Braking system for a powered two-wheeler
The invention relates to a braking system for a powered two-wheeler, comprising
• a brake fluid reservoir;
• a brake lever;
• a main braking cylinder;
• a wheel brake connected by a hydraulic braking connection line to the main
braking cylinder;
• a motor-driven pump;
• a normally open valve arranged between the pressure side of the pump and
the brake;
• a normally closed valve arranged between the braking connection line and
the suction side of the pump.
The invention further relates to a corresponding method of operation.
For powered two-wheels such as motor cycles, braking systems with ABS
functionality provide safety to the driver in critical situations. The brake lever is
typically connected to a hydraulic master cylinder which comprise one enclosure,
while the valves and a low pressure accumulator are enclosed in a second housing.
For both enclosures, suitable mounting places need to be found. These braking
systems are realized with high assembly time and cost.
The current two-devices brake systems with separate control and actuation units
are also expensive. Current closed-loop ABS control units can cause high
vibrational noise, hard lever feeling (especially during twice apply), excess

movement of the brake lever during ABS control functions,
and low deceleration & instability of the vehicle while Mu Jump-in.
The term "two-wheeler" especially denotes motorcycles or motor scooters or
E-bikes. The wheel brake is preferably built as a front wheel brake.
The object of the invention is to provide a braking system which reduces or
eliminates the described disadvantages. It is another object of the invention to
provide a modular braking system which is easy to assemble and to mount in a
two-wheeler. Moreover, a corresponding method of operation is provided.

In a first aspect, the invention relates to a braking system for a powered two-wheeler,
comprising
• a brake fluid reservoir;
• a brake lever;
• a main braking cylinder;
• a wheel brake connected by a hydraulic braking connection line to the main
braking cylinder;
• a motor-driven pump;
• a normally open valve arranged between the pressure side of the pump and
the brake;
• a normally closed valve arranged between the braking connection line and
the suction side of the pump,
whereby the main braking cylinder, the normally closed valve, the normally open
valve and the pump are arranged in a common housing. Especially all components
except the brake lever and the cable assembly are arranged in the housing.
Preferred embodiments of the invention are described in the dependent claims and
the description.
Preferably the brake lever is connected to the main braking cylinder by a cable
assembly, especially at least one steel cable. The braking system preferably
comprises a control unit (ECU) for operating the valves.
Advantageously in the hydraulic braking connection line a mechanically operated
valve is arranged which on a control side is connected to the pressure side of the
pump, whereby the mechanically operated valve closes when the pressure at the
control side is larger than the pressure of the main braking cylinder. The
mechanically operated valve also is arranged in the common housing.
Preferably the hydraulic braking connection line is directly, especially without a
low-pressure accumulator, connected to the reservoir and the suction side of the
pump via a normally closed magnetic valve.
The pump advantageously on its suction side is directly connected to the reservoir.

Preferably the pump on its pressure side is connected to the brake via a normally
open magnetic valve.
In a preferred embodiment, the brake is a front brake associated with a front wheel
of the powered two-wheeler.
In a second aspect, the invention relates to a method for operating a braking system
described above, whereby during normal braking while braking fluid is pushed from
the main braking cylinder through the mechanically operated valve, the normally
open magnetic valve is put to an open state and the normally closed magnetic valve
is put to a closed state, and whereby flow of braking fluid from the brake to the
normally open valve is hindered by a check valve.
The terms that a valve is actuated to a certain state or put into a certain state or
similar expressions encompass the condition that the valve already is in that state
and no active control operation is performed.
Preferably, for holding brake pressure, the normally open magnetic valve is closed
and the pump is actuated to build up pressure on the control side of the
mechanically operated valve with a pressure larger than the pressure of the main
braking cylinder such that said mechanically operated valve closes.
Advantageously, for release of braking pressure, the normally closed magnetic
valve is opened, allowing braking fluid to flow to the reservoir, and whereby
simultaneously the mechanically operated valve and the normally open magnetic
valve are closed.
In a preferred embodiment, for a driver-independent pressure increase in the brake,
the normally closed magnetic valve is closed and the normally open magnetic valve
is opened and the mechanically operated pressure valve is closed and the pump is
actuated.
Advantageously, when the driver releases the brake lever, the pump is stopped if it
is running and the normally open magnetic valve is opened and the normally closed
magnetic valve is closed.
The advantages of the invention are especially as follows. The design of the
proposed braking system leads to a reduction in product cost, a reduction in

assembly time. It leads to a reduction in Noise due to vibration and flow stream. A
hard lever feel is eliminated and the brake lever movement is minimized.
Deceleration and vehicle stability are improved during Jump-in.
In the following significant changes properties of the proposed design are described
which reduce the product cost. Both actuation and control functions related
components are constructed within one box / one common housing and hence
separate enclosures for the master cylinder and the ABS modulator valve are
eliminated. Also, the one-box-integrated brake system reduces the packaging
design effort, assembly time and labor cost for the customer. The commonly
employed low pressure accumulator is eliminated and release of wheel pressure is
directly connected to the brake fluid reservoir. The commonly used hydraulic
connection from the handlebar to the ABS control device is replaced by steel wire
cable.
The braking system leads furthermore to a reduction in vibration and flow stream
noise. Motor and pump need not to run at higher speed especially at low Mu
(Jump-in) as there is no need of evacuation of a low pressure accumulator (LPA) as
it has been eliminated in the proposed design. However, motor and pump still can be
at controlled speed to feed the brake fluid volume to wheel calliper during an ABS
control cycle.
The orifice of the mechanically operated normally open valve is preferably built
larger than the orifice of current electronically controlled magnetic valves {normally
open type) and hence chance for flow stream noise {annoying damping noise
caused by the valve orifice) even at high viscosity of the brake fluid can be avoided.
Additionally, the elimination of hard lever feel can be achieved. The pressure at the
master cylinder and the brake calliper shall be the same at any point of time while
demanding high pressure gradients even at twice apply condition as the orifice of
the mechanically operated normally open valve can be built larger than for current
electronically controlled magnetic valves {normally open type).
During ABS control cycles, the master cylinder is isolated from the brake calliper
using the mechanically operated normally open type valve. Hence, the reaction
force to the driver due to pump re-flow and pressure ripple is eliminated.
A further advantage is the strong reduction of brake lever movement. During ABS
control cycles, the master cylinder is isolated from the brake calliper using by the

mechanically operated normally open type valve. Hence, the reaction force and its
corresponding lever movement to the driver due to pump re-flow and pressure ripple
are eliminated.
Deceleration and vehicle stability during jump-in are improved. In the proposed new
design of the braking system, the low pressure accumulator is eliminated and the
delivery of the normally closed valve is directly connected to the brake fluid reservoir
and hence there is no need of evacuation of the LPA by the pump driven by the
motor. With this, reduction in wheel pressure shall be achieved with no time delay
from the time of NC valve actuated. Thus, the time to wheel re-acceleration shall be
very low which helps to keep the vehicle stability in control even in low Mu road
surface condition.
The braking system allows a modular design using different sizes of single master
cylinder piston diameters and valves to suit brake device for a wide range of E-bikes
and motor cycles.
A preferred embodiment of the invention is described in connection with a drawing.
In this drawing, in a schematic style,
FIG. 1 shows a braking system in a preferred embodiment during normal
braking;
FIG. 2 shows the braking system according to FIG. 1 during a pressure
holding phase in an ABS control cycle;
FIG. 3 shows the braking system according to FIG. 1 during a pressure
releasing phase in an ABS control cycle;
FIG. 4 shows the braking system according to FIG. 1 during a pressure
increasing phase in an ABS control cycle; and
FIG. 5 shows the braking system according to FIG. 1 during brake release.
Same parts in the FIGs are labelled with identical reference numbers.
In FIG. 1 a braking system 30 is shown during normal or regular braking. The
braking system 30 comprises a brake lever 10 which is connected to a single master

cylinder 7 by a cable assembly 9 which in the preferred embodiment shown is a
single steel cable. A wheel brake 11 which is built as a front wheel brake is
connected by a hydraulic braking connection line 24 to the main braking cylinder7.
Amotor-driven pump 3 is provided, whereby a normally open valve 1 is arranged

brake 11 to cylinder 7 and prevents it in the opposite direction.
The braking cylinder 7, the normally closed valve 2 and pump 3 are arranged in a
common housing 26 or one box. Especially all components except brake lever and
cable assembly are arranged in the common housing.
During normal braking, the driver applies the front brake 11 by pressing the brake
Lever 10. Thereby force is transferred to the One box device via the cable assembly
9. The single circuit master cylinder 7 converts driver force into pressure. Thus,
pressurized fluid volume is pushed to the front calliper 11 through the mechanically
operated normally open type valve 6. Calliper 11 converts the brake pressure into
brake force and thus the deceleration of the vehicle is achieved. The effectiveness
of braking is directly proportional to the lever force exerted by the driver. The release
of braking is to happen upon remove of brake force on the lever by the driver.

The orifice diameter in the mechanically operated master cylinder isolation valve 6 is
preferably built larger than orifices of electronically controlled magnetic valves
current ABS systems for powered two-wheelers. The orifice dimeter depends on the
calliper size of the vehicle. Preferably it is equal to or larger than 0,7 mm. Hence,
even at higher flow rate condition, flow can be established without any restriction at
valve 6 and hence hard lever feel at driver can be avoided. Also, reduction in time to
wheel lock compared to current ABS systems can be achieved as there is no time
delay in pressure between master cylinder 7 and calliper / brake 11 when a high
pressure gradient is demanded by the driver. In the preferred embodiment, all
components except the brake lever and the cable assembly are arranged in the
common housing 26 or box.
FIG. 2 shows the braking system 30 for a pressure hold cycle (in 2 steps) when ABS
control cycles are taking place.
It is assumed that the front wheel is attaining slip due to various factors including
excess brake force exerted by the
driver. The wheel slip is continuously monitored and sensed by wheel speed
sensors (not part of proposed invention) and communicated to an ECU (not shown)
being part of braking system 30.
The next step in the ABS control function is to maintain the wheel pressure to
prevent further wheel slip. In the proposed braking system 30, the ECU actuates the
electronically controlled normally open valve 1 to a closed state and further actuates
the motor and the pump 3. Pump 3 sucks the fluid from the reservoir 8, and
correspondingly pressure is built in the delivery line of the pump 3 and acts on one
side of the differential pressure acting plunger/piston of the mechanically operated
normally open valve 6 and changes its position to the closed state as the pressure
developed by pump 3 (reflow) is greater than the pressure of the single master
cylinder 7 acting other side of pressure differential plunger of valve 6. Hence the
pressure connection between the single master cylinder 7 and the wheel cylinder I
brake 11 is disconnected and thereby pressure in the wheel calliper / brake 11 is
further maintained.
FIG. 3 shows the braking system 30 for pressure release when ABS control cycles
are taking place. It is assumed that the front wheel is attaining further slip and this
time it is beyond acceptable range and the ECU detects the same with the input
signals from the corresponding respective wheel speed sensor. Further to the
detection, the ECU actuates the normally closed type magnetic valve 2 to an open

state and allows pressure in the wheel calliper to be released to the reservoir 2 to a
level to allow wheel to re-accelerate. In this condition, valves 1 and 6 remain in
respective closed position as it is being actuated by ECU and pressure due to pump
re-flow respectively.
With this proposed design, re-acceleration of the wheel shall be achieved in shorter
time compared to current brake systems. Hence it is possible for drivers to achieve
better deceleration and to obtain better control on their vehicle especially at jump-in.
The term jump-in denotes the situation when the vehicle enters to low Mu surface
from high Mu with brake applied condition. The term Jump-out correspondingly
denotes the condition when the vehicle enters to high Mu surface from low Mu with
brake applied condition.
FIG. 4 shows the braking system for pressure increase cycle when ABS control
cycles are taking place.
Further to pressure release cycle, it is assumed that the front wheel is at full
re-acceleration (low slip). To meet the driver deceleration demand, it is necessary to
bring back the wheel to an acceptable slip range by increasing pressure at its
calliper. For this, first the ECU actuates valve 2 to closed state to stop flow of fluid to
reservoir and then actuate valve 1 to open state to allow pressurized fluid volume to
calliper from pump delivery.
During this action, valve 6 remains closed which means there is no pressure
connection between calliper and master cylinder due to higher pump pressure on
differential pressure acting plunger of valve 6. Furthermore, pump 3runs
continuously and supplies pressurized fluid volume to the calliper throughout the
ABS cycles and until driver initiates for brake release. Effects (brake lever
movements and its hard feel) due to pump pulsation (pressure ripple) during ABS
cycle are isolated from the single master cylinder 7 and the driver with support of
valve 6 and its position. With this, the driver can have higher comfort (like normal
braking) while ABS system is modulating the brake.
FIG. 5 shows the braking system 30 during brake release. First, the driver releases
the brake lever 10 causing reduction in pressure at the single master cylinder 7.
Meanwhile the ECU stops the pump 3 from running and thus brings the
mechanically operated NO type valve 1 to an open position.

Brake fluid in the calliper is returning to the master cylinder 7 through valve 6 and its
integrated check valve 28. Similarly, brake fluid in the pump reflow circuit also
returns to the master cylinder through check valve 14 and valve 6.
Finally, very low fluid pressure will get trapped in the pump re-flow circuit. However,
trapped pressure and fluid volume is important to minimize response time to close
the valve 6 during the next ABS cycle. Pressure trapped in the pump re-flow circuit is
not high enough against the return spring of differential pressure acting plunger of
the valve 6. Hence, the valve 6 will remain in an open position.

We Claim :
1. Braking system (30) for a powered two-wheeler, comprising
• a brake fluid reservoir (8);
• a brake lever (10);
• a main braking cylinder (7);
• a wheel brake (11) connected by a hydraulic braking connection line (24) to
said main braking cylinder;
• a motor-driven pump (3);
• a normally open valve (1) arranged between the pressure side of said pump
(3) and said brake (11);
• a normally closed valve (2) arranged between said braking connection line
and the suction side of said pump (3),
characterized in that
said main braking cylinder (7), said normally closed valve (2), said normally open
valve (1) and said pump (3) are arranged in a common housing (26).
2. Braking system (30) according to claim 1, whereby said brake lever (10) is
connected to said main braking cylinder (7) by a cable assembly (9), especially at
least one steel cable.
3. Braking system (30) according to claim 1 or 2, whereby in said hydraulic
braking connection line a mechanically operated valve (6) is arranged which on a
control side is connected to the pressure side of said pump (3), whereby said
mechanically operated valve (6) closes when the pressure at said control side is
larger than the pressure of said main braking cylinder (7).
4. Braking system (30) according to one of the claims 1 to 3, whereby said
hydraulic braking connection line (24) is directly, especially without a low-pressure
accumulator, connected to said reservoir (8) and the suction side of said pump (3)
via a normally closed magnetic valve (2).
5. Braking system (30) according to one of the claims 1 to 4, whereby said pump
(3) on its suction side is directly connected to said reservoir (8).

6. Braking system (30) according to one of the claims 1 to 5, whereby said pump
(3) on its pressure side is connected to said brake via a normally open magnetic
valve (1).
7. Method for operating a braking system (30) according to claim 1 to 6, whereby
during normal braking while braking fluid is pushed from said main braking cylinder
(7) through said mechanically operated valve (6), said normally open magnetic
valve (1) is put to an open state and said normally closed magnetic valve (2) is put to
a closed state, and whereby flow of braking fluid from said brake to said normally
open valve (1) is hindered by a check valve (14).
8. Method according to claim 7, whereby for holding brake pressure, said
normally open magnetic valve (1) is closed and said pump (3) is actuated to build up
pressure on the control side of said mechanically operated valve with a pressure
larger than the pressure of said main braking cylinder (7) such that said
mechanically operated valve closes.
9. Method according to claim 7 or 8, whereby for release of braking pressure,
said normally closed magnetic valve (2) is opened, allowing braking fluid to flow to
the reservoir (8), and whereby simultaneously said mechanically operated valve (6)
and said normally open magnetic valve (1) are closed.
10. Method according to one of the claims 7 to 9, whereby for a driver-independent
pressure increase in said brake (11), said normally closed magnetic valve (2) is
closed and said normally open magnetic valve (1) is opened and said mechanically
operated pressure valve (6) is closed and said pump (3) is actuated.
11. Method according to one of the claims 7 to 10, whereby, when the driver
releases said brake lever (10), said pump (3) is stopped if it is running and said
normally open magnetic valve (1) is opened and said normally closed magnetic
valve (2) is closed.