Gear with helical tooth part

Abstract

The invention relates to a gear (1), which is formed in one piece from plastic, having: an axis of rotation (R); an outer toothing (10) arranged around the axis of rotation; a centrally arranged receiving opening (40); an intermediate section (30) arranged between the outer toothing (10) and the receiving opening (40); a reinforcing structure arranged in the intermediate section (30), which reinforcing structure has a plurality of openings (32, 33) and reinforcing ribs (34, 35) located between the openings, characterized by the following features: the external toothing (10) is designed as a helical toothing having a helical angle (W) with respect to the axis of rotation (R); at least a portion of the openings (32, 33) follows at least approximately the helical angle (W) of the helical tooth at an opening angle (V). The invention also relates to a method for manufacturing such a gear.

Description

Technical Field

[0001] The invention relates to a gear wheel which is made of plastic in one piece and has the features of the preamble of claim 1 and to a method for producing the gear wheel. Background Art

[0002] Examples of one-piece gear wheels made of plastic are well known from DE 10 2017 2013 83 A1, DE 20 22 2502 U1, US 2002 / 0029648 A1 and US 6,070,484. The gear wheels have an external toothing arranged around a central axis of rotation. The gear wheels have a receiving opening in the middle for receiving an axis or shaft, wherein the middle part connects the receiving opening to the external toothing in a single piece. These known gear wheels have so-called spur gearing, i.e. the teeth of the external toothing are aligned parallel to the axis of rotation of the gear wheel. Such spur gearing has problems with respect to its running smoothness and noise generation.

[0003] Furthermore, so-called multi-component gear wheels are also known, which consist of different materials, for example different plastics, and components.

[0004] In particular, such gears are increasingly being used in auxiliary drives of motor vehicles, such as electric steering, electric seat adjustment or electromechanical brakes. Here, it is absolutely necessary that these gears meet high strength requirements but also have a compact design.

[0005] In general, in motor vehicle construction, and in particular in the implementation of electromechanical brakes, electric steering and electric seat adjustment, there is a need to produce weight-saving and space-saving motor vehicle components. In addition, due to increasing cost pressure, it is necessary to produce such components required for motor vehicles at the lowest possible cost. Summary of the invention

[0006] The present invention is proposed herein.

[0007] The object of the invention is to improve the one-piece gear wheel of the type mentioned at the outset, which is made of plastic, in particular for use in an auxiliary drive of a motor vehicle, in such a way that it takes up less space, can be produced at low cost and still meets the necessary strength requirements. In addition, such a gear wheel should be characterized by low noise generation and high running smoothness.

[0008] This object is achieved with a toothed wheel having the features of claim 1 .

[0009] Improvements of such a gear wheel are the subject matter of the dependent claims.

[0010] Therefore, the one-piece gear made of plastic according to the invention has the following features:

[0011] - axis of rotation (R);

[0012] - an external toothing arranged around the axis of rotation;

[0013] - Centrally arranged storage opening;

[0014] - an intermediate section arranged between the outer toothing and the receiving opening;

[0015] a reinforcing structure arranged in the middle section, the reinforcing structure having a plurality of openings and reinforcing ribs located between the openings;

[0016] - the external toothing is designed as a helical toothing with a helix angle W relative to the axis of rotation;

[0017] At least one section of the openings at an opening angle V at least approximately follows the helix angle W of the helical toothing.

[0018] Compared to gears with spur gearing, such gears are characterized by greater running smoothness and less noise generation due to the helical gearing of the external gearing. Due to the openings arranged likewise obliquely according to the invention and the rib structure formed obliquely in the middle section of the gear, the gear has a high strength.

[0019] Although such a gear can be manufactured in principle, for example by 3D printing, in such a way that the opening angle V of the opening corresponds exactly or at least quite exactly to the helix angle W of the external toothing, a further development of the invention provides that the opening angle V is selected to be smaller or slightly smaller than the helix angle W. In this context, the invention provides in particular that the opening angle satisfies or at least approximately follows the following rule:

[0020] V=arctan(tan(W)×(R) / (d0 / 2))

[0021] Where:

[0022] d0 / 2 = half of the pitch circle diameter of the external toothing (10),

[0023] R = distance of the center of one of the openings (32; 33) from the axis of rotation (R).

[0024] For realizing the gear wheel according to the invention, it has proven to be expedient if the helix angle W is greater than 0 and less than 25 degrees, preferably approximately 10 to 20 degrees, in particular approximately 15 degrees.

[0025] This design of the opening angle also allows the gear according to the invention to be manufactured in a mold by a plastic injection molding method. This mold has a plurality of pins, which are placed at the positions of the mold where the subsequent opening of the gear should be formed. This mold is rotated out of the finished injection molded gear mold during demoulding after the injection molding process of the gear.

[0026] Although the openings can in principle also protrude as through-openings over the entire axial length of the gear wheel, one embodiment of the invention provides that the openings are designed as blind holes, ie each have a bottom.

[0027] These openings can be arranged on the ring in the middle section between the outer toothing and the central receiving opening. However, it is also within the scope of the invention that these openings are arranged on two or more different rings.

[0028] In order to improve the strength of the gear, a revolving reinforcement ring is provided between two circularly arranged open rings.

[0029] If the openings are arranged on two or more circular rings, the openings can be arranged radially aligned with one another or radially offset with respect to one another.

[0030] In another development of the invention, it is provided that the openings are arranged in such a way that one of the openings is arranged below each tooth root of a tooth of the external toothing. The opening at least approximately reaches the tooth root circle of the corresponding tooth of the external toothing. Here, it is also possible that the opening protrudes beyond the tooth root circle into the corresponding tooth.

[0031] It has proven to be useful if the openings have a shape different from a circular ring when viewed in cross section and are in particular elliptical or approximately triangular. Here, the inner walls of the openings themselves can still be rotatably or torsionally configured. This simplifies demoulding the mold when the gear is manufactured in a mold by injection molding.

[0032] The receiving opening of the gear is equipped with a suitable structure for receiving a hub, a shaft or a spindle. If the receiving opening is to receive a spindle, the receiving opening is provided with a spindle nut toothing into which the spindle can be screwed. Such a spindle can, for example, actuate an actuating piston of an electric brake upon rotation of a gear which is an integral part of a transmission assembly of the electric brake.

[0033] In a special embodiment of the invention, the gear is provided with an extension on its axial end side for receiving radial and axial bearings, for example ball bearings. Here, the extension can be formed as a revolving ring with a plurality of evenly distributed and radially outwardly directed ribs, wherein the outer diameter of the extension is smaller than the outer diameter of the external toothing. The above-mentioned ball bearing can be pushed onto the ribs, for example in a clamping manner, as long as the ribs have an outer diameter that is selected to be slightly larger than the receiving ring of the ball bearing.

[0034] If the gear has an extension on the axial end side, it is recommended to provide an orbiting concave depression between the extension and the axial end side of the gear. Such an orbiting concave depression reduces the shear forces when the gear is loaded.

[0035] In another embodiment of the invention, the radially outwardly pointing end face of the tooth of the gear is designed as a step when viewed in the axial direction of the gear. The external toothing can have one or more steps. This stepping of the outwardly facing end face of the tooth, i.e. the tooth tip of the tooth, ensures an increased contact spot of the gear.

[0036] It has proven to be expedient to provide the tooth tip with two steps that are set back from the left and right sides of the middle section, so that the middle step has the greatest radial distance from the axis of rotation and the two outer steps have smaller radii. Here, the outer step of the gear can be designed to be narrower than the middle step when viewed in the axial direction.

[0037] In a development of the invention, the teeth of the external toothing have, viewed in the axial direction, an edge-side toothing section which transitions from a helical toothing with a helix angle W to a straight toothing with a helix angle 0. This measure makes it possible to distribute the stresses in the tooth roots of the teeth of the external toothing over a larger area. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The following is a more detailed description of the embodiments of the gear according to the present invention in conjunction with a plurality of figures. In the accompanying drawings:

[0039] Figure 1 A first embodiment of a gear according to the present invention is shown, viewing the front end side of the gear;

[0040] Figure 2 Shown along Figure 1 A cross-sectional view of the section line AA;

[0041] Figure 3 Shows Figure 1 and Figure 2 A three-dimensional view of the front end side of the gear;

[0042] Figure 4 Shows Figure 1 A three-dimensional view of the rear end side of the gear viewed from an oblique rear direction;

[0043] Figure 5 Shows Figure 1 An end side top view of the gear viewed from the rear end side;

[0044] Figure 6 Shows Figure 1 A side view of a gear with a clearly identifiable extension.

[0045] Figure 7 Shown according to Figure 1 An end plan view of a gear with a section line AA, wherein the section line AA is selected to be tangent to the pitch circle of the gear;

[0046] Figure 8 Shown according to Figure 1 A cross-sectional view of the section line AA;

[0047] Fig. 9 Shown with Figure 1 Similar view but with section line AA along the centre of the opening of the gear wheel on the outer ring.

[0048] Fig.10 Shows Fig. 9 Related cross-sectional views;

[0049] Fig.11 is similar to Figure 1 A second embodiment of the illustrated gear is shown in a top view on the front end side, wherein the openings arranged on the two rings are arranged offset with respect to one another; and

[0050] Fig.12 A detailed view of a gear wheel with external toothing is shown in the region of the tooth flanks. DETAILED DESCRIPTION

[0051] In the following drawings, unless otherwise specified, the same reference numerals denote the same components having the same meanings, respectively.

[0052] Figure 1 A first embodiment of a gear wheel 1 according to the invention is shown, viewed on its first axial end side 2. The gear wheel 1 has an external toothing 10 with teeth 12 which mesh helically at a helix angle W. The helix angle W is combined with Figure 7 and Figure 8 is obvious. Figure 7 In, with Figure 1 A similar illustration is shown in section along the section line AA, which is taken in the pitch circle of the external toothing 10 of the gear 1. The relevant section AA is at Figure 8 , and the helix angle W is plotted. The helix angle W is >0, and for example Figure 8 In the embodiment shown, it is approximately 15°. The helix angle may also be between approximately >0 and <25°, preferably between approximately 10° and 20°.

[0053] Back to Figure 1 The gear 1 has a central rotation axis R. A receiving opening 40 for receiving a hub, a shaft, etc. is provided in the center of the rotation axis R. An intermediate section 30 is provided between the receiving opening 40 and the external toothing 10. The intermediate section 30 has a plurality of openings 32, 33, which are arranged on two circular rings in the intermediate section 30. In this embodiment, the openings 32, 33 are formed as pocket openings (see Figure 2) is provided with reinforcing ribs 34, 35 for improving the strength of the entire gear 1. In the present case, these openings are formed approximately triangularly when viewed in cross section.

[0054] The external toothing 10 of the gear wheel 1 has a plurality of orbiting teeth 12 which are arranged obliquely with respect to the rotation axis R in accordance with the selected helical toothing. Figure 1 It can be seen that the opening 32 on the outer ring in the middle section 30 protrudes close to the root circle 13 of the outer toothing 10. Here, the opening 32 and the opening 33 arranged on the inner ring are placed radially flush with the tooth center of each tooth 12 of the outer toothing.

[0055] An annular rotating reinforcement ring 7 is provided between the annularly arranged openings 32 , 33 .

[0056] As described above, the outer toothing 10 of the gear 1 is designed with a helical toothing. At least a portion of the openings 32, 33 at least approximately follows the helix angle W of the helical toothing, more precisely at an opening angle V, which will be explained in more detail below. Therefore, these openings and the wall sections of the relevant openings 32, 33 are not arranged parallel to the rotation axis R of the gear 1, but are arranged obliquely to the rotation axis R, wherein the walls themselves can still rotate and twist.

[0057] Figure 1 The entire gear wheel 1 shown is designed as a single piece and is produced from plastic, in particular by a suitable plastic injection molding method, and has its external toothing 10 and a center section 30 with openings 32 , 33 arranged therein and reinforcing ribs 34 and a reinforcing ring 37 located therebetween.

[0058] exist Figure 2 Along Figure 1 In the cross-sectional view along the section line AA of FIG. 4 , the spindle nut teeth 42 arranged on the inner wall of the receiving opening 40 can be seen. The spindle nut teeth 42 are used to receive the spindle, for example, the spindle can be screwed into the electric brake to actuate the actuating piston. Figure 2 It can also be seen that gear 1 has Figure 2 The first axial end side 2 shown on the right and Figure 2 The second opposite axial end side 3 is shown on the left. On this second axial end side 3, an extension 60 protrudes from the second axial end side 3. The spindle nut toothing 42 in the opening 40 extends into this extension 60 in the interior of the gear 1, so that for Figure 2 The outer diameter D2 of the extension 60 is significantly smaller than the outer diameter D1 of the gear 1 .

[0059] It can also be seen that the opening 32 on the outer ring is arranged on a ring with diameter K1 and the opening 33 on the inner ring is arranged on an inner ring with smaller diameter K2. The openings 32, 33 are each designed as a blind hole and each have a bottom 32a, 33a.

[0060] Figure 2 It is also clearly shown that the radially outwardly directed end faces of the teeth 12 of the external toothing 10 are designed in a stepped manner and in the present example have three step regions a, b and c. The central step region b is the step region with the largest diameter D1. Step regions a and c are provided to the left and right of this step region b, which are slightly offset back to the step region b. Finally, Figure 2 Also visible in FIG. 5 is the orbiting concave depression 5 between the extension 60 and the second axial end side 3. The orbiting concave depression 5 ensures that shear forces are reduced when the gear wheel 1 is loaded.

[0061] Figure 3 and Figure 4 The first end side 2 of the gear 1 is shown. Figure 3 ) or observe the second rear axial end side 3 of the gear 1 ( Figure 4 ). Known reference numerals are further used in conjunction with Figure 1 and Figure 2 Part of the description. Especially from Figure 4 It can be clearly seen that three injection points 8 are provided in the orbiting concave depression 5, each offset by 120° about the rotation axis R, through which the plastic material is injected into the mold to form the gear 1 during the manufacture of the gear 1. It can also be clearly seen that the extension 60 is formed with an orbiting ring 62, away from which a plurality of evenly distributed and radially outwardly directed ribs 64 extend radially outward.

[0062] Figure 5 A front-side plan view of a second axial end side 3 of the gear wheel 1 is shown. Figure 6 Shows Figure 5 Top view of the gear rotated 90 degrees.

[0063] In the following Figures 7 to 12 In FIG. 1 , it is indicated at which opening angle V the openings 32 , 33 in the gear wheel 1 are selected relative to the rotation axis R and as a function of the helix angle W of the external toothing 10 according to the invention.

[0064] As mentioned earlier, Figure 7 A first axial end face 2 of the gear wheel 1 is shown in a top view at the end face. Figure 8 Shown along Figure 7sectional view of the section line AA of the gear 1. The section line AA is directed tangentially at the point of the gear 1 at which the pitch circle of the gear shown is located. The pitch circle of the gear is defined by half the height of the gear 12 of the gear 1 concerned. The entire diameter of the pitch circle is Figure 7 The relevant radius d0 / 2 is Figure 7 Thus, the section line AA intersects the tooth gap between two teeth 12 tangentially at half the height of the tooth 12 or the associated tooth gap located therebetween. It is precisely at this position that the helix angle W can be read, as Figure 8 As shown. The helix angle W is here approximately 15° and is selected in the counterclockwise direction relative to the axis of rotation R. This helix angle W is also decisive for the inclined arrangement of the openings 32, 33 according to the following formula:

[0065] V=arctan(tan(W)×(R) / (d0 / 2))

[0066] Where:

[0067] d0 / 2 = half of the pitch circle diameter of the external toothing (10),

[0068] R = distance of the center of one of the openings 32; 33 from the axis of rotation (R).

[0069] Combination Figures 9 to 12 This is explained in more detail.

[0070] Fig. 9 Shown with Figure 7 A similar illustration, but the section AA now runs tangentially through the center of one of the outer openings 32. This center of the opening 32 has a distance from the center of the axis of rotation R, which is indicated by the reference symbol R 32 The resulting opening angle V 32 For opening 32 the calculation is as follows:

[0071] V 32 =arctan(tan(W)×(R 32 / d0 / 2)

[0072] Where: W is the helix angle of the external tooth portion 10, d0 / 2 is half of the pitch circle diameter of the external tooth portion 10, R 32 Corresponds to the distance of the center of the opening 32 from the axis of rotation R.

[0073] It is clear from this rule that the angle V 32 Slightly smaller than the helix angle W of the opening 32 .

[0074] If the section AA is placed in the middle of the opening 33 located further inside, the opening angle V 33 The calculation is as follows:

[0075] V 33 =arctan(tan(W)×(R 33 / (d0 / 2))

[0076] Since the radius R 33 Smaller than the radius R discussed above 32 and is also smaller than the inclination angle W of the outer tooth portion 10, so the opening angle V of the opening 33 located on the inner ring is 33 Produces a smaller opening angle V 33 .

[0077] V 33 <V 32 <W

[0078] Although in the figures described above the openings 32, 33 are arranged radially flush with the corresponding teeth 12 of the external toothing 10, it is also possible to arrange the opening 33 offset from the opening 32 located above it. Fig.11 A first axial end side 2 of a gear wheel 1 is shown in a top view.

[0079] at last, Fig.12 A detailed view of a gear wheel of the external toothing 10 is shown in the region of the relevant tooth flank.

[0080] The half mold has a helix angle. The other side is divided into one side with a helix angle and one side with a vertical angle so that the tooth part can be demoulded accurately.

[0081] Description of reference numerals:

[0082] 1 Gear

[0083] 2First axial end side

[0084] 3 Second axial end side

[0085] 5 Concave depression

[0086] 7 Edge side tooth section

[0087] 8 Injection Points

[0088] 10 External teeth

[0089] 12 teeth

[0090] 13 Tooth root circle

[0091] 30 Middle section

[0092] 32 Opening

[0093] 32a Bottom of opening 32

[0094] 33 Opening

[0095] 33a Bottom of opening 33

[0096] 34 Reinforcement ribs

[0097] 35 Reinforcement ribs

[0098] 37 Reinforcement Ring

[0099] 40 Storage opening

[0100] 42 Spindle nut teeth

[0101] 60 Extension

[0102] 62 rings

[0103] D1 Outer diameter of gear 1

[0104] D2 The outer diameter of the extension portion 60

[0105] RRotation axis

[0106] W Helix Angle

[0107] V opening angle

[0108] K1 outer ring

[0109] K2 Inner Ring

[0110] a step area

[0111] b Step area

[0112] c Step area

Claims

1. A gear (1) made of a single piece of plastic, having: - axis of rotation (R); - an external toothing (10) arranged around the axis of rotation; - a centrally arranged receiving opening (40); - an intermediate section (30) arranged between the outer toothing (10) and the receiving opening (40); - a reinforcing structure arranged in the middle section (30), the reinforcing structure having a plurality of openings (32, 33) and reinforcing ribs (34, 35) located between the openings; It is characterized by the following additional features: The external toothing (10) is designed as a helical toothing with a helix angle (W) relative to the rotation axis (R); At least one portion of the openings (32, 33) at an opening angle (V) at least approximately follows the helix angle (W) of the helical toothing.

2. The gear (1) according to claim 1, characterized in that The openings (32, 33) are designed as blind holes.

3. The gear (1) according to claim 1 or 2, characterized in that: The openings (32, 33) are arranged around the rotation axis (R) in a double row of circles having different circle diameters (K1, K2).

4. The gear (1) according to claim 3, characterized in that The openings (32, 33) are arranged on the two circles in radial alignment with one another.

5. The gear (1) according to claim 3, characterized in that The openings (32, 33) are arranged on the two circles radially offset from one another.

6. Gear wheel (1) according to any one of the preceding claims, characterized in that A reinforcement ring (37) is arranged between the two circularly arranged openings (32, 33).

7. Gear wheel (1) according to any one of the preceding claims, characterized in that An opening (32) is arranged below each tooth root of a tooth (12) of the external toothing (10), and the opening (32) at least nearly extends to a root circle (13) of the corresponding tooth (12) of the external toothing (10) or protrudes beyond the root circle (13) into the corresponding tooth (12).

8. Gear wheel (1) according to any one of the preceding claims, characterized in that The openings (32, 33) have a shape different from a circular ring when viewed in cross section and are in particular elliptical or approximately triangular in shape.

9. A gear wheel (1) according to any one of the preceding claims, characterised in that A spindle nut tooth portion (42) is arranged in the receiving opening (40).

10. Gear wheel (1) according to any one of the preceding claims, characterized in that The gear wheel (1) has an extension (60) on one of its axial sides (2, 3) for receiving radial bearings and axial bearings, in particular ball bearings.

11. The gear (1) according to claim 10, characterized in that The extension (60) is designed as a revolving ring (62) having a plurality of ribs (64) uniformly distributed and directed radially outward, wherein an outer diameter (D2) of the extension (60) is smaller than an outer diameter (D1) of the external toothing (10).

12. The gear (1) according to claim 10 or 11, characterized in that A revolving concave recess (5) is provided between the extension portion (60) and the opposite axial side portion (3) of the gear (1).

13. Gear wheel (1) according to any one of the preceding claims, characterized in that The radially outwardly directed end face of the tooth (12) of the gear (10) has at least one, preferably a plurality of steps (a, b, c) when viewed in the axial direction of the gear (10).

14. The gear (1) according to claim 13, characterized in that The tooth (12) has three step regions (a, b, c), wherein the middle step region (b) is at a greater radial distance from the rotation axis (R) than the outer step regions (a, c).

15. Gear wheel (1) according to any one of the preceding claims, characterized in that The teeth (12) of the external toothing (10) have, viewed in the axial direction, an edge-side toothing section (7) which transitions from the helical toothing with the angle (W) to a straight toothing with a helix angle 0.

16. Gear wheel (1) according to any one of the preceding claims, characterized in that The helix angle (W) is greater than 0 and less than about 25 degrees, preferably about 10° to 20°, and especially approximately about 15°.

17. Gear wheel (1) according to any one of the preceding claims, characterized in that The opening angle (V) is smaller than the helix angle (W).

18. Gear wheel (1) according to any one of the preceding claims, characterized in that The opening angle (V) is at least approximately formed according to the following formula: V=arctan(tan(W)×(R) / (d0 / 2)) Where: d0 / 2 = half of the pitch circle diameter of the external toothing (10), R = distance of the center of one of the openings (32; 33) from the axis of rotation (R).

19. A method for manufacturing a gear according to any one of the preceding claims, wherein an insert is provided in the mold for forming the opening (32, 33), and the insert is moved out of the injected gear (32, 33) by equilateral rotation when the gear (1) is demoulded.

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