Worm gear unit for a gear means, actuating means for a brake master cylinder

Abstract

The invention relates to a worm gear unit (17) for a gear means (13), with a worm gear (18) which has a disc-shaped, in particular annular disc-shaped, main body (19), wherein a shell outer side (20) of the main body (19) has a worm toothing system (21), and wherein the main body (19) is manufactured from a plastic. It is provided that the worm gear unit (17) has at least one supporting element (31, 45) which is manufactured separately from the main body (19), bears against an end side (32, 47) of the main body (19), and is manufactured from a material which has a higher strength than the plastic of the main body (19).

Description

[0001] Description

[0002] title

[0003] Worm gear unit for a transmission device, actuating device for a master brake cylinder

[0004] The invention relates to a worm gear unit for a gear device, comprising a worm gear having a disc-shaped, in particular annular disc-shaped, base body, wherein an outer shell side of the base body has a worm toothing, and wherein the base body is made of a plastic.

[0005] Furthermore, the invention relates to an actuating device for a master brake cylinder, comprising a transmission device which can be driven by an electric motor and which has a transmission element which can be displaced in a first direction to actuate the master brake cylinder.

[0006] State of the art

[0007] Worm gears are known from the prior art. A worm gear typically has a disk-shaped base body. The worm gear's worm teeth are generally formed on the outer surface of the base body. It is known to construct the base body with the worm teeth from a metal material. This allows a worm gear with high rigidity to be obtained. However, the choice of a Meta II material is associated with a high mass of the worm gear. It is also known to construct the base body with the worm teeth from a plastic. A plastic base body offers significant functional advantages compared to a metal base body. However, from a wide range of plastics, only a small proportion are suitable for use as the base body of a worm gear in terms of their tribological properties.A major challenge is finding a plastic with sufficient strength, especially at high temperatures. While certain high-performance plastics meet this requirement, the use of high-performance plastics comes with high costs.

[0008] Disclosure of the invention

[0009] The worm gear unit according to the invention with the features of claim 1 has the advantage that the worm gear unit can be realized cost-effectively and with a low mass. According to the invention, the worm gear unit has at least one support element manufactured separately from the base body, which support element rests against an end face of the base body and is made of a material that has a higher strength than the plastic of the base body. As previously mentioned, typically only a few plastics are suitable for forming a base body of a worm gear. This is due to the fact that high axial forces act on the base body having the worm gearing during operation. Only a few plastics, such as the previously mentioned high-performance plastics, can withstand these axial forces.By using the support element in addition to the worm wheel, the selection of possible plastics for the base body of the worm wheel is expanded. For this purpose, the support element is made according to the invention from a material that has a higher strength than the plastic of the base body. In order to be able to absorb axial forces effectively, the support element rests against an end face of the base body. In particular, the end face of the base body is only partially occupied by the support element. However, the end face can also be occupied entirely by the support element. In the context of the disclosure, an end face refers to a side oriented perpendicular to the axis of rotation of the worm wheel. A shell outer face refers to a side directed radially outwards with respect to the axis of rotation. Correspondingly, a shell inner face refers to a side directed radially inwards with respect to the axis of rotation.If the terms "axial" and "radial" are used in the disclosure, these terms refer to the rotational axis of the worm gear, unless a different reference is expressly disclosed. Preferably, an inner surface of the worm gear casing has output teeth. However, the output teeth can also be formed at a different location, for example, on an outer surface of the worm gear casing. The worm gear unit according to the invention can be used, for example, in an actuating device for a brake master cylinder. However, the worm gear unit according to the invention is not limited to this use, so that a different use is also possible.

[0010] According to a preferred embodiment, the support element is attached to the worm wheel. This results in a mechanically robust worm wheel unit. If two elements are attached to one another, displacement of the two elements relative to each other is not possible. However, attaching the support element to the worm wheel is optional. According to an alternative embodiment, the support element is connected to the worm wheel, for example, by a positive connection, in such a way that relative movement of the support element relative to the worm wheel is possible.

[0011] According to a preferred embodiment, the support element is made of a metal II material. Metal materials are typically characterized by their high strength, making them advantageous for the construction of the support element. Particularly preferably, the support element is made of a steel material.

[0012] According to an alternative embodiment, it is preferably provided that the support element is made of a plastic that has a higher strength than the plastic of the base body. This also allows for effective support of the base body by the support element.

[0013] The base body is preferably made of a polyoxymethylene plastic. Due to its tribological properties, a polyoxymethylene plastic is particularly suitable for forming the base body with the worm gearing. According to a preferred embodiment, the support element has at least one axial projection which engages axially in a recess in the base body to stiffen the base body. The axial projection provides additional stiffening of the base body against radial and tangential forces. Preferably, the axial projection is manufactured in one piece with the support element. However, the axial projection can also be attached to the support element. Preferably, the axial projection is pin-shaped. Particularly preferably, there are several axial projections distributed in the circumferential direction of the support element.

[0014] According to a preferred embodiment, the worm gear unit comprises two support elements that rest on opposite end faces of the base body. A support element that rests on one end face of the base body provides particularly effective support for axial forces acting in the direction of the support element. Axial forces directed away from the support element are less effectively supported by the support element. Two support elements that rest on opposite end faces of the base body allow all axial forces to be effectively supported.

[0015] According to a preferred embodiment, the support elements are fastened to one another by at least one fastening means, which extends, in particular, axially through the base body. This results in a mechanically robust worm gear unit. The fastening means also stiffens the base body against radial and tangential forces. For example, the fastening means is designed as a screw. Particularly preferably, several fastening means are provided, which are distributed in the circumferential direction of the support elements.

[0016] Preferably, the support element or at least one of the support elements is designed in the shape of an annular disc. Axial forces can be effectively supported by an annular disc-shaped support element. Furthermore, due to its comparatively small dimensions in the axial direction, an annular disc-shaped support element is associated with low material costs and low mass.

[0017] Preferably, the support element or at least one of the support elements is sleeve-shaped. A sleeve-shaped support element has the advantage that even areas of the worm wheel enclosed by the sleeve-shaped support element can be protected by the support element. Furthermore, the sleeve-shaped support element can be used to rotatably support the worm wheel unit. If the worm wheel unit is installed as intended in a gear device, an outer shell side of the sleeve-shaped support element preferably bears radially from the inside against a rotatably mounted bearing part of a pivot bearing supporting the worm wheel unit. Preferably, the support element is designed as the inner ring of a rolling element bearing, for example of the aforementioned gear device, and for this purpose has in particular a guide recess for rolling elements of the rolling element bearing in its outer shell side.Particularly preferably, the worm gear unit has two support elements, one of which is annular disc-shaped and the other of which is sleeve-shaped. Alternatively, two annular disc-shaped support elements or two sleeve-shaped support elements are provided.

[0018] Preferably, the sleeve-shaped support element has a projection that rests against the end face of the base body. Due to the projection, the sleeve-shaped support element itself has a sufficiently large end face so that the support element can effectively support the base body against axial forces.

[0019] According to a preferred embodiment, the worm wheel has at least one sleeve-shaped axial section formed integrally with the base body, wherein a radial extent of the sleeve-shaped axial section is smaller than a radial extent of the base body, and wherein the sleeve-shaped support element radially encloses the sleeve-shaped axial section and bears against an outer shell side of the sleeve-shaped axial section. The sleeve-shaped axial section is formed integrally with the base body and is therefore also made of the plastic of the base body. Due to the contact of the sleeve-shaped support element with the outer shell side of the sleeve-shaped axial section, the sleeve-shaped axial section is protected by the support element. In particular, the aforementioned output toothing of the worm wheel is formed in the region of the sleeve-shaped axial section on the inner shell side of the worm wheel.The sleeve-shaped support element then supports the sleeve-shaped axial section against radial forces and tangential forces.

[0020] Preferably, the sleeve-shaped support element has a base that rests against an end face of the sleeve-shaped axial section. This allows the base of the support element to support axial forces acting on the sleeve-shaped axial section. Preferably, the base has an axial opening, for example, for a threaded spindle.

[0021] The actuating device according to the invention is characterized by the features of claim 14 in that the gear mechanism comprises the worm gear unit according to the invention. This also results in the aforementioned advantages. Further preferred features and combinations of features emerge from the above description and from the claims.

[0022] According to a preferred embodiment, the actuating device comprises a pivot bearing for the worm gear unit, and the support element of the worm gear unit rests radially from the inside on a rotatably mounted bearing part of the pivot bearing. In addition to supporting the base body, the support element thus has another function. The support element forms the contact surface for the rotatably mounted bearing part of the pivot bearing. For this purpose, the support element is preferably sleeve-shaped.

[0023] The invention is explained in more detail below with reference to the drawings.

[0024] Figure 1 shows an actuating device with a worm gear unit, Figure 2 shows another worm gear unit,

[0025] Figure 3 another worm gear unit,

[0026] Figure 4 another worm gear unit,

[0027] Figure 5 is a further illustration of the worm gear unit shown in Figure 4,

[0028] Figure 6 shows another worm gear unit, and

[0029] Figure 7 shows another worm gear unit.

[0030] Figure 1 shows a sectional view of an assembly 1 for a hydraulic brake system of a motor vehicle (not shown in detail). The assembly 1 has an actuatable master brake cylinder 2 with several hydraulic connections 3. Two hydraulic pistons 4 are slidably mounted in the master brake cylinder 2. If the assembly 1 is installed as intended in a brake system, the hydraulic connections 3 are fluidly connected to slave cylinders of friction brake devices of the brake system, so that the friction brake devices can be actuated by actuating the master brake cylinder 2. The assembly 1 also has an actuating device 5 for actuating the master brake cylinder 2. The actuating device 5 has a housing 6. The master brake cylinder 2 is arranged on a first end face 7 of the housing 6.The housing 6 is tubular in this case and therefore has a circumferential jacket wall 8 that encloses a housing interior 9 of the housing 6. The actuating device 5 also has a drive unit 10 that is arranged on the housing 6. The drive unit 10 has an electric motor 11, which is arranged in a motor housing 12 and is therefore not visible in Figure 1. A gear device 13 is operatively connected downstream of the electric motor 11. The electric motor 11 is designed to drive the gear device 13. The gear device 13 has a displaceably mounted gear element 14. The gear element 14 is displaceable in a first direction 15 and in a second direction 16 opposite to the first direction 15. In the present case, the gear element 14 is designed as a threaded spindle 14.The transmission element 14 is operatively connected or operatively connectable to the master brake cylinder 2 in such a way that the master brake cylinder 2 can be actuated by a displacement of the transmission element 14 in the first direction 15. Actuation of the master brake cylinder 2 means that the hydraulic pistons 4 are displaced in the first direction 15. If the assembly 1 is installed as intended in a braking system, this displaces hydraulic fluid from the master brake cylinder 2 into the slave cylinders of the wheel brake devices. In particular, one or more coupling elements are present, which are arranged between the transmission element 14 and the hydraulic pistons 4. The transmission element 14 is then operatively connected to the hydraulic pistons 4 by the coupling element or coupling elements.

[0031] The gear mechanism 13 also has a worm gear unit 17. The worm gear unit 17 has a rotatably mounted worm gear 18 with an annular disk-shaped base body 19. The worm gear 18 is rotatable about a rotation axis 25, which is aligned parallel to the directions 15 and 16. An outer shell 20 of the base body 19 has worm gear teeth 21. A worm shaft (not shown) of the gear mechanism 13 meshes with the worm gear teeth 21 of the worm gear 18. The base body 19 is made of a plastic, in this case a polyoxymethylene plastic. The worm gear 18 also has a sleeve-shaped first axial section 22. The first axial section 22 is formed integrally with the base body 19. Accordingly, the first axial section 22 is made of the same plastic as the base body 19.Given the arrangement of the worm gear unit 17 in the actuating device 5 shown in Figure 1, the first axial section 22 protrudes in the second direction 16 from the base body 19. The worm gear 18 also has a sleeve-shaped second axial section 23. The second axial section 23 is also formed integrally with the base body 19. Accordingly, the second axial section 23 is also made of the same plastic as the base body 19. Given the arrangement of the worm gear unit 17 in the actuating device 4 shown in Figure 1, the second axial section 23 protrudes in the first direction 15 from the base body 19. The radial extent of the axial sections 22 and 23 is smaller than the radial extent of the base body 19.

[0032] The worm wheel 18 has an axial opening 24. The axial opening

[0033] 24 extends through the base body 19 and the axial sections 22 and 23. The gear element 14 projects through the axial opening 24. The longitudinal center axis 26 of the gear element 14 corresponds to the rotation axis

[0034] 25 of the worm wheel 18. An inner shell side 27 of the worm wheel 18 has an output toothing 28. The output toothing 28 meshes with a drive toothing 29 of the gear element 14 such that the gear element 14 can be displaced in the first direction 15 or in the second direction 16 by rotating the worm wheel 18, depending on the direction of rotation of the worm wheel 18. The worm wheel 18 and the gear element 14 together form a spindle gear 30. In the present case, the output toothing 28 is formed in the region of the second axial section 23 on the inner shell side 27 of the worm wheel 18. Alternatively or additionally, the output toothing 28 is formed, for example, in the region of the base body 19 and / or in the region of the first axial section 22 on the inner shell side 27 of the worm wheel 18.

[0035] As previously mentioned, the base body 19 having the worm gearing 21 is made of a polyoxymethylene plastic. While this plastic has advantageous tribological properties, the strength of the plastic is limited. Accordingly, the base body 19 can be deformed by axial forces acting on the base body 19 during operation of the actuating device 5. To prevent deformation of the base body 19, the worm gear unit 17 has a first support element 31, which is manufactured separately from the base body 19. The first support element 31 is made of a material that has a higher strength than the plastic of the base body 19. For example, the first support element 31 is made of a metal material. Alternatively, the first support element 31 is made of a plastic that has a higher strength than the plastic of the base body 19.The first support element 31 bears axially against a first end face 32 of the base body 19. By bearing against the first end face 32, the first support element 31 can support axial forces acting on the base body 19 in the second direction 16. According to the exemplary embodiment shown in Figure 1, the first support element 31 is sleeve-shaped. The first support element 31 therefore has a circumferential casing wall 33. The first support element 31 encloses the first axial section 22, and an inner casing side 34 of the casing wall 33 bears radially against an outer casing side 35 of the first axial section 22. The sleeve-shaped first support element 31 has a projection 36. An end face 37 of this projection 36 bears against the first end face 32 of the base body 19. In the present case, the sleeve-shaped first support element 31 also has a base 38 with an axial opening 39. The base 38 rests axially against an end face 40 of the first axial section 22.

[0036] For the rotatable mounting of the worm gear unit 17, the actuating device 5 has a pivot bearing 41 with a first bearing part 42 fixed to the housing and a rotatably mounted second bearing part 43. An outer shell side 44 of the shell wall 33 of the first support element 31 rests radially from the inside against the second bearing part 43.

[0037] According to the exemplary embodiment shown in Figure 1, the worm gear unit 17 also has a second support element 45. The second support element 45 is also manufactured separately from the base body 19. In addition, the second support element 45 is also made of a material that has a higher strength than the plastic of the base body 19. In particular, the first support element 31 and the second support element 45 are made of the same material. According to the exemplary embodiment shown in Figure 1, the second support element 45 is also sleeve-shaped. Accordingly, the second support element 45 also has a circumferential jacket wall 48. An end face 46 of the second support element 45 bears axially against a second end face 47 of the base body 19, which face is facing away from the first end face 32 of the base body 19. Accordingly, the second support element 45 supports axial forces that act on the base body 19 in the first direction 15.An inner side 49 of the casing wall 48 radially abuts an outer side 50 of the second axial section 23. Accordingly, the sleeve-shaped second support element 45 also supports radial forces and tangential forces acting on the second axial section 23 during operation of the actuating device 4.

[0038] Several further exemplary embodiments of the worm gear unit 17 are explained in more detail below with reference to Figures 2 to 6. All exemplary embodiments have in common that the base body, which has the worm gearing, is made of a plastic. The supporting elements are made of a material that is more rigid than the plastic of the base body. It should be noted at this point that the use of the worm gear units 17 is not limited to the actuating device 5. Rather, the worm gear units 17 can also be used in other transmission devices.

[0039] In the exemplary embodiment of the worm gear unit 17 shown in Figure 2, the worm gear 18 has only the base body 19 and the first axial section 22. The output toothing 28 is formed in the region of the base body 19 and the first axial section 22 on the inner shell side 27. Furthermore, the first support element 31 is present, which axially bears against the first end face 32 of the base body 19. In terms of its structural design, the first support element 31 essentially corresponds to the first support element 31 shown in Figure 1.

[0040] The embodiment of the worm gear unit 17 shown in Figure 3 differs from the embodiment shown in Figure 2 in that the second support element 45 is also present, which axially rests against the second end face 47 of the base body 19. In the embodiment shown in Figure 3, however, the second support element 45 is designed in the shape of an annular disk. Furthermore, a plurality of fastening means 51 are provided, by means of which the support elements 31 and 45 are fastened to one another. The fastening means 51 extend axially through axial openings 52 in the base body 19 and thereby stiffen the base body 19 with regard to radial forces and tangential forces. The fastening means 51 are arranged distributed in the circumferential direction of the base body 19 or of the support elements 31 and 45. In the present case, the fastening means 51 are designed as screws 51.

[0041] Figures 4 and 5 show a further embodiment of the worm gear unit 17. Figure 4 shows a sectional view. Figure 5 shows a perspective view. The embodiment of the worm gear unit 17 shown in Figures 4 and 5 differs from the embodiment shown in Figure 2 in that the first support element 31 has a plurality of axial projections 53 which engage axially in recesses in the base body 19. The axial projections 53 are arranged in the region of the projection 36 and are manufactured integrally with the first support element 31. The axial projections 53 stiffen the base body 19 against radial and tangential forces. The axial projections 53 are arranged distributed in the circumferential direction of the base body 19 or the first support element 31. In the present case, the axial projections 53 are pin-shaped.Alternatively, the axial projections 53 are, for example, dome-shaped.

[0042] Figure 6 shows a further embodiment of the worm gear unit 17. In the embodiment shown in Figure 6, the worm gear 18 has only the base body 19. However, one of the axial sections 22 or 23, or both axial sections 22 and 23, may also be present. In the embodiment shown in Figure 6, the first support element 31 and the second support element 45 are present. Both support elements 31 and 45 are each annular disk-shaped.

[0043] Figure 7 shows a further embodiment of the worm gear unit 17, which differs from the previous embodiments in that the support element 31 forms an inner ring 54 or the bearing part 43 of the pivot bearing 41, which in this respect is a rolling element bearing 55. For this purpose, the support element 31 has, in particular on its outer shell 56, a guide groove or recess 57 extending over the entire circumference, in which rolling elements of the rolling element bearing are guided and supported. The integrated design of the inner ring 54 as the support element 31 or of the support element 31 as the inner ring 54 of the pivot bearing 41 results in simplified assembly and an advantageously space-saving design of the worm gear unit 17.

Claims

Claims 1. Worm gear unit for a gear device, with a worm gear (18) having a disk-shaped, in particular annular disk-shaped, base body (19), wherein an outer shell side (20) of the base body (19) has worm teeth (21), and wherein the base body (19) is made of a plastic, characterized in that the worm gear unit (17) has at least one support element (31, 45) which is manufactured separately from the base body (19), which rests on an end face (32, 47) of the base body (19) and is made of a material which has a higher strength than the plastic of the base body (19).

2. Worm gear unit according to claim 1, characterized in that the support element (31, 45) is fastened to the base body (19).

3. Worm gear unit according to one of the preceding claims, characterized in that the support element (31, 45) is made of a metal material.

4. Worm gear unit according to one of claims 1 and 2, characterized in that the support element (31, 45) is made of a plastic which has a higher strength than the plastic of the base body (19).

5. Worm gear unit according to one of the preceding claims, characterized in that the base body (19) is made of a polyoxymethylene plastic.

6. Worm gear unit according to one of the preceding claims, characterized in that the support element (31) has at least one in particular pin-shaped axial projection (53) which engages axially in a recess of the base body (19) to stiffen the base body (19).

7. Worm gear unit according to one of the preceding claims, characterized in that the worm gear unit (17) has two support elements (31, 45) which bear against mutually opposite end faces (32, 47) of the base body (19).

8. Worm gear unit according to claim 7, characterized in that the support elements (31, 45) are fastened to one another by at least one fastening means (51) which extends through the base body (19).

9. Worm gear unit according to one of the preceding claims, characterized in that the support element (31, 45) or at least one of the support elements (31, 45) is designed in the shape of an annular disc.

10. Worm gear unit according to one of the preceding claims, characterized in that the support element (31, 45) or at least one of the support elements (31, 45) is sleeve-shaped, in particular as an inner ring (54) of a rolling element bearing (55).

11. Worm gear unit according to claim 10, characterized in that the sleeve-shaped support element (31) has a projection (36), and that the projection (36) bears against the end face (32) of the base body (19).

12. Worm wheel unit according to one of the preceding claims, characterized in that the worm wheel (18) has at least one sleeve-shaped axial section (22, 23) formed integrally with the base body (19), wherein a radial extent of the sleeve-shaped axial section (22, 23) is smaller than a radial extent of the base body (19), and wherein the sleeve-shaped support element (31, 45) radially encloses the sleeve-shaped axial section (22, 23) and bears against a casing outer side (35, 50) of the sleeve-shaped axial section (22, 23).

13. Worm gear unit according to claim 12, characterized in that the sleeve-shaped support element (31) has a base (38), and that the base (38) bears against an end face (40) of the sleeve-shaped axial section (22).

14. Actuating device for a master brake cylinder, with a gear device (13) which can be driven by an electric motor (11) and which has a gear element (14) which can be displaced in a first direction (15) to actuate the master brake cylinder (2), characterized in that the gear device (13) has a worm gear unit (17) according to one of the preceding claims.

15. Actuating device according to claim 14, characterized in that the actuating device (5) has a rotary bearing (41) for the worm gear unit (17), and that the support element (31) of the Worm gear unit (17) rests radially from the inside on a rotatably mounted bearing part (43) of the pivot bearing (41).

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