Electromechanical brake pressure generator with anti-torsion section

Abstract

The present invention relates to an electromechanical brake pressure generator (14) for a hydraulic braking system (10) of a vehicle, having at least one threaded drive device (40). The threaded drive device (40) includes a spindle (68) and a spindle nut (76) interacting via a thread (72), and the electromechanical brake pressure generator has an electric actuator (38) through which the spindle (68) and the spindle nut (76) are rotatable relative to each other. A hydraulic piston (80) is housed in a hydraulic cylinder (64) of a piston / cylinder unit (18), the hydraulic cylinder forming anti-torsion portions (84, 88), wherein the anti-torsion portions (84, 88) are formed by a recess (88) and a sliding element (84) extending into the recess (88), such that the hydraulic piston (80) is fixed to prevent torsion and is axially movable by rotation of the spindle (68), the recess extending in the axial direction and forming a sliding surface (100). The contact surface (96) of the sliding surface (100) and / or the sliding element (84) that interacts with the sliding surface (100) has a microformed part (104) whose forming direction is configured to be orthogonal to the movement of the hydraulic piston (80).

Description

Technical Field

[0001] This invention relates to an electromechanical brake pressure generator for a hydraulic braking system of a vehicle. The electromechanical brake pressure generator particularly includes a threaded drive mechanism for converting rotary motion on the drive side into translational motion for piston actuation of a piston / cylinder unit.

[0002] Since a driver's foot pressure is often insufficient to brake a motor vehicle, they are typically equipped with brake force amplifiers. Traditional brake force amplifiers usually operate using the negative pressure generated by the internal combustion engine. Here, the pressure difference between the engine pressure and ambient pressure is utilized to apply an amplified force to the piston rod of the piston / cylinder unit, in addition to the force exerted by the driver's foot.

[0003] For the future drive concept of motor vehicles, an alternative brake pressure building device is needed because negative pressure can no longer be used to operate traditional vacuum brake amplifiers. The electromechanical brake pressure generator of interest here was developed for this purpose.

[0004] The operating force on this master brake cylinder is generated by an electric motor. This electromechanical brake pressure generator can not only provide auxiliary force, but also provide operating force independently in a brake-on-line system. Therefore, the electromechanical brake pressure generator is particularly advantageous for autonomous driving. Background Technology

[0005] DE 10 2019 205 911 A1 discloses an electromechanical brake pressure generator for a hydraulic braking system of a vehicle. The electromechanical brake pressure generator has a threaded drive device having a main shaft and a main shaft nut. The main shaft nut forms an anti-torsion portion with a housing, which is formed by a torque support member of the main shaft nut, the torque support member being fitted into an axially recessed portion in the housing. The main shaft nut is prevented from torsion by the anti-torsion portion. When the main shaft rotates, the torque support member moves axially within a recess.

[0006] The objective of this invention is to provide an electromechanical brake pressure generator with a threaded drive device having a longer service life.

[0007] To solve this task, an electromechanical brake pressure generator with a threaded drive mechanism, having the features of claim 1, is described. This task is additionally solved by a method for manufacturing such an electromechanical brake pressure generator, having the features of claim 5. Advantageous improvements of the invention can be derived in the corresponding dependent claims. Summary of the Invention

[0008] This invention describes an electromechanical brake pressure generator for a hydraulic braking system of a vehicle. The electromechanical brake pressure generator has at least one threaded drive device for converting rotational motion on the drive side into translational motion for generating brake pressure, and a piston / cylinder unit operable by the threaded drive device for generating brake pressure, the piston / cylinder unit comprising a hydraulic piston. The threaded drive device includes a spindle and a spindle nut interacting via threads, and has an electrically driven actuator that is rotatable relative to each other via the spindle and spindle nut.

[0009] The hydraulic piston is housed in the hydraulic cylinder of the piston / cylinder unit, and the hydraulic cylinder forms an anti-torsion section. The anti-torsion section is formed by a recess and a sliding element extending into the recess, such that the hydraulic piston is fixed to prevent torsion and can move axially by the rotation of the main shaft. The recess extends in the axial direction and forms a sliding surface.

[0010] In the context of this invention, both pure spindle drive devices and ball screw drive devices are understood as threaded drive devices, where the spindle nut is in direct contact with the spindle in a pure spindle drive device. A ball screw drive device is a helical gear drive device with balls inserted between the spindle and the spindle nut. Both components have helical grooves, which together form a helical tube filled with balls. The form-fit connection across the helix in the thread does not occur between the thread groove and the stop as in a pure spindle drive device, but rather through the balls.

[0011] In the context of this invention, torsion is understood as rotational motion about the axial axis of the spindle nut. As the driven spindle rotates, the spindle nut can move axially accordingly, so that the rotational motion of the motor or spindle can be converted into the translational motion of the spindle nut. Anti-torsion components are arranged here in the radial region or on the outer peripheral surface of the spindle nut.

[0012] The invention is characterized in that the contact surface of the sliding surface and / or the sliding element that interacts with the sliding surface has a micro-shaped part, the forming direction of which is configured to be orthogonal to the movement of the hydraulic piston.

[0013] A microformed part is a structure that differs from a plane by an order of micrometers. Therefore, protrusions and depressions are created on the contact or sliding surface by the microformed part. These protrusions and depressions are not arranged in a point-like manner, but rather extend continuously over at least a portion of the contact surface. The direction of extension of the protrusions or depressions of the microformed part is configured to be orthogonal to the axial direction of movement or configured to be along the radial direction of the spindle nut.

[0014] At least one converging gap is formed between the sliding surface and the contact surface along the direction of motion by a micro-formed part. The area in front of the protrusion in the direction of motion thus serves as a lubricant deposition area. Through the lubricant deposition area, a lubricating film can be formed between the sliding surface and the contact surface within a short stroke of the spindle nut. In addition, the lubricant deposition area ensures that the lubricating film will not tear. Thus, the solid friction between the sliding surface and the contact surface can be quickly overcome. Therefore, wear is stopped or at least reduced, and thus the service life of this electromechanical braking pressure generator is increased. Similarly, the force used to move the spindle nut is also reduced.

[0015] In an advantageous embodiment, the sliding element has a contact shoe forming a contact surface, which is applied to the sliding element and disposed at least in the region of the sliding surface. The contact shoe is preferably made of a different material than the hydraulic piston. Preferably, the contact shoe completely surrounds the sliding element. The material of the hydraulic piston can be selected regardless of the sliding characteristics by using the contact shoe. The material of the contact shoe is advantageously chosen in this way to ensure a good sliding fit between the material of the sliding surface and the contact shoe. This further reduces wear, thereby improving service life and efficiency.

[0016] In a preferred embodiment of the invention, the contact boot is made of a plastic material. This allows for the easy production of any shape. Such a contact boot can be constructed easily and economically. Furthermore, plastics are lightweight and inexpensive. A wide variety of plastics with specific properties are available, ensuring that a suitable plastic can be found for the intended application. In particular, polyoxymethylene (POM), polyetheretherketone (PEEK), and polyamide (PA) are conceivable materials. With the aid of two-component plastics, the advantageous tribological properties of one material can be combined with the advantageous strength properties of another.

[0017] In another preferred embodiment of the invention, the sliding surface of the contact surface and / or recess has a wave-like structure. The wave-like structure preferably extends over the entire radial height of the contact and / or sliding surface. This wave-like structure forms a continuous orientation of the molded part, for example, in a parabolic form, thereby preventing eddies of lubricant in the region of the molded part. This prevents the lubricant film from tearing due to such eddies. This ensures the formation of a permanent lubricant film, thereby reducing wear. Furthermore, sufficient lubricant deposition is ensured even if the axial length and / or translational path of the sliding element is large.

[0018] The height of the waveform structure is limited downwards by the roughness of the contact and sliding surfaces. The upper limit of the waveform structure depends on the specific implementation of the waveform and the axial length of the sliding element to which the waveform is applied. This design can be accomplished using fluid / tribology simulations.

[0019] The waveform structure preferably has at least one wave with a height between 5 μm and 500 μm. This wave is particularly preferably between 10 μm and 100 μm in height. It has been found that a wave of this height is sufficiently effective to form lubricant deposits. Additionally, this height ensures that the lubricant does not separate or swirl due to turbulent flow. Such a height thus ensures the aforementioned advantages. In particular, multiple waves can be formed instead of a single wave, thereby forming lubricant deposits between the waves or in the troughs.

[0020] In an alternative embodiment, the sliding surface is formed by an insert that is inserted into the recess. This allows for the simple application of the micro-molded part to the sliding surface. The insert is preferably made of a plastic material. The aforementioned advantages are thus achieved by molding the sliding surface.

[0021] The objective upon which this invention is based is additionally addressed by a method for manufacturing such an electromechanical braking pressure generator. This method includes the step of forming a recess with a sliding surface extending in the axial direction, wherein the recess, together with a sliding element, forms an anti-torsion portion. The method is characterized by forming microformed parts on the contact surface of the sliding element and / or the sliding surface of the recess. This construction of the microformed parts substantially achieves the aforementioned advantages.

[0022] The contact shoe is preferably applied to the sliding element. The microformed part is preferably constructed on the contact shoe by injection molding. Thus, the microformed part is formed on the injection molding tool. The advantage of this is that no further processing steps are required to produce the microformed part.

[0023] In another advantageous embodiment, the micro-molded part is formed by post-processing the contact surface. Therefore, the micro-molded part is formed through further processing steps. Thus, the production process does not require significant changes. Similarly, for example, the injection mold does not need to be changed.

[0024] According to a suitable implementation, the micro-formed part is formed by the elastic deformation of the contact shoe when it is applied to the sliding element. The sliding element here has a slightly larger external dimension in a predetermined direction. Consequently, the contact shoe expands in a specific direction, minimizing the change in its outer contour. This eliminates the need for subsequent processing.

[0025] The present invention also describes a vehicle having an electromechanical brake pressure generator for a hydraulic braking system. Using such a vehicle, the advantages mentioned for the electromechanical brake pressure generator can be achieved. In a preferred embodiment, the vehicle can be an automated vehicle or a fully autonomous vehicle. Attached Figure Description

[0026] Embodiments of the present invention are shown in the accompanying drawings and explained in more detail in the following description.

[0027] Figure 1 A schematic diagram of a hydraulic braking system for a vehicle with an electromechanical brake pressure generator is shown.

[0028] Figure 2 A longitudinal cross-sectional view of an embodiment of the threaded drive device of the electromechanical braking pressure generator according to the present invention is shown.

[0029] Figure 3 A perspective view of an embodiment of the contact shoe is shown, and

[0030] Figure 4 A top view of an embodiment of a sliding element with a contact shoe is shown. Detailed Implementation

[0031] Figure 1 The diagram shows a schematic of a hydraulic braking system 10 for a vehicle, including an electromechanical brake pressure generator 14. The hydraulic braking system 10 includes the electromechanical brake pressure generator 14. The brake pressure generator 14 includes a piston / cylinder unit 18, which is supplied with brake fluid via a brake fluid reservoir 22.

[0032] The piston / cylinder unit 18 can be controlled by the brake pedal 26 operated by the driver, and the resulting brake pedal travel is measured by the pedal travel sensor 30 and relayed to the controller 34. Although Figure 1 The brake force amplifier is shown in principle, but what is important here is that the brake pedal travel is measured by the pedal travel sensor 30. Braking pressure can also be generated without brake pedal travel, allowing the vehicle to brake even in autonomous driving mode.

[0033] Based on the measured brake pedal travel, controller 34 generates a control signal for the electric motor 38 of brake pressure generator 14. The electric motor is connected to a transmission (not shown) of brake pressure generator 14, and within the scope of the decoupled system, the electric motor 38 amplifies the braking force input from brake pedal 26 according to the control signal. For this purpose, according to the operation of brake pedal 26, the threaded drive device 40 arranged in brake pressure generator 14 is controlled by electric motor 38, causing the rotational motion of electric motor 38 to be converted into translational motion.

[0034] By operating the brake pedal 26, the brake fluid present in the piston / cylinder unit 18 is pressurized by the brake pressure generator 14. This brake pressure is transmitted via the brake line 42 to the brake hydraulic unit 46. The brake hydraulic unit 46 is shown here only as a box, which is formed by various valves and other components to construct, for example, an electronic stability program (ESP). The brake hydraulic unit 46 is additionally connected to at least one wheel brake 50, so that braking force can be applied to the wheel brake 50 by corresponding switching of the valves.

[0035] Figure 2 A longitudinal sectional view of an embodiment of the electromechanical brake pressure generator 14 and its threaded drive device 40 according to the invention is shown. The threaded drive device 40 includes a housing 60 forming a canister-shaped hydraulic cylinder 64. In this embodiment, the housing 60 is made of metal. Additionally, the threaded drive device 40 includes a spindle 68 that can be driven... Figure 1 The motor 38 shown drives the spindle 68 to rotate.

[0036] A spindle nut 76 is disposed on a thread 72 of a spindle 68, and the spindle nut engages with the thread 72 of the spindle 68. The spindle nut forms a one-piece hydraulic piston 80, coaxially arranged with the spindle nut 76. Additionally, two sliding elements 84 are constructed one-piece with the spindle nut 76, and the two sliding elements interact with an axial recess 88 in the housing 60 and form an anti-torsion portion. Above the centerline 90, an embodiment is shown in which the sliding element 84 has a contact shoe 92, the contact shoe being disposed on the outer side and passing through a contact surface 96 ( Figure 3 (As shown) the sliding element 84 slides in contact with the sliding surface 100 constructed in the recess 88. An embodiment of the sliding element 84 without the contact shoe 92 is shown below the center line 90. The contact surface 96 is here constructed on the sliding element 84.

[0037] The spindle nut 76 is secured by anti-torsion portions 84 and 88 to prevent torsion. The axial length of the sliding element 84 is significantly smaller than the axial length of the recess 88. Therefore, the spindle nut 76 can move axially by rotating the spindle 68.

[0038] Figure 3 A perspective view of an embodiment of the contact shoe is shown. The contact surface 96 of the contact shoe 92, which has a microform 104, is particularly shown in the figure. Since the microform 104 is constructed only in the μm range, it is not visible on the contact surface 96 itself. A coordinate system is shown with respect to the contact surface 96, having a zero point at the lower left corner of the contact surface 96. The X-axis extends here along the axial direction of movement of the sliding element 84 in the recess 88. The Y-axis represents a direction orthogonal to the direction of movement and corresponding to the radial direction of the spindle nut 76. The height of the microform 104 is indicated by the Z-axis.

[0039] Below the contact shoe 92, two embodiments of the orientation of the microformed part 104 on the contact surface 96 are exemplarily shown. It can be seen here that the microformed part 104 has a wave-like structure. In the left figure, only a single wave 108 is formed. At the crest 112 of the wave, the gap between the sliding surface 100 of the recess 88 and the contact shoe 92 is thereby reduced. As the sliding element 84 moves axially, lubricant thus accumulates more quickly between the contact shoe 92 and the sliding surface 100 in front of the crest 112. Thus, after only a brief movement of the sliding element 84, a lubricant flow is already provided in the region of the crest 112, thereby overcoming solid friction between the contact shoe 92 and the sliding surface 100. This significantly reduces friction and wear.

[0040] Figure 3 The right figure shows a microformed part 104 having, for example, three waves 108, constructed on the contact surface 96 of the contact shoe 92. Essentially the same effect as in the left figure is achieved here. Additionally, a lubricant reservoir is provided between the waves 108, which allows for the storage of lubricant and rapid overcoming of solid friction.

[0041] In embodiments not shown here, Figure 3 The micro-molded part 104 shown can also be applied over the entire axial length of the sliding surface 100 constructed in the recess 88. In other words, a large number of waves 108 are applied to the sliding surface 100. This achieves the same effect as the contact surface 96, thereby reducing wear on the anti-torsion portions 84, 88 and extending their service life.

[0042] Figure 4 A top view of an embodiment of a sliding element 84 with a contact shoe 92 is shown. In this embodiment, the sliding element 84 has raised regions 116 facing the two contact surfaces 96, which are shown here in an exaggerated manner. The contact shoe 92, made of a soft material, is applied to the sliding element 84. The contact shoe 92 here has a shape with smooth contact surfaces 96. Due to the soft material, the application of the contact shoe 92 does not result in the direct formation of the raised shape due to the compression of the soft material in the raised regions 116. However, under the load of the sliding surface 100, this results in a reduction in the compression in the raised regions 116 and the effect of the contact surfaces 96 being shown by exaggerated dashed lines in the figure. This results in a micro-molded part 104 with wavy lines, thereby achieving the aforementioned advantages.

Claims

1. An electromechanical brake pressure generator (14) for a hydraulic braking system (10) of a vehicle, comprising: At least one thread drive device (40) is used to convert the rotational motion on the drive side into translational motion; A piston / cylinder unit (18) operable by a threaded drive (40) for generating braking pressure, the piston / cylinder unit comprising a hydraulic piston (80), wherein, The threaded drive device (40) includes a spindle (68) and a spindle nut (76), the spindle and the spindle nut interacting via a thread (72); and An electric drive (38) enables the spindle (68) and the spindle nut (76) to rotate relative to each other. Furthermore, the hydraulic piston (80) is housed in the hydraulic cylinder (64) of the piston / cylinder unit (18), the hydraulic cylinder forming anti-torsion portions (84, 88), wherein the anti-torsion portions (84, 88) are formed by a recess (88) and a sliding element (84) extending into the recess (88), such that the hydraulic piston (80) is fixed to prevent torsion and can move axially by the rotation of the main shaft (68), the recess extending in the axial direction and forming a sliding surface (100). Its features are, The contact surface (96) of the sliding surface (100) and / or the sliding element (84) that interacts with the sliding surface (100) has a microformed part (104), the forming direction of which is configured to be orthogonal to the movement of the hydraulic piston (80). The micro-molded part (104) has a waveform structure having multiple waves (108), and a lubricant storage section is provided between the waves (108).

2. The electromechanical braking pressure generator (14) according to claim 1, characterized in that, The sliding element (84) has a contact shoe (92) forming the contact surface (96), the contact shoe being applied to the sliding element (84) and being disposed at least in the region of the sliding surface (100).

3. The electromechanical braking pressure generator (14) according to claim 2, characterized in that, The contact boot (92) is made of plastic material.

4. The electromechanical braking pressure generator (14) according to claim 1 or 2, characterized in that, The contact surface (96) and / or sliding surface (100) of the recess (88) have a wave-like structure.

5. The electromechanical braking pressure generator (14) according to claim 4, characterized in that, The waveform structure has at least one wave (108) with a height between 5 μm and 500 μm.

6. A method for manufacturing an electromechanical brake pressure generator (14) according to any one of the preceding claims, wherein the method comprises the following steps: A recess (88) with a sliding surface (100) extending in the axial direction is formed, wherein the recess (88) and the sliding element (84) together form an anti-torsion portion (84, 88). Its features are, The micro-shaped part (104) is constructed on the contact surface (96) of the sliding element (84) and / or the sliding surface (100) of the recess (88).

7. The method according to claim 6, characterized in that, The contact shoe (92) is applied to the sliding element (84).

8. The method according to claim 7, characterized in that, The micro-molded part (104) is constructed on the contact shoe (92) by injection molding.

9. The method according to any one of claims 6 to 8, characterized in that, The micro-shaped part (104) is formed by post-processing the contact surface (96).

10. The method according to claim 7 or 8, characterized in that, The micro-shaped part (104) is formed by the elastic deformation of the contact shoe (92) when the contact shoe (92) is applied to the sliding element (84).

11. A vehicle, including an electromechanical brake pressure generator (14) according to any one of claims 1 to 5 for a hydraulic braking system (10).

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