WO2003059707A1

WO2003059707A1 - Variable force limiter for safety belts

Info

Publication number: WO2003059707A1
Application number: PCT/SE2003/000055
Authority: WO
Inventors: Bo Swedenklef
Original assignee: Bo Swedenklef
Priority date: 2002-01-16
Filing date: 2003-01-16
Publication date: 2003-07-24
Also published as: SE0200100L; AU2003235617A1; SE521720C2; SE0200100D0

Abstract

A safety system for safety belts in a vehicle containing a variable power limiter with the objective to regulate the chest belt loading on the occupant in a collision. The power limiter is located in conjunction to the belt reel of the chest part of the safety belt, containing of an electric controlled unit that is regulated by a number of sensors and a control unit located in the vehicle. In a frontal collision will the safety system regulate the loading acting on the occupants neck and chest. The system is also designed to efficiently distribute the decelerating forces generated by the occupants kinetic energy between the safety belt, airbag and vehicle seat.

Description

Variable Force Limiter for Safety Belts

The inventions technical area

The invention is a safety system for safety belts in vehicles. The system is especially suited to regulate and absorb forces that are applied to an occupant's torso from the safety belt. In a frontal collision the safety system will regulate forces applied to the neck and chest and also reduce injury to the occupant.

Known methods

Modem cars are equipped with effective crumple zones, which are located mostly in the vehicle's front and rear. Around the passenger compartment there is a strong protective cage, which is in place^" to prevent that the passenger compartment is deformed in a collision. The evolution of cars is moving towards reduced weight and size, mostly out of environmental and cost reasons. This makes the demands on vehicle crumple zones much higher. For this reason vehicle safety belts have been evolving to become more effective. An important progress has been deferent types of pre tensioning of safety belts. The purpose of these is to remove the slack that is present in safety belts normally. In a collision the pre tensioning system is activated and the occupant is pulled towards the seat. This reduces the risk for sliding under the lap belt and increases braking distance for both the chest and lap portions of the safety belt. Development is underway to introduce four point belts, which will increase the effectiveness further in frontal collisions and roll over accidents. If the four point safety belt system is installed in the seat the effectiveness of the safety system is increased further. To further reduce the likely hood of injury in collisions the vehicles are equipped with airbags. Airbags mostly protect the chest and head. Recently manufacturers have started to coordinate the actions of safety belts and airbags. As an example airbags are inflated one or two stages depending on the collision energy. Collision energy is mostly dependant on the vehicle collision speed and the occupant's weight. Modem safety belts have been constructed to start the deceleration of the occupant's torso as early as possible. This is done mostly to avoid impact of the head and torso, which could inflict life threatening injury in a collision. This progression has resulted in increased strain on the neck in frontal collisions. This is dependent on the relative movements between the neck which is affected by it's mass and the torso, which is pulled towards the seat by the seat belt pre tensioning system described above. Humans are partly biologically unsuited for this progression. The neck is the part of the spine that can handle stain least. This relationship between our biological predisposing and the progression of safety systems has resulted in that neck injury in collisions still is a considerable problem. As an example 30% of whiplash injury are caused in frontal collisions. Car manufactures and their subcontractors have in recent years introduced power limiters that usually operates on the roll up mechanism for the lap belt. This construction is most often made of a metal that is deformed during the collision. This deformation makes the safety belt more giving. The metal functions as a power limiter and start giving after when the safety belt has been subjected to about 4000 N . In the belt there is some minor stretching of a few percent.

Problem with known methods

Insurance statistics from both USA and Sweden indicated that both neck, lower back and leg still is a considerable problem in spite of major improvements in collision safety. Foremost lengthy neck problem resulting from collisions are common. No clear scientific medical reason have been established to determine what causes whiplash injuries. Several theories has been presented that would indicate that if the neck is subjected to very fast and sometimes high energy pushing forces under vertical compression of the neck this would cause whiplash injuries. Pushing forces suspected injury likelihood is valid in collisions from all directions, side collisions and the classic rear collision. This means that lighter humans often children and women does not receive the same protection from power limiters in a frontal collision then heavier persons would get. Women, older people and children also have weaker muscles and ligaments in the neck. Children's heads are also proportionally bigger and heavier as percentage of total body weight. In addition taller people of both sexes runs a higher risk of developing a whiplash injury in a collision. Possible reason for this may be that taller people have a more slumped down driving position. Whiplash injury with long time consequences are more common in women as compared with men if you correct for driving distance and accident frequency. Safety belt is the most important protection system. It absorbs the majority of collision energy in a frontal collision. The force is mainly distributed over the pelvis and chest. In frontal collisions the body will continue forward in the direction of travel, at the same time the safety belt is pulled tight across the upper body and pelvis. This results in that the neck will move forward in relation the upper body. It is probable that the risk for whiplash injury is increased if this occurs early in the accident, when the occupant is sitting slightly slumped down in the seat and the head forward. Studies of seating positions have shown that we are sitting slouched with backward rotated pelvis and poorly tightened lap belt in worn/compressed seating surfaces when the vehicle has 100-150,000 km and the car/seat has still 50% of its potential life left. Today's system with safety belt pre-tension that by pulling torso and pelvis gives a powerful backwards tilting of the pelvis when it is activated in a collision. This relationship increases the chance of so called "flexion" of the joints in the back, especially in the lower back. Joints can tolerate less force in their outer range on movement as compared to more central force applied to the joint. The risk of tears in ligaments increases on the pull side and compression damage (for example: micro fractures on discs and joints) are increased on the compression side. The above described mechanical system of power limiters does not take into account the occupants weight or seating position and thereby the body's ability to tolerate the collision forces.

The part of the back that handles mechanical forces the best is the pelvis. Safety belts, airbags and vehicle seats will in the future work together in a more and more sophisticated way. They will do this to distribute deceleration forces between the three main safety systems nearest to the person. Consumer and authorities are increasing their demands on protection in higher collision velocities and higher g-loading, this is putting great demands on the safety systems effectiveness. To be able to meet these demands it is required that the safety systems are quick, intelligent and adaptable to the environment in a specific collision. The inventions purpose and uniqueness

The invention in question has the purpose of eliminate the above named problems that exits in current systems and to create a safer collision system for safety belts in cooperation with the vehicle's airbags. The purpose is to create a new and more effective deceleration system in frontal collisions for occupants traveling in vehicle seats were the safety belts deceleration ability is regulated by a electronically regulated deceleration mechanism placed in conjunction with spool up mechanism or in conjunction with the D-ring portion of the chest belt.

Short summary of the technology involved

Mechanical power limiters in the safety belt spool up mechanism is previously known from among others US 5,533,756, US 5,547,143, US 5,626,306 and US 667,246. These inventions have mechanical power limiters that can be modified during manufacturing and be set at an interval between 50-2000 lbs (227-9080 Nm). They can only be set during manufacturing and can't be changed thereafter. Due to the fact that they are not adjustable, they can only take into limited consideration the occupants weight, vehicle speed and deceleration forces. This means that lighter persons (women and children) have an increased chance of injury. Variable control of deceleration forces in the chest portion of the safety belt in the moments after the collision is limited in today's systems.

Short description of included drawings

On the drawings:

Figure 1 Side view, overall picture of an occupant in a vehicle seat equipped with the safety systems included components.

Figure 2 Drawing of roll-up mechanism for chest belt and included variable power limiter. Figure 3 Drawing of the D-ring and included power limiter.

Detailed description of the invention

Figure 1 contains a vehicle seat (1) and a steering wheel (2) equipped with an airbag

(3). The driver has a safety belt (4) of the three point type. The belt consists of a waist portion (5) and a chest portion (6) of the safety belt (4). The safety belt (4) is equipped with a fastening mechanism (7) for the safety belt (4) to the vehicle chassis (8). Between the chassis and the fastening mechanism (7) is a safety belt pre tensioning system (9). The vehicle is also equipped with one or more sensors that whose purpose it is to determine the vehicle collision speed (10), deceleration forces (11), rate of safety belt spool out (12), seats distance from possible impact surfaces (13), occupants weight and seating position (15). The sensor for safety belt spool out rate (12) can consist of the spool up mechanism (17) monitored by optical, inductive or mechanical sensor. Sensors for the seat (1) distance from impact surfaces (13) are likely located in the seats or their sub structures and also in the steering column on vehicles with adjustable steering wheels. Sensors to determine the occupants weight (14) are placed in respective seat (1). Sensors for the occupants seating position (15) in the seat (1) can be mechanically sensitive sensors placed in the backrest. It is also possible that infrared technology is used to determine seating position (15). Infrared sensors can be placed in several different location for example seat, door or ceiling. Infrared sensors can also determine the occupant's height. Impact surfaces for occupants in the front seat are steering wheel (2) and instrumentation panel (36). For occupants in the backseat the impact surface is the backrest of the front seat (1). Information from these sensors are sent to a control unit (16) that will send electrical signals to the chest belts variable power limiter (29) that is located in conjunction with the spool up mechanism (17). In a frontal collision the safety belt pre tensioning system (9) will activate and the slack in the safety belt will be reduced. The length of pull from the safety belt pre tensioning system (9) is 100-150 mm dependent on construction. The system is activated and starts to pull approximately 5-10 ms after the collision has been detected by the vehicles collision sensors (1) or other sensor in the vehicles front. When the safety belt pre tensioning system (9) is activated the chest belt (6)spool up mechanism (17) will lock the chest belts spool out. Safety belt (4) can have several pre tensioning systems (9) placed in either waist belt (5) outer mounting (19) or in the chest belt (6) spool out mechanism (17). The sensors information is computed in the control unit (16) that provides variable electrical control of a very fast electrical motor (20) whose purpose is dependent on deceleration protection needed by the occupant to regulate the speed, timing and amount of release of the chest safety belt. Outgoing signals from the control unit (16) to the electrical motor (20) can be in analog or digital form. As a rule you can say that light persons who are sitting with good seating positions and are in frontal collisions with relatively low energy would produce low g-forces. The variable power limiter will give the lighter occupant more belt spool out and less resistance from the chest belt (6). The opposite with heavy occupants who are sitting in poor seating position in frontal collisions with high energy and high g-forces, in this instance the variable power limiter will spool out a small amounts of the chest belt (6) with very high resistance. The above mentioned safety system is built around active control of the spool out of the chest portion of the safety belt (6). When loads are reduced on the chest belt (6) the loads will increase on the airbags (3) and seats (1). The force in the airbag (3) is regulated in coordination with the spool out of the chest belt (6), this function is controlled by the control unit (16). Figure 2 illustrates the safety belt (4) spool up mechanism (17) and associated case (21), spool out stop or acceleration stop (22) and the belt roll (23). Included is a cog system (24) and fast electrical motor (20). The cogwheel (27) is mounted on the belt roll (23) lengthwise axis. The cog sysiem (24) other part consists of the motor axel (28). The electric motors (20) energy demand can supplied fast from a spare energy source (26), that could consists of a battery or rechargeable capacitors or a combination of these, that are equipped with a electronic controller for pulsed energy supply for effective and fast control of the electrical motor (20). Figure 2 also demonstrates approximate ratio of the cog system (24) where the electrical motors (20) speed is reduced via a worm gear assembly. The rise of the cogs on the cog wheel (27) from the electrical motors outgoing axel (28) is such that belt spool -out from the belt roll (23) is impossible unless the electrical motor (20) is activated by the control unit

(16). If the variable and electrically controlled power limiter is combined with a mechanical power limiter available on the market today (33) you would have a backup system should the electrical system fail. The inventions advantages

One of the major advantages of the invention is that the deceleration forces from the safety belt that stresses chest and neck in frontal collisions can be regulated dependent on the occupant's weight, safety belt amount of spool out, seats distance from possible impact surfaces, collision speed and vehicle deceleration. This means that the force can be distributed over a longer time and thereby the stress on neck and chest can be distributed more evenly and lower g-forces under the collisions beginning stages (0-60 ms). In additions the invention will lead to a more even g-load throughout the entire collision. This invention will provide a more effective coordination of the deceleration achieved by airbag and safety belt.

Possible modifications of the invention

In figure 3 a possible modification of the electrical variable power limiter (29'). The power limiter (29') consists of the motor (20') and its outgoing axel (28'), the cog system (24') where one part consists of a threaded axel (28') and the other part a threaded holder (32). The safety belts (4) D-ring (30) is loosely tied to the holder (32) by a connector (31). The holder (32) is in its turn connected by a connector (34) and

(34') to the vehicle B-post (35). All of figure 3 mentioned arrangement is normally mounted on a slider for individual height adjustment of the chest belts (6) D-ring (30). When the safety system is activated,, the D-ring (30) and holder (32) is forced towards the vehicle floor by impulses from the control unit (16) that will drive the motor (20'). Thereby the chest belt (6) deceleration force on occupant in frontal collisions will be reduced. The sensors (10-15) and control unit (16) are described under the detailed description of the invention and has the same ftmction in this modification of the invention. Under the detailed description in figure 1 and 2 and also in figure 3 has a cog shape ϋϊ the cog system (24) described as impossible to spool out the safety belt unless the motor (20) is activated. If the cogs are geometrically is angled so that the motors axel (28') is equipped with a worm gear where the angles of the cogs are less than a right angle against the lengthwise motor axis, then the motor (20) instead would a have braking effect when activated. Today's vehicles most commonly have 12 V electrical systems. Cars in the future are being developed with higher voltages, 42 V has been suggested as future standard. This is also advantageous for this invention. This would add up to electrical motors with small size could develop more effect and thereby offer more effective variable deceleration of the occupants. If the motor (20) is not activated, safety belt spool out from the spool out mechanism will occur.

Another possible modification of the invention is that a bipolar electrical motor (20) can be used to regulate the pull back of the chest belt (6) in the vehicle pre collision phase. This would make possible pre tensioning the chest belt (6) if the occupant is not in good contact with the seat back of the seat. This would mean that a maximal deceleration distance is achieved with a less violent pull than if a safety belt pre tensioning system (9) is used to mo e ⁺ > body "f the oc^cupant in the collisions beginning stages. After the system has been activated in a primary collision the system can provide pull back force to protect from a possible secondary collision. Pull back of the safety belt (4) as above described is a known technique and can be activated by hard pressure on the brake pedal or different kinds of collision detecting warning systems (for example, radar).

Another possible modification of the invention is seat mounted safety belts (4) and then the variable electrical controlled power limiter (29) is mounted in the vehicle seat (1) instead of the vehicle B-post (35). The power limiter (29) is suitable for 4 or 6- point belts especially in combination with the above mentioned pull back function and in so called roll over accidents. In motor sport this type of accidents happen frequently. Power limiter in combination with 4-point safety belt makes it possible to effectively control the body's deceleration against the airbag (3). The 4-point belt will reduce the twisting of the body and thereby give a more effective use of the airbags (3) deceleration ability, due to the fact that the chest and head will hit more exactly in the center of the airbag.

Also some adjustable electromagnetic devices can possibly substitute the function of the electrical motor (20) in the variable power limiter (29).

Claims

Patent claims

1. Safety system for vehicles, including a vehicle seat (1) safety belt (4), the safety belt includes a waist portion (5) and a chest portion (6), which includes at least one spool up mechanism (17) and one with the belt cooperating power limiter (29), and at least one pre tensioning system (9), whereby the function of the mentioned power limiter is controlled by one control unit (16) which is connected to sensors (10-15) and whose purpose it is to detect a number of parameters in conjunction with a collision, characterized therein that the power limiter (29) includes a fast electric motor (20) with a outgoing axle (28) that has a male thread, who in its turn are connected to cogs on a cog wheel (27) who is connected with a safety belt roll (23) and its spool up mechanism (17), whereby the thread and the cogs angle of inclination is such that spool out of the safety belt is impossible unless the motor is activated.

2. Safety system for vehicles, including a vehicle seat (1) safety belt (4), the safety belt includes a waist portion (5) and a chest portion (6), and\ consists of the safety belt (4) chest portion (6), D-ring (30) whose purpose it is to hang on the B-post in the vehicle, and a power limiting system (29'), and at least one pre tensioning system (9), whereby the function of the power limiting system (29') is controlled by a control unit (16) who is connected to sensors (10-15) whose purpose it is to detect a number of parameters in conjunction with a collision characterized therein that the power limiter (29') includes a fast electric motor (20') with a outgoing axle (28') that has a male thread, who is in contact with a female thread in a holder (32) in which the D-ring (30) connected but movable, whereby the angle of inclination of the thread is such that pull down of the D-ring and slide though of the belts chest portion (6) is impossible unless the motor

(20') is activated.

3. The safety system according to patent claim 1 or 2, characterized therein that the control unir(16) is designed to control the electrical motor (20, 20') with variable effect.

4. The safety system by any of the preceding claims, characterized therein that the sensors (10-15) is designed to detect several of the following parameters; vehicle collision speed (sensor 10), vehicle deceleration (sensor 11), chest belt (6) amount of spool out (sensor 12), vehicle seats (1) distance from impact surfaces (sensor 13), the occupants weight (sensor 14) and the occupant seating position in the vehicle seat (sensor 15).

5. The safety system by any of the preceding claims, characterized therein that it works in coordination with the vehicles airbags (3).