JP4749670B2 - Method for determining or correcting the maximum boost characteristic curve of a vacuum brake booster - Google Patents

Description

  The present invention relates to a method for determining or correcting a maximum boost characteristic curve of a vacuum brake booster of a vehicle brake device.

  Furthermore, the present invention comprises a negative pressure casing, which is divided into at least one negative pressure chamber and at least one working chamber by at least one movable partition wall, and further reduces the pressure of the vacuum brake booster. The invention relates to a correction device for a characteristic curve of a vacuum brake booster of a vehicle brake device, comprising a sensor unit for sensing.

  The brake pressure is generated by pedal force and auxiliary force. This auxiliary force arises from the pressure difference between the working chamber of the vacuum brake booster and the vacuum chamber (negative pressure chamber). In this case, the ratio of the assist force continuously increases to the maximum boost point according to the structurally determined boost factor. At the maximum boost point, the maximum pressure differential is achieved. A further increase in the output is possible only by an unfamiliar increase in braking force, in particular pedal force. The maximum boost point is a predetermined hydraulic pressure (maximum boost pressure) of the master brake cylinder following the vacuum brake booster.

  The term “maximum boost characteristic curve” here and below refers to the vacuum or negative pressure in the vacuum chamber or negative pressure chamber of the vacuum brake booster and the maximum brake pressure or maximum braking force (maximum boost pressure or maximum It means the characteristic curve of the vacuum brake booster indicating the relationship with the boost force.

  The negative pressure supply for the vacuum brake booster is generally performed by a drive engine (internal combustion engine). If the maximum assist force obtained is too small due to a weak negative pressure supply (which often occurs with new engine technologies such as gasoline direct injection systems or diesel engines), additional braking force assist devices are required. A method for generating additional braking force or additional braking pressure is the use of an “active” hydraulic braking force assist device. This is achieved, for example, by a hydraulic pump. In this case, the hydraulic pressure generated in the hydraulic master brake cylinder is additionally increased by the hydraulic pump by the braking force applied by the driver via the brake pedal and increased by the vacuum brake booster. This pump is driven by an electric motor controlled by an electronic brake control unit.

  In such a system, it is necessary to know the maximum boost characteristic curve and the maximum boost point of the vacuum brake booster. This is because this maximum boost point determines the transition point between braking force assistance by negative pressure and braking force assistance by a hydraulic pump. The maximum boost characteristic curve and the maximum boost point or maximum boost pressure depend on various parameters such as the diaphragm area, negative pressure level and master brake cylinder area of the vacuum brake booster. There is a problem in fixing a sufficiently accurate maximum boost characteristic curve and an accurate maximum boost point or maximum boost pressure, for example based on the tolerances of the relevant components.

  It is known to incorporate a pressure sensor into a vacuum brake booster to identify and evaluate the pressure difference between the negative pressure chamber, i.e. the vacuum chamber and the working chamber.

  Patent Document 1 discloses a method for operating a vacuum brake booster and a vehicle brake device. In this case, the confirmed pressure difference is evaluated for controlling the control valve of the vacuum brake booster.

Patent Document 2 discloses a vacuum brake booster equipped with a control device. The control device includes two pressure sensors having two air guide passages. The air guide passage extends to the negative pressure chamber and the working chamber of the vacuum brake booster. The control device serves to control the vacuum brake booster.
German Patent No. 4436297 German Patent No. 19729158

  An object of the present invention is to provide a method and apparatus in which the characteristic curve and maximum boost point of a vacuum brake booster can be determined reliably and accurately.

  This problem is solved by the features of the independent claims.

  Particularly advantageous embodiments of the invention are described in the dependent claims.

  An object of the present invention is a method for determining or correcting a maximum boost characteristic curve of a vacuum brake booster of a vehicle brake device, the pressure in the working chamber of the vacuum brake booster, or the working chamber and the negative pressure chamber. And the maximum boost characteristic curve is determined based on the measured pressure or pressure difference of the vacuum brake booster, or set or stored maximum boost characteristic In a method in which the curve is changed or corrected according to the measured pressure or pressure difference, when the speed of operation of the brake operating device is less than 40-60 bar / sec, preferably less than about 50 bar / sec. The maximum boost characteristic curve is determined or the stored maximum boost characteristic curve is changed or corrected in response to the measured pressure or pressure difference. It is solved by determining or correcting the maximum boost characteristic curve of the vacuum brake booster of a vehicle brake system according to symptoms.

  By measuring the pressure in the working chamber of the vacuum brake booster or the pressure difference between the working chamber and the negative pressure chamber, the maximum boost characteristic curve of the vacuum brake booster can be determined or set relatively accurately. The maximum boost characteristic curve or the actual stored maximum boost characteristic curve can be adapted or changed to the determined value. Subsequently, during braking of the vehicle, it can be ascertained when the maximum boost point has been achieved and when brake control should be performed.

  The pressure difference between the working chamber and the vacuum chamber of the vacuum brake booster determines the actually adjusted pneumatic braking force assist. The pressure difference can be determined from the measured pressure or negative pressure in the working chamber and the vacuum chamber. Therefore, the pressure in the working chamber and the negative pressure chamber of the vacuum brake booster is preferably measured.

  In the present invention, the hydraulic pressure in the vehicle brake device, particularly the master brake cylinder, is measured, and the maximum boost characteristic curve is determined based on the measured pressure or pressure difference of the vacuum brake booster and the measured hydraulic pressure, Alternatively, the set or stored maximum boost characteristic curve is changed according to the measured pressure or pressure difference of the vacuum brake booster and the measured hydraulic pressure.

  The measured pressure or pressure difference of the vacuum brake booster is assigned the determined hydraulic pressure, in particular the pressure in the master brake cylinder. This assignment is consistent with the relationship between the pressure in the vacuum chamber and the maximum boost pressure. From this pair of values, the maximum boost characteristic curve can be determined directly by interpolation or extrapolation. Preferably, the characteristic curve is determined by a plurality of pairs of values or “reference points”.

  The hydraulic pressure is preferably measured by a pressure sensor already provided in the vehicle. This pressure sensor is provided, for example, in a brake system equipped with a driving dynamics control (ESP).

  In the present invention, an initial maximum boost characteristic curve is set, and the set initial maximum boost characteristic curve is changed or changed depending on the measured pressure or pressure difference of the vacuum brake booster and the measured hydraulic pressure. It is corrected.

  The maximum boost pressure is already determined and memorized before the first braking operation performed by the driver by measuring the pressure in the vacuum chamber and defining the corresponding maximum boost pressure based on the "basic characteristic curve" be able to.

  In the “basic characteristic curve”, all tolerances of the brake booster, the master brake cylinder and the relevant parts of the sensor are not yet taken into account. In the present invention, this tolerance is “learned” while the vehicle is running, in particular during braking, and is adapted or corrected according to the determined deviation of the set or currently stored maximum boost characteristic curve.

  Therefore, in order to minimize the deviation between the “true” characteristic curve, that is, the characteristic curve that actually exists and the characteristic curve that has been set, the maximum boost characteristic curve that has been set is at least once to the tolerance caused by the system. Be adapted. The initial braking of the vehicle is advantageously carried out by the vehicle manufacturer. In this case, the first correction of the basic characteristic curve can be performed. This already optimizes the control and pedal feel for the end customer of the vehicle. Other subsequent adaptations are made after the initial correction, generally with little or no feeling.

  Furthermore, even after the first adaptation, this maximum boost characteristic curve that is adapted or changed can be stored and possibly corrected according to other deviations determined. This makes the stored current characteristic curve increasingly closer to the “true” maximum boost characteristic curve. In addition, changes in the system over time, such as wear conditions, are taken into account. The current maximum boost characteristic curve is preferably stored in a memory such as an EPROM that is not adversely affected by the ignition of the drive engine.

  The determination preferably measures and stores the hydraulic pressure at the same time by monitoring whether a pressure differential or pressure corresponding to the selected reference point occurs at each braking or during a predetermined number of brakings. This is implemented by evaluating the value of the pair at the set “reference point”. Selection and classification of the reference points can be performed in certain steps or depending on the operation at that time. The associated slopes of the hydraulic pressure are preferably stored together at each reference point. This arises in particular from the speed of operation of the brake pedal by the driver and serves as a measure of measurement quality. In this case, subsequent measurements at the reference point are only taken into account if the pressure gradient that occurs is less than the last stored pressure gradient.

In the present invention, the maximum boost characteristic curve is determined or stored when the speed of operation of the brake operating device, in particular the brake pedal, is less than 40-60 bar / sec, preferably less than about 50 bar / sec. maximum boost characteristic curves is changed or corrected according to the measured pressure or pressure differential. In general, the speed of the brake operation is in such a range that the hydraulic pressure gradient is located below this limit value. If the slope is below about 40 bar / second, different time or braking measurements are considered the same. Braking with such a gradient is considered quasi-static.

  In the present invention, the maximum boost characteristic curve is determined or corrected by extrapolating the measured values. This is because the maximum boost characteristic curve extends similarly over the pressure applied by the driver and can be extrapolated appropriately. Thus, for example, a measurement that does not cover the full range of the characteristic curve is considered because there is not enough vacuum or the brakes are not operated, and the difference between the last valid measured value and the stored or set characteristic curve is still Add to insufficient measurements. This brings the reference point, which is rarely achieved or measured only at high pressure gradients, to a true characteristic curve.

  In this case, the “final” adaptation or correction of the maximum boost characteristic curve is only performed when a predetermined relatively high hydraulic pressure has already been achieved, which corresponds to the proximity to the maximum boost point. According to this method, it is possible to adapt at least temporarily before the characteristic curve reaches a high hydraulic pressure. Alternatively or additionally, the achievement of a relatively high pressure in the working chamber that matches the ambient atmospheric pressure can be evaluated as an indication of proximity to the maximum boost point.

In the present invention, the following condition a) hydraulic pressure gradient is less than 50 bar / second,
b) The hydraulic pressure gradient is greater than 0,
c) the current gradient of hydraulic pressure is smaller than the gradient at the time of determining the effective maximum boost characteristic curve;
d) active brake intervention of electronic brake control such as anti-lock brake system (ABS), driving dynamics control (ESP), traction slip control (TCS), brake assist (HBA) or auto cruise control (ACC) Not implemented,
e) negative pressure is sufficient, ie the negative pressure in the negative pressure chamber is less than 50 mbar, preferably less than 100 mbar;
f) The reference point is sufficiently accurate, ie the deviation between the measured pressure difference between the working chamber and the negative pressure chamber and the set reference point is less than ± 50 mbar, preferably ± Less than 40 mbar, and g) one if the change to a pre-set or set measurement is sufficiently large, greater than 1.2 bar, preferably greater than 1.0 bar. Measurements are taken into account.

  In the present invention, the determination and / or adaptation of the maximum boost characteristic curve together with confirmation of the demand for additional brake assistance is active and only when the driver confirms the demand for additional brake assistance. A hydraulic brake assist device is activated in situations where it is necessary.

  In the present invention, the determination and / or adaptation of the maximum boost characteristic curve includes together confirming that the maximum boost point has been reached or at least close to the maximum boost point, and that the maximum boost point has been reached Or, at least if it is confirmed that it is close to the maximum boost point, the active hydraulic brake assist device is activated.

  In the present invention, the boost of the vacuum brake booster and / or hydraulic brake assist device can be adjusted according to other functions of the brake control system such as brake assist (BA) or driving dynamics control (ESP). is there.

  In the present invention, during multiple braking of the vehicle, the measured pressure or pressure difference is evaluated, and from this evaluation, the maximum boost characteristic curve is determined or stored according to the measured pressure or pressure difference. The maximum boost characteristic curve is adapted or corrected.

  The present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a brake operating device provided with a correction device according to the present invention. The brake operating device includes a vacuum brake booster 1. This vacuum brake booster is divided into at least one working chamber 2 and a negative pressure chamber (vacuum chamber) 3. The vacuum brake booster can be operated by the brake pedal 5 via the operation rod 4. Thereby, the tandem master brake cylinder 6 connected to the vacuum brake booster 1 is operated. The tandem master brake cylinder 6 includes hydraulic connection pipes 7 and 8 connected to vehicle wheel brakes. The negative pressure chamber 3 is connected via a connecting pipe 9 to a negative pressure source or a vacuum source (not shown) that operates continuously.

  Sensors 10 and 11 are attached to the correction device. The (vacuum) pressure in the working chamber 2 is measured by the first sensor 10, and the (vacuum) pressure in the negative pressure chamber 3 is measured by the second sensor 11. The hydraulic pressure of the tandem master brake cylinder 6 is measured by a hydraulic pressure sensor 12 for at least one brake circuit.

  When the pedal 5 is operated and the operating rod 4 is slid, the valve in the vacuum brake booster 1 is operated. First, the connection between the negative pressure chamber 3 and the working chamber 2 is cut off. When the operating rod slides further, the connection to the outside air is opened by the valve. The negative pressure starts a boost of the force applied by the brake pedal 5. Brake pressure is applied to the wheel brake of the vehicle by the rising hydraulic pressure in the master brake cylinder 6.

  The pressure difference between the working chamber 2 and the negative pressure chamber 3 increases or decreases according to the change in pedal force. This is measured by sensors 10 and 11. The resulting hydraulic pressure is measured by the sensor 12. The measured value is evaluated by the electronic control and adjustment unit 13. The relationship between the pressure difference in the vacuum brake booster 1 and the hydraulic pressure is stored. A characteristic curve for correcting the maximum boost characteristic curve of the vacuum brake booster 1 is determined in consideration of various maximum boost situations of the vacuum brake booster 1.

  When the pedal is further depressed, air flows from the atmosphere through the valve into the working chamber 2. The pressure difference generated between the negative pressure chamber 3 and the working chamber 2 tries to slide the partition between the working chamber 2 and the negative pressure chamber 3 until the pressure in the working chamber 2 matches the atmospheric pressure. On the other hand, the pressure in the negative pressure chamber 3 matches the negative pressure generated based on the connected vacuum source. These situations correspond to the full braking position of the vacuum brake booster. The maximum boost of the vacuum brake booster is supplied and the maximum boost point is reached. Further increase in force is possible only with greater pedal force applied by the driver.

  The respective negative pressure in the vacuum brake booster and the corresponding maximum boost hydraulic pressure are determined by the control and adjustment unit 13 each time. If the comparison with the correction characteristic curve (the relationship between the pressure difference in the vacuum brake booster chamber pressure and the maximum boost hydraulic pressure) shows that the current hydraulic pressure exceeds the maximum auxiliary hydraulic pressure, the control The cum adjustment unit 13 generates a control signal for the active hydraulic braking force assisting device in the direction of increasing the additional hydraulic pressure by controlling the hydraulic pump, for example.

  In FIG. 1, the sensors 10, 11 are shown as two separate units for ease of viewing. However, it is advantageous to have two sensor elements in one common casing. Such a “double pressure sensor” can be handled and operated like a single sensor during the sensor chain process from the sensor manufacturer to the vacuum brake booster manufacturer to the vehicle manufacturer. This gives rise to cost advantages and assembly advantages. In a very advantageous embodiment, at least a part of the sensor casing is integrated into the negative pressure casing of the vacuum brake booster 1. This reduces the required space in the engine room.

  FIG. 2 shows a plot of the determined correction characteristic curve, the maximum boost characteristic curve (brake control characteristic curve), and the brake pressure P against the pressure difference dV between the negative pressure chamber and the working chamber. This correction characteristic curve is determined based on the measured pressure difference dV in the brake booster 1 and the associated hydraulic pressure P (brake pressure in the tandem master brake cylinder). The pressure difference measured by the sensors 10, 11 determines the braking force assist that is adjusted at that time. The pressure differences dV1 to dV4 are assigned to the corresponding hydraulic pressures, that is, the hydraulic pressures P1 to P4 measured at that time. Then, a correction characteristic curve KL (solid line) is obtained in which the average value is obtained from the reference point (nodal point) (dV1 / P1; dV2 / P2; dV3 / P3; dV4 / P4). Further increases in the brake pressure P are possible only by increasing the pedal force applied by the driver after this point.

  With the determined and stored correction characteristic curve shown in FIG. 2, a maximum boost point A with an associated maximum boost pressure PA can be assigned to the pressure in the negative pressure chamber V. FIG. 3 shows the brake control curve AL determined from the correction characteristic curve KL shown in FIG. 2 in a similar manner. The brake control curve AL can be corrected or adapted by the correction characteristic curve KL.

  As can be seen from the correction characteristic curve KL, for example, the pressure difference dVx coincides with the maximum boost hydraulic pressure Px. As in the case where the measured negative pressure Vx matches the pressure difference (Vx = dVx), the maximum boost hydraulic pressure Px is generated (FIG. 3). With the “corrected” maximum boost characteristic curve AL, the maximum boost point A can be determined reliably and accurately.

  If the maximum boost point is exceeded and the driver requests further or stronger vehicle deceleration, the brake pressure P can be increased by hydraulic boosting by the pump. The hydraulic pressure boost is adjusted to the required maximum brake pressure according to the boost factor or the slope of the maximum boost characteristic curve AL. Since the determined characteristic curve AL is very close to or coincides with the “true” characteristic curve, the driver does not feel a change in the characteristic of the brake control. As a result, the pedal feel is the same. Therefore, the operational comfort of the driver is enhanced by the present invention.

It is the schematic of the brake operation apparatus provided with the correction apparatus. It is a figure which shows roughly the determined correction characteristic curve. It is a figure which shows roughly the maximum boost characteristic curve determined from the correction characteristic curve.

Claims (7)

A method of determining or correcting a maximum boost curve of the vacuum brake booster of a vehicle brake system, the vacuum brake booster, the pressure in the working chamber, or the pressure difference between the working chamber and the negative pressure chamber Is measured and a maximum boost characteristic curve is determined based on the measured pressure or pressure difference of the vacuum brake booster, or a set or stored maximum boost characteristic curve is measured. In a method that is changed or corrected according to the pressure or pressure difference,
The maximum boost characteristic curve is determined when the speed of operation of the brake operating device is less than 40-60 bar / sec , or the stored maximum boost characteristic curve is dependent on the measured pressure or pressure difference A method characterized by being changed or corrected.   The hydraulic pressure in the vehicle brake device is measured, and the maximum boost characteristic curve is determined based on the measured pressure or pressure difference of the vacuum brake booster and the measured hydraulic pressure, or The set or stored maximum boost characteristic curve is changed or corrected according to the measured pressure or pressure difference of the vacuum brake booster and the measured hydraulic pressure. The method according to 1.   3. The method according to claim 1, wherein the maximum boost characteristic curve is determined or corrected by extrapolating the measured values. The following conditions a) the hydraulic pressure gradient is less than 50 bar / second,
b) the gradient of the hydraulic pressure is greater than 0;
c) The current gradient of the hydraulic pressure is smaller than the gradient at the time of determining the effective maximum boost characteristic curve; d) Anti-lock brake system (ABS), driving dynamics control (ESP), traction slip control (TCS), brake Active brake intervention of electronic brake control such as assist (HBA) or auto cruise control (ACC) is not implemented,
e) the negative pressure in the negative pressure chamber is less than 100 mbar;
f) the difference between the measured pressure difference between the working chamber and the negative pressure chamber and the set reference point is less than ± 50 mbar, and g) the change with respect to the pre-set or set measured value but if you meet the greater condition than 1.0 bar, the method according to any one of claims 1 to 3, one measurement is characterized in that it is taken into account. Active or only when the determination or correction of the maximum boost characteristic curve includes confirmation of a request for additional brake assistance, and in situations where the request for additional brake assistance for the driver has been confirmed. The method according to claim 1, wherein a hydraulic brake assist device is activated. Determining or correcting the maximum boost characteristic curve together with confirming that the maximum boost point has been reached or at least close to the maximum boost point, and that the maximum boost point has been reached or at least the maximum boost point 6. The method of claim 5, wherein the active hydraulic brake assist device is activated only when it is determined that the vehicle is in proximity. The boost of the vacuum brake booster and the hydraulic brake assist device can be adjusted according to other functions of the brake control system such as brake assist (BA) or driving dynamics control (ESP). The method according to claim 5 or 6.

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