Electromechanically actuable brake pressure generator

Abstract

The present invention relates to an electromechanically drivable brake pressure generator for a vehicle hydraulic brake system, which has a spindle transmission unit (38) that converts a drive-side rotational movement (a) into a translational movement (b) for operating a piston of a hydraulic piston / cylinder unit (34), in which a planetary gear set (22) connected to an electric drive motor (18) is arranged between the spindle transmission unit (38) and the electric drive motor (18), and a spur gear (42) is fixed to a planetary gear support shaft (78) on the driven side of the planetary gear set (22) so that the spindle transmission unit (38) can be driven via the spur gear (42). In this case, the spur gear (42) is supported via a first bearing (L1) arranged between the spur gear (42) and the planetary gear device (22) and a second bearing (L2) arranged on the side of the spur gear (42) axially opposite the first bearing (L1).

Description

[Technical Field]

[0001] The present invention relates to an electromechanically actuable brake pressure generator for a vehicle hydraulic brake system, which has a spindle transmission unit that converts a rotary motion on the drive side into a translational motion for operating a piston of a hydraulic piston-cylinder unit, in which a planetary gear set connected to the electric drive motor is arranged between the spindle transmission unit and the electric drive motor, and a spur gear is fixed to a planet gear carrier shaft on the driven side of the planetary gear set, via which the spindle transmission unit can be driven. The present invention also relates to a vehicle having such an electromechanically actuable brake pressure generator.

[0002] For future drive concepts of motor vehicles, selective brake pressure generators are required, since vacuum is no longer available to drive conventional vacuum brake boosters. For this reason, related electromechanical brake pressure generators are being developed.

[0003] In the related electromechanically actuated brake pressure generators, the braking force is generated in a piston / cylinder unit by means of an electric motor or other suitable electric drive. Such brake pressure generators are used not only to provide auxiliary force but also to generate the braking force independently in so-called brake-by-wire systems. Therefore, electromechanical brake pressure generators are particularly advantageous for autonomous driving. [Background technology]

[0004] According to the generally known prior art of this type of electromechanical brake pressure generator, when the brake pedal is operated, the manually applied pedal stroke is measured via an electronic pedal stroke sensor and transmitted to an electronic control unit. From this, the electronic control unit calculates a corresponding control signal for the electric drive motor. The motor torque is converted into an assist force for the driver via a multi-stage gear transmission. The power provided by this amplifier is converted into hydraulic pressure for braking by a hydraulic piston / cylinder unit. In this case, the electromechanical brake pressure generator provides a brake feel comparable to that of a conventional vacuum brake booster. This brake feel can be adapted to the manufacturer-specific characteristics of the vehicle via the electronic control unit by software.

[0005] An electromechanical brake pressure generator of the type mentioned at the outset is derived from DE 10 04 22 512. The brake pressure generator has an electric drive motor which is operatively connected to a spindle transmission unit via a multi-stage spur gear in such a way that rotation of the electric drive motor causes a translational movement of the spindle of the spindle transmission unit for operating a master brake cylinder. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2017 / 045804 Brochure Summary of the Invention [Problem to be solved by the invention]

[0007] SUMMARY OF THE INVENTION It is an object of the present invention to provide an electromechanically actuable brake pressure generator which is distinguished by low noise generation. [Means for solving the problem]

[0008] This problem is solved by an electromechanically drivable brake pressure generator for a hydraulic braking system of a vehicle, in combination with the preamble and characterizing features of claim 1. The subsequent dependent claims describe preferred embodiments of the invention. Claim 10 recites a vehicle having a hydraulic braking system with an electromechanical brake pressure generator according to the invention.

[0009] The present invention includes a technical theory in which the spur gear is supported via a first bearing arranged between the spur gear and the planetary gear device, and a second bearing arranged on the side of the spur gear axially opposite the first bearing.

[0010] The spur gear is therefore supported on both sides. This prevents tilting of the planet gear support axis caused by loads on the spur gear. Such tilting would normally cause the planet gears in the ring gear to tilt as well. This would result in greater noise generation in the planetary gear set because the teeth would no longer mesh perfectly with the ring gear. By supporting the spur gear on both sides, such tilting and the resulting noise generation in the planetary gear set can be significantly reduced.

[0011] According to 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 facing the housing. This eliminates the need to provide an additional separate housing for the bearings. Furthermore, since assembling the common housing requires only one step, such an electromechanical brake booster can be manufactured economically.

[0012] According to another preferred embodiment of the present invention, a housing is fixed to the valve housing, and an electric drive motor is accommodated within the valve housing. The housing must be fixed so that support forces can be absorbed via the housing. By fixing it to the valve housing, it is not necessary to provide additional fixing possibilities. Furthermore, since the electric drive that drives the planetary gear unit is also fixed to the valve housing, the electric drive unit, the planetary gear unit, and the bearing have the same reference point. This avoids tilting due to relative movements at different reference points, further improving noise generation.

[0013] In a preferred embodiment, the housing is formed as a deep-drawn part from sheet metal. Therefore, the housing is manufactured using a deep-drawing process. This deep-drawing process has the advantage that the part produced thereby can be manufactured very inexpensively compared to other methods, such as cutting. This can be done quickly, especially in mass production. Furthermore, the sheet metal provides sufficient dimensional stability for supporting the spur gear.

[0014] In a preferred embodiment, the housing has a housing recess in the meshing area of ​​the spur gear. The housing recess provided only in the meshing area ensures sufficient dimensional stability for the bearing on the one hand and ensures torque transmission of the spur gear on the other hand. This allows for a one-piece housing to be provided that contains the spur gear and also ensures its function in the same way.

[0015] In a preferred embodiment, the diameter of the first bearing is greater than or equal to the outer diameter of the spur gear. In this case, the bearing diameter is understood to mean the outer diameter of the bearing. This has the advantage that such an arrangement of components allows assembly of at least the first housing to be carried out from one side of the planet gear support shaft after assembly of the spur gear. This simplifies assembly of the housing. Likewise, the bearing can be directly abutted against the housing, i.e., without an intermediate part.

[0016] According to another preferred embodiment, the diameter of the second bearing is smaller than the outer diameter of the spur gear. In this case, the bearing diameter is understood to mean the outer diameter of the bearing. This allows at least one housing, which covers the second bearing, the spur gear and other components in a suitable manner, to be mounted from one side of the planet gear support shaft. This simplifies assembly.

[0017] The spur gear is preferably made of a plastic material. Plastic materials have the advantage that they are light in weight and can be easily manufactured using injection molding. Plastic materials also have low material costs. Furthermore, plastics can be selected that have good tribological properties, allowing the use of self-lubricating plastics, thereby eliminating the need for additional lubricants. In this case, the spur gear can be made, for example, from PEEK (Polyetheretherketone). Accordingly, such materials allow the production of economically manufacturable, electromechanically actuated brake pressure generators.

[0018] According to a preferred embodiment, the first bearing and / or the second bearing rest directly on the planet gear support shaft, thereby supporting the spur gear via the planet gear support shaft. Unlike support types in which the bearing rests on one stage of the spur gear, the spur gear can be designed independently of the bearing, and therefore can be optimized for its intended function. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram of an embodiment of a power transmission mechanism for an electromechanical brake pressure generator according to the present invention; [Figure 2] 1 is a cross-sectional view of a planetary gear unit having a spur gear according to the prior art; [Figure 3] 1 is a cross-sectional view of an embodiment of a planetary gear set having spur gears according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of the invention is shown in the drawings and is explained in more detail below.

[0021] 1 shows a schematic diagram of an embodiment of a power transmission 14 of an electromechanical brake pressure generator according to the invention. The power transmission 14 has an electric drive motor 18, via which a rotary movement a can be generated. The electric drive motor 18 is mechanically connected to the input side of a planetary gear set 22. In this embodiment, the planetary gear set 22 is positioned coaxially with respect to a drive motor axis 26. The planetary gear set 22 is additionally arranged in a valve housing 28 of the brake pressure generator.

[0022] The planetary gear 22 converts the drive speed of the electric drive motor 18 into a slower rotation. On its output side, the planetary gear 22 is mechanically connected to a hydraulic module 30. In this case, the hydraulic module 30 comprises a piston / cylinder unit 34, which generates brake pressure via the axial translational movement b of a spindle transmission unit 38. The power transmission 14 shown in this exemplary embodiment is arranged biaxially, meaning that the hydraulic module 30 is arranged parallel to the drive motor axis 26.

[0023] 2 shows a cross-sectional view of a planetary gear set 22 having a spur gear 42 according to the prior art. The planetary gear set 22 has a sun gear shaft 46 on which a sun gear 50 is arranged. The sun gear shaft 46 is driven via an electric drive motor 18 disposed within the valve housing 28. The sun gear 50 meshes with a plurality of planet gears 54 of the planetary gear set 22. The planet gears 54 and the sun gear 50 are disposed within a ring gear 62 that is non-rotatably mounted within a housing 58 of the planetary gear set 22, so that the planet gears 54 cooperate with an internal toothing 66 of the ring gear 62.

[0024] The planetary gear set 22 additionally comprises a planet gear support 70 having a planet gear shaft 74, on which the planet gears 54 are rotatably supported. The planet gear support 70 is rotatably supported relative to the housing 58 via a bearing L, so that the planet gear support 70 can rotate relative to the housing as the planet gears 54 rotate. The planet gear support 70 additionally has a planet gear support shaft 78, at the end of which the spur gear 42 is firmly connected. In this case, the spur gear 42 meshes with a gear 82 of the hydraulic module 30.

[0025] A cross-sectional view of an embodiment of the planetary gear unit 22 according to the invention, including the spur gear 42, is shown in FIG. 3. It can be seen in this drawing that, in addition to the first bearing L1 between the spur gear 42 and the planetary gear unit 22, a second bearing L2 is arranged on the planetary gear carrier shaft 78. In this case, the second bearing L2 is arranged on the side of the spur gear 42 axially opposite the first bearing L1. Unlike the housing 58 shown in FIG. 2, this housing 58 encloses both the spur gear 42 and the second bearing L2. This allows the planetary gear carrier shaft 78 to be supported relative to the housing 58. In this case, the housing 58, which is made of sheet metal, is firmly connected to the valve housing 28.

[0026] In this case, the housing 58 is formed by a deep drawing process. As can be seen in the drawing, the diameter d L1 is the outer diameter of the spur gear d S On the other hand, the diameter d of the second bearing L2 is L2 is the diameter d of the first bearing L1 L1 smaller than the spur gear outer diameter d S 4. Only in this way is deep drawing and assembly of the housing 58 possible. To ensure the meshing of the gear 82 of the hydraulic module 30 with the spur gear 42, the housing 58 has a housing recess 86 in the meshing area. In this case, the housing recess 86 only has the height of the spur gear 42, so that the first bearing L1 and the second bearing L2 are in contact with the housing 58 in the same way.

[0027] Additionally shown in the drawing is a portion of the spindle transmission unit 38, which includes a spindle 90 and a spindle nut 94 that mesh with each other. [Explanation of symbols]

[0028] 14 Power transmission mechanism 18 Electric drive motor 22 Planetary gear unit 26 Drive motor axis 28 Valve housing 30 Hydraulic Module 34 Piston / cylinder unit 38 Spindle transmission unit 42 Spur gear 46 Sun gear shaft 50 Sun Gear 54 Planetary gear 58 Housing 62 Ring gear 66 Inner dentition 70 Planetary gear support 74 Planetary gear shaft 78 Planetary gear support shaft 82 Gears 86 Housing notch 90 Spindle 94 Spindle nut a Rotational motion b translational motion d L1 Diameter of first bearing L1 d L2 Diameter of the second bearing L2 d S Spur gear outer diameter L1 First bearing L2 Second bearing

Claims

1. An electromechanically drivable brake pressure generator for a hydraulic braking system of a vehicle, comprising a spindle transmission unit (38) for converting a rotary motion (a) on a drive side into a translational motion (b) for operating a piston of a hydraulic piston / cylinder unit (34), wherein a planetary gear set (22) connected to an electric drive motor (18) is arranged between the spindle transmission unit (38) and the electric drive motor (18), and a spur gear (42) is fixed to a planetary gear support shaft (78) on the driven side of the planetary gear set (22) and is capable of driving the spindle transmission unit (38) via the spur gear (42), The spur gear (42) is supported via a first bearing (L1) disposed between the spur gear (42) and the planetary gear device (22) and a second bearing (L2) disposed on the side of the spur gear (42) facing the first bearing (L1) in the axial direction, The planetary gear set (22) and the spur gear (42) are disposed in a common housing (58), and the first and second bearings (L1, L2) in contact with the housing (58) support the spur gear (42); Electromechanically drivable brake pressure generator, characterized in that the housing (58) has a housing notch (86) in the meshing region of the spur gear (42).

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

3. 3. An electromechanically actuable brake pressure generator according to claim 1, wherein the housing (58) is formed as a deep-drawn part from sheet metal.

4. 4. An electromechanically drivable brake pressure generator according to claim 1, wherein the diameter (dL1) of the first bearing (L1) is greater than or equal to the spur gear outer diameter (dS).

5. 5. An electromechanically drivable brake pressure generator according to claim 1, wherein the diameter (dL2) of the second bearing (L2) is smaller than the outer diameter (dS) of the spur gear.

6. 6. An electromechanically drivable brake pressure generator according to claim 1, wherein the spur gear (42) is made of plastic material.

7. 7. An electromechanically drivable brake pressure generator according to claim 1, wherein the first bearing (L1) and / or the second bearing (L2) directly abuts the planet gear carrier shaft (78), whereby the spur gear (42) is supported via the planet gear carrier shaft (78).

8. 8. A vehicle having an electromechanical brake pressure generator for a hydraulic braking system according to any one of claims 1 to 7.

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