The present invention concerns a vibration arrangement for a vehicle steering wheel .

The present invention is included as an important part of an active safety system for motor vehicles. In such a system, there are included a detection component, which detects situations of impending danger, and a calculation component, which raises an alarm. This alarm takes place in a warning component, which warns the driver when danger has been detected. The warning component may use a steering wheel vibrator according to the invention. The development of active safety systems for motor vehicles has focused on not only the detection of traffic dangers but also on suitable driver alarms in various situations of danger. The alarms that have been tested have been visual, acoustic, and haptic alarms, and combinations of these.

Different types of alarm may prove to be most suitable and effective, depending on the traffic situation.

Visual alarms can be used in a traffic situation in which the driver is fully awake and alert, but become completely inef- fectual if the driver has fallen asleep or is in the process of falling asleep. Acoustic alarms are less appropriate in situations in which the driver has impaired hearing or in which the surrounding noise level is high. Both acoustic and haptic alarms can be used in cases in which the driver falls into a short-lived or unbroken sleep. A haptic alarm in the form of mechanical vibration in the steering wheel has the major advantage over both an acoustic alarm and a haptic alarm located in other locations, such as in the seat belt or in the driver's seat, in that the feeling of vibration in the hand and fingers of the driver leads to an immediately and distinct grip on the steering wheel, while the driver is at the same time awakened, as has been described in WO 2007/136 338 Al . The present invention uses this knowledge. Many different ways of creating vibration in a vehicle steering wheel are known. Arrangements based on electromagnetic or piezoelectric vibrators have been described with the installation of such between a fixed point in the vehicle and the shaft of the steering wheel, or between the centre part of the steering wheel and its spokes, or between the spokes of the steering wheel and its ring. Imbalance motors are known, whose installation is normally in direct physical contact with some part of the supporting metal structure of the steering wheel, for example a spoke, or for installation onto the steering wheel. A further previously known arrangement uses piezoelectric layers at some part of the outer cover of the steering wheel, with piezoelectric crystals or piezoelectric tape. In order for the vibration to be experienced around the complete ring of the steering wheel, it has been suggested that the complete metallic part of the steering wheel be placed into an oscillation condition. This requires, however, an equivalent electromechanical power in a vibrator, in order to achieve the vibration. Furthermore, the complex geometry of the steering wheel leads to vibration in several directions, which, together with different resonance frequencies in different parts of the steering wheel, easily creates phase distortions and irregular oscillation modes. It is therefore very complicated to produce vibration that corresponds to a desired frequency in the surface of the steering wheel.

Experience shows, in addition, that the maxima of amplitude vary in an undesired manner around the ring of the steering wheel when the known methods of installing vibrators are used . The steering wheel vibrator is primarily suited to be an integral part of a vehicle steering wheel, but it can be designed also to be a part of externally mounted supplementary equipment on a vehicle steering wheel such as in a cover, which can contain also a detection component and a calculation component.

The present invention consists of a vibration arrangement that removes the disadvantage of a large vibration body, which the metal structure of the steering wheel is, and thus removes the requirement for a powerful vibrator, the disadvantage of poor distribution of vibration in the irregular body, and the disadvantage of oscillatory interference. Furthermore, the present invention offers the possibility of achieving a desired vibratory effect in the surface of the steering wheel independently of the design of the steering wheel .

The present invention thus relates to a vibration arrangement for a vehicle steering wheel comprising one or several vibrators at or in the ring of the steering wheel, which steering wheel has a ring with a metallic part that is mechanically coupled to a steering wheel hub and where at least one vibrator is present arranged to produce a vibration frequency, and is characterised in that the vibrator is fixed attached to a vibration body, in that the vibration body is an extended element, in that the vibration body is arranged to lie around the complete ring of the steering wheel, or around a major part of it, without being in contact with the metallic part of the ring of the steering wheel, and in that the vibration body is arranged to be positioned close to the external surface cover that a driver grips when driving the vehicle.

Figure 1 shows schematically a vibration arrangement accord- ing to the invention for a vehicle steering wheel comprising one or several vibrators at or in the ring of the steering wheel. Figure 1 shows a vibration body 1 and a vibrator 2 arranged to be electrically connected to a source of voltage. The vehicle steering wheel has a ring with a metallic part that is mechanically coupled with a steering wheel hub. It is normal that the metallic part of the ring of the steering wheel is connected to spokes that pass to a steering wheel hub. At least one vibrator is present arranged to produce an vibration frequency in the vibration body.

The vibrator 2 is, according to the invention, fixed coupled to the vibration body 1. The vibration body 1 is an extended element arranged to lie around the complete ring of the steering wheel, or around a major part of it, without being in contact with the said metallic part of the ring of the steering wheel. The vibration body 1 is arranged to be posi- tioned close to the external surface cover that a driver grips when controlling the vehicle.

According to one preferred embodiment, the vibration body 1 is constituted by a rod, as is shown in Figure 1.

It is furthermore preferred that the extended vibration body 1 has two free ends and that the vibrator 2 is fixed attached at one of these ends. In an alternative design, the vibrator 2 is attached at the two ends of the extended vibration body 1 such that a closed ring is formed. This is the design according to Figure 1.

According to a further alternative, the extended vibration body 1 is a closed ring at which the vibrator 2 is attached.

It is appropriate that the vibrator 2 be an imbalance motor with a vibration body, joined to form a single unit. The vibration body or bodies is or are, according to one preferred embodiment, of metal. In the primary design of the invention, in which one or several vibrators are integrated with the steering wheel, the diameter of each vibration body ring is less than the outer diameter of the steering wheel and greater than its inner diameter.

Thus the vibration body is mechanically fixed coupled with an imbalance motor that is encapsulated in a suitable manner. A vibration arrangement according to the invention contains at least one ring-shaped vibration body, hereunder called the "vibrator ring", which is fixed united with the cover of at least one imbalance motor. The vibration arrangement is an integrated part of a vehicle steering wheel and is installed inside the ring of the steering wheel close to its outer cover.

In another design of the arrangement, which differs in principle, the vibrator ring and its encapsulated imbalance motor are located inside a specially designed cover, and it is intended that it be possible to mount this cover onto an existing steering wheel in a motor vehicle. The integration of the steering wheel vibrator with the cover can be designed in a similar manner in order to allow vibration even when hard hand pressure influences the cover.

The two designs of an arrangement according to the invention, which differ in principle, are based on the same vibration arrangement comprising an imbalance motor and an open or closed vibrator ring coupled with it. It is an aspect of the solution and the invention that the ring can be designed with respect to material, mass and cross-sectional form in such a manner that the desired amplitude is achieved at a selected degree of imbalance and a selected rate of revolution of the motor, which determines the applied vibration frequency. The invention will be described in more detail below, partly in association with embodiments shown in the attached drawings .

- Figure 1 shows a freed steering wheel vibrator according to the invention,

- Figure 2 shows a feature of this in an enlarged view.

- Figure 3 shows a vehicle steering wheel with a steering wheel vibrator according to the invention,

- Figure 4 shows a cross-section detail of this. Figure 3 shows the steering wheel of a passenger vehicle, but the invention is valid in just as high a degree for the steering wheel of a commercial motor vehicle.

- Figures 5-7 show schematically installation variants in a vehicle steering wheel.

- Figure 8 shows a steering wheel vibrator according to the invention mounted in a cover for a steering wheel, and

- Figure 9 shows a cross-section detail of this.

The idea of the invention is to be able to generate in an efficient and controlled manner haptic vibration signals around the complete ring of the steering wheel to the driver of a motor vehicle, where the driver's hands and fingers grip the steering wheel. Figure 2 shows the central parts of the steering wheel vibrator, where 21 denotes an imbalance motor, 22 denotes an imbalance element, 23 denotes a protective cover, 24 denotes electrical conductors, and 3 denotes the vibrator ring of the steering wheel vibrator.

The motor unit 2 of the steering wheel vibrator in Figures 1 and 2 is mechanically fixed united with the vibrator ring 3 through brazing or other known technology, such that the motor shaft of the imbalance motor is parallel with the tan- gential direction of the vibrator ring 3 at the point of attachment . As is shown in Figure 2, the motor unit 2 comprises the motor 21 with its displaceable imbalance element 22 and a surround ^¬ ing capsule 23, which is fixed united with the motor 21 and so designed that the imbalance element 22 can rotate freely.

The cross-sectional area of the ring 3 shown in Figures 1 and 2 is circular, but it may also have another form and it may be selected, for example, such that the desired vibration is primarily directed towards the normal of the external surface cover of the steering wheel after installation. The ring should oscillate most easily in a direction that is perpendicular to the longest side of the cross-sectional area.

In Figure 3, the reference number 4 denotes the steering wheel of a motor vehicle, 41 its central part, 42 its spokes,

43 the ring of the steering wheel, 44 the metallic supporting structure of the steering wheel, and 45 a soft outer cover of the steering wheel, which cover is fixed at the metallic supporting structure of the steering wheel.

The outer cover 45 of the steering wheel has been drawn in Figure 3 with full lines and the metal supporting structure

44 of the steering wheel with dashed lines, while the steer ^¬ ing wheel vibrator 1 with its motor unit and vibrator 3 have been drawn with dot-dashed lines. The steering wheel in this design is provided with a steering wheel vibrator 1, which is located close to the outer diameter of the steering wheel.

According to one highly preferred embodiment, the extended vibration body 1 is arranged in or on the ring of the steering wheel. Furthermore, the vibration body 1 and the vibrator 2 are surrounded by a soft and flexible material.

According to a significant embodiment, the vibration body 1 is arranged in a groove or a track, located in the ring of the steering wheel under the external surface cover of the ring . The reference number 451 in Figure 4 denotes a groove in the ring of the steering wheel, 31 denotes a soft spacer material, and 32 a shock-absorbing reinforcement, of a suitable material, for the walls of the groove.

Figure 4, which shows an enlarged cross-section A-A in Figure 3, shows how the vibrator ring 3 is oriented in a track 451, here denoted "groove", in the plastic cover 45 of the ring of the steering wheel, which lies around the complete circumference of the ring of the steering wheel. The location of the vibrator ring 3 in the groove 451 is such that the vibrator ring can vibrate easily, without large counteracting forces from the walls of the groove 451, and such that the vibration is not easily propagated to these walls. It is preferred that the vibrator ring 3 be held in place by means of a soft and flexible spacer material 31 between the vibrator ring 3 and the walls of the groove 451. It is appropriate that the spacer material be plastic. During adaptation during manufac- ture, the vibrator ring 3 and its soft holder 31 can be provided with an outer cover 32 that forms a wall at the site of plastic injection at the steering wheel, such that the outer cover of the steering wheel conceals exactly the vibrator ring 3. That which has been described here is valid to the same extent for the vibrator 2 that is fixed at the vibrator ring 3.

According to one preferred embodiment, more than one vibrator is present, where each one of the vibrators is coupled to its respective vibration body.

It is important in this case that the vibration bodies 11, 12 lie separated from each other and that each one of the vibration bodies is coupled to a vibrator, see Figures 6 and 7.

It is also preferred in this case that the motor vehicle steering wheel be provided with at least two vibrators, one of which is located close to the upper side of the ring of the steering wheel and the second close to the lower side of the steering wheel. These vibrators are designed such that they can operate at different angular frequencies.

Figures 5-7 show a design of a steering wheel vibrator installed in a steering wheel. A steering wheel for a passenger vehicle with three spokes is shown in this case as an example. The metallic supporting structure of the steering wheel has been omitted from Figure 5 for reasons of clarity. This variant shows an example of how a steering wheel can be designed with the aid of the invention to have at the same time haptic alarms with two different frequencies with the least possible interference between the two frequencies.

The reference number 11 in Figures 5-7 denotes a first steering wheel vibrator that operates at a first angular frequency GOi, and the reference number 12 denotes a second steering wheel vibrator, that operates at a second angular frequency ω2.

Figure 5 shows in a view from above a vehicle steering wheel 4 and a steering wheel vibrator 11, shown with dashed lines, that lies inside it. Figure 6 shows a cross-section B-B of the ring 43 of the steering wheel, where it is clear that not only the upper side, but also the lower side of the ring of the steering wheel is provided with a steering wheel vibrator, denoted 12. The metallic supporting structure of the steering wheel is suggested with oblique hatching cross- section in Figures 6 and 7.

The uppermost steering wheel vibrator 11, which operates at the angular frequency coi, lies in a groove at the upper side of the ring 43 of the steering wheel, while the lower steer- ing wheel vibrator 12, which operates at the angular frequency 0)2, is located in a groove at the lower side of the ring 43 of the steering wheel. Both steering wheel vibrators 11 and 12 are at the boundary of the respective side of the outer cover of the ring of the steering wheel, which cover thus absorbs the vibration coi at the upper side and the vibration ω ₂ at the lower side. Both vibrators have free mobil- ity on other sides since they are bounded by a very flexible spacer material 31, such as extra-soft foamed plastic, which reduces the damping of vibration and leads to the variation in amplitude around the vibrator ring being low. The effect is in this way achieved that when the hand pressure against the ring 43 of the steering wheel increases, through a stronger grip from the driver, these forces are absorbed by the ring 43 of the steering wheel, while the vibrator 11, 12 does not exert any other counteracting force that its own forces of deformation. In this way, it is prevented that the vibration be significantly damped when hand pressure increases .

Figure 7 shows a cross-section C-C in Figure 5, with the location of the motor unit of the vibrators 11, 12. The plas- tic external surface cover 45 of the ring of the steering wheel is sufficiently hard and shock-absorbent, such that no reinforcement 32 of the groove 451 is necessary.

According to a second embodiment of the invention illustrated in Figures 8 and 9, the vibrator and the vibration body are located in a cover that can be applied and removed, arranged to lie around the ring of the steering wheel.

The reference number 5 in Figures 8 and 9 denotes two differ- ent covers for a steering wheel. The reference number 51 denotes a protuberance of the cover, and 551 denotes a groove in the cover.

The protuberance 51 contains a compartment for a vibrator 1 and an alarm-raising arrangement, which may be arranged as specified by the Swedish patent SE 539317, containing a de- tection component with a sensor for movement of the steering wheel and units for setting and indication, etc.

Figure 8 shows a cover equipped with a steering wheel vibra- tor 1 according to the invention. A compartment for the alarm-raising arrangement 51 is suggested in the Figure.

The steering wheel vibrator 1 in its design follows the same principles that have been described above for a steering wheel vibrator according to the invention installed in the steering wheel and located in a groove 551 of the cover 5 in such a manner that the cover 5 absorbs forces of pressure from the hands without placing any pressure load onto the vibrator 1 through it being positioned inside a very flexible spacer material 31 in the groove.

The power supply for the alarm-raising arrangement may be from a small battery and/or an electrical conductor with a contact, adapted to the cigarette lighter fitting of the vehicle, not shown in the Figure.

Figure 9 shows a cross-section through D-D of the cover in Figure 7, where the vibrator ring is located at the outer part of the cover and rests against a flexible spacer mate- rial in a groove in the cover, as shown in the Figure.

According to a further design of the invention, one or several steering wheel vibrators are integrated into a cover for a car steering wheel, which is equipped, in addition to this, with an alarm-raising arrangement.

Independently of the designs described above, it is a preferred embodiment that a vibrator and a vibration body are arranged such that the external surface cover of the ring of the steering wheel vibrates with a frequency and an amplitude such that the Pacinian or Meissner corpuscles in the fingers or hands of the driver are activated. In the case in which two vibration bodies each with a vibrator are present, one of the vibration bodies can vibrate with a frequency and an amplitude such that the Pacinian corpuscles are activated, while the second vibration body can vibrate with a frequency and an amplitude such that the Meissner corpuscles are activated .

The present invention solves the problems described in the introduction. The invention concerns an arrangement that can be designed to give an even, desired frequency and amplitude of vibration and an even distribution of the vibration around the ring of the steering wheel. The arrangement can be generally used for vehicle steering wheels without extra fitting. By using two steering wheel vibrators separated from each other in the steering wheel, the invention makes possible at the same time the presence of two different frequencies around the ring of the steering wheel, as is suggested in WO 2007/136 338 Al, and without any noticeable interference arising between these two vibrations.

Through the arrangement containing a vibrator body that has considerably less mass than the metal structure of the steering wheel, considerably less electromotor energy will need to be supplied, while at the same time a haptic alarm obtains a higher quality through its even distribution and the distinctive character of its frequency.

It is obvious that one skilled in the art can develop alter- native locations of the vibrator and other embodiments of the invention, and that such a person can modify the arrangements described and achieve the desired functionality, without deviating from the innovative concept of the present invention .

The present invention, therefore, is not to be considered to be limited to the embodiments specified above, since it can be varied within the scope specified by the attached patent claims .