Press fit system, press fit and drive train

Abstract

The present invention relates to a press-fit system comprising a first element (20) and a second element (22). The first element (20) and the second element (22) are insertable into one another for connection. The first element (20) has a cutting tooth (26) which, upon insertion, cuts a corresponding tooth profile (32) into the second element (22) in a cutting direction (34). After connection, the cutting tooth (26) and the tooth profile (32) form a press fit, and the cutting tooth (26) is designed for an increasing pressure opposite to the cutting direction (34). The invention also relates to a press fit and a drive train.

Description

[0001] The present invention relates to a press-fit system with which two elements can be joined to one another by means of an interference fit and corresponding toothing, particularly for a bicycle. The invention also relates to a press fit and a drive train.

[0002] It is known to connect two components using a splined connection. The splined connection typically forms an undefined fit, which can result in uneven loading of the splined connection.

[0003] From DE 23 47 372 A1 a positive locking connection of two components is known, in which one of the two components has teeth with cutting surfaces which, when the two components are pressed together, cut a toothing in the other component.

[0004] From DE 10 2007 000 659 A1, a positive-locking connection of two interlocking components with toothing is known. Guide surfaces are provided to center the two components relative to each other when the connection is made.

[0005] DE 10 2007 000 659 A1 discloses a bearing device for a wheel of a vehicle and a manufacturing method for such a bearing device.

[0006] From JP 2003 065 316 A a connection structure between components, in particular a connection structure of a metal yoke and a glass fiber reinforced plastic cylinder in a drive shaft, is disclosed.

[0007] The object of the present invention is therefore to propose a press-fit system that is improved upon the prior art. This object is achieved by the subject matter with the features of the independent claims. Advantageous further developments are described in the dependent claims.

[0008] One aspect concerns a press fit system with a first element and a second element. These two elements could be components of a drivetrain. For example, the first element could be a shaft, and the second element could also be a shaft. The shafts could be, for example, a motor shaft and a gearbox shaft. For instance, the first element could be a bicycle crank axle, and the second element a rotating element of the bicycle's planetary gear system. One of the two elements could also be a stationary component, such as a housing. The press fit system can be designed to join the two elements together. The press fit system can be designed to create a defined press fit between the two elements.

[0009] The first and second elements can be inserted into one another for connection. For example, the second element can have a recess into which the first element can be at least partially inserted. Conversely, the first element can also have a recess into which the second element can be at least partially inserted. The examples described below, in which the first element is inserted into the second element, also apply equally to configurations in which the second element is inserted into the first element. The two elements can be moved relative to each other for insertion. Insertion allows the two elements to be permanently joined. Insertion creates a press-fit connection between the two elements. During insertion, the two elements can be pressed together.The recess in one of the two elements for receiving the other can be designed to correspond to an outer contour of an insertion section of the other element. The recess in one element for receiving the other can, for example, be cylindrical.

[0010] The first element features a cutting tooth. The cutting tooth can have teeth, each with a cutting end. The teeth of the cutting tooth can be arranged around the circumference of the first element. The cutting end can be designed, for example, as a cutting edge or a cutting surface. A toothed section can adjoin the cutting tooth, through which torque can be transmitted from the first component to the second component after they are joined. For example, the cutting tooth cuts material from the second element during insertion, such as on an adjacent surface. The toothed section, however, does not cut material from the second element during insertion. Torque transmission can occur, for example, via the respective tooth flanks of the cutting tooth, such as the tooth flanks of the toothed section.The first element can, for example, be hardened in the cutting area. The cutting teeth may extend axially only over a portion of the first element. The cutting teeth may, for example, project radially, for instance, towards the second element after insertion.

[0011] The cutting teeth are designed to cut a corresponding tooth profile into the second element in a specific cutting direction during insertion. This cutting direction can, for example, correspond to the insertion direction of the first element into the second element. The cutting direction can also be the direction in which the material is cut from the second element during insertion. The cutting direction can run from the point that is cut first during insertion to the point that is cut last. The cutting direction can be parallel to a longitudinal axis of the first component and, alternatively or additionally, to that of the second component. The cutting direction can be coaxial with a longitudinal axis of a recess in either component. The tooth profile can have a corresponding number of teeth to the teeth of the cutting teeth of the first element.The teeth of the tooth profile can be arranged around the circumference of the second element. Torque can be transmitted between the first and second components via the tooth profile after they are joined. This torque transmission can occur, for example, via the respective tooth flanks of the tooth profile. The tooth flanks of the tooth profile and the cutting teeth can be in contact with each other after the two elements are joined. The first element, and alternatively or additionally the second element, can have a cylindrical shape in the area of ​​the press fit, the cutting teeth, and the tooth profile.

[0012] The cutting teeth and tooth profile form an interference fit after the first element is connected to the second, for example, by insertion. The cutting teeth are designed for an increasing pressure in the opposite direction of cutting. For example, the dimension of the teeth of the cutting teeth can increase from the cutting area in the opposite direction of cutting. This displaces additional material behind the cutting area during insertion, resulting in a defined interference fit of the first element to the second element in the area of ​​their teeth. This dimensionally increasing area, for example, the toothed area, does not cause any further cutting of material in the second element during insertion. The interference fit thus created allows the elements to be held together particularly securely.Furthermore, the transmission of a particularly high torque may be possible. The connection between the two elements can be designed to be rotationally fixed.

[0013] In another embodiment of the press fit system, the contact pressure can increase strictly monotonically in the opposite direction to the cutting direction. For example, the contact pressure can be lowest at the end face of the first or second element, which was inserted first. In this end face, a clearance fit or loose fit may even exist. However, an interference fit may also already be present there. The contact pressure can increase continuously towards the last inserted element. Due to the strictly monotonous increase in contact pressure, inserting the two elements into each other can be particularly easy. For example, the force required to insert the two elements into each other can increase continuously. This allows for minimal force to be required at the beginning of a cutting operation of the tooth profile.This makes assembling the two elements of the press fit system and joining them together particularly easy. Alternatively, the pressure can increase exponentially against the cutting direction, increase in stages, or alternatively or additionally increase monotonically instead of strictly monotonically.

[0014] In another embodiment of the press-fit system, the height of each tooth of the cutting gear can increase in the opposite direction to the cutting direction. The height of the individual teeth can increase, for example, in steps or in a strictly monotonous manner. For instance, all teeth of the cutting gear can be identical or exhibit different height increases. The height of a tooth of the cutting gear can, for example, be the distance between the tooth root and the tooth tip. The height of the teeth of the cutting gear can, for example, correspond to their tip height and, alternatively or additionally, their root height. The height of the teeth of the cutting gear can correspond to their radial extent. For example, the height of each tooth of the cutting gear can increase continuously from one end, which is first inserted into the second element, along an axial extent of the teeth.A low side of the teeth is formed, for example, at the axial end of each tooth that lies in the cutting direction. The low side of the teeth can be adjacent to the cutting area or form the cutting area itself. A high side of the teeth is formed, for example, at the axial end of each tooth that faces away from the cutting direction. The increasing height of the teeth allows for a strong radial pressure to be achieved.

[0015] In another embodiment of the press-fit system, the individual teeth of the cutting gear can have a conical height profile. For example, in a side view, the teeth of the cutting gear can have a straight, ramp-like profile. Such a height profile of the cutting gear teeth can be easy to manufacture.

[0016] In another embodiment of the press-fit system, the width of each tooth of the cutting gear can increase in the opposite direction to the cutting direction. The width of each tooth can increase, for example, in steps or in a strictly monotonous manner. For instance, all teeth of the cutting gear can be identical or exhibit different increases in width. The width of a tooth of the cutting gear can, for example, be the circumferential distance between two tooth bases. The width of the teeth of the cutting gear can, for example, correspond to their tooth thickness. The width of the teeth of the cutting gear can correspond to their circumferential extent. For example, the width of each tooth of the cutting gear can increase continuously from one end, which is first inserted into the second element, along the axial extent of the teeth.A narrow side of the teeth is formed, for example, at an axial end of each tooth that lies in the cutting direction. This narrow side can be adjacent to the cutting area or may even form the cutting area itself. A wide side of the teeth is formed, for example, at an axial end of each tooth that faces away from the cutting direction. The increasing width of the teeth against the cutting direction allows for strong contact pressure between the tooth flanks of the cutting teeth and the tooth profile.

[0017] In another embodiment of the press-fit system, the individual teeth of the cutting gear can have a wedge-shaped width profile. For example, in a top view, the teeth of the cutting gear can have a wedge-shaped profile with straight flanks. The two opposing tooth flanks of a tooth of the cutting gear can converge in the top view against the cutting direction. Such a width profile of the teeth of the cutting gear can be easy to manufacture.

[0018] In a further embodiment of the press-fit system, the system may include a fixing element. This fixing element can secure the first element to the second element in the cutting direction. For example, it can block axial movement of the two elements relative to each other in the cutting direction. This reliably prevents the two elements from separating, for example, due to vibrations. The fixing element can be, for example, a screw or a dowel pin. The second element may have a through-hole through which the fixing element is inserted and engages with an internal thread in the first element. Tightening the screw then fixes the two elements together. The fixing element can also serve to slide the two elements together.For example, tightening the screw can press the first element into the second element. Tightening the screw also allows the tooth profile to be cut with the cutting teeth. This makes assembly particularly simple and requires few steps. The press-fit system can be designed to use the fixing element to pull the first and second elements together in one cutting direction, thus joining them, cutting the tooth profile, and forming the press connection.

[0019] In a further embodiment of the press-fit system, the second element may have a recess for inserting the first element. For example, the second element may have a cylindrical through-hole or a cylindrical blind hole into which a corresponding section of the first element with the cutting teeth can be inserted. The second element may have a radial recess at its end (e.g., on the bottom) in the cutting direction, in which chips can be collected during the cutting of the tooth profile. The cutting teeth may be formed on an outer circumference of the first element. For example, the first element with the cutting teeth may cut the tooth profile on an inner circumference of the recess of the second element. Manufacturing the cutting teeth on the outer circumference of the first element can be particularly simple and cost-effective.

[0020] In another embodiment of the press-fit system, the first element may have a recess for inserting the second element. The cutting teeth may be formed on the inner circumference of the recess in the first element. The design here can therefore be the reverse of the embodiment described previously. For example, the first element may have a cylindrical through-hole or a cylindrical blind hole into which a corresponding section of the second element can be inserted. The tooth profile can then be cut in this section of the second element. For example, the first element with its cutting teeth can cut the tooth profile on the outer circumference of the second element. The cutting teeth on the inner circumference of the first element can be well protected from damage before the two elements are joined.

[0021] In a further embodiment of the press-fit system, the first element may have a mating surface in the cutting direction upstream of the cutting teeth, which guides the first and second elements during insertion. For example, the mating surface may be formed by a cylindrical section in the cutting direction upstream of the cutting teeth. The mating surface can, for example, ensure concentricity of the two elements during insertion before the start of a cutting operation on the tooth profile. The mating surface may be separated from the cutting teeth, for example, by a circumferential groove. This prevents the mating surface from interfering with the cutting process.

[0022] A second aspect concerns a press fit with a first element and a second element. The press fit can be formed from the press fit system according to the first aspect. Further features, embodiments, and advantages are described in the first aspect. Conversely, features, embodiments, and advantages of the second aspect also represent features, embodiments, and advantages of the first aspect.

[0023] The first element of the press fit has a cutting tooth, and the second element has a corresponding tooth profile. The tooth profile is cut by the cutting tooth when the first and second elements are inserted into each other. The cutting tooth and the tooth profile form a press fit. The contact pressure between the cutting tooth and the tooth profile increases in the opposite direction to the cutting direction, and thus, for example, in the insertion direction. For instance, one dimension of the cutting tooth may be constant in the opposite direction to the cutting direction, while the cross-section of the tooth profile along its path in the opposite direction to the cutting direction would be constant, or even entirely constant, at least when no contact pressure is present.

[0024] A third aspect concerns a drive train with a first element and a second element. For example, the two elements are designed as gear elements of the drive train, which are permanently and rotationally fixed to each other. The two elements form an interference fit according to the second aspect. Further features, embodiments, and advantages can be found in the descriptions of the second and first aspects. Conversely, features, embodiments, and advantages of the second and first aspects also represent features, embodiments, and advantages of the third aspect. Fig. Figure 1 shows a schematic sectional view of a press fit with a first element and a second element. Fig. Figure 2 shows a schematic top view of a first variant of the first element. Fig. Figure 3 shows a schematic top view of a second variant of the first element.

[0025] Fig. Figure 1 shows a schematic sectional view of a press fit with a first element 20 and a second element 22. The first element 20 is designed as a pedal crank axle. The second element 22 is designed as an input shaft of a bicycle gearbox. The second element 22 has a cylindrical recess 24 into which the first element 20 is inserted with a cylindrical end section. A press fit is formed between the first element 20 and the second element 22.

[0026] The first element 20 has a cutting tooth 26 on its outer circumference in an axial section, which is formed by radially outer teeth 28. To connect the two elements 20, 22, the first element 20 is inserted into the second element 22 along its axial extent in an insertion direction and thus cutting direction towards the bottom of the recess 24. The cutting direction is in Fig. 1 illustrated by arrow 34. At a leading end of the cutting tooth 26 in this cutting direction, each of the teeth 28 of the first element 20 has a cutting area 30. This cutting area 30 cuts into an inner circumference of the second element 22 in the recess 24 a tooth profile 32 corresponding to the cutting area of ​​the cutting tooth 26. The tooth profile 32 has a constant cross-section along its longitudinal extent in the cutting direction. The teeth of the tooth profile 32 of the second element 22 have a constant height and a constant width. The constant height is in Fig. 1 illustrated by line 40.

[0027] The cutting teeth 26 of the first element 20 are designed for a pressure increasing in the opposite direction of cutting. In the Fig. In the embodiment shown in Figure 1, the pressure increases strictly monotonically against the cutting direction. For this to occur, the height of the respective teeth 28 of the cutting teeth 26 increases against the cutting direction. This results in a conical height profile of the respective teeth 28 of the cutting teeth 26, which for one of the teeth 28 in Fig. This is illustrated by a straight line 56. Due to this increase in height of the teeth 28 of the cutting teeth 26, a radial pressure between the inner circumference of the second element 22 in the recess 24 and the outer circumference of the first element 20 increases strictly monotonically against the cutting direction and thus towards the opening of the recess 24. In this way, a defined press fit can be provided, which ensures a particularly good connection between the two elements 20 and 22.

[0028] The second element 22 has a through-opening 36 at the base of the recess 24. A fixing element in the form of a screw 38 is arranged in the through-opening 36. The screw 38 fixes the first element 20 to the second element 22 in the cutting direction. The screw 38 engages with an internal thread in a through-opening 42 of the first element 20. By tightening the screw 38, the first element 20 can also be drawn into the recess 24 to connect the two elements 20 and 22, and thus pressed in. During this drawing in and insertion of the first element 20 into the second element 22, the tooth profile 32 is also cut into the second element 22.

[0029] The first element 20 has a cylindrical end piece 44 at its end facing the bottom of the recess 24 and thus at the front end in the cutting direction, in front of the cutting teeth 26 and the cutting area 30. This end piece forms a mating surface on its outer circumference. The mating surface guides the first element 20 and the second element 22 together during insertion and ensures concentricity between the two elements 20 and 22 before cutting of the tooth profile 32 begins. The mating surface and the end piece 44 are axially separated from the cutting teeth 26 by a circumferential groove 46 in the first element 20.

[0030] Fig. Figure 2 illustrates a first variant of the first element 20, in which the teeth 28 of the cutting teeth 26 are arranged differently than in Figure 2. Fig. 1 are designed. The width of the respective teeth 28 of the cutting teeth 26 is not constant as in Fig. 1, but increases strictly monotonically in the direction of cutting over its entire extent, contrary to the cutting direction. The width corresponds to the extent of the teeth 28 in the circumferential direction between their tooth flanks. A wedge-shaped width profile is formed, as in Fig. 2 illustrated by lines 48. This design of the width profile according to the first variant of the first element 20 is combined in one embodiment with a constant height of the teeth 28 of the cutting teeth 26 and in another embodiment with a height increasing in the opposite direction of the cutting, as in Fig. 1 shown.

[0031] Fig. Figure 3 illustrates a second variant of the first element 20, in which the teeth 28 of the cutting teeth 26 are arranged differently than in Figure 3. Fig. 1 are designed. The width of the respective teeth 28 of the cutting teeth 26 increases against the cutting direction in a forward end region 50 in the cutting direction. In a region 52 adjoining this, against the cutting direction, the respective teeth 28 of the cutting teeth 26 have a continuous width. In the second variant, the width of the respective teeth 28 of the cutting teeth 26 increases against the cutting direction over their entire extension in the cutting direction, i.e., monotonically but not strictly monotonically. The forward end region 50 forms a wedge-shaped width profile. The width of the teeth 28 of the cutting teeth 26 is in Fig. 3 illustrated by lines 54. This design of the width profile according to the second variant of the first element 20 is combined in one embodiment with a constant height of the teeth 28 of the cutting teeth 26 and in another embodiment with a height increasing against the cutting direction, as in Fig. 1 shown. Reference sign 20 first element 22 second element 24 cylindrical recesses 26 cutting teeth 28 teeth 30 cutting area 32 Tooth Profile 34 Arrow / Cutting direction 36. Passage opening of the second element 38 Screw / Fixing element 40 Line constant height of the teeth of the tooth profile 42. Passage opening of the first element 44 End piece / Fitting surface 46 Nut 48 lines of wedge-shaped width profile of the teeth of the cutting teeth 50 End range 52 area 54 lines width of the teeth of the cutting teeth 56 Line conical height profile of the teeth of the cutting teeth

Claims

[1] Press-fit system with a first element (20) and a second element (22), wherein the first element (20) and the second element (22) can be inserted into one another for connection, wherein the first element (20) has a cutting tooth (26) which, upon insertion, cuts a corresponding tooth profile (32) into the second element (22) in a cutting direction (34), wherein the cutting tooth (26) and the tooth profile (32) form a press fit after the first element (20) is connected to the second element (22), and wherein the cutting tooth (26) is designed for a pressure increasing in the opposite direction to the cutting direction (34). characterized by , that the width of each tooth (28) of the cutting teeth (26) increases in the opposite direction of cutting (34). [2] Press dressing system according to claim 1, characterized by , that the pressure increases strictly monotonically in the opposite direction of the cut (34). [3] Press-fit system according to claim 1 or 2, characterized by , that the height of each tooth (28) of the cutting teeth (26) increases in the opposite direction of cutting (34). [4] Press dressing system according to claim 3, characterized by , that the respective teeth (28) of the cutting teeth (26) have a conical height profile. [5] Press dressing system according to claim 1, characterized by , that the respective teeth (28) of the cutting teeth (26) have a wedge-shaped width profile. [6] Press-fit system according to one of the preceding claims, characterized by , that the press fitting system has a fixing element (38), wherein the press fitting system is designed to fix the first element (20) to the second element (22) in the cutting direction (34) by means of the fixing element (38). [7] Press bandage system according to one of the preceding claims, characterized by, that the second element (22) has a recess (24) for the insertion of the first element (20) and the cutting teeth (26) are formed on an outer circumference of the first element (20). [8] Press-fit system according to any one of claims 1 to 5, characterized by , that the first element (20) has a recess (24) for the insertion of the second element (22) and the cutting teeth (26) are formed on an inner circumference of the recess (24) of the first element (20). [9] Press bandage system according to any one of the preceding claims, characterized by , that the first element (20) in the cutting direction (34) has a mating surface (44) in front of the cutting teeth (26) which guides the first element (20) and the second element (22) during insertion. [10] Press bandage, characterized by that the press bandage can be formed from the press bandage system according to one of the preceding claims. [11] Drive train suitable for a bicycle, comprising a first element (20) and a second element (22), wherein the two elements (20, 22) form a press fit according to claim 10.

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