Control method for an electronically slip-regulated brake assist device, electronically slip-regulated brake assist device, and electronic controller

Abstract

The invention relates to a method for controlling an electronically slip-regulated power brake device, to an electronically slip-regulated power brake device, and to an electronic controller for an electronically slip-regulated power brake device. The power brake device is equipped with a friction brake device, with a generator brake device, and with an electronic controller for controlling the brake devices in a needs-adapted manner. The friction brake device comprises, inter alia, an electronically controllable brake pressure generator with a ram, which can be operated by a controllable drive unit, and which delivers pressure medium to the wheel brakes of the power brake device. It is proposed that, after the power brake device has been switched from generating a generator brake torque to generating a friction brake torque, the operation of the drive unit of the ram is controlled by the electronic controller in such a way that the speed of the ram being operated changes strictly monotonically. Pressure shocks and the noise associated therewith at the beginning and end of the operation of the ram are reduced.

Description

Technical Field

[0001] This invention relates to a method for controlling an electronically adjustable power-assisted braking device for a motor vehicle, and further relates to an electronically adjustable power-assisted braking device and an electronic controller.

[0002] Electronically adjustable power-assisted braking systems in motor vehicles are prior art. These systems can perform braking actions independently of the driver's braking intentions and prevent wheel lock-up during operation, at startup, or during the braking process. Therefore, such power-assisted braking systems significantly help avoid accident-prone driving conditions and ultimately contribute to improved traffic safety. Background Technology

[0003] For example, a power-assisted braking device that can be electronically adjusted by sliding is known from DE 10 2013 205 653 A1.

[0004] This material Figure 1 This known power-assisted braking device is illustrated schematically and in a very simplified manner in an improved embodiment. According to this improved embodiment, the power-assisted braking device 10, in addition to the conventional friction braking device 12, also includes a generator braking device 14. The two braking devices can provide, individually or jointly, the necessary total braking torque for braking a motor vehicle equipped with the power-assisted braking device 10, and thus contribute to the particularly energy-efficient operation of such a motor vehicle. The braking pressure and braking torque are controlled in a demand-responsive manner by an electronic controller 16.

[0005] according to Figure 1 The power-assisted braking system is further equipped with a device 18 for detecting a braking demand. This is a master cylinder 22 that can be operated by the driver via the brake pedal 20. The braking demand is obtained by measuring the displacement of the brake pedal 20 using a displacement sensor 24, and its suitability is checked using the braking pressure present in the master cylinder 22. A pressure sensor 26 is present to measure the braking pressure.

[0006] The friction braking device 12 of the power-assisted braking device 10 is equipped with a brake pressure generator 30, which includes a squeezer 32, for example, implemented in the form of a piston. The piston is axially movably housed inside a cylinder 34 and, together with the cylinder 34, defines a pressure medium chamber 36. To deliver the pressure medium to the wheel brakes 38 of the power-assisted braking device 10, the piston is driven linearly by an electronically controllable drive unit 40, thereby gradually reducing the volume of the pressure medium chamber 36. If the pressure medium is largely discharged or depleted from the pressure medium chamber 36, the piston is driven in the opposite direction of motion to refill the pressure medium chamber 36 with new pressure medium.

[0007] The auxiliary generator braking device 14 of the power-assisted braking device 10 is preferably constructed from the electric drive motor of the motor vehicle. This electric drive motor can operate as a generator during braking and, for example, supply electrical energy to the vehicle's energy storage system. The energy used to drive the generator is obtained here from the kinetic energy of the rotating vehicle.

[0008] However, the braking torque generated here depends on the driving speed of the generator and decreases as the driving speed decreases. If the vehicle speed, and therefore the driving speed of the generator, is too low, then there is not enough generator braking torque available to bring the vehicle to a stop. Consequently, the vehicle ultimately brakes to a stop only by means of the friction braking device.

[0009] The control of the power-assisted braking device 10 by the electronic controller 16 in the transition from generator braking operation to friction braking operation has a significant impact on the resulting driving comfort, or on the noise and vibration that can be perceived by the driver or passengers.

[0010] Advantages of the present invention The present invention has the advantage that when the braking system switches from generator braking operation to friction braking operation, the vehicle passengers perceive as little reaction force as possible or none at all. According to the invention, the latter is achieved by the electronic controller 16 of the power-assisted braking device 10 through the optimized electrical control of the drive unit 40 of the brake pressure generator 30.

[0011] It is proposed that after the power-assisted braking device 10 switches from generator braking operation to friction braking operation, the control of the drive unit 40 of the extruder 32 is performed by the electronic controller 16 such that the speed of the extruder 32, or the piston, changes strictly monotonically during operation.

[0012] The proposed method can be used in all operating conditions where there is no longer sufficient generator braking torque available and the driver's braking desire needs to be implemented through the friction braking device 12.

[0013] In the known power-assisted braking system 10, the brake pressure generator 30's actuator 32, or piston, accelerates from a standstill to its maximum speed and then continues to operate at a constant speed. While this operation results in a linear build-up of brake pressure, it also causes high acceleration at the start and end of the actuator 32's operation. This places a mechanical load on the actuator 32 and its actuator actuator, and can cause noise or vibration that may be bothersome to passengers.

[0014] Through optimizations to the control, a smoother start and a smoother finish to the operation are achieved. This reduces the acceleration caused by the brake lever, minimizes changes in braking pressure, and consequently improves ride comfort for passengers by avoiding perceptible noise and vibration.

[0015] Further advantages or advantageous improvements of the invention are derived from the dependent claims and from the following description.

[0016] In an advantageous improvement of the invention, it is proposed that the speed of the extruder 32 increases strictly monotonically from the start of the operation of the extruder until the maximum speed; and the speed decreases strictly monotonically from the maximum speed until the end of the operation.

[0017] In other words, the control of the drive unit 40 is performed by the electronic controller 16 such that the speed of the extruder 32, plotted during the time between the start and end of the extruder's operation, has an arc-shaped or parabolic curve of change. Therefore, the acceleration or deceleration of the extruder 32 is achieved stably and without interruption, and the speed of the extruder 32 changes accordingly continuously and non-jumping.

[0018] This invention avoids the situation where, even under high pressure build-up dynamics, braking pressure build-up occurs in a manner that can be disturbing. Furthermore, it avoids pressure oscillations that, despite a constant braking desire, cause fluctuations in vehicle deceleration. Attached Figure Description

[0019] The invention is illustrated with the aid of the accompanying drawings, which will be explained in detail below. The drawings comprise a total of 5 images.

[0020] Figure 1 The diagram illustrates, in a very simplified manner, the version of the power-assisted braking device as explained at the beginning and improved by the integration of an additional generator braking device.

[0021] Figures 2 to 5 The graphs illustrate the travel, speed, acceleration, and pulses originating from the movement of the brake pressure generator of the friction braking device during the braking process and after the transition from generator braking to friction braking operation. The graphs are recorded synchronously with each other. Each graph contains two characteristic curves: one illustrating the variation when the piston drive is operated according to the prior art; and the other, directly compared, illustrating the variation of various quantities in the control method according to the invention. Detailed Implementation

[0022] exist Figure 2 The graph shown illustrates the change in distance *s* traveled by the piston or squeezer 32 of the brake pressure generator 30 during the braking process time *t* after the power-assisted braking device 10 has transitioned from generator braking operation to friction braking operation. Two characteristic curves A and B are shown, wherein characteristic curve A rises continuously with a constant slope from a starting point *t1* (where the distance *s* traveled is zero) to an endpoint *t2* (where the maximum distance *s(max)* traveled) is reached. This characteristic curve corresponds to a control method known from the prior art for the drive unit 40 of the brake pressure generator 30. In this control method, the squeezer 32 moves at a constant speed between the endpoints (see [link to previous section]). Figure 3 ).

[0023] Conversely, characteristic curve B shows an S-shaped curve of change between endpoints t1 and t2. Characteristic curve B illustrates the movement of the extruder 32 when the brake pressure generator 30 is operated according to the method according to the invention. The extruder 32 also begins its journey at the initial time point t1; however, the journey initially increases very slowly and lags significantly behind the first half of the S-shaped curve compared to the journey described by characteristic curve A. The difference in journey distance increases to its maximum at time point t3 and then gradually decreases between t3 and t4. At time point t4, the piston travels the same distance regardless of the operating method, causing the two characteristic curves A and B to intersect. Thereafter, the extruder 32 driven according to the method according to the invention travels a greater distance than according to known methods. This increased distance rises to time point t5 and then gradually decreases. The movement ends at time point t2, or the extruder 32 has traveled a distance s(max).

[0024] Figure 3 Similarly, the speed v variation curve of the extruder 32 is shown using two characteristic curves C and D, which are based on... Figure 2 It moves between the two endpoints.

[0025] In the control method according to the prior art (characteristic curve C), the speed v rises almost vertically or without delay to its maximum speed v1 at time point t1, and then remains constant until shortly before reaching time point t2. At time point t2, the speed v of the extruder 32 also drops to zero almost without delay. This results in an almost rectangular speed change curve.

[0026] In contrast, the speed variation curve (characteristic curve D) of the extruder 32 under the operation according to the invention is arc-shaped and increases strictly monotonically, reaching a maximum speed v2 at time point t4, and then decreases strictly monotonically until zero. Up to time point t7 and from time point t8 onwards, the speed v is lower than in the prior art; while it is higher between these time points.

[0027] Figure 4 Characteristic curves E and F are shown, which describe the variation of acceleration a at the extruder 32.

[0028] In the control method according to the prior art (characteristic curve E), a relatively sharp acceleration peak, pointing positive in the graph, appears at the beginning, and a sharp deceleration peak, pointing negative, appears near the end of the movement of the extruder 32. Between these peaks, the acceleration is zero because the extruder 32 maintains a constant speed (see...). Figure 3 )sports.

[0029] In contrast, in the control method according to the present invention, the acceleration has a very flat wave-like variation curve (characteristic curve F). The peak, i.e., the maximum acceleration value, appears shortly after the start of the movement of the extruder 32 (i.e., in the range near time point t1). The trough, i.e., the range of the maximum deceleration of the extruder 32, appears at the end of the movement of the extruder 32 (in the region near time point t2). From the amplitude and shape of the peaks and troughs, it can be inferred that the acceleration and deceleration are significantly smaller than those (characteristic curve E) according to known control methods. Furthermore, the wavy variation curve shows that, unlike the prior art, the acceleration ratio in the present invention changes steadily or uniformly and does not exhibit "sprungverhalten," i.e., no obvious peaks are shown.

[0030] Figure 5 Characteristic curves G and H illustrate the force pulses emitted by the operated extruder 32 to the hydraulic circuit of the power-assisted braking system 10. In the prior art, pulses with relatively high amplitude, directed in two directions (i.e., towards the acceleration direction of the extruder 32 and towards the deceleration direction of the extruder 32), occur at the beginning (near time point t1) and the end (near time point t2) of the movement of the extruder 32, respectively. The peak value in the current signal used for the drive unit 40 is related to these pulses, and therefore, the peak value in the driving force of the extruder 32 allocated to the brake pressure generator 30 is also related to these pulses. The latter is the cause of noise and vibration generated in the prior art.

[0031] In the control method according to the invention (characteristic curve H), only force pulses appear along the acceleration direction of the extruder 32. In direct comparison, these force pulses are significantly smaller in amplitude than those in the prior art, and further decrease (around time point t1) or increase (around time point t2) over longer time intervals. The characteristic curve H is generally characterized by a smooth, continuous curve of change. Correspondingly, the driving force of the extruder 32, distributed by the drive unit 40 to the brake pressure generator 30, responds, and as a result, the drive of the brake pressure generator 30 causes less noise and vibration.

[0032] When the vehicle's power-assisted braking device 10 switches from generator operation or friction braking operation (i.e., when there is a braking desire but there is no longer a sufficiently high generator braking torque to decelerate the vehicle), the recommended control method can be used as initially shown.

[0033] It should be further noted that the present invention is described by way of example only by means of a brake pressure generator 30, which is equipped with a piston- / cylinder unit for delivering the pressure medium. Alternatively, it is conceivable to use, for example, a squeeze pump (e.g., a gear pump) that continuously delivers the pressure medium instead of such a brake pressure generator.

[0034] Other changes or additions to the embodiments described in the specification are conceivable without departing from the basic concept explained in this invention.

Claims

1. A method for controlling a power-assisted braking device (10) that can electronically adjust the slip of a motor vehicle, wherein The power-assisted braking device (10) is equipped with Friction braking device (12) that generates friction braking torque. The generator braking device (14) that generates generator braking torque, and Electronic controller (16) for controlling the braking devices (12, 14) in a demand-responsive manner. The friction braking device (12) includes a brake pressure generator (30), which can deliver a pressure medium to the wheel brakes (38) of the power-assisted braking device (10). In this embodiment, for the purpose of conveying the pressure medium, the braking pressure generator (30) has a squeezer (32) that can be operated by a drive unit (40) that can be electronically controlled, characterized in that, After the power-assisted braking device (10) switches from generating a generator braking torque to generating a friction braking torque, the operation of the drive unit (40) of the extruder (32) is performed by the electronic controller (16) in such a way that the speed (v) of the operated extruder (32) changes strictly monotonically. The drive unit (40) is operated by the electronic controller (16) in such a way that: This causes the speed (v) of the extruder (32) to increase strictly monotonically from the start of operation of the extruder (32) until the maximum speed (v2) of the extruder (32); and This causes the speed (v) of the extruder (32) to decrease strictly monotonically from the maximum speed (v2) until the end of the operation. The force pulses emitted by the operated extruder (32) to the hydraulic circuit of the power-assisted braking device (10) occur only along the acceleration direction of the extruder (32).

2. A power-assisted braking device that can be electronically adjusted (10). Equipped with Friction braking device (12) that generates friction braking torque. The generator braking device (14) that generates generator braking torque, and Electronic controller (16) for controlling the braking devices (12, 14) in a demand-responsive manner. wherein The friction braking device (12) includes a brake pressure generator (30), which can deliver a pressure medium to the wheel brakes (38) of the power-assisted braking device (10), and In this embodiment, for the purpose of conveying the pressure medium, the braking pressure generator (30) has a squeezer (32) that can be operated by a drive unit (40) that can be electronically controlled, characterized in that, The electronic controller (16) is configured to perform the method according to the features of claim 1.

3. The power-assisted braking device (10) with electronic sliding adjustment according to claim 2. Its features are, The extruder is a piston movably housed in a cylinder (34), which can be operated by the drive unit (40) to perform translational motion for the delivery of the pressure medium.

4. The power-assisted braking device (10) with electronic sliding adjustment according to claim 2. Its features are, The power-assisted braking device (10) is used in motor vehicles.

5. An electronic controller (16) for controlling the power-assisted braking device (10) that can electronically adjust the slip of a motor vehicle. wherein The power-assisted braking device (10) is equipped with a friction braking device (12) that generates a friction braking torque and a generator braking device (14) that generates a generator braking torque. The friction braking device (12) includes a brake pressure generator (30), which can deliver a pressure medium to the wheel brakes (38) of the power-assisted braking device (10). In this embodiment, for the purpose of conveying the pressure medium, the braking pressure generator (30) has a squeezer (32) that can be operated by a drive unit (40) that can be electronically controlled, characterized in that, The electronic controller (16) is configured to perform the method according to the features of claim 1.

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