Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T17/00—Component parts, details, or accessories of power brake systems not covered by groups B60T8/00, B60T13/00 or B60T15/00, or presenting other characteristic features
  • B60T17/18—Safety devices; Monitoring
  • B60T17/22—Devices for monitoring or checking brake systems; Signal devices
  • B60T17/221—Procedure or apparatus for checking or keeping in a correct functioning condition of brake systems
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/17—Using electrical or electronic regulation means to control braking
  • B60T8/172—Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/32—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration
  • B60T8/56—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force responsive to a speed condition, e.g. acceleration or deceleration having means for changing the coefficient of friction
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T2201/00—Particular use of vehicle brake systems; Special systems using also the brakes; Special software modules within the brake system controller
  • B60T2201/12—Pre-actuation of braking systems without significant braking effect; Optimizing brake performance by reduction of play between brake pads and brake disc
  • B60T2201/124—Rain brake support [RBS]; Cleaning or drying brake discs, e.g. removing water or dirt

Definitions

• the invention relates to a method and a device for the variable adjustment of the braking force in a hydraulic brake system of a motor vehicle according to the preamble of claims 1 and 15, respectively.
• a brake system for motor vehicles which comprises a master cylinder designed as a tandem cylinder, which is actuated by a brake pedal. Furthermore, an auxiliary pressure supply system is provided which comprises a hydraulic pump for generating the required brake pressure and an electric motor which actuates the pump, the hydraulic medium required by the pump being supplied to the wheel brake device for generating the required braking force.
• the brake can be actuated as a function of the wiper actuation.
• DE 44 27 170 Cl discloses detecting the temperature of the brake parts and a braking process in the event ensure that the brake temperature falls below a temperature limit.
• the invention is based on the problem of compensating for a waning braking effect in hydraulic brake systems in a wide range.
• the actual coefficient of friction between the brake disc and the brake lining of a wheel brake characterizes the implementation of the clamping force of the brake caliper m the deceleration force on the brake disc. If the actual coefficient of friction between the brake disc and brake pad falls below the target coefficient of friction, the brake pressure is increased, which can at least partially compensate for a reduced braking power that can result as a result of overheating, wear, or environmental influences such as wetness, dirt, or ice formation. so that there is neither a subjective nor an ective deterioration in braking performance.
• an additional condition is checked before the brake pressure increase to determine whether the actual coefficient of friction lies within a defined stabilization range, which includes a band of coefficients of friction below the maximum desired coefficient of friction. If the actual coefficient of friction is within this stabilization range, the brake pressure is increased. If the actual coefficient of friction is below the stabilization range, it is not advisable to increase the brake pressure for reasons of overload protection; In this case, the brake pressure does not increase and an error or alarm signal is displayed, which indicates to the driver that the brake condition is poor.
• the stabilization range can be predefined or can be determined during operation based on changing status or operating parameters such as the maximum achievable deceleration, temperature of the brake system, wetting of the brake parts with moisture, etc., thereby achieving a high degree of flexibility.
• the stabilization range is divided into a constant range, in which a constant, maximum braking deceleration can be maintained over deteriorating coefficients of friction, and into a gradient range, in which the braking pressure is increased without reaching the maximum braking deceleration.
• the constant range in this case comprises higher coefficients of friction than the gradient range, both areas expediently completely fill the stabilization range.
• the boundary between constant range and gradient range - the lower coefficient of friction of the constant range - is advantageously set variably. It is particularly expedient to shift the lower coefficient of friction of the constant range in the direction of the lower limit of the gradient range with increasing temperature of the wheel brake device, whereby the Constant range is expanded at the expense of the gradient range. This shift in the lower coefficient of friction of the constant range results in a constant deceleration over an increasing range of small coefficients of friction without further shifting the lower limit of the stabilization range, which is used for functional reliability, in the direction of smaller coefficients of friction.
• the brake pressure is subjected to a correction factor greater than one, which is expediently calculated depending on the measured or calculated actual coefficient of friction, the target coefficient of friction and the lower limit of the current range - the gradient range or the constant range.
• the correction factor advantageously increases linearly in the constant range from value 1 with decreasing friction values and then decreases continuously and linearly in the gradient range with decreasing friction values until value 1 is reached at the lower coefficient of friction of the gradient range.
• the correction factor increases in the constant range, the smaller the lower coefficient of friction of the constant range, the more the lower coefficient of friction of the constant range is shifted towards the lower limit of the gradient range. This can take into account the fact that with increasing temperature, an increasing brake pressure is required to compensate for the temperature-related brake fading.
• the friction values r 1 plotted on the abscissa are divided into different areas between the brake disc and the brake lining of a wheel brake m. Between a lower limit ⁇ m ⁇ n and a target friction coefficient ⁇ so ⁇ , which at the same time marks the usually achievable maximum coefficient of friction between the brake disc and brake pad, extends a stabilization area
• the stabilization area 1 is subdivided into a lower gradient area 2 and an upper constant area 3, the gradient area 2 between the lower coefficient of friction ⁇ m ⁇ n marking the lower limit of the stabilizing area 1 and the coefficient of friction ⁇ ⁇ ow and the lower limit of the constant area 3 Constant range 3 between the coefficient of friction and the target coefficient of friction ⁇ so ⁇ .
• the gradient area 2 and the constant area 3 directly adjoin one another, both areas
• the correction factor f k0 rr serves to compensate for reduced coefficients of friction in order to ensure a desired vehicle deceleration even in the case of deteriorated coefficients of friction.
• the correction factor f k0 rr is multiplied by the brake pressure calculated by the electro-hydraulic brake and corresponding to a certain pedal pressure of the driver, whereby a declining braking effect can be compensated for.
• the correction factor fo rr only has a value greater than one within the stabilization area 1, outside of the stabilization area 1 the value of the correction factor is equal to one, so that an increase in brake pressure is only carried out within the stabilization area 1 for actual friction values ⁇ ls r, not however above the upper limit of the stabilization area 1, the target coefficient of friction ⁇ so ⁇ . and below the lower limit of the stabilization area 1, the lower coefficient of friction ⁇ min .
• the determination of the correction factor as a function of the actual actual coefficient of friction and the multiplication of the correction factor by the brake pressure corresponding to the pedal pressure of the driver and determined in the braking device offers the advantage that a reduction in the actual coefficient of friction can be reacted to immediately and without loss of time.
• the braking system can be kept at its original, constant braking level at least within the constant range 3, regardless of the physical cause of the loss of friction.
• the value of the correction factor is Fcorr greater than one, wherein the function of the correction factor in dependence on the coefficient of friction at the lower and the upper limit value ⁇ m ⁇ n, ⁇ S oi ⁇ at one starting at the located between gradient region 2 and constant region 3 Coefficient of friction ⁇ m ⁇ n increases linearly.
• the coefficient of friction ⁇ min the function of the correction factor takes a maximum, the function of the correction factor takes a triangular shape with a linear increase.
• the correction factor fkorr is calculated as a function of the instantaneous coefficient of friction ⁇ 13t according to the linear relationship
• the current actual coefficient of friction ⁇ i3t is advantageously determined from the measured or calculated vehicle deceleration and the currently applied brake pressure. But it can also be expedient, the actual friction- ⁇ _ st from a comparison between the desired and actual vehicle deceleration to calculate.
• a minimum coefficient of friction ⁇ A i ar m is entered below the lower limit value ⁇ min of the stabilization area 1. If the current actual coefficient of friction ⁇ reaches the minimum coefficient of friction ⁇ A iarm.- an error signal is generated and displayed to the driver as an indication of a brake defect or a dangerous situation.
• the correction factor f kor r can either be as shown can be used to multiply the determined actual coefficient of friction ⁇ ⁇ st , which is incorporated into the calculation of the required hydraulic brake pressure, or can be used directly to multiply the brake pressure or to multiply another quantity influencing the brake pressure or vehicle deceleration.
• the device for variably adjusting the braking force m of the braking system of a motor vehicle comprises a regulating and control device, m to which the control signals required to set the desired braking pressure are generated.
• Regulating and control unit of the actual coefficient of friction ⁇ ls supplied as an input signal and it is the actual coefficient of friction ⁇ is calculated from Meß counselor 13t and with a desired coefficient of friction ⁇ 30 n compared. Falls below the actual coefficient of friction ⁇ 13t the desired coefficient of friction ⁇ as ⁇ m impermissible manner and also is the actual friction factor ⁇ lst within the stabilization range, the regulating and control unit generates a control signal with which the braking pressure f to a by the correction factor k0 rr multiplied value is increased.
• a low braking pressure of advantageously around 3 bar to 8 bar to be built up in the wet, even when driving unbraked, in order to create a water film by applying the brake pads to the brake discs. displaced on the brake discs.
• the low brake pressure ensures that there is no noticeable, unwanted vehicle deceleration.
• the engine torque is increased, for example by increasing the amount of fuel injected and the corresponding air supply, in order to compensate for the braking torque and the vehicle speed to keep constant.
• the risk of corrosion in the brake system can be reduced by building up a low brake pressure without noticeable vehicle deceleration, as a result of which the temperature of the brake system can be stabilized at a low level, which is harmless to the brake material, even when driving unabated.
• the temperature of the brake system can be stabilized at a low level, which is harmless to the brake material, even when driving unabated.
• the moisture from the wheel brake is largely removed or kept away.
• the brake disc is cleaned of dirt and road salt.
• the build-up of the brake pressure during unbraked driving can be carried out at intervals, the length of the intervals being determined by the length of driving times without braking initiated by the driver, by the windshield wiper setting and by the braking load of a previous braking operation.
• the boiling point of the brake fluid can be increased by deliberately including a residual pressure in the brake system, thereby preventing the outgassing of the fluid.
• There is a risk of overheating in the brake system in particular in the case of very frequent and / or strong brake applications with a simultaneous low accelerator pedal operation, which can be counteracted by including the residual pressure.
• the operating time of the brake fluid since the last brake fluid change can be taken into account as a further parameter. The driver is advised of the overloading of the brake system.

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• Engineering & Computer Science (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Braking Arrangements (AREA)
• Regulating Braking Force (AREA)
• Valves And Accessory Devices For Braking Systems (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=7901315

Family Applications (1)

Country Status (6)

Cited By (5)

Families Citing this family (18)

Citations (5)

Family Cites Families (4)

• 1999
  • 1999-03-17 DE DE19911902A patent/DE19911902C1/de not_active Expired - Fee Related
• 2000
  • 2000-01-25 JP JP2000605468A patent/JP2002539032A/ja active Pending
  • 2000-01-25 WO PCT/EP2000/000541 patent/WO2000055024A1/de not_active Ceased
  • 2000-01-25 ES ES00910608T patent/ES2199141T3/es not_active Expired - Lifetime
  • 2000-01-25 EP EP00910608A patent/EP1159176B1/de not_active Expired - Lifetime
  • 2000-01-25 US US09/936,614 patent/US6671604B1/en not_active Expired - Fee Related

Patent Citations (5)

Non-Patent Citations (1)

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