Pedal crank system and pedal crankshaft

Abstract

Pedal crank system with a first pedal crank part (20) and a second pedal crank part (22), wherein the first pedal crank part (20) and the second pedal crank part (22) are insertable into each other for connection to form a pedal crank for a bicycle, wherein the first element (20) has a cutting tooth (26) which, when inserted, cuts a corresponding tooth profile (32) into the second element (22) in a cutting direction (34).

Description

[0001] The present invention relates to a crankset system in which two crankset parts can be connected to each other by interlocking teeth to form a crankset. The invention also relates to a crankset for a bicycle.

[0002] It is known to connect two components using a splined connection. 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, engage a tooth in the other component. One of the two components is a ring gear and the other is a gearbox housing.

[0003] Bicycle crank axles are usually manufactured as a single piece. However, this can complicate assembly. Furthermore, attaching other components to the crank axle can be difficult. Two-piece crank axles are also known, for example from DE 10 2021 102 992 A1.

[0004] DE 10 2007 062 156 A1 describes a bottom bracket with a torque sensor system, consisting of a crank arm, a non-rotatably connected hollow shaft and a torque detection device that detects a change in magnetization due to the torque introduced into the hollow shaft.

[0005] US 1 235 530 A describes a bottom bracket for a bicycle, consisting of a mounting bracket, ball bearing housings, a two-piece crank axle, two sleeves, means for preventing relative rotation of the sleeves, ball cones on the sleeves for cooperation with the ball bearing housings, and means for adjustable retention of the sleeves in axial relation to each other.

[0006] US 549 313 A describes a bottom bracket for a bicycle, consisting of a mounting bracket, a two-piece crank axle, two sleeves, means to prevent the relative rotation of the sleeves, ball cones on the sleeves to cooperate with the ball bearing housings, and means to adjust the retention of the sleeves in axial relation to each other.

[0007] US 648 077 A describes a bicycle crank consisting of two parts, the first part comprising an arm and shaft with threads and conical grooves, and the second part comprising an arm and sleeve with internal ribs complementary to the grooves, such that the parts are tightly connected to each other by a nut.

[0008] DE 10 2012 111 124 B3 describes a method for manufacturing a composite crankshaft for an internal combustion engine, in which crank webs with receiving openings and crank pins with end-side fastening sections are provided, which are positively connected by a toothed connection, so that the joining partners are securely fixed without additional fastening means.

[0009] US 2015 / 0016873A1 describes a metallic sleeve that can be pressed onto a softer metal shaft with relatively low axial forces to create a permanent press fit, the sleeve having inside several axially spaced rows of teeth with angled cutting edges and intervening circumferential grooves for receiving chips.

[0010] It is therefore an object of the present invention to provide a pedal crank axle 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.

[0011] A first aspect concerns a crankset system with a first crankset section and a second crankset section. The two crankset sections can together form the crankset of a bicycle, particularly a bicycle with an electric auxiliary motor, such as a pedelec. The crankset system can be designed to join the two crankset sections together. The crankset system can be designed to create a defined fit between the two crankset sections. Each crankset section can be a shaft element. For example, each crankset section can be supported in the bicycle by a bottom bracket, such as a roller bearing.

[0012] The first and second crank arm sections can be inserted into each other to form a complete crank arm for a bicycle. The crank arm can thus be a two-piece design, for example, joined axially in a central section. The crank arm can form part of the bicycle's drivetrain, to which a rider applies power through muscle power. A crank arm with a rotatable pedal can be attached to opposite ends of the crank arm. The two-piece design allows for easy assembly of the crank arm. Furthermore, the diameter can be largest at each end, while still allowing for the easy attachment of another component, such as a sleeve, in the center. This enables the use of standard bottom brackets without hindering the installation of other components with smaller inner diameters.

[0013] For example, the second crank arm section can have a recess into which the first crank arm section can be at least partially inserted. Conversely, the first crank arm section can also have a recess into which the second crank arm section can be at least partially inserted. The examples described below, in which the first crank arm section is inserted into the second crank arm section, also apply equally to embodiments in which the second crank arm section is inserted into the first crank arm section. The two crank arm sections can be moved relative to each other for insertion. By inserting them, the two crank arm sections can be permanently and, alternatively or additionally, rotationally fixed to one another.The recess in one of the two crankshaft parts for receiving the other crankshaft part can be designed to correspond to an outer contour of an insertion section of the other crankshaft part. The recess in one crankshaft part for receiving the other crankshaft part can, for example, be cylindrical.

[0014] The first crank arm section has a cutting tooth profile. The cutting tooth profile can have teeth, with each tooth having a cutting edge on its face. The teeth of the cutting tooth profile can be arranged around the circumference of the first crank arm section. The cutting edge can be designed, for example, as a cutting edge or a cutting surface. A toothed section can be connected to the cutting edge, through which torque can be transmitted from the first crank arm section to the second crank arm section after they are joined. For example, the cutting edge profile cuts material from the second crank arm section during insertion, such as on an adjacent surface. After insertion, the toothed section does not continue to cut material from the second crank arm section.Torque transmission can occur, for example, via the respective tooth flanks of the cutting teeth, such as the tooth flanks of the toothed section. The toothing formed between the two crank arm sections during insertion can create a rotationally fixed connection. Axial fixation and absorption of bending forces can be achieved in other ways, for example, through toothless areas on the two crank arm sections. The first crank arm section can, for example, be hardened in the cutting area. Generally, the first crank arm section can be harder than the second. The cutting teeth may, for example, extend axially only over a portion of the first crank arm section. The cutting teeth may, for example, protrude radially, for instance, towards the second crank arm section after insertion.

[0015] The cutting teeth are designed to cut a corresponding tooth profile into the second crank arm section in a specific cutting direction during insertion. This cutting direction can, for example, correspond to the insertion direction of the first crank arm section into the second. Alternatively, the cutting direction can be the direction in which the material is cut from the second crank arm section 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 crank arm section and, alternatively or additionally, to a longitudinal axis of the second crank arm section. These longitudinal axes can correspond to a rotational axis of the crank arm.The cutting direction can be coaxial with a longitudinal axis of a recess in one of the two crank arm sections. The tooth profile can have a corresponding number of teeth to the teeth of the cutting teeth of the first crank arm section. The teeth of the tooth profile can be arranged on the circumference of the second crank arm section. Torque can be transmitted between the first and second crank arm sections via the tooth profile after they are joined. The 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 crank arm sections are joined. The first crank arm section, and alternatively or additionally the second crank arm section, can have a cylindrical shape in the area of ​​their connection, the cutting teeth, and the tooth profile.The two crank arm sections can have a cylindrical shape overall. The cutting teeth and, alternatively or additionally, the tooth profile can extend axially along each crank arm section, for example, on an inner or outer circumference. The two crank arm sections can be pressed together during insertion. For example, insertion can be achieved using a hydraulic press.

[0016] In a further embodiment of the crankset system, the cutting teeth and tooth profile can form an interference fit after the first crankset section is joined to the second. This interference fit is achieved by insertion. For example, a dimension of the teeth of the cutting teeth, or an intermediate section between individual teeth, can press against the other crankset section. This creates an interference fit between the first and second elements. The interference fit allows for a particularly secure hold between the elements. Furthermore, it enables the transmission of exceptionally high torque. The connection between the two elements can be designed to be rotationally fixed.

[0017] In another embodiment of the crankset system, the cutting teeth and tooth profile can form a transition fit after the first crankset section is joined to the second. The tolerances can be selected such that a loose fit or interference fit is randomly generated, possibly varying in different areas. This allows for particularly cost-effective manufacturing and the use of large tolerances.

[0018] In another embodiment of the crankset system, the cutting teeth and tooth profile can form a loose fit after the first crankset section is joined to the second. This allows for particularly low insertion force. Maintenance can also be very simple. Furthermore, this prevents bending forces from being transmitted in the area of ​​the teeth. The two crankset sections can have a greater clearance than their respective adjacent mating surfaces, so that bending forces are transmitted exclusively or at least predominantly at these mating surfaces. This prevents damage to the teeth, even under high bending loads. High bending loads can occur, especially with cranksets, depending on usage and rider position.

[0019] In a further embodiment of the crankset system, the system may include a locking element. This locking element can be designed to fix the first crankset section to the second crankset section in the cutting direction. For example, the locking element can block axial movement of the two crankset sections relative to each other in the cutting direction. This reliably prevents the two crankset sections from separating, for example, due to vibrations. The locking element can be designed, for example, as a screw or a dowel pin. The second crankset section may, for example, have a through-hole through which the locking element is inserted and engages in an internal thread of the first crankset section.Tightening the screw then fixes the two crank arm sections together. The fixing element can also be used to slide the two crank arm sections into each other. For example, tightening the screw can press the first crank arm section into the second. Tightening the screw also allows the tooth profile to be cut with the cutting teeth. This makes assembly particularly easy and requires only a few steps. The crank arm system can be designed so that the fixing element pulls the first and second crank arm sections together in one cutting direction to join them, cut the tooth profile, and form the press fit. Alternatively or additionally, axial fixing can also be achieved by gluing or welding.

[0020] In a further embodiment of the crankset system, the second crankset section may have a recess for inserting the first crankset section. For example, the second crankset section may have a cylindrical through-hole or a cylindrical blind hole into which a corresponding section of the first crankset section with the cutting teeth can be inserted. The second crankset section 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 crankset section. For example, the first crankset section with the cutting teeth may cut the tooth profile on an inner circumference of the recess of the second crankset section.Manufacturing the cutting teeth on the outer circumference of the first part of the pedal crank shaft can be particularly simple and cost-effective.

[0021] In a further embodiment of the crankset system, the first crankset section may have a recess for inserting the second crankset section. The cutting teeth may be formed on an inner circumference of the recess in the first crankset section. The design here can therefore be the reverse of the embodiment described previously. For example, the first crankset section may have a cylindrical through-hole or a cylindrical blind hole into which a corresponding section of the second crankset section can be inserted. The tooth profile can then be cut in this section of the second crankset section. For example, the first crankset section with its cutting teeth can thus cut the tooth profile on an outer circumference of the second crankset section.The cutting teeth on the inner circumference of the first crankshaft part can be well protected from damage before the two parts are joined together.

[0022] In a further embodiment of the crankset system, the first and second crankset sections can be designed to abut each other in the cutting direction when joined. This allows for a defined connection position. For example, when inserted into the blind recess of the second crankset section, the first crankset section can abut the bottom of the blind recess. This achieves a defined assembly position. The abutment can also be formed, for example, by a protruding portion of the first crankset section that abuts the outer wall of the recess of the second crankset section during insertion.

[0023] In a further embodiment of the crankshaft system, the first crankshaft section may have a first mating surface in the cutting direction upstream of the cutting teeth. This first mating surface can guide the first and second crankshaft sections during insertion. It can also absorb bending loads. The second crankshaft section may have a first mating surface corresponding to the first mating surface of the first crankshaft section. These two first mating surfaces may be arranged adjacent to each other in the connected state, for example, abutting each other in the same axial region of the crankshaft. The two first mating surfaces may, for example, form a loose fit, a transition fit, or an interference fit. The fit in the region of the first mating surfaces may be tighter than in the region of the teeth.For example, the first mating surface of the first crank arm section can be formed by a cylindrical section in the cutting direction in front of the cutting teeth. This first mating surface can ensure concentricity between the two crank arm sections during insertion before the cutting process of the tooth profile begins. The first mating surface can be separated from the cutting teeth, for example, by a circumferential groove. This prevents the mating surface from interfering with the cutting process.

[0024] In a further embodiment of the crankshaft system, the first crankshaft section may have a second mating surface behind the cutting teeth in the cutting direction. This second mating surface can also withstand bending loads. The second crankshaft section may have a second mating surface corresponding to the second mating surface of the first crankshaft section. These two second mating surfaces may be arranged adjacent to each other in the connected state, for example, abutting each other in the same axial region of the crankshaft. The two second mating surfaces may, for example, form a loose fit, a transition fit, or an interference fit. The fit in the region of the second mating surfaces may be tighter than in the region of the teeth. For example, the second mating surface of the first crankshaft section may be formed by a cylindrical section behind the cutting teeth in the cutting direction.The second mating surface can also be located on another crankset component or drivetrain component, for example, to support bending forces. For instance, the second mating surface can be located on a bottom bracket. The second mating surface of the first crankset component can be separated from the cutting teeth, for example, by a circumferential groove. This can simplify manufacturing.

[0025] In another embodiment of the crankset system, a section of the cutting teeth can have a constant cross-section. This reduces the cost of manufacturing the cutting teeth. Furthermore, it allows for a continuous, uniform tooth profile between the two crankset components. For example, the cutting teeth can have a constant height and width after the cutting edge. The cross-section can change only at the respective axial ends of the cutting teeth, for instance, to transition into the mating surfaces and, alternatively or additionally, to form the cutting edge.

[0026] In a further embodiment of the crankset system, the system may include a sleeve that can be slid onto an end section of one of the crankset sections before the two sections are joined. This end section faces the other crankset section during the joining process. After the two crankset sections are joined, the sleeve can be fixed to the crankset. However, after joining, the sleeve can be permanently fixed. For example, the ends of the crankset sections facing away from each other when joined can have a diameter larger than the inner diameter of the sleeve. This allows the sleeve to be easily installed and secured to the crankset by connecting the two crankset sections. The sleeve can, for example, be made of plastic.The sleeve can, for example, be designed as a signal-carrying component. The sleeve is, for instance, made in one piece to ensure unimpeded signal transmission. Furthermore, this allows the sleeve to have a small diameter, enabling a compact bicycle drivetrain. Despite this compact design, the sleeve can still be installed on the two-piece crank axle.

[0027] A second aspect concerns a pedal crank shaft comprising a first pedal crank shaft part and a second pedal crank shaft part. The pedal crank shaft can be formed from the pedal crank shaft 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.

[0028] The first part of the crankshaft has a cutting tooth profile, and the second part has a corresponding tooth profile. The tooth profile was cut by the cutting teeth when the first and second parts of the crankshaft were inserted into each other.

[0029] In a further embodiment of the crank arm, the crank arm may have a first end section with a first diameter, an opposing end section with a second diameter, a central section with a third diameter, and a sleeve. The sleeve may be located in the central section. The sleeve may have a central through-hole. The third diameter may be smaller than the first and second diameters. The inner diameter of the sleeve may be smaller than the first and second diameters. The inner diameter of the sleeve may correspond to or be larger than the third diameter. The sleeve may abut one or both parts of the crank arm. The sleeve may be fixed, for example, by a dowel pin, adhesive bond, screw connection, or press fit.

[0030] Another aspect concerns a bicycle drivetrain that has the crank axle according to the second aspect. Yet another aspect concerns a bicycle with the crank axle according to the second aspect or the aforementioned drivetrain. Further features, embodiments, and advantages are described in the second and first aspects. Conversely, features, embodiments, and advantages of the second and first aspects also represent features, embodiments, and advantages of the further aspects. Fig. Figure 1 shows a schematic sectional view of a pedal crank shaft with a first pedal crank shaft part and a second pedal crank shaft part.

[0031] Fig. Figure 1 shows a schematic sectional view of a pedal crankshaft with a first pedal crankshaft part 20 and a second pedal crankshaft part 22. The second pedal crankshaft part 22 has a cylindrical recess 24 into which the first pedal crankshaft part 20 has been inserted with a cylindrical end section. Thus, the pedal crankshaft is formed from a pedal crankshaft system with the two pedal crankshaft parts 20 and 22.

[0032] The first crank arm section 20 has a cutting tooth profile 26 on its outer circumference in an axial section, formed by radially outer teeth 28. To connect the two crank arm sections 20, 22, the first crank arm section 20 is inserted along its axial extent in an insertion direction, and thus cutting direction, towards the bottom of the recess 24 in the second crank arm section 22. The bottom of the recess forms a stop for the first crank arm section 20, thereby defining an assembly position. The cutting direction is in Fig.Figure 1 is illustrated by arrow 34. At a leading end of the cutting teeth 26 in this cutting direction, each of the teeth 28 of the first crank arm section 20 has a cutting area 30. This cutting area 30 engages a tooth profile 32 corresponding to the cutting area of ​​the cutting teeth 26 in the recess 24 of the inner circumference of the second crank arm section 22. 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 crank arm section 22 have a constant height and a constant width.

[0033] The second crank arm section 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 crank arm section 20 to the second crank arm section 22 in the cutting direction, and thus axially. The screw 38 engages with an internal thread in a through-opening 42 of the first crank arm section 20. By tightening the screw 38, the first crank arm section 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 crank arm section 20 into the second crank arm section 22, the tooth profile 32 is also cut into the second crank arm section 22. Alternatively, the pressing in can be carried out using a press without using the screw 38.

[0034] The first crank arm section 20 has a first 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 first mating surface on its outer circumference. The first mating surface guides the first crank arm section 20 and the second crank arm section 22 together during insertion and ensures concentricity of the two elements 20, 22 before the tooth profile 32 begins to cut. Furthermore, in the connected state shown, the first mating surface rests against a corresponding mating surface of the second crank arm section 22. The first mating surfaces can thus withstand bending loads.

[0035] The first mating surface and the end piece 44 are axially separated from the cutting teeth 26 by a circumferential groove 46 in the first pedal crank shaft part 20.

[0036] The first crank arm section 20 has a second cylindrical end piece 50 at its end facing away from the bottom of the recess 24 and thus behind the cutting teeth 26 and the cutting area 30 in the cutting direction. This end piece forms a second mating surface on its outer circumference. This second mating surface rests against a bottom bracket in a section not shown and also absorbs bending loads. Reference sign 20 first pedal crank shaft part 22 second pedal crank shaft part 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 42. Passage opening of the first element 44 End piece / first fitting surface 46 Nut 50 End piece / second fitting surface

Claims

[1] Pedal crank system comprising a first pedal crank part (20) and a second pedal crank part (22), wherein the first pedal crank part (20) and the second pedal crank part (22) are insertable into each other for connection to form a pedal crank for a bicycle, wherein the first element (20) has a cutting tooth (26) which, when inserted, cuts a corresponding tooth profile (32) into the second element (22) in a cutting direction (34). [2] Pedal crank system according to claim 1, characterized by , that the cutting teeth (26) and the tooth profile (32) form a press fit after connecting the first pedal crank shaft part (20) with the second pedal crank shaft part (22). [3] Pedal crank system according to claim 1, characterized by, that the cutting teeth (26) and the tooth profile (32) form a transition fit after connecting the first pedal crank shaft part (20) with the second pedal crank shaft part (22). [4] Pedal crank system according to claim 1, characterized by , that the cutting teeth (26) and the tooth profile (32) form a loose fit after connecting the first pedal crank shaft part (20) with the second pedal crank shaft part (22). [5] Pedal crank system according to one of the preceding claims, characterized by , that the pedal crank system has a fixing element (38), wherein the pedal crank system is designed to fix the first pedal crank part (20) to the second pedal crank part (22) in the cutting direction (34) by means of the fixing element (38). [6] Pedal crank system according to one of the preceding claims, characterized by, that the second pedal crank shaft part (22) has a recess (24) for the insertion of the first pedal crank shaft part (20) and the cutting teeth (26) are formed on an outer circumference of the first pedal crank shaft part (20). [7] Pedal crank system according to any one of claims 1 to 5, characterized by , that the first pedal crank shaft part (20) has a recess (24) for the insertion of the second pedal crank shaft part (22) and the cutting teeth (26) are formed on an inner circumference of the recess (24) of the first pedal crank shaft part (20). [8] Pedal crank system according to one of the preceding claims, characterized by , that the first pedal crank shaft part (20) and the second pedal crank shaft part (22) are designed to strike each other when joined together in the cutting direction (34). [9] Pedal crank system according to one of the preceding claims, characterized by, that the first element (20) in the cutting direction (34) has a first mating surface (44) in front of the cutting teeth (26). [10] Pedal crank system according to one of the preceding claims, characterized by , that the first element (20) has a second mating surface (50) behind the cutting tooth (26) in the cutting direction (34). [11] Pedal crank system according to one of the preceding claims, characterized by , that a toothed area of ​​the cutting tooth (26) has a constant cross-section. [12] Pedal crank system according to one of the preceding claims, characterized by, that the pedal crank system has a sleeve which, before connecting the two pedal crank parts (20, 22), can be slid onto an end area of ​​one of the two pedal crank parts (20, 22), which faces the other of the two pedal crank parts (20, 22) during connection, and is thus attached to the pedal crank after connecting the two pedal crank parts (20, 22). [13] Pedal crank shaft with a first pedal crank shaft part (20) and a second pedal crank shaft part (22) which are inserted into one another, wherein the first pedal crank shaft part (20) has a cutting tooth (26) and the second pedal crank shaft part (22) has a corresponding tooth profile (32) which was cut by the cutting tooth (26) when the first pedal crank shaft part (20) and the second pedal crank shaft part (22) were inserted into one another. [14] Crankshaft according to claim 13, characterized by, that the pedal crank shaft has a first end region with a first diameter, an opposite end region with a second diameter, and a central region with a third diameter, as well as a sleeve which is arranged in the central region, wherein the third diameter is smaller than the first diameter and the second diameter, and an inner diameter of the sleeve is smaller than the first diameter and the second diameter.

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