BACKGROUND OF THE INVENTION

The invention relates to improvements for a bicycle provided with a side wheel on each side.

While operational, the side wheels in general are positioned fixedly or semi-fixed ly to keep the bicycle upright relative to the road surface under various circumstances.

Such known bicycles with side wheels that are known per se, are characterized by a number of drawbacks.

In case of the known bicycle with two side wheels, the bicycle will in general always be kept upright relative to the road surface. This is rather unpleasant for the rider when riding over road surfaces that are at a lateral slant, and riding through bends. On surfaces that are at a slant, the cyclist would like to sit straight up, in the same way as would be the case with a regular bicycle without side wheels, and when riding through bends the cyclist would like to be oriented in accordance with the slanted position in the bend.

Attention should furthermore be paid to the fact that two side wheels together with the load bearing wheel of the bicycle are three wheels placed adjacent to each in transverse direction that have to support on the road surface simultaneously, whereas the differences in height of the road surface may show large differences at those three locations and also constantly change. The motion of the side wheels may greatly affect the bicycle's behaviour and the cyclist's comfort, particularly when taking bends in the road and riding over road surfaces that are at a lateral slant.

A drawback of fixed side wheels arises when the base at the location of the driving rear wheel has a pot-hole. In that case, when the side wheels have been rigidly arranged, traction will be lost as the rear wheel no longer contacts the ground and starts slipping. To make up for this shortcoming it was devised that instead of the fixedly positioned side wheels contacting the road surface in the vertical position of the bicycle, a clearance of approximately one or two centimetres would be used. This clearance with respect to the road surface, however, means that the bicycle moves to and fro sideways over a small distance, which results in an uneasy sensation and is unpleasant for the rider.

SUMMARY OF THE INVENTION

To improve on this, as regards at least one aspect, the invention provides a bicycle as described in the description and/or described in the attached claims, the contents of which should be considered inserted here.

The invention relates to side wheels that can selectively be, individually urged downwards relative to the frame of the bicycle, to as it were push off from the road surface on that side. Said downward motion is realised by a servomechanism having an individual drive for each side wheel, in combination with a balance sensor and with the individual drive of each of the side wheels for urging the sidewheel downwards. In that way, too large a tilt to the right-hand side can be corrected by pushing off the right-hand side wheel to cause a tilting motion to the left and too large a tilt to the left-hand side can be corrected by pushing off the left-hand side wheel to cause a tilting motion to the right.

In one embodiment of the invention the motions, in particular the downward motions, of the side wheels or auxiliary wheels are controlled electrically, hydraulically, pneumatically or mechanically in such a way as to correct a deviation from the wanted (soil) position of balance H of the bicycle, which position of balance is at least substantially parallel to the resulting direction of gravity and the centrifugal force exerted on the bicycle and the cyclist. For that purpose, the angle of tilt (deviation) a from said wanted position of balance H relative to the position E (ist) actually taken up (considered in a vertical plane perpendicular to the longitudinal axis of the frame of the bicycle) is sensed by a sensor and passed on to the servomechanism which moves the side wheels or auxiliary wheels such that said angle of tilt a is neutralized.

in one embodiment of the bicycle according to the invention, the side wheel in question in dependency on the sign of the sensed angle of tilt a is forcedly moved in downward direction. In one embodiment said motion depends on the magnitude of the angle of tilt a. In order to describe said motions the following definitions and names are important. First of all, there is a left-hand side and a right-hand side of the bicycle and there is a left-hand side wheel and a right-hand side wheel. As regards the position E that is taken up, there is a left-hand tilt and a right-hand tilt having a left- hand angle of tilt al_ and a right-hand angle of tilt aR, wherein the angle a indicates the angular deviation of the position E that has been taken up and with respect to the wanted position of balance H.

According to one aspect, the invention provides a bicycle comprising a bicycle frame having two aligned wheels and two side wheels on either side of the bicycle frame, comprising a servomechanism comprising an individual drive for each of both side wheels, for urging the selected side wheel in question downwards in order to push the bicycle off from the road surface on that side, thus bringing the bicycle from an actual position E deviating from a wanted position of balance H, into the wanted position of balance H, and a sensor for sensing a right-hand or left-hand angle of tilt aR or aL of the frame relative to the wanted position of balance H and on the basis thereof sending a signal to the servomechanism, wherein the servomechanism has been configured for controlling the drive of the selected side wheel in question for urging the side wheel in question downwards in response to the signal sent by the sensor.

As regards the angle of tilt a, in one embodiment, there are two values to the right and to the left that are relevant in terms of the downward motions of the side wheels. The angles in question are indicated in increasing values to the right by a1 R and cs2R and to the left by crt L and a2L.

In one embodiment, the servomechanism can be configured such that in case of angles of tilt to the right and left from zero up to a first threshold value a1 R and a1 L, no more downward forces are exerted on the side wheels by the servomechanism. The sensor will in that case give no signal to do so. For these angles of tilt the drives of both side wheels can be configured such that the force counteracting an upward motion of a side wheel is smaller than approximately half the force exerted by the weight of the bicycle including the rider on the load bearing wheel of the bicycle situated between the side wheels. When riding the rear wheel through a pot-hole, wherein the road surface at the location of the path for the side wheels is situated at a higher level, each side wheel is able to move upwards so that the rear wheel remains in contact with the road surface.

As regards all angle of tilt values exceeding the first threshold value a1R to the right and a1L to the left, the servomechanism has been configured for urging the right-hand or left-hand side wheel downwards. The speed with which the side wheel is moved downwards may depend on the numerical value of the angle of tilt. The speed may for instance be proportional to the absolute value of the angle of tilt, but another control strategy is also possible as is the possibility to have a single or for instance only two, multi-stage, speeds suffice. For instance, the servomechanism may have been configured such that in a range of the sensed angle of tilt to the right exceeding a second larger threshold value a2R, the right-hand side wheel is extended at a higher speed than in the range of a1R up to a2R, as well as that in a range of the sensed angle of tilt to the left exceeding a2L the left-hand side wheel is extended at a higher speed than in the range of a1 L up to a2L.

As regards the angle of tilt values exceeding the first threshold value a1 R to the right and exceeding a1 L to the left, it has also been provided in one embodiment that the side wheel positioned on the other side, in this case meaning the right-hand side wheel and the left-hand side wheel, respectively, can be moved upwards while overcoming a counterforce developed by the drive active on that side which at the most is 50 percent of the force exerted on the adjacent load bearing wheel of the bicycle by the weight of the bicycle and the rider. Said counterforce may depend on the absolute value of the angle of tilt and in general it will become smaller as the angle of tilt becomes larger, but another control strategy is also possible here.

As regards all angle of tilt values it is preferably so that the side wheels can freely move downwards down to the road surface or down to an end stop. For that purpose, a freewheel mechanism may have been included between the drive and the side wheel in question.

The side wheel drives included in the servomechanism may have been configured mechanically, pneumatically, hydraulically and/or electrically.

In one embodiment, the two auxiliary wheels or side wheels of the bicycle, defining the situation of balance of the bicycle, have each been attached to a rod, a so-called wheel carrier, which can be moved up and down by a servomechanism in or over a guide or holder for it. These wheel carriers and wheel carrier holders, may for instance be two tubes that fit into each other and wherein the wheel carrier holder has been attached to the bicycle frame on each side of the bicycle. The displacement of the wheel carrier may be linear. The displacement can be substantially vertical, preferably at least almost vertical. In sideward direction, the occupation of space can then remain within limits. The wheel carrier holders may for instance be situated between the rear axis and the pedal axis spaced apart from the rear axis to approximately half a radius of the rear wheel.

The motion of the side wheels can then be obtained by an individual drive of each wheel carrier via for instance a driving electromotor or for instance a hydraulic drive, wherein each time the wheel carrier that effects the wanted position of balance of the bicycle frame by the downward motion of the side wheel in question, is moved.

In an advantageous elaboration of the invention, the entire servomechanism with all accessories, including side wheels, can be added as a kit to practically all regular bicycles, in particular also electrically driven bicycles. The embodiment as a kit is advantageous in terms of costs of the complete bicycle as in that way use can be made of the expected low price of the current bicycle and the, for the user perhaps, prospective electric bicycle. In addition, one embodiment according to the invention also has the property that, if required, the bicycle can be made narrower so that it can be parked in a regular bicycle parking facility.

For that purpose the attachment of the wheel carrier to the bicycle frame is such, that the upper side of each wheel carrier holder has been attached via one or two almost horizontal connections to one or two almost horizontal tips of the seat stay and/or the saddle tube, wherein the lower portion of each of the wheel carrier holders has been attached via one or two almost horizontal connections to one or two almost horizontal tips of the chain stay and/or the lower portion of the seat stay and wherein for absorbing vertical forces a vertical shore rod is present running from the chain stay to the upper portion of the wheel carrier holder or from the lower portion of the wheel carrier holder to the upper portion of the seat stay or the saddle tube. In this construction according to the invention, a strong and suitable attachment is available for nearly all types of bicycles.

The sensor may have been configured in various ways. The sensor may be an existing inclinometer, when able to indicate the angle of tilt a. In an exemplary embodiment the sensor comprises a freely rotating coding shaft to which is attached a pendulum including weight, subjected to the above-mentioned resulting force and which in transverse direction indicates the number of degrees of arc deviation of the bicycie frame relative to the direction of the above-mentioned resulting force and which cooperates with the servomechanism which in dependency on the deviation moves the side wheel in question downwards such that the deviation that had occurred is decreased.

In one embodiment the sensor comprises a coding shaft with a pendulum including weight that rotates freely about a point of the bicycle frame and moves in a vertical plane or a plane that is at a small angle to the vertical, transverse to the bicycle frame, and which in case of an increasing angular deviation of the frame to the direction of the resulting force near the free outer end successively switches on a few contacts, such as micro switches, that for instance allow a servomotor to run slowly at first and then faster, as a result of which the side wheel in question moves downwards and thus the angle of tilt is decreased.

In a compact, more electronic embodiment, use is made of so- called "sensor boards". These special circuit boards have been provided with various micro sensors and digital electronics, and convert various motions of the board into output signals that can be programmed and used for operating the various actors such as among others the servomotors.

A bicycle is balanced when the acceleration vector constituted by the resultant of the gravitational acceleration and the optional centripetal acceleration resulting from an optional bend, is parallel to the height axis of the bicycle. When the bicycle is not balanced, there is question of a sideward component of said vector.

Assume that in the initial situation the bicycle rides straight up and straight ahead. Using the handlebars a bend is started. The bicycle is still upright, so that the resultant of gravity + centrifugal force is not in the plane of the height axis of the bicycle. In other words, the actual position E deviates from the wanted position of balance H. Said deviation is measured by an acceleration sensor on the sensor board. If the sideward acceleration at the level of the sensor exceeds a threshold value, a side wheel is urged downward by activation of the servomotor in question. In that way, the bicycle is tilted into a position in which the said resultant is in the plane of the height axis.

Said tilting motion causes an acceleration on the sensor (unit) or sensor board, which is (also) measured. The acceleration sensor then measures an increased acceleration instead of a decreasing acceleration, so that the correcting tilting motion is going too far. In order to prevent this, a correction is applied using a gyroscope provided on the sensor board. In that way, the angular speed of the tilting motion about the longitudinal axis of the bicycle is measured, which is subsequently differentiated in time into the angular acceleration. Said value is used to correct the value measured by the acceleration sensor. The angular acceleration is then multiplied by a correction factor. The magnitude of said correction factor is determined in dependency on the height of the acceleration sensor relative to the road surface, and the sign depends on the orientation direction of the gyroscope. Due to this correction, the resultant of the gravitational acceleration and the centripetal acceleration can be determined sufficiently accurate for realising a proper operation of the control system.

In other deviations from the position of balance, such as riding on a road surface of which the transverse slope changes (for instance from horizontal to a slope to the right) a corresponding control system with correction can be applied.

In the bicycle according to the invention, the four wheels of the bicycle, that means both main wheels and both side wheels, are able to remain in contact with the road surface in case of changing base profiles, such as a road surface having a transverse slope, a pot-hole, a speed bump.

The aspects and measures described in this description and the claims of the application and/or shown in the drawings of this application may where possible also be used individually. Said individual aspects may be the subject of divisional patent applications relating thereto. This particularly applies to the measures and aspects that are described per se in the sub claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in which:

Figure 1 shows a schematic representation of the wheel carrier guide for a bicycle having two side wheels or auxiliary wheels, wherein the wheel carrier can be moved vertically by an electromotor;

Figure 2 shows the attachment of the wheel carriers in question to the bicycle in side view;

Figures 3 and 4 like figure 2 but in a rear view and top view;

Figure 5 shows a detail of an example of a servomotor drive of the wheel carrier of figure 1 , in side view; Figure 6 like figure 5 but in a top view;

Figure 7A and 7B show an example of a sensor for the servomechanism according to the invention, in top view and side view;

Figures 8A and 8B show circuit diagrams for the electric components for a servo system according to the invention, for a highly simple and cost-effective embodiment of the servo system;

Figures 8C-E show circuit diagrams for an embodiment having a more gradual change of the forces that occur; and

Figures 9A-G show a few schematic positions in the use of a bicycle according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In figures 1-4 each wheel carrier holder or wheel carrier guide 1 is a square tube, in which the wheel carrier 2, also a square tube, is able to move linearly and vertically. Each wheel carrier holder 1 (the one on the left- hand side as well as the one on the right-hand side of the frame) has been provided with a motor bracket 3 to which the servomotor 4 has been attached. The servomotor 4 rotates a drum 5 able to pull in a pulling cable 6 which runs upwards, as a result of which the wheel carrier 2 including the side wheel 7 attached thereto, is urged downwards.

At the location of 6a the pulling cable 6 has been attached to the upper side of the wheel carrier and then runs to the guide wheel 8 and subsequently runs to the drum 5. After a few windings around the drum 5 the pulling cable 6 runs to the guide wheel 8 again and subsequently to the bottom side of the wheel carrier 2. A tension spring 9 ensures that the cord is tensioned at all times.

When the polarity of the motor has been changed, the wheel carrier 2 can be moved upwards again with little effort. Such moving upwards can also occur when the road surface presses against the bottom side of the side wheel. The mechanism in question of figure 1 is therefore able to bring the wheel carrier down via the servomotor with a large transmission ratio and therefore with a large force and in case of the voltage that has changed polarity, the wheel carrier can be returned with little effort when this is required to place the bicycle in the wanted position of balance H.

A stop 38 has been arranged for limiting the outgoing displacement of the wheel carrier 2. By way of example the wheel carrier 2 can be made of a tube having a cross-section of 20x20x1.5 mm, the wheel carrier holder 1 of a tube having a cross-section of 30x25x1.5 mm. The dimensions of hi , h2, h3, h4, h5 and h6 may for instance be 135 mm, 150 mm, 435 mm, 130 mm, 420 mm and 700 mm or 28 inch, respectively.

In figure 1 two threaded weld studs 10 and 11 can be seen with which the wheel carrier holder 1 has been attached to the bicycle frame (in a slightly rotatable manner). Figure 1 also indicates how the side wheel has been attached to the right of the vertical wheel carrier 2 via a short connection 12. This intervention has made the side wheel slightly self-steering. The rather slight rotary motion required, can easily be realized and set via the weld stud attachments 10, 11 and/or via the clearance of the two square tubes.

In three views, figures 2, 3 and 4 show how the side wheels have been attached to the bicycle frame via both above-mentioned weld studs 10 and 11.

The upper sides of the wheel carrier holders or wheel carrier guides have been attached to an almost horizontal plate 12a via said weld stud 10 and an angled piece. Said plate 12 has been attached to a connection plate 13 by two attachments, which connection plate provides connection to the upper side of the seat stays 14. In that way, the upper sides of the wheel guides have been firmly attached in horizontal direction to the bicycle frame.

The lower sides of the wheel carrier holders or wheel carrier guides have each been attached via a rigid almost horizontal L-shaped lying metal strip 15 (comprising two legs 15a, 15b) having two attachment tips 16. In that way, the lower sides of the wheel carrier holders or wheel carrier guides have been firmly attached in horizontal direction to the bicycle frame (when tightening the bolts on the weld studs 10, 11). It is noted that the sidewardiy extending leg 15a of the connection 15 can also be parted, having two parts that can be set in a position with respect to each other, for instance by sliding and then securing in the wanted position, wherein by choosing the length of the sidewardiy projecting leg 15a the track width of the side wheels can be adjusted. The wheel carrier holder in question can then be rotated about the point of rotation of weld stud 10 after slightly loosening the bolt at that location.

Subsequently the upper sides of the wheel guides have also been attached to a tip of the chain stay 17 (figure 2-4) via weld stud 10 and a metal strip 18. In this case, it regards a lightweight and thin metal strip as it is particularly loaded in longitudinal direction in case of vertical forces that are exerted upwards on the wheel guide, in order to prevent that the strip is stretched and takes up the middle portion of the space between the wheel carrier holder and the seat stay, the strip has also been connected to the middle section of the seat stay via the clamp 20 (figures 3 and 4).

For compact parking of the bicycle in a shed, the connection to weld stud 11 can easily be detached or the two parts of the leg 15a can be detached from each other and subsequently, after slightly loosening the bolt on weld stud 10, the wheel carrier holder can be rotated sidewards and upwards over approximately 180 degrees about weld stud 10. The widest width of the bicycle is then defined by the handlebars.

Figures 5 and 6 show details of a motor drive of the wheel carriers. The bracket 3 can be seen that has been welded to the wheel carrier holder 1 and serving as housing for the motor drive with servomotor 26. The part 27 of the servomotor 26 is a reducer for the very large transmission ratio of approximately 1 :500 required for providing the transmission forces. The servomotor 26 has been attached to the bracket by the screws 34, via the rectangular attachment plate 32. The pulling cable 6 has been attached to the drum 5 via the metal part 37. The drum 5 has been bearing mounted to a pin 28 welded to the bracket 3. The interior part 33, 30 of the drum 5 is driven via the reducer with large transmission ratio. Via a freewheel coupling 35 this interior part 30 transmits the driving force of the servomotor 26, 27 in urging direction (anticlockwise in the drawing figure 5}, to the drum 5, for urging down the wheel carriers, whereas a motion of the drum 5 in the same direction (of extension) caused, however, by the spontaneous downward movement of the wheel carrier 2, is not transmitted to the motor shaft by the drum 5. This means that when the servomotor is standing still or rotates in the opposite, non-urging direction, the drum 5 is able to rotate onwards in the direction of extension wherein the wheel carrier by its own weight and/or a spring that is not shown moves further down to the road surface or the end stop (such as position 38, figure 1).

In the simple embodiment of the invention as described here, for the required freewheel coupling and the drum, use is made of the known freewheel coupling generally used for the freerun of the acceleration gears of a regular bicycle. Instead of a pulling cable another suitable supple, elongated pulling element can be used, such as a chain engaging onto the drum.

The said very large transmission ratio makes it difficult to rotate the motor via the driven shaft of the transmission reduction, meaning that a motion of the wheel carrier in the upward, non-urging direction which opposes the urging direction, requires a very iarge driving force, also when the motor is entirely non-actuated. In order to ensure that the wheel carrier 2 is still able to move upwards using a force that is not too large, the polarity of the motor should first be changed electrically to a low voltage. Said low negative voltage that has changed polarity is too low to allow the motor to rotate in the non- urging direction, but indeed suffices to effect that the motor in case of an additional external force of the wheel carrier starts moving in the non-urging direction, wherein the friction of the motor and also the friction of the driven mechanical reduction are only just overcome, as a result of which the motor can be moved upwards using relatively low external force. The required magnitude of said external force is indicated further in the following.

It is noted that if the resistance the motor generates when rotating in the non-urging direction would be too low or unreliable, an additional torsion friction could be required that may for instance be electrically switched on.

In figures 7A and 7B an example of the balance sensor 39 is shown. It has been attached to the (in this case inclined) saddle tube 36 of the bicycle (see figure 2). The sensor 39 comprises a box 43 including lid 44, which box has been attached by means of bolts 45, which box contains a weight 40 attached at the lower end of a flat rod 46 that has been suspended from a fixed point 42 of the box so as to rotate. The weight 40 is able to oscillate in transverse direction of the bicycle, transverse to the plane of symmetry of the bicycle, more or less like a pendulum and under the influence of a motion damping that is not shown but known per se, depending on the vertical position of balance of the frame of the bicycle. In a purely vertical position of the bicycle the weight hangs straight down as shown. On either side of the flat rod 46 bendable strips 48 have been attached by means of rigid strips 47. Rigid U-shaped lips 49 have further been attached to the flat rod 46 on either side thereof, offset in a direction parallel to the axis of rotation of the flat rod 46. The range of the strips 48 therefore is adjacent to the range of the lips 49. Micro switches MSL and MSR have been arranged in the box 43, within the path of the strips 48. Micro switches MSLR have been arranged in the box 43, within the range of the lips 49.

In case of an angle of tilt a1 R and a1 L abutment of the strip 48 in question switches on the micro switch MSR or MSL In order to achieve that in case of a slight angle of tilt a1R or a1L the weight still has sufficient force indeed to activate the micro switch, a relatively Iarge weight of for instance 0.5 to 1 kilogramme is required. Considering the advantage of a direct actuation of the micro switches, in the embodiment of the invention as described here, the battery of the servo system that is needed anyway can be used as weight. For that purpose, the battery may be attached to the metal part 40.

In case of a further increasing tilt to the left or right, the flexibility of the strips 48 allows a further relative rotation of the flat rod 46, and when achieving the angles of tilt ct2R or a2L, the lip 49 in question is also able to switch on the micro switch MSLR in question. Said micro switches have been circuited parallel and are each individually able to actuate relay LR yet to be discussed on the basis of figures 8C-E.

Reference is now made to figures 8A and 8B. Depending on the angle of tilt the above-mentioned weight will activate micro switch MSL or MST by pressing in, as a result of which the relay LL or the relay RR are actuated. In case of an angle of tilt a that is smaller than a1 L and also smaller than a1 R, the two non-actuated relays LL and RR connect the servomotors smR and smL with the low voltage that has changed polarity, realized in figure 8A by a series resistor W reducing the voltage at the location of the servomotor from approximately 12 Volt to approximately 1 Volt. Said low voltage that has changed polarity will have both motors start to run in reverse direction, however, the voltage is so low that it fails to do so. Not until an upwardly oriented pressure arises on one of the wheel carriers, will the wheel carrier start moving and will the servomotor in question start rotating in the non-urging direction.

When the right-hand angle of tilt exceeds the value a1R, MSR will actuate the relay RR, see figure 8B. As a result, two actions take place. Firstly, the upward motion by the left-hand servomotor smL now takes place of its own accord, as in that case the series resistor does not operate two servomotors but only one and as a result the remaining servomotor smL will be under a voltage that is approximately twice as high. Secondly, the servomotor smR is switched to the battery voltage driving the motor in the direction wherein the right-hand wheel carrier is urged downwards and the bicycle starts straightening up. As soon as the angle of tilt a has been reduced to the value below a1 R, the micro switch MSR switches off the relay RR as a result of which the motor smR changes polarity again to the extremely low voltage that has changed polarity (condition of figure 8A) and the motor stops again in the condition of changed polarity wherein the right- hand side wheel will only be moved by an external upward force. By selecting the resistance value in question of the series resistor W, said force is such that the force counteracting the externa! force is smaller than 50 percent of the weight of the bicycle and rider on the adjacent drive wheel of the bicycle.

Figures 8C-E show a more elaborate circuit (which just like the circuit of figures 8A.B can be accommodated in the sensor housing), wherein both the voltages that have changed polarity as well as the immediately driving voltages run in two and three stages. Figure 8C shows the initial situation, with angles of tilt smaller than a1R and a1 L. If the angle of tilt exceeds a1R, the micro switch MSR will be operated again and thus the relay RR will be actuated. See the situation in figure 8D. Now the voltage V3 is the voltage urging the right-hand side wheel downwards. Said voltage comes from an amplifier PWM2 and is smaller than the battery voltage of 12 Volt. However, if the angle of tilt becomes larger than a2R, at some point in time the relay LR will be actuated via the micro switch MSLR in question (figure 7B), as a result of which the said voltage is changed to the full battery voltage of 12 Volt, see the situation in figure 8E, and the maximum speed of the wheel carrier in question.

In figures 8C-E the low voltage that has changed polarity also runs via a multi-stage system. For the voltage that has changed polarity three voltages are available here, V1 , V2 and the battery voltage of 12 Volt. The lowest voltage V1 is transmitted from relay LL or RR to the servomotor in question via a third change-over-contact (here depicted schematically separately, for the sake of clarity as LL+ and RR+). As soon as one of the relays LL or RR, in this example RR, is actuated said change-over-contact will replace the voltage V1 by the higher voltage V2. When subsequently relay LR is actuated, via a third change-over-contact (here depicted schematically individually, for the sake of clarity, as LR+) of relay LR the voltage V2 will be replaced by the full battery voltage of 12 Volt, see figure 8E. To all of these cases applies that the higher the voltage that has changed polarity is, the easier it will be to move the side wheel in question upwards, meaning the side wheel (in this example the left-hand side wheel) that is on the opposite side of the side wheel that is being extended.

When a bicycle including rider thus rides straight ahead over a horizontal road surface, the pendulum will hang vertically. When subsequently the road surface starts to slope (figure 9A) and the left-hand side of the road rises, the bicycle will start to lean over to the right and the box 43 will also become inclined as a result of which the micro switch MSR and subsequently the relay RR are actuated and the right-hand servomotor smR starts urging the right-hand side wheel downwards. As a result, the right-hand side of the bicycle will be urged upwards and the bicycle will straighten up (figure 9B) until the angle of tilt to the right becomes smaller than a1 R. At that moment, the right-hand relay RR switches back again and the equilibrium has been restored to a sufficient extent.

The previous circuit is simple and cost-effective. Sophisticated versions are possible here, wherein for instance the speed curve of the servomotor runs in several stages or linearly. The servo motion for bringing the side wheel down can also be combined with a simultaneous upward servo motion for the other side wheel.

It is also of importance to make use of circuits that realize electro-dynamic deceleration especially in for instance decelerating the servos in their return motion to the centre of the suspension. It regards known circuits that can be used here, for instance by short-circuiting the servomotor.

It is noted that in figures 8A-E the diode B is present to effect that the counter-EMK when pushing the wheel carrier upwards will not be active in a decelerating manner and that the diode A is present to effect that the wheel carrier urged downwards by the servomotor will decelerate very quickly as soon as the voltage to the servomotor is switched off.

When the bicycle and its rider rides through a right-hand bend (figures 9C-E) the weight will swing to the left-hand side of the sensor due to the centrifugal force and the left-hand servomotor is activated, after which the left-hand side wheel is urged downwards and the bicycle starts to lean over to the right until the angle of tilt a has achieved a value that corresponds so closely to the value of the resultant of the prevailing gravity and the centrifugal force that the angle of tilt becomes smaller than a1 R and the motor in the condition of changed polarity has come to a standstill again. The right-hand side wheel is allowed to move freely upwards.

When the bicycle and its rider ride on a concave road (figure 9F) the side wheels will be subjected to an upward force from the road surface. As a result, there is a risk that the driving wheel of the bicycle loses contact with the ground, however, this risk is avoided because at an upward force exceeding 50 percent of the weight of the bicycle on the driving wheel in question the side wheels will move upwards and the driving wheel thus remains in contact with the road surface throughout.

When the bicycle rides on a convex road (figure 9G) the side wheels will not be released from the road surface as the free run present in the drives makes it possible that the wheel carriers due to their own weight and/or the pressure of an arranged spring for instance, will be able to sink downwards down to the road surface. The bicycle will therefore remain standing with both side wheels on the road surface. This will give the rider a sense of security and the corrections described above will remain in force throughout. When the freerun would be replaced by a fixed drum, the bicycle leaning over would also cause the side wheels to end up on the road surface but this would then happen much later and as a result of the correcting actions of the servo system.

A point of attention for the control systems described here is the behaviour of the servomotors in bends. In a commencing bend to the right the handlebars will first move to the right. This means that the bicycle will immediately tilt to the left. Subsequently the bicycle will start describing a bend to the right and a centrifugal force to the left will also arise in the process. Via the servo system and the left-hand servomotor in question, these motions to the left activate a controlling tilting motion to the right, which motion should end in an inclined position of balance to the right of the bicycle that is parallel to the resultant of gravity and the centrifugal force prevailing in the bend. The initially powerful starting motion to the left should therefore result in an inclined position to the right within a very short time. This requires a large capacity and a very quick response by the servomotor and to prevent this, in one embodiment of a control system according to the invention, a type of differentiating action working ahead can be provided, which at an early stage effects a powerful tilting motion to the right generated by the servomotor.

The centrifugal force is inversely proportional to the bend radius or proportional to 1/R in which R is the bend radius and proportional to the quadrate of the bicycle speed V, or the centrifugal force is proportional to WR. The bend radius 1/R is proportional to the steering angle. Using known means, both the steering angle and the bicycle speed can be converted into a signal proportional to the centrifugal force or the first derivative of said force. For realising an early tilting motion to the right by the servomotors when starting a bend, the steering tube has been provided with a speed dampening whereas the connection between the steering tube and the handlebars has been made elastic with a centre position or zero position. The effect thereof is that a steering angle caused by the cyclist via a steering motion will not immediately be transmitted to the steering tube and the front wheel but indeed immediately to the servomechanism. The steering tube and the centrifugal force follow later. This means that the servomotor in question already works at a slight centrifugal force and therefore requires less power. In case of a control system having one or two coding shafts (see below) this signal may for instance cause a horizontal motion of the pendulum to the left or right by activation of an electromagnet. Alternatively, this signal may be able to directly actuate the relay RR or LL. In case of a digital control system with sensor boards, such as for instance discussed above, this signal has to be used as input for taking the left-hand or right-hand servomotor to a proportional speed.

For a simplified embodiment, the speed dampening on the steering tube will suffice and an elastic connection between the handlebars and the steering tube with a closing contact for a particular bicycle speed, deduced from for instance a hub dynamo or bicycle computer, with in series therewith a n.o.-contact or double n.o.-contact closing at a particular steering angle of the steering tube to the left or right.

The object of these facilities is to effect that the thus initiated, forced tilt to for instance the right in the bend runs ahead or simultaneous to the increase of the counteracting centrifugal force as much as possible, because in that case the servomotor needs to do very little.

The servo systems or servomechanisms described above are systems wherein the wheel carrier is directly moved mechanically by an electromotor. However, it is also possible in the servomechanism to have the vertical motions of the wheel carriers operated by a hydraulic cylinder, in this case the servomotor, such as pump, will permanently pressurize a hydraulic medium. From said permanent pressure reservoir the wheel carrier in question can be moved downwards via an individual hydraulic cylinder wherein the speed of movement is controlled by an electrically operable control valve. When the control valve connects the supply to the cylinder to a reservoir of low pressure, the wheel carrier can subsequently be moved upwards again. It is also possible to connect the servomotor to a hydraulic pump and in that way supply the pressure agent to the cylinder, wherein the speed of movement is defined by the speed of the servomotor. Each wheel carrier requires a servomotor and a servo valve or a sensor-operated switch valve is required connecting the correct wheel carrier to one driven (servo) pump. In that way, the two wheel carriers can be operated in the same way as explained for the case with the direct (drum-snare) drive by the electric servomotors. In order to move the side wheels upwards with a required resistance, a throttle valve is required which may or may not be adjustable and that can be switched on for passing the fluid back to the low-pressure reservoir and with a non-return valve as bypass over the throttle valve wherein the non-return valve has the same function as the discussed freewheel coupling in the electric servomotors.

However, a drawback of the hydraulic embodiment may be the higher costs of the hydraulic components.

An inclinometer may optionally be used as a sensor, when made suitable for controlling the servomotors in the bicycle according to the invention.

In one embodiment, a possible imbalance in the control system is effectively counteracted. Such an imbalance may easily arise in a control system including a coding shaft having weight (such as in the embodiment of figures 7A,7B). The imbalance arises especially when the servomotor returns the bicycle (after a tilt correction) to the position of balance. Such a motion to for instance the right, strongly decelerates the bicycle when approaching the position of balance in order to stop in time in the position of balance. In said (return) motion the (undecelerated) weight (at the pendulum) may however tip to the right and activate relay MSR after which the right-hand servomotor starts and throws the bicycle back to the left and thus causes the imbalance. Such an imbalance can be counteracted by arranging a heavier dampening but this may slow down the system too much.

According to a further development of the invention use can be made of an embodiment having two identical coding shafts, both including a pendulum, which have been suspended in the sensor housing next to each other at a horizontal intermediate distance. The left-hand shaft operates the switch MSL to the left and to the right encounters a middle stop arranged in the middle of the sensor housing between both shafts. To the left, the right- hand shaft also encounters a middle stop and operates the switch MSR to the right.

When running against the middle stop, the left-hand shaft including pendulum will operate a micro switch MSXL which, when operating, keeps the relay RR in the non-actuated position, whereas when the pendulum runs against the middle stop the right-hand shaft operates a micro switch MSRX, which during said operation keeps the relay LL in the non-actuated position.

The operation of this control system is such that in the return motion, wherein the bicycle returns from a left-hand tilt to the right to the position of balance, the left-hand shaft including the pendulum encounters the middle stop and as a result keeps the relay RR in the non-actuated position, whereas in case of tipping to the right the right-hand shaft including pendulum is unable to actuate the relay RR. In other words; neither shaft is capable of starting the right-hand servomotor and thus the risk of the onset of an imbalance is prevented. In a returning motion to the left the same happens to the relay LL.

It is noted that the switches MSRX and MSLX switch only very shortly at a rather large operation force arising when the shaft including pendulum in question encounters a strongly decelerated part of the bicycle. Said tilts to be corrected such as in case of a sloping road surface or a bend have no effect on the switching position.

A bicycle equipped according to the invention has a number of advantages.

Firstly, according to the invention, due to moving the side wheels or auxiliary wheels, said loss of comfort is largely or entirely compensated for and the cyclist experiences the original feeling again that is associated with a regular bicycle without auxiliary wheels and without having to exert him/herself to keep the bicycle in the position of balance.

Secondly, the motion of the side wheels according to the invention also influences the mechanical load the side wheels have to deal with during operation and namely in particular when taking bends and riding or standing still on a sloping base. When riding on a sloping base the load will be as small as possible if the frame of the bicycle is kept in a vertical position of balance as much as possible by the side wheels. When taking bends said load is as small as possible if the frame of the bicycle can be kept parallel to the direction of the resultant of the vertical gravity and the horizontal centrifugal force exerted on the bicycle in the bends. When the (inclined) resultant is as parallel to the inclined position of the frame of the bicycle as possible, the mechanical load on the auxiliary wheels will be minimal. A low load of the auxiliary wheels does not only mean a lower rolling resistance of the auxiliary wheels, it also makes a lightweight and cost-effective structure possible and also means that the overall required width of the side wheels can be as small as possible.

Thirdly, the motion of the auxiliary wheels according to the invention is also of importance to overcome the aforementioned fundamental drawback that always occurs for the rider of bicycle with permanent auxiliary wheels when riding over a pot-hole.

Fourthly, the intended vertical motion of the side wheels is also of importance in the sense that the generally required learning curve when switching to a bicycle with auxiliary wheels, no longer applies in case of a bicycle according to the invention, as the incorrigible tilt, in accordance with the previous, no longer occurs.

In a bicycle according to the invention the side wheel is urged downwards on the side to which the frame of the bicycle leans over further than the wanted position of balance (H) in order to realize a returning tilting motion. The other side wheel can be passive, and by following the road surface when tilting back move upwards relative to the rear wheel. Said motion may optionally be imposed by means of the servomotor for that side, but this is not required.

The above description is included to illustrate the operation of preferred embodiments of the invention and not to limit the scope of the invention. Starting from the above explanation many variations that fall within the spirit and scope of the present invention will be evident to an expert.