Electromechanically driven brake pressure generator

Abstract

The invention relates to an electromechanically drivable brake pressure generator for a hydraulic brake system of a vehicle, the brake pressure generator comprising a spindle gear unit (38) for converting a drive-side rotational motion (a) into a translational motion (b) for piston actuation of a hydraulic piston / cylinder unit (34), wherein a planetary gear mechanism (22) connected to the electric drive motor (18) is arranged between the spindle gear unit (38) and the electric drive motor (18), and a spur gear (42) is fixed to a planetary gear carrier shaft (78) on the output side of the planetary gear mechanism, via which the spindle gear unit (38) can be driven. The spur gear (42) is supported by a first bearing (L1) arranged between the spur gear (42) and the planetary gear mechanism (22) and by a second bearing (L2) arranged on an axial side of the spur gear (42) opposite the first bearing (L1).

Description

Technical Field

[0001] The present invention relates to an electromechanically drivable brake pressure generator for a hydraulic brake system of a vehicle, comprising a spindle drive unit for converting a drive-side rotational motion into a translational motion for piston actuation of a hydraulic piston / cylinder unit. A planetary gear mechanism connected to the electric drive motor is arranged between the spindle drive unit and the electric drive motor, a spur gear being fastened to a planetary carrier shaft on the output side of the planetary gear mechanism, via which the spindle drive unit can be driven. The present invention also relates to a vehicle comprising such an electromechanically drivable brake pressure generator. Background Art

[0002] For future drive concepts of motor vehicles, alternative brake pressure buildup devices are required, since negative pressure is no longer used to operate conventional vacuum brake pressure boosters. For this purpose, electromechanical brake pressure generators of interest have been developed.

[0003] In the case of an electromechanical brake pressure generator of the type of interest here, the braking force is generated at the piston / cylinder unit by means of an electric motor or other suitable electric drive. Such a brake pressure generator can be used not only for providing assistance but also for independently generating the brake actuation force in so-called brake-by-wire systems. Therefore, electromechanical brake pressure generators are particularly advantageous for automated driving.

[0004] According to the generally known prior art regarding such electromechanical brake boosters, the pedal travel manually applied when the brake pedal is actuated is measured by an electronic pedal travel sensor and transmitted to an electronic control unit. The electronic control unit uses this information to calculate the corresponding control signal for the electric drive motor. The motor torque is converted into a supporting force for the driver via a multi-stage gear train. The force provided by this booster is converted into hydraulic pressure for braking in a hydraulic piston / cylinder unit. The electromechanical brake pressure generator provides a braking feel similar to that of a conventional vacuum brake booster. This braking feel can then be adapted to the vehicle's specific market characteristics via software using the electronic control unit.

[0005] WO 2017 / 045804 A1 discloses an electromechanical brake pressure generator of this type, which includes an electric drive motor that is operatively connected to a spindle drive unit via a multi-stage spur gear mechanism such that rotation of the electric drive motor causes a translational movement of a spindle of the spindle drive unit for actuating a master brake cylinder. Summary of the Invention

[0006] The object of the present invention is to specify an electromechanically drivable brake pressure generator which is distinguished by low noise generation.

[0007] This object is achieved by an electromechanically drivable brake pressure generator according to the present invention for a hydraulic brake system of a vehicle. Advantageous refinements of the present invention include: the housing is fixed to a valve housing, in which the electric drive motor is accommodated; the housing is designed as a deep-drawn part made of sheet metal; the diameter of the first bearing is greater than or equal to the outer diameter of the spur gear; the diameter of the second bearing is smaller than the outer diameter of the spur gear; the spur gear is made of plastic material; the first bearing and / or the second bearing directly abuts the planetary carrier shaft, so that the spur gear is supported by the planetary carrier shaft. The present invention also describes a vehicle having a hydraulic brake system that includes an electromechanical brake pressure generator according to the present invention.

[0008] The invention includes the technical teaching that the spur gear is supported by a first bearing arranged between the spur gear and the planetary gear and a second bearing arranged on the axial side of the spur gear opposite the first bearing.

[0009] The spur gear is thus supported on both sides. This prevents tilting of the planetary carrier shaft due to loads on the spur gear. Due to this tilting, the planet gears in the ring gear often also tilt. This leads to increased noise generation in the planetary gear train, as the teeth no longer fit perfectly into the ring gear. By supporting the spur gear on both sides, this tilting and the associated noise generation in the planetary gear train can be significantly reduced.

[0010] In a preferred embodiment of the present invention, the planetary gear and the spur gear are arranged in a common housing, with the first and second bearings supporting the spur gear relative to the housing. This eliminates the need for a separate housing for the bearings. The installation of the common housing requires only one additional step, enabling cost-effective production of such an electromechanical brake booster.

[0011] In another preferred embodiment of the present invention, the housing is fixed to the valve housing, in which the electric drive motor is accommodated. In order to be able to absorb the bearing forces via the housing, the housing must be fixed. By fixing it to the valve housing, no additional fixing options are required. The electric drive that drives the planetary gear mechanism is also fixed to the valve housing, so that the electric drive, planetary gear mechanism, and bearings share a common reference point. This prevents tilting due to relative movement at different reference points, further improving noise generation.

[0012] The housing is preferably designed as a deep-drawn part made of sheet metal. The housing is thus manufactured using a deep-drawing process. This deep-drawing process has the advantage that the components produced using it can be manufactured very cost-effectively compared to other processes, such as cutting processes. This allows for rapid implementation, particularly during mass production. The sheet metal also provides sufficient stability for the support of the spur gear.

[0013] In an advantageous refinement, the housing has a housing recess in the engagement region of the spur gear. The housing recess, provided only in the engagement region, ensures sufficient stability for the bearing structure and, on the other hand, ensures torque transmission of the spur gear. This provides a one-piece housing that also surrounds the spur gear and also further ensures its functionality.

[0014] Advantageously, the diameter of the first bearing is greater than or equal to the outer diameter of the spur gear. The bearing diameter here refers to the outer diameter of the bearing. This has the advantage that, due to the arrangement of the components, at least the first housing can be installed from the side of the planetary carrier shaft after the spur gear has been installed. This simplifies the installation of the housing. Likewise, the bearing can rest directly on the housing, that is, without intermediate components.

[0015] In another advantageous embodiment, the diameter of the second bearing is smaller than the outer diameter of the spur gear. The bearing diameter here refers to its outer diameter. This allows for the attachment of at least one housing, which covers the second bearing, the spur gear, and advantageously the remaining components, to the planetary carrier shaft. This simplifies assembly.

[0016] The spur gear is preferably made of a plastic material. Plastic materials have the advantage of being lightweight and easily manufactured using injection molding. They also have low material costs. Plastics with good tribological properties can also be selected, allowing the use of self-lubricating plastics, thus eliminating the need for additional lubricants. The spur gear can be made of PEEK (polyetheretherketone), for example. Accordingly, such materials can provide an electromechanically drivable brake pressure generator that can be manufactured economically.

[0017] According to an advantageous embodiment, the first and / or second bearing bears directly against the planet carrier shaft, so that the spur gear is supported by the planet carrier shaft. In contrast to a bearing structure in which the bearing bears against a step on the spur gear, the spur gear can be designed independently of the bearings, so that it can be designed in an optimized manner with respect to its actual function. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Embodiments of the present invention are shown in the drawings and explained in detail in the following description.

[0019] Figure 1 A schematic diagram of an exemplary embodiment of a drive train for an electromechanical brake pressure generator according to the present invention is shown; and

[0020] FIG2 shows a sectional view of a planetary gear train with spur gears according to the prior art; and

[0021] Figure 3 A sectional view of an exemplary embodiment of a planetary gear according to the invention with spur gears is shown. DETAILED DESCRIPTION

[0022] exist Figure 1 shows a schematic diagram of an exemplary embodiment of a drive train 14 for an electromechanical brake pressure generator according to the present invention. Drive train 14 includes an electric drive motor 18, which can generate a rotational motion a. Electric drive motor 18 is mechanically connected to the input side of a planetary gear mechanism 22. In this exemplary embodiment, planetary gear mechanism 22 is positioned coaxially with a drive motor shaft 26. Planetary gear mechanism 22 is also arranged on a valve housing 28 of the brake pressure generator.

[0023] The planetary gear mechanism 22 converts the drive speed of the electric drive motor 18 to a slower speed. The planetary gear mechanism 22 is mechanically connected to a hydraulic module 30 on the output side. The hydraulic module 30 can include a piston / cylinder unit 34 that generates brake pressure via an axial translational movement b of a spindle drive unit 38. In the exemplary embodiment shown, the drive train 14 is arranged in a biaxial configuration. This means that the hydraulic module 30 is arranged parallel to the drive motor shaft 26.

[0024] FIG2 shows a cross-sectional view of a planetary gear 22 having a spur gear 42 according to the prior art. The planetary gear 22 includes a sun gear shaft 46 on which a sun gear 50 is arranged. The sun gear shaft 46 is driven by an electric drive motor 18 arranged in a valve housing 28. The sun gear 50 engages with a plurality of planetary gears 54 of the planetary gear 22. The planetary gears 54 and the sun gear 50 are arranged in a ring gear 62, which is arranged in a rotationally fixed manner in a housing 58 of the planetary gear 22, so that the planetary gears 54 interact with an internal toothing 66 of the ring gear 62.

[0025] The planetary gear mechanism 22 also includes a planetary carrier 70 having planetary shafts 74 on which the planetary gears 54 are rotatably supported. The planetary carrier 70 is rotatably supported relative to the housing 58 via bearings L, so that it can rotate relative to the housing with the rotational movement of the planetary gears 54. The planetary carrier 70 also includes a planetary carrier shaft 78, at the end of which the spur gear 42 is fixedly connected. The spur gear 42 is engaged with a gear 82 of the hydraulic module 30.

[0026] exist Figure 3 shows a cross-sectional view of an exemplary embodiment of a planetary gear 22 according to the present invention having a spur gear 42. This figure shows that, in addition to the first bearing L1 between the spur gear 42 and the planetary gear 22, a second bearing L2 is arranged on the planetary carrier shaft 78. The second bearing L2 is arranged on the side of the spur gear 42 axially opposite the first bearing L1. In contrast to the housing 58 shown in FIG. 2 , this housing 58 also surrounds the spur gear 42 and the second bearing L2. This allows the planetary carrier shaft 78 to be supported relative to the housing 58. The housing 58, which is constructed from sheet metal, is fixedly connected to the valve housing 28.

[0027] The housing 58 is formed by means of a deep drawing process. As can be seen in the figure, the diameter d of the first bearing L1 is L1 Larger than the outer diameter d of the cylindrical gear S The diameter d of the second bearing L2 is L2 is smaller than the diameter d of the first bearing L1 L1 and is smaller than the outer diameter d of the cylindrical gear S This allows the deep drawing process of the housing 58 to be completely completed and assembled. To ensure the engagement of the spur gear 42 with the gear 82 of the hydraulic module 30, the housing 58 has a housing recess 86 in the engagement area. This housing recess 86 is only as high as the spur gear 42, so that the first and second bearings L1, L2 are in contact with the housing 58.

[0028] In this figure, a part of the spindle drive unit 38 is additionally shown, which has a spindle 90 and a spindle nut 94 which engage with one another.

Claims

1. An electromechanically drivable brake pressure generator for a hydraulic brake system of a vehicle, comprising a spindle drive unit (38) for converting a drive-side rotational movement (a) into a translational movement (b) for piston actuation of a hydraulic piston / cylinder unit (34), wherein: A planetary gear transmission mechanism (22) connected to the electric drive motor (18) is arranged between the screw transmission unit (38) and the electric drive motor (18), and a cylindrical gear (42) is fixed to the planetary gear carrier shaft (78) on the output side of the planetary gear transmission mechanism, and the screw transmission unit (38) can be driven by the cylindrical gear. It is characterized by: The spur gear (42) is supported by a first bearing (L1) arranged between the spur gear (42) and the planetary gear mechanism (22) and by a second bearing (L2) arranged on an axial side of the spur gear (42) opposite the first bearing (L1), wherein the planetary gear mechanism (22) and the spur gear (42) are arranged in a common housing (58), and the first and second bearings (L1, L2) support the spur gear (42) relative to the housing, wherein the housing (58) has a housing recess (86) in the engagement region of the spur gear (42), which has only the height of the spur gear (42), so that the first and second bearings (L1, L2) are in contact with the housing (58).

2. The electromechanically drivable brake pressure generator according to claim 1, characterized in that The housing (58) is fastened to a valve housing (28) in which the electric drive motor (18) is accommodated.

3. The electromechanically drivable brake pressure generator according to claim 1 or 2, characterized in that The housing (58) is designed as a deep-drawn part made of sheet metal.

4. The electromechanically drivable brake pressure generator according to claim 1 or 2, characterized in that The diameter (d L1 ) is greater than or equal to the outer diameter of the cylindrical gear (d S ).

5. The electromechanically drivable brake pressure generator according to claim 1 or 2, characterized in that The diameter (d L2 ) is smaller than the outer diameter of the cylindrical gear (d S ).

6. The electromechanically drivable brake pressure generator according to claim 1 or 2, characterized in that The spur gear (42) is made of plastic material.

7. The electromechanically drivable brake pressure generator according to claim 1 or 2, characterized in that The first bearing (L1) and / or the second bearing (L2) directly abut against the planetary carrier shaft (78), so that the spur gear (42) is supported by the planetary carrier shaft (78).

8. Vehicle comprising an electromechanical brake pressure generator for a hydraulic brake system according to any one of the preceding claims.

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