Electromechanical brake

Abstract

The invention relates to an electromechanical brake (10) for a motor vehicle. The electromechanical brake (10) comprises a brake caliper housing (14) in which a displacement piston (22) is arranged, which is movable via an electric drive (18) and via which a hydraulic brake fluid can be displaced in a pressure chamber (26) such that at least one brake piston (30) is axially movable for braking. The pressure chamber (26), in which the displacement piston (22) is movable, is partially delimited by the at least one brake piston (30), and the displacement piston (22) is connected to the brake piston (30) via a spring element (34) such that at least one compressive force (FD) can be transmitted to the brake piston (30) via the spring element (34).

Description

[0001] The present invention relates to an electromechanical brake for a motor vehicle. Furthermore, the invention relates to a motor vehicle having such an electromechanical brake. State of the art

[0002] Typically, the service brake is a brake in which a brake piston, together with a brake pad, is pressed onto a brake disc via brake fluid to brake the vehicle. The parking brake, on the other hand, is designed as an electromechanical brake. With the increasing electrification of motor vehicle components, the service brake is also to be designed as an electromechanical brake, thus eliminating the need for brake fluid and the associated complex valve and line assembly. Such an electromechanical brake could also significantly reduce maintenance requirements.

[0003] WO 01 / 36837 A1 describes an electromechanical brake. The brake comprises an electric motor mounted on the brake caliper, which drives a pressure piston through which brake fluid can be pressurized. The pressure is transmitted via brake lines in the brake caliper to four brake pistons located on either side of the brake disc. These pistons allow the brake pads to be applied to the brake disc. Additionally, a reservoir is provided in the brake caliper to supply brake fluid.

[0004] EP 1 195 538 A1 describes an electrically controlled brake. The brake comprises a solenoid coil with a movable armature connected to a piston. This piston opens into a pressure chamber. At an opposite end of the pressure chamber, a larger brake piston is arranged, to which a brake pad is attached. By activating the solenoid coil, braking pressure is applied to the brake piston via the armature connected to the piston.

[0005] The object underlying the invention is to provide an electromechanical brake for a motor vehicle which can be manufactured more easily and economically and with which greater safety can be achieved.

[0006] The object is achieved by an electromechanical brake having the subject matter of patent claim 1. Preferred embodiments can be found in the dependent claims. Disclosure of the invention

[0007] The invention specifies an electromechanical brake for a motor vehicle. The electromechanical brake comprises a brake caliper housing in which a displacement piston is arranged, which is movable via an electric drive and via which a hydraulic brake fluid can be displaced in a pressure chamber, so that at least one brake piston is axially movable for braking. The pressure chamber, in which the displacement piston is movable, is partially delimited by the at least one brake piston, and the displacement piston is connected to the brake piston via a spring element such that at least one compressive force can be transmitted to the brake piston via the spring element.

[0008] A displacement piston is a piston that increases the pressure in the pressure chamber by displacing the hydraulic brake fluid. The increased pressure acts on the brake piston and moves it towards a brake disc to be braked. A spring element is an element that changes its length and spring force through the movement of the displacement piston or the brake piston. During a braking maneuver, the spring element applies a force to the brake piston in addition to the hydraulic brake fluid. The spring element is arranged between the displacement piston and the brake piston and has the advantage that when the parking brake is engaged and there is a leak in the hydraulic brake fluid, the brake piston is held in a braked position by the spring element. This improves the safety of the electromechanical brake.

[0009] The arrangement, in which the braking force is transferred to the brake piston via the hydraulic brake fluid, has the advantage that no transverse forces or bending moments caused by the brake pad act on the electrically driven displacement piston. The displacement piston, which is preferably designed as a ball screw, can therefore be smaller. Furthermore, the bearing for the displacement piston can be smaller and simpler, since it does not have to absorb transverse forces or bending moments. The displacement piston can therefore be designed in a simpler and more economical manner.

[0010] By transmitting the braking force via the hydraulic brake fluid, the noise and vibration of the electromechanical brake are also improved.

[0011] In a preferred embodiment of the invention, the spring element is arranged between the displacement piston and the brake piston in such a way that a tensile force can also be transmitted to the brake piston. Advantageously, the spring element is firmly connected both to the brake piston and to the displacement piston. This makes it possible to actively retract the brake piston via the spring element when the displacement piston moves in a brake release direction. This minimizes dragging of the brake pad against the brake disc. Furthermore, it is also possible to actively adjust the clearance between the brake disc and the brake pad. For example, in predefined situations, the clearance can be reduced to enable faster braking.

[0012] In a further preferred embodiment of the invention, at least one additional brake piston is provided, which is hydraulically connected to the pressure chamber and is axially opposite the brake piston connected to the displacement piston. The additional brake piston is thus located on a different side of the brake caliper housing. This allows a different side of the brake disc to be braked via the additional brake piston. This eliminates the need for a complex and expensive floating caliper.

[0013] Preferably, the pressure chamber has a connection for a hydraulic line of a fallback brake pressure generation system. The fallback brake pressure generation system can be a separate braking system or a brake pressure generated by the driver via a brake pedal. Such a connection thus allows brake pressure to be generated for braking, even in the event of a failure of the electric drive, for example. This improves the reliability of the electromechanical brake.

[0014] In an advantageous refinement, the displacement piston has a smaller surface area than the brake piston. By appropriately selecting the surface area of the brake piston and the surface area of the displacement piston, a power transmission ratio can be easily achieved. This eliminates the need for a complex gear system between the electric drive and the displacement piston for transmission.

[0015] Advantageously, a displacer piston center axis has an angle or axial offset to a brake piston center axis. If there is an angle between the displacer piston center axis and the brake piston center axis, the two axes are neither coaxial nor parallel to one another. Rather, both axes have an angle to one another. By transmitting the braking force via the hydraulic brake fluid, a coaxial alignment is no longer necessary. This allows the electric drive to be arranged according to the available space. This improves the utilization of the available installation space. The utilization of the available installation space is also improved by an axial offset of the displacer piston center axis and the brake piston center axis. With an axial offset, the axes run parallel, but there is a distance between the axes.

[0016] In a further advantageous embodiment, the electromechanical brake is designed with a fixed caliper or a floating caliper. Using a fixed caliper over a floating caliper has the advantage that it is significantly more cost-effective to manufacture. Using a floating caliper, on the other hand, has the advantage that an additional brake piston is omitted. Despite all this, the invention allows the use of both a floating caliper and a fixed caliper. Depending on the customer's requirements, the invention is thus versatile.

[0017] According to a practical embodiment, the spring element is designed as a wire spring or as an elastic solid body. The elastic solid body is a body made of an elastic material. Such a material can be used to achieve damping in addition to a spring effect. By appropriately selecting the elastic material, it is possible to achieve both a degressive and a progressive stiffness characteristic. Such an elastic solid body can thus be very well designed to meet the required requirements. Advantageously, the elastic solid body is arranged between the displacement piston and the brake piston in such a way that it is subjected to pressure during a braking maneuver.

[0018] The wire spring has the advantage of being available in a wide range of stiffnesses. Furthermore, this spring can be positioned between the displacement piston and the brake piston as either a compression-loaded or a tension-loaded spring. In other words, the spring is subjected to either a tension or compression load during a braking maneuver.

[0019] According to another practical embodiment, the spring element is designed as a bellows spring. A bellows spring has the advantage of offering high rigidity while requiring minimal installation space. The bellows spring can be used either as a tension-loaded bellows spring or as a compression-loaded bellows spring. In a tension-loaded bellows spring, the spring is arranged between the displacement piston and the brake piston in such a way that it is subjected to a tensile load during braking. Similarly, a compression-loaded bellows spring is compressed during a braking maneuver.

[0020] Advantageously, a pressure sensor is arranged in the area of the pressure chamber. The pressure sensor is positioned in such a way that the pressure in the pressure chamber can be measured. The pressure in the pressure chamber can be used to easily measure the braking force. This information can be made available, for example, to a brake control system, allowing the braking force to be more effectively controlled.

[0021] The invention also provides a motor vehicle having such an electromechanical brake. Such a motor vehicle has the advantages and properties described above.

[0022] Embodiments of the invention are illustrated in the drawing and explained in more detail in the following description. It shows: Fig. 1 sectional view of an electromechanical brake according to a first embodiment of the invention, Fig. 2 Sectional view of the electromechanical brake according to a second embodiment of the invention, Fig. 3a Second embodiment of the spring element according to the invention, Fig. 3b Third embodiment of the spring element according to the invention, Fig. 3c Fourth embodiment of the spring element according to the invention, Fig. 4a Fifth embodiment of the spring element according to the invention, and Fig. 4b Sixth embodiment of the spring element according to the invention.

[0023] In Fig. Figure 1 shows a sectional view of an electromechanical brake 10 according to a first exemplary embodiment of the invention. The electromechanical brake 10 comprises a brake caliper housing 14, which surrounds a brake disc (not shown here) on both sides. An electric drive 18 is arranged on the brake caliper housing 14, via which a displacement piston 22 is axially movable. The displacement piston 22 extends into a pressure chamber 26 of the brake caliper housing 14, in which a hydraulic brake fluid is provided. A brake piston 30 is arranged for axial movement at one end of the pressure chamber 26. In this exemplary embodiment, the brake piston 30 is arranged coaxially with the displacement piston 22. An axial surface 32 of the displacement piston 22 is smaller than an axial surface 33 of the brake piston 30.

[0024] A spring element 34 is arranged between the displacement piston 22 and the brake piston 30. In this embodiment, the spring element 34 is designed as a wire spring. In addition to the hydraulic brake fluid, a compressive force F D to the brake piston 30. A connection 38 for a hydraulic line 42 of a fallback brake pressure generation system 46 is connected to the pressure chamber 26. If, for example, the electric drive 18 fails, brake pressure can still be generated via the fallback brake pressure generation system 46. The fallback brake pressure generation system 46 can be represented by an additional electric brake pressure generator or by the brake pedal. This increases the reliability of the electromechanical brake 10.

[0025] Although sufficient brake pressure can be transmitted to the brake piston 30 via the hydraulic brake fluid through the displacement piston 22, a leak in the pressure chamber 26 can cause the brake pressure to decrease, particularly when stationary, so that the parking brake is released. With the help of the spring element 34, a sufficient pressure force F can be maintained despite the leak. D to the brake piston 30, so that the vehicle remains braked while stationary. This increases the safety of the electromechanical brake 10.

[0026] The Fig. The electromechanical brake 10 shown in Figure 1 is designed as a fixed-caliper brake. Accordingly, on a side of the brake caliper housing 14 opposite the brake piston 30, a further brake piston 50 is arranged, which acts in the opposite direction to the brake piston 30. The further brake piston 50 defines a further pressure chamber 54, which is hydraulically connected to the pressure chamber 26 via a hydraulic channel 58 formed in the brake caliper housing 14.

[0027] Fig. Figure 2 shows a sectional view of the electromechanical brake 10 according to a second embodiment of the invention. This embodiment differs from that shown in Fig. 1 in that a displacement piston center axis 62 has an angle β to a brake piston center axis 66. Accordingly, the displacement piston 22 does not have to be arranged coaxially to the brake piston 30. The electric drive 18 and the displacement piston 22 can thus be positioned according to the available space. It is also possible for the displacement piston center axis 62 to have an axial offset from the brake piston center axis 66. Fig. 2 further differs in that a pressure sensor 70 is arranged on the brake caliper housing 14 in the area of the pressure chamber 26. This pressure sensor 70 enables simple braking force measurement.

[0028] Fig. Figure 3a shows a second embodiment of the spring element 34 according to the invention. In this embodiment, the spring element 34, designed as a wire spring, is firmly connected to both the brake piston 30 and the displacement piston 22 via a fastening 72. This makes it possible not only to apply a compressive force F D , but also when retracting the displacement piston 22 a tensile force F Z to the brake piston 30. The brake piston 30 and thus a brake pad can thereby be actively released from the brake disc after a braking operation.

[0029] Fig. 3b shows a third embodiment of the spring element 34 according to the invention. In this initial example, the spring element 34 is designed as an elastic solid body. In this embodiment, too, the elastic solid body 34 is firmly connected both to the displacement piston 22 and to the brake piston 30. The spring element 34 is accordingly made of an elastic material. An air space 74 is formed between the brake piston 30 and the elastic solid body 34. Such an arrangement allows a non-linear stiffness characteristic to be formed. This can be degressive or progressive. The elastic solid body 34 and the air space 74 additionally provide damping between the displacement piston 22 and the brake piston 30.

[0030] A fourth embodiment of the spring element 34 is shown in Fig. 3c. In this exemplary embodiment, the spring element 34 is designed as a tension-loaded bellows spring. This is also firmly connected to the brake piston 30 and the displacement piston 22. Although a coaxial alignment between the displacement piston 22 and the brake piston 30 is shown in this figure, an angle β or axial offset between the center axes 62, 66 is also possible. Such a bellows spring 34 has the advantage that, in addition to high rigidity, it requires a small installation space.

[0031] Fig. Figure 4a shows a fifth embodiment of the spring element 34 according to the invention. In this embodiment, the spring element 34 is designed as a compression-loaded spiral spring. In this embodiment, too, the spiral spring 34 is firmly connected to both the brake piston 30 and the displacement piston 22. The spiral spring 34 enables high rigidity in a small installation space. Fig. 4b shows another example of a bellows spring 34. In contrast to Fig. 3c, this bellows spring 34 is a pressure-loaded bellows spring 34. By this bellows spring 34, which is already Fig. The advantages and properties described in 3c are achieved. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 01 / 36837 A1

[0003] EP 1 195 538 A1

[0004]

Claims

[1] Electromechanical brake (10) for a motor vehicle, comprising a brake calliper housing (14) in which a displacement piston (22) is arranged, which is movable via an electric drive (18) and via which a hydraulic brake fluid can be displaced in a pressure chamber (26), so that at least one brake piston (30) is axially movable for braking, characterized by that the pressure chamber (26), in which the displacement piston (22) is movable, is partially delimited by the at least one brake piston (30) and the displacement piston (22) is connected to the brake piston (30) via a spring element (34) in such a way that at least one pressure force (F D ) can be transferred to the brake piston (30). [2] Electromechanical brake (10) according to claim 1, characterized by that the spring element (34) is arranged between the displacement piston (22) and the brake piston (30) in such a way that an additional tensile force (F Z) can be transferred to the brake piston (30). [3] Electromechanical brake (10) according to claim 1 or 2, characterized by that at least one further brake piston (50) is provided, which is hydraulically connected to the pressure chamber (26) and is axially opposite the brake piston (30) connected to the displacement piston (22). [4] Electromechanical brake (10) according to one of the preceding claims, characterized by that the pressure chamber (26) has a connection (38) for a hydraulic line (42) of a fallback brake pressure generation system (46). [5] Electromechanical brake (10) according to one of the preceding claims, characterized by that the displacement piston (22) has a smaller area (32, 33) than the brake piston (30). [6] Electromechanical brake (10) according to one of the preceding claims, characterized by that a displacement piston center axis (62) has an angle (β) or axial offset to a brake piston center axis (66). [7] Electromechanical brake (10) according to one of the preceding claims, characterized by that the electromechanical brake (10) is designed with a fixed caliper or a floating caliper. [8] Electromechanical brake (10) according to one of the preceding claims, characterized by that the spring element (34) is designed as a wire spring or as an elastic solid body. [9] Electromechanical brake (10) according to one of claims 1 to 7, characterized by that the spring element (34) is designed as a bellows spring. [10] Electromechanical brake (10) according to one of the preceding claims, characterized by that a pressure sensor (70) is arranged in the region of the pressure chamber (26). [11] Motor vehicle comprising an electromechanical brake (10) according to one of the preceding claims.

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