Tilting Vehicle Australia wishes to disclose inventions that relate to tilting vehicles.
Date of invention  February 2003.  Inventor  Phillip James.

Date of invention February 23,  2008   Inventors:  Bokhorst, Davenport, James.

Invention  [3]  " BRAKE COUNTERSTEER"
Date of Invention 2007. Inventors  : Bokhorst,James
The inventions to be disclosed are disclosed on this page.     Please scroll down to view all items.

Reduced to practise 2007[ James] . Inventors : Bokhorst, James .Disclosed to public here on 19th of  October
                                              "BRAKE COUNTERSTEER."

                                         BACKGROUND OF THE INVENTION.
This invention applies to wheeled vehicles that tilt into corners .
                                               Prior Art Observations.
* Countersteer is a tilt  force  method for tilting vehicles.
* Manual countersteer is seen in a single track vehicle [STV] where the rider must first manually countersteer  the
steerable wheel to create a tilt force prior to modulating the front wheel position to create the rider's desired
steered path. Countersteer tilt control relies on traction between the front tyre and the road. Manual Countersteer
is also seen in multiwheel tilting vehicles.[ eg. Piaggio MP3]
* The control element is generally a handlebar .

* Automatic countersteer methods may be employed to automatically countersteer the front wheel/s of  multi track
tilting vehicles [MTV] and these systems are known in the prior art. These automatic systems remove any
ambiguity of  driver input onto the control element and result in a fundamentally safer relationship between the
driver and the vehicle. The control becomes  a simple steer style input.
*  The control element is preferably a steering wheel [ eg. Brinks Dynamics  CARVER ]

* Simple steer control input is of course seen in a common motorcar. However, a motorcar is disadvantaged
because its  tilt position is fixed arbitrarily normal to the road surface or in fact tilted the wrong way in a corner .
Simple steer can be  combined with automatic countersteer and applied to a narrow tilting vehicle that will then
automatically actively  optimise its tilt position suitable for the curved path and speed of the vehicle.

*  Direct tilt control [DTC] is tilt force that can be applied using the lateral spacing of wheels as the support for the
application of the force.  DTC  has the advantage that tilt control is not compromised if traction is lost between the
tyres and the road as is the case for countersteer tilt control.

* A combination of  simple steer driver input, DTC and automatic countersteer tilt assist is becoming accepted as
a preferred method. This combination allows an actively optimised tilt position fixed independent of traction
conditions that can allow a narrow vehicle track suitable for urban transport.

                                    SUMMARY OF THE INVENTION and  PRIOR ART.

This invention shows that the tilt of the vehicle may be automatically  created/assisted  by  applying a  braking
force  to  countersteer  steerable wheels.
A method to achieve this is to provide steerably connected laterally spaced front  wheels with an offset to the
contact patch on each wheel so that when a braking force is applied to the contact patch of one  wheel  the wheel
set is countersteered .

Methods have been described in prior art of  brake steer of non tilting vehicles [motorcars] to:
[a] initiate and maintain a driver  desired  curved path directly  or
[b], to adjust the  driver  desired curved  path automatically to reduce dangerous roll moments  away from the
driver's desired curved path.

In these vehicle systems  roll moments can never be applied to create positive roll to  position  the vehicle
c of g to the inside of the  vehicle centerline as the vehicle travels on the drivers required curved path.

In contrast,  the application of brake countersteer can allow actively  created  tilt of a tilting vehicle section to
position the vehicle c of g to the inside of the vehicle centerline displaced in the direction of the drivers required
Brake steer can also be combined with brake countersteer in a tilting vehicle  control system to steer the
steerable wheels positive in the direction of the drivers desired path, at speeds where brake countersteer is not
desired. Brake steer systems will be described later.
  Brake Countersteer Systems.
Brake countersteeer principles will  now be described as they might be applied to tilting  vehicles  described in
WO2005/075278 .[James] and US6435522 [Carver] however, the  application of  these  principles to other  tilting
vehicle systems is in no way limited by these specific references.
In the  vehicles described in WO2005/075278  the connection between the driver and the front wheels is
resilient.  There is no conventional steer connection between the driver and the steerable wheels. The steerable
wheels are dynamically directed/restrained as a result of the driver actively directly tilting the vehicle [DTC]. The
wheels are free to castor [FTC] and being attached to the tilting section of the vehicle they tilt and steer to the
ideal path for the tilt angle of the vehicle and the speed of the vehicle. This characteristic is  described as a  tilt/
steer and in this example it is the " steer means" for the vehicle to follow the drivers directed path.
Because of this resilient directing/ restraint of the front  steerable wheels in this vehicle, there is an opportunity to
apply  countersteer torque to the front wheels against any existing resilient directing/restraining torques, so to
induce the wheels into a countersteering position. This is a " tilt means"   to create a tilt torque in the direction of
the drivers directed path.
Brake countersteer is a tilt torque creating method that  has benefits over previous systems . One particular
benefit is the ability to apply  torque control remotely and effectively to the steerable wheels.
It is  a convenient arrangement that can utilise existing components.

                                    BEST WAYS TO PERFORM THE INVENTION
In  Fig1, a generally  suitable wheel  arrangement  is illustrated. The wheel [1] is steerable around its steer axis
[2]. The steer axis is defined by upper and lower ball joints [2a]. When a braking force is applied to the wheel its
reaction point is the contact patch of the tire [3]. Because the contact patch is offset radially from the steer axis as
illustrated by [4][ FIG 1], when a brake force is applied  this causes a torque to be created to steer the wheel
about its steer axis.   As the two front wheels are steerably connected  by track rod [19] both are steered.

The application of brake countersteer to a tilting vehicle  will always have specific  system requirements.
Fig 2  shows a manual tilt system applied to a vehicle of  type WO2005/075278.
The driver applies a manual force [DTC] to tilt the vehicle via his control element  [5 ] which is connected to rotate
the parallelogram cross arms [6] about their centrally located pivot axes [6a].  The control element is  rotatably
mounted on the vehicle tilting section [20 ] and connected to rotate the  drive pulley wheel [8] which is also
mounted to the tiltable vehicle section. The drive pulley wheel [8] is connected to the cables [7] to drive the cables
which are led around pulley wheels [9], also mounted on the vehicle tilting section, and then the cables attach to
the lower parallelogram cross arm to create a right tilt of the vehicle when a right turn of the control element is
applied by the driver [as viewed by the driver] and vice versa.  A chain and sprocket drive system may be used if
Each wheel steer axis is defined by ball joints attached to the ends of the parallelogram cross arms to complete
the parallelogram structure. It will be appreciated that the parallelogram cross arms form a  non tilting vehicle
section. The front parallelogram tilting linkage is shown only in basic form as this type of wheel support system is
well known in the art. It provides the tilting action for the " tiltable vehicle section". The tiltable vehicle section is
supported by a rear wheel or by 2 rear wheels as desired. Many rear wheel arrangements that allow  tilting
vehicle sections have been fully described in prior art. Various front wheel supporting tilting linkages may be
applied to the front of the vehicle and these are also well known.
The pulley / chain sprocket arrangement is a convenient way to transmit driver torque and control position  to  the
parallelogram and so to tilt the vehicle in a manner reflective of driver input on the control element. The vehicle
then steers automatically as a result of the tilt/steer of the castoring wheels as has been describe in
WO2005/075278. Various connection designs can be used between driver input and vehicle tilt action.

Two hydraulic piston /cylinders [ 10 ] are fitted one to each control cable [one side only is shown]. The control
cable is attached to the piston and the cylinder is  pivotally attached to the cross arm.  A reaction spring [13] sits  
against the piston [14] and regulates the movement of the piston according to the force applied by the control
cable, or in other words the torque applied by the driver on the control to direct tilt the vehicle This assembly
becomes the "brake controlling elements".  
The spring  is arranged to  modulate the force that the driver applies to force tilt the vehicle and converts  some
force to hydraulic pressure which  is  then connected by hydraulic delivery  lines [11 ]one to each wheel disc
brake caliper [12 ][again one side only is shown]. The caliper and disc are the " front wheel brake  elements".

As the driver applies a torque to his control to tilt the vehicle say right [ as illustrated by the inclusion of these
parts only in the drawing], after a certain force level has been applied the spring has compressed  and causes
hydraulic oil to be pressurised by the movement of the piston in the cylinder. This process is "automatic" and
requires no additional actions from the driver other than the simple directing of the control element. This oil is
connected to the brake caliper to cause a braking effect on the appropriate wheel disc brake [ the left side] to
cause a vehicle  countersteer left  and so a  tilt  torque [ right]  to assist the drivers applied  torque [right] on the
control. The two front wheels being steerably connected with a track rod [19] means that both wheels steer
together whenever one or the other is braked.
Because the force applied to  brake the wheel depends on the resistance that the driver finds in his control as he
attempts to tilt the vehicle [the tilt mass inertia], the system operates with automatic closed loop feedback .
Clearly , both rest inertia and moving inertia of the tilt mass will create signals which will be converted to brake
When the vehicle tilting action has ceased, the force to maintain its new  tilted steady state is considerably less
[potentially zero], than the force required to overcome tilt inertia and initiate tilt.  The spring value is set so that in
a  vehicle steady state there is no/ virtually no braking effect and so no torque is generated on the steerable
wheels due to the system being described in this invention. The wheels then steer due to the natural
characteristic of a tilted castoring wheel as has been described in prior art. This is the "vehicle steer means".
Other prior art vehicles use similar resilient restraint of their steerable wheel/s  for example see US6435522
[Carver]. Here there is an automatic countersteer input applied by an active hydraulic cylinder attached between
the front wheel/s and the vehicle frame arranged to apply a force between the cylinder attachment point on the
vehicle frame and the front wheel/s steer  lever arms so to apply a torque to the wheels steer axes. In this
example a brake countersteer system of this invention could replace the cylinder arrangement or augment it when
the vehicle has two front wheels. Clearly the brake countersteer system of our invention uses a fundamentally
different and novel principle to apply  torque about the steer axis. It must be clear that other forms of brake force
may be employed for example electric systems  etc

Fig 3 shows a further variation applied to a James type system which was also  described in WO2005/075278
where a  hydraulic tilt servo is fitted to power assist the drivers manual force applied to the control  element to tilt
the vehicle. In this version a servo valve [15] between driver input and vehicle tilt action, reacts to driver applied
torques on the control element, and directs hydraulic pressure to the appropriate actuators to power assist the
tilt. In this example the pressure in the tilt actuators is also fed directly to the appropriate brake as required to
produce a tilt assisting countersteer of the vehicle.
Other  methods for the application of brake countersteer can be contemplated. The application of the braking
force to create countersteering torque to then create tilting torque may be regulated by computer generated
control signals or other methods.

                             Brake positive steer systems or "vehicle steer means":

As previously mentioned it may be convenient to use existing wheel braking components  to apply a positive steer
torque at certain points in the vehicle control phase . At low speeds particularly there may be no useful role for
countersteer because manual direct tilt may be sufficient to overcome rest inertia of the tiltable section of the
vehicle. This is because at low speeds there is not much tilt required in any given time period of control input, and
there is more positive wheel steer required. This fundamental principle of low speed positive steer torque  has
been fully described in WO2005/075278  and the principle here described will show the use of brake components
as the "variable force steer transmitter" [a term used in that prior art document]. In this document it is  termed a
"variable brake force element".

Fig 4 shows a low speed positive steer system activated by brake. In this system an "indicator of vehicle tilt
position"[15]  is connected to apply electrical  energy to the hydraulic pump[16 ] which is the "variable brake force
transmitter". The pump is driven by electric motor[17].  When the tilt position is to the left of vertical as determined
by the indicator of vehicle tilt position, the supply has positive polarity and when tilted to the right it has negative
polarity [for example]. This causes pump rotation according to tilt position left or right with zero influence in the
vertical tilt position. The pump pressure is regulated by a vehicle "speed sensitive control signal transmitter" [18]
that varies the voltage available to the motor that drives the pump.  Voltage increases with reducing vehicle
speeds, and so, pressure output from the pump increases  with  reducing vehicle speeds. The two output ports
are connected  to brake calipers one  port to one side wheel brake caliper [12] and the other port to the other
side [12a]. Tilt left produces pressure directed to the left caliper to urge the wheel set left, tilt right produces
pressure directed to the right caliper to urge the wheel set right, and, vertical tilt produces no pressure as the
pump is not active.

Other methods may be used to generate the  front wheel brake control for example electrically operated methods
using solenoids or similar means. The indicator of vehicle tilting action may take various forms.