob, and judges whether the required tension has been adjusted by checking the shaft load value displayed on the vehicle's instrument panel.
[0060] Furthermore, there are several possible layout options:
[0061] The first type has an automatic control module, a tension acquisition module, and a vehicle speed acquisition module all installed on the retractor 2.
[0062] In the second configuration, the automatic control module and tension acquisition module of the retractor are located on the retractor 2, while the vehicle speed acquisition module is the vehicle ECU. The vehicle speed acquisition module is wirelessly connected to the automatic control module of the retractor. This means that obtaining the vehicle speed does not require a separate sensor, thus saving costs.
[0063] In some preferred embodiments, it has been found in practice that the inclination of the outer surface of the formed flow guiding structure and the length of the transition surface are related to the flow guiding effect; therefore, the following settings are adopted:
[0064] The retractor 2 in the second flow guiding unit is set vertically; the retractor 2 in the first flow guiding unit is set horizontally.
[0065] The first guide unit also includes a first position adjustment device, which moves its corresponding retractor 2 in the vehicle height direction;
[0066] The second guide unit also includes a second position adjustment device, which moves its corresponding retractor 2 in the vehicle width direction.
[0067] The first position adjusting device includes a vertically arranged first guide rail and a first screw rod structure. A first slider that moves vertically is provided on the first guide rail; one end of the screw rod in the first screw rod structure penetrates through the first slider and is threadedly connected to the first slider; the other end is connected to a first driving motor.
[0068] The second position adjusting device includes a horizontally arranged second guide rail and a second screw rod structure. A second slider that moves vertically is provided on the second guide rail; one end of the screw rod in the second screw rod structure penetrates through the second slider and is threadedly connected to the second slider; the other end is connected to a second driving motor.
[0069] By means of the first position adjusting device and the second position adjusting device, the position of the corresponding retractor 2 can be changed, thereby changing the length of the transition part actually participating in the diversion; it can be understood that when the retractor 2 of the first diversion unit is located on the top edge of the cab 7, the length of participating in the diversion is the largest, and it gradually decreases when moving downward; when the retractor 2 of the second diversion unit is located on the side edge of the cab 7, the length of participating in the diversion is the largest, and it gradually decreases when moving towards the central axis of the vehicle.
[0070] This application also proposes a control method for a flexible diversion system, which includes the following steps:
[0071] Compare the vehicle speed with a set threshold value;
[0072] If the vehicle speed is less than or equal to the set threshold value, control the retractor 2 to unwind and wind the flexible member 1 so that the tension force of the retractor 2 on the flexible member 1 changes to a first design value;
[0073] If the vehicle speed is greater than the set threshold value, control the retractor 2 to tighten the flexible member 1 so that the tension force of the retractor 2 on the flexible member 1 changes to a second design value.
[0074] Of course, this control method is: only distinguish between high and low speeds. Below a certain set vehicle speed is low speed, and above a certain set vehicle speed is high speed. Low speed and high speed respectively correspond to a tension force.
[0075] That is, the retractor 2 is set with two tension forces, namely the tension Z1 at low speed and the tension Z2 at high speed, Z1 < Z2; a set vehicle speed judgment value V0 is set;
[0076] When the vehicle speed of the whole vehicle V ≤ V0, the retractor tension controller sets the tension force to Z1; in the low-speed state, the influence of the flexible member 1 on the wind resistance of the whole vehicle is small, and the probability of the trailer or cargo box pitching and rotating is large. A smaller retractor tension can meet the requirements of this working condition
[0077] When the vehicle speed of the whole vehicle V > V0, the retractor tension controller sets the tension force to Z2;
[0078] At high speeds, flexible component 1 has a significant impact on the overall vehicle's wind resistance. High tension keeps flexible component 1 taut, resulting in lower wind resistance for the entire vehicle. Simultaneously, at high speeds, the vehicle operates well, and the elasticity of flexible component 1 can accommodate minor pitching and turning movements of the trailer.
[0079] Of course, there is another control method, specifically:
[0080] Different target speed ranges are preset; the different target speed ranges are arranged in ascending order; each target speed range corresponds to a set tension force;
[0081] The actual vehicle speed is compared with different target vehicle speed ranges. If it falls within one of the target vehicle speed ranges, the tension force corresponding to that range is adjusted as the target value so that the tension force of the retractor 2 on the flexible part 1 is changed to the target value.
[0082] Both of the above methods are dynamic adjustment methods, and both fall within the scope of this application.
[0083] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.
[0084] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0085] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A flexible flow guiding system, characterized in that, It includes: The first flow guiding unit is used to be installed on the top of the cab (7); Two second flow guiding units are respectively located on both sides of the first flow guiding unit in the vehicle width direction and below the first flow guiding unit; the second flow guiding units and the first flow guiding unit enclose to form a flow guiding structure that covers the gap between the cab (7) and the vehicle cargo box (6); wherein, the second flow guiding unit and the first flow guiding unit each include a flexible element (1) and a retractor (2), the retractor (2) is used to be installed on the cab (7), one end of the flexible element (1) is wound in the retractor (2), and the other end is used to connect with the vehicle cargo box (6); The control device includes a retractor automatic control module (3), a vehicle speed acquisition module (4), and a tension force acquisition module; the vehicle speed acquisition module (4) sends vehicle speed information to the retractor automatic control module (3); the tension force acquisition module is used to detect the shaft load value of the retractor (2) and send the shaft load value to the retractor automatic control module (3); the retractor automatic control module (3) is used to control the retractor (2) to rewind or unwind the flexible part (1) according to the vehicle speed information, and to make the tension force of the retractor (2) on the flexible part (1) equal to the designed shaft load value.
2. The flexible flow guiding system as described in claim 1, characterized in that: The width of the flexible component (1) gradually increases from the end connected to the cab (7) to the end connected to the cargo box (6); the flexible component (1) is made of elastic material.
3. The flexible flow guiding system as described in claim 1, characterized in that: The flexible component (1) is detachably connected to the end of the vehicle cargo box (6).
4. The flexible flow guiding system as described in claim 1, characterized in that: The control device also includes a manual control knob for the retractor; the manual control knob for the retractor is located on the vehicle dashboard and is signal-connected to the retractor (2) to control the retractor (2) to retract or unwind the flexible component (1); the tension acquisition module is also used to send the shaft load value to the vehicle instrument panel.
5. The flexible flow guiding system as described in claim 1, characterized in that: The automatic control module, tension acquisition module, and vehicle speed acquisition module of the retractor are all installed on the retractor (2); or, The automatic control module and tension acquisition module of the retractor are installed on the retractor (2). The vehicle speed acquisition module is the vehicle ECU. The vehicle speed acquisition module is wirelessly connected to the automatic control module of the retractor.
6. The flexible flow guiding system as described in claim 1, characterized in that: The retractor (2) in the second flow guiding unit is vertically arranged; The retractor (2) in the first flow guiding unit is set horizontally.
7. The flexible flow guiding system as described in claim 6, characterized in that: The first guide unit also includes a first position adjustment device, which moves its corresponding retractor (2) in the vehicle height direction. The second guide unit also includes a second position adjustment device, which moves its corresponding retractor (2) in the vehicle width direction.
8. The flexible flow guiding system as described in claim 7, characterized in that: The first position adjustment device includes a vertically arranged first guide rail and a first lead screw structure. The first guide rail is provided with a vertically movable first slider. One end of the lead screw in the first lead screw structure passes through the first slider and is threadedly connected to the first slider. The other end is connected to a first drive motor. The second position adjustment device includes a horizontally arranged second guide rail and a second lead screw structure. The second guide rail is provided with a vertically movable second slider. One end of the lead screw in the second lead screw structure passes through the second slider and is threadedly connected to the second slider. The other end is connected to a second drive motor.
9. A control method for a flexible flow guiding system as described in any one of claims 1-8, characterized in that, It includes the following steps: Compare the vehicle speed with a set threshold; If the vehicle speed is less than or equal to the set threshold, the retractor (2) is controlled to release the flexible part (1) so that the tension of the retractor (2) on the flexible part (1) is changed to the design value one; If the vehicle speed is greater than the set threshold, the retractor (2) is controlled to tighten the flexible part (1) so that the tension of the retractor (2) on the flexible part (1) is changed to the design value two.