FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to a car braking anti-jolt method and apparatus and, more particularly, but not exclusively, to such a system that may work with existing components of a vehicle design.

During deceleration of a vehicle to a stop using the brake, jolting tends to occur during the last part of the deceleration as the vehicle comes to a halt. The jolt is unpleasant in most circumstances and is particularly problematic in traffic jams and public transport where many passengers may be standing, causing anyone not holding tight to lose their balance. The occurrence of a jolt is caused, or significantly influenced, by effects at low vehicle speed. There is a link to a sudden increase in the friction between the tyre and the road during the later stages of deceleration while, at the same time, the friction between the brake pad and the brake disc increases. This results in a sudden increase in force on the wheels, causing instability which is not well damped, resulting in a jolt.

DE-A-44 01 082 discloses a method for preventing the stopping jolt by lowering the pressure in the master cylinder of an electronically-controlled or regulated brake system. In order to maintain braking distance, the possibility is described of briefly increasing the brake pressure before lowering it. The disclosed method does not distinguish between the brake pressure at the front axle and the brake pressure at the rear axle.

In DE-A-101 31 323, the concept is developed of avoiding the stopping jolt by transferring brake pressure from the front axle to the rear axle, or by only lowering the brake pressure at the front axle. Regulation is applied to avoid the stopping jolt substantially during braking on reaching or falling below a vehicle speed threshold value of about 7 to 3km/hr. The vehicle is thus still moving during the activation of the special regulation. It is expressly pointed out that the change in the brake force distribution is cancelled at near or complete standstill of the vehicle.

In the prior art, the cause of stopping jolts is mainly attributed to the above- mentioned sudden increase in the coefficient of friction at low speeds (road/brake coefficient of friction). PCT EP2004 050278 also considers the possibility that the strong deceleration leads to compressing and deforming forces acting on the vehicle and having an impact on the vehicle. A part of these compressing forces leads to the deflection or pitching of the vehicle. Further forces lead, for example, to a slight twisting and/or deformation of the body as well as causing deformation of the tyres, the chassis etc, and thus the '278 disclosure suggests the concept of bringing about a relaxation or de- stiffening of the vehicle by releasing the brakes when the vehicle comes to a standstill. Pressure sensors are installed in the master cylinder or directly on the wheels and the actual pressure at the outlet of the master cylinder is reduced to a factor of 20-60% of the starting brake pressure. The brake pressure reduction is carried out on the rear axle in order to enable braking force modulation on coming to a standstill, but may be reduced simultaneously at certain portions on the front wheels.

A disadvantage of the system disclosed is that special construction is required, which means that the system is difficult to apply to existing vehicles and vehicle designs have to be changed. SUMMARY OF THE INVENTION

The present embodiments use the anti-lock braking system already installed on the vehicle to cause a brief release in brake pressure immediately prior to standstill.

When a vehicle comes to a stop, a deceleration effect may be felt in the vehicle.

As the wheels come to a stop the car body may still have a forward moving momentum which goes through a process of being absorbed by the car suspension system. When the car springs have fully absorbed the forward movement they push the car body backward and the process may be repeated a few times until fully constrained by the car suspension dampers. That is to say, the deceleration power is not fully damped when the vehicle comes to a stop, causing the jolt.

The present embodiments may activate the ABS to release the car brakes after the car has almost or completely stopped and the forward movement is at the final stage of being absorbed by the suspension. The temporary release has the effect of increasing the damping factor of the system, thus reducing the jolt.

According to embodiments of the present invention, there may be provided a vehicle comprising an anti-lock braking system (ABS), the ABS comprising ABS valves on each wheel for controlling braking and an ABS controller for operating the valves, and further having an anti-jolt controller added to the ABS controller, the anti-jolt controller configured to release the ABS valves for a predetermined duration around a time at which the vehicle stops in order to damp the vehicle stop and reduce jolting.

In an embodiment, the anti-jolt controller is configured to operate at below 2kmh.

In an embodiment, the release is for a time of between about 20ms and about

120ms.

In an embodiment, the anti-jolt controller is configured to calculate a time to release the valves based on a speed of the vehicle, a deceleration of the vehicle and a road angle of the vehicle.

In an embodiment, the anti-jolt controller is configured to calculate a number of releases of the valves based on a speed of the vehicle, a deceleration of the vehicle and a road angle of the vehicle.

In an embodiment, the anti-jolt controller is configured to calculate a duration of release of the valves based on a speed of the vehicle, a deceleration of the vehicle and a road angle of the vehicle.

In an embodiment, the ABS has three ABS valves for each wheel such that a wheel may be partly released if two ABS valves are operated and fully released if three ABS valves are operated, the anti-jolt controller being configured to select for each wheel whether to operate two of the ABS valves, three of the ABS valves or a combination of the two, based on a speed of the vehicle, a deceleration of the vehicle and a road angle of the vehicle. An example of the combination case may be that a first activation involves three valves and then in a later activation the number of valves is reduced to two.

In an embodiment, the anti-jolt controller is configured to operate three of the valves on front wheels of the vehicle and two of the valves on rear wheels of the vehicle.

In an embodiment, the anti-jolt controller is configured to obtain speed information of the vehicle from ABS wheel speed sensors.

According to a second aspect of the present invention, there is provided a method of modifying a vehicle having an anti-lock braking system by adding to the anti-lock braking system an anti-jolt controller, the anti-jolt controller being configured to operate the anti-lock braking system upon deceleration to a complete stop to release vehicle brakes just prior to coming to the complete stop.

According to a third aspect of the present invention, there is provided a method of stopping a vehicle, the vehicle having brakes and an anti-lock braking system, the method comprising:

measuring a speed of the vehicle; and

as the speed approaches zero, operating the anti-lock braking system at least once to release the brakes for a pre-calculated duration.

It is noted that in all cases herein the ABS may be part of a computerized braking system in which a computer applies brake pressure, for example without any human intermediary. The computer may operate an actuator which directly controls the brake pressure.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be.

Implementation of the method and/or system of embodiments of the invention can involve performing or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of embodiments of the method and/or system of the invention, several selected tasks could be implemented by hardware, by software or by firmware or by a combination thereof using an operating system.

For example, hardware for performing selected tasks according to embodiments of the invention could be implemented as a chip or a circuit. As software, selected tasks according to embodiments of the invention could be implemented as a plurality of software instructions being executed by a computer or controller using any suitable operating system. Optionally, the computer or controller includes a volatile memory for storing instructions and/or data and/or a non-volatile storage, for example, a magnetic hard-disk and/or removable media, for storing instructions and/or data. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a simplified diagram illustrating a typical Anti-Lock Braking System according to the existing art;

FIG. 2 is a simplified block diagram illustrating an anti-jolt controller added to the controller of an anti-lock braking system according to an embodiment of the present invention;

FIG. 3 is a simplified flow chart illustrating operation of an anti-jolt stopping operation according to the present invention;

FIG. 4 is a simplified graph of deceleration against time for a conventional vehicle stopping operation; and

FIG. 5 is a simplified graph of deceleration against time for a stopping operation using an anti-jolt system according to the present embodiments compared to the same stop with the system turned off.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to a car brake anti- jolt system and, more particularly, but not exclusively, to a car brake anti-jolt system that uses the already installed anti-lock braking system that is present in the vehicle.

A vehicle uses the anti-lock braking system (ABS) in order to reduce or eliminate the jolt experienced as the vehicle comes to a halt. The ABS comprises ABS valves on each wheel for controlling braking and an ABS controller for operating the valves. An anti-jolt controller is added to the ABS controller, and releases the ABS valves for a predetermined duration around a time at which the vehicle stops in order to damp the vehicle stopping operation and thus reduce jolting. The release may be full or partial and is for a short period of time, allowing the wheels to move forward by a few centimeters in order to relieve the tension created on the suspension system and releasing the force in the suspension that would have pushed the vehicle body backward.

When the vehicle has almost come to a stop the present embodiments may release the brake in a combination of partial or full release between the front and rear wheels at the same time. This may allow the wheels to retain forward momentum and fully or partially relieve the tension on the vehicle suspension system, thus increasing the damping and reducing the jolt.

The anti-lock braking system (ABS) is the automobile safety system that allows the wheels on a motor vehicle to maintain tractive contact with the road surface according to driver inputs while braking, preventing the wheels from locking up and ceasing to rotate, and avoiding uncontrolled skidding. It is an automated system that uses the principles of threshold braking and pumping the brake which were practiced by skillful drivers with previous generation braking systems. ABS achieves a much faster rate and better control than a driver could manage.

ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces; however, on loose gravel or snow-covered surfaces, ABS can significantly increase braking distance, although still improving vehicle control.

Since initial widespread use in production cars, anti-lock braking systems have been improved considerably. Recent versions not only prevent wheel lock under braking, but also electronically control the front- to-rear brake bias. This function, depending on its specific capabilities and implementation, is known as electronic brakeforce distribution (EBD), traction control system, emergency brake assist, or electronic stability control (ESC).

For the present embodiments, the ABS provides an avenue for control of the brakes, and is generally available at low speeds, since the standard ABS functions are all carried out at high speeds. The anti-jolt functions of the present embodiments thus do not interfere with the standard functions of the ABS system.

The anti-jolt system may work as follows: The system almost fully releases the brakes by activating most of the ABS valves and then gradually returns brake pressure to the wheel by releasing specific ABS valves at certain times according to information obtained from the acceleration gauge. The release of specific valves at different times may help smooth the return of the brake power. The release process may commence at between 70 - 20 ms prior to the calculated normal stopping point and fully end 100 - 270 ms after the operation start depending on the car deceleration rate and the stopping profile.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

Referring now to the drawings, Fig. 1 illustrates a vehicle 10 which has an anti- lock braking system (ABS). The vehicle 10 is a conventional road vehicle, and may be a motorcycle, a car, a truck, a van, a minibus, a bus, a train or any other road vehicle that may be equipped with an ABS, and has a vehicle body 12 and two or more wheels 14 that come into contact with the road. The ABS comprises an ABS controller 16, and hydraulic unit 17. The hydraulic unit 17 includes a master cylinder, fluid reservoir and actuators which operate ABS valves 18 that operate on the brake lines 20 for each road wheel 14 that is braked. The ABS controller 16 obtains data from speed sensors 22, which may for example be mounted on backing plate 23, and provided for each braked wheel 14, and controls braking by operating the valves 18. The ABS system further comprises a warning light 24 to indicate malfunctions to the driver, and a diagnostic connector 26. The brakes themselves are operated by the driver from brake pedal 28 and push rod 30 which operates the hydraulic unit to apply pressure via brake lines 20 against brake discs 32 mounted on wheel hubs 34. It is noted that while the present embodiments are described in respect of a vehicle with a human driver, driverless cars, in which the brake is always automatically operated are also contemplated. The ABS operates by using valves 18 to temporarily release the pressure in the brake lines and thus release the brakes, and the pressure is restored using the fluid reservoirs and the driver pressing on the brake pedal at the end of the release process. The ABS operates in situations where some of the wheels are rotating at high speeds and others of the wheels have stopped rotating, which indicates wheel lock and skidding.

Referring now to Fig. 2, the present embodiments add an additional feature to the ABS controller 16 which is referred to as an anti-jolt controller 40. The anti-jolt controller releases the ABS valves for a predetermined duration around a time at which said vehicle stops, and thus provides for damping of the vehicle stopping operation, thus reducing the jolt. Fig. 2 shows schematically how the anti-jolt control system may be superimposed on the ABS controller 16. The anti-jolt controller 40 may be a card that is inserted into the ABS controller 16 or incorporated into the ABS ACU, or may be a separate device, but having access to the ABS sensors 22 and being able to actuate the ABS valves 18.

The anti-jolt controller may work as follows: The controller almost fully releases the brakes by activating most of the ABS valves and then gradually returns brake pressure to the wheel by releasing specific ABS valves at certain times according to information obtained from the acceleration gauge. The release of specific valves at different times may help smooth the return of the brake power.

The release process may commence at between 70 - 20 ms prior to the calculated normal stopping point and fully end 100 - 270 ms after the starting point depending on the car deceleration rate and the stopping profile.

Reference is now made to Fig. 3, which is a flow chart illustrating operation 50 of an anti-jolt system according to the present embodiments. The anti-jolt controller obtains a speed reading that is below lkmh - 52. The speed, deceleration and road angle of the vehicle are obtained 54, and used alongside fixed information such as the unloaded weight of the vehicle, to determine a time, a duration and a number of brake releases - 56. Typical timing of the release is when the speed of the vehicle is around 0.5kmh. A typical duration of the process is between about lOOm/s and about 250m/s, and the number of releases may be 1, 2 3 or any suitable larger number. Finally, the brake valves are released and reapplied - 58 as defined in the calculation, in order to achieve a smooth stop.

A typical ABS system has three ABS valves for each wheel, but some systems may have more or less valves. Thus some systems have two valves per wheel. In the three-valve system, a wheel is partly released if two ABS valves are operated and fully released if all three ABS valves are operated. The anti-jolt controller may select for each wheel whether to operate two of ABS valves, three of the ABS valves or a combination of the two, depending on whether the measurements and calculations indicate that full or partial release is needed. In the case of partial braking the two valves to be selected may be explicitly specified. The combination case may for example involve a first activation using all three valves and at some stage reducing the number of valves activated to two.

In a typical stop the anti-jolt controller may operate three valves on front wheels and two valves on rear wheels. In other words full release is provided to the front wheels but only partial release to the back wheels.

As explained, speed information for the anti-jolt controller may be obtained from the ABS wheel speed sensors 22.

The anti-jolt controller may be added to a current vehicle or vehicle design simply by modifying the software within the anti-lock braking system, for example by adding a card or adding extra circuits to the existing ECU or by modifying the firmware on the ECU.

In use, the present embodiments provide a method of stopping, in a vehicle having brakes and an anti-lock braking system, by measuring the speed of the vehicle, and as the speed approaches zero, operating the anti-lock braking system at least once at a pre-calculated time to release the brakes for a pre-calculated duration. The effect of the release is to add damping to the system and thus reduce the jolt experienced on stopping. Fig. 4 is a graph of acceleration against time for prior art vehicles and showing a deceleration stage 60, a wheel stop point 62 and a jolting stage 64 in which the motion is steadily damped but not before four cycles of quite powerful vibration.

Fig. 5 illustrates the application of the present invention to the stopping process in Fig. 4. Graph 70 illustrates the prior art undamped stopping process and graph 72 illustrates the damped process according to the present embodiments. The stages are the same but in graph 72 the powerful low frequency vibrations are missing from stage 64 which is now much smoother.

As explained above, typically the ABS includes a central electronic control unit (ECU) - the ABS controller discussed above, four wheel speed sensors, and at least two hydraulic valves within the brake hydraulics. The ECU constantly monitors the rotational speed of each wheel, and if it detects a wheel rotating significantly slower than the others, a condition indicative of impending wheel lock, it actuates the valves to reduce hydraulic pressure to the brake at the affected wheel, thus reducing the braking force on that wheel. The wheel then turns faster and a skidding situation may be avoided. The process is repeated continuously and can be detected by the driver via brake pedal pulsation. Some anti-lock systems can apply or release braking pressure 15 times per second. Because of this, the wheels of cars equipped with ABS are practically impossible to lock even during panic braking in extreme conditions.

The ECU is programmed to disregard differences in wheel rotative speed below a critical threshold, because when the car is turning, the two wheels towards the center of the curve turn slower than the outer two. For this same reason, a differential is used in virtually all roadgoing vehicles.

There are four main components of ABS: wheel speed sensors, valves, a pump, and a controller.

A speed sensor 22 is used to determine the wheel rotation speed and can also be used to calculate the acceleration or deceleration of the wheel. These sensors use a magnet and a Hall effect sensor, or a toothed wheel and an electromagnetic coil to generate a signal. The rotation of the wheel or differential induces a magnetic field around the sensor. The fluctuations of the magnetic field generate a voltage in the sensor.

There is a valve in the brake line 20 of each brake controlled by the ABS. In some systems, the valve has three positions. In position one, the valve is open, and pressure from the master cylinder, part of hydraulic unit 17, is passed right through to the brake. In position two, the valve blocks the line, isolating that brake from the master cylinder, preventing the pressure from rising further should the driver push the brake pedal harder. In position three, the valve releases some of the pressure from the brake.

In alternative systems there may be a combination of three separate valves rather than three positions of a single valve.

The pump in the ABS is used to restore the pressure to the hydraulic brakes after the valves have released it. A signal from the controller 16 may release the valve at the detection of wheel slip. After a valve releases the pressure supplied from the user, the pump is used to restore a desired amount of pressure to the braking system. The controller may modulate the pump status in order to provide the desired amount of pressure and reduce slipping.

The controller 16 may be an ECU type unit which receives information from each individual wheel speed sensor 22. If a wheel 14 loses traction the signal is sent to the controller 16, the controller may then limit the brake force (EBD) and activate the ABS modulator which actuates the braking valves to turn them on and off.

As discussed, when a vehicle stops a deceleration affect may be felt, and once the wheels 14 of the vehicle have come to a stop the vehicle body 12 may still have a forward momentum which is absorbed by the vehicle suspension system. When the vehicle suspension has fully absorbed the forward momentum the car body is pushed backward by a rebound due to underdamping and the process may be repeated a few times until fully constrained by the car suspension dampers.

The present embodiments may thus release the vehicle brakes after the car has almost stopped or has completely stopped. At such a point the forward momentum of the vehicle is in the last stage of being absorbed by the suspension. The release, which may be full or partial may be for a short period of time and may allow the wheels to move forward by a few centimeters in order to relieve the tension created on the suspension system. The release of the brakes may release the force in the suspension that would have pushed the car body backward, thus effectively increasing the damping factor.

The exact point at which to release the brake may be affected by certain factors such as the vehicle deceleration rate, vehicle mass and the vehicle's road angle or angle with the horizontal, that is the vehicle climbing or descending angle.

Every modern vehicle today is equipped with an ABS system whose purpose is to prevent skidding during braking, in order to keep the car maneuverability under control. The ABS prevents skidding by momentarily releasing the car brakes for a fraction of a second and allowing the wheel to stop skidding and instead relay the steering to the road. The ABS is managed by the controller, as discussed above, and the controller monitors rotation speed of the individual wheels to detect a start of a skid. Using data from the wheels it is possible to calculate the vehicle speed and acceleration or deceleration rate.

Usually the ABS is unused more than 99.9% of the time and would not in any event operate at speeds of less than 20 KMH. Thus, the ABS system is generally available for the anti-jolt system, since emergency braking is over at near zero speed at which the jolt occurs. It is nevertheless possible to determine if the car is in an emergency brake situation. For example, the ABS may indicate that it is operating, or the car deceleration rate may be independently monitored. The present embodiments may be arranged not to activate the anti-jolt if the ABS is active or the deceleration is above a certain level.

When the car is close to coming to a complete stop, and more specifically in the vicinity of less than 0.1 sec to the complete stop, the ABS may be activated by the present embodiments so as to release the brake in a combination of partial and full release between the front and rear wheels at the same time. Such a release allows the wheels to retain forward momentum and fully or partially relieve tension in the vehicle. In this way the jolt may be reduced as the system as a whole is better damped.

The exact time for activation of the brake release, as well as the duration, the number of releases and whether the front or rear wheels are fully or partially released may depend on the different conditions described above. The conditions may be monitored continuously by the ABS controller, which gatherers data from the ABS speed sensors in the wheels, and from acceleration and gyroscope sensors.

The anti-jolt system may begin to operate when the approximate vehicle speed falls below lkmh, and more typically below 0.5kmh. Operation start may be determined based on the vehicle speed as detected using the ABS sensors on each of the four wheels. Vehicle deceleration rate may be calculated either by the change in speed obtained from the ABS speed sensors on the wheels or from an external accelerometer, and the road angle may be detected by an accelerometer microchip. Data on speed, deceleration, and road angle may be used together in order to calculate the exact timing and duration of the system activation, and a change in any of the above values may lead to a change in either or both of the timing and duration of the brake release.

In most modern cars the ABS has three valves for each wheel and it is possible to activate the ABS in two different ways. The first way is to activate all three valves, resulting in the brake pressure being relieved completely. That is to say the wheel rotates freely despite the fact that the driver is pressing the brake pad. The second way involves activating only two specific valves. The result is that the brake force is only reduced but not eliminated.

In a typical operation, the anti-jolt system may be activated at a selected time to release the brake pressure on the front wheels completely, meaning that all three valves are activated for each front wheel. At the same time the rear wheels are released partially by activating two specific valves of the three for each rear wheel. The activation is maintained for a duration of between about lOOm/s and about 250m/s.

The valve activation is for a short time in order to create a feedback affect that damps the vibration and thus reduces the jolt without creating the feeling that the car is sliding instead of stopping.

A control unit can be incorporated into the ABS ECU unit (ABS computer) and thus may reduce the cost and complexly of integrating the system to nothing more than addition or change of the PCB card in the ECU controller. Hence, existing vehicles can be upgraded and newly manufactured vehicles can be provided with the anti-jolt system without making any significant changes to the production line or the brake system.

The traditional ABS system covers an electronic system that modifies the driver's application of the brakes. The present embodiments also cover systems in which a computer applies the brakes, in which the ABS system is a function within the computerized braking system, operating within a dedicated braking computer or within a processor that manages driving of the vehicle.

It is expected that during the life of a patent maturing from this application many relevant ABS and vehicle control technologies will be developed and the scopes of the corresponding terms are intended to include all such new technologies a priori.

As used herein the term "about" refers to ±10%

The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to".

The term "consisting of means "including and limited to".

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment, and the above description is to be construed as if this combination were explicitly written. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention, and the above description is to be construed as if these separate embodiments were explicitly written. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.