Brake assist device for vehicle and hydraulic brake device for vehicle

Abstract

A brake assist device (1) for a vehicle that can be driven by muscle power and / or an electric motor and a hydraulic brake device (2) is proposed. The brake assist device (1) includes a sensor (3) with a first piston (4), a compensation volume (5) with a second piston (6) and a pretensioning member (7), a 2-port 2-position directional control valve (8), a brake piston (9), and an actuator (11), where the pretensioning member (7) is designed to apply pressure to the second piston (6) and thus to the hydraulic fluid of the brake device (2), and the actuator (11) is designed to selectively move the second piston (6) in a first direction or a second direction opposite to the first direction.

Description

[Technical field]

[0001] The present invention relates to a brake assist device for vehicles and hydraulic brake devices for vehicles that can be driven by muscle power and / or electric motors. In particular, the present invention relates to E-bikes, Pedelecs, Lasten-E-Bikes and lightweight electric vehicles, such as wheelchairs. [Background technology]

[0002] Standard ABS implementation is done by incorporating a pump between the driver's hand force and a reserve chamber.

[0003] Such a conversion has a significant drawback in that the size of the reserve chamber is limited by legal minimum decelerations, severely limiting the compatibility of such a system with the basic brakes.

[0004] If a leak in the discharge valve would cause the reserve chamber to fill inadvertently during normal braking, the driver must ensure that the remaining brake lever stroke achieves a legally predetermined minimum deceleration, which means that the size of the reserve chamber must be limited, because otherwise if the reserve chamber is too large, the entire displacement volume of the brake lever will flow into it.

[0005] Such problems are very pronounced in bicycle brakes due to the limited displacement volume of the brake lever and the adjustable handbrake lever position. When the rider adjusts the lever close to the handlebars, the amount of brake fluid that can be displaced by the lever is reduced. Therefore, standard ABS circuits are not compatible with all conventional basic brakes, because the dimensions of the reserve chamber are limited to such an extent that ABS functionality cannot be guaranteed (insufficient brake pressure build-up is possible due to the small reserve chamber volume).

[0006] Patent Document 1 discloses a hydraulic brake system that uses an electric motor having a slidable piston.

[0007] The piston in the hand lever is directly connected to the reserve chamber. The piston, which is movable in the reserve chamber, is connected to an electric drive. A bypass is provided to guide the oil from the hand lever to the brake caliper. If the wheel locks, the spring-supported piston is displaced by the power of the motor. Depending on the position of the piston, the bypass between the hand lever and the brake caliper is disconnected. By displacing the piston further, the pressure in the brake caliper can be adjusted.

[0008] This idea cannot be applied to the reserve chamber, but the pressure reduction is performed by applying a force to the brake lever by the piston, so that the driver is always provided with a sufficient brake lever stroke to achieve the legal minimum deceleration, thereby ensuring compatibility with the basic brake. The problem with this system is that the electric motor must work against the hand pressure generated by the driver, which varies from driver to driver. If the hand pressure is too high, the actuator may no longer be able to apply the torque required to move the piston. This situation is particularly dangerous when braking, especially on loose surfaces, because a large pressure difference occurs between the chambers, which must be compensated for by the actuator. Moreover, high hand pressure significantly increases the power demand, which means that the energy source or the battery must supply more power to the motor.

[0009] Patent document 2 discloses a brake assist system without an intake valve. This brake assist system further reduces the installation space occupied by the system, but has the disadvantage that no gradient control is possible in order to limit the brake pressure gradient. This allows the driver to build up pressure in the brake system. Another drawback of this brake system is that in the event of an actuator failure, the piston can reduce the pressure in the brake line below 1 bar. Due to the generated negative pressure, the actuator sucks air through the seal into the hydraulic system, thereby threatening its functionality. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] European Patent Application Publication No. 3124344 [Patent Document 2] International Publication No. 2018 / 083615 Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to propose an improved conception and an improved design of the mechanical components of a hydraulic brake assist system, thereby eliminating the drawbacks known from the prior art, at least maintaining the functionality and possibly simplifying the construction. [Means for solving the problem]

[0012] The object is achieved according to the invention by a brake assist device for a hydraulic braking system for vehicles that can be driven by muscle power and / or electric motors. The brake assist device has a sensor with a first piston. To actuate the first piston, the sensor has a hand lever or is associated with this hand lever. The first piston acts on a first line section of the hydraulic braking system. In addition, a compensation volume with a second piston is provided. The second piston is arranged in the compensation volume in such a way that it applies pressure to the hydraulic / brake fluid by means of a pretensioning element (e.g. a pretensioning spring). For this purpose, the compensation volume forms or has a cylinder associated with the second piston. In particular, the volume located beyond the second piston relative to the pretensioning element is filled with hydraulic fluid. A 2 / 2-way directional control valve follows the first line section. The 2 / 2-way directional control valve is therefore fluidly connected to the first piston of the sensor. The 2 / 2-way directional control valve may also be interpreted as an intake valve arrangement or a controllable intake valve. The 2 / 2-way directional control valve is actuated as a function of the wheel speed in order to prevent the wheel from being permanently locked. For this purpose, the 2 / 2-way directional control valve is associated with a brake piston in a brake caliper associated with the wheel. According to the invention, an actuator is also provided which is associated with the second piston in the compensation volume. The pretensioning element is designed to apply pressure to the second piston and thus to the hydraulic fluid of the brake system. In particular, the pretensioning element can be designed to influence the pressure in a second line section of the hydraulic system which is arranged opposite the 2 / 2-way directional control valve in relation to the sensor. The actuator is designed to selectively move the second piston in a first direction or in a second direction opposite to the first direction. In other words, the actuator can increase or decrease the force action on the second piston, which is generated by the pretensioning element.It may be said that the actuator is designed to displace the second piston differently, particularly in opposite directions, around a working point that is adjusted by the pretensioning member and the hydraulic fluid, depending on the direction of force application. In this way, the brake assist system according to the invention can also adjust the brake pressure below the reserve chamber preload.

[0013] To ensure that the braking system according to the invention guarantees the legally required minimum deceleration in the event of an AV (outlet valve) leak, one solution is the adjustment of the reserve chamber spring bias. By detailed analysis of the various basic brakes, the brake pressure required for each brake has been calculated in order to obtain the legally required minimum deceleration. This value varies between approximately 30 bar or approximately 50 bar. If the reserve chamber spring is biased with a biasing force corresponding to 50 bar of hydraulic pressure, the system is guaranteed to always obtain the legally required minimum deceleration, even in the event of an AV (outlet valve) leak.

[0014] The dependent claims indicate preferred embodiments of the invention.

[0015] The actuator may, for example, comprise an electric motor with a spindle drive, which is in particular coaxial with the direction of movement of the second piston or with the axis of symmetry of the second piston, so that a sufficiently strong force action is ensured both in the first direction and in the second direction.

[0016] A discharge valve may preferably be provided between the brake piston and the compensation volume. The discharge valve may be configured similarly to the intake valve or the 2 / 2-way directional control valve. However, in comparison with the 2 / 2-way directional control valve, the discharge valve is designed to close in the absence of an applied signal, whereas the 2 / 2-way directional control valve of the intake valve may be designed to pass hydraulic fluid in the absence of an applied signal. In the event of a failure of the discharge valve (e.g. in the event of a power failure after a reduction in brake pressure (e.g. after a negative mu jump), i.e. after a sudden decrease in the coefficient of friction between the tire and the road), the discharge valve closes and the preload element is unable to displace brake fluid / hydraulic fluid from the compensation volume. As a solution, an arrangement can be proposed in which a check valve is arranged between the discharge valve and the compensation volume on the one hand and between the sensor and the 2 / 2-way directional control valve on the other hand (first line section). The check valve may be oriented in such a way that a flow in the direction towards the sensor is always permitted. Thus, the check valve allows the preload member to displace hydraulic fluid from the compensation volume to provide braking to the driver / sensor even if the discharge valve is closed in the event of a failure.

[0017] A similar effect can be achieved by connecting a check valve between the delivery valve and the compensation volume on the one hand and between the 2 / 2-way directional control valve and the brake piston on the other hand, where again the flow can be allowed either towards the brake piston or towards the 2 / 2-way directional control valve.

[0018] In order to avoid a miscontrol of the actuator, which would cause the piston to generate a negative pressure and thus suck air into the hydraulic system, a separable connection can be provided between the second piston and the actuator. This connection can be interpreted as a so-called selectively rigid connection or a selectively loose connection. In particular, the connection is provided to the second piston in a rigid manner in relation to the pressure of the actuator, whereas the actuator cannot or can only indirectly pull the second piston out of the area filled with hydraulic fluid. For example, the actuator can be connected to the piston with a tensile force only via a pretensioning element, whereas the actuator can be rigidly connected or in contact with the second piston with a compressive force. Due to the releasable connection, the movement of the piston out of the hydraulic system is exclusively forced by the hydraulic pressure, so that the piston does not move out of the hydraulic system to any great extent as soon as the brake pressure reaches 1 bar. This means that a balance with the ambient pressure is always maintained.

[0019] In an ideal form, the pretensioning element is designed in cooperation with the second piston (without the force action of the actuator) to generate a hydraulic pressure of at least 40 bar, in particular 50 bar, preferably 60 bar. In other words, the working point can be adjusted to 40 or 50 bar, preferably 60 bar, and then adjusted by the actuator. If the pressure in the hydraulic system is higher, the number of situations in which the electric motor must be operated can be reduced in order to avoid brake fluid flowing into the compensation volume. However, very high values ​​must be avoided, since a higher hydraulic working point position adversely affects the dynamics and power consumption of the system.

[0020] The pretensioning element may comprise a spiral spring, in other words the second piston is pressed in the direction towards the hydraulic fluid by the spiral spring, in the case of a separable connection the spiral spring is arranged on the second piston on the one hand and on the actuator on the other hand, whereby it also optionally applies a pulling force when the actuator tries to pull the second piston out of the hydraulic system by means of the spiral spring.

[0021] According to a second aspect of the present invention, a vehicle capable of being driven by muscle power and / or an electric motor (in particular an E-Bike, Pedelec, electric road bike, electric light vehicle, wheelchair, E-Trike or E-Quad) is proposed, which comprises a brake assist device according to the first aspect of the present invention. The features, the combinations of these features and the advantages resulting therefrom have been described in detail above in relation to the first aspect, and reference is made to the first aspect of the present invention to avoid repetition. [Brief description of the drawings]

[0022] [Figure 1] 1 is a schematic diagram of an E-bike constructed in accordance with the present invention having a brake assist device constructed in accordance with the present invention; [Diagram 2] 1 is a brake system constructed in accordance with the prior art in a first operating condition having a substantially empty correction volume; [Diagram 3] 1 is a brake system constructed in accordance with the prior art in a first operating condition with a filled compensation volume; [Figure 4] 1 is a first embodiment of a brake assist device without a discharge valve, constructed according to the present invention. [Diagram 5] 2 is a second embodiment of a brake assist device having a discharge valve configured according to the present invention. [Figure 6] 3 is a third embodiment of a brake assist device having a check valve configured according to the present invention. [Figure 7]4 is a fourth embodiment of a brake assist device having a check valve configured according to the present invention. [Figure 8] 1 is a cross-sectional view showing details of one embodiment of an actuator that can be used in accordance with the present invention, the actuator having a selectively severable connection to a second piston; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, several embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0024] 1 shows an e-bike 10 as an example of a means of transport constructed according to the invention, with an embodiment of a brake assist device 1 for a hydraulic brake device 2. A brake piston 9 is provided in each of the brake calipers of the front and rear wheels of the e-bike 10. The brake pistons 9 are fluidly connected via hydraulic hoses 16 to the hand lever 3 as a sensor and to a control unit 17. A battery 18 providing traction energy further powers the sensor and actuator devices as well as the solenoid valves of the brake assist device 1.

[0025] 2 shows a brake assist device 1 for a hydraulic braking system 2, constructed according to the prior art, in a first operating state. A pump 19 is used here to supply hydraulic fluid, which is temporarily stored via the discharge valve 13 and, if necessary, in the compensation volume 5, to the sensor 3 or to the first piston 4 and the 2 / 2-position directional control valve 8 via the check valve 14. The compensation volume 5 is essentially emptied in the illustrated operating state. The pretensioning element as a spiral spring 7 is stress-relieved due to the relatively empty compensation volume 5.

[0026] Figure 3 shows the situation according to figure 2, in which the compensation volume 5 is almost completely filled. The hydraulic hose 16 closes the circuit between the 2 / 2 directional control valve 8 and the delivery valve 13 or connects the brake piston 9 to the hydraulic circuit. The pretensioning element 7 as a spiral spring is strongly compressed due to the filled compensation volume 5.

[0027] FIG. 4 shows a first embodiment of a brake assist device 1 according to the invention for a hydraulic braking system 2. Via a sensor hand lever 3 and a first piston 4, the hydraulic fluid flows through a 2 / 2-way directional control valve 8 as a function of a control signal and via a hydraulic hose 16 towards a brake piston 9. A compensation volume 5 is provided for intermediate storage of the outflowing hydraulic fluid. The working point or hydraulic pressure is adjusted via a pretensioning element 7 as a spiral spring. An actuator as a spindle motor 11 is operatively connected to the second piston 6 via a separable connection (not shown). The spindle motor 11 can thereby exert tensile and compressive forces on the second piston 6.

[0028] Figure 5 shows the arrangement proposed in Figure 4, in which a controllable delivery valve 13 is provided between the compensation volume 5 and the brake piston 9 or between the 2 / 2 directional control valve 8. Depending on the control signal the delivery valve 13 is opened, in the absence of a control signal the delivery valve 13 is closed.

[0029] Figure 6 shows the arrangement proposed in Figure 5, obtained by interposing a check valve 14 between the discharge valve 13 and the compensation volume 5 on the one hand and the first piston 4 or the 2 / 2-way directional control valve 8 on the other hand. This allows a backflow of hydraulic fluid from the compensation volume 5 towards the 2 / 2-way directional control valve 8 at any time while the check valve 14 is closed towards the compensation volume 5.

[0030] 7 shows an arrangement which is modified compared to FIG. 6 in that the check valve 14 is not connected to the first line section but to the second line section between the 2 / 2-way directional control valve 8 and the brake piston 9. Furthermore, a sensor 20 is arranged in the area of ​​the brake piston 9, which determines the wheel speed and outputs a correspondingly generated control signal to the 2 / 2-way directional control valve 8.

[0031] FIG. 8 shows a detailed cross-sectional view of the actuator 11 with the spindle drive 12. The spindle drive 12 is connected to the second piston 6 via a selectively separable connection 15. When the spindle drive 12 is pressed against the second piston 6, the position of the spindle drive 12 and the position of the second piston 6 are directly connected to each other. When the spindle drive 12 is removed from the second piston 6, the spindle drive 12 and the piston 6 are connected to each other only via the spiral spring 7. For this reason, the actuator 11 can compress the large spring 7 by the spring retainer 21 and the spindle 12. The small piston 6 has another small spring 22, which is not connected to the spring retainer 21 in a rigid connection. When the spring retainer 21 and the spindle 12 move upwards, they push the small piston 6 upwards. When the spring retainer 21 and the spindle 12 move downwards, the hydraulic pressure moves the piston 6 downwards. If there is no pressure in the brake line, the piston 6 will not move downwards and the connection between the piston and the spindle 12 / spring seat 21 will be open. [Explanation of symbols]

[0032] 1 Brake assist device 2. Hydraulic brake system 3 Hand lever, sensor 4. First Piston 5 Compensation volume 6 Second piston, small piston 7 Spiral springs, pretension members 8 2-port 2-position directional control valve 9 Brake piston 10 Vehicles, E-bikes 11 Spindle motor, actuator 12 Spindle drive unit, spindle 13 Discharge valve 14 Check valve 15 Connection 16 Hydraulic hose 17 Control Unit 18 Battery 19 Pump 21 Spring holder 22 Small Spring

Claims

1. A brake assist device for a hydraulic brake system (2) for a vehicle (10) that can be driven by muscle power and / or an electric motor, comprising: The brake assist device (1), a sensor (3) equipped with a first piston (4); a compensation volume (5) comprising a second piston (6) and a pretensioning member (7); A two-port two-position directional control valve (8); A brake piston (9); an actuator (11) including an electric motor with a spindle drive (12); the pretensioning member (7) is designed to cover the outer circumference of the spindle drive (12) and to apply pressure to the second piston (6) and thus to the hydraulic fluid of the brake device (2); the actuator (11) is designed to selectively move the second piston (6) in a first direction or in a second direction opposite to the first direction; A brake assist device for a hydraulic braking system.

2. 2. The brake assist device according to claim 1, wherein the sensor (3) comprises a hand lever.

3. A discharge valve (13) is provided between the brake piston (9) and the compensation volume (5), and further a check valve (14) is provided between the discharge valve (13) and the compensation volume (5) on the one hand, and between the sensor (3) and the 2-port 2-position directional control valve (8) on the other hand; The brake assist device according to claim 1 or 2.

4. A discharge valve (13) is provided between the brake piston (9) and the compensation volume (5), and further 3. The brake assist device according to claim 1, further comprising a check valve (14) provided between the discharge valve (13) and the compensation volume (5) on the one hand and between the 2 / 2 directional control valve (8) and the brake piston (9) on the other hand.

5. 5. The brake assist device according to claim 1, further comprising a selectively separable connection between the actuator (11) and the second piston (6).

6. 6. A brake assist device according to claim 1, wherein the pretensioning element (7) is designed to generate a hydraulic pressure of at least 40 Bar.

7. 7. A brake assist device according to claim 1, wherein the pretensioning element (7) comprises a coil spring.

8. A vehicle (10) that can be driven by muscle power and / or an electric motor, in particular an E-bike or a pedelec, comprising a brake assist device (1) according to any one of claims 1 to 7.

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