Method for determining a stiffness of a hydraulic brake system, method for operating a hydraulic brake system of a two-wheeled vehicle, hydraulic brake system of a two-wheeled vehicle and two wheeled vehicle

Abstract

The present invention relates to a method for determining the rigidity (33) of a hydraulic braking system (10), particularly for a hydraulic braking system of an electric bicycle (100), wherein the hydraulic braking system (10) has an anti-lock unit (1) having a piston (4) actuated in a controllable manner for active pressure modulation of a braking pressure, and wherein the method comprises the following steps performed during actuation of the piston (4): determining a volume change (32) of a braking fluid by actuation of the piston (4); determining a pressure change (31) of the braking pressure; and determining the rigidity (33) of the hydraulic braking system (10) as a ratio of the pressure change (31) to the volume change (32), wherein the volume change (32) is determined based on a position change of the piston (4).

Description

[Technical Field]

[0001] None. [Previous Technology]

[0002] This invention relates to a method for determining the rigidity of a hydraulic braking system, a method for operating a hydraulic braking system of a two-wheeled vehicle, a hydraulic braking system for a two-wheeled vehicle, and a two-wheeled vehicle.

[0003] Hydraulic braking systems are known to have an anti-lock braking unit (ABS) that prevents or reduces wheel lock-up of a vehicle by pressure modulation of the hydraulic braking pressure within the system. For example, this ABS has a reservoir chamber into which brake fluid can flow during ABS operation to modulate the pressure. To achieve optimal performance during ABS operation, pressure modulation suitable for the fundamental braking parameters of the hydraulic braking system is required. A particularly relevant fundamental braking parameter is the stiffness of the hydraulic braking system. However, the stiffness of different braking systems can vary significantly. Furthermore, stiffness can change during braking system operation, for example, due to changing environmental conditions (such as temperature). [Summary of the Invention]

[0004] In contrast, the method according to the invention having the features of claim 1 is characterized in that the stiffness of the hydraulic braking system can be determined with particular precision, and particularly at any time during the operation of the hydraulic braking system. Therefore, for example, the required performance of the hydraulic system in braking action can be reliably monitored and / or adjusted. This is achieved by a method for determining the stiffness of a hydraulic braking system (preferably for a hydraulic braking system of an electric bicycle), wherein the hydraulic braking system has an anti-lock unit having a piston that can be actuated in a controllable manner. Active pressure modulation of the braking pressure in the hydraulic braking system can be achieved by the controlled actuation of the piston. The method includes the following steps, performed during piston actuation: - determining the volume change of the braking fluid caused by piston actuation, - determining the pressure change of the braking pressure, and - determining the stiffness of the hydraulic braking system as the ratio of the pressure change to the volume change.

[0005] This is based on the change in piston position to determine the volume change during piston actuation.

[0006] This method therefore allows for the simple determination of a parameter related to braking power. Specifically, the determined stiffness can be used in a variety of ways. For example, during the operation of the anti-lock braking unit in anti-lock operation, the controlled actuation of the piston can be purposefully adjusted to achieve optimal pressure modulation, for example, by adjusting the pressure gradient and / or maximum and / or minimum pressure. For example, the determined stiffness can also be used to optimize the structural design of the hydraulic braking system, preferably to achieve actuation behavior suitable for the driver's expectations, such as the desired bite.

[0007] Because volume change and braking pressure are determined, parameters specifically related to the operation of the hydraulic braking system can be determined simply and directly without complex calculations. Specifically, rigidity can be directly determined in the assembled and operating state of the hydraulic braking system. In a hydraulic braking system, rigidity can be affected by a large number of factors, in which case precise understanding of these factors is not required. For example, such influencing factors include the elasticity or resilience of components such as brake lines, brake cylinders, brake calipers, brake pads, and anti-lock braking units, and especially the properties of the brake fluid, such as compressibility. Environmental effects such as temperature changes can also affect rigidity.

[0008] The appendix contains a preferred further development of the invention.

[0009] A hydraulic braking system preferably includes a brake cylinder, a brake caliper, a brake wiring system, and a master valve. The brake wiring system connects the brake cylinder and the brake caliper. The master valve is integrated into the brake wiring system. This method is performed specifically only when the master valve interrupts the fluid connection between the brake cylinder and the brake caliper, i.e., when the master valve is closed. Specifically, rigidity is therefore determined only for a portion of the hydraulic braking system, i.e., the portion located between the master valve and the brake caliper, and the anti-lock unit is preferably integrated into this portion. This portion represents the part of the hydraulic braking system related to anti-lock operation, thereby allowing for particularly simple and reliable setup of optimal operation during anti-lock operation.

[0010] The change in piston position is preferably determined as longitudinal displacement of the piston within the chamber of the anti-lock unit and along its axis. Specifically, the fluid volume within the chamber can be changed in a controlled manner by the longitudinal displacement of the piston within the chamber, thereby achieving pressure modulation in the hydraulic braking system. The change in brake fluid volume is thus determined based on the longitudinal displacement of the piston along its axis and based on the piston surface. The piston surface is considered as the surface of the piston through which it can apply pressure to the brake fluid. The change in brake fluid volume achieved by the piston displacement can therefore be determined, particularly simply, by geometric relationships.

[0011] Longitudinal displacement is better determined by a magnetic sensor. This allows for the determination of volume changes in a particularly simple and low-cost manner.

[0012] The method preferably further includes the following steps: performing noise reduction by means of determined measurements of volume change and pressure change. Noise reduction is performed in particular by means of corresponding signals, on which measurements of volume change and pressure change are generated to obtain optimized data that is easier to process from inaccurate or fluctuating signals.

[0013] In particular, noise reduction is performed by means of a low-pass filter, thereby enabling particularly simple signal optimization.

[0014] More preferably, noise reduction is performed using the recursive least squares algorithm (RLS algorithm for short). This allows for the acquisition of particularly accurate data.

[0015] The parameters of the recursive least squares algorithm are preferably adjusted based on the determined pressure change. These parameters are particularly preferably adjusted so that the gradient change due to low pressure is weighted more heavily than the gradient change due to high pressure. This allows for more accurate results to be obtained in a simpler way, because, for example, the gradient change due to lower pressure has less noise compared to the gradient change due to high pressure.

[0016] The method preferably further includes the step of determining the instantaneous braking pressure in the hydraulic braking system. Herein, the method is performed only when the braking pressure is determined to be at least equal to a predetermined minimum braking pressure, preferably 50 bar. That is, stiffness is determined only when the hydraulic braking system is at least preloaded with a predetermined minimum braking pressure, such as during braking. This method can be particularly accurate in determining stiffness in situations involving braking with high braking pressure. The method is particularly preferably performed only when the driver pulls the brake lever of the hydraulic braking system.

[0017] This method is particularly preferred for calibrating hydraulic braking systems in two-wheeled vehicles, and preferably in electric bicycles. The method is therefore performed specifically only when the two-wheeled vehicle, and preferably the electric bicycle, is stationary. For example, the method can be performed such that the driver of the two-wheeled vehicle pulls the brake lever, and when the brake lever is pulled, the piston is actuated in a controlled manner to simultaneously determine both volume and pressure changes, and based on this, to determine rigidity. Therefore, a particularly simple and convenient calibration of the hydraulic braking system can be performed.

[0018] The present invention further provides a method for operating a hydraulic braking system, preferably for a hydraulic braking system of an electric bicycle. The method for operating the hydraulic braking system includes the following steps: - determining the rigidity of the hydraulic braking system by means of the described method for determining rigidity, and - during anti-lock operation of the anti-lock unit of the hydraulic braking system, actuating the piston of the hydraulic braking system, wherein the actuation of the piston is determined based on the determined rigidity.

[0019] The optimal braking action required by the hydraulic braking system can be achieved in a particularly precise and targeted manner.

[0020] Based on the determined rigidity, the amplitude and / or frequency of piston actuation, especially the amplitude and / or frequency of longitudinal displacement, are preferably adjusted during the active pressure modulation of the braking pressure. That is, during the anti-lock operation of the anti-lock unit, the controlled actuation of the piston is adjusted to obtain braking function optimally suited to the determined rigidity.

[0021] The present invention further provides a hydraulic braking system for two-wheeled vehicles, preferably bicycles, and particularly preferably electric bicycles, comprising an anti-lock unit, a brake cylinder, a brake caliper, a brake wiring, a master valve, and a control device. The anti-lock unit has: a chamber for containing brake fluid; a piston defining the fluid volume inside the chamber and capable of displacement along an axis; and an actuator adapted to controllably displace the piston along the axis. The brake wiring has: a first segment fluidly connected to the chamber and to the brake caliper; and a second segment connected to the brake cylinder. The master valve is integrated into the brake wiring and adapted to block or release the fluid connection between the brake caliper and the brake cylinder. The control device is adapted to perform the described method for determining the rigidity of the hydraulic braking system or for operating the hydraulic braking system. The hydraulic braking system thus has a particularly simple and low-cost construction that allows for accurate determination of basic braking parameters.

[0022] The hydraulic braking system preferably further includes a pressure sensor adapted to obtain the braking pressure at the brake caliper. The measurement value of the pressure sensor preferably serves as the basis for pressure changes in a method for determining the rigidity of the hydraulic braking system. This allows for particularly accurate determination of the relevant pressure changes at the brake caliper.

[0023] The present invention further provides a two-wheeled vehicle, particularly a bicycle, and preferably an electric bicycle, incorporating the described hydraulic braking system. Especially in the case of a bicycle, and preferably an electric bicycle, numerous adjustment possibilities are provided to individually adjust the braking behavior of the hydraulic braking system according to the rider's expectations. By determining the rigidity of the hydraulic braking system, reliable and optimal braking function can still be ensured in any configuration and driving situation, especially in anti-lock operation.

Implementation Method

[0025] FIG1 is a simplified schematic view of an electric bicycle 100 according to a preferred exemplary embodiment of the present invention. The electric bicycle 100 includes a drive unit 105, which is adapted to assist the rider's pedaling force by means of motor force. Electrical energy is supplied to the drive unit 105 by means of an energy storage device 106. The energy storage device 106 may be disposed, for example, inside the downtube 109 of the frame of the electric bicycle 100.

[0026] The electric bicycle 100 includes a hydraulic braking system 10, which actuates brakes 101 and 102 at the front wheel 107 or rear wheel 108 of the electric bicycle 100. For each brake 101 and 102, the hydraulic braking system 10 includes a brake lever 19, a brake cylinder 15, a brake caliper 13, a wiring 11 that hydraulically connects the brake cylinder 15 and the brake caliper 13, and an anti-lock unit 1 integrated in the wiring 11.

[0027] The anti-lock unit 1 can also be configured inside the downtube 109 of the electric bicycle 100, and is supplied with power by the power storage device 106.

[0028] The hydraulic braking system 10 with anti-lock unit 1 will be described in detail below with reference to FIG2. For simplicity, only a single brake 101, especially the brake of the front wheel 107, will be described here.

[0029] The brake caliper 13 is connected to the first segment 11a of the wiring 11. The brake cylinder 15 is connected to the second segment 11b of the wiring 11. The first segment 11a and the second segment 11b can be hydraulically separated from each other by the main valve 16. The main valve 16 is preferably a normally open valve.

[0030] The anti-lock unit 1 further includes a chamber 2 in which braking fluid can be contained. The chamber 2 is connected to the line 11 between the main valve 16 and the brake caliper 13.

[0031] Inside the chamber 2, the fluid volume is defined by the piston 4. The piston 4 can be displaced along the axis 50 by means of the actuator 5, so that the fluid volume inside the chamber 2 is variable.

[0032] The actuator 5 is in the form of an electric motor and can be actuated by the control device 61.

[0033] The anti-lock unit 1 further includes a return element 6 in the form of a helical spring, which is disposed on the side of the piston 4 opposite to the chamber 2 and applies a return force 60 to the piston 4. Thereby, the return force 60 is oriented completely opposite to the fluid inlet 70 leading to the chamber 2.

[0034] The anti-lock unit 1 further includes a pressure sensor 35 adapted to obtain braking pressure at the inlet opening of the chamber 2.

[0035] During normal operation of the hydraulic braking system 10, the actuating element 51 is not actuated by the actuator 5, so that the return element 6 pushes the piston 4 to the stationary position.

[0036] The chamber 2 and piston 4 are preferably designed such that when piston 4 is in the stationary position, the fluid volume is zero or approximately zero. That is, in the stationary position, piston 4 prevents brake fluid from entering the interior of chamber 2.

[0037] The locking state of wheel 107 can be further determined by means of an anti-lock sensor system (not shown in the figure). Based on the locking state, the necessity of the anti-lock function of anti-lock unit 1 is determined. If the anti-lock function is necessary, for example, if wheel 107 is locked or about to lock, the anti-lock operation of anti-lock unit 1 is started.

[0038] During anti-lock operation, the main valve 16 is closed and the actuator 5 actuates the piston 4 to actively adjust the braking pressure in the brake line 11 at the brake caliper 13. Specifically, the piston 4 is pulled back against the return force 60 to allow brake fluid to flow into the chamber 2, thereby reducing the braking pressure at the brake caliper 13. The piston 4 is then pushed in the opposite direction to increase the braking pressure again.

[0039] The rigidity 33 of the hydraulic braking system 10 can be determined by means of the anti-lock unit 1. The rigidity 33 is crucial to the rider's brake lever feel and is also related to the optimal performance of the anti-lock operation.

[0040] High rigidity 33 can also be considered as strong brake engagement. This means that a small increase in the travel of the brake lever will cause a significant increase in brake pressure. In contrast, low rigidity 33 causes a large travel of the brake lever to cause a small increase in brake pressure. Rigidity 33 depends in particular on the elasticity of the hydraulic braking system 10, such as the elasticity of the brake line 11 and the compressibility of the brake fluid.

[0041] For further explanation, please refer to Figure 3, which shows the pressure curve 24 of the braking pressure when the brake lever 19 is actuated. Figure 3 shows a curve 20, in which the pressure 21 of the brake fluid shows the volume 22 of the brake fluid in the hydraulic braking system 10.

[0042] Section 25 demonstrates brake lever actuation, after which the brake pads come into contact with the brake disc. That is, the brake fluid is displaced, but no significant increase in pressure has yet occurred. In Section 26, subsequent application of the brake pads and further actuation of the brake lever 19 cause a significant increase in brake pressure.

[0043] Rigidity 33 corresponds to the tangent of pressure curve 24 in zone 26. Specifically, rigidity 33 corresponds to the ratio of pressure change 31 to volume change 32.

[0044] The determination of rigidity 33 is performed as follows: Using the anti-lock unit 1, when at least a predefined minimum braking pressure in the hydraulic braking system is generated via the brake lever 19, a volume change 32 and a pressure change 31 are detected. If the predefined minimum braking pressure is exceeded, the main valve 16 closes, and when the main valve 16 closes, the piston 4 is actuated. During the actuation of the piston 4, the corresponding pressure change 31 is directly acquired by the pressure sensor 35. Additionally, the volume change 32 is simultaneously determined.

[0045] The determination of volume change 32 is based on the position change of piston 4. This position change is determined by means of magnetic sensor 8 (see Figure 2), which can acquire the longitudinal displacement of piston 4 along axis 50. The volume change 32 can be calculated in a simple way based on this longitudinal displacement and piston surface 40 of piston 4, through which piston 4 can apply pressure to brake fluid.

[0046] Rigidity 33 can therefore be determined based on the determined values ​​of pressure change 31 and volume change 32. To obtain particularly accurate results, noise reduction of one or both measurements can preferably be performed, for example, by means of a low-pass filter and / or by means of an RLS algorithm.

[0047] The determined rigidity 33 can then be used to adjust the controlled actuation of the piston 4. For example, the frequency and / or amplitude and / or actuation speed of the piston 4 can be adjusted to achieve the optimal desired braking action. [Simplified Explanation of the Diagram]

[0024] The invention will now be described with reference to the accompanying drawings and illustrative examples. In the drawings, functionally identical components are always identified by the same reference numerals. In the drawings: [Figure 1] is a simplified schematic view of an electric bicycle according to a preferred illustrative example of the invention, [Figure 2] is a simplified schematic view of the hydraulic braking system of the electric bicycle of Figure 1, and [Figure 3] is a simplified schematic view of the pressure curve of the hydraulic braking system of Figure 2 during braking actuation.

Claims

1. A method for determining the rigidity (33) of a hydraulic braking system (10), particularly for a hydraulic braking system of an electric bicycle (100), wherein the hydraulic braking system (10) has an anti-lock unit (1) having a piston (4) actuated in a controllable manner for active pressure modulation of a braking pressure, and wherein the method comprises the following steps performed during actuation of the piston (4): determining a volume change (32) of a braking fluid by the actuation of the piston (4), determining a pressure change (31) of the braking pressure, determining the rigidity (33) of the hydraulic braking system (10) as a ratio of the pressure change (31) to the volume change (32), wherein the volume change (32) is determined based on a position change of the piston (4), and determining a braking pressure in the hydraulic braking system (10), wherein the method is performed only when the determined braking pressure is at least equal to a predetermined minimum braking pressure.

2. The method of request item 1, wherein the predetermined minimum braking pressure is 50 bar.

3. The method of claim 1 or 2, wherein the method is performed only when the driver pulls the brake lever (19) of the hydraulic braking system (10).

4. The method of claim 1 or 2, wherein the hydraulic braking system (10) has a brake cylinder (15), a brake caliper (13), a brake line (11) connecting the brake cylinder (15) and the brake caliper (13), and a master valve (16) integrated in the brake line (11), and wherein the method is performed when the master valve (16) interrupts a fluid connection between the brake cylinder (15) and the brake caliper (13).

5. The method of claim 1 or 2, wherein the change in position of the piston (4) is determined to be a longitudinal displacement of the piston (4) within a chamber (2) of the anti-lock unit (1) and along an axis (50), and wherein the change in volume is determined based on the longitudinal displacement of the piston (4) and based on a piston surface (40) of the piston (4).

6. The method of claim 5, wherein the longitudinal displacement is determined by means of a magnetic sensor (8).

7. The method of claim 1 or 2 further includes the following steps: performing a noise reduction by means of determined measurements of the volume change and the pressure change.

8. The method of claim 7, wherein the noise reduction is performed by means of a low-pass filter.

9. The method of request item 7, wherein the noise reduction is performed by means of a recursive least squares algorithm.

10. The method of request item 9, wherein the parameters of the recursive least squares algorithm are adjusted as determined by the change in pressure (31).

11. The method of claim 1 or 2, wherein the method is used to calibrate the hydraulic braking system (10) in a two-wheeled vehicle, particularly an electric bicycle (100), and wherein the method is performed when the two-wheeled vehicle, particularly the electric bicycle (100), is stationary.

12. A method for operating a hydraulic braking system (10), particularly a hydraulic braking system of an electric bicycle (100), comprising the steps of: determining a rigidity (33) of the hydraulic braking system (10) by means of any one of claims 1 to 11, and actuating the piston (4) of the hydraulic braking system (10) during anti-lock operation of the anti-lock unit (1) of the hydraulic braking system (10) depending on the determined rigidity (33).

13. The method of claim 12, wherein, based on the determined rigidity (33), an amplitude and / or a frequency of a longitudinal displacement of the piston (4) is adjusted during an active pressure modulation of the braking pressure.

14. A hydraulic braking system for a two-wheeled vehicle, particularly a bicycle, preferably an electric bicycle (100), comprising: an anti-lock unit (1) having: a chamber (2) for containing a braking fluid; a piston (4) defined within a fluid volume in the chamber (2) and displaceable along an axis (50); an actuator (5) adapted to displace the piston (4) along the axis (50) in a controllable manner; a brake cylinder (15); a brake caliper (13); and a brake line (11) having a first segment (11a) fluidly connected to the chamber (2) and to the brake caliper (13), and a second segment (11b) connected to the brake cylinder (15). A main valve (16) integrated into the brake circuit (11) and a control device (61) adapted to perform a method for determining the rigidity (33) of the hydraulic brake system (10) as claimed in any of claims 1 to 11 or a method for operating the hydraulic brake system (10) as claimed in claims 12 or 13.

15. The hydraulic braking system of claim 14 further includes a pressure sensor (35) adapted to obtain a braking pressure at the brake caliper (13).

16. A two-wheeled vehicle, particularly a bicycle, preferably an electric bicycle (100), comprising a hydraulic braking system (10) as claimed in claim 14 or 15.

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